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   1583651篇
  免费   153550篇
  国内免费   1527篇
  2021年   18158篇
  2019年   16254篇
  2018年   18958篇
  2017年   17724篇
  2016年   28982篇
  2015年   42933篇
  2014年   51022篇
  2013年   77222篇
  2012年   44189篇
  2011年   34936篇
  2010年   46404篇
  2009年   47001篇
  2008年   32438篇
  2007年   31108篇
  2006年   34666篇
  2005年   35733篇
  2004年   34535篇
  2003年   32107篇
  2002年   30129篇
  2001年   46477篇
  2000年   44288篇
  1999年   40887篇
  1998年   27064篇
  1997年   27132篇
  1996年   26251篇
  1995年   24503篇
  1994年   24187篇
  1993年   23565篇
  1992年   35607篇
  1991年   34192篇
  1990年   32526篇
  1989年   32934篇
  1988年   30488篇
  1987年   29223篇
  1986年   27586篇
  1985年   29348篇
  1984年   27558篇
  1983年   24291篇
  1982年   23211篇
  1981年   22009篇
  1980年   20751篇
  1979年   24048篇
  1978年   21541篇
  1977年   20455篇
  1976年   19474篇
  1975年   19491篇
  1974年   20465篇
  1973年   20599篇
  1972年   17908篇
  1971年   16382篇
排序方式: 共有10000条查询结果,搜索用时 292 毫秒
131.
132.
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   
133.
A finite element based method to determine the incremental elastic material properties of planar membranes was developed and evaluated. The method is applicable to tissues that exhibit inhomogeneity, geometric and material nonlinearity, and anisotropy. Markers are placed on the tissue to form a four-node quadrilateral element. The specimen is loaded to an initial reference state, then three incremental loading sets are applied and the nodal displacements recorded. One of these loadings must include shear. These data are used to solve an over-determined system of equations for the tangent stiffness matrix. The method was first verified using analytical data. Next, data obtained from a latex rubber sheet were used to evaluate experimental procedures. Finally, experiments conducted on preconditioned rat skin revealed nonlinear orthotropic behavior. The vector norm comparing the applied and calculated nodal force vectors was used to evaluate the accuracy of the solutions.  相似文献   
134.
135.
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   
136.
137.
138.
139.
140.
    
Ohne Zusammenfassung  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