全文获取类型
收费全文 | 1986篇 |
免费 | 405篇 |
国内免费 | 306篇 |
专业分类
测绘学 | 108篇 |
大气科学 | 139篇 |
地球物理 | 893篇 |
地质学 | 812篇 |
海洋学 | 244篇 |
天文学 | 12篇 |
综合类 | 145篇 |
自然地理 | 344篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 68篇 |
2021年 | 76篇 |
2020年 | 85篇 |
2019年 | 86篇 |
2018年 | 73篇 |
2017年 | 60篇 |
2016年 | 79篇 |
2015年 | 75篇 |
2014年 | 98篇 |
2013年 | 102篇 |
2012年 | 104篇 |
2011年 | 105篇 |
2010年 | 104篇 |
2009年 | 143篇 |
2008年 | 123篇 |
2007年 | 137篇 |
2006年 | 142篇 |
2005年 | 112篇 |
2004年 | 109篇 |
2003年 | 76篇 |
2002年 | 88篇 |
2001年 | 92篇 |
2000年 | 62篇 |
1999年 | 67篇 |
1998年 | 48篇 |
1997年 | 40篇 |
1996年 | 46篇 |
1995年 | 53篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 35篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1976年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2697条查询结果,搜索用时 140 毫秒
41.
Audrey GalvéAlfred Hirn Jiang MeiJosep Gallart Béatrice de VoogdJean-Claude Lépine Jordi DiazWang Youxue Qian Hui 《Earth and Planetary Science Letters》2002,203(1):35-43
New wide-angle reflection and refraction seismic data provide constraints on the structure of the upper lithosphere, and test models of its evolution to raise the northeastern part of the Tibetan Plateau. Amplitudes observed for reflections from the crust-mantle boundary are sufficiently large to suggest that there is no significant partial melt in the deep crust. The data show an increase of the crustal thickness between terranes from north of the Kun Lun Fault into the Qang Tang of central Tibet, and a contrast among their intracrustal images and compositions. In the north, P and S velocities are consistent with a dominantly felsic composition and show that only the upper crust thickened. South of the Kun Lun Fault a thicker crust made of two layers could result from the superposition of the originally thin crust of the Bayan Har terrane on the lower part of the crust of the domain to the north, which upper crust it shoved and thickened. Different modes of crustal thickening, either by thickening of individual layers or superpositions and imbrication among them appear to work jointly to raise the topography. 相似文献
42.
Comparison of Seismic Dispersion and Attenuation Models 总被引:2,自引:0,他引:2
The frequency-dependent attenuation of seismic waves causes decreased resolution of seismic images with depth, and the difference in transmission losses induces amplitude variations with offset. Transmission losses may occur due to friction or fluid movement, or may result from scattering in thin-layer. Whatever the physical mechanism, they can often be conveniently described using an empirical formulation wherein the elastic moduli and propagation velocity are complex functions of frequency.We have compiled and compared algebraically and numerically eight different models involving complex velocity: the Kolsky-Futterman model, the power-law model, Kjartansson's model, Müller's model, Azimi's second and third model, the Cole-Cole model, and the standard linear-solid model.For two different parameter sets, the attenuation and phase velocity are computed in the seismic frequency band, and the plane-wave propagation of a Ricker wavelet for the other models is compared with that for the Kolsky-Futterman model. The first parameter set consists of parameters for each of the models calculated from expressions given in the appendix. These expressions make the different models behave similarly to the KF model. The second parameter set consists of model parameters that are numerically adapted to the KF model.By selecting proper parameters, all models, except the standard linear-solid model, show behavior similar to that of the Kolsky-Futterman model. The SLS model behaves differently from the other models as the frequency goes to zero or infinity. Broadband measurement data is needed to select a specific model for a given seismic experiment. 相似文献
43.
多矿物岩石流变规律的研究进展及存在问题 总被引:4,自引:2,他引:4
总结了近年来由多种矿物组成的岩石的流变规律的研究,阐述了多矿物岩石流变性质研究的意义和进展,再从实验和理论两个方面,详细论述了目前最具代表性的三种理论模型,算术平均方法、几何平均方法和能量极小方法,最后,指出这方面研究仍然存在的问题和进一步研究的方向。 相似文献
44.
Yan Y. Kagan 《Geophysical Journal International》2002,149(3):731-754
45.
46.
Power-law attenuation in acoustic and isotropic anelastic media 总被引:1,自引:0,他引:1
47.
An anisotropic fractured poroelastic effective medium theory 总被引:1,自引:0,他引:1
S. R. Tod 《Geophysical Journal International》2003,155(3):1006-1020
48.
According to the measured data of typhoons going over the Chinese coasts in 1949-2002, a statistic relative equation showing the relation between the central atmospheric pressure of typhoons in a certain region at a certain period of time and their accumulation of frequency is established, and the concept of recurrence interval of typhoons is put forward, which is of actual significance for typhoon disaster reduction along the coastal area. 相似文献
49.
双鸭山矿区矿井充水规律研究 总被引:2,自引:0,他引:2
根据双鸭山矿区的水文地质条件及多年生产实践资料(矿井涌水量与其相关因素——地貌、采掘深度、回采面积、巷道长度、岩性、构造、降雨的关系),阐述了矿区充水的一般规律,提出了含水砂层覆盖下采区进行水文地质勘探的重点及开采含水砂层覆盖下煤炭资源的主要防治水措施,对同类水文地质条件矿井开采煤炭资源具有可借鉴意义。 相似文献
50.
研究了地下水中铜元素迁移富集的主要控制因素及其分布规律。结果表明,地下水铜元素的迁移富集与含水介质及其上覆土层中的铜元素含量、地下水的酸碱度、地下水的径流条件和氧化还原环境等有密切的关系。 相似文献