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   3482篇
  免费   824篇
  国内免费   279篇
  2024年   6篇
  2023年   20篇
  2022年   41篇
  2021年   64篇
  2020年   79篇
  2019年   80篇
  2018年   101篇
  2017年   197篇
  2016年   198篇
  2015年   131篇
  2014年   303篇
  2013年   320篇
  2012年   246篇
  2011年   290篇
  2010年   220篇
  2009年   283篇
  2008年   224篇
  2007年   199篇
  2006年   223篇
  2005年   206篇
  2004年   198篇
  2003年   147篇
  2002年   127篇
  2001年   125篇
  2000年   82篇
  1999年   73篇
  1998年   67篇
  1997年   61篇
  1996年   47篇
  1995年   42篇
  1994年   47篇
  1993年   37篇
  1992年   32篇
  1991年   35篇
  1990年   14篇
  1989年   9篇
  1988年   7篇
  1987年   3篇
  1975年   1篇
排序方式: 共有4585条查询结果,搜索用时 15 毫秒
111.
We evaluate the effect of competition on prices, profits, and consumers' surplus in multiperiod, finite horizon, dynamic pricing settings. In our base model, a single myopic consumer visits two competing retailers, who offer identical goods, in a (first order Markovian) probabilistic fashion—if the posted price exceeds the consumer's valuation for the good, he returns to the same store in the following period with a certain probability. We find that even a small reduction in the return probability from one—which corresponds to the monopoly case at which prices decline linearly—is sufficient to revert the price decline from a linear into an exponential shape. Each retailer's profit is particularly sensitive to changes in his return probability when it is relatively high, and is maximized under complete loyalty behavior (i.e., return probability is one). On the other hand, consumer surplus is maximized under complete switching behavior (i.e., return probability is zero). In the presence of many similar consumers, the insights remain valid. We further focus on the extreme scenario where all consumers follow a complete switching behavior, to derive sharp bounds, and also consider the instance where, in this setting, myopic consumers are replaced with strategic consumers. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011  相似文献   
112.
We study a stochastic inventory model of a firm that periodically orders a product from a make‐to‐order manufacturer. Orders can be shipped by a combination of two freight modes that differ in lead‐times and costs, although orders are not allowed to cross. Placing an order as well as each use of each freight mode has a fixed and a quantity proportional cost. The decision of how to allocate units between the two freight modes utilizes information about demand during the completion of manufacturing. We derive the optimal freight mode allocation policy, and show that the optimal policy for placing orders is not an (s,S) policy in general. We provide tight bounds for the optimal policy that can be calculated by solving single period problems. Our analysis enables insights into the structure of the optimal policy specifying the conditions under which it simplifies to an (s,S) policy. We characterize the best (s,S) policy for our model, and through extensive numerical investigation show that its performance is comparable with the optimal policy in most cases. Our numerical study also sheds light on the benefits of the dual freight model over the single freight models. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011  相似文献   
113.
随着信息技术的迅猛发展,新媒介对大学生的影响日益深刻。新媒介具有对大学生进行思想政治教育的先天优势,但新媒介环境下的思想政治教育危机也不容忽视。我们应当扬长避短,积极探索利用新媒介开展思想政治教育的新路径,不断提高思想政治教育的针对性和有效性。  相似文献   
114.
灾情信息是灭火及应急救援行动的关键因素,在救援行动中发挥重要作用。介绍了灾情信息的基本概念、具体内容和表现形式,详细分析了消防部队在灭火和应急救援行动中灾情信息的应用现状和发展方向,并对灾情信息的应用提出了部分改进建议,为灭火和应急救援的信息化建设提供技术支持。  相似文献   
115.
根据石油化工企业生产特点,阐述了石油化工企业火灾现场特点、火灾事故调查的重点内容、调查采取的方法和技术以及事故调查当中的注意事项,为开展好石油化工企业火灾调查工作提供参考。  相似文献   
116.
边防工作作为国防的重要组成部分,涉外性强,受周边安全形势影响大。当前,我国的边防工作既面·l盏着难得的发展机遇,同时更要直面各种挑战。分析周边安全环境对我国边防的影响,可以使我们更好地认清形势,趋利避害,抓住机遇,充分发挥职能作用,确保边防安全稳定。  相似文献   
117.
灭火作战初战是整个灭火战斗的前期战,它的成功与否直接影响到整个灭火战斗的成败。重点论述了如何把握初战的火情侦查、火场救人、控制火势等三个关键环节,以期对基层广大指战员有所指导。  相似文献   
118.
针对现有任务分配方法在任务点较多时不易解算,且计算量大的问题,提出了基于模糊C-均值聚类算法的多无人机系统任务分配方法.首先,利用模糊C-均值聚类算法得到的隶属度矩阵对任务点进行初始分配;其次,针对基于空间划分聚类可能造成各UAV任务不均衡的问题,设计任务的局部优化调整规则;最后,结合单旅行商问题,利用Tabu Sea...  相似文献   
119.
In many practical multiserver queueing systems, servers not only serve randomly arriving customers but also work on the secondary jobs with infinite backlog during their idle time. In this paper, we propose a c‐server model with a two‐threshold policy, denoted by (e d), to evaluate the performance of this class of systems. With such a policy, when the number of idle servers has reached d (<c), then e (<d) idle agents will process secondary jobs. These e servers keep working on the secondary jobs until they find waiting customers exist in the system at a secondary job completion instant. Using the matrix analytic method, we obtain the stationary performance measures for evaluating different (e, d) policies. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007.  相似文献   
120.
Analytical resolution of search theory problems, as formalized by B.O. Koopman, may be applied with some model extension to various resource management issues. However, a fundamental prerequisite is the knowledge of the prior target density. Though this assumption has the definite advantage of simplicity, its drawback is clearly that target reactivity is not taken into account. As a preliminary step towards reactive target study stands the problem of resource planning under a min–max game context. This paper is related to Nakai's work about the game planning of resources for the detection of a stationary target. However, this initial problem is extended by adding new and more general constraints, allowing a more realistic modeling of the target and searcher behaviors. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007  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