全文获取类型
收费全文 | 17750篇 |
免费 | 285篇 |
国内免费 | 55篇 |
专业分类
教育 | 13265篇 |
科学研究 | 1168篇 |
各国文化 | 186篇 |
体育 | 1239篇 |
综合类 | 44篇 |
文化理论 | 93篇 |
信息传播 | 2095篇 |
出版年
2021年 | 190篇 |
2020年 | 250篇 |
2019年 | 381篇 |
2018年 | 541篇 |
2017年 | 567篇 |
2016年 | 533篇 |
2015年 | 349篇 |
2014年 | 491篇 |
2013年 | 3664篇 |
2012年 | 501篇 |
2011年 | 513篇 |
2010年 | 453篇 |
2009年 | 442篇 |
2008年 | 453篇 |
2007年 | 431篇 |
2006年 | 460篇 |
2005年 | 401篇 |
2004年 | 285篇 |
2003年 | 274篇 |
2002年 | 265篇 |
2001年 | 389篇 |
2000年 | 319篇 |
1999年 | 275篇 |
1998年 | 178篇 |
1997年 | 173篇 |
1996年 | 185篇 |
1995年 | 163篇 |
1994年 | 157篇 |
1993年 | 136篇 |
1992年 | 218篇 |
1991年 | 206篇 |
1990年 | 252篇 |
1989年 | 221篇 |
1988年 | 177篇 |
1987年 | 184篇 |
1986年 | 186篇 |
1985年 | 181篇 |
1984年 | 176篇 |
1983年 | 159篇 |
1982年 | 130篇 |
1981年 | 146篇 |
1980年 | 125篇 |
1979年 | 182篇 |
1978年 | 151篇 |
1977年 | 115篇 |
1976年 | 117篇 |
1975年 | 108篇 |
1974年 | 101篇 |
1973年 | 102篇 |
1971年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Early childhood is a sensitive period for learning and social skill development. The maturation of cerebral regions underlying social processing lays the foundation for later social-emotional competence. This study explored myelin changes in social brain regions and their association with changes in parent-rated social-emotional development in a cohort of 129 children (64 females, 0–36 months, 77 White). Results reveal a steep increase in myelination throughout the social brain in the first 3 years of life that is significantly associated with social-emotional development scores. These findings add knowledge to the emerging picture of social brain development by describing neural underpinnings of human social behavior. They can contribute to identifying age-/stage-appropriate early life factors in this developmental domain. 相似文献
2.
David Sánchez-Oliva Rebecca M. Leech Alberto Grao-Cruces Irene Esteban-Cornejo Carmen Padilla-Moledo Oscar L. Veiga 《Journal of sports sciences》2020,38(9):1062-1069
ABSTRACTThe aims of this study were to identify profiles of sedentary behaviour (SB) patterns, based on leisure-time self-reported SB modalities (screen, educative, social, and relaxing) and to evaluate changes in these profiles over 2 years among Spanish youth aged 8–18 years. Latent profile analysis (LPA), a data-driven analytic approach, was used to identify groups of boys and girls (n = 1553; 48% girls; mean±SD age: 12.56 ± 2.49 y) with distinct SB profiles using the SB modalities (time/d) as input variables. Latent transition analysis, an extension of LPA that uses longitudinal data, was used to analyse 2-year changes in these profiles. At baseline, four and three SB profiles were found among boys (labelled: screen, educative, social, and relaxing) and girls (labelled: screen/social, educative, and relaxing), respectively. Overall, more girls (range: 48%-67%) had the same profile over time, than boys (40%-52%). Participants with a screen or relaxing SB profile at baseline were more likely to have an educative profile after 2 years. Youth with a social and an educative SB profile at baseline were more likely to transition to profiles characterized by higher screen and social SB, respectively. Using a novel and person-centered approach, this study identified gender-specific SB profiles that were moderately stable over time. 相似文献
3.
4.
5.
In this digital ITEMS module, Dr. Jeffrey Harring and Ms. Tessa Johnson introduce the linear mixed effects (LME) model as a flexible general framework for simultaneously modeling continuous repeated measures data with a scientifically defensible function that adequately summarizes both individual change as well as the average response. The module begins with a nontechnical overview of longitudinal data analyses drawing distinctions with cross-sectional analyses in terms of research questions to be addressed. Nuances of longitudinal designs, timing of measurements, and the real possibility of missing data are then discussed. The three interconnected components of the LME model—(1) a model for individual and mean response profiles, (2) a model to characterize the covariation among the time-specific residuals, and (3) a set of models that summarize the extent that individual coefficients vary—are discussed in the context of the set of activities comprising an analysis. Finally, they demonstrate how to estimate the linear mixed effects model within an open-source environment (R). The digital module contains sample R code, diagnostic quiz questions, hands-on activities in R, curated resources, and a glossary. 相似文献
6.
在美国 ,科技编辑是一个逐渐被认可的领域。美国的科技编辑们在什么环境下工作 ?他们做什么 ?有什么样的教育背景 ?用什么样的体例手册和其他资源 ?有什么组织为他们服务 ?他们对哪些话题和事件有职业兴趣 ?文章描述了美国科技编辑的概况 ,着重说明上面这些问题。本文的写作在很大程度上依赖于我为科技编辑委员会的期刊《科技编辑》做编辑的经验。本文中 ,“科学”具有广泛的含义 ,包括医学及其相关领域。的确 ,在美国许多科技编辑是医学编辑。 工作环境和工作类型在美国 ,有各种各样的媒体雇佣科技编辑 ,这些媒体包括杂志、图书、大众… 相似文献
7.
8.
9.
10.