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   13461篇
  免费   141篇
  国内免费   92篇
测绘学   292篇
大气科学   837篇
地球物理   2565篇
地质学   5193篇
海洋学   1294篇
天文学   2840篇
综合类   65篇
自然地理   608篇
  2022年   152篇
  2021年   215篇
  2020年   213篇
  2019年   249篇
  2018年   558篇
  2017年   453篇
  2016年   508篇
  2015年   213篇
  2014年   450篇
  2013年   677篇
  2012年   510篇
  2011年   629篇
  2010年   645篇
  2009年   741篇
  2008年   657篇
  2007年   638篇
  2006年   551篇
  2005年   385篇
  2004年   365篇
  2003年   347篇
  2002年   325篇
  2001年   273篇
  2000年   297篇
  1999年   195篇
  1998年   204篇
  1997年   193篇
  1996年   137篇
  1995年   153篇
  1994年   143篇
  1993年   122篇
  1992年   94篇
  1991年   103篇
  1990年   118篇
  1989年   92篇
  1988年   105篇
  1987年   120篇
  1986年   100篇
  1985年   141篇
  1984年   127篇
  1983年   132篇
  1982年   108篇
  1981年   117篇
  1980年   121篇
  1979年   104篇
  1978年   102篇
  1977年   97篇
  1976年   73篇
  1975年   74篇
  1974年   90篇
  1973年   80篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
951.
952.
Hydrographic observations in the eastern Arabian Sea (EAS) during summer monsoon 2002 (during the first phase of the Arabian Sea Monsoon Experiment (ARMEX)) include two approximately fortnight-long CTD time series. A barrier layer was observed occasionally during the two time series. These ephemeral barrier layers were caused byin situ rainfall, and by advection of low-salinity (high-salinity) waters at the surface (below the surface mixed layer). These barrier layers were advected away from the source region by the West India Coastal Current and had no discernible effect on the sea surface temperature. The three high-salinity water masses, the Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), and Red Sea Water (RSW), and the Arabian Sea Salinity Minimum also exhibited intermittency: they appeared and disappeared during the time series. The concentration of the ASHSW, PGW, and RSW decreased equatorward, and that of the RSW also decreased offshore. The observations suggest that the RSW is advected equatorward along the continental slope off the Indian west coast.  相似文献   
953.
A numerical model is proposed to describe the formation of ice jams under the effect of a release wave.  相似文献   
954.
Cosmogenic-nuclide exposure ages for 13 glacially transported boulders atop the Martha's Vineyard moraine, MA, USA, indicate that the southeastern margin of the Laurentide ice sheet reached its maximum extent during the last glaciation 23,200±500 yr ago. Another 10 age determinations from the younger Buzzards Bay moraine near Woods Hole, MA, indicate that this moraine complex was formed 18,800±400 yr ago. These ages correlate approximately with the terminations of cooling cycles recorded in Greenland ice cores and coeval ice-rafting events, suggesting that the marginal position of this sector of the ice sheet was tightly coupled to North Atlantic climate during the last glacial maximum.  相似文献   
955.
Odemerho  Francis O. 《GeoJournal》1993,29(4):371-376
GeoJournal - Inspite of step-up efforts at controlling flood hazards in Third World cities, the frequency and magnitude of the flood problem have more than doubled in recent years. A survey of the...  相似文献   
956.
957.
958.
This study attempts regression/correlation analysis between maize yield and weather variables based on data analysed for the entire growing season and the different physiological stages of the crop's growth for Kabba in the wet sub-humid climate of Nigeria. The implications of the relationships obtained are examined for maize growth at the station.  相似文献   
959.
The potential gradient at ground level due to a charge volume is obtained in terms of integrals, some values of which are computed as functions of normalized vertical and horizontal distances. Using these values the vertical potential gradients at points on the ground below some simple cloud volumes, built up of cylindrical slices of uniform charge densities, are calculated. The results consitute definite improvements on those provided by conventional point-charge models.  相似文献   
960.
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