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   803977篇
  免费   86855篇
  国内免费   450篇
  2018年   11293篇
  2017年   10969篇
  2016年   11652篇
  2015年   11775篇
  2014年   13558篇
  2013年   20052篇
  2012年   23710篇
  2011年   28163篇
  2010年   20009篇
  2009年   18538篇
  2008年   24530篇
  2007年   26731篇
  2006年   19623篇
  2005年   19659篇
  2004年   19101篇
  2003年   18933篇
  2002年   18409篇
  2001年   32675篇
  2000年   32972篇
  1999年   26217篇
  1998年   9436篇
  1997年   10198篇
  1996年   9608篇
  1995年   9052篇
  1994年   8814篇
  1993年   9028篇
  1992年   22721篇
  1991年   22473篇
  1990年   21918篇
  1989年   21639篇
  1988年   20052篇
  1987年   19147篇
  1986年   17852篇
  1985年   18305篇
  1984年   15274篇
  1983年   13190篇
  1982年   10206篇
  1981年   9103篇
  1980年   8675篇
  1979年   14606篇
  1978年   11468篇
  1977年   10675篇
  1976年   10176篇
  1975年   11074篇
  1974年   11809篇
  1973年   11664篇
  1972年   11146篇
  1971年   10144篇
  1970年   8335篇
  1969年   8143篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
72.
The paper presents data on a change in lysozyme content in tissues of spleen, liver and heart in fry of the Lena River sturgeon exposed to the presence of sublethal concentrations of Hg2+, Cd2+, and Cu2+ under conditions of chronic experiment. It has been shown that the lysozyme content in fish tissues varies and has a phasic character. The amplitude of fluctuations of this parameter depends on the moment of sampling, nature of the toxicant, and structural-functional organization of the studied organs.  相似文献   
73.
Replication of the flavivirus Kunjin virus is associated with virus-induced membrane structures within the cytoplasm of infected cells; these membranes appear as packets of vesicles associated with the sites of viral RNA synthesis and as convoluted membranes (CM) and paracrystalline arrays (PC) containing the components of the virus-specified protease (E. G. Westaway, J. M. Mackenzie, M. T. Kenney, M. K. Jones, and A. A. Khromykh, J. Virol. 71:6650-6661, 1997). To determine the cellular origins of these membrane structures, we compared the immunolabelling patterns of several cell markers in relation to these sites by immunofluorescence and immunoelectron microscopy. A marker for the trans-Golgi membranes and the trans-Golgi network, 1,4-galactosyltransferase (GalT), was redistributed to large foci in the cytoplasm of Kunjin virus-infected cells, partially coincident with immunofluorescent foci associated with the putative sites of viral RNA synthesis. As determined by immunoelectron microscopy, the induced vesicle packets contained GalT, whereas the CM and PC contained a specific protein marker for the intermediate compartment (ERGIC53). A further indicator of the role of cellular organelles in their biogenesis was the observation that the Golgi apparatus-disrupting agent brefeldin A prevented further development of immunofluorescent foci of induced membranes if added before the end of the latent period but that once formed, these membrane foci were resistant to brefeldin A dispersion. Reticulum membranes emanating from the induced CM and PC were also labelled with the rough endoplasmic reticulum marker anti-protein disulfide isomerase and were obviously redistributed during infection. This is the first report identifying trans-Golgi membranes and the intermediate compartment as the apparent sources of the flavivirus-induced membranes involved in events of replication.  相似文献   
74.
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   
75.
76.
Argon laser surgery is an effective treatment for ectasias and congenital port-wine stains; however, its use in children under the age of 13 is controversial. This paper reviews 202 children under the age of 13 who underwent argon laser treatments for congenital port-wine stains, spider angiomas, epidermal nevi, and lentigines. The clinical characteristics of port-wine stains in 170 children are discussed. Good to excellent results (moderate to complete clearing) in port-wine stains were obtained in 60 percent of patients and seemed to correlate best with lack of blanchability on pressure. Hypertrophic scarring was seen in only 7 children, all of whom had undressed wounds; no significant scarring has been seen in any subsequent child who had maintained a dressed wound postoperatively.  相似文献   
77.
78.
79.
80.
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