全文获取类型
收费全文 | 648篇 |
免费 | 27篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 47篇 |
地球物理 | 136篇 |
地质学 | 319篇 |
海洋学 | 49篇 |
天文学 | 76篇 |
自然地理 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 26篇 |
2017年 | 14篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 40篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 45篇 |
2009年 | 59篇 |
2008年 | 48篇 |
2007年 | 26篇 |
2006年 | 30篇 |
2005年 | 31篇 |
2004年 | 33篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1979年 | 2篇 |
排序方式: 共有679条查询结果,搜索用时 31 毫秒
671.
Dehydration of dioctahedral aluminous phyllosilicates: thermodynamic modelling and implications for thermobarometric estimates 总被引:1,自引:1,他引:0
Benoît Dubacq Olivier Vidal Vincent De Andrade 《Contributions to Mineralogy and Petrology》2010,159(2):159-174
We propose a solid-solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations,
including hydration, observed in natural smectites, interlayered illite/smectite, illites, and phengites from diagenetic to
high-grade metamorphic conditions. The suggested formalism involves dehydrated micas and hydrated pyrophyllite-like thermodynamic
end-members. With these end-members, the equilibrium conditions of quartz + water + K-bearing mica-like phyllosilicates of
fixed 2:1 composition are represented by a line in P–T space along which the interlayer water content varies. The relevant thermodynamic properties required for the calculation
of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions,
which covers a range between 25°C and few MPa to 800°C and 5 GPa. The temperatures calculated at fixed pressure with our model
are in fair agreement with those reported in the literature for the 250 natural data. At low temperature and pressure, the
amount of interlayer water in K-deficient phengite and illite is predicted to reach 100% of the apparent vacancies, which
is consistent with previous values reported in the literature. Although the amount of interlayer water is predicted to decrease
with pressure and temperature, it is calculated to be significant in K-deficient phengite from LT–HP pelites metamorphosed
at about 350°C, 10 kbar. The presence of molecular water in the interlayer site of such phengites has been confirmed by FTIR
mapping. Its implications for P–T estimates are discussed. 相似文献
672.
Hydraulic conductivity distribution in crystalline rocks, derived from inflows to tunnels and galleries in the Central Alps, Switzerland 总被引:4,自引:3,他引:1
Inflow data from 23 tunnels and galleries, 136 km in length and located in the Aar and Gotthard massifs of the Swiss Alps, have been analyzed with the objective (1) to understand the 3-dimensional spatial distribution of groundwater flow in crystalline basement rocks, (2) to assess the dependency of tunnel inflow rate on depth, tectonic overprint, and lithology, and (3) to derive the distribution of fracture transmissivity and effective hydraulic conductivity at the 100-m scale. Brittle tectonic overprint is shown to be the principal parameter regulating inflow rate and dominates over depth and lithology. The highest early time inflow rate is 1,300 l/s and has been reported from a shallow hydropower gallery intersecting a 200-m wide cataclastic fault zone. The derived lognormal transmissivity distribution is based on 1,361 tunnel intervals with a length of 100 m. Such interval transmissivities range between 10?9 and 10?1 m2/s within the first 200–400 m of depth and between 10?9 and 10?4 m2/s in the depth interval of 400–1,500 m below ground surface. Outside brittle fault zones, a trend of decreasing transmissivity/hydraulic conductivity with increasing depth is observed for some schistous and gneissic geological units, whereas no trend is identified for the granitic units. 相似文献
673.
