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   964篇
  免费   246篇
  国内免费   53篇
  2024年   1篇
  2023年   8篇
  2022年   16篇
  2021年   15篇
  2020年   30篇
  2019年   24篇
  2018年   21篇
  2017年   66篇
  2016年   59篇
  2015年   46篇
  2014年   81篇
  2013年   68篇
  2012年   78篇
  2011年   78篇
  2010年   64篇
  2009年   76篇
  2008年   68篇
  2007年   68篇
  2006年   69篇
  2005年   66篇
  2004年   46篇
  2003年   44篇
  2002年   30篇
  2001年   34篇
  2000年   22篇
  1999年   20篇
  1998年   12篇
  1997年   12篇
  1996年   4篇
  1995年   7篇
  1994年   6篇
  1993年   6篇
  1992年   5篇
  1991年   4篇
  1990年   6篇
  1989年   3篇
排序方式: 共有1263条查询结果,搜索用时 15 毫秒
641.
Since 2012, China’s assertion of its sovereignty claim to the contested Senkaku/Diaoyu Islands has significantly raised the risk of a potentially escalatory political-military crisis with Japan. As circumstances worsen, Japanese Prime Minister Shinzo Abe has championed major institutional reforms aimed at centralizing Japanese security policy decision-making and vastly improving crisis management. This article assesses these reforms’ significance for ameliorating Japan’s long-standing internal crisis management weaknesses, and enhancing its ability to communicate with Beijing promptly under challenging conditions. While significant issues remain, recent developments – especially the establishment of Japan’s first-ever National Security Council – demonstrate significant progress. Bilaterally, however, important firebreaks remain conspicuously absent.  相似文献   
642.
A transit vessel traffic scheduling algorithm has been developed to limit the negative effects on cargo volume throughput in two‐way waterways where separation distances between transiting vessels must be maintained and passage restrictions may hold. It runs in time that is polynomial in the number of ships involved in the computation and finds schedules which increase the utilization of waterways. Three examples illustrate its use. The first example is situated in the Sunda Strait where the algorithm is used to enhance the safety of merchant shipping against a terrorist threat. It illustrates important features of the algorithm and demonstrates how it can be used with cross traffic. The second example is situated in the Strait of Istanbul and offers a comparison between the developed algorithm and the transit vessel scheduling algorithm of Ulusçu et al., J Navig 62 (2009), 59–77. This was done using a plausible model of the Strait of Istanbul. The third and last example shows how the algorithm can be used to schedule transit vessel traffic in two‐way waterways with junctions. This feature is especially useful in congested waters with a high risk of collisions like the Inland Sea of Japan. An extreme test case proves that the developed algorithm is a practical algorithm ready for such use. © 2017 Wiley Periodicals, Inc. Naval Research Logistics 64: 225–248, 2017  相似文献   
643.
We consider a problem of optimal division of stock between a logistic depot and several geographically dispersed bases, in a two‐echelon supply chain. The objective is to minimize the total cost of inventory shipment, taking into account direct shipments between the depot and the bases, and lateral transshipments between bases. We prove the convexity of the objective function and suggest a procedure for identifying the optimal solution. Small‐dimensional cases, as well as a limit case in which the number of bases tends to infinity, are solved analytically for arbitrary distributions of demand. For a general case, an approximation is suggested. We show that, in many practical cases, partial pooling is the best strategy, and large proportions of the inventory should be kept at the bases rather than at the depot. The analytical and numerical examples show that complete pooling is obtained only as a limit case in which the transshipment cost tends to infinity. © 2017 Wiley Periodicals, Inc. Naval Research Logistics, 64: 3–18, 2017  相似文献   
644.
