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   920篇
  免费   16篇
  国内免费   12篇
测绘学   29篇
大气科学   62篇
地球物理   174篇
地质学   399篇
海洋学   61篇
天文学   127篇
综合类   3篇
自然地理   93篇
  2021年   9篇
  2020年   10篇
  2019年   11篇
  2018年   14篇
  2017年   24篇
  2016年   17篇
  2015年   19篇
  2014年   16篇
  2013年   27篇
  2012年   23篇
  2011年   28篇
  2010年   33篇
  2009年   32篇
  2008年   40篇
  2007年   33篇
  2006年   34篇
  2005年   21篇
  2004年   29篇
  2003年   26篇
  2002年   31篇
  2001年   26篇
  2000年   26篇
  1999年   25篇
  1998年   16篇
  1997年   13篇
  1996年   13篇
  1995年   12篇
  1994年   10篇
  1993年   8篇
  1992年   11篇
  1991年   8篇
  1990年   10篇
  1989年   14篇
  1988年   11篇
  1987年   10篇
  1986年   11篇
  1985年   13篇
  1984年   17篇
  1983年   21篇
  1982年   14篇
  1981年   16篇
  1980年   10篇
  1979年   8篇
  1978年   10篇
  1977年   7篇
  1975年   9篇
  1973年   8篇
  1971年   10篇
  1970年   9篇
  1875年   7篇
排序方式: 共有948条查询结果,搜索用时 11 毫秒
101.
Evidence for threshold gradients is reviewed. The consolidation problem, with threshold gradient, is properly formulated and solved numerically. An approximate analytical solution is also developed. The influence of a threshold gradient on the time rate of settlement is examined, and it is shown that by modifying the definition of the degree of consolidation a good approximation to the threshold gradient problem can be obtained directly from the Terzaghi solution. It is also shown that threshold gradients will have no influence on odometer testing and their effect is, therefore, to reduce the primary compression below that predicted from standard tests.  相似文献   
102.
103.
The examination of nearly 9600 archival photographic plates covering six gamma-ray burst error boxes has unveiled several star-like images. Unfortunately, the reality of none of these images can be proved by duplicate plates.A laboratory test was performed to get a more detailed estimation of the number of plate faults. The result emphasizes the necessity of duplicate synchronous plates to exclude plate defects.  相似文献   
104.
Bos  Randall J.  Hill  Henry A. 《Solar physics》1983,82(1-2):89-102
Solar Physics - New observations of solar oscillations are reported. Power density spectra derived from these observations reveal narrow-band oscillations that are spatially global, have spatial...  相似文献   
105.
106.
Several stratospheric chemistry modules from box, 2-D or 3-D models, have been intercompared. The intercomparison was focused on the ozone loss and associated reactive species under the conditions found in the cold, wintertime Arctic and Antarctic vortices. Comparisons of both gas phase and heterogeneous chemistry modules show excellent agreement between the models under constrained conditions for photolysis and the microphysics of polar stratospheric clouds. While the mean integral ozone loss ranges from 4–80% for different 30–50 days long air parcel trajectories, the mean scatter of model results around these values is only about ±1.5%. In a case study, where the models employed their standard photolysis and microphysical schemes, the variation around the mean percentage ozone loss increases to about ±7%. This increased scatter of model results is mainly due to the different treatment of the PSC microphysics and heterogeneous chemistry in the models, whereby the most unrealistic assumptions about PSC processes consequently lead to the least representative ozone chemistry. Furthermore, for this case study the model results for the ozone mixing ratios at different altitudes were compared with a measured ozone profile to investigate the extent to which models reproduce the stratospheric ozone losses. It was found that mainly in the height range of strong ozone depletion all models underestimate the ozone loss by about a factor of two. This finding corroborates earlier studies and implies a general deficiency in our understanding of the stratospheric ozone loss chemistry rather than a specific problem related to a particular model simulation.  相似文献   
107.
108.
109.
楊偉聰  刘逸 《地理研究》2021,40(12):3253-3258
进入21世纪以来,全球生产网络(Global Production Net-work,GPN)研究非常深刻地展现了 Peter Dicken所描绘的"全球-地方矛盾".这个概念由Dicken在1994年发表于《Economic Geography》上的Roepke Lecture特邀文章中首次提出[1].作为过去20多年经济地理学的一个主要学术支柱,GPN研究经历了两个重要的理论发展阶段,即从早期的广泛而一般的GPN框架2-4]过渡到更加具备解释性的GPN 2.0理论[5-7].在GPN研究理论快速发展的这个时期里,Coe等首先提出了"战略耦合"这一关键而新颖的概念[4],并由Yeung对其进行了完善[8-10].  相似文献   
110.
The rare calc‐silicate minerals cuspidine, bultfonteinite, foshagite and xonotlite occur in a calcsilicate skarn zone near Chesney Vale, in northern Victoria. They are associated with andradite-grossular garnet, vesuvianite, diopside, wollastonite, prehnite, epidote, fluorite, calcite, perovskite,sphene and possibly tobermorite. The calc‐silicate skarn zone has formed in thermally meta‐morphosed, Ordovician, deep‐marine sediments adjacent to an Early Devonian aplitic granite pluton. The assemblages are estimated to have formed at low pressure (<100 MPa) at temperaturesnot exceeding 600°C in the presence of a low‐Xco2 fluorine‐bearing fluid. The occurrence is the firstrecord of bultfonteinite and foshagite in Australia and the first record of cuspidine and xonotlite inVictoria.  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