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   425篇
  免费   13篇
  2021年   11篇
  2019年   10篇
  2017年   10篇
  2016年   13篇
  2015年   13篇
  2014年   8篇
  2013年   83篇
  2011年   4篇
  2008年   7篇
  2007年   5篇
  2006年   7篇
  2005年   7篇
  2004年   4篇
  2002年   7篇
  2001年   7篇
  2000年   5篇
  1999年   4篇
  1998年   8篇
  1997年   9篇
  1996年   5篇
  1995年   6篇
  1994年   8篇
  1993年   7篇
  1992年   7篇
  1991年   8篇
  1990年   2篇
  1989年   7篇
  1988年   15篇
  1987年   7篇
  1986年   16篇
  1985年   9篇
  1984年   6篇
  1983年   6篇
  1982年   4篇
  1981年   8篇
  1980年   6篇
  1979年   11篇
  1978年   7篇
  1977年   8篇
  1976年   2篇
  1975年   9篇
  1974年   7篇
  1973年   5篇
  1972年   7篇
  1971年   4篇
  1970年   4篇
  1969年   6篇
  1968年   3篇
  1967年   2篇
  1966年   3篇
排序方式: 共有438条查询结果,搜索用时 15 毫秒
281.
In February 1998, Osama Bin Laden published a signed statement calling for a fatwa against the United States for its having ‘declared war against God’. As we now know, the fatwa resulted in the unprecedented attack of 9/11. The issue of whether or not 9/11 was in any way predictable culminated in the public debate between Richard Clarke, former CIA Director George Tenet and the White House. This paper examines whether there was any evidence of a structural change in the terrorism data at or after February 1998 but prior to June 2001, controlling for the possibility of other breaks in earlier periods. In doing so, we use the standard Bai–Perron procedure and our sequential importance sampling (SIS) Markov Chain Monte Carlo (MCMC) method for identifying an unknown number of breaks at unknown dates. We conclude that sophisticated statistical time‐series analysis would not have predicted 9/11.  相似文献   
282.
ANGOLAN DEADLOCK     
Children on the African continent have suffered immensely from the proliferation and misuse of small arms, including death, injury, displacement, separation from families, loss of access to health, humanitarian and educational services, and lack of economic opportunities. Further, over 300,000 children serve as child soldiers, relying on small arms as their tools of war. The international community has worked to establish protections for children for over 50 years, yet children continue to suffer. The recent UN Special Session on Children adopted ‘A world fit for children’, which, in combination with the Programme of Action agreed upon at the July 2001 UN Conference on Small Arms, begins to address a comprehensive approach to eliminating the negative impacts of small arms proliferation on children in conflict.  相似文献   
283.
Abstract

The article evaluates the security challenges that are likely to occur along international borders in East Africa with the advent of the East African Community Common Market in July 2010. In an attempt to illustrate the porosity of borders and the likelihood that criminals could take advantage of the situation, the author describes the ease with which transnational crime could thrive (in the absence of efficient border security measures) under the guise of informal cross-border trade that derives its basis largely from the customs and historical linkages in the region. Border towns in the region are considered zones of risk but also opportunities for quick money-making ventures and deals that tend to attract a variety of criminals. While the danger is not alarmingly high, there is a likelihood that with the opening up of the East African Community to the free movement of goods and people, criminals will exploit this freedom to commit crimes such as human trafficking, drug smuggling and moving terrorists and contraband goods unless mechanisms are put in place to curtail these activities. Should this not happen, the mission of the East African Community could be jeopardised.  相似文献   
284.
Significant nuclear reductions by the United States can affect other states in one of five ways: by directly altering their strategic calculations and postures; by indirectly altering their strategic calculations and postures by affecting the behavior of third-party states; by undermining formal US deterrence commitments; by eroding the United States's perceived ability to provide “informal” deterrence through the maintenance of an active global presence; and by creating normative pressure for states to emulate US nuclear reductions. Only the erosion of “informal” deterrence is likely to affect South Asia; to the extent that significant US nuclear reductions affect South Asia, then, their impact is likely to be destabilizing.  相似文献   
285.
This article analyzes the public side of the NH90 network consisting of four participating countries (Germany, France, Italy, and the Netherlands) and their industrial partners. Comparable to observations in earlier international projects in the defense sector, the development and production of the NH90 defense helicopter did not match original plans and costs estimates. On the basis of four mechanisms that were intended to facilitate the cooperation between the partnering countries (the General Memorandum of Understanding; coalition formation; the role of the central agency; and the process of vertical escalation) the question is posed whether or not there was a true alignment of national interests and “logics.” The lack of standardization, as well as program delays and issues concerning the division of the work-share, lead to the emerging alignment being characterized as “quasi-alignment” at best.  相似文献   
286.
This article introduces two new maximum entropy (ME) methods for modeling the distribution of time to an event. One method is within the classical ME framework and provides characterizations of change point models such as the piecewise exponential distribution. The second method uses the entropy of the equilibrium distribution (ED) for the objective function and provides new characterizations of the exponential, Weibull, Pareto, and uniform distributions. With the same moment constraints, the classical ME and the maximum ED entropy algorithms generate different models for the interarrival time. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 427–434, 2014  相似文献   
287.
This paper formulates a problem of continuous quality production and maintenance of a machine. Quality is assumed to be a known function of the machine's (Markov diffusion process) degradation states. Applications to a specific quality function are used to obtain analytical solutions to an open-loop and feedback stochastic control maintenance problem.  相似文献   
288.
Product quality is emerging as a major strategic instrument for competition. The purpose of this article is to assess the effects of quality control on sales, and, vice versa, the effects of the sales process on quality control. A model relating quality control and the sales process (advertising, repeat purchase, and word-of-mouth effects) is developed to evaluate the above relationships. Two special cases, with degenerate and beta distribution for defect items in the production lot, are analyzed in detail. In the former case, analytical results for the optimal quality control schemes are obtained, whereas in the latter, efficient bounds are derived to search for the optimal scheme. It is shown, analytically and numerically, that the sales parameters have significant impact on whether more “stringent” or “tighter” quality control is warranted. Future research directions are also discussed.  相似文献   
289.
India and China are the 2 most populous countries of the world; in the 1950s, both countries initiated a centrally planned program for rapid development within vastly differing political systems. China embarked India's policy encouraged only voluntary acceptance of family planning. In both cases, however, government involvement in population forms a part of comprehensive national planning. Both countries rely on a limited resource base and technological sophistication in order to alleviate mass poverty and misery. The political implications of population growth cannot be neatly isolated from those that are generated by social and economic forces of change in a society that is in a transitional stage of modernization and development. Development has not been an unmixed bleesing; population growth is one of its counterproductive outcomes. The development process has begun to draw increasing attention to hitherto neglected correlates of fertility decline, such as a reduction in infant mortality, universal education, improvement in women's status, and women's participation in economic activity outside the home, all of which eventually result in greater demand for family planning services. Both the Indian and Chinese models highlight the importance of taking the people into one's confidence; the response of the common people to official initiatives is critical in securing a reduction in fertility levels. China has adopted a 1 child family policy, yet it is unreasonable to expect that the Indian people would agree to a nationally prescribed family size norm below 2 children. The principal determinant of future population trends in both these countries is the course of their politics. The success of developing countries will be assured if the developed nations support their progress without being worried about their population growth, which is the result of their unavoidable failure to modernize their social and economic structures.  相似文献   
290.
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