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   42031篇
  免费   1654篇
  2020年   542篇
  2019年   846篇
  2018年   959篇
  2017年   1165篇
  2016年   1250篇
  2015年   940篇
  2014年   920篇
  2013年   14293篇
  2012年   1068篇
  2011年   1084篇
  2010年   1095篇
  2009年   1084篇
  2008年   1021篇
  2007年   935篇
  2006年   836篇
  2005年   582篇
  2004年   580篇
  2003年   533篇
  2002年   510篇
  2001年   515篇
  2000年   448篇
  1999年   517篇
  1998年   462篇
  1997年   430篇
  1996年   407篇
  1995年   416篇
  1994年   363篇
  1993年   409篇
  1992年   397篇
  1991年   296篇
  1990年   291篇
  1989年   303篇
  1988年   302篇
  1987年   317篇
  1986年   297篇
  1985年   412篇
  1984年   438篇
  1983年   444篇
  1982年   390篇
  1981年   385篇
  1980年   425篇
  1979年   418篇
  1978年   402篇
  1977年   426篇
  1976年   378篇
  1975年   382篇
  1974年   286篇
  1973年   269篇
  1972年   244篇
  1970年   219篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
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   
954.
955.
956.
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   
957.
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   
958.
959.
960.
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