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   1044篇
  免费   142篇
  国内免费   115篇
  2024年   2篇
  2023年   5篇
  2022年   13篇
  2021年   22篇
  2020年   18篇
  2019年   20篇
  2018年   14篇
  2017年   47篇
  2016年   55篇
  2015年   37篇
  2014年   71篇
  2013年   80篇
  2012年   83篇
  2011年   92篇
  2010年   49篇
  2009年   97篇
  2008年   49篇
  2007年   80篇
  2006年   105篇
  2005年   73篇
  2004年   55篇
  2003年   46篇
  2002年   30篇
  2001年   38篇
  2000年   26篇
  1999年   22篇
  1998年   11篇
  1997年   8篇
  1996年   6篇
  1995年   9篇
  1994年   8篇
  1993年   6篇
  1992年   2篇
  1991年   8篇
  1990年   10篇
  1989年   3篇
  1988年   1篇
排序方式: 共有1301条查询结果,搜索用时 15 毫秒
851.
运用冲击波理论,对横向效应增强型弹丸(Penetration with Enhanced Lateral Efficiency,PELE)侵穿金属靶板的机理进行了分析,将PELE侵彻过程中能量损失分为外壳撞击靶板区域环形塞块获得的能量,内芯撞击靶板区域塞块获得的能量,冲击波影响范围内外壳和内芯增加的内能,外壳前端外沿和内沿对靶板冲塞剪切耗能等几部分,给出了确定这些能量的计算方法;并依据能量守恒原理,给出了PELE正撞金属薄靶板靶后剩余速度的近似计算公式。公式计算结果与多种条件下实验结果均吻合较好。分析计算所得各能量损失结果表明,弹体内芯材料的变化对弹体侵彻能力的影响较小;侵彻中靶板塞块获得的能量在弹体侵彻动能损失中比重最大;外壳前端内沿对靶板的剪切能耗对弹体动能损失的影响可以忽略。  相似文献   
852.
针对概略射击条件下反舰导弹机动搜索目标策略优化选择的需求,采用搜索论的基本理论对反舰导弹机动搜捕策略问题进行了研究,建立了反舰导弹随机搜索策略、平行搜索策略和螺旋搜索策略搜捕概率计算模型,并进行了仿真计算。仿真结果表明:在已知目标概略位置的条件下,反舰导弹假若采取螺旋式搜索策略,能以较高的概率快速捕捉目标。  相似文献   
853.
为降低异常证据对合成结果的影响,提出了基于投影分解与k最近邻距离的异常证据检测算法。该算法在对证据集中所有证据进行焦元单一元素投影分解的基础上,重新构造证据的基本概率赋值,然后利用证据之间形成的欧式距离,采用k最近邻距离算法对异常证据进行检测。无线传感器网络应用实验分析表明:该算法可有效地对异常证据进行检测。对检测前后的证据利用证据合成规则进行融合对比结果发现,剔除了异常证据的合成结果并具有良好的峰值性和可分辨性,合成结果有利于融合决策。  相似文献   
854.
The anthrax attacks of 2001 energized research directed toward reducing health consequences from airborne contaminants by augmenting current heating ventilation and air-conditioning (HVAC) systems. Even during peacetime, interest will continue in improving HVAC components to reduce biocontaminants associated with sick building syndrome. Current HVAC design uses numerical simulation methods of ordinary differential equations to predict approximate performance. The authors show that state-space Laplace Transform calculations actually solve the underlying differential equations and yield algebraic expressions that provide new insight. To sharpen the arguments in favor of this methodology, attention is restricted to improving existing HVAC systems to increase protection from an external release of hazardous particulates. By nearly eliminating the need for dynamical simulation, the resulting methods can be applied to far more complex HVAC designs with little additional computational effort. The new methods reduce the time required for computation by three orders of magnitude. These algebraic methods also can be extended to disparate technical problems including internal particulate release, gas masks, and designing new protective buildings.  相似文献   
855.
