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   8716篇
  免费   677篇
  国内免费   188篇
测绘学   362篇
大气科学   974篇
地球物理   2668篇
地质学   3277篇
海洋学   619篇
天文学   990篇
综合类   191篇
自然地理   500篇
  2023年   12篇
  2022年   21篇
  2021年   51篇
  2020年   55篇
  2019年   61篇
  2018年   518篇
  2017年   443篇
  2016年   379篇
  2015年   225篇
  2014年   220篇
  2013年   289篇
  2012年   780篇
  2011年   598篇
  2010年   273篇
  2009年   352篇
  2008年   313篇
  2007年   304篇
  2006年   284篇
  2005年   954篇
  2004年   990篇
  2003年   771篇
  2002年   297篇
  2001年   171篇
  2000年   142篇
  1999年   101篇
  1998年   104篇
  1997年   76篇
  1996年   77篇
  1995年   49篇
  1994年   33篇
  1993年   43篇
  1992年   34篇
  1991年   49篇
  1990年   34篇
  1989年   39篇
  1988年   15篇
  1987年   28篇
  1986年   17篇
  1985年   24篇
  1984年   35篇
  1983年   26篇
  1982年   17篇
  1981年   17篇
  1980年   19篇
  1979年   16篇
  1978年   18篇
  1977年   14篇
  1976年   18篇
  1975年   24篇
  1973年   15篇
排序方式: 共有9581条查询结果,搜索用时 15 毫秒
991.
The Litang fault zone (LFZ) is an important active fault within the northwestern Sichuan sub-block. To-gether with the Garzê-Yushu, Xianshuihe, and An-ninghe fault zones on its northern, eastern and south-eastern sides, the LFZ constitutes the lateral extrusion tectonic system in the southeastern part of the Qing-hai-Tibetan Plateau[1,2] (Fig. 1). According to instru-mental records, historical recordings and field investi- gation, an earthquake (Ms7.3) occurred on its middle to south se…  相似文献   
992.
993.
The deterioration of air quality is threatening the life and health of people. Scientists in China and other countries have done a great deal of research work on the details of air pollution and the methods of preven-tion and control during the past decades. Up to now, most of the achievements are concentrated on the techniques of controlling pollutant sources and the programs of reduction, which focus on the improve-ment of air quality and the restoration of environment. The techniques of con…  相似文献   
994.
Earthquake is a disaster event resulting from rapid and intensive crustal vibration caused by fault activity, volcanic eruption, or block dilapidation. Heezen and Ewing[1] and Heezen and Dyke[2] were the first to note earthquake-related mass movement and associated deposits in connection to the turbidity currents and submarine slumps triggered by the Grand Bank Earthquake in 1929. Seilacher[3] defined redeposited sedimentary beds, disturbed and modified by earth- quakes, as seismite. Since t…  相似文献   
995.
The Dabie Mountain is the collisional orogenic belt between the North China Block and the Yangtze Block. As the eastern segment of the central-China orogenic belt, its tectonic framework is corresponding to the Qinling orogenic belt as a whole[1]. The NHB in northern part of Dabie Orogen is regarded as the joint belt between the Yangtze Block and the North China Block, and roughly corresponds to the north Qinling belt of the Qinling orogenic belt, which separated the Tongbai-Dabie hig…  相似文献   
996.
In recent years, the Red Clay deposits underlying Quaternary loess on the Chinese Loess Plateau (north China) have attracted more attention because they show a direct and continuous record of past atmos- pheric circulation and palaeoclimatic change. Investiga- tions on Red Clay deposits through multidisciplinary methods have demonstrated an aeolian origin for the Red Clay, like the overlying Quaternary loess. The Red Clay formed during the Miocene and Pliocene[1―13]. However, the type o…  相似文献   
997.
The importance of calcimicrobes and microbialite in carbonate platform and reefal environments has been stressed in recent literature. Burne and Moore[1] introduced the term microbialite to describe the clotted, laminated and undifferentiated fabrics formed by mi-crobial communities. Microbialites are organosedi-mentary deposits that have accreted as a result of ben-thic (prokaryotic or eukaryotic) communities, trapping and binding detrital sediment[1]. Microbial organisms and microbialite are…  相似文献   
998.
Mesozoic and Cenozoic volcanic rocks are widely distributed in the circum-Pacific area of eastern China. These rocks have long been genetically linked to westward subduction of the paleo-Pacific oceanic plate to the eastern Asia continent[1,2]. Research in re-cent years[3―6] has attained conclusions that a simple paleo-Pacific subduction model does not work well in interpreting all the volcanic rocks in eastern China, although some of them could be attributed to circum-Pacific interaction …  相似文献   
999.
The South China, including Yangzi Craton and the Cathaysian Block, belongs to the southern part of East Asia continent. It borders Pacific plate on the east side and Qinling-Dabie Orogen on the north side. During the middle-late Cretaceous, a number of downfaulted red basins (the terrestrial sedimentary basins in Fig. 1) and volcanic- sedimentary basins had been developed in South China[1,2], in which the con-temporaneous basaltic rocks were generally distributed (Fig. 1). Although the …  相似文献   
1000.
The main portion of the inner radiation belt en-countered by spacecraft in low-Earth orbits (LEOs) is concentrated over the South Atlantic Anomaly (SAA) where satellites observed the highest particle flux. The anomaly arises from the Earth’s magnetic field being less intense in the region centered near the east of the Atlantic coast of South America. The trapped radiation belt particles therefore have their lowest mirroring altitudes over the center region of the SAA. Drift shells in t…  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