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   35131篇
  免费   5969篇
  国内免费   7327篇
测绘学   3346篇
大气科学   4453篇
地球物理   6119篇
地质学   19038篇
海洋学   3959篇
天文学   3363篇
综合类   2339篇
自然地理   5810篇
  2024年   117篇
  2023年   430篇
  2022年   1177篇
  2021年   1355篇
  2020年   1258篇
  2019年   1461篇
  2018年   1130篇
  2017年   1333篇
  2016年   1385篇
  2015年   1567篇
  2014年   1968篇
  2013年   1990篇
  2012年   2092篇
  2011年   2229篇
  2010年   1928篇
  2009年   2432篇
  2008年   2389篇
  2007年   2454篇
  2006年   2391篇
  2005年   2278篇
  2004年   1991篇
  2003年   1907篇
  2002年   1623篇
  2001年   1455篇
  2000年   1439篇
  1999年   1285篇
  1998年   1102篇
  1997年   786篇
  1996年   633篇
  1995年   549篇
  1994年   525篇
  1993年   451篇
  1992年   314篇
  1991年   275篇
  1990年   183篇
  1989年   148篇
  1988年   125篇
  1987年   71篇
  1986年   39篇
  1985年   34篇
  1984年   20篇
  1983年   12篇
  1982年   14篇
  1981年   8篇
  1980年   12篇
  1979年   5篇
  1978年   16篇
  1977年   5篇
  1976年   4篇
  1954年   7篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
103.
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   
104.
105.
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   
106.
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   
107.
108.
109.
We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able to account for an observed mismatch between theoretical predictions and observations of the coolest Hyades MS stars. Finally, we show that current theoretical models probably give too faint He burning luminosities unlike the case of less massive He burning models, with degenerate progenitors, which have been suggested to suffer the opposite discrepancy.  相似文献   
110.
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