全文获取类型
收费全文 | 138篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
地球物理 | 51篇 |
地质学 | 25篇 |
综合类 | 4篇 |
自然地理 | 69篇 |
出版年
2022年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 13篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 140 毫秒
81.
Subduction zone earthquakes and stress in slabs 总被引:3,自引:0,他引:3
Summary The pattern of seismicity as a function of depth in the world, and the orientation of stress axes of deep and intermediate earthquakes, are explained using viscous fluid models of subducting slabs, with a barrier in the mantle at 670 km. 670 km is the depth of a seismic discontinuity, and also the depth below which earthquakes do not occur. The barrier in the models can be a viscosity increase of an order of magnitude or more, or a chemical discontinuity where vertical velocity is zero. LongN versus depth, whereN is the number of earthquakes, shows (1) a linear decrease to about 250–300 km depth, (2) a minimum near that depth, and (3) an increase thereafter. Stress magnitude in a subducting slab versus depth, for a wide variety of models, shows the same pattern. Since there is some experimental evidence thatN is proportional toe
, where is a constant and is the stress magnitude, the agreement is encouraging. In addition, the models predict down-dip compression in the slab at depths below 400 km. This has been observed in earlier studies of earthquake stress axes, and we have confirmed it via a survey of events occurring since 1977 which have been analysed by moment tensor inversion. At intermediate depths, the models predict an approximate but not precise state of down-dip tension when the slab is dipping. The observations do not show an unambiguous state of down-dip tension at intermediate depths, but in the majority of regions the state of stress is decidedly closer to down-dip tension than it is to down-dip compression. Chemical discontinuities above 670 km, or phase transitions with an elevation of the boundary in the slab, predict, when incorporated into the models, stress peaks which are not mirrored in the profile of seismicity versus depth. Models with an asthenosphere and mesosphere of appropriate viscosity can not only explain the state of stress observed in double Benioff zones, but also yield stress magnitude profiles consistent with observed seismicity. Models where a nonlinear rheology is used are qualitatively consistent with the linear models. 相似文献
82.
The seismic hazard of Sannio-Matese is calculated using a new seismogenetic zoning of southern Italy of seven areas and different, azimuth-dependent, attenuation laws. Various approaches (Gumbel's first and third asymptotic distribution, Cornell) lead to similar results for the different exposure times considered (100 and 200 years) and probability levels (37 and 68%). The present seismic regulation proposed in 1980 by the Italian National Council for Researches, and based on a different approach, is, in general, confirmed by the results. 相似文献
83.
84.
85.
86.
87.
88.
British earthquakes 总被引:1,自引:0,他引:1
89.
江苏—南黄海地区城市密集,人口众多,是中国东部经济最发达的地带之一。同时,该地区历史上曾频发中—强以上级别的地震,地震及次生地质灾害是威胁该区经济社会发展的自然灾害之一。该区的地震活动时空特征和发震机制还不清楚。本文通过整理江苏—南黄海地区的历史和仪器记录地震数据,分析了该区地震活动时空分布格局,发现地震活动主要集中于若干条区域活动断裂带,在时间上具有约60年的平静期,目前仍处于地震活跃期。深部构造研究还表明该区域内地震活跃的南部坳陷和勿南沙隆起区均存在显著的地球物理异常,表明地震活动与区域深部构造有关。东部菲律宾海板块的俯冲作用和印度—欧亚大陆碰撞引起的板块边界挤压力和大陆边缘因地形高程差异伴随的重力势能是中国海洋地震的主要驱动力。上述认识不仅加深了对江苏—南黄海地区地震构造环境的理解,同时也能对该区防震减灾公益事业提供科学参考。 相似文献
90.
Dozens of >M5, hundreds of >M4, and much more >M3 aftershocks occurred after the 2008/05/12 Wenchuan earthquake, which were well recorded by permanent and portable seismic
stations. After relocated with P arrival, the >M3 aftershocks show two trends of distribution, with most of the aftershocks located along the north-east strike consistent
with Longmenshan fault system, yet there is a north-west trend around the epicenter. It seems that substantially more aftershocks
occur in regions with crystalline bedrocks. Then we collected waveform data from National Digital Seismograph Network and
regional seismograph network of China, and employed “Cut and Paste” method to obtain focal mechanisms and depths of the big
aftershocks (M⩾5.6). While most of those aftershocks show thrust mechanism, there are some strike slip earthquakes in the northern-most
end of the rupture. Focal mechanisms show that the events located on the southern part of central Beichuan-Yingxiu Fault (BY)
are mainly thrust earthquakes, which is consistent with initial mechanism of the main shock rupture. In the north part the
aftershocks along the BY are also dominated by thrust slip, which is quite different from the right slip rupture of the main
shock. Around Qingchuan-Pingwu Fault, the focal mechanisms are dominated by right-slip rupture with large depths (∼18 km).
So we suspected that in the north part the main shock might rupture on two faults: Beichuan Fault and Qingchuan-Pingwu Fault.
The complex pattern of aftershock mechanisms argues for presence of a complicated fault system in the Longmenshan area.
Supported by Knowledge Innovation Project of Chinese Academy of Sciences (Grant Nos. KZCX3-SW-153, KZCX2-YW-116-1), National
Natural Science Foundation of China (Grant No. 40604004), and National Basic Technology R & D Program (Grant No. 2006BAC01B02-01-02). 相似文献