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   2961篇
  免费   74篇
  国内免费   51篇
测绘学   302篇
大气科学   282篇
地球物理   525篇
地质学   1309篇
海洋学   140篇
天文学   415篇
综合类   55篇
自然地理   58篇
  2023年   16篇
  2022年   54篇
  2021年   60篇
  2020年   64篇
  2019年   67篇
  2018年   261篇
  2017年   235篇
  2016年   227篇
  2015年   135篇
  2014年   200篇
  2013年   261篇
  2012年   164篇
  2011年   164篇
  2010年   147篇
  2009年   144篇
  2008年   124篇
  2007年   86篇
  2006年   74篇
  2005年   54篇
  2004年   43篇
  2003年   37篇
  2002年   28篇
  2001年   23篇
  2000年   31篇
  1999年   20篇
  1998年   17篇
  1997年   22篇
  1996年   11篇
  1995年   11篇
  1994年   21篇
  1993年   15篇
  1992年   9篇
  1991年   28篇
  1990年   19篇
  1989年   24篇
  1988年   14篇
  1987年   22篇
  1986年   17篇
  1985年   16篇
  1984年   13篇
  1982年   6篇
  1981年   7篇
  1979年   13篇
  1978年   7篇
  1977年   6篇
  1976年   7篇
  1975年   8篇
  1974年   11篇
  1972年   8篇
  1969年   5篇
排序方式: 共有3086条查询结果,搜索用时 15 毫秒
111.
We have delineated different granitoids based on variation in emissivity and relative surface temperature recorded in thermal bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor of EO-1 satellite. In this regard, we have used emissivity normalization algorithm to derive broadband emissivity from thermal bands of ASTER sensor to delineate different lithounits of the granitoid family. We have compared emissivity and radiance image composites in terms of delineation of different granitoids. We have also used false colour composite (FCC) image derived using two emissivity bands and temperature (derived using emissivity normalisation method) bands to delineate different granitoids. We could differentiate different granitoids in the three-dimensional (3D) data space of ASTER-derived emissivity bands (second and third bands) and temperature bands. Based on the analysis of 3D scatter plot, we also proposed a ternary diagram of emissivity and temperature, which can be used to delineate different granitoids.  相似文献   
112.
The orbital and the rational polynomial coefficients (RPC) models are the two most commonly used models to compute a three-dimensional coordinates from an image stereo-pair. But it is still confusing that with the identical user provided inputs, which one of these two models provides more accurate digital elevation model (DEM), especially for mountainous terrain. This study aimed to find out the answer by evaluating the impact of used models on the vertical accuracy of DEM extracted from Cartosat-1 stereo data. We used high-accuracy photogrammetric DEM as the reference DEM. Apart from general variations in statistics, surprisingly in a few instances, both the DEMs provided contrasting results, thus proving the significance of this study. The computed root mean square errors and linear error at 90% (LE90) were lower in case of RPC DEM for various classes of slope, aspect and land cover, thus suggesting its better relative accuracy.  相似文献   
113.
114.
115.
116.
117.
118.
119.
120.
The present research work deals with an expansive high plastic clayey soil with cement kiln dust (CKD) and stabilizer (RBI Grade 81). The physical and engineering properties of soil are plasticity, compaction, unconfined compressive strength (UCS), consolidation and California bearing ratio (CBR) of the clayey soil and clay treated with CKD and stabilizer were determined. Soil chemistry was examined before and after treatment using scanning electron microscope (SEM) and elemental dispersive spectrometer. The clay mixed with CKD, CKD and RBI Grade 81 was found that optimum contents are 10 % (CKD), 15 % CKD with 4 % RBI Grade 81, respectively. The result indicates that CKD alone will decrease maximum dry density and increase optimum moisture content. CKD with RBI Grade 81 slightly increases maximum dry density and decreases optimum moisture content. UCS increased with CKD alone and CKD with RBI Grade 81 from 88.3 to 976 kN/m2, respectively. CBR values were increased by the addition of CKD, CKD with RBI Grade 81 from 1.65 to 21.7 %. With the curing time of 3, 14 and 28 days, UCS and CBR values were increased due to pozzolanic reaction from cementations material. The treated soil has considerable reduction in compression index. SEM images clearly indicate the formation of CSH and CAH gel.  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