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   46957篇
  免费   8645篇
  国内免费   8422篇
测绘学   3600篇
大气科学   4864篇
地球物理   16974篇
地质学   21409篇
海洋学   4198篇
天文学   3926篇
综合类   3183篇
自然地理   5870篇
  2024年   275篇
  2023年   772篇
  2022年   1547篇
  2021年   1913篇
  2020年   1721篇
  2019年   2065篇
  2018年   1598篇
  2017年   1818篇
  2016年   1721篇
  2015年   2044篇
  2014年   2568篇
  2013年   2548篇
  2012年   2681篇
  2011年   2842篇
  2010年   2522篇
  2009年   3286篇
  2008年   2964篇
  2007年   3118篇
  2006年   3040篇
  2005年   2900篇
  2004年   2573篇
  2003年   2448篇
  2002年   2106篇
  2001年   1864篇
  2000年   1854篇
  1999年   1598篇
  1998年   1432篇
  1997年   1096篇
  1996年   982篇
  1995年   858篇
  1994年   795篇
  1993年   638篇
  1992年   484篇
  1991年   376篇
  1990年   265篇
  1989年   207篇
  1988年   168篇
  1987年   95篇
  1986年   55篇
  1985年   39篇
  1984年   22篇
  1983年   18篇
  1982年   11篇
  1981年   9篇
  1980年   8篇
  1979年   18篇
  1978年   15篇
  1977年   6篇
  1976年   4篇
  1954年   12篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
93.
In the article the author looks back the hard development course and great progress in earth quake science and technology in China during the last near a half of century and expounds the following 3 aspects: (1) The strong desire of the whole society to mitigate seismic disasters and reduce the effect of earthquakes on social-economic live is a great driving force to push forward the development of earthquake science and technology in China; (2) To better ensure people‘ s life and property, sustainable economic development, and social stability is an essential purpose to drive the development of earthquake science and technology in China; and (3) To insist on the dialectical connection of setup of technical system for seismic monitoring with the scientific research of earthquakes and to better handle the relation between crucial task, current scientif ic level, and the feasibility are the important principles to advance the earthquake science and technology in China. Some success and many setbacks in earthquake disaster mitigation consistently enrich our knowledge regarding the complexity of the conditions for earthquake occurrence and the process of earthquake preparation, promote the reconstruction and modernization of technical system for earthquake monitoring, and deepen the scientific research of earthquakes. During the last 5 years, the improvement and modernization of technical system for earthquake monitoring have clearly provided the technical support to study and practice of earthquake prediction and pre caution, give prominence to key problems and broaden the field of scientific research of earth quakes. These have enabled us to get some new recognition of the conditions for earthquake oc currence and process of earthquake preparation, characteristics of seismic disaster, and mecha nism for earthquake generation in China‘s continent. The progress we have made not only en courages us to enhance the effectiveness of earthquake disaster mitigation, but also provides a basis for accelerating further development of earthquake science and technology in China in the new century, especially in the 10th five-year plan. Based on the history reviewed, the author sets forth a general requirement for develop ment of earthquake science and technology in China and brings out 10 aspects to be stressed and strengthened at present and in the future. These are: upgrade and setup of the network of digitized seismic observation; upgrade and setup of the network for observation of seismic pre cursors; setup of the network for observation of strong motion; setup of the laboratories for ex periment on seismic regime; establishment of technical system for seismic information, emer gency command and urgent rescue; research on short-term and imminent earthquake predic tion; research on intermediate- and long-term earthquake prediction; research on attenuation of seismic ground motion, mechanism for seismic disaster, and control on seismic disaster; ba sic research fields related to seismology and geoscience. We expect that these efforts will signifi cantly elevate the level of earthquake science and technology in China to the advanced interna tional level, improve theories, techniques, and methods for earthquake precaution and predic tion, and enhance the effectiveness of earthquake disaster mitigation.  相似文献   
94.
95.
We investigate the morphological relation between the orbits of the central family of periodic orbits ( x 1 family) and the bar itself using models of test particles moving in a barred potential. We show that different bar morphologies may have as a backbone the same set of x 1 periodic orbits. We point out that by populating initially axisymmetric stellar discs exponentially with test particles in circular, or almost circular motion, we may end up with a response bar which reveals a shape different in crucial details from that of the individual stable x 1 orbits. For example, a bar model in which the x 1 orbits are pure ellipses may have a much more complicated response morphology. This depends on the particular invariant curves around x 1, which are populated in each model.  相似文献   
96.
97.
国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程.其总控系统下共包括8个既相互独立又互有关联的子系统.如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转,以及如何确保软件开发的可维护性、可持续性是研究重点.  相似文献   
98.
99.
100.
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