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   517篇
  免费   16篇
  533篇
  2021年   11篇
  2019年   23篇
  2018年   13篇
  2017年   11篇
  2016年   16篇
  2015年   13篇
  2014年   13篇
  2013年   106篇
  2011年   4篇
  2009年   8篇
  2008年   5篇
  2007年   5篇
  2006年   6篇
  2005年   10篇
  2004年   9篇
  2003年   6篇
  2002年   6篇
  2001年   4篇
  2000年   8篇
  1999年   5篇
  1998年   8篇
  1997年   15篇
  1996年   7篇
  1994年   10篇
  1992年   5篇
  1991年   13篇
  1990年   4篇
  1989年   7篇
  1988年   8篇
  1987年   14篇
  1986年   8篇
  1985年   6篇
  1984年   6篇
  1983年   8篇
  1982年   8篇
  1981年   5篇
  1980年   7篇
  1979年   11篇
  1978年   7篇
  1977年   8篇
  1976年   7篇
  1975年   7篇
  1974年   7篇
  1973年   12篇
  1972年   6篇
  1971年   6篇
  1970年   7篇
  1969年   7篇
  1968年   5篇
  1967年   5篇
排序方式: 共有533条查询结果,搜索用时 15 毫秒
401.
The structural changes inside the French innovation system have impacted the role of defense firms since the late 1980s. Major changes have affected the defense budget and public R&D funding system in particular. The aim of this article is to understand French defense firms’ repositioning within the National Innovation System (NIS) based on an analysis of their R&D behavior over a long period of time (1987–2010). We show that French defense firms remain major players in the NIS and faced up to these major changes by adapting the funding of their R&D and their research priorities and rolling out new innovation capabilities. Additionally, they developed new innovation models to take advantage of new collaborative partnerships developed for civil and military markets.  相似文献   
402.
Why does terrorist violence escalate from some ethnic groups but not others? According to theoretical insights, many groups endure conditions that should spur on terrorist campaigns, but in reality only some carry them out. In contrast to studies emphasising motivations, this article constructs a framework centred on opportunity structures that contributes to our understanding of the rise of terrorism waged along ethnic lines. It argues that beyond grievances or other motivations, terrorist campaigns develop from communities when moderate political leaders depart from their positions in nationalist movements, causing terrorists to fill the subsequent power vacuum, while little terrorism occurs when leaders do not relinquish the nationalist agenda. This argument is evaluated with evidence from the Tamil and Muslim cases in the context of the Sri Lankan Civil War. Tamil United Liberation Front leaders left the Tamil nationalist movement in the early 1980s, enabling the Liberation Tigers of Tamil Eelam’s rise to dominate the nationalist agenda for three decades, while the Sri Lanka Muslim Congress did not relinquish the Muslim cause, which in part precluded the normalisation of violence in the community.  相似文献   
403.
404.
This article analyzes how the conflict environment in which a civilian monitoring mission is deployed influences the monitors' assessment of the operation. It draws on unique empirical material from the experience of the Sri Lanka Monitoring Mission (SLMM), deployed to oversee a ceasefire agreement in Sri Lanka 2002–2008. With material from a survey and in-depth interviews, experiences of the monitors are analyzed and changes over time are traced in relation to the monitors' assessment of the mandate and organizational set-up of the mission. The study points to the difficulty of monitoring missions to address escalation during an ongoing peace process. Its function is dependent on the goodwill of the parties. In essence, monitoring missions have the potential to strengthen peace when there is momentum in favor of progress, but when relations between the parties turn sour and the conflict escalates a civilian monitoring mission basically loses its potential. During the final stages of the war, which saw a very large number of civilian casualties, the war-torn areas were closed to international observers. Moreover, international pressure for a short-term ceasefire to alleviate the humanitarian situation was dismissed by the Sri Lankan government, which also saw the backing of several important actors, not the least China.  相似文献   
405.

The aim of this paper is to indicate the extent to which the arms race against Turkey, in which Greece and Cyprus have been entangled, imposes a defence expenditure burden that is tough for the two allies to bear. To do so we have resorted to evaluating the optimal military expenditure for the two countries, allied in the context of the Integrated Defence Doctrine, which is compatible with the constraints imposed by the resources of their economies. All experiments and scenarios examined lead to the conclusion that the current defence burden of the two allies seems to be driving their economies beyond capacity limits. The fact remains, however, that under the circumstances, a one-sided disarmament policy like the one currently followed by Greece, is a risky choice given that the long-term armament programmes pursued by Turkey, whose role in this arms race has been proven as leading, leave very small room to the Greek and Cypriot sides to reduce their own defence expenditure.  相似文献   
406.
This paper analyses the long‐run demand for defence output through a homogeneous treatment of 15 NATO member countries between 1960 and 1999. We carry out a progressive study of the interactions between either defence spending or defence burden and their main determinants: income, external threat and allied military spending. To that end, we use time‐series analysis with endogenously determined structural breaks. We further consider individual country functions related to one another through a common correlated effects method, in order to take into account explicitly the connections between members of an alliance.  相似文献   
407.
We study a stochastic interdiction model of Morton et al. IIE Transactions, 39 (2007):3–14 that locates radiation sensors at border crossings to detect and prevent the smuggling of nuclear material. In this model, an interdictor places sensors at customs checkpoints to minimize a potential smuggler's maximum probability of crossing a border undetected. We focus on a model variant in which the interdictor has different, and likely more accurate, perceptions of the system's parameters than the smuggler does. We introduce a model that is tighter and uses fewer constraints than that of Morton et al. We also develop a class of valid inequalities along with a corresponding separation procedure that can be used within a cutting‐plane approach to reduce computational effort. Computational results demonstrate the effectiveness of our approach.Copyright © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 91–100, 2014  相似文献   
408.
The container relocation problem (CRP) is concerned with emptying a single yard‐bay which contains J containers each following a given pickup order so as to minimize the total number of relocations made during their retrieval process. The CRP can be modeled as a binary integer programming (IP) problem and is known to be NP‐hard. In this work, we focus on an extension of the CRP to the case where containers are both received and retrieved from a single yard‐bay, and call it the dynamic container relocation problem. The arrival (departure) sequences of containers to (from) the yard‐bay is assumed to be known a priori. A binary IP formulation is presented for the problem. Then, we propose three types of heuristic methods: index based heuristics, heuristics using the binary IP formulation, and a beam search heuristic. Computational experiments are performed on an extensive set of randomly generated test instances. Our results show that beam search heuristic is very efficient and performs better than the other heuristic methods.Copyright © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 101–118, 2014  相似文献   
409.
This study examines the failures of the William J. Clinton and Barack Obama administrations to secure ratification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). It applies an integrated analytical framework for assessing treaty ratification that builds upon previous research in order to understand why the Clinton administration failed to achieve CTBT ratification in 1999 and why the Obama administration has so far failed to advance the treaty in the Senate. The study concludes that CTBT ratification, despite Obama administration pledges of support, remains highly unlikely. Finally, the study analyzes the common domestic political factors present in both cases and suggests areas for further research.  相似文献   
410.
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