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   3321篇
  免费   82篇
  国内免费   1篇
  3404篇
  2021年   37篇
  2019年   88篇
  2018年   51篇
  2017年   80篇
  2016年   79篇
  2015年   62篇
  2014年   64篇
  2013年   696篇
  2010年   36篇
  2009年   37篇
  2008年   47篇
  2007年   52篇
  2006年   36篇
  2005年   42篇
  2004年   56篇
  2003年   42篇
  2002年   57篇
  1999年   41篇
  1998年   46篇
  1997年   48篇
  1996年   61篇
  1995年   41篇
  1994年   59篇
  1993年   63篇
  1992年   58篇
  1991年   74篇
  1990年   39篇
  1989年   72篇
  1988年   78篇
  1987年   68篇
  1986年   72篇
  1985年   64篇
  1984年   36篇
  1983年   42篇
  1982年   43篇
  1981年   46篇
  1980年   51篇
  1979年   45篇
  1978年   49篇
  1977年   45篇
  1976年   45篇
  1975年   46篇
  1974年   52篇
  1973年   50篇
  1972年   52篇
  1971年   43篇
  1970年   40篇
  1969年   40篇
  1968年   34篇
  1967年   34篇
排序方式: 共有3404条查询结果,搜索用时 0 毫秒
371.

Given the challenges posed by failed and failing states, and the likelihood that such failure will continue well into the new millennium, the need for a strategic approach appears evident. Should we respond? If so, how and with what expectations? Answers to such questions require an underlying set of strategic guidelines. This article contributes to developing that strategy by examining common manifestations of state failure and some possible response objectives. It concludes by arguing that careful and tough analysis must guide our choices about where and when to respond, and how ambitiously we set our objectives.  相似文献   
372.

A nation's wealth is both an object of conquest to covetous aggressors and a resource to its owners for self defense. To maintain autonomy every country must mount a defense which either makes its capture (1) more expensive than any aggressor can afford, or (2) more expensive than it is worth to aggressors. Whether this condition can be satisfied for all countries simultaneously depends as shown in this paper on relative efficacy of military offense versus defense, the aggregate of wealth among nations and its distribution, and the benefits a conqueror may obtain from conquest, including the duration of these benefits. The paper shows how these factors fit together to determine the sustainability and stability of the international distribution of property as embodied in the configuration of sovereign states.  相似文献   
373.
It is intrinsic to the nature of military competition that the unit acquisition costs of defence systems rise generation by generation. Traditional “bottom‐up” methods of cost‐estimating cannot meet the increasing demands for extensive studies of many options before commencing design and, while “top‐down” estimating techniques are an improvement, in particular by reducing the time required for preparing estimates, they also are inadequate to meet current requirements. A new method has been devised, therefore, further developing “top‐down” methods using Bayesian techniques to make best use of the available information, whether certain or uncertain, and its accuracy established by example.  相似文献   
374.
This paper, intended to stimulate debate, suggests that we are at a turning point in the history of the UK military aerospace industry. It argues that there is urgent need for a fresh vision as to how the UK military aerospace industry can both prosper and make its maximum contribution to the defence of Britain. Further, the resulting plans and policies must emphasise the robustness of defence capabilities in a future in which the only thing we can be certain is that it will be very different from the present – especially whenever defence most matters.  相似文献   
375.
We examine who benefits when there is a strong leader in place, and who benefits when a situation lacks a proper leader. There are fractious terrorist groups who seek to serve the same people in common cause against a common enemy. The groups compete for rents obtained from the public by engaging in actions against the common enemy. We determine the leadership structure under which each group is better off, as well as the circumstance that the common enemy prefers. We are able to state simple and general conditions for each group and the common enemy to benefit.  相似文献   
376.
This paper is the first to demonstrate a viable prediction market that successfully forecasts defense acquisition cost and schedule outcomes, and to provide insights for defense executive decision‐making. Already used in private industry, prediction markets can also accurately forecast outcomes and their associated risks for government programs. Using virtual money, prediction markets allow traders to ‘bet’ on some future outcome. This market mechanism turns out to be a relatively simple and accurate way to discover, aggregate, and communicate to a defense executive the collective market’s beliefs about the likelihood of an eventual outcome of an acquisition program of interest.  相似文献   
377.
概念模型验证是保证和提高仿真可信性的重要手段,是建模与仿真VV&A中的重点和难点.首先将概念模型的验证方法划分为非形式化方法、静态方法、动态方法和形式化方法4类,并提出了一种基于本体推理的概念模型验证方法,然后对各种方法的基本思想、基本原理、基本过程、适用对象、优缺点进行全面的分析总结,明确了各种方法的优缺点和适用范围,为如何选用各种验证方法提供参考,也明确了下一步应重点研究的问题.  相似文献   
378.
379.
380.
By comparing the Somali experience of piracy with the emerging situation in the Gulf of Guinea, I show that increases in the enforcement aspects of state capacity in the Gulf of Guinea states are necessary but not sufficient tools to combat the emergence, growth, and institutionalisation of piracy. Such tools would require state-building measures that would minimise the incentives of individuals to join piracy organisations and they would have to effectively deal with youth unemployment, income inequality, and environmental degradation.  相似文献   
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