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   15441篇
  免费   189篇
  国内免费   119篇
教育   10576篇
科学研究   2044篇
各国文化   109篇
体育   1350篇
综合类   11篇
文化理论   120篇
信息传播   1539篇
  2020年   209篇
  2019年   307篇
  2018年   424篇
  2017年   370篇
  2016年   383篇
  2015年   242篇
  2014年   315篇
  2013年   2618篇
  2012年   297篇
  2011年   337篇
  2010年   242篇
  2009年   240篇
  2008年   252篇
  2007年   286篇
  2006年   275篇
  2005年   270篇
  2004年   254篇
  2003年   247篇
  2002年   238篇
  2001年   255篇
  2000年   271篇
  1999年   274篇
  1998年   142篇
  1997年   149篇
  1996年   183篇
  1995年   169篇
  1994年   131篇
  1993年   142篇
  1992年   216篇
  1991年   222篇
  1990年   230篇
  1989年   258篇
  1988年   209篇
  1987年   225篇
  1986年   219篇
  1985年   250篇
  1984年   222篇
  1983年   211篇
  1982年   176篇
  1981年   168篇
  1980年   157篇
  1979年   244篇
  1978年   190篇
  1977年   180篇
  1976年   148篇
  1975年   132篇
  1974年   151篇
  1973年   132篇
  1972年   107篇
  1971年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Children’s obesity rates have increased substantially over the past several decades, due in part to unhealthy eating habits. About 75% of preschool-aged children consume fewer fruits and vegetables than recommended for health. Because children begin developing eating habits during early childhood, obesity prevention programs are increasingly targeting young children in early childhood education (ECE) settings and are involving their families in teaching about healthy eating. The purpose of this pilot study is to assess the effectiveness of a family involvement activity known as the family backpack in increasing fruit and vegetable consumption among 4- and 5-year-old children and their parents through hands-on activities that encourage them to explore and discuss fruits and vegetables at home. Forty-two families (22 experimental, 20 control) participated in the study. Families received a family backpack from their child’s ECE teacher and completed activities with their child at home during a specific week. Experimental-group backpacks contained a children’s book and three activities to encourage parent–child discussion about fruits and vegetables; control-group backpacks contained an unrelated book and activities. Children’s and parents’ fruit and vegetable consumption and frequency of serving fruits and vegetables at home were assessed using parent self-report surveys before and after completing backpack activities. Parents in the experimental group, but not the control group, reported increases in their own and their children’s fruit and vegetable consumption after completing family backpack activities. Family backpacks show promise as a tool for early childhood educators to help families reinforce and expand children’s learning and encourage healthy eating habits at home.  相似文献   
962.
Textbook vetting and evaluation process intends to ensure that the materials provided are relevant, of the required quality, suitable ad would enhance learning efficiency and effectiveness. The paper investigates the role of publishers and Tanzania Institute of Education (TIE) in the textbooks vetting and evaluation process; examines factors used to vet, evaluate and approve primary and secondary school textbooks in Tanzania and proposes Strategies that would enhance the textbook vetting, evaluation and process. The study used a mixed method research design. Respondents were selected educational publishers; MoEVT, Baraza la Kiswahili Tanzania, TIE, and Publishers Association of Tanzania. Questionnaire and semi- structured interview were used to collect data which were analysed qualitatively and quantitatively. Major findings of the study were; textbooks vetting and evaluation process is not professionally conducted although standard criteria have been established; there is not well established roles among key players involved in the vetting and evaluation process leading to conflict of interest between TIE and the publishers. The study recommends establishing an independent professional evaluation board and a well-defined timetable and effective communication among various players; enacting a book policy and adopting a limited multiple-textbook publishing system.  相似文献   
963.
Abstract

The dynamic properties of six types of tennis balls were measured using a force platform and high-speed digital video images of ball impacts on rigidly clamped tennis rackets. It was found that the coefficient of restitution reduced with velocity for impacts on a rigid surface or with a rigidly clamped tennis racket. Pressurized balls had the highest coefficient of restitution, which decreased by 20% when punctured. Pressureless balls had a coefficient of restitution approaching that of a punctured ball at high speeds. The dynamic stiffness of the ball or the ball-racket system increased with velocity and pressurized balls had the highest stiffness, which decreased by 35% when punctured. The characteristics of pressureless balls were shown to be similar to those of punctured balls at high velocity and it was found that lowering the string tension produced a smaller range of stiffness or coefficient of restitution. It was hypothesized that players might consider high ball stiffness to imply a high coefficient of restitution. Plots of coefficient of restitution versus stiffness confirmed the relationship and it was found that, generally, pressurized balls had a higher coefficient of restitution and stiffness than pressureless balls. The players might perceive these parameters through a combination of sound, vibration and perception of ball speed off the racket.  相似文献   
964.
A stochastic actor‐based model was used to investigate the origins of sex segregation by examining how similarity in sex of peers and time spent in gender‐typed activities affected affiliation network selection and how peers influenced children's (= 292; Mage = 4.3 years) activity involvement. Gender had powerful effects on interactions through direct and indirect pathways. Children selected playmates of the same sex and with similar levels of gender‐typed activities. Selection based on gender‐typed activities partially mediated selection based on sex of peers. Children influenced one another's engagement in gender‐typed activities. When mechanisms producing sex segregation were compared, the largest contributor was selection based on sex of peers; less was due to activity‐based selection and peer influence. Implications for sex segregation and gender development are discussed.  相似文献   
965.
This paper presents the results of a major investigation by questionnaire of author attitudes towards scholarly publishing, which was funded by the Publisher's Association. Altogether, the views of nearly 4,000 authors were obtained and this paper concerns just those thousand or so authors who accepted the invitation to write freely about their own personal feelings and experiences. Using QSR N6 textual analysis software, their comments were processed and themes extracted. While the rest of the questionnaire, which was formed of closed‐question, tick‐box type questions, clearly must have had some impact on their thinking, the authors had considerable latitude in regard to what they could say. The paper provides a unique opportunity to hear their views directly. The pressing topics turned out to be (in rough order of concern): the peer‐review system, copyright, journal prices, alternative business models for journal publishing, big deals, Elsevier, electronic publishing and digital journals.  相似文献   
966.
We conduct an analysis of 1835 pledges to 10 music production projects hosted on the largest Brazilian crowdfunding platform, namely the Catarse Web site, and we assess the relation between the fundraising accumulation period, the donor–entrepreneur distance and the propensity of donors to back projects. Our results suggest a significantly negative association between distance and the value of capital pledged to projects, which is consistent with the notion that the entrepreneur’s network of close contacts might play a central role in funding. Furthermore, our results contradict the idea that crowdfunding reduces the inhibiting effect of donor–entrepreneur distance. In addition, the results show that a long project exposure is associated with higher values of pledges. These results suggest practical implications for the study of crowdfunding as a financing platform. This study contributes to the literature on the use of crowdfunding as an alternative funding source in a major emerging market.  相似文献   
967.
Supplying MEDLINE services to a widely dispersed user population in the developing countries creates numerous problems not encountered by other MEDLINE centres. The inability to interact with the user complicates system promotion and makes search formulation sometimes a gamble. Nevertheless, an evaluation survey has shown high user satisfaction. Of great concern is the still inadequate solution of document delivery. Near-term objectives are the broadening of geographic coverage and the integration of search processing with supporting hard copy supply.  相似文献   
968.
969.
970.
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