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   123667篇
  免费   1909篇
  国内免费   239篇
教育   86235篇
科学研究   13485篇
各国文化   1983篇
体育   9417篇
综合类   173篇
文化理论   1084篇
信息传播   13438篇
  2021年   952篇
  2020年   1684篇
  2019年   2595篇
  2018年   3101篇
  2017年   3407篇
  2016年   3440篇
  2015年   2346篇
  2014年   3206篇
  2013年   27433篇
  2012年   2384篇
  2011年   2719篇
  2010年   2347篇
  2009年   2626篇
  2008年   2404篇
  2007年   2132篇
  2006年   2369篇
  2005年   2354篇
  2004年   3050篇
  2003年   2373篇
  2002年   2168篇
  2001年   2052篇
  2000年   1734篇
  1999年   1618篇
  1998年   1472篇
  1997年   1540篇
  1996年   1712篇
  1995年   1469篇
  1994年   1471篇
  1993年   1472篇
  1992年   1504篇
  1991年   1434篇
  1990年   1413篇
  1989年   1353篇
  1988年   1215篇
  1987年   1150篇
  1986年   1173篇
  1985年   1457篇
  1984年   1280篇
  1983年   1281篇
  1982年   1260篇
  1981年   1177篇
  1980年   1164篇
  1979年   1263篇
  1978年   1216篇
  1977年   1123篇
  1976年   1001篇
  1975年   812篇
  1974年   814篇
  1973年   789篇
  1971年   636篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
Emerging fathers experience a variety of stressors, including identity and role transitions, changes in their relationships, and challenges in developing caregiving skills. Increasing expectations for father involvement in childcare are emphasizing the importance of the father role, but social supports for new fathers remain scarce. Nineteen expectant and new fathers participated in a pilot 5-week group intervention aimed at improving stress coping and involvement attitudes using a combination of mindfulness practices and skill-building for parenting and partner communication. We administered surveys pre- and postintervention to assess efficacy in the areas of stress, depressive symptoms, father involvement attitudes, and mindfulness. Within-participant differences were compared across participants as well as examining individual reliable change. Results indicated initial reductions in stress and depressive symptoms and increases in the mindfulness constructs of nonjudgment and nonreactivity. No significant changes were found in father involvement attitudes. Perinatal intervention specific to fathers holds promise as an underexplored avenue for supporting families across the transition to parenthood.  相似文献   
923.
924.
Abstract

This article discusses the use of R programing language for executing a sentiment analysis of tweets pertaining to library topics. This discussion is situated within the literature of marketing and management sciences, which is employing methods of machine learning and business intelligence to make informed decision-making, and library administration, which has expressed great interest in social media engagement within its literature but has yet to adopt these types of analysis. Presented in this article is a sample code with instructions on how users may execute it within R to retrieve and analyze tweets relevant to library services. Two examples created using the code (analysis of top librarians’ tweets and analysis of posts about major book publishers) are used to demonstrate the functionality of the code. The code presented in this article may be used by libraries to analyze tweets about their library and library-related topics, which, in turn, may inform management and marketing design.  相似文献   
925.
926.
ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.  相似文献   
927.
ABSTRACT

The objective of this study was to analyse the effect of the use of social networks in smartphones or playing video games on the passing decision-making performance in professional soccer athletes. Participants were 25 male professional soccer athletes (mean ± SD: age 23.4 ± 2.8 years). The participants performed three randomised conditions divided into three groups: control (CON), smartphone (SMA), and video game (VID). Before and after each experimental condition, the Stroop Task assessed the level of induced mental fatigue. Then, the athletes performed a simulated soccer match. A CANON® camera recorded the matches for further analysis on passing decision-making performance. A group effect was identified (< .01) with impairment on passing decision-making performance for the SMA (p = .01, ES = 0.5) and VID (p = .01, ES = 0.5) conditions. We concluded that the use of social networks on smartphones and/or playing video games right before official soccer matches might impair the passing decision-making performance in professional soccer athletes.  相似文献   
928.
Abstract

Maternal dietary habits influence maternal and foetal health, representing a pathway for intervention to maximise pregnancy outcomes. Advice on energy intake is provided on a trimester basis, with no additional calories required in the first trimester and an additional 340?kcal?d?1 and 452?kcal?d?1 needed for the second and third trimesters. Energy intake depends on pre-gravid body mass index (BMI); underweight women are recommended an increase of 150, 200 and 300?kcal?d?1 during the first, second and third trimester, normal weight women an increase of 0, 350 and 500?kcal?d?1 and obese women an increase of 0, 450 and 350?kcal?day?1. The recommendations for carbohydrate and protein intake are 175?g?d?1 and 0.88–1.1?g?kgBM?d?1, with no change to fat intake. The number of pre-gravid obese women is rising; therefore, we need to regulate weight in women of childbearing age and limit gestational weight gain to within the recommended ranges [overweight women 6.8–11.3?kg and obese women 5.0–9.1?kg]. This can be achieved using nutritional interventions, as dietary changes have been shown to help with gestational weight management. As pregnancy has been identified as a risk factor for the development of obesity, normal weight women should gain 11.5–16.0?kg during pregnancy. While some research has shown that dietary interventions help to regulate gestational weight gain and promote postpartum weight loss to some extent, future research is needed to provide safe and effective guidelines to maximise these effects, while benefitting maternal and foetal health.  相似文献   
929.
930.
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