全文获取类型
收费全文 | 567篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 37篇 |
地球物理 | 147篇 |
地质学 | 277篇 |
海洋学 | 46篇 |
天文学 | 57篇 |
综合类 | 3篇 |
自然地理 | 32篇 |
出版年
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 32篇 |
2012年 | 29篇 |
2011年 | 25篇 |
2010年 | 29篇 |
2009年 | 39篇 |
2008年 | 20篇 |
2007年 | 31篇 |
2006年 | 30篇 |
2005年 | 34篇 |
2004年 | 37篇 |
2003年 | 28篇 |
2002年 | 29篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有603条查询结果,搜索用时 531 毫秒
541.
Om Prakash Tripathi Sophie Godin-Beekmann Franck Lefèvre Marion Marchand Andrea Pazmiño Alain Hauchecorne Florence Goutail Hans Schlager C. Michael Volk B. Johnson G. König-Langlo Stefano Balestri Fred Stroh T. P. Bui H. J. Jost T. Deshler Peter von der Gathen 《Journal of Atmospheric Chemistry》2006,55(3):205-226
Simulations of polar ozone losses were performed using the three-dimensional high-resolution (1∘ × 1∘) chemical transport model MIMOSA-CHIM. Three Arctic winters 1999–2000, 2001–2002, 2002–2003 and three Antarctic winters 2001, 2002, and 2003 were considered for the study. The cumulative ozone loss in the Arctic winter 2002–2003 reached around 35% at 475 K inside the vortex, as compared to more than 60% in 1999–2000. During 1999–2000, denitrification induces a maximum of about 23% extra ozone loss at 475 K as compared to 17% in 2002–2003. Unlike these two colder Arctic winters, the 2001–2002 Arctic was warmer and did not experience much ozone loss. Sensitivity tests showed that the chosen resolution of 1∘ × 1∘ provides a better evaluation of ozone loss at the edge of the polar vortex in high solar zenith angle conditions. The simulation results for ozone, ClO, HNO3, N2O, and NO
y
for winters 1999–2000 and 2002–2003 were compared with measurements on board ER-2 and Geophysica aircraft respectively. Sensitivity tests showed that increasing heating rates calculated by the model by 50% and doubling the PSC (Polar Stratospheric Clouds) particle density (from 5 × 10−3 to 10−2 cm−3) refines the agreement with in situ ozone, N2O and NO
y
levels. In this configuration, simulated ClO levels are increased and are in better agreement with observations in January but are overestimated by about 20% in March. The use of the Burkholder et al. (1990) Cl2O2 absorption cross-sections slightly increases further ClO levels especially in high solar zenith angle conditions. Comparisons of the modelled ozone values with ozonesonde measurement in the Antarctic winter 2003 and with Polar Ozone and Aerosol Measurement III (POAM III) measurements in the Antarctic winters 2001 and 2002, shows that the simulations underestimate the ozone loss rate at the end of the ozone destruction period. A slightly better agreement is obtained with the use of Burkholder et al. (1990) Cl2O2 absorption cross-sections. 相似文献
542.
The coupling of optimal economic growth and climate dynamics 总被引:1,自引:0,他引:1
Olivier Bahn Laurent Drouet Neil R. Edwards Alain Haurie Reto Knutti Socrates Kypreos Thomas F. Stocker Jean-Philippe Vial 《Climatic change》2006,79(1-2):103-119
In this paper, we study optimal economic growth programs coupled with climate change dynamics. The study is based on models derived from MERGE, a well established integrated assessment model (IAM). We discuss first the introduction in MERGE of a set of “tolerable window” constraints which limit both the temperature change and the rate of temperature change. These constraints, obtained from ensemble simulations performed with the Bern 2.5-D climate model, allow us to identity a domain intended to preserve the Atlantic thermohaline circulation. Next, we report on experiments where a two-way coupling is realized between the economic module of MERGE and an intermediate complexity “3-D-” climate model (C-GOLDSTEIN) which computes the changes in climate and mean temperature. The coupling is achieved through the implementation of an advanced “oracle based optimization technique” which permits the integration of information coming from the climate model during the search for the optimal economic growth path. Both cost-effectiveness and cost-benefit analysis modes are explored with this combined “meta-model” which we refer to as GOLDMERGE. Some perspectives on future implementations of these approaches in the context of “collaborative” or “community” integrated assessment modules are derived from the comparison of the different approaches. 相似文献
543.