The literature on the product mix decision (or master production scheduling) under the Theory of Constraints (TOC), which was developed in the past two decades, has addressed this problem as a static operational decision. Consequently, the developed solution techniques do not consider the system's dynamism and the associated challenges arising from the complexity of operations during the implementation of master production schedules. This paper aims to address this gap by developing a new heuristic approach for master production scheduling under the TOC philosophy that considers the main operational factors that influence actual throughput after implementation of the detailed schedule. We examine the validity of the proposed heuristic by comparison to Integer Linear Programming and two heuristics in a wide range of scenarios using simulation modelling. Statistical analyses indicate that the new algorithm leads to significantly enhanced performance during implementation for problems with setup times. The findings show that the bottleneck identification approach in current methods in the TOC literature is not effective and accurate for complex operations in real‐world job shop systems. This study contributes to the literature on master production scheduling and product mix decisions by enhancing the likelihood of achieving anticipated throughput during the implementation of the detailed schedule. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 357–369, 2015  相似文献   
856.
Hub terminals are important entities in modern distribution networks and exist for any transportation device, that is, cross docks and parcel distribution centers for trucks, container ports for ships, railway yards for trains, and hub airports for aircraft. In any of these hubs, the mid‐term planning task of synchronizing the transshipment of goods and passengers when servicing the transportation devices has to be solved, for which many different solution approaches specifically tailored to the respective application exist. We, however, take a unified view on synchronization in hubs and aim at a general building block. As a point of origin, a basic vertex ordering problem, the circular arrangement problem (CAP), is identified. We explain the relation between the CAP and hub processes, develop suited algorithms for solving the CAP, and extend the basic CAP by multiple additions, for example, arrival times, limited storage space, and multiple service points, make the problem adaptable to a wide range of hub terminals. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 454–469, 2015  相似文献   
857.
This article investigates the firms' optimal quality information disclosure strategies in a supply chain, wherein the supplier may encroach into the retail channel to sell products directly to end consumers. We consider two disclosure formats, namely, retailer disclosure (R-C) and supplier disclosure (S-C), and examine the optimal disclosure format from each firm's perspective. We show that either firm prefers to delegate the disclosure option to its partner when the supplier cannot encroach. However, the threat of supplier encroachment dramatically alters the firm's preference of disclosure. The supplier may prefer the S-C format to the R-C format when the entry cost is low and the disclosure cost is high to achieve a higher quality information transparency. Meanwhile, the retailer may prefer the R-C format to the S-C format when the entry cost is intermediate to deter the possible encroachment of the supplier. In this sense, the firms' preferences of disclosure format can be aligned due to the threat of supplier encroachment. The consumer surplus is always higher under the S-C format while either disclosure format can lead to a higher social welfare. We also consider an alternative scenario under which the supplier encroaches after the product quality information is disclosed. An interesting observation appears that the supplier may encroach when the product quality is low but foregoes encroachment when the product quality gets higher.  相似文献   
858.
基于搜索论的反舰导弹捕捉概率研究   总被引:1,自引:0,他引:1  
反舰导弹已成为现代海战中的主要进攻武器,正确选择反舰导弹捕捉概率计算模型,对火控系统解算、指挥决策至关重要。针对传统捕捉概率计算方法存在的不足,根据搜索论的基本原理、反舰导弹自控终点分布函数、目标位置域函数、目标分布函数、导弹雷达扫描特征等,提出了基于搜索论的捕捉概率计算方法,确定了常见目标分布条件下的现在点射击捕捉概率计算模型,通过仿真验证了模型的正确性,并由仿真结果确定了敌舰高速规避条件下目标瞄准点选取模型。  相似文献   
859.
为了解决防空火力分配问题,首先运用NSGA-II算法求出Pareto最优解集,然后运用多属性决策方法对Pareto最优解集中的解进行综合评估,并从中找出一个最优解。用区间数定性描述各属性,建立了防空火力分配的三目标优化模型。描述了NSGA-II算法和多属性决策方法的运算步骤。在仿真算例中,得到了一个最佳防空火力分配方案,说明该方法对于防空火力分配问题有良好的应用价值。  相似文献   
860.
舰艇编队防空作战信息效用分析及度量模型   总被引:1,自引:0,他引:1  
提出了信息生产-消费模型,对舰艇编队防空作战的信息效用进行了分析,建立了信息效用度量指标,根据幂指数方法建立了信息效用度量模型,并给出了应用实例。  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