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   748424篇
  免费   82383篇
  国内免费   562篇
  831369篇
  2018年   6866篇
  2017年   6632篇
  2016年   9252篇
  2015年   12016篇
  2014年   14155篇
  2013年   20854篇
  2012年   22923篇
  2011年   23493篇
  2010年   15894篇
  2009年   14592篇
  2008年   20869篇
  2007年   21486篇
  2006年   20261篇
  2005年   19468篇
  2004年   19254篇
  2003年   18437篇
  2002年   17824篇
  2001年   36163篇
  2000年   36176篇
  1999年   28347篇
  1998年   9340篇
  1997年   10081篇
  1996年   9406篇
  1995年   8611篇
  1994年   8356篇
  1993年   8392篇
  1992年   22850篇
  1991年   22162篇
  1990年   21325篇
  1989年   20830篇
  1988年   19150篇
  1987年   17962篇
  1986年   16740篇
  1985年   16716篇
  1984年   13687篇
  1983年   11566篇
  1982年   8758篇
  1981年   7956篇
  1980年   7523篇
  1979年   13005篇
  1978年   9963篇
  1977年   9370篇
  1976年   8505篇
  1975年   9405篇
  1974年   10265篇
  1973年   10009篇
  1972年   9121篇
  1971年   8384篇
  1970年   7318篇
  1969年   6971篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
1. High mol. wt kininogen (HMW kininogen) was purified to a homogeneous state from porcine plasma. 2. The protein exhibited a strong inhibitory activity for thiol proteinases such as ficin, papain and calpain I, whereas it did not inhibit serine proteinases, trypsin and chymotrypsin. 3. The mol. wt, isoelectric point, amino acid and carbohydrate compositions, stabilities to temperature and pH, kinetic constants, and immunological properties of the porcine HMW kininogen were determined and compared with those of human HMW kininogen.  相似文献   
22.
Female BALB/c mice were immunized with human melanoma (Mewo) cells containing ganglioside GD3 as a surface antigen. Immune splenocytes were fused with syngeneic P3-X63.Ag 8 myeloma cells. Antibodies produced by hybrid clones were analyzed by solid phase immunoassay. B, C, D and Q clones producing antibodies against Raja clavata brain gangliosides were obtained. Monoclonal B and C antibodies bound monosialogangliosides. Monoclonal D antibody bound a number of gangliosides but reacted predominantly with GD1a. Monoclonal Q antibody reacted selectively with GQ1c. It is assumed that ganglioside GQ1c is expressed on the melanoma cell surface and may be found only in the early stage of ontogenesis of high vertebrates.  相似文献   
23.
24.
L-lysine-alpha-oxidase, a new fungal enzyme catalyzing oxidative deamination of L-lysine, exerts an inhibitory effect on DNA, RNA and protein synthesis in human cells of carcinoma ovarius (CaOv) in vitro.  相似文献   
25.
S Yokota  H Tsuji  K Kato 《Histochemistry》1985,82(2):141-148
Light and electron microscopic localization of cathepsin D in rat liver was investigated by post-embedding immunoenzyme and protein A-gold techniques. By light microscopy, cytoplasmic granules of parenchymal cells and Kupffer cells were stained for cathepsin D. Weak staining was also noted in sinusoidal endothelial cells. In the parenchymal cells many of positive granules located around bile canaliculi. In the Kupffer cells and the endothelial cells, diffuse staining was noted in the cytoplasm in addition to granular staining. By electron microscopy, gold particles representing the antigenic sites for cathepsin D were seen in typical secondary lysosomes and some multivesicular bodies of the parenchymal cells and Kupffer cells. The lysosomes of the endothelial cells and fat-storing cells were weakly labeled. Quantitative analysis of the labeling density in the lysosomes of these three types of cells demonstrated that the lysosomes of parenchymal cells and Kupffer cells are main containers of cathepsin D in rat liver. The results suggest that cathepsin D functions in the intracellular digestive system of parenchymal cells and Kupffer cells but not so much in that of the endothelial cells.  相似文献   
26.
27.
1. Examination of the cerebrospinal fluid (CSF) of head-injured patients reveals that the concentration of intraventricular xanthine is elevated and that of uridine is decreased relative to those of adult lumbar CSF. 2. No correlations were observed between CSF lactate and CSF hypoxanthine, xanthine, or uridine, suggesting that changes in purine metabolites and the pyrimidine nucleoside do not index similar cellular events as does lactic acid production. 3. Ventricular CSF from hydrocephalic infants had uridine and hypoxanthine concentrations not significantly different from those of normal adult lumbar CSF, but xanthine was significantly elevated. 4. Since uridine has anticonvulsant properties and is a crucial substrate for cerebral metabolism, it may be useful to evaluate this pyrimidine for use in the management of patients with head injury.  相似文献   
28.
29.
30.
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