全文获取类型
收费全文 | 1989篇 |
免费 | 391篇 |
国内免费 | 384篇 |
专业分类
测绘学 | 299篇 |
大气科学 | 114篇 |
地球物理 | 545篇 |
地质学 | 1031篇 |
海洋学 | 375篇 |
天文学 | 30篇 |
综合类 | 169篇 |
自然地理 | 201篇 |
出版年
2024年 | 11篇 |
2023年 | 28篇 |
2022年 | 53篇 |
2021年 | 72篇 |
2020年 | 72篇 |
2019年 | 100篇 |
2018年 | 64篇 |
2017年 | 89篇 |
2016年 | 93篇 |
2015年 | 94篇 |
2014年 | 97篇 |
2013年 | 107篇 |
2012年 | 128篇 |
2011年 | 130篇 |
2010年 | 103篇 |
2009年 | 111篇 |
2008年 | 115篇 |
2007年 | 146篇 |
2006年 | 139篇 |
2005年 | 116篇 |
2004年 | 141篇 |
2003年 | 94篇 |
2002年 | 84篇 |
2001年 | 61篇 |
2000年 | 62篇 |
1999年 | 63篇 |
1998年 | 58篇 |
1997年 | 67篇 |
1996年 | 51篇 |
1995年 | 35篇 |
1994年 | 46篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有2764条查询结果,搜索用时 15 毫秒
91.
Near Bordeaux (France), the Oligocene aquifer is a potential target for drinking water supply. A high-resolution seismic campaign and several exploration wells helped to clarify the geometry of this formation and, as a consequence, the Medoc Tertiary aquifers. The major information extracted from these new data is the existence of a soft deformation inducing two different deposit areas, showing different hydrogeological characteristics (thickness, type, hydraulic properties, etc.). The presence of an erosional gap area affecting the Oligocene formations lead us to propose a new image of groundwater flow in the area, in the context of a predicted intensive exploitation of this resource. To cite this article: F. Larroque, A. Dupuy, C. R. Geoscience 336 (2004). 相似文献
92.
93.
B.R. Goleby R.S. Blewett R.J. Korsch D.C. Champion K.F. Cassidy L.E.A. Jones P.B. Groenewald P. Henson 《Tectonophysics》2004,388(1-4):119
Deep seismic reflection data across the Archaean Eastern Goldfields Province, northeastern Yilgarn Craton, Western Australia, have provided information on its crustal architecture and on several of its highly mineralised belts. The seismic reflection data allow interpretation of several prominent crustal scale features, including an eastward thickening of the crust, subdivision of the crust into three broad layers, the presence of a prominent east dip to the majority of the reflections and the interpretation of three east-dipping crustal-penetrating shear zones. These east-dipping shear zones are major structures that subdivide the region into four terranes. Major orogenic gold deposits in the Eastern Goldfields Province are spatially associated with these major structures. The Laverton Tectonic Zone, for example, is a highly mineralised corridor that contains several world-class gold deposits plus many smaller deposits. Other non crustal-penetrating structures within the area do not appear to be as well endowed metallogenically as the Laverton structure. The seismic reflection data have also imaged a series of low-angle shear zones within and beneath the granite–greenstone terranes. Where the low-angle shear zones intersect the major crustal-penetrating structures, a wedge shaped geometry is formed. This geometry forms a suitable fluid focusing wedge in which upward to subhorizontal moving fluids are focused and then distributed into the nearby complexly deformed greenstones. 相似文献
94.
95.
The reflection of plane waves in a poroelastic half-space saturated with inviscid fluid 总被引:8,自引:2,他引:8
Chi-Hsin Lin Vincent W. Lee Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2005,25(3):205-223
This paper discusses surface displacements, surface strain, rocking, and energy partitioning during reflection-of-plane waves in a fluid-saturated poroelastic half-space. The medium is modeled by Biot's theory, and is assumed to be saturated with inviscid fluid. A linear porosity-modulus relation based on experimental data on sandstones is used to determine the material parameters for Biot's model. Numerical results in terms of angle of incident waves and Poisson's ratio are illustrated for various porosities and degrees of solid frame stiffness. The results show that the amount of solid frame stiffness controls the response of a fluid-saturated porous system. A poroelastic medium with essentially dry-frame stiffness behaves like an elastic medium, and the influence of pore fluid increases as dry-frame stiffness is reduced. The effects of a second P-wave become noticeable in poroelastic media with low dry-frame stiffness. 相似文献
96.
Introduction China is a country with many landslides and debris flows. These disasters bring out a large amount of losses of life and property. It is significant to predict landslide incident by monitoring the deformations of these landslides. At past, triangulation and trilateration are traditional tools, but it is very difficult for them to realize real-time monitoring, and it is more dangerous for obser- vation workers when the deformation becomes larger. Because of many advantages such as… 相似文献
97.
V. Grechka 《Studia Geophysica et Geodaetica》2005,49(3):365-381
All methods of seismic characterization of fractured reservoirs are based on effective media theories that relate geometrical and material properties of fractures and surrounding rock to the effective stiffnesses. In exploration seismology, the first-order theory of Hudson is the most popular. It describes the effective model caused by the presence of a single set of thin, aligned vertical fractures in otherwise isotropic rock. This model is known to be transversely isotropic with a horizontal symmetry axis (HTI). Following the theory, one can invert the effective anisotropy for the crack density and type of fluid infill of fractures, the quantities of great importance for reservoir appraisal and management.Here I compute effective media numerically using the finite element method. I deliberately construct models that contain a single set of vertical, ellipsoidal, non-intersecting and non-interconnected fractures to check validity of the first-order Hudson’s theory and establish the limits of its applicability. Contrary to conventional wisdom that Hudson’s results are accurate up to crack density e ≈ 0.1, I show that they consistently overestimate the magnitudes of all effective anisotropic coefficients ε(V), δ(V), and γ(V). Accuracy of theoretically derived anisotropy depends on the type of fluid infill and typically deteriorates as e grows. While the theory gives | ε(V)|, |δ(V)|, |γ(V)| and close to the upper bound of the corresponding numerically obtained values for randomly distributed liquid-filled fractures, theoretical predictions of ε(V), δ(V) are not supported by numerical computations when the cracks are dry. This happens primarily because the first-order Hudson’s theory makes no attempt to account for fracture interaction which contributes to the final result much stronger for gas- than for liquid-filled cracks. I find that Mori-Tanaka’s theory is superior to Hudson’s for all examined crack densities and both types of fluid infill.The paper was presented at the 11th International Workshop on Seismic Anisotropy (11IWSA) held in St. John’s, Canada in 2004. 相似文献
98.
99.
100.