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   1359篇
  免费   63篇
  2023年   6篇
  2022年   10篇
  2020年   21篇
  2019年   35篇
  2018年   44篇
  2017年   59篇
  2016年   52篇
  2015年   32篇
  2014年   36篇
  2013年   469篇
  2012年   43篇
  2011年   38篇
  2010年   45篇
  2009年   43篇
  2008年   31篇
  2007年   32篇
  2006年   16篇
  2005年   18篇
  2004年   15篇
  2003年   21篇
  2002年   18篇
  2001年   20篇
  2000年   18篇
  1999年   22篇
  1998年   9篇
  1997年   14篇
  1996年   15篇
  1995年   16篇
  1994年   13篇
  1993年   13篇
  1992年   11篇
  1991年   11篇
  1990年   10篇
  1989年   10篇
  1987年   9篇
  1986年   10篇
  1985年   8篇
  1984年   9篇
  1983年   5篇
  1982年   7篇
  1981年   13篇
  1980年   9篇
  1979年   14篇
  1977年   7篇
  1976年   8篇
  1975年   6篇
  1974年   8篇
  1973年   11篇
  1972年   5篇
  1971年   4篇
排序方式: 共有1422条查询结果,搜索用时 15 毫秒
141.
142.
143.
In this paper we extend the Harris-Todaro model of rural-to-urban migration to include urban agglomeration effects, some urban real wage flexibility, and a government budget constraint. Without employment subsidies laissez-faire migration is excessive unless real wage flexibility and agglomeration effects are high. Laissez-faire migration is too low compared with the first-best outcome supported by a subsidy, if its financing involves no costs. Simulations suggest that such a program would imply a substantial increase in taxation. If, as seems likely, an increase of this magnitude involves economic costs then the optimal outcome falls well short of first-best.  相似文献   
144.
145.
The analysis presented in this paper explores the similarities and differences between the services selected as priorities for funding by the Baltimore Ryan White CARE Act Title I Planning Council during the first 2 years of the program in this metropolitan area, and services perceived by HIV/AIDS service providers and people living with HIV/AIDS to be unmet needs. The data used for these analyses were collected as part of a study to assess the implementation and impact of the CARE Act legislation in the Baltimore eligible metropolitan area( EMS ). This project includes three interrelated components: (a) a case study of the legislatively mandated Planning Council, (b) a survey of providers representing HIV/AIDS service organizations, and (c) a qualitative field study of the perceptions of people living with HIV/AIDS about the service delivery system. Taken together, the data from these three sources describe the similarities and differences among these three groups involved in HIV/AIDS care in Baltimore, in terms of their perceptions of services needed by people living with HIV / AIDS. The conclusions drawn from this study can be used to strengthen needs assessments in Title I-EMAs throughout the United States.  相似文献   
146.
147.
148.
Photography – a novel medium of scientific representation in the XIXth century array of arts and sciences. To delve into various nineteenth century academic disciplines under the heading ‘photography in the arts and sciences’ as did last year's annual conference of the History of Science Society – the interest in such a topic only partly stems from the ‘iconic turn’ that has generally enlarged the scope of the social sciences in recent years. A more poignant feature in any such present day study will probably be a basic scepticism facing the fact that in public use photographs have been manipulated in many respects. Yet, while shying away from any simple success story, a historically minded approach to changing ‘visual paradigms’ (Historische Bildwissenschaft) has begun to emerge. In this context, it has proved of considerable heuristic value to reconsider the role of early photography in an array of science, arts and technology: Since the reliance on the traditional ways of sketching reality persisted, in many an instance where photography was introduced, the thoughts the pioneer photographers had about their new, seemingly automated business, call for close attention. Thus scholarship sets up a parallel ‘discussion room’; the lively debate on the benefit of academic drawings as opposed to photographic portraits is a case in point. Some fairly specialised reports on photographically based analyses, such as electron microscopy, point to a borderline where the very idea of representation as a correspondence of reality and imagination gets blurred. Even though any ‘visual culture’ will have to shoulder the ‘burden of representation’, it is equally likely that it will offer a deeper sensibility for the intricacies entailed in the variegated ways of illustrating or mapping chosen subjects of scientific interest. Scholarship may thus somewhat control the disillusionment that by now has become the epitome of writing on photographic history. Provided with a renewed methodological awareness for the perception process and its photographic transition, historians may strike a better balance between the ever present tendencies of a realistic and an aesthetic way of picturing the world we live in.  相似文献   
149.
150.
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