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   6808篇
  免费   127篇
  国内免费   2篇
  2023年   31篇
  2022年   22篇
  2021年   39篇
  2020年   68篇
  2019年   73篇
  2018年   208篇
  2017年   185篇
  2016年   287篇
  2015年   167篇
  2014年   108篇
  2013年   329篇
  2012年   388篇
  2011年   381篇
  2010年   99篇
  2009年   94篇
  2008年   127篇
  2007年   146篇
  2006年   120篇
  2005年   1398篇
  2004年   722篇
  2003年   513篇
  2002年   213篇
  2001年   76篇
  2000年   49篇
  1999年   65篇
  1998年   37篇
  1997年   24篇
  1996年   22篇
  1995年   20篇
  1994年   31篇
  1993年   25篇
  1992年   49篇
  1991年   52篇
  1990年   69篇
  1989年   53篇
  1988年   36篇
  1987年   58篇
  1986年   54篇
  1985年   39篇
  1984年   38篇
  1983年   32篇
  1979年   40篇
  1976年   20篇
  1975年   33篇
  1974年   36篇
  1973年   34篇
  1972年   27篇
  1971年   28篇
  1970年   19篇
  1969年   19篇
排序方式: 共有6937条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
Three forms related to different age groups are discussed. Special attention is devoted to laboratory analyses in support of clinical diagnosis. A representative sample of sera from the healthy population of Thuringia showed 6.97 per cent positive sera. The difference between the exposed agricultural and forestry workers and industrial workers is significant. Moreover, there is a relationship between the extent of wooded country and the presence of microfoci.  相似文献   
995.
996.
A large number of experiments in successive tests of episodic memory have focused on an experimental paradigm called recognition failure of recallable words. In this paradigm, a cued recall test follows a recognition test. Large amounts of data have revealed a lawful moderate dependence between recognition and cued recall. TECO (Sikstr?m, 1996b), a general connectionist theory of memory, has been applied for the phenomenon of recognition failure. This paper makes a strong claim that all possible pairwise combinations of successive tests between recognition, cued recognition, cued recall, and free recall follow a lawful relationship. The quantitative degree of the dependency predicted between these tests can be summarized in one function. Four experiments were conducted to test this claim. In line with the predictions, the results show that all pairwise combinations of these tests fit reasonably well with the proposed function. The TECO theory suggests theoretical insights into how recognition and recall may be divided into a recollection component, a familiarity component, and a cue-target integration component.  相似文献   
997.
998.
999.
1000.
Extended redundancy analysis (ERA) is used to reduce multiple sets of predictors to a smaller number of components and examine the effects of these components on a response variable. In various social and behavioural studies, auxiliary covariates (e.g., gender, ethnicity) can often lead to heterogeneous subgroups of observations, each of which involves distinctive relationships between predictor and response variables. ERA is currently unable to consider such covariate-dependent heterogeneity to examine whether the model parameters vary across subgroups differentiated by covariates. To address this issue, we combine ERA with model-based recursive partitioning in a single framework. This combined method, MOB-ERA, aims to partition observations into heterogeneous subgroups recursively based on a set of covariates while fitting a specified ERA model to data. Upon the completion of the partitioning procedure, one can easily examine the difference in the estimated ERA parameters across covariate-dependent subgroups. Moreover, it produces a tree diagram that aids in visualizing a hierarchy of partitioning covariates, as well as interpreting their interactions. In the analysis of public data concerning nicotine dependence among US adults, the method uncovered heterogeneous subgroups characterized by several sociodemographic covariates, each of which yielded different directional relationships between three predictor sets and nicotine dependence.  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