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   30972篇
  免费   453篇
  国内免费   20篇
教育   22250篇
科学研究   2351篇
各国文化   406篇
体育   2861篇
综合类   10篇
文化理论   330篇
信息传播   3237篇
  2021年   299篇
  2020年   485篇
  2019年   727篇
  2018年   983篇
  2017年   940篇
  2016年   928篇
  2015年   598篇
  2014年   751篇
  2013年   5893篇
  2012年   688篇
  2011年   733篇
  2010年   594篇
  2009年   589篇
  2008年   715篇
  2007年   626篇
  2006年   595篇
  2005年   529篇
  2004年   519篇
  2003年   474篇
  2002年   474篇
  2001年   580篇
  2000年   613篇
  1999年   535篇
  1998年   348篇
  1997年   345篇
  1996年   409篇
  1995年   362篇
  1994年   363篇
  1993年   305篇
  1992年   450篇
  1991年   464篇
  1990年   434篇
  1989年   445篇
  1988年   414篇
  1987年   387篇
  1986年   381篇
  1985年   431篇
  1984年   347篇
  1983年   371篇
  1982年   306篇
  1981年   316篇
  1980年   332篇
  1979年   411篇
  1978年   307篇
  1977年   278篇
  1976年   248篇
  1975年   221篇
  1974年   214篇
  1973年   204篇
  1971年   200篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Working Graphs     
  相似文献   
94.
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   
95.
96.
97.
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   
98.
99.
100.
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   
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