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   1289002篇
  免费   110929篇
  国内免费   1354篇
  2021年   17849篇
  2020年   13709篇
  2019年   17991篇
  2018年   19825篇
  2017年   18573篇
  2016年   29983篇
  2015年   43862篇
  2014年   51700篇
  2013年   78051篇
  2012年   34370篇
  2011年   22562篇
  2010年   44618篇
  2009年   45688篇
  2008年   21437篇
  2007年   19104篇
  2006年   24359篇
  2005年   25852篇
  2004年   24877篇
  2003年   22617篇
  2002年   20780篇
  2001年   29095篇
  2000年   26292篇
  1999年   27563篇
  1998年   24786篇
  1997年   24437篇
  1996年   24055篇
  1995年   22168篇
  1994年   21968篇
  1993年   21046篇
  1992年   24139篇
  1991年   22814篇
  1990年   21458篇
  1989年   22482篇
  1988年   20627篇
  1987年   19544篇
  1986年   18560篇
  1985年   20684篇
  1984年   20969篇
  1983年   18589篇
  1982年   19545篇
  1981年   18867篇
  1980年   17679篇
  1979年   16926篇
  1978年   16591篇
  1977年   15924篇
  1976年   15179篇
  1975年   14698篇
  1974年   15212篇
  1973年   15604篇
  1972年   13219篇
排序方式: 共有10000条查询结果,搜索用时 141 毫秒
51.
52.
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   
53.
54.
55.
56.
57.
The immunological analysis of 24 spontaneous Strr, Rifr and Kanr mutants of streptococcal strain IP, highly virulent for mice and capable of binding polyclonal human IgG (IgG FcR+), was made. The characteristic feature of all these mutants was decreased virulence, restored after their passage in vivo. 23 mutants were capable of binding polyclonal IgG; one Strr mutant had no such capacity, but acquired it, together with an increase in virulence, after its passage in vivo. When stored in meat-peptone agar without antibiotics, 5 out of 10 Strr mutants lost their capacity for binding polyclonal human IgG. After passage in vivo they regained this property simultaneously with virulence.  相似文献   
58.
59.
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   
60.
The results of the inoculation of material taken from the anterior section of the nasal cavity and from the pharyngeal mucosa of 50 healthy young children and 298 acute pneumonia patients were analyzed. 23 microbial species were isolated. In the samples taken from the anterior section of the nasal cavity, monocultures were detected in 86 samples and 54 variants of associations including 2-4 species, in 139 samples. In the samples taken from the pharynx, monocultures were detected in 59 samples and 180 variants of associations including 2-6 species, in 282 samples. Differences in the contamination of the nasal cavity and the pharynx in healthy children and in pneumonia patients were revealed. These differences were manifested in the structure of the microflora (monocultures, associations, their composition), the assortment of microbial species and their concentration. In young children with pneumonia the microflora of the upper respiratory tract was found to reflect the severity of acute pneumonia and the intensity of the pathological process in the lungs (uncomplicated, pyodestructive pneumonia, pyodestructive pneumonia with fatal termination, acute purulent pleurisy).  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