IR spectra of clay samples can be collected in transmission through oriented deposits onto glass slide and are similar to the IR spectra of the same samples obtained by traditional way (KBr pellets). As examples, it is shown that it is possible to differentiate dickite from kaolinite and smectites of various chemistries, as easily by both ways. It is thus possible to use oriented clay deposits onto glass slide for both XRD and IR studies and to easily take benefit of the complementarity of both techniques. To cite this article: S. Petit et al., C. R. Geoscience 335 (2003). 相似文献
544.
Reza Sheikholeslami Hervé Bellon Hachem Emami Mossaı̈eb Sabzehei Alain Piqué 《Comptes Rendus Geoscience》2003,335(13):981-991
The metamorphic rocks of the Neyriz area (Sanandaj–Sirjan zone) represent a Palaeozoic sequence, the upper part of which being palaeontologically dated from the Carboniferous and the Permian. Field structural analysis of the whole sequence, detailed in laboratory by microstructural one and 40K–40Ar dating carried on separated minerals, lead to establish that the whole sequence, from gneisses to Permian rocks, has suffered a unique synmetamorphic deformation, of variable intensity, marked by a foliation. Isotopic ages measured on extracted amphiboles and micas, clustered in four groups between 300 and 60 Ma, show the successive stages of their slow exhumation, which ended by the end of the Cretaceous. To cite this article: R. Sheikholeslami et al., C. R. Geoscience 335 (2003). 相似文献
545.
Characterization and correlation of Upper Jurassic (Oxfordian) bentonite deposits in the Paris Basin and the Subalpine Basin, France 总被引:1,自引:0,他引:1
Pierre Pellenard Jean-Francois Deconinck Warren D. Huff† Jacques Thierry‡ Didier Marchand‡ Dominique Fortwengler§ Alain Trouiller¶ 《Sedimentology》2003,50(6):1035-1060
Abstract Explosive volcanic activity is recorded in the Upper Jurassic of the Paris Basin and the Subalpine Basin of France by the identification of five bentonite horizons. These layers occur in Lower Oxfordian (cordatum ammonite zone) to Middle Oxfordian (plicatilis zone) clays and silty clays deposited in outer platform environments. In the Paris Basin, a thick bentonite (10–15 cm), identified in boreholes and in outcrop, is dominated by dioctahedral smectite (95%) with trace amounts of kaolinite, illite and chlorite. In contrast, five bentonites identified in the Subalpine Basin, where burial diagenesis and fluid circulation were more important, are composed of a mixture of kaolinite and regular or random illite/smectite mixed-layer clays in variable proportions, indicating a K-bentonite. In the Subalpine Basin, a 2–15 cm thick bentonite underlain by a layer affected by sulphate–carbonate mineralization can be correlated over 2000 km2. Euhedral zircon, apatite and biotite crystals have been identified in all the bentonites. The geochemical composition of the bentonites in both basins is characterized by high concentrations of Hf, Nb, Pb, Ta, Th, Ti, U, Y, Zr and low concentrations of Cr, Cs and Rb. Biostratigraphical and geochemical data suggest that the thick bentonite in the Paris Basin correlates with the thickest bentonite in the Subalpine Basin, located 400 km to the south. These horizons indicate that significant explosive volcanic events occurred during the Middle Oxfordian and provide potential long-distance isochronous marker beds. Immobile element discrimination diagrams and rare-earth element characteristics indicate that the original ash compositions of the thickest bentonites correspond to a trachyandesitic source from a within-plate alkaline series that was probably related to North Atlantic rifting. 相似文献
546.
Intercomparison of Boron Isotope and Concentration Measurements. Part II: Evaluation of Results 总被引:3,自引:1,他引:3
Roberto Gonfiantini Sonia Tonarini Manfred Grning Alessandra Adorni‐Braccesi Assad S. Al‐Ammar Marcus Astner Sebastien Bchler Ramon M. Barnes Randy L. Bassett Alain Cocherie Annette Deyhle Andrea Dini Giorgio Ferrara Jrme Gaillardet Judith Grimm Catherine Guerrot Urs Krhenbühl Graham Layne Damien Lemarchand Anette Meixner D. Jack Northington Maddalena Pennisi Eva Reitznerov Ilia Rodushkin Naoji Sugiura Regina Surberg Sabine Tonn Michael Wiedenbeck Samuel Wunderli Yingkai Xiao Thomas Zack 《Geostandards and Geoanalytical Research》2003,27(1):41-57
The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ11 B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution. 相似文献
547.
