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   12439篇
  免费   249篇
  国内免费   1篇
管理学   1879篇
民族学   72篇
人才学   1篇
人口学   1140篇
丛书文集   53篇
理论方法论   1253篇
综合类   158篇
社会学   6114篇
统计学   2019篇
  2023年   85篇
  2021年   70篇
  2020年   196篇
  2019年   296篇
  2018年   310篇
  2017年   455篇
  2016年   324篇
  2015年   264篇
  2014年   308篇
  2013年   2113篇
  2012年   432篇
  2011年   444篇
  2010年   311篇
  2009年   273篇
  2008年   297篇
  2007年   328篇
  2006年   337篇
  2005年   308篇
  2004年   307篇
  2003年   260篇
  2002年   292篇
  2001年   286篇
  2000年   262篇
  1999年   261篇
  1998年   202篇
  1997年   200篇
  1996年   181篇
  1995年   159篇
  1994年   151篇
  1993年   169篇
  1992年   168篇
  1991年   176篇
  1990年   175篇
  1989年   193篇
  1988年   134篇
  1987年   145篇
  1986年   133篇
  1985年   144篇
  1984年   145篇
  1983年   139篇
  1982年   121篇
  1981年   115篇
  1980年   113篇
  1979年   112篇
  1978年   106篇
  1977年   79篇
  1976年   81篇
  1975年   81篇
  1974年   72篇
  1973年   57篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Abstract

Accessibility of library electronic resources is a must. Its importance derives from professional ethics of librarianship, rising total costs of acquisition, and mounting legal challenges to colleges and universities that fail to provide resources accessible to users with disabilities. Library staff are responsible for ensuring the accessibility of vendor-licensed eresources. This column reviews the accessibility clauses of nine model license agreements for electronic resources. It describes terms that should go into an optimal accessibility clause and creates a composite model clause. It also provides guidance for library staff seeking to negotiate stronger accessibility language into vendor license agreements. Finally, it addresses the impact of accommodation requests on the total cost of acquiring library eresources, concluding with a call to redouble efforts to advocate for greater accessibility and educate both vendors and library staff about its importance.  相似文献   
2.
3.
4.
5.
6.
7.
8.
9.
Summary.  We detail a general method for measuring agreement between two statistics. An application is two ratios of directly standardized rates which differ only by the choice of the standard. If the statistics have a high value for the coefficient of agreement then the expected squared difference between the statistics is small relative to the variance of the average of the two statistics, and inferences vary little by changing statistics. The estimation of a coefficient of agreement between two statistics is not straightforward because there is only one pair of observed values, each statistic calculated from the data. We introduce estimators of the coefficient of agreement for two statistics and discuss their use, especially as applied to functions of standardized rates.  相似文献   
10.
Spatial variation in soil inorganic nitrogen across an arid urban ecosystem   总被引:4,自引:1,他引:3  
We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well as for the desert and urban sites separately. Concentrations of both NO3-N and NH4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious surfaces and lawn, whereas soil NH4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO3-N and NH4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation of soil NO3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic soil N concentrations are controlled by a number of ‘local’ or ‘neighborhood’ human-related drivers in the city, rather than factors related to an urban-rural gradient.  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