全文获取类型
收费全文 | 1241篇 |
免费 | 53篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 25篇 |
大气科学 | 91篇 |
地球物理 | 312篇 |
地质学 | 476篇 |
海洋学 | 117篇 |
天文学 | 212篇 |
综合类 | 2篇 |
自然地理 | 71篇 |
出版年
2023年 | 8篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 33篇 |
2018年 | 35篇 |
2017年 | 35篇 |
2016年 | 37篇 |
2015年 | 45篇 |
2014年 | 55篇 |
2013年 | 82篇 |
2012年 | 50篇 |
2011年 | 74篇 |
2010年 | 55篇 |
2009年 | 85篇 |
2008年 | 62篇 |
2007年 | 53篇 |
2006年 | 56篇 |
2005年 | 53篇 |
2004年 | 54篇 |
2003年 | 40篇 |
2002年 | 34篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1969年 | 6篇 |
1968年 | 3篇 |
排序方式: 共有1306条查询结果,搜索用时 15 毫秒
141.
Pierre Choukroune Xavier Le Pichon Michel Seguret Jean-Claude Sibuet 《Earth and Planetary Science Letters》1973,18(1):109-118
The different hypotheses proposed for the creation of the Bay of Biscay are reviewed. New geological and geophysical data collected in the last two years in the Bay and in the Pyrenean domain give new insight into the tectogenesis of the Pyrenees. Geological data of the Pyrenean area provide tight constraints on the hypothesis of formation of the Bay. The most probable hypothesis is an opening by rotation of the Iberian Peninsula around a pole of rotation situated near Paris, which resulted in strike-slip motion along the North Pyrenean fault during the Upper Mesozoic. A progressive westward migration of the pole initiated in the late Cretaceous blocked the motion along the fault and led to the main Eocene tectogenetic Pyrenean phase. 相似文献
142.
Structure,diversity and stability of two oligochaete communities according to sedimentary inputs in Lake Geneva (Switzerland) 总被引:3,自引:1,他引:3
Two oligochaete communities were sampled monthly during one year in two 35 m deep locations of Lake Geneva (Switzerland).
Organic sedimentation was lower and less variable in station 1 than in station 2 (157 versus 214 g C m−2yr−1). The oligochaete community in station 1 was more diverse and more stable (persistent over time) than in station 2, as long
as the organic sedimentation was low. Diversity and stability decreased in station 1 when the organic sedimentation increased,
and during anOscillatoria bloom. The less diverse community in station 2 was more resistent to these changes. Diversity was associated with environmental
stability, but resistance to perturbation was greater in the simpler community which is adapted to changing environmental
conditions. The value of oligochaete communities as an indicator of the level of eutrophication was reassessed according to
our present data. Changes in the structure of oligochaete communities were related to changes in sedimentation processes. 相似文献
143.
Pierre Hudon In-Ho Jung Don R. Baker 《Physics of the Earth and Planetary Interiors》2002,130(3-4):159-174
Melting relations of β-quartz were experimentally determined at 1.0 GPa (1900±20 °C), 1.5 GPa (2033±20 °C), and 2.0 GPa (2145±20 °C) using a new high-pressure assembly in a piston–cylinder apparatus and substantial differences were found with data previously reported. The new melting data of β-quartz were combined and optimized with all available thermodynamic, volumetric, and phase equilibria data for β-cristobalite, β-quartz and coesite to produce a P–T liquidus diagram for silica valid up to 6.0 GPa. Using the new optimized thermodynamic parameters, the invariant point β-cristobalite+β-quartz+liquid and β-quartz+coesite+liquid were determined to lie at 1687±17 °C and 0.457 GPa, and 2425±25 °C and 5.00 GPa, respectively. 相似文献
144.
145.
