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61.
Jack Dymond Richard Cobler Louis Gordon Pierre Biscaye Guy Mathieu 《Earth and Planetary Science Letters》1983,64(3):417-429
Hydrothermal waters collected by “Alvin” from the Galapagos Spreading Center are enriched in222Rn by factors of 50–200 over bottom waters. The226Ra in the same samples, however, is enriched by less than a factor of four over bottom waters. Enrichments of222Rn result primarily from α-recoil from rock surfaces while226Ra enrichments are dominantly produced by high-temperature alteration of cooling ridge volcanics. The abundances of both nuclides exhibit positive correlations with temperature. The data extrapolate to bottom water temperatures and compositions, demonstrating the importance of seawater mixing. Different vents, however, have different mixing lines, and vents with high222Rn have low226Ra. We propose these patterns result from variations in the extent of low-temperature crustal interaction with the hydrothermal fluids. Low-temperature crustal waters can maintain high steady state222Rn contents due to the α-recoil additions to the fluids. The226Ra, however, is strongly adsorbed at low-temperatures resulting in low concentrations of this nuclide in low-temperature crustal waters. Thus, physical mixing of a crustal water component with hydrothermal waters or variable crustal path lengths of the hydrothermal fluids can account for the variable mixing lines and222Rn/226Ra values of the hot springs.The222Rn/226Ra value appears to be a sensitive indicator of low-temperature crustal interaction. Values > 100 have experienced extensive crustal interaction and are indicative of diffuse hydrothermal flow. Values between 1 and 10 are indicative of primary hydrothermal fluids which have not experienced significant interaction with the crust. Values of222Rn/226Ra between 103 and 104 are indicative of interaction of the hydrothermal fluids with sediments. Such values are observed in water samples from the Galapagos hydrothermal mounds. 相似文献
62.
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64.
Jacques Mathieu Fabrice Jeannerod Frédéric Hervant Thomas C. Kane 《Aquatic Sciences - Research Across Boundaries》1997,59(1):39-47
Electrophoretic variation in proteins encoded by seven presumptive gene loci was analyzed in four populations of the stygobiont amphipodNiphargus rhenorhodanensis. The four populations occur in different habitats, including one in drainage canals, another from sediments of the Ain River, a tributary of the Rhône River, and the remaining two occur in a karstic massif (Dorvan, Ain, France) in the epikarstic and at the base level of the massif, respectively. Six of the seven loci were polymorphic within or among populations, with as many as three electromorphs segregating at the most variable loci. Significant deficiencies in the frequency of heterozygotes were common. Genetic divergence between the two populations of the Dorvan Massif and between the two of the Ain River (forest and sediment habitats) was large. This was highly unexpected, particularly in the case of the two hydrologically connected populations of the Dorvan Massif. It is suggested that either low migration rates or the presence of ecological barriers to gene flow may result in strong genetic differention among local populations ofNiphargus. 相似文献
65.
Wallace S. Broecker Rik Wanninkhof Guy Mathieu Tsung-Hung Peng Scott Stine Steve Robinson Andy Herczeg Minze Stuiver 《Earth and Planetary Science Letters》1988,88(1-2)
Since 1957 the 14C/C ratio of the dissolved inorganic carbon in Mono Lake has risen by about 60‰. The magnitude of this increase is about four times larger than that expected from the invasion of bomb-produced14C from the atmosphere. We have eliminated the following explanations: (1) measurement error, (2) an unusually high physical exchange rate for non-reactive gases, (3) inorganic enhancement of the CO2 exchange rate, and (4) biological enhancement of the CO2 exchange rate. Clandestine disposal of waste radiocarbon remains a dark-horse explanation.In the course of our investigations we have uncovered evidence for at least one episodic input of radiocarbon-free carbon to the lake over the last 1000 years. We speculate that this injection was related to a hydrothermal event resulting from sublacustrine volcanic activity. 相似文献
66.
Mathieu Schuster Philippe Duringer Jean‐Francois Ghienne Patrick Vignaud Alain Beauvilain Hassan Taisso Mackaye Michel Brunet 《地球表面变化过程与地形》2003,28(10):1059-1069
This paper reports on a study dealing with the rhyolitic inselbergs of Hadjer el Khamis that formed palaeoislands during Lake Mega‐Chad events. Field observations have shown that: (1) conglomeratic patches of immature to mature clasts are preserved at the feet of the Hadjer el Khamis inselbergs; (2) in cross‐section, their pro?le reveals a well de?ned cliff–platform junction at a constant elevation (325 m). The monolithological clasts show all degrees of roundness, from angular cobbles to well rounded pebbles. This wide range of maturity suggests a coastal origin for these cobbles. The system was permanently fed with angular clasts, which were progressively worn by waves. Cobbles that were wave‐worked for the longest time are the best rounded. The cliff–platform junction is the result of erosion by waves, which attacked and undercut the inselberg cliffs during Lake Mega‐Chad events. Asymmetrical erosion pro?les moreover suggest a wind regime dominated by SW to NE oriented winds. These interpretations have two implications. The elevation of the cliff–platform junction is an indication of the highest water level of Lake Mega‐Chad at 320–325 m, which is in agreement with other observations elsewhere in the basin. The SW to NE oriented winds show that monsoon‐related winds were prevalent during Lake Mega‐Chad events, suggesting the Inter‐Tropical Convergence Zone was located higher in latitude than today. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
67.
