全文获取类型
收费全文 | 21791篇 |
免费 | 314篇 |
国内免费 | 196篇 |
专业分类
教育 | 15440篇 |
科学研究 | 2020篇 |
各国文化 | 184篇 |
体育 | 1528篇 |
综合类 | 377篇 |
文化理论 | 90篇 |
信息传播 | 2662篇 |
出版年
2022年 | 136篇 |
2021年 | 298篇 |
2020年 | 332篇 |
2019年 | 401篇 |
2018年 | 537篇 |
2017年 | 587篇 |
2016年 | 541篇 |
2015年 | 490篇 |
2014年 | 737篇 |
2013年 | 3671篇 |
2012年 | 863篇 |
2011年 | 965篇 |
2010年 | 902篇 |
2009年 | 850篇 |
2008年 | 865篇 |
2007年 | 832篇 |
2006年 | 813篇 |
2005年 | 725篇 |
2004年 | 441篇 |
2003年 | 411篇 |
2002年 | 395篇 |
2001年 | 520篇 |
2000年 | 395篇 |
1999年 | 302篇 |
1998年 | 188篇 |
1997年 | 184篇 |
1996年 | 185篇 |
1995年 | 154篇 |
1994年 | 154篇 |
1993年 | 127篇 |
1992年 | 206篇 |
1991年 | 193篇 |
1990年 | 234篇 |
1989年 | 205篇 |
1988年 | 161篇 |
1987年 | 167篇 |
1986年 | 171篇 |
1985年 | 162篇 |
1984年 | 165篇 |
1983年 | 148篇 |
1982年 | 112篇 |
1981年 | 123篇 |
1980年 | 115篇 |
1979年 | 170篇 |
1978年 | 142篇 |
1977年 | 97篇 |
1976年 | 108篇 |
1975年 | 101篇 |
1973年 | 97篇 |
1971年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 281 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.
[目的/意义] 优化藏书采访工作和流通管理,实现对藏书采访、藏书总量和结构等状况适时监测、评估、调控等的标准化管理。[方法/过程] 通过对H类指数中的H指数、A指数和G指数相关性、变异性和适应性分析,遴选适用于图书流通数据分析的A指数,并根据帕累托定律采用A指数对西北农林科技大学图书馆2014-2018年的前20%的图书流通数据分别进行统计分析。[结果/结论] 研究结果表明:平均A指数对中图法一级类目与读者性别、读者专业、读者年级以及图书出版社、图书出版年、单位等数据统计分析具有较理想的表现,能够更全面、准确地遴选核心读者群、核心出版者和核心出版年;同时发现,布拉德福定律不仅能够应用于期刊管理,而且能够应用于藏书管理。本文研究能够为探索H类指数分析高校图书馆藏书流通数据提供参考依据。 相似文献
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.
高校数字图书馆现状及思考 总被引:1,自引:0,他引:1
对我国高等院校数字图书馆建设的现状进行了总结,对存在的问题做了比较分析、研究,提出了优化高等院校数字图书馆建设的几点建议。 相似文献
7.
8.
9.
10.
杨琴 《四川工程职业技术学院学报》2006,(1):98-101,95
本文通过对计算机三维动画的相关理论与技术的初步探讨,并结合环境景观动画的制作实例,介绍了该技术在园林景观动画设计方面的应用和发展前景。 相似文献