Claude Robin Philippe Mossand Guy Camus Jean-Marie Cantagrel Alain Gourgaud Pierre M. Vincent 《Journal of Volcanology and Geothermal Research》1987,31(1-2)
The evolution of the Colima volcanic complex can be divided into successive periods characterized by different dynamic and magmatic processes: emission of andesitic to dacitic lava flows, acid-ash and pumice-flow deposits, fallback nuées ardentes leading to pyroclastic flows with heterogeneous magma, plinian air-fall deposits, scoriae cones of alkaline and calc-alkaline nature. Four caldera-forming events, resulting either from major ignimbrite outbursts or Mount St. Helens-type eruptions, separate the main stages of development of the complex from the building of an ancient shield volcano (25 × 30 km wide) up to two summit cones, Nevado and Fuego.The oldest caldera, C1 (7–8 km wide), related to the pouring out of dacitic ash flows, marks the transition between two periods of activity in the primitive edifice called Nevado I: the first one, which is at least 0.6 m.y. old, was mainly andesitic and effusive, whereas the second one was characterized by extrusion of domes and related pyroclastic products. A small summit caldera, C2 (3–3.5 km wide), ended the evolution of Nevado I.Two modern volcanoes then began to grow. The building of the Nevado II started about 200,000 y. ago. It settled into the C2 caldera and partially overflowed it. The other volcano, here called Paleofuego, was progressively built on the southern side of the former Nevado I. Some of its flows are 50,000 y. old, but the age of its first outbursts is not known. However, it is younger than Nevado II. These two modern volcanoes had similar evolutions. Each of them was affected by a huge Mount St. Helens-type (or Bezymianny-type) event, 10,000 y. ago for the Paleofuego, and hardly older for the Nevado II. The landslides were responsible for two horseshoe-shaped avalanche calderas, C3 (Nevado) and C4 (Paleofuego), each 4–5 km wide, opening towards the east and the south. In both cases, the activity following these events was highly explosive and produced thick air-fall deposits around the summit craters.The Nevado III, formed by thick andesitic flows, is located close to the southwestern rim of the C3 caldera. It was a small and short-lived cone. Volcan de Fuego, located at the center of the C4 caldera, is nearly 1500 m high. Its activity is characterized by an alternation of long stages of growth by flows and short destructive episodes related to violent outbursts producing pyroclastic flows with heterogeneous magma and plinian air falls.The evolution of the primitive volcano followed a similar pattern leading to formation of C1 and then C2. The analogy between the evolutions of the two modern volcanoes (Nevado II–III; Paleofuego-Fuego) is described. Their vicinity and their contemporaneous growth pose the problem of the existence of a single reservoir, or two independent magmatic chambers, after the evolution of a common structure represented by the primitive volcano. 相似文献
146.
147.
148.
Nicole Vatin-Prignon Pierre Goemans Richard A. Oliver Eduardo Parra Palacio 《Journal of Volcanology and Geothermal Research》1990,41(1-4)
Trace-element concentrations of the eruptive products from the Nevado del Ruiz volcano indicate that at least for the last 1 Ma, the major controlling factor in the evolution of the magma has been a simple fractional crystallization.The Zr/Hf ratios suggest that the source material is mantle-like in origin and whilst subduction-related contamination of the source material has taken place, there is no evidence that assimilation of continental crust has affected the series.No convincing geochemical evidence for magma mixing was found, and data on banded pumices of Pleistocene, Historic and the 1985 eruptions strongly support a crystal fractionation model to explain the compositional variation of their glasses. Therefore, if mixing has taken place it can only be a mixing of layers within a stratified or partially stratified magma chamber.Modeling of fractional crystallization using a stepwise program has been undertaken and least-squares approximations with small residuals are commensurate with analyzed samples. Crystal fractionation models with plagioclase dominating two-pyroxenes and iron oxides give good fits for all calculations. We conclude that simple crystal fractionation is the process most consistent with major- and trace-element variations in the Ruiz series. This closed-system model requires at least 77% crystal fractionation of a basaltic parent to generate the observed compositions of dacites. 相似文献
149.
The application of trichloroacetic acid (TCA) as a shell extractant for preparation of soft body parts with reference to tissue metal concentrations (Cd, Cu, Pb, Zn) in shellfish has been evaluated on the example of the mud snail Hydrobia ulvae, a small marine prosobranch densely present in rocky and soft-bottom habitats of the eastern Atlantic. A solution of 0.1 M TCA was tested on individuals treated according to two different protocols: (1) thawed after freezing ("non-dried") and (2) thawed and air-dried to a constant weight ("dried"). Two points were investigated in detail to improve the method: individual soft tissue dry weight and tissue metal concentration following a standard digestion method. In both instances, the results were compared with those from manually dissected snails. Conditions for total shell decalcification of 60 individuals (3-4 mm long) were 5.5 h in 20 ml of 0.1 M TCA.No differences in individual soft tissue weight were observed between the treatments, indicating good efficiency of the TCA extraction with respect to weight of soft body parts. In contrast, tissue metal concentrations varied among treatments. The TCA extraction of the dried animals had a good recovery for Cd, most likely due to the lower solubility of Cd vital cellular components (proteins and mineral concretions) from the dried tissue. Satisfactory recoveries of the tissue concentrations of Cu and Pb were obtained for the non-dried individuals. This might be related to the specific distribution of metals in the organism (namely in the digestive glands and gonads) and their different chemical reactivity with TCA after the tissue was dried. Limited susceptibility of Zn-bearing protein bindings to complexing with TCA also accounts for significantly lower concentrations of Zn in the mud snail's soft tissue that was extracted. The 0.1 M TCA solution is therefore recommended for extraction of the shells of Hydrobia ulvae for tissue determination of Cd, Cu and Pb; however the treatment protocol does affect metal recovery and thus a consistent procedure should be followed.The extracted metals from the soft tissues and shells of the mud snails (on the basis of both metal concentrations and contents) were ranked in order of increasing contribution of soft body parts to the total (shell+tissue): Pb相似文献
150.