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   975528篇
  免费   110263篇
  国内免费   593篇
  2019年   9228篇
  2018年   12619篇
  2017年   12154篇
  2016年   15762篇
  2015年   19482篇
  2014年   22293篇
  2013年   30949篇
  2012年   32722篇
  2011年   33228篇
  2010年   24372篇
  2009年   21376篇
  2008年   28900篇
  2007年   29494篇
  2006年   27835篇
  2005年   26765篇
  2004年   26743篇
  2003年   25603篇
  2002年   24930篇
  2001年   43820篇
  2000年   43807篇
  1999年   34722篇
  1998年   12054篇
  1997年   12378篇
  1996年   11614篇
  1995年   10866篇
  1994年   10567篇
  1993年   10320篇
  1992年   28139篇
  1991年   27555篇
  1990年   26958篇
  1989年   26299篇
  1988年   24467篇
  1987年   22872篇
  1986年   21189篇
  1985年   21266篇
  1984年   17513篇
  1983年   14633篇
  1982年   10924篇
  1981年   9673篇
  1980年   9173篇
  1979年   15810篇
  1978年   12305篇
  1977年   11139篇
  1976年   10221篇
  1975年   11565篇
  1974年   12365篇
  1973年   12270篇
  1972年   10968篇
  1971年   10110篇
  1970年   8589篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Hostile intercommunity relations, including attacking and killing extra-community infants of both sexes have occurred at most wild chimpanzee sites. We describe three recent cases of intercommunity attacks on infants committed by members of the Ngogo chimpanzee community in Kibale National Park, Uganda. Two of the attacks resulted in confirmed infanticides while a third attack probably resulted in the infant's death. In common with previous accounts of chimpanzee infanticides, the attacks described here occurred during boundary patrols outside the Ngogo community's usual range, adult and adolescent males were the main participants, one infant was cannibalized after being killed, and the victims’ mothers did not accompany the attacking party back to the Ngogo range. However, the patrol parties during each infanticide were larger than before and included females from the Ngogo community. Our observations indirectly support both the range expansion and imbalance of power hypotheses, which address why and under which conditions chimpanzee intercommunity encounters lead to aggression. These cases of intercommunity infanticide add to the growing database of the phenomenon in wild chimpanzees.  相似文献   
72.
73.
74.
75.
76.
Four myeloid cell lines (M1, WEHI-3B D+, FDC-P1, and 32D) were screened for the presence of J11d antigen. One of these cell lines, the myeloid leukemia M1, was found to express a high level of J11d antigen on the cell surface. Recombinant mouse leukemic inhibitory factor (rm-LIF), recombinant human LIF (rh-LIF), and steroids (hydrocortisone and dexamethasone) could induce M1 cells to undergo monocytic differentiation. The level of J11d antigen was greatly reduced after treatment of the cells with LIF or steroids. Western blotting revealed that the apparent molecular weight of the J11d antigen on M1 cells was 45-48 kDa. Furthermore, the level of J11d mRNA was also reduced during LIF-induced differentiation of M1 cells.  相似文献   
77.
78.
79.
80.
The paper presents data on a change in lysozyme content in tissues of spleen, liver and heart in fry of the Lena River sturgeon exposed to the presence of sublethal concentrations of Hg2+, Cd2+, and Cu2+ under conditions of chronic experiment. It has been shown that the lysozyme content in fish tissues varies and has a phasic character. The amplitude of fluctuations of this parameter depends on the moment of sampling, nature of the toxicant, and structural-functional organization of the studied organs.  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