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   37370篇
  免费   255篇
  国内免费   219篇
测绘学   739篇
大气科学   1730篇
地球物理   7080篇
地质学   14715篇
海洋学   3530篇
天文学   8846篇
综合类   102篇
自然地理   1102篇
  2022年   488篇
  2021年   712篇
  2020年   756篇
  2019年   828篇
  2018年   1702篇
  2017年   1551篇
  2016年   1645篇
  2015年   620篇
  2014年   1423篇
  2013年   2051篇
  2012年   1624篇
  2011年   1908篇
  2010年   1795篇
  2009年   2002篇
  2008年   1769篇
  2007年   1983篇
  2006年   1745篇
  2005年   903篇
  2004年   819篇
  2003年   815篇
  2002年   747篇
  2001年   767篇
  2000年   638篇
  1999年   423篇
  1998年   443篇
  1997年   476篇
  1996年   342篇
  1995年   359篇
  1994年   341篇
  1993年   290篇
  1992年   286篇
  1991年   299篇
  1990年   340篇
  1989年   274篇
  1988年   260篇
  1987年   260篇
  1986年   192篇
  1985年   303篇
  1984年   306篇
  1983年   296篇
  1982年   276篇
  1981年   250篇
  1980年   269篇
  1979年   203篇
  1978年   243篇
  1977年   205篇
  1976年   177篇
  1975年   184篇
  1974年   171篇
  1973年   206篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
This study considers the influence of the effects of scattering due to Langmuir turbulent pulsations in the transfer of radiation in the spectral lines. The transfer equation of radiation in spectral lines, by taking into account scattering due to Langmuir turbulent pulsations, is written in a form convenient for application by numerical methods.The profile's intensity for a plane-parallel finite isothermal slab of a turbulent plasma in the case of complete redistribution of scattering by an atom are obtained. Numerical studies show that in this case with the broadening of spectral lines and the decreasing of self-reversal, the Langmuir frequency pe is of the same order as the electronic Doppler width De. Creation of the line satellites when pe is larger than the line width is shown with the aid of numerical methods.  相似文献   
33.
The laboratory simulation experiments on volatilization from the melts formed due to micrometeoroid impacts on the lunar surface were carried out. The simulation was performed using modulated laser pulses incident on rocks and minerals in vacuum; in so doing microcraters on the targets, glass particles, condensates were formed and gases solved in the bulk of the rock and mineral grains were released. It is shown that volatilization from only the crater glass layers is negligible, which fully confirms the theoretical predictions of Nussinov and Chernyak.The volatilizations from the drops formed by the micrometeoric impacts can be noticeable. For micron-sized drops, predominant among the others after the impact, the volatilization of Na, K and other volatiles can be up to 10 to 20%. For larger-sized (d102 m) drops the volatilization should lead to the appearance of the significant gradients of the element concentrations over the particle cross-section and as a result of their normalization it leads to the surface enrichment by some elements (Si and others).The mechanism of dust formation due to the surface rocks attack by volatilizing alkaline metals (Naughtonet al.) on the Moon probably is not effective. It is the consequence of such a fact that the condensate of the target materials evaporated due to other simultaneous micrometeoric impacts and had the same (as the target has) elemental composition is the very strong background for volatilizing and condensating alkaline elements.Preliminary conclusions about a possible correlation between the composition and the sizes of dust particles in the Solar system and in the Universe (at similar initial composition) have been drawn.  相似文献   
34.
35.
36.
37.
38.
39.
Lithology and Mineral Resources - The chemical composition and Nd isotope systematics were obtained for mudrocks (mudstones) from sections of the Siberian hypostratotype of the Riphean and Vendian...  相似文献   
40.
The Cone-in-Cone Structure and Its Origin   总被引:1,自引:0,他引:1  
Morphostructural investigation of carbonate cone-in-cone formations allows to conclude that they belong to self-organizing (dissipative, according to I. Prigogine's terminology) systems of the geological past formed in a thermogradient field at the expense of energy of heat and mass transfer (Prigogine and Stengers, 1984). First, the fluid-convective metasomatic hypothesis unites and reconciles the most well-known hypotheses that previously seemed to be incompatible and transforms them to rather consistent particular cases of a more intricate multistage geological phenomenon. Second, it helps to identify the morphologically and genetically analogous noncarbonate structures that mimic biogenic ones. The probable indicative role of cone-in-cone structure in the mapping of fluid-conducting systems is a consequence of the proposed hypothesis.  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