The Hasan Dagi stratovolcano (Central Anatolia, Turkey): evolution from calc-alkaline to alkaline magmatism in a collision zone 总被引:1,自引:0,他引:1
Catherine Deniel Erkan Aydar Alain Gourgaud 《Journal of Volcanology and Geothermal Research》1998,87(1-4)
The Hasan Dagi volcano is one of the two large Plio-Quaternary volcanoes in Cappadocia (Central Anatolia, Turkey). Three stages of edifice construction have been identified for this volcano: Paleovolcano, Mesovolcano and Neovolcano. Most samples from Hasan Dagi volcano are calc-alkaline and define an almost complete trend from basaltic andesite to rhyolite. However, the more recent (Neovolcano) mafic samples are alkaline basalts. The mineralogical and geochemical characteristics of the oldest lavas (Keçikalesi (13 Ma) and Paleo-Hasan Dagi (7 Ma)) are significantly different from those of the younger lavas (Meso- and Neo-Hasan Dagi (<1 Ma)). Calcic plagioclase and pigeonite are typically observed in these older lavas. The Paleovolcano basalts are depleted in alkalis and display a tholeiitic tendency whereas the differentiated lavas are depleted in Na2O but enriched in K2O compared to younger lavas. There is an evolution through time towards higher TiO2, Fe2O3*, MgO, Na2O and K2O and lower Al2O3 and SiO2 which is reflected in the basalt compositions. All the basalts display multi-element patterns typical of continental margin magmas with a significant enrichment in LILE (K, Rb, Ba and Th) and LREE and strong (Paleovolcano) to moderate (Meso- and Neovolcano) negative Nb, Zr and Ti anomalies. However, the younger basalts are the most enriched in incompatible elements, in agreement with their alkaline affinities and do not systematically display negative HFSE anomalies. REE data suggest an hydrous amphibole-bearing crystallization history for both Meso- and Neovolcano lavas. The distinction between the older and younger lavas is also apparent in trace element ratios such as Nb/Y, Ti/Y and Th/Y. These ratios indicate the role of a subducted component±crustal contamination in the genesis of the Hasan Dagi lavas, particularly for the oldest lavas (Keçikalesi and Paleo-Hasan Dagi). The decreasing influence of this component through time, over the last 6–7 m.y., has been accompanied by an increasing contribution of melt-enriched lithosphere. Although the range of variation of Sr, Nd and Pb isotopic ratios is small (0.70457–0.70515; 0.51262–0.51273; 18.80–18.94; 15.64–15.69; 38.87–39.10), it also reflects the evolution of the magma sources through time. Indeed, the youngest (Neovolcano) and most primitive basalts display significantly lower 87Sr/86Sr than the Paleo- and Mesovolcano basalts, whereas the Mesovolcano basalts display more radiogenic Pb than Paleovolcano samples. Magma mixing processes between initially heterogeneous and/or variably contaminated magmas may account for the genesis of the less differentiated and intermediate lavas (48–57% SiO2). Meso- and Neovolcano differentiated lavas (60–68% SiO2) are either derived from the analyzed basalts or from more primitive and more depleted magmas by fractional crystallization±some crustal contamination (AFC). Furthermore, the highly differentiated samples (72–75% SiO2) are not strongly contaminated. The strong calc-alkaline character of Hasan Dagi lavas, in the absence of contemporaneous subduction, must reflect the heritage of the early subduction of the Afro–Arabian plate under the Eurasian plate. The evolution towards alkaline compositions through time is clearly related to the development of extensional tectonics in Central Anatolia in the Late Miocene. 相似文献
548.
