全文获取类型
收费全文 | 360篇 |
免费 | 1篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 16篇 |
地球物理 | 50篇 |
地质学 | 170篇 |
海洋学 | 38篇 |
天文学 | 68篇 |
综合类 | 1篇 |
自然地理 | 19篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 32篇 |
2012年 | 11篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 25篇 |
2008年 | 26篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 27篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有366条查询结果,搜索用时 15 毫秒
301.
Anders Meibom Jean-Pierre Cuif Smail Mostefaoui Karin L. Meibom 《Geochimica et cosmochimica acta》2008,72(6):1555-1569
Distributions of Mg and Sr in the skeletons of a deep-sea coral (Caryophyllia ambrosia) and a shallow-water, reef-building coral (Pavona clavus) have been obtained with a spatial resolution of 150 nm, using the NanoSIMS ion microprobe at the Muséum National d’Histoire Naturelle in Paris. These trace element analyses focus on the two primary ultra-structural components in the skeleton: centers of calcification (COC) and fibrous aragonite. In fibrous aragonite, the trace element variations are typically on the order of 10% or more, on length scales on the order of 1-10 μm. Sr/Ca and Mg/Ca variations are not correlated. However, Mg/Ca variations in Pavona are strongly correlated with the layered organization of the skeleton.These data allow for a direct comparison of trace element variations in zooxanthellate and non-zooxanthellate corals. In both corals, all trace elements show variations far beyond what can be attributed to variations in the marine environment. Furthermore, the observed trace element variations in the fibrous (bulk) part of the skeletons are not related to the activity of zooxanthellae, but result from other biological activity in the coral organism. To a large degree, this biological forcing is independent of the ambient marine environment, which is essentially constant on the growth timescales considered here.Finally, we discuss the possible detection of a new high-Mg calcium carbonate phase, which appears to be present in both deep-sea and reef-building corals and is neither aragonite nor calcite. 相似文献
302.
Evangelos Moulas Dimitrios Kostopoulos James A. D. Connolly Jean-Pierre Burg 《Petrology》2013,21(5):507-521
Sapphirine-bearing symplectites that replace kyanite in eclogites from the Greek Rhodope Massif have previously been attributed to a high-pressure granulite-facies metamorphic event that overprinted the eclogitic peak metamorphic assemblage. The eclogitic mineralogy consisted of garnet, omphacitic pyroxene, rutile and kyanite and is largely replaced by low-pressure minerals. Omphacite was initially replaced by symplectites of diopside and plagioclase that were subsequently replaced by symplectites of amphibole and plagioclase. Garnet reacted during decompression to form a corona of plagioclase, amphibole and magnetite. Rutile was partly transformed to ilmenite and kyanite decomposed to produce a high-variance mineral assemblage of symplectitic spinel, sapphirine, plagioclase and corundum. The presence of quartz and corundum in the kyanite eclogites is evidence for the absence of bulk equilibrium and obviates a conventional analysis of phase equilibria based on the bulk-rock composition. To circumvent this difficulty we systematically explored the pressure-temperature-composition (P-T-X) space of a thermodynamic model for the symplectites in order to establish the pressure-temperature (P-T) conditions at which the symplectites were formed after kyanite. This analysis combined with conventional thermometry indicates that the symplectites were formed at amphibolite-facies conditions. The resulting upper-pressure limit (~0.7 GPa) of the sapphirine-producing metamorphic overprint is roughly half the former estimate for the lower pressure limit of the symplectite forming metamorphic event. Temperature was constrained (T ~ 720°C) using garnet-amphibole mineral thermometry. The P-T conditions inferred here are consistent with thermobarometry from other lithologies in the Rhodope Massif, which show no evidence of granulite-facies metamorphism. Regional geological arguments and ion-probe (SHRIMP) zircon dating place the post-eclogite-facies metamorphic evolution in Eocene times. 相似文献
303.
Jean-Pierre Masse 《Geodinamica Acta》2013,26(4-5):263-271
Résumé— A l’aide des données disponibles sur la stratigraphie et la localisation des formations carbonatées de plates-formes du Crétacé inférieur périatlantique et caraïbe, il est possible de préciser l’état actuel des connaissances sur la distribution des dispositifs sédimentaires correspondants, à l’Aptien inférieur. Les schémas paléobiogéographiques proposés pour les organismes inféodés à ces plates-formes, confrontés à leur distribution, se heurtent à des difficultés d’ordre paléogéographique et paléocéanographique mais s’accordent généralement assez bien avec les hypothèses paléotectoniques. Les problèmes paléogéographiques se posent dans l’interprétation de la dispersion biologique par les marges. Les problèmes paléocéanographiques qui concernent essentiellement les schémas de paléocirculation hydrologique et leurs implications climatiques, se posent dans l’interprétation de la dispersion biologique transatlantique. Des éléments de solution à ces différents problèmes pourraient être apportés par de nouvelles recherches. 相似文献
304.
305.
David L. Jauncey Lucyna Kedziora-Chudczer James E.J. Lovell Jean-Pierre Macquart George D. Nicolson Rick A. Perley John E. Reynolds Anastasios K. Tzioumis Mark H. Wieringa Hayley E. Bignall 《Astrophysics and Space Science》2001,278(1-2):87-92
Intra-day variability (IDV) of active galactic nuclei (AGN) has been detected from gamma-ray energies to radio wavelengths.