Nicolas Estrade Jean Carignan Jeroen E. Sonke Olivier F.X. Donard 《Geostandards and Geoanalytical Research》2010,34(1):79-93
With the emergence of new analytical techniques and the expansion of scientific fields explored by using mercury isotopes, the community needs reference materials (RM) to validate and assure the accuracy of the results. The present work investigates (1) the characterisation of secondary RM in order to validate analytical systems, (2) the effects of two complex matrices on isotopic determination using stannous chloride cold vapour generation coupled to MC-ICP-MS (CV-MC-ICP-MS), (3) the effects of multiple digestion techniques for total Hg extraction and (4) the characterisation of nine geo-bio-environmental RM. Two secondary mono-elemental RMs analysed using two different analytical setups yielded isotopic compositions on δ202Hg of −3.54 ± 0.27‰ (CRPG-F65A, 2SD, n = 38) and +2.59 ± 0.19‰ (CRPG-RL24H, 2SD, n = 30) relative to the CRM NIST SRM 3133. These two RMs cover the whole range of Hg isotopic fractionation in natural samples and are made available to the scientific community. Complex fly ash and hydroxysulfate green rust matrices were synthesised, spiked with NIST SRM 3133, then digested and finally analysed versus the mono-elemental NIST SRM 3133 to show potential effect of these complex matrices during CV-MC-ICP-MS. Three digestions techniques, including traditional acid digestion, microwave digestion and high pressure-high temperature digestion, were applied to the lichen RM BCR-482 in order to compare advantages and drawbacks of these methods. Finally, the isotopic compositions of nine RMs including soils (NIST SRM 2711; GXR-2; GSS-4), sediment (GSD-10), jasperoid (GXR-1), ore deposit (GXR-3), fly ashes (BCR-176; BCR-176R) and lichen (BCR-482) are reported. These selected materials have δ202Hg values ranging from −1.75‰ to +0.11‰. Some RMs also presented mass-independent fractionation with Δ199Hg and Δ201Hg of up to −0.6‰. 相似文献
674.
In this paper, we applied a reliable technique for measuring Fe isotope variations in coastal seawater at nanomolar levels. Iron was directly pre-concentrated from acidified seawater samples onto a nitrilotriacetic acid chelating resin and further purified using anion-exchange resin. Sample recovery, determined using a standard addition method, was essentially quantitative. Iron was then determined using a high-resolution multicollector ICP-MS (Neptune) coupled to an ApexQ desolvation introduction system. The external precision for δ56Fe values was 0.11‰ (2s) when using total a Fe quantity between 25 and 100 ng. We initially applied this technique to measure the Fe isotope composition of dissolved Fe from several coastal environments in the north-eastern United States and we observed a range of δ56Fe values between -0.9‰ and 0.1‰ relative to the IRMM-14 reference material. Iron isotope compositions of several reference water materials for inter-laboratory comparisons were also reported. Our results suggest that iron in coastal seawater, derived from benthic diagenesis and/or groundwater has negative Fe isotopic signatures that are distinct from other iron sources such as atmospheric deposition and rivers. 相似文献
675.
Natural variations of Se isotopic composition determined by hydride generation multiple collector inductively coupled plasma mass spectrometry 总被引:1,自引:0,他引:1
Olivier Rouxel John LuddenJean Carignan Luc MarinYves Fouquet 《Geochimica et cosmochimica acta》2002,66(18):3191-3199
Multiple-collector inductively coupled plasma mass spectrometry has been used for the precise measurement of the isotopic composition of Se in geological samples. Se is chemically purified before analysis by using cotton impregnated with thioglycollic acid. This preconcentration step is required for the removal of matrix-interfering elements for hydride generation, such as transitional metals, and also for the quantitative separation of other hydride-forming elements, such as Ge, Sb, and As. The analyte is introduced in the plasma torch with a continuous-flow hydride generation system. Instrumental mass fractionation is corrected with a “standard-sample bracketing” approach. By use of this new technique, the minimum Se required per analysis is lowered to 10 ng, which is one order of magnitude less than the amount needed for the N-TIMS technique. The estimated external precision calculated for the 82Se/76Se isotope ratio is 0.25‰ (2σ), and the data are reported as delta notation (‰) relative to our internal standard (MERCK elemental standard solution). Measurements of Se isotopes are presented for samples of standard solutions and geological reference materials, such as silicate rocks, soils, and sediments. The Se isotopic composition of selected terrestrial and extraterrestrial materials are also presented. An overall Se isotope variation of 8‰ has been observed, suggesting that Se isotopes fractionate readily and are extremely useful tracers of natural processes. 相似文献
676.
Frédéric Hourdin Marie-Alice Foujols Francis Codron Virginie Guemas Jean-Louis Dufresne Sandrine Bony Sébastien Denvil Lionel Guez François Lott Josefine Ghattas Pascale Braconnot Olivier Marti Yann Meurdesoif Laurent Bopp 《Climate Dynamics》2013,40(9-10):2167-2192
The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged. 相似文献
677.
