全文获取类型
收费全文 | 1761篇 |
免费 | 389篇 |
国内免费 | 332篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 29篇 |
地球物理 | 779篇 |
地质学 | 988篇 |
海洋学 | 60篇 |
天文学 | 25篇 |
综合类 | 58篇 |
自然地理 | 536篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 57篇 |
2020年 | 60篇 |
2019年 | 76篇 |
2018年 | 73篇 |
2017年 | 50篇 |
2016年 | 75篇 |
2015年 | 72篇 |
2014年 | 92篇 |
2013年 | 94篇 |
2012年 | 91篇 |
2011年 | 80篇 |
2010年 | 78篇 |
2009年 | 95篇 |
2008年 | 118篇 |
2007年 | 140篇 |
2006年 | 144篇 |
2005年 | 114篇 |
2004年 | 108篇 |
2003年 | 89篇 |
2002年 | 85篇 |
2001年 | 60篇 |
2000年 | 65篇 |
1999年 | 65篇 |
1998年 | 59篇 |
1997年 | 55篇 |
1996年 | 53篇 |
1995年 | 40篇 |
1994年 | 55篇 |
1993年 | 36篇 |
1992年 | 29篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有2482条查询结果,搜索用时 15 毫秒
1.
2.
V. Maupin 《Geophysical Journal International》1985,83(2):379-398
Summary. Surface wave behaviour in flat anisotropic structures is first illustrated by performing an exact computation on a simple two-layer model. The variational procedure of Smith & Dahlen is then used to compute the partial derivatives of surface wave phase velocities with respect to the elastic parameters in more realistic earth models. Linear relationships between the partial derivatives for a general anisotropic structure and those for a transversely isotropic structure are derived. When considering waves propagating in a fixed direction, there are only four independent derivatives for Rayleigh waves, and two for Love waves. To avoid the lack of resolution in an inverse method, we propose to use physically constrained models. These results are illustrated by using a model with hexagonal symmetry and a symmetry axis oriented either vertically or horizontally. Quasi-Love- and quasi-Rayleigh-wave partial derivatives are computed for both axis orientations. Modes up to the second overtone and periods ranging between 45 and 130 s have been considered. Finally, anomalies of phase velocity are computed in an oceanic model made of 1/6 oriented olivine crystals with horizontal or vertical preferred orientations of the a -axis. 相似文献
3.
Wave propagation in anisotropic linear viscoelastic media: theory and simulated wavefields 总被引:6,自引:0,他引:6
J. M. Carcione 《Geophysical Journal International》1990,101(3):739-750
4.
Summary. Multiparameter inversions of multimode dispersion data are performed for two large regions: the Pacific Ocean and North America. Anisotropy is taken into account by considering transversely isotropic structures with a vertical axis of symmetry. Two fundamental questions are studied in detail: (1) how to make the inverted models consistent when using different sets of parameters, (2) what is the significance of transversely isotropic inversion for the actual Earth's structure? It is proved that full consistency of the inverted models can be achieved by properly taking into account some a priori informations on the model and it is shown that the use of transversely isotropic models with vertical axis of symmetry does not cause severe limitations when interpreting the data. The models we have obtained are discussed in the light of these investigations. Considering an olivine-rich upper mantle, we make a tentative interpretation of these models in terms of preferred orientation of the a -axis of the crystals in one fixed horizontal direction. 相似文献
5.
6.
Yannis F. Dafalias Majid T. Manzari Achilleas G. Papadimitriou 《国际地质力学数值与分析法杂志》2006,30(12):1231-1257
SANICLAY is a new simple anisotropic clay plasticity model that builds on a modification of an earlier model with an associated flow rule, in order to include simulations of softening response under undrained compression following Ko consolidation. Non‐associativity is introduced by adopting a yield surface different than the plastic potential surface. Besides, the isotropic hardening of the yield surface both surfaces evolve according to a combined distortional and rotational hardening rule, simulating the evolving anisotropy. Although built on the general premises of critical state soil mechanics, the model induces a critical state line in the void ratio–mean effective stress space, which is a function of anisotropy. To ease interpretation, the model formulation is presented firstly in the triaxial stress space and subsequently, its multiaxial generalization is developed systematically, in a form appropriate for implementation in numerical codes. The SANICLAY is shown to provide successful simulation of both undrained and drained rate‐independent behaviour of normally consolidated sensitive clays, and to a satisfactory degree of accuracy of overconsolidated clays. The new model requires merely three constants more than those of the modified Cam clay model, all of which are easily calibrated from well‐established laboratory tests following a meticulously presented procedure. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
8.
9.
10.
安溪县铅山铅锌矿区地质普查阶段开展了物探工作(激电中梯剖面、激电测深),发现了激电异常,结合矿区成矿地质条件,推断异常是由隐伏铅锌矿(化)引起,提出了进一步工作的建议,经钻探验证得以证实。该区激电异常是一个深部找矿的有效标志,电法工作为该普查区顺利转入详查阶段起了一定作用。 相似文献