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   424286篇
  免费   44174篇
  国内免费   199篇
  468659篇
  2016年   4603篇
  2015年   6076篇
  2014年   7200篇
  2013年   10774篇
  2012年   11704篇
  2011年   12171篇
  2010年   8268篇
  2009年   7598篇
  2008年   10839篇
  2007年   11510篇
  2006年   10838篇
  2005年   10316篇
  2004年   10368篇
  2003年   10162篇
  2002年   9967篇
  2001年   17494篇
  2000年   17511篇
  1999年   14153篇
  1998年   5038篇
  1997年   5329篇
  1996年   5059篇
  1995年   4770篇
  1994年   4687篇
  1993年   4661篇
  1992年   12349篇
  1991年   12157篇
  1990年   12154篇
  1989年   11951篇
  1988年   11235篇
  1987年   10585篇
  1986年   9889篇
  1985年   10311篇
  1984年   8496篇
  1983年   7326篇
  1982年   5663篇
  1981年   5061篇
  1980年   4733篇
  1979年   8131篇
  1978年   6336篇
  1977年   5980篇
  1976年   5709篇
  1975年   6169篇
  1974年   6742篇
  1973年   6613篇
  1972年   6174篇
  1971年   5558篇
  1970年   4803篇
  1969年   4817篇
  1968年   4488篇
  1967年   3835篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Fraternal twins, offspring of consanguineous parents, developed pancytopenia, the boy at 7, the girl at 12 years of age. A third patient became anemic at 3 years. All three are free of associated malformations. In blood cultures the incidence of chromatid breaks, exchanges, and chromosome-type aberrations was elevated to 24%, 18%, and 28%, respectively. In addition, in a low number of mitotic cells unusual observations, pointing to profound disturbances of chromosome structure, were made. It is suggested that these patients have a genetic defect impairing the normal process of mitotic chromosome condensation and decondensation.  相似文献   
992.
Phagocytic activity of leukocytes, as well as the complement, properdin, and lysozyme levels in the blood serum of miniature piglets, germfree and monocontaminated with E. coli 055 and E. coli 083, were studied. E. coli 055 phagocytosis was decreased in the presence of autologous serum and complement and increased under the effect of specific opsonins (antibodies to E. coli 055). Complement, properdin, and lysozyme levels were decreased in the germfree, in comparison with conventional animals. In the E. coli contaminated piglets properdin and complement production was stimulated most, and lysozyme formation--less. No antibodies to E. coli 055 were revealed in monocontaminated piglets. The highest lysozyme levels were found in the ex-germfree animals, this indicating the participation of factors other than E. coli contamination in lysozyme stimulation. It is concluded that microbial contamination played an important role in the development of cellular and humoral factors of the organism resistance.  相似文献   
993.
994.
995.
996.
997.
998.
In the genus Klebsiella, the growth respnse in nutient broth at 10 degrees C correlates inversely with the operational definition of a fecal coliform and not merely with the ability to grow at 44.5 degrees C. Of the fecal coliform-positive Klebsiella, 97% did not grow at 10 degrees C after 72 h of incubation. Conversely, 97% of the fecal coliform-negative isolates grew at 10 degrees C. The amount of growth at 10 degrees C varied among the fecal coliform-negative isolates and was found to correlate with indole production and pectin liquefaction. Low-temperature growth associated with specific biochemical tests can be used to differentiate several groups in the genus Klebsiella. Three main groups were discerned. Group I consists of indole-negative, pectin-nonliquefying, fecal coliform-positive isolates that do not grow at 10 degrees C. Group II isolates are differentiated from group I by a fecal-coliform-negative response and growth at 10 degrees C. Group III are indole-positive, pectin-liquefying, fecal coliform-negative isolates that grow at 10 degrees C. In our culture collection, isolates of group I are most frequently of human/animal clinical origins, whereas isolates of groups II and III are predominantly derived from the environment.  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