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   42412篇
  免费   1649篇
  2020年   533篇
  2019年   833篇
  2018年   952篇
  2017年   1154篇
  2016年   1261篇
  2015年   949篇
  2014年   927篇
  2013年   14186篇
  2012年   1059篇
  2011年   1103篇
  2010年   1110篇
  2009年   1082篇
  2008年   1033篇
  2007年   933篇
  2006年   853篇
  2005年   597篇
  2004年   589篇
  2003年   545篇
  2002年   521篇
  2001年   520篇
  2000年   475篇
  1999年   549篇
  1998年   473篇
  1997年   430篇
  1996年   412篇
  1995年   424篇
  1994年   367篇
  1993年   421篇
  1992年   398篇
  1991年   305篇
  1990年   297篇
  1989年   314篇
  1988年   313篇
  1987年   332篇
  1986年   315篇
  1985年   433篇
  1984年   461篇
  1983年   465篇
  1982年   399篇
  1981年   393篇
  1980年   436篇
  1979年   425篇
  1978年   406篇
  1977年   434篇
  1976年   385篇
  1975年   387篇
  1974年   297篇
  1973年   274篇
  1972年   245篇
  1970年   229篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The characterization of the products of international cooperation as public goods has been severely challenged, undermining a central pillar of theories of international cooperation. I review the criticism of public goods assumptions, identifying the need to account for both exclusion and rival consumption in international cooperative arrangements. Drawing on the recent debate of states as relative versus absolute gains maximizers, I offer a characterization of international cooperative arrangements as discriminatory clubs. I develop a refined relative gains model, which focuses on relative net gains, and apply it to a hypothetical situation to illustrate its usefulness in predicting patterns of exclusion and distribution in international trade.  相似文献   
994.
995.
996.
The Campania was a fertile area, with a growing population during the eleventh and twelfth centuries, and was economically more advanced than most of the rest of southern Italy. This essay examines the impact of the Norman conquest of the south upon this region, with special reference to the settlement pattern and the aristocracy. It concludes that the role of incastellamento in changing the pattern of settlement was relatively limited, and the extensive incastellamento of the Montecassino lands (a product of Norman pressure upon the abbey) cannot be taken as typical. Furthermore, while the Norman conquest led to colonisation by French aristocrats, this did not entirely displace existing Lombard families, and widespread intermarriage led to a blurring of the distinction between Lombards and Normans. The impact of political crises during the twelfth century was also more limited than might be supposed, and continuity rather than change characterised the nobility of the Norman period.  相似文献   
997.
We develop a new conceptual approach to locating inspection stations for hazardous vehicles, prevention, and compare it to the previous, punitive, philosophy of the flow-capturing location model. We implement this preventive protection philosophy with a new mixed integer program that maximizes hazard avoidance by locating a number of inspection stations to detect and remove hazardous vehicles as early in their trips as possible. We test the model's performance and analyze the spatial characteristics of solutions simulating several potential applications. Our computations demonstrate that a relaxed integer-linear program is overly demanding computationally and that a simple greedy heuristic lacks robustness. We suggest further approaches to developing more powerful and efficient solution methods.  相似文献   
998.
999.
1000.
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