Vania Rosolen Mathieu Lamotte René Boulet Jean Trichet Olivier Rouer Adolpho José Melfi 《Comptes Rendus Geoscience》2002,334(3):187-195
A mottled horizon in a laterite cover (without any duricrust) was studied by microscopy and quantitative chemical microanalysis. Apart from the voids, light red spots consisting of Fe-rich particles (≈2 μm) are set in clayey plasma. Dark red spots consisted of concentrations of Fe-rich particles. These patterns are inherited. On the border of structural or biological voids, where Fe-depletion features are systematic, gray or yellow spots result from dissolution of the Fe-rich particles and impregnation of the plasma by iron, respectively. The present Fe-depletion is the dominant process that explains the mottled differentiation and the absence of lateritic duricrust. To cite this article: V. Rosolen et al., C. R. Geoscience 334 (2002) 187–195. 相似文献
68.
This paper presents an overview of some of the most significant, recent to ancient, littoral morpho-sedimentary structures and deposits from the Lake Turkana Basin. We highlight the importance of wave-related sedimentary processes in lakes, and more specifically in rift lakes. In the published literature, references to wave-dominated shorelines are mainly in regards to coastal marine environments. However, numerous modern lakes exhibit typical wave-dominated littoral landforms, and related sedimentary deposits are known from several paleolake successions in the geological record. Wave-related processes are often of relatively minor importance in depositional models for lacustrine environments. Classical models emphasize clastics transported by rivers, which are then distributed by fan-deltas and/or deltas into a water body of fluctuating depth, where reworking of clastics is limited in the littoral domain, and episodic in deep waters. Modern processes in Lake Turkana and the exposed paleolake deposits of the Turkana Basin demonstrate that this view is incomplete. Wave-dominated shorelines are evident (1) for modern Lake Turkana based on prominent and active littoral landforms (e.g., beach ridges, sand spits, washover fans, and arcuate-cuspate deltas); (2) for the Holocene (African Humid Period) climate-driven highstand of Megalake Turkana and its subsequent forced regression based on conspicuous raised beach ridges and spits; and (3) for the Pliocene–Pleistocene (Omo Group, Nachukui Formation) from typical nearshore sedimentary facies and stratigraphic architectures associated with paleolake Turkana. These examples from the Turkana Basin coupled with examples from other lacustrine settings, suggest that wave-dominated clastic shorelines represent significant portions of existing and ancient lake-shores. As this view contrasts with classic depositional models for lakes, notably for those found in rift setting, we also present examples of wave-influenced littoral landforms from other lakes of the East African Rift System. Identifying lacustrine paleoshorelines from typical clastic landforms and deposits is the key to the spatial reconstruction of lakes over time, and to determine transgressive–regressive cycles. Waves action is an important agent in lakes for the erosion, transport, and deposition of clastics at the basin-scale, an aspect that needs to be integrated in sedimentary models. 相似文献
69.
Jessica Barabasch Mathieu Ducros Nicolas Hawie Samer Bou Daher Fadi Henri Nader Ralf Littke 《Basin Research》2019,31(2):228-252
The Eastern Mediterranean Levant Basin is a proven hydrocarbon province with recent major gas discoveries. To date, no exploration wells targeted its northern part, in particular the Lebanese offshore. The present study assesses the tectono‐stratigraphic evolution and related petroleum systems of the northern Levant Basin via an integrated approach that combines stratigraphic forward modeling and petroleum systems/basin modeling based on the previous published work. Stratigraphic modeling results provide a best‐fit realisation of the basin‐scale sedimentary filling, from the post‐rift Upper Jurassic until the Pliocene. Simulation results suggest dominant eastern marginal and Arabian Plate sources for Cenozoic siliciclastic sediments and a significant contribution from the southern Nilotic source mostly from Lower Oligocene to Lower Miocene. Basin modeling results suggest the presence of a working thermogenic petroleum system with mature source rocks localised in the deeper offshore. The generated hydrocarbons migrated through the deep basin within Jurassic and Cretaceous permeable layers towards the Latakia Ridge in the north and the Levant margin and offshore topographic highs. Furthermore, the basin model indicates a possibly significant influence of salt deposition during Messinian salinity crisis on formation fluids. Ultimately, the proposed integrated workflow provides a powerful tool for the assessment of petroleum systems in underexplored areas. 相似文献
70.
The 15-km-long Matane pockmark train belongs to a series of NNE-striking alignments of pockmarks mapped on the seafloor of the St. Lawrence Estuary. It includes 109 pockmarks that show a complete transition from well-defined, relatively deep (up to 8.6 m), crater-like depressions to subtle, partly buried morphological features, suggesting that pockmarks have formed at different periods along the whole alignment and that the location of fluid release has changed through time. On seismic profiles, pockmarks are characterized by vertical seismic chimneys that root in the (fractured?) hinge zone of an open anticline within the autochthonous Palaeozoic rocks of the St. Lawrence Platform. In absence of a geochemical characterization of expelled gas, the relationship between the Matane pockmark train and the anticline in a domain characterized by mature source rocks is the strongest evidence for the genetic link between pockmarks and the release of gas from an active hydrocarbon system or a reservoir located in the Palaeozoic succession. Figure
Alignment of the Matane pockmark train along a buried bedrock anticline of the Lower St. Lawrence Estuary 相似文献