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   18363篇
  免费   1396篇
  国内免费   1篇
  19760篇
  2021年   138篇
  2020年   122篇
  2019年   125篇
  2018年   282篇
  2017年   246篇
  2016年   437篇
  2015年   759篇
  2014年   705篇
  2013年   1036篇
  2012年   1245篇
  2011年   1226篇
  2010年   733篇
  2009年   601篇
  2008年   1097篇
  2007年   1087篇
  2006年   1054篇
  2005年   992篇
  2004年   940篇
  2003年   858篇
  2002年   812篇
  2001年   413篇
  2000年   415篇
  1999年   371篇
  1998年   183篇
  1997年   165篇
  1996年   138篇
  1995年   157篇
  1994年   137篇
  1993年   103篇
  1992年   229篇
  1991年   232篇
  1990年   210篇
  1989年   164篇
  1988年   175篇
  1987年   146篇
  1986年   142篇
  1985年   126篇
  1984年   114篇
  1983年   97篇
  1982年   94篇
  1981年   118篇
  1980年   74篇
  1979年   110篇
  1978年   103篇
  1977年   82篇
  1976年   96篇
  1975年   80篇
  1974年   90篇
  1973年   79篇
  1971年   80篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Forty-two patients were followed up after 44 renal transplantations in an effort to evaluate possible benefits from the following protocol: systematic microbiologic and clinical surveillance, early and aggressive research for the cause of suspected infections, refusal to use prophylactic antibiotherapy, and selection of treatment according to the established cause of the infection. During 18,030 days of follow-up 124 infections were recorded, of which 110 were bacterial, 11 viral and 3 protozoal. Eighty originated in the urinary tract, 17 in skin wounds and 10 in the lower respiratory tract. Septicemia occurred three times, and one death due to infection was recorded. In the treatment of bacterial infections patients received antibiotics for 2486 days. Ampicillin (given for 816 days) and "minor" drugs such as sulfonamides and urinary antiseptics (given for 1036 days) were used 74.5% of the time, whereas gentamicin was used only 2.6% of the time (64 days). Combined antibacterial therapy was needed 1.2% of the time (29 days). A restrictive policy regarding anti-biotherapy seems to be beneficial to renal transplant recipients.  相似文献   
83.
84.
Two glycoproteins characterized by their serological activities (HLA-A9 and HLA-B12), their isoelectric points and their molecular weights were purified from urine from a patient suffering from tubular proteinuria (cystinosis). Their physicochemical properties as well as an important increase of their specific activities during the different purification steps suggested that they behave as human leucocyte antigens (HLA) which had been excreted into urine. Their amino acid compositions and N-terminal sequences were different to those described for HLA solubilized from cultured human lymphoblast cell lines. The N-terminal sequences of the two serologically active glycoproteins were identical to the N-terminal sequence of another recently purified human urinary glycoprotein called human complex-forming glycoprotein. The relationship between HLA, human complex-forming glycoprotein and the serologically active urinary glycoproteins is discussed.  相似文献   
85.
The secondary structures of cow and sheep kappa-caseins were established according to the predictive rules of Chou and Fasman. The diagrams derived from this treatment allowed us to study the chymosin sensitive bond (milk-clotting process), as well as the glycosylation and phosphorylation sites, found to be situated in beta-turns. Despite a high variability between the primary structures of the COOH-terminal part (caseinoglycopeptide) of cow, sheep, and also other caseins, the secondary structures of the biologically important sites were found to be conserved.  相似文献   
86.
The exocellular DD -carboxypeptidase–transpeptidase that Streptomyces R61 excretes during growth has been produced in large fermentation units of 15 m3 total capacity. The yield from 15,000 liter culture filtrate was 1.080 g purified enzyme (92% purity) with a total recovery of 29% and at least a 2000-fold increased specific activity.  相似文献   
87.
88.
The NADH: nitrate reductase from durum wheat leaves was inactivated by cyanide and its activity restored by thiosulphate and beef kidney rhodanese. Rhodanese and thiosulphate, added to NADH-nitrate reductase before cyanide treatment protected NADH-nitrate reductase activity. No oxidizing agent was required for the protection or restoration of cyanide treated NADH-nitrate reductase.  相似文献   
89.
VO2 max, maximum oxygen uptake, has been measured in 4 normal young men, before and after beta-adrenergic blockade (0.5 to 5 mg Pindolol by mouth). Pindolol induces bradycardia and reduces VO2 max. A statistically significant positive correlation appears between posology of Pindolol and bradycardia, this posology and reduction of VO2 max, and finally between bradycardia and reduction of VO2 max. These correlations indicate that the reduction of VO2 max is best explained by a circulatory limitation of oxygen supply to active muscles.  相似文献   
90.
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