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   411篇
  免费   9篇
  2021年   4篇
  2019年   7篇
  2018年   11篇
  2017年   8篇
  2016年   11篇
  2014年   7篇
  2013年   105篇
  2011年   3篇
  2010年   6篇
  2009年   5篇
  2008年   4篇
  2006年   4篇
  2005年   8篇
  2004年   4篇
  2003年   6篇
  2002年   9篇
  2001年   4篇
  2000年   6篇
  1999年   5篇
  1998年   3篇
  1997年   8篇
  1996年   4篇
  1995年   4篇
  1994年   6篇
  1993年   12篇
  1992年   6篇
  1991年   7篇
  1990年   3篇
  1989年   6篇
  1988年   11篇
  1987年   9篇
  1986年   9篇
  1985年   10篇
  1984年   10篇
  1983年   3篇
  1982年   4篇
  1981年   3篇
  1980年   5篇
  1979年   6篇
  1978年   9篇
  1977年   6篇
  1976年   4篇
  1974年   9篇
  1972年   5篇
  1971年   10篇
  1970年   5篇
  1969年   7篇
  1968年   3篇
  1967年   3篇
  1966年   2篇
排序方式: 共有420条查询结果,搜索用时 31 毫秒
411.
The use of conventional armed forces in a deterrent role merits close consideration. Instability in weak or failing states can have global ramifications, while efforts to build stability take time. In principle, conventional deterrence can be used to buy the time required for such stabilization efforts. Attempts at deterrence will, however, need to overcome credibility problems stemming from the technical limitations associated with conventional armed forces, and with the likely requirement for multiple external actors to deter multiple intrastate audiences. While deterrence might work under certain circumstances, it will not play as central a role in strategy as it did during the Cold War.  相似文献   
412.
We study the quadratic bottleneck problem (QBP) which generalizes several well‐studied optimization problems. A weak duality theorem is introduced along with a general purpose algorithm to solve QBP. An example is given which illustrates duality gap in the weak duality theorem. It is shown that the special case of QBP where feasible solutions are subsets of a finite set having the same cardinality is NP‐hard. Likewise the quadratic bottleneck spanning tree problem (QBST) is shown to be NP‐hard on a bipartite graph even if the cost function takes 0–1 values only. Two lower bounds for QBST are derived and compared. Efficient heuristic algorithms are presented for QBST along with computational results. When the cost function is decomposable, we show that QBP is solvable in polynomial time whenever an associated linear bottleneck problem can be solved in polynomial time. As a consequence, QBP with feasible solutions form spanning trees, s‐t paths, matchings, etc., of a graph are solvable in polynomial time with a decomposable cost function. We also show that QBP can be formulated as a quadratic minsum problem and establish some asymptotic results. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011  相似文献   
413.
414.
ABSTRACT

The American way of war in Afghanistan presents a conundrum for proponents of 21st-century state-building projects. How can liberal peace proponents engage in efficient state building without sacrificing their ideals? The US learned that state-building allocates a degree of command and control to powerbrokers operating in the shadows to launder aid money, traffic illicit narcotics, and engage in extrajudicial punishments. These clients failed to represent the liberal values foreign patrons endorsed, because the latter not only offered resources without conditions but also rewarded bad behavior. This issue is examined by looking at the case of post-2001 northern Afghanistan, where powerful warlords should have held greater control over their paramilitary forces, limited predatory behavior, and built stronger relationships with the community. Instead, warlords-turned-statesmen expanded their material and social influence in the north, while holding onto the informal instruments of racketeering and patronage that overwhelmed Western ideals and shaped the predatory state present in Afghanistan today. Moreover, paramilitaries were influenced by material, social, and normative incentives that rewarded violent and predatory behavior and further eroded already weak community control mechanisms at the subdistrict level.  相似文献   
415.
416.
ABSTRACT

Despite its portrayal as something new, the concept of the ‘gray zone’ is not novel. It was the Cold War battleground in which the USA and the Soviet Union waged rival unconventional campaigns, and it was there that the newly formed Central Intelligence Agency (CIA) was given responsibility for operating. This was not the organization’s original purpose, but Cold War exigencies forced Washington to improvise and build an organization with unique capabilities. These early years shaped the CIA’s operations directorate, creating two distinct cultures within the larger agency, one focused on intelligence collection and the other focused on covert action.  相似文献   
417.
418.
ABSTRACT

In recent years, an upward trend in terrorist attacks has mirrored an increase in suicide attacks. According to our preliminary analysis, the events of September 11th marked a sea change in the number of terrorist attacks. While a rich literature has evaluated why terrorists participate in suicide attacks, none have considered the uptick in volume after 9/11, and fewer yet have considered how female fighters may be contributing to this. We evaluate how both structural and female-specific factors affect the likelihood of female fighter suicide attacks. Recent literature discovered a trend in terrorist groups using females as suicide bombers due to cultural norms that permit them to get closer to targets. We test our theory using data from the Chicago Project on Security and Threats Suicide Attack Database (CPOST-SAD) and various datasets from the Quality of Government (QOG) compendium for the 1986–2016 time period. We construct a series of models that consider both female-specific and structural factors that could explain variation in the number of female suicide attacks. Our results indicate that our models encompass relatively stable patterns. Female political empowerment, female educational attainment, and female employment rates are significant and positive in our post-9/11 models, indicating that they may increase female suicide attacks. Democracy is a relevant structural factor and generally yields a positive effect on female suicide attacks across both time periods and multiple models. Ethnic fractionalization is significant in both time periods but yields a negative effect before 9/11 and a positive effect in the later period.  相似文献   
419.
This article analyzes two general warranty policies involving an initial free replacement period, followed by a pro rata period. We examine the short-run total costs and longrun average costs under these policies. Formulas for both consumer costs and manufacturer profits under warranty are derived. We also study the expected number of purchases over the product life cycle under both policies. Bounds for the expected total costs and expected number of purchases are obtained for the case where the failure distribution of the item is new better than used.  相似文献   
420.
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