全文获取类型
| 收费全文 | 563篇 |
| 免费 | 0篇 |
专业分类
| 563篇 |
出版年
| 2021年 | 11篇 |
| 2019年 | 22篇 |
| 2018年 | 11篇 |
| 2017年 | 12篇 |
| 2016年 | 11篇 |
| 2015年 | 11篇 |
| 2014年 | 9篇 |
| 2013年 | 145篇 |
| 2009年 | 5篇 |
| 2008年 | 5篇 |
| 2007年 | 5篇 |
| 2006年 | 5篇 |
| 2005年 | 9篇 |
| 2004年 | 8篇 |
| 2003年 | 6篇 |
| 2002年 | 6篇 |
| 2001年 | 4篇 |
| 2000年 | 8篇 |
| 1999年 | 6篇 |
| 1998年 | 8篇 |
| 1997年 | 15篇 |
| 1996年 | 7篇 |
| 1994年 | 10篇 |
| 1993年 | 4篇 |
| 1992年 | 5篇 |
| 1991年 | 14篇 |
| 1990年 | 4篇 |
| 1989年 | 7篇 |
| 1988年 | 7篇 |
| 1987年 | 14篇 |
| 1986年 | 8篇 |
| 1985年 | 7篇 |
| 1984年 | 5篇 |
| 1983年 | 8篇 |
| 1982年 | 8篇 |
| 1981年 | 6篇 |
| 1980年 | 9篇 |
| 1979年 | 11篇 |
| 1978年 | 7篇 |
| 1977年 | 8篇 |
| 1976年 | 8篇 |
| 1975年 | 7篇 |
| 1974年 | 10篇 |
| 1973年 | 13篇 |
| 1972年 | 7篇 |
| 1971年 | 6篇 |
| 1970年 | 7篇 |
| 1969年 | 6篇 |
| 1968年 | 5篇 |
| 1967年 | 5篇 |
排序方式： 共有563条查询结果，搜索用时 0 毫秒
341.
Corine M. Laan Ana Isabel Barros Richard J. Boucherie Herman Monsuur Judith Timmer 《海军后勤学研究》2019,66(2):174-190
In this paper, we introduce partially observable agent‐intruder games (POAIGs). These games model dynamic search games on graphs between security forces (an agent) and an intruder given possible (border) entry points and high value assets that require protection. The agent faces situations with dynamically changing, partially observable information about the state of the intruder and vice versa. The agent may place sensors at selected locations, while the intruder may recruit partners to observe the agent's movement. We formulate the problem as a two‐person zero‐sum game, and develop efficient algorithms to compute each player's optimal strategy. The solution to the game will help the agent choose sensor locations and design patrol routes that can handle imperfect information. First, we prove the existence of ?‐optimal strategies for POAIGs with an infinite time horizon. Second, we introduce a Bayesian approximation algorithm to identify these ?‐optimal strategies using belief functions that incorporate the imperfect information that becomes available during the game. For the solutions of large POAIGs with a finite time horizon, we use a solution method common to extensive form games, namely, the sequence form representation. To illustrate the POAIGs, we present several examples and numerical results. 相似文献
342.
We consider the problem of optimally maintaining a stochastically degrading, single‐unit system using heterogeneous spares of varying quality. The system's failures are unannounced; therefore, it is inspected periodically to determine its status (functioning or failed). The system continues in operation until it is either preventively or correctively maintained. The available maintenance options include perfect repair, which restores the system to an as‐good‐as‐new condition, and replacement with a randomly selected unit from the supply of heterogeneous spares. The objective is to minimize the total expected discounted maintenance costs over an infinite time horizon. We formulate the problem using a mixed observability Markov decision process (MOMDP) model in which the system's age is observable but its quality must be inferred. We show, under suitable conditions, the monotonicity of the optimal value function in the belief about the system quality and establish conditions under which finite preventive maintenance thresholds exist. A detailed computational study reveals that the optimal policy encourages exploration when the system's quality is uncertain; the policy is more exploitive when the quality is highly certain. The study also demonstrates that substantial cost savings are achieved by utilizing our MOMDP‐based method as compared to more naïve methods of accounting for heterogeneous spares. 相似文献
343.
