首页 | 官方网站   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   65603篇
  免费   5339篇
  国内免费   32篇
生物科学   70974篇
  2022年   436篇
  2021年   896篇
  2020年   562篇
  2019年   678篇
  2018年   882篇
  2017年   826篇
  2016年   1437篇
  2015年   2515篇
  2014年   2638篇
  2013年   3528篇
  2012年   4460篇
  2011年   4470篇
  2010年   2905篇
  2009年   2572篇
  2008年   3740篇
  2007年   3855篇
  2006年   3646篇
  2005年   3657篇
  2004年   3619篇
  2003年   3358篇
  2002年   3365篇
  2001年   821篇
  2000年   626篇
  1999年   816篇
  1998年   944篇
  1997年   669篇
  1996年   676篇
  1995年   658篇
  1994年   635篇
  1993年   672篇
  1992年   630篇
  1991年   529篇
  1990年   460篇
  1989年   476篇
  1988年   460篇
  1987年   402篇
  1986年   385篇
  1985年   458篇
  1984年   525篇
  1983年   430篇
  1982年   528篇
  1981年   464篇
  1980年   432篇
  1979年   292篇
  1978年   351篇
  1977年   335篇
  1976年   282篇
  1975年   260篇
  1974年   286篇
  1973年   260篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).  相似文献   
2.
3.
4.
5.
6.

Background  

The function and viability of cultured, transplanted, or encapsulated pancreatic islets is often limited by hypoxia because these islets have lost their vasculature during the isolation process and have to rely on gradient-driven passive diffusion, which cannot provide adequate oxygen transport. Pancreatic islets (islets of Langerhans) are particularly susceptible due to their relatively large size, large metabolic demand, and increased sensitivity to hypoxia. Here, finite element method (FEM) based multiphysics models are explored to describe oxygen transport and cell viability in avascular islets both in static and in moving culture media.  相似文献   
7.
8.
9.
10.
Are we able to infer what happened to a person from a brief sample of his/her behaviour? It has been proposed that mentalising skills can be used to retrodict as well as predict behaviour, that is, to determine what mental states of a target have already occurred. The current study aimed to develop a paradigm to explore these processes, which takes into account the intricacies of real-life situations in which reasoning about mental states, as embodied in behaviour, may be utilised. A novel task was devised which involved observing subtle and naturalistic reactions of others in order to determine the event that had previously taken place. Thirty-five participants viewed videos of real individuals reacting to the researcher behaving in one of four possible ways, and were asked to judge which of the four ‘scenarios’ they thought the individual was responding to. Their eye movements were recorded to establish the visual strategies used. Participants were able to deduce successfully from a small sample of behaviour which scenario had previously occurred. Surprisingly, looking at the eye region was associated with poorer identification of the scenarios, and eye movement strategy varied depending on the event experienced by the person in the video. This suggests people flexibly deploy their attention using a retrodictive mindreading process to infer events.  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-23

京公网安备 11010802026262号