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   1790761篇
  免费   177508篇
  国内免费   1548篇
  2021年   18450篇
  2018年   19662篇
  2017年   18423篇
  2016年   29647篇
  2015年   43479篇
  2014年   51647篇
  2013年   77847篇
  2012年   50380篇
  2011年   42215篇
  2010年   48347篇
  2009年   48242篇
  2008年   38765篇
  2007年   38559篇
  2006年   40770篇
  2005年   41708篇
  2004年   40589篇
  2003年   37767篇
  2002年   35861篇
  2001年   58053篇
  2000年   56437篇
  1999年   49857篇
  1998年   28277篇
  1997年   28398篇
  1996年   27378篇
  1995年   25624篇
  1994年   25314篇
  1993年   24592篇
  1992年   43051篇
  1991年   41735篇
  1990年   40203篇
  1989年   40026篇
  1988年   37301篇
  1987年   35451篇
  1986年   33571篇
  1985年   35087篇
  1984年   31917篇
  1983年   28139篇
  1982年   25377篇
  1981年   24005篇
  1980年   22570篇
  1979年   28952篇
  1978年   25019篇
  1977年   23439篇
  1976年   22207篇
  1975年   23096篇
  1974年   24306篇
  1973年   24387篇
  1972年   21735篇
  1971年   19458篇
  1970年   17187篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Zooplankton data collected during September 1995 in the NorthWest Atlantic at 4139'N, 4958'W (the location of the siteof the ‘Titanic’ wreck) were analysed. The regioninvestigated was characterized by a very sharp frontal zonebetween the Gulf Stream and the main stream of the LabradorCurrent. The total plankton biomass in the water column wasvery high. The macroplankton biomass values below the 600 mlayer were significantly higher as compared with the similarvalues measured before in other productive boreal regions ofthe Atlantic and Pacific oceans. A lot of dead mesoplanktonanimals occurred in the deep layers. The reason was that thecold-water mesoplankton advected by the Labrador Current diedoff intensively within the deep layers of the frontal zone andwere used as a food resource by the macroplankton carnivoresand scavengers that were very abundant there.  相似文献   
152.
153.
Over the past 10 years the AIDS crisis has produced a large volume of writing. Much of this is documentary. Dozens of studies of AIDS from various clinical and political perspectives have been complemented by just as many published diaries, autobiographies, novels, plays, and poems. A few of these works have risen to the surface not only as extraordinarily valuable testimonies to the changes AIDS has wrought in individual and collective life but also as first-rate literary works, worth reading because beyond their immediate purposes they articulate with extraordinary lucidity and compassion some deep truths about the human--and the modern--condition. Paul Monette's Borrowed Time is among the most distinctive of those. It speaks not only for the community of people with AIDS and those who support them but for a generation.  相似文献   
154.
155.
156.
Reconstruction of bony structures of the face is always a problem as big as the defect and the function that must be replaced. Everything from simple grafts to sophisticated distant bone flaps has been used. Based on the studies of Cutting et al., Psillakis et al., and Casanova et al., we have developed the full-thickness galeoparietal bone flap, initially for mandibular reconstruction, but of great use for all maxillofacial reconstructions. From July of 1987 to December of 1988, 14 patients have been operated on. The experience with this flap is shown in four patients as follows: primary reconstruction of a mandible as a result of ameloblastoma, secondary reconstruction of a mandible with associated old fractures and malalignment of segments, bilateral malar reconstruction in a patient with Treacher Collins syndrome, and severe sequelae of an already treated Romberg case. Small variations could be made to best accommodate the technique used to the defect we were treating. Some technical details, the experience, the results, and possible sequelae or complications are also discussed.  相似文献   
157.
158.
159.
160.
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