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   1226340篇
  免费   99061篇
  国内免费   1354篇
  1326755篇
  2021年   17619篇
  2020年   12528篇
  2019年   16088篇
  2018年   17439篇
  2017年   16250篇
  2016年   27779篇
  2015年   41889篇
  2014年   49861篇
  2013年   76068篇
  2012年   31813篇
  2011年   19562篇
  2010年   42412篇
  2009年   44155篇
  2008年   19221篇
  2007年   16935篇
  2006年   22708篇
  2005年   24117篇
  2004年   23295篇
  2003年   21054篇
  2002年   19295篇
  2001年   25941篇
  2000年   23205篇
  1999年   25298篇
  1998年   24452篇
  1997年   24140篇
  1996年   23802篇
  1995年   21933篇
  1994年   21754篇
  1993年   20813篇
  1992年   22477篇
  1991年   21181篇
  1990年   19805篇
  1989年   21004篇
  1988年   19244篇
  1987年   18200篇
  1986年   17306篇
  1985年   19471篇
  1984年   20096篇
  1983年   17826篇
  1982年   19097篇
  1981年   18502篇
  1980年   17323篇
  1979年   15985篇
  1978年   15882篇
  1977年   15308篇
  1976年   14579篇
  1975年   13948篇
  1974年   14353篇
  1973年   14753篇
  1972年   12436篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
45.
46.
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   
47.
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   
48.
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   
49.
50.
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