344.
Brandon M. Boylan 《Civil Wars》2019,21(1):104-127
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
345.
This article presents a flexible days‐on and days‐off scheduling problem and develops an exact branch and price (B&P) algorithm to find solutions. The main objective is to minimize the size of the total workforce required to cover time‐varying demand over a planning horizon that may extend up to 12 weeks. A new aspect of the problem is the general restriction that the number of consecutive days on and the number of consecutive days off must each fall within a predefined range. Moreover, the total assignment of working days in the planning horizon cannot exceed some maximum value. In the B&P framework, the master problem is stated as a set covering‐type problem whose columns are generated iteratively by solving one of three different subproblems. The first is an implicit model, the second is a resource constrained shortest path problem, and the third is a dynamic program. Computational experiments using both real‐word and randomly generated data show that workforce reductions up to 66% are possible with highly flexible days‐on and days‐off patterns. When evaluating the performance of the three subproblems, it was found that each yielded equivalent solutions but the dynamic program proved to be significantly more efficient. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 60: 678–701, 2013 相似文献
346.
The article examines alternative strategies to combating the scourge of terrorism beyond military approaches. There is now more realization, especially after the difficulties experienced in Iraq today, that an innovative multi-pronged mix of methods is needed to combat international terrorism. The paper looks at an ideological response towards combating terrorism by looking at the Singapore experience. The Singapore government recognizes the importance of an ideological response as an integral part of counterterrorism measures. Terrorism occurs when opportunity, motivation and capability meet. The prevention of terrorism requires the elimination of at least one of these three factors- motivation- often driven by ideology. The paper will look at direct and indirect initiatives undertaken in Singapore to combat terrorism and will also look at the Muslim community in Singapore's response to the threat to Singapore society. Lastly, the article will examine some lessons learnt from the Singapore experience in applying an ideological approach in combating terrorism as well as some recommendations of what more can be done to move forward. 相似文献
347.
A. S. Andreou K. E. Parsopoulos M. N. Vrahatis G. A. Zombanakis 《Defence and Peace Economics》2013,24(4):329-347
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
348.
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
349.
For a service provider facing stochastic demand growth, expansion lead times and economies of scale complicate the expansion timing and sizing decisions. We formulate a model to minimize the infinite horizon expected discounted expansion cost under a service‐level constraint. The service level is defined as the proportion of demand over an expansion cycle that is satisfied by available capacity. For demand that follows a geometric Brownian motion process, we impose a stationary policy under which expansions are triggered by a fixed ratio of demand to the capacity position, i.e., the capacity that will be available when any current expansion project is completed, and each expansion increases capacity by the same proportion. The risk of capacity shortage during a cycle is estimated analytically using the value of an up‐and‐out partial barrier call option. A cutting plane procedure identifies the optimal values of the two expansion policy parameters simultaneously. Numerical instances illustrate that if demand grows slowly with low volatility and the expansion lead times are short, then it is optimal to delay the start of expansion beyond when demand exceeds the capacity position. Delays in initiating expansions are coupled with larger expansion sizes. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009 相似文献
350.
In this article we explore how two competing firms locate and set capacities to serve time‐sensitive customers. Because customers are time‐sensitive, they may decline to place an order from either competitor if their expected waiting time is large. We develop a two‐stage game where firms set capacities and then locations, and show that three types of subgame perfect equilibria are possible: local monopoly (in which each customer is served by a single firm, but some customers may be left unserved), constrained local monopoly (in which firms serve the entire interval of customers but do not compete with each other), and constrained competition (in which firms also serve the entire interval of customers, but now compete for some customers). We perform a comparative statics analysis to illustrate differences in the equilibrium behavior of a duopolist and a coordinated monopolist. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 相似文献