At high energies, such variability appears to be intrinsic to the sources themselves. However, at radio wavelengths, brightness
temperatures as high as1018 to 1021 K are encountered if the IDV is intrinsic to the source. We discuss here the accumulating evidence showing that, at radio
wavelengths where the highest brightness temperatures are encountered, interstellar scintillation (ISS) is the principal mechanism
causing IDV. While ISS reduces the implied brightness temperatures, they still remain uncomfortably high.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
306.
Fluvial bedrock erosion rates due to impacting sediment particles are thought to be proportional to the energy delivered to the bedrock. When sediment particles cover the bed, they reduce the energy transmitted to the bed by an impacting particle. We measured the decline of energy transferred through sediment cover of increasing thickness in laboratory experiments. The energy arriving at the bed is a function both of the cover thickness and the grain size of the covering sediment. Using a simple stochastic model of cover distribution, the experimental results were upscaled to the reach scale. Although cover thickness influences energy delivery heavily at a given point, when averaging over the whole bed, cover-free areas dominate total energy delivery, making partial energy transfer through the cover negligible when a small or intermediate fraction of the bed is covered by sediment. Partial energy delivery through the bed cover is not negligible when a large fraction or the complete bed is already covered, but in this situation, an erosion threshold may become important. On grounds of the presented data, we expect that the areal distribution of sediment in a bedrock channel dominates total energy delivery and that partial energy delivery to the bed through a sediment layer can be neglected for most modelling purposes. 相似文献
307.
ABSTRACTThis study demonstrates that long-term climate model solutions can be efficiently converted to storm surge time series at points of interest (POIs) for the future. The all-source Green's function (ASGF) regression model is used for this conversion. In addition to being data assimilative, the ASGF regression model can also simulate storm surges at a POI faster than the traditional modelling approach by orders of magnitude. This is demonstrated using the tidal gauge at Sept-Îles (Quebec, Canada) in the Gulf of St. Lawrence as the POI. First the ASGF regression model is used to assimilate 32 years of tidal gauge data, producing a continuous hindcast of storm surges and a set of best-estimate regression parameters. Second, the ASGF regression model with the best-estimate parameters is used to convert a Canadian Regional Climate Model solution (CRCM/AHJ) to an hourly time series of storm surges from 1961 to 2100. Gumbel's extreme value analysis (EVA) is then applied to the time series as a whole and also to tri-decadal segments. The tri-decadal approach is used to investigate whether there is any progressive shortening or lengthening of storm surge return periods as a result of future climate change. A method for correcting for bias due to the forcing field at the EVA level is also demonstrated. 相似文献
308.
In the 2000 and 2001 springtime periods, mesozooplankton samples were systematically taken during research cruises devoted
to the study of the distribution and abundance of small pelagic fishes in the French part of the Bay of Biscay, NE Atlantic,
continental shelf. Simultaneous activities of three enzymes were measured in these mesozooplankton samples, to characterize
the main features of ecosystem function at a regional scale. The aim was to assess assimilation rates of carbohydrates, through
pyruvate kinase activity, and protein, through trypsin activity, by the mesozooplankton community and the resulting overall
productivity, through aspartate transcarbamylase activity. The highest influence on the pelagic environment was the strong
difference in the freshwater outflow rates from the two main large rivers, the Loire and the Gironde, which was principally
responsible for the inter-annual fluctuations of the nutrients in the Bay. This overall influence of river flow results in
a characteristic pattern of sea-surface salinity, which was reflected by the phytoplankton biomass distribution. Mesozooplankton
enzyme activities showed high variations between the two years. The contrast in the dynamics of the pelagic food web processes
between the two consecutive years, with higher activity in 2001, affected the nutritional condition of the zooplanktivorous
breeding anchovy Engraulis encrasicolus. 相似文献
309.
Michel Westphal Jean-Pierre Pozzi Yao Xiu Zhou Li Sheng Xing Xian Yao Chen 《Geophysical Journal International》1983,73(2):507-521
Summary. A palaeomagnetic study of Middle to late Cretaceous redbeds from Linzhou basin (Lhasa block), north of the Yarlung Zangbo suture zone, gives a stable palaeomagnetic direction of magnetization with a positive fold-test: six sites, 57 samples, D = 333°, I = 38°, k = 78, α95 = 8°, pole 64°N, 348°E. We discuss the problem of a possible remagnetization but consider that this direction of magnetization gives a good approximation for the palaeolatitude of the Lhasa block during Middle to late Cretaceous time. Results from more recent Tibetan formations are also presented: late Cretaceous to Palaeocene sediments and volcanics give a lower palaeolatitude of 10° N and but more recent andesites have emplaced about 30°N, close to the present-day latitude. An interpretation is proposed whereby the Lhasa block, which was a part of Asia in the early Cretaceous, has undergone first a southward motion accompanied by an anticlockwise rotation and then, after the Palaeocene, a northward motion under the constraint of the colliding India. 相似文献
310.
The paleomagnetic results from Tibet, north of the Yarlung-Zang bo suture zone, show that Tibet was at about 15°–20°N in Middle Cretaceous time. It then moved south down to 7°–10°N in the Late Cretaceous-Paleogene. The oceanic crust of the Xigaze ophiolites was magnetized at 13°N but thereafter migrated further south. This movement is compared with the relative movement of India and Asia as deduced from magnetic anomalies and paleomagnetism. Experimental models on deformation help us to explain how Tibet moved during the Late Cretaceous under the constraint of the Africa-Arabia indenter and during the Upper Tertiary under the constraint of the Indian indenter. 相似文献