全文获取类型
收费全文 | 15317篇 |
免费 | 3376篇 |
国内免费 | 1455篇 |
专业分类
测绘学 | 496篇 |
大气科学 | 1314篇 |
地球物理 | 11666篇 |
地质学 | 3868篇 |
海洋学 | 465篇 |
天文学 | 28篇 |
综合类 | 1195篇 |
自然地理 | 1116篇 |
出版年
2024年 | 24篇 |
2023年 | 150篇 |
2022年 | 396篇 |
2021年 | 590篇 |
2020年 | 515篇 |
2019年 | 593篇 |
2018年 | 571篇 |
2017年 | 570篇 |
2016年 | 496篇 |
2015年 | 653篇 |
2014年 | 873篇 |
2013年 | 827篇 |
2012年 | 865篇 |
2011年 | 935篇 |
2010年 | 843篇 |
2009年 | 1104篇 |
2008年 | 850篇 |
2007年 | 1016篇 |
2006年 | 936篇 |
2005年 | 891篇 |
2004年 | 801篇 |
2003年 | 765篇 |
2002年 | 604篇 |
2001年 | 549篇 |
2000年 | 530篇 |
1999年 | 452篇 |
1998年 | 423篇 |
1997年 | 406篇 |
1996年 | 388篇 |
1995年 | 372篇 |
1994年 | 326篇 |
1993年 | 255篇 |
1992年 | 210篇 |
1991年 | 109篇 |
1990年 | 81篇 |
1989年 | 55篇 |
1988年 | 49篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1979年 | 15篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
In recent years,scholars at home and abroad have method,and that vanous disasters would be analyzed assynthetically studied natural dlsaste‘theoretically and an Integral.SHI Peilun(1991)putforwad a scientificmethodologlcally,as well as its cases analys。s(CND,term—regional disaster system,which Indicates that1987; MA et al,1990; MARBLE,1990; NE et al,the situation of a disaster(calamity loss)results from1999; PATAK et al,1982; SHI,1991;VAN et al,h… 相似文献
22.
通过对蓄水前后三峡库首区构造应力场进行三维数值模拟发现,相对于蓄水前,蓄水至135 m水位时,官渡口断裂-马鹿池断裂-牛口断裂围限区、秭归地理中心和九湾溪断裂带,出现了4个主应力下降区和共轭的主应力增长区,形成了差应力场;175 m水位与135 m水位相比,局部差应力场呈现逆向变化,即形成了加载效应与卸载效应的交替过程。这一过程,可能是水库诱发地震的诱震(或触震)因素。 相似文献
23.
Kenai, located on the west coast of the Kenai Peninsula, Alaska, subsided during the great earthquake of AD 1964. Regional land subsidence is recorded within the estuarine stratigraphy as peat overlain by tidal silt and clay. Reconstructions using quantitative diatom transfer functions estimate co‐seismic subsidence (relative sea‐level rise) between 0.28±0.28 m and 0.70±0.28 m followed by rapid post‐seismic recovery. Stratigraphy records an earlier co‐seismic event as a second peat‐silt couplet, dated to ~1500–1400 cal. yr BP with 1.14±0.28 m subsidence. Two decimetre‐scale relative sea‐level rises are more likely the result of glacio‐isostatic responses to late Holocene and Little Ice Age glacier expansions rather than to co‐seismic subsidence during great earthquakes. Comparison with other sites around Cook Inlet, at Girdwood and Ocean View, helps in constructing regional patterns of land‐level change associated with three great earthquakes, AD 1964, ~950–850 cal. yr BP and ~1500–1400 cal. yr BP. Each earthquake has a different spatial pattern of co‐seismic subsidence which indicates that assessment of seismic hazard in southern Alaska requires an understanding of multiple great earthquakes, not only the most recent. All three earthquakes show a pre‐seismic phase of gradual land subsidence that marked the end of relative land uplift caused by inter‐seismic strain accumulation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
24.
Current plate motions 总被引:57,自引:0,他引:57
25.
In this paper the second order characteristic (discontinuous bifurcation) condition is derived for the granular flow (fully plastic) equations. This second order bifurcation equation is shown to be formally identical to the first order localization requirement during steady elastoplastic deformation provided the elastic compliance tensor is substituted for the product of the plastic multiplier with the flow Hessian. For isotropic yield and flow functions the invariant form of the characteristic condition is given in detail, as well as an alternative expression in adapted co‐ordinates. The characteristic condition can be regarded as defining a hardening function which is maximized to identify the critical angles. When the method is applied to 3D Coulomb flow, Mohr's 3D fracture plane conditions are obtained uniquely. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
26.
1StrongtideandastronomicalconditionsPartial solar eclipse occurred 4 times in 1964, 1982 and 2000 respectively. Time interval is about 3 Saros periods (one Saros period is 18 years and 10.33~11.33 days). Total lunar eclipse occurred 2 times in 1964 and 2000 respectively and 3 times in 1982. However, there was no lunar eclipse in 1966, 1984 and 2002. It seems that they had similar astro-nomical conditions and the best was in 1982. The studies about the effect of tide on the global climate… 相似文献
27.
28.
29.
利用西安数字地震遥测台网记录的数字地震资料,采用P波初动半周期残差法求得1998年7月临猗5.0级地震前后不同路径的Q(品质因子)值变化,发现在地震发生前Q值为87~203,震后Q值为67~164,震前震中区附近出现明显的高Q值异常。结果表明,地震前的高Q值异常可以作为地震预测的一种手段。 相似文献
30.
Univariate and multivariate stress release models are fitted to historical earthquake data from North China. It is shown that a better fit is obtained by treating separately the Eastern part of the region, including the North China Plain and Bohai Sea, and the Western part of the region, including the Ordos Plateau and its Eastern boundary. Further improvement is obtained by fitting the large events (M7.6) and smaller events in the Western region by different stress release models. The comparisons are made by computing the likelihoods of the fitted models and discounting the number of parameters used by Akaike's AIC criterion. The models are used to develop long-term risk scenarios for the East and West regions. 相似文献