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   5379篇
  免费   550篇
  国内免费   157篇
测绘学   236篇
大气科学   603篇
地球物理   1957篇
地质学   2193篇
海洋学   301篇
天文学   358篇
综合类   185篇
自然地理   253篇
  2023年   4篇
  2022年   6篇
  2021年   13篇
  2020年   6篇
  2019年   10篇
  2018年   436篇
  2017年   376篇
  2016年   257篇
  2015年   157篇
  2014年   118篇
  2013年   138篇
  2012年   656篇
  2011年   429篇
  2010年   122篇
  2009年   146篇
  2008年   128篇
  2007年   123篇
  2006年   143篇
  2005年   835篇
  2004年   874篇
  2003年   660篇
  2002年   175篇
  2001年   74篇
  2000年   45篇
  1999年   15篇
  1998年   11篇
  1997年   18篇
  1996年   12篇
  1995年   3篇
  1991年   13篇
  1990年   14篇
  1989年   6篇
  1987年   6篇
  1983年   2篇
  1981年   2篇
  1980年   3篇
  1978年   3篇
  1976年   3篇
  1975年   4篇
  1973年   2篇
  1969年   2篇
  1968年   2篇
  1965年   3篇
  1963年   2篇
  1961年   2篇
  1959年   2篇
  1955年   2篇
  1954年   2篇
  1951年   2篇
  1948年   2篇
排序方式: 共有6086条查询结果,搜索用时 15 毫秒
171.
Previous studies of weathering generally started with geochemistry[1—8] and mineralogy[9—12], and have been focused on chemical weathering rates[1—3], removability-enrichment of elements[3—6] during chemical weathering, and the age of weathering profi…  相似文献   
172.
Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Expedition. The results showed that 226Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m3 with an average of 0.76 Bq/m3 in the Arctic Ocean, and from 0.25 to 1.26 Bq/m3 with an average of 0.71 Bq/m3 in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that the study area may be partly influenced by sea ice meltwater. In the Bering Sea, 226Ra in the surface water decreased northward, probably as a result of the exchange between the 226Ra-deficient sea ice meltwater and the 226Ra-rich Pacific water. In the Arctic Ocean, 226Ra in the surface water increased northward and eastward. This spatial distribution of 226Ra reflected the variation of the 226Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of 226Ra in the Canadian Basin showed a concentration maximum at 200 m, which could be attributed to the inputs of the Pacific water or/and the bottom shelf water with high 226Ra concentration. This conclusion was consistent with the results from 2H, 18O tracers.  相似文献   
173.
Land surface temperature is a key parameter in monitoring the status of crop water stress by remote sensing, and studying the water and energy balance in cropland ecosystem. The component temperatures of crop and soil are especially significant in remote …  相似文献   
174.
In this paper, we report cosmic-ray exposure ages (3He, 21Ne, 38Ar) and gas retention ages (4He, 40Ar) of two Antarctic meteorites, and the Guangmingshan and Zhuanghe ordinary chondrites. The Antarctic meteorites (GRV98002 and GRV98004) were collected on …  相似文献   
175.
A candidate of the Induan-Olenekian boundary stratotype in the Tethyan region   总被引:10,自引:0,他引:10  
The Olenekian Stage was proposed by Kiparisova and Popov[1] based on the type section along the lower reaches of the Olenek River, Siberia. Later research showed that this section con-tains only the Olenikites spiniplicatus Zone of the Upper Olenekian Sta…  相似文献   
176.
Sea ice, as an important component of the Arctic climate system, has drawn significant sci-entific interest. Sea ice thickness and its morphology have dramatic impacts on ocean-atmos- phere-ice interactions[1—4], which directly affect the exchange proces…  相似文献   
177.
The influences of human activities on regional climate and weather are tremendous. The re-gional temperature and the distributing of wind field are influenced, whereas the precipitation in-tensity and the spatial and temporal distribution of the precipita…  相似文献   
178.
Basic characteristics of active tectonics of China   总被引:84,自引:8,他引:76  
Active tectonics is inferred to all the structures which have been active since the late Pleisto-cene, 100—120 ka B.P., are still active recently, and will be active in a certain time period in the future, such as active faults, active folds, active basi…  相似文献   
179.
To develop geosciences quantification and multi-dimensional researches will be an inevitable trend in the 21st century. The interaction between the land surface and the atmosphere not only serves as an important component in geosciences quantification, bu…  相似文献   
180.
When organic matter during geological processes is affected by a variety of factors such as paleotemperature, and time, complicated chemical reactions will occur, finally resulting in the generation of petroleum and natural gas. These reactions leading to…  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