首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1272篇
  免费   86篇
  国内免费   18篇
测绘学   62篇
大气科学   104篇
地球物理   327篇
地质学   363篇
海洋学   89篇
天文学   293篇
综合类   2篇
自然地理   136篇
  2023年   1篇
  2022年   1篇
  2021年   32篇
  2020年   31篇
  2019年   38篇
  2018年   51篇
  2017年   37篇
  2016年   47篇
  2015年   49篇
  2014年   48篇
  2013年   76篇
  2012年   61篇
  2011年   68篇
  2010年   54篇
  2009年   84篇
  2008年   66篇
  2007年   65篇
  2006年   75篇
  2005年   70篇
  2004年   67篇
  2003年   55篇
  2002年   52篇
  2001年   43篇
  2000年   27篇
  1999年   34篇
  1998年   31篇
  1997年   12篇
  1996年   11篇
  1995年   11篇
  1994年   11篇
  1993年   8篇
  1992年   4篇
  1991年   6篇
  1990年   1篇
  1989年   6篇
  1988年   6篇
  1987年   4篇
  1986年   6篇
  1985年   3篇
  1984年   4篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1978年   1篇
  1975年   1篇
排序方式: 共有1376条查询结果,搜索用时 15 毫秒
341.
342.
During the 1980s, New Zealand underwent a period of dramatic economic, social, and administrative restructuring. The reform extended to the administrative arrangements for environmental management. A geographic restructuring model is used in this paper to establish the context in which the reforms were carried out. A combination of economic, environmental, and social influences operating at different geographic scales can be identified. These influences are subsequently illustrated through reference to three aspects of the restructuring that have distinct geographical dimensions: the definition of human-environment relations, the spatial definition of planning regions, and the implications of spatial differentiation for resource management policy and practice.  相似文献   
343.
344.
The Olinghouse fault zone is one of several NE—ENE-trending fault zones and lineaments, including the Midas Trench and the Carson—Carson Sink Lineament, which exhibit left-lateral transcurrent movement conjugate to the Walker Lane in western Nevada. The active portion of this fault zone extends for approximately 23 km, from 16 km east of Reno, Nevada, to the southern extent of Pyramid Lake. The fault can be traced for most of its length from its geomorphic expression in the hilly terrain, and it is hidden only where overlain by recent alluvial sediments. Numerous features characteristic of strike-slip faulting can be observed along the fault, including: scarps, vegetation lines, sidehill and shutter ridges, sag ponds, offset stream channels and stone stripes, enclosed rhombohedral and wedge-shaped depressions, and en-echelon fractures.A shear zone having a maximum observable width of 1.3 km is defined principally by Riedel shears and their symmetrical P-shears, with secondary definition by deformed conjugate Riedel shears. Several continuous horizontal shears, or principal displacement shears, occupy the axial portion of the shear zone. The existence of P-shears and principal displacement shears suggests evolution of movement along the fault zone analogous to the “Post-Peak” or “Pre-Residual Structure” stage.Historic activity (1869) has established the seismic potential of this zone. Maximum intensities and plots of the isoseismals indicate the 1869 Olinghouse earthquake had a magnitude of 6.7. Field study indicates the active length of the fault zone is at least 23 km and the maximum 1869 displacement was 3.65 m of left-slip. From maximum fault length and maximum fault displacement to earthquake magnitude relations, this corresponds to an earthquake of about magnitude 7.  相似文献   
345.
346.
347.
348.
349.
Chris Lukinbeal 《GeoJournal》2004,59(4):307-321
During the later half of the 1980s through the mid 1990s the American film production industry experienced significant growth due to an increase in the production of television shows. Because of this growth, the economic geography of film production changed dramatically. I examine how the film production market has changed over the period 1984–1997, using a modified version of Storper and Christopherson's (1985) film market model of developed centers, second-order centers, edge-centers and occasional sites. I modify this model by including two new factors in the locational decision process: one, the effects of increased television production on the film market model; and two, the availability of different types of landscapes within regional film production centers.  相似文献   
350.
The influence of the structural pounding on the ductility requirements and the seismic behaviour of reinforced concrete structures designed to EC2 and EC8 with non‐equal heights is investigated. Special purpose elements of distributed plasticity are employed for the study of the columns. Two distinct types of the problem are identified: Type A, where collisions may occur only between storey masses; and Type B, where the slabs of the first structure hit the columns of the other (72 Type A and 36 Type B pounding cases are examined). Type A cases yielded critical ductility requirements for the columns in the pounding area mainly for the cases where the structures were in contact from the beginning of the excitation. In both pounding types the ductility requirements of the columns of the taller building are substantially increased for the floors above the highest contact storey level probably due to a whiplash behaviour. The most important issue in the pounding type B is the local response of the column of the tall structure that suffers the hit of the upper floor slab of the adjacent shorter structure. In all the examined cases this column was in a critical condition due to shear action and in the cases where the structures were in contact from the beginning of the excitation, this column was also critical due to high ductility demands. It can be summarized that in situations of potential pounding, neglecting its possible effects leads to non‐conservative building design or evaluation that may become critical in some cases. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号