Grard Brogniez Frdric Parol Laurianne Bcu Jacques Pelon Olivier Jourdan Jean-Franois Gayet Frdrique Auriol Christian Verwaerde Jean-Yves Balois Bahaiddin Damiri 《Atmospheric Research》2004,72(1-4):425
In the context of the next AQUA Train satellite experiment, airborne measurements were carried out to simulate satellite measurements. They were conducted between September 25 and October 12, 2001, off the coast of southern France over the Atlantic Ocean and over the Mediterranean Sea, respectively. During the intensive Field Radiation Experiment on Natural Cirrus and High-level clouds (FRENCH/DIRAC 2001), natural ice clouds were sampled from in situ and remote sensing measurements. On October 5 and 7, 2001, cirrus cloud decks were described by a complete data set acquired by: (i) in situ microphysical instruments onboard the TBM-700 aircraft: PMS probe, and Polar Nephelometer (ii) and downward-looking radiative instruments onboard the Mystère 20 aircraft: an infrared radiometer, a lidar, a visible imager with polarisation capabilities, and a middle infrared radiometer. Moreover, classical thermodynamical measurements were carried out onboard the Mystère 20. Mean microphysical characteristics of cirrus deck are derived from interpretation of remote sensing measurements. These properties are compared with those derived from in situ microphysical measurements in order to evaluate the radiative impact of natural cirrus clouds. 相似文献
678.
Cobalt-bearing pyrite (0.5?C2.0?wt.% Co) is abnormally abundant (up to 35?vol.% of the total volume of the sulfide phase) in some eastern Pyrenean peridotite massifs, compared to pieces of subcontinental mantle studied so far for sulfides. Pyrite occurs as vermicular intergrowths inside pentlandite and/or chalcopyrite or as coarser, blocky grains in the intergranular pores of host peridotites. Those different pyrites are characterized by different platinum-group element systematics (measured by laser ablation microprobe and ICP-MS). Vermicular pyrite intergrown with pentlandite displays Os-, Ir-, Ru- and Rh-enriched chondrite normalized PGE patterns of Monosulfide solid solution (Mss). In contrast, coarse-grained intergranular (??blocky??) pyrites, are PGE-poor. Chalcophile trace elements (i.e. Zn, Pb, Ag, Au) that are not usually concentrated in mantle-derived sulfides were commonly detected. By contrast, selenium contents are generally low, yielding thus pyrite with high S/Se ratio (>105), consistent with a sedimentary sulfur source. Pyrite microtextures and chalcophile trace element contents support a process of assimilation of crustal sulfur from the metamorphosed sedimentary country rocks. These latter generated highly reactive CO2-S fluids, which were injected into structural discontinuities of the lherzolitic bodies. Sulfur has reacted at T?=?300?C550°C with pre-existing, mantle-derived, metal-rich sulfide assemblages (pentlandite-chalcopyrite). Addition of crustal sulfur did produce Mss which, on cooling, exsolved the Os-rich pyrite in addition to pentlandite. The coarse-grained pyrite types have crystallized directly from S-rich fluids. 相似文献
679.
Djim M. L. Diongue Christine Stumpp Olivier Roupsard Didier Orange Frederic C. Do Serigne Faye 《水文研究》2023,37(1):e14787
Sustainable water management in semi-arid agriculture practices requires quantitative knowledge of water fluxes within the soil-vegetation-atmosphere system. Therefore, we used stable-isotope approaches to evaluate evaporation (Ea), transpiration (Ta), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre-monsoon, monsoon, and post-monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifying Ea); (ii) water and isotope mass balances (to partition Ea and Ta for groundnut and pasture); and (iii) the piston displacement method (for estimating R). Ea losses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02 to 0.09 mm d−1 in the Groundnut basin, versus 0.02–0.11 mm d−1 in Ferlo. At the groundnut site, Ea rates ranged from 0.01 to 0.69 mm d−1; Ta was in the range 0.55–2.29 mm d−1; and the Ta/ETa ratio was 74%–90%. At the pasture site, the ranges were 0.02–0.39 mm d−1 for Ea; 0.9–1.69 mm d−1 for Ta; and 62–90% for Ta/ETa. The ETa value derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from the previous validated HYDRUS-1D model. However, the HYDRUS-1D model gave a lower Ta/ETa ratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways. 相似文献