全文获取类型
| 收费全文 | 20459篇 |
| 免费 | 161篇 |
| 国内免费 | 8篇 |
专业分类
| 教育 | 15458篇 |
| 科学研究 | 1718篇 |
| 各国文化 | 177篇 |
| 体育 | 1118篇 |
| 综合类 | 3篇 |
| 文化理论 | 506篇 |
| 信息传播 | 1648篇 |
出版年
| 2022年 | 57篇 |
| 2021年 | 92篇 |
| 2020年 | 166篇 |
| 2019年 | 248篇 |
| 2018年 | 2439篇 |
| 2017年 | 2362篇 |
| 2016年 | 1847篇 |
| 2015年 | 342篇 |
| 2014年 | 377篇 |
| 2013年 | 2118篇 |
| 2012年 | 465篇 |
| 2011年 | 930篇 |
| 2010年 | 1033篇 |
| 2009年 | 620篇 |
| 2008年 | 925篇 |
| 2007年 | 1356篇 |
| 2006年 | 289篇 |
| 2005年 | 599篇 |
| 2004年 | 614篇 |
| 2003年 | 563篇 |
| 2002年 | 305篇 |
| 2001年 | 147篇 |
| 2000年 | 152篇 |
| 1999年 | 124篇 |
| 1998年 | 111篇 |
| 1997年 | 128篇 |
| 1996年 | 135篇 |
| 1995年 | 129篇 |
| 1994年 | 124篇 |
| 1993年 | 103篇 |
| 1992年 | 124篇 |
| 1991年 | 114篇 |
| 1990年 | 108篇 |
| 1989年 | 95篇 |
| 1988年 | 93篇 |
| 1987年 | 75篇 |
| 1986年 | 68篇 |
| 1985年 | 77篇 |
| 1984年 | 67篇 |
| 1983年 | 81篇 |
| 1982年 | 78篇 |
| 1981年 | 82篇 |
| 1980年 | 86篇 |
| 1979年 | 79篇 |
| 1978年 | 58篇 |
| 1977年 | 51篇 |
| 1976年 | 58篇 |
| 1975年 | 44篇 |
| 1974年 | 41篇 |
| 1971年 | 29篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
1.
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
2.
3.
4.
5.
6.
7.
8.
Anthony J. Sadar 《Science & Education》2018,27(1-2):233-235
9.
10.
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