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   3958篇
  免费   234篇
  4192篇
  2024年   6篇
  2023年   58篇
  2022年   73篇
  2021年   98篇
  2020年   143篇
  2019年   140篇
  2018年   229篇
  2017年   226篇
  2016年   206篇
  2015年   115篇
  2014年   140篇
  2013年   513篇
  2012年   293篇
  2011年   291篇
  2010年   188篇
  2009年   91篇
  2008年   247篇
  2007年   197篇
  2006年   183篇
  2005年   113篇
  2004年   85篇
  2003年   93篇
  2002年   67篇
  2001年   31篇
  2000年   53篇
  1999年   28篇
  1998年   22篇
  1997年   16篇
  1996年   13篇
  1995年   9篇
  1994年   14篇
  1993年   14篇
  1992年   10篇
  1991年   23篇
  1990年   11篇
  1989年   14篇
  1988年   12篇
  1987年   10篇
  1986年   7篇
  1985年   13篇
  1984年   7篇
  1983年   7篇
  1981年   7篇
  1980年   5篇
  1979年   5篇
  1972年   5篇
  1971年   6篇
  1968年   9篇
  1966年   7篇
  1965年   9篇
排序方式: 共有4192条查询结果,搜索用时 15 毫秒
71.
Animal Cognition - Across mammals, increased body size is positively associated with lifespan. However, within species, this relationship is inverted. This is well illustrated in dogs (Canis...  相似文献   
72.
Attention, Perception, & Psychophysics - Learning and imitating a complex motor action requires to visually follow complex movements, but conscious perception seems too slow for such tasks....  相似文献   
73.
74.
75.
76.
77.
78.
The purposes of the present study were threefold: (a) to assess the prevalence levels of anxiety and depression in a sample of Mexican migrant farm workers in the midwestern United States; (b) to explore the relationships among acculturative stress, anxiety, and depression; and (c) to examine the variables that best predict anxiety and depression. The overall sample revealed elevated levels of anxiety and depression. Migrant farm workers with heightened levels of acculturative stress were more likely to report high levels of anxiety and depression. Family dysfunction, ineffective social support, low self-esteem, lack of agreement with the decision to migrate, high education levels, high levels of acculturative stress, and high levels of anxiety were significantly associated with high depression levels. The overall findings suggest that migrant farm workers who experience elevated levels of acculturative stress may be at risk for experiencing high levels of anxiety and depression. The findings highlight the importance of establishing prevention and treatment services for migrant farm workers that aim to increase levels of emotional support, self-esteem, and coping skills.  相似文献   
79.
This work analyzed the effects of unrealistic optimism in the interaction between the emotional valence of future events, the perception of control over these events, and the person with whom one compares oneself. It was hypothesized that, if the person of comparison is judged as very competent, a pessimistic bias should be produced. Likelihood of four different types of events (positive and controllable, positive and uncontrollable, negative and controllable, and negative and uncontrollable) were rated by 133 university students (22 men and 111 women) for themselves, for an average student, for their best friend, and for a bright friend. A pessimistic bias was observed on the relative likelihood of the events when the comparison was made between oneself and a competent and bright friend, when events were perceived as controllable, especially positive ones. Not enough is known, however, to provide meaningful interpretation at present; that must await further data and theoretical development.  相似文献   
80.
Gutiérrez  G.  de Guzmán  I. P.  Martínez  J.  Ojeda-Aciego  M.  Valverde  A. 《Studia Logica》2002,72(1):85-112
The tree-based data structure of -tree for propositional formulas is introduced in an improved and optimised form. The -trees allow a compact representation for negation normal forms as well as for a number of reduction strategies in order to consider only those occurrences of literals which are relevant for the satisfiability of the input formula. These reduction strategies are divided into two subsets (meaning- and satisfiability-preserving transformations) and can be used to decrease the size of a negation normal form A at (at most) quadratic cost. The reduction strategies are aimed at decreasing the number of required branchings and, therefore, these strategies allow to limit the size of the search space for the SAT problem.  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