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   792472篇
  免费   92204篇
  国内免费   433篇
  2018年   7044篇
  2016年   9743篇
  2015年   13617篇
  2014年   15703篇
  2013年   22017篇
  2012年   25134篇
  2011年   25723篇
  2010年   17329篇
  2009年   16034篇
  2008年   22901篇
  2007年   23793篇
  2006年   21991篇
  2005年   21351篇
  2004年   21115篇
  2003年   19975篇
  2002年   19412篇
  2001年   34204篇
  2000年   34203篇
  1999年   27514篇
  1998年   10150篇
  1997年   10490篇
  1996年   10061篇
  1995年   9255篇
  1994年   9193篇
  1993年   9100篇
  1992年   22523篇
  1991年   21906篇
  1990年   21413篇
  1989年   21015篇
  1988年   19455篇
  1987年   18756篇
  1986年   17331篇
  1985年   17131篇
  1984年   14448篇
  1983年   12498篇
  1982年   9768篇
  1981年   8789篇
  1980年   8381篇
  1979年   13793篇
  1978年   10767篇
  1977年   9940篇
  1976年   9452篇
  1975年   10039篇
  1974年   11133篇
  1973年   10875篇
  1972年   10027篇
  1971年   9194篇
  1970年   7889篇
  1969年   7807篇
  1968年   7197篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The effect of obesity on the connective tissue composition of skin was investigated in mice with goldthioglucose (GTG)-induced obesity. Four months after GTG treatment, the obese animals were sacrificed. Acid mucopolysaccharides, glycoproteins, collagen, and elastin were analyzed in the skin and compared to the controls. Total MPS in the skin from obese animals decreased, reflected mostly in hyaluronic acid. Chondroitin showed an increase over controls. The content of soluble glycoproteins varied; total carbohydrate and sialic acid of the glycoprotein tended to increase with obesity. Collagen and elastin both tended to decrease with obesity.  相似文献   
993.
994.
995.
996.
997.
The epithelium of the rim of the octopus sucker is the site of several different types of primary receptors. One is a non-ciliated cell with unusual characteristics. (1) The surface of the cell is extremely irregular with finger-like extensions of cytoplasm, especially far reaching in the basal region. (2) The slender neck contains a canal whose apical opening is in contact with the environment. This canal is lined with microvilli and contains granular material in an electron-dense matrix. (3) Patches of presumed glycogen granules occur throughout the cell, being especially abundant in the outer reaches of the cytoplasmic extensions. Their presence, together with numerous mitochondria and free ribosomes, indicate a high intrinsic metabolism. (4) Small fascicles of microtubules are randomly situated throughout the perikaryon. They gather into a coherent system of larger and larger bundles which ultimately enter the axon leading from the cell. This axon extends some distance in the basal region of the epithelium before crossing the subepithelial space to enter the infundibular muscle. Possible functions of this cell are discussed. On the basis of its specific position on the sucker and its intrinsic morphology we suggest that it is a mechanoreceptor involved in shape and/or negative pressure discrimination.  相似文献   
998.
Antigenic change on the surface of immature oocytes of Ascaris occurred during passage through the oviduct. Using immunodiffusion and immunoelectrophoretic techniques we examined the possible relationship between the antigenic change of immature oocytes and the junctional fluid (JF) which is present in the fertilization chamber. From the immunodiffusion it was found that the anti-immature oocyte serum (A-I serum) had more immunoprecipitation arcs than did the anti-mature oocyte serum (A-M serum) when reacted against the junctional fluid. This indicated that A-I serum contained more immunoglobulins that reacted with junctional fluid than did the A-M serum. This result was substantiated by using immunoelectrophoretic analysis and two dimension crossed immunoelectrophoresis. Our results suggest that during the migration toward the oviduct-uterine junction the immature oocytes might shed surface proteins into the luminal fluid. Alternatively, the membrane surface of mature oocytes may be altered by the interaction with the substances present in the junctional fluid.  相似文献   
999.
1000.
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