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   10514篇
  免费   52篇
  国内免费   13篇
教育   7201篇
科学研究   1095篇
各国文化   109篇
体育   1053篇
综合类   6篇
文化理论   101篇
信息传播   1014篇
  2021年   85篇
  2020年   163篇
  2019年   236篇
  2018年   261篇
  2017年   286篇
  2016年   249篇
  2015年   169篇
  2014年   238篇
  2013年   1917篇
  2012年   224篇
  2011年   219篇
  2010年   191篇
  2009年   176篇
  2008年   196篇
  2007年   221篇
  2006年   191篇
  2005年   177篇
  2004年   166篇
  2003年   185篇
  2002年   166篇
  2001年   182篇
  2000年   173篇
  1999年   175篇
  1998年   84篇
  1997年   84篇
  1996年   129篇
  1995年   91篇
  1994年   116篇
  1993年   105篇
  1992年   179篇
  1991年   166篇
  1990年   150篇
  1989年   154篇
  1988年   132篇
  1987年   126篇
  1986年   149篇
  1985年   142篇
  1984年   120篇
  1983年   134篇
  1982年   121篇
  1981年   107篇
  1980年   97篇
  1979年   174篇
  1978年   116篇
  1977年   120篇
  1976年   110篇
  1975年   82篇
  1974年   96篇
  1972年   70篇
  1971年   72篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
    
In this paper a variety of optimal control (OC) problems for distributed- parameter (DP) systems are approached using mathematical programming (MP). First, the principal DP models in current use are given, a variety of DP objective functions is provided, and the OC problems based on them are formulated. Second, these models and objective functions are converted in algebraic form, as required by MP, and the solution procedure of the OC problems via MP is outlined. Third, a representative set of nonlinear programming results applied to DP systems is presented, and finally, a numvber of application examples is given.  相似文献   
72.
    
Research in the area of technology learning environments is tremendously complex. Tasks performed in these contexts are highly cognitive and mostly invisible to the observer. The nature of performance in these contexts is explained not only by the outcome but also by the process. However, evaluating the learning process with respect to tasks involving technology is difficult to measure objectively. As a result, audit trails (also called log or dribble files) are becoming extremely valuable tools in evaluating learning and performance in complex environments. This article reviews efforts of researchers in various areas, describes the nature of research using dribble files, and provides a framework on which investigators might build evaluations.  相似文献   
73.
    
  相似文献   
74.
    
As part of a longitudinal twin study of literacy and language, we conducted a behaviour‐genetic analysis of orthographic learning, spelling and decoding in Grade 2 children (225 identical and 214 fraternal twin pairs) in the United States and Australia. Each variable showed significant genetic and unique environment influences. Multivariate analyses revealed very high genetic correlations among the variables, indicating that the same genes are involved in their aetiology. These genes are partly independent of those contributing to intelligence. A further analysis indicated that the covariation between decoding and orthographic learning is mediated by shared genes rather than by a direct causal path. The authors argue that a learning parameter, most directly assessed by orthographic learning in this study, underlies all three literacy variables. The results are also discussed in relation to Share's self‐teaching hypothesis, which may require modification.  相似文献   
75.
Leon IG 《Child development》2002,73(2):652-663
The American definition of kinship based on biological ties, the practice of closed adoption, and stigmas associated with adoption may decisively influence adoption-related losses. Cross-cultural and historical accounts of adoption that do not apply to these contemporary American constructs of parenthood and practices of adoption suggest outcomes that are not as integrally based on loss. Adoption in infancy is defined as parenting a child with one set of (adoptive) parents and two (adoptive and birth) families. Implications for adoption research, policy, and practice are discussed.  相似文献   
76.
    
This study evaluated a 2‐week residential program aimed at enhancing the science interest and persistence of high‐achieving 8th‐grade girls. Questionnaires were administered to 38 program participants (14 of whom were of minority ethnicity) and 173 applicants who did not attend the program, at 3 time points: preprogram, 1 year postprogram, and 4 years postprogram. Outcomes, measured postprogram, included science self‐concept and interest, persistence and aspirations in science, science activities, science course‐taking in high school, and plans for a science college major. There was no main effect of program participation on any of the outcome measures, but a significant Participation × Ethnicity interaction effect occurred for all but one of the outcome variables. At Time 2, and especially Time 3, nonminority participants tended to have the most positive outcomes, whereas minority participants tended to have the most negative outcomes, compared with applicants. Post hoc analyses showed that although nonminority girls overall were more advantaged, this difference did not explain results. Several interpretations for these findings are discussed, the most likely that some global feature of the program, not any intervention component, interacted over time with the girls' postprogram experience. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 393–414, 2003  相似文献   
77.
This study evaluated the feasibility of using students' self reports of the academic development and college experiences as proxies and policy indicators for a national assessment of undergraduate education. Results indicated that self reports of academic development should be used with care as proxies for a national test. Particularly important are issues of content overlap and differences in the measurement methods. Results from the second part of this study supported using self reports of college experiences as policy indicators to improve undergraduate education.Paper presented at the annual forum of the Association for Institutional Research, New Orleans, May 1995.  相似文献   
78.
A Twin Study of Attachment in Preschool Children   总被引:3,自引:0,他引:3  
The degree to which individual differences in child-parent attachment were mediated by genetic, shared environmental, and nonshared environmental influences was investigated. One hundred and ten preschool-aged twin pairs (N = 220) were assessed in the Strange Situation and coded using conventional four-way classifications and a continuous measure of attachment security. The degree of sibling similarity in attachment was substantial, with an overall concordance rate of 67% at the secure/insecure level. The degree of concordance was equally high in monozygotic and dizygotic twin pairs, 70% and 64%, respectively, suggesting little genetic influence but a moderate degree of discordance. Twin similarity on the continuous measure of attachment security was r(57) = .48 and r(53) = .38 for monozygotic and dizygotic twin pairs, respectively, also consistent with a modest role for genetic influence but a significant effect for shared and nonshared environment. The implications for genetic influences on the environment and for understanding nonshared and shared environmental influences are discussed.  相似文献   
79.
The semantic differential technique was used in this study for the purpose of discovering similarities and differences in the meaning of words between teachers in training and counselors in training. A number of differences were revealed which indicate that teachers in training and counselors in training are not in accord as to the connotations of certain concepts. These differences suggest that counselors and counselor educators must strive for a greater understanding of the counselor's role in the school setting on the part of other education professionals.  相似文献   
80.
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