EDTA and ATMP are synthetic chelatingagents used in many industrial applications. Becauseof their low biodegradability, they are present inmany aquatic systems where their strong complexingcapacities can modify the transfer of toxic heavymetals between solid and liquid phases.The remobilization of Cu, Pb and Cd from pollutedsuperficial river sediments in the presence of twosynthetic organic ligands (a polycarboxylate, EDTA,and a phosphonate, ATMP) is investigated as a functionof reaction time to determine the time necessary toreach dissolutive equilibrium, and as a fonction ofthe complexing agent concentration.The dissolutive equilibrium times are similar (10 to20 hours) and the solubilizing power of ATMP isslightly lower than that of EDTA. The curves ofsolubilization of metals in the presence of thecomplexing agents present a shape of a chelateconcentration desorption edge, for a chelate rangebetween 10-5 to 10-3 mol L-1, thesolubilised metals increasing dramatically. Thisremobilization is the result of a competition betweenassociation with the solid phase and dissolvedcomplexation. With EDTA, the desorption order ofmetals seems to be imposed by association with thesolid. For ATMP is it the chelate complexing strengthwhich determines this order. 相似文献
549.
Pierre Delmelle Minoru Kusakabe Alain Bernard Tobias Fischer Simon de Brouwer Esfeca del Mundo 《Bulletin of Volcanology》1998,59(8):562-576
The hydrologic structure of Taal Volcano has favored development of an extensive hydrothermal system whose prominent feature
is the acidic Main Crater Lake (pH<3) lying in the center of an active vent complex, which is surrounded by a slightly alkaline
caldera lake (Lake Taal). This peculiar situation makes Taal prone to frequent, and sometimes catastrophic, hydrovolcanic
eruptions. Fumaroles, hot springs, and lake waters were sampled in 1991, 1992, and 1995 in order to develop a geochemical
model for the hydrothermal system. The low-temperature fumarole compositions indicate strong interaction of magmatic vapors
with the hydrothermal system under relatively oxidizing conditions. The thermal waters consist of highly, moderately, and
weakly mineralized solutions, but none of them corresponds to either water–rock equilibrium or rock dissolution. The concentrated
discharges have high Na contents (>3500 mg/kg) and low SO4/Cl ratios (<0.3). The Br/Cl ratio of most samples suggests incorporation of seawater into the hydrothermal system. Water
and dissolved sulfate isotopic compositions reveal that the Main Crater Lake and spring discharges are derived from a deep
parent fluid (T≈300 °C), which is a mixture of seawater, volcanic water, and Lake Taal water. The volcanic end member is
probably produced in the magmatic-hydrothermal environment during absorption of high-temperature gases into groundwater. Boiling
and mixing of the parent water give rise to the range of chemical and isotopic characteristics observed in the thermal discharges.
Incursion of seawater from the coastal region to the central part of the volcano is supported by the low water levels of the
lakes and by the fact that Lake Taal was directly connected to the China sea until the sixteenth century. The depth to the
seawater-meteoric water interface is calculated to be 80 and 160 m for the Main Crater Lake and Lake Taal, respectively. Additional
data are required to infer the hydrologic structure of Taal. Geochemical surveillance of the Main Crater Lake using the SO4/Cl, Na/K, or Mg/Cl ratio cannot be applied straightforwardly due to the presence of seawater in the hydrothermal system.
Received: 12 February 1997 / Accepted: 26 January 1998 相似文献
550.
Alain Plouffe 《Environmental Geology》1998,33(2-3):183-196
Abundant cinnabar (HgS) mineralization is associated with the Pinchi Fault in central British Columbia. Two formerly producing
mercury mines have been developed on this fault: Pinchi and Bralorne Takla. The mercury content of till (a sediment type directly
deposited by glaciers) in the area of this fault is primarily controlled by the occurrence of cinnabar mineralization in bedrock
and the direction of ice flow. Cinnabar-bearing bedrock was eroded by glaciers, transported in the direction of ice flow,
and deposited "down-ice" from its source. An example of such a dispersal train is documented for the Pinchi Mine area where
mercury ore was transported over a distance of 12 km, as measured in the clay-sized fraction (< 0.002 mm) of till, and could
have been transported over 24 km according to heavy mineral concentrates (specific gravity >3.3) of this same sediment. Antimony,
chromium, and nickel dispersal trains were also detected in the region. These data indicate that natural glacial processes
can result in the "mobilization" of metals in the surficial environment, a factor which has to be considered at mine sites
in glaciated terrain, where mine reclamation and remediation measures are now required.
Received: 31 October 1996 · Accepted: 27 May 1997 相似文献