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   28817篇
  免费   467篇
  国内免费   229篇
测绘学   610篇
大气科学   2230篇
地球物理   5797篇
地质学   10478篇
海洋学   2273篇
天文学   6302篇
综合类   71篇
自然地理   1752篇
  2021年   161篇
  2020年   197篇
  2019年   209篇
  2018年   848篇
  2017年   809篇
  2016年   688篇
  2015年   516篇
  2014年   692篇
  2013年   1231篇
  2012年   893篇
  2011年   1116篇
  2010年   886篇
  2009年   1231篇
  2008年   1080篇
  2007年   1065篇
  2006年   993篇
  2005年   1298篇
  2004年   1494篇
  2003年   1225篇
  2002年   774篇
  2001年   690篇
  2000年   636篇
  1999年   571篇
  1998年   577篇
  1997年   576篇
  1996年   440篇
  1995年   419篇
  1994年   380篇
  1993年   335篇
  1992年   311篇
  1991年   276篇
  1990年   304篇
  1989年   281篇
  1988年   235篇
  1987年   311篇
  1986年   257篇
  1985年   346篇
  1984年   384篇
  1983年   371篇
  1982年   335篇
  1981年   310篇
  1980年   312篇
  1979年   282篇
  1978年   311篇
  1977年   263篇
  1976年   267篇
  1975年   275篇
  1974年   234篇
  1973年   238篇
  1972年   158篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
26.
Conclusion The above account is just a selection of Perthes' multifarious activities. As such it is fragmentary and incomplete. Many other publications and collaborators could have been mentioned. Even in its incompleteness the report may justify the statement that the success of Justus Perthes Geographische Verlagsanstalt, was apart from the managing qualities of its governors, undoubtedly due to the long series of scholarly competent collaborators whom they succeeded in engaging. As illustrated above most of theme were among the avant garde of the profession. Apparently they were at ease with Justus Perthes where they were granted enough freedom of action to realise their ambitious projects under the vigilant eye of the management. In fact the history of the firm is a continuous story of their achievements. Their combined effort initiated modern scientific atlas-making, laid down the foundation of methodic school cartography and accelerated the growth of thematic cartography. The Justus Perthes maps and atlasses stand for intellectual honestly and have an authoritative appearance of truth and exactness. For a long time to come the name of the firm will be considered as a classical example of the promotion of geography and cartography by private enterprise.  相似文献   
27.
28.
Two single-sensor piezometer probes, 8 mm in diameter, were developed for deep-ocean geotechnical investigations. These probes were tested in a hyperbaric chamber pressurized to 55 MPa (8000 psi). Testing was performed for a period of five weeks under high hydrostatic pressure with the probes inserted in reconstituted illitic marine sediment. Small differential pore-water pressures were generated in response to both mechanically and thermally generated forcing functions. During deep-ocean simulated pressure tests, the sensors exhibited excellent sensitivity and stability. These developments in piezometer-probe technology provide a quantitative means of assessing important geotechnical parameters of fine-grained seabed deposits.  相似文献   
29.
30.
The light curve modeling of binary stars has continued to evolve since its founding by Henry Norris Russell (see Russell and Merrill 1952 and citations therein) nearly a century ago, accelerated in the 1950s by Kopal's introduction of Roche geometry into models and by the development of synthetic light curve computer code in the 1970's. Improved physics and the use of more kinds of observational input are providing another round of important advances that promise to enlarge our knowledge of both binary stars and ensembles containing them. Here we discuss the newer horizons of light curve modeling and the steps being taken toward them.  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