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   62786篇
  免费   722篇
  国内免费   376篇
测绘学   1583篇
大气科学   4444篇
地球物理   11444篇
地质学   24801篇
海洋学   5201篇
天文学   13071篇
综合类   213篇
自然地理   3127篇
  2021年   402篇
  2020年   402篇
  2019年   454篇
  2018年   3759篇
  2017年   3487篇
  2016年   2592篇
  2015年   724篇
  2014年   1030篇
  2013年   2075篇
  2012年   2152篇
  2011年   4167篇
  2010年   3885篇
  2009年   4418篇
  2008年   3564篇
  2007年   4247篇
  2006年   1629篇
  2005年   1777篇
  2004年   1614篇
  2003年   1665篇
  2002年   1434篇
  2001年   1078篇
  2000年   1017篇
  1999年   811篇
  1998年   812篇
  1997年   827篇
  1996年   667篇
  1995年   655篇
  1994年   615篇
  1993年   567篇
  1992年   525篇
  1991年   494篇
  1990年   505篇
  1989年   496篇
  1988年   473篇
  1987年   553篇
  1986年   488篇
  1985年   604篇
  1984年   649篇
  1983年   592篇
  1982年   527篇
  1981年   589篇
  1980年   488篇
  1979年   458篇
  1978年   433篇
  1977年   432篇
  1976年   386篇
  1975年   378篇
  1974年   376篇
  1973年   384篇
  1971年   224篇
排序方式: 共有10000条查询结果,搜索用时 225 毫秒
781.
The wavemaking capability and energy absorbing characteristics of a single submerged body, constrained to move horizontally in a surge mode, are examined. The body possesses both a vertical axis of symmetry and a horizontal plane of symmetry and is ‘thin’ in the sense that the body draft is small compared to the length. The behaviour of a single body subject to a constraint being placed upon the amplitude of its displacement and the properties of an array of interacting identical devices are also discussed.  相似文献   
782.
Three methods for the determination of dissolved organic carbon in seawater were compared. Samples were analysed using persulphate oxidation, high-temperature combustion, and ultraviolet photo-oxidation. The dissolved organic carbon content of the seawater samples ranged from 0.6 to 1.6 mg C/I. This study shows that results of high-temperature oxidation and photo-oxidation procedures differ by less than 5%, whereas results with persulphate oxidation are about 15% less than those obtained with the high-temperature oxidation. The relative merits of each of the oxidation techniques for the determination of organic matter in seawater are discussed.  相似文献   
783.
The decline of the herring stocks and the gadoid outburst   总被引:2,自引:1,他引:2  
  相似文献   
784.
785.
The drainage pattern in the northeast and central Tufts Abyssal Plain is described in detail. Satellite navigation on the systematic survey has allowed precise location of the major channel systems of the northeast Pacific Ocean. Two hundred channel profiles were collected from the echograms showing the Moresby-Scott, Mukluk, and Horizon Channel Systems trending in either a southwestward or westward direction across this section of the Tufts Plain. The channel profiles illustrate the prominence of the higher and wider right-hand levee (facing downstream). The Moresby-Scott Channel System disperses in the form of several distributaries throughout the area studied, and is probably responsible for much of the sediment deposits. Unlike the Moresby-Scott, the Mukluk extends throughout the survey area as a solitary channel with one minor branch. The Horizon Channel crosses the Sedna Fracture Zone east of the Sedna Seamount and terminates in distributary fashion in the central portion of the Tufts Plain. The Moresby-Scott, Mukluk, and Horizon Channels form one major system which encompasses the entire northeast and central Tufts Abyssal Plain.  相似文献   
786.
The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region.  相似文献   
787.
788.
789.
790.
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