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   23517篇
  免费   342篇
  国内免费   14篇
教育   16692篇
科学研究   1937篇
各国文化   257篇
体育   2345篇
综合类   9篇
文化理论   219篇
信息传播   2414篇
  2021年   246篇
  2020年   370篇
  2019年   561篇
  2018年   753篇
  2017年   708篇
  2016年   691篇
  2015年   429篇
  2014年   552篇
  2013年   4336篇
  2012年   499篇
  2011年   552篇
  2010年   423篇
  2009年   451篇
  2008年   489篇
  2007年   457篇
  2006年   427篇
  2005年   368篇
  2004年   400篇
  2003年   319篇
  2002年   340篇
  2001年   465篇
  2000年   511篇
  1999年   444篇
  1998年   261篇
  1997年   258篇
  1996年   309篇
  1995年   251篇
  1994年   262篇
  1993年   227篇
  1992年   357篇
  1991年   369篇
  1990年   339篇
  1989年   347篇
  1988年   312篇
  1987年   314篇
  1986年   308篇
  1985年   340篇
  1984年   278篇
  1983年   275篇
  1982年   218篇
  1981年   220篇
  1980年   234篇
  1979年   329篇
  1978年   233篇
  1977年   213篇
  1976年   187篇
  1975年   165篇
  1974年   169篇
  1973年   165篇
  1971年   151篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
71.
72.
73.
An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay.  相似文献   
74.
75.
How will the expansion of the concept of construct validity affect validation practice in employment testing? How does the need for consequential validity differ in educational and employment testing? How do the research bases differ for performance assessment in these settings? Are there parallel trends in policies for test use in education and industry?  相似文献   
76.
77.
78.
This paper examines end-user, online searching using data from a questionnaire mailed to 150 Canadian health professionals in practice settings. The response rate was 83% (n = 124). The data provide a demographic profile of early adopters of end-user searching in the health care community. Positive correlations with the user's level of implementation of end-user searching were found for the following variables: amount of time spent in research activities, amount of system training received, and use of Medical Subject Headings (MeSH). There was a negative association between the amount of time spent in patient care and implementation level. General practitioners and family physicians had lower implementation levels than physicians in other specialties. Successful implementers were more likely to be computer literate and to place a high value on formal information sources such as books, journals, and libraries. Health professionals using so-called "user-friendly" or menu-based software had lower levels of personal commitment to using online databases, as measured by a combination of continuance of use, willingness to pay personally, type of recommendations made to colleagues, and hardware ownership.  相似文献   
79.
80.
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