We study two‐agent scheduling on a single sequential and compatible batching machine in which jobs in each batch are processed sequentially and compatibility means that jobs of distinct agents can be processed in a common batch. A fixed setup time is required before each batch is started. Each agent seeks to optimize some scheduling criterion that depends on the completion times of its own jobs only. We consider several scheduling problems arising from different combinations of some regular scheduling criteria, including the maximum cost (embracing lateness and makespan as its special cases), the total completion time, and the (weighted) number of tardy jobs. Our goal is to find an optimal schedule that minimizes the objective value of one agent, subject to an upper bound on the objective value of the other agent. For each problem under consideration, we provide either a polynomial‐time or a pseudo‐polynomial‐time algorithm to solve it. We also devise a fully polynomial‐time approximation scheme when both agents’ scheduling criteria are the weighted number of tardy jobs.  相似文献   
645.
根据非局部Euler梁理论建立了外部磁场影响下的黏弹性基体上纳米梁的动力学问题分析模型。通过引入Kelvin黏弹性地基模型和洛伦兹力,得到了纳米梁的振动控制方程。基于Kelvin-Voigt黏弹性模型,给出了黏弹性基体上纳米梁在磁场影响下的固有频率解析解,并就多种典型情况进行了分析。在一般情况下,利用传递函数方法对振动控制方程进行求解,得到了纳米梁固有频率及相应振型的封闭解。以某单壁碳纳米管为例,计算得到了多种边界条件下纳米梁的前三阶固有频率,并详细分析了非局部参数、磁场强度、长细比、阻尼系数及边界条件等因素对纳米梁振动特性的影响情况。结果表明,文中所建的动力学分析模型对研究磁场作用下纳米梁在黏弹性基体上的动力学特性问题准确有效。  相似文献   
646.
陆战场空域已经成为一种重要的作战资源,对其进行科学高效的管理十分必要。分析了陆战场空域管理的特点,总结了陆战场空域管理的职能,从条令条例建设、空域管制方法和指挥体系结构等方面对美军陆战场空域管理进行了研究。  相似文献   
647.
为应对全天候、全天时实时使用要求,光电探测系统逐渐从功能单一的光电探测系统演变为多功能、多传感器的综合光电系统。因此,具体进行工程设计时,系统电源组件的技术指标要合理,满足系统使用要求。同时,组件维修、故障诊断、部件互换也要容易。针对此问题,基于描述的光电探测系统电源通用化设计原则,提出了一种可工程化设计方案。该方案对电源硬件结构设置、电源控制管理和电源功能扩展设计等进行了讨论,并给出具体设计方法。通过实际应用验证表明,该方案能够满足系统对电源组件的要求。  相似文献   
648.
指挥控制舱是武器系统中指挥控制的功能核心,通过多人协同交互完成指控任务。为提高人员协同效率和操控效率。建立了以完成所有任务的时间最短为目标函数的多人协同任务规划模型。在求解模型时,采用禁忌单亲遗传混合优化算法,通过无性繁殖的方法,减少了在子代中产生无效染色体的情况,提升了算法的效率,通过禁忌算法有效避免陷入局部极小值。通过实例分析,算法使总任务执行时间减少了12豫。本模型以及求解算法在解决指挥控制舱多人协同任务规划时具有可行性,对指挥控制舱任务流程设计具有一定参考价值。  相似文献   
649.
以组网雷达情报综合处理为背景,针对多站多目标航迹相关问题,首先介绍了动态多因子相关算法的基本原理,然后在此基础上提出了几点改进措施。利用位置因子的重要性对相关判定区域做了限制;利用航向因子对判决结果进行二次修正,同时结合目标的机动检测问题,提高了对目标强机动的检测能力;此外,根据实验结果还对综合处理中的航迹配对准则进行了修正。通过算法的改进不仅改善了航迹相关的质量,还降低了运算量。最后给出了改进后的算法流程图。  相似文献   
650.
通过一个实例分析了现有瞄准线独立控制系统的原理及特点 ,提出了一种改进方案。该方案有效地解决了现有瞄准线独立控制系统普遍存在的瞄准线动态偏移问题。采用 MATL AB/ SIMU L NK对改进前后两种瞄准线独立控制系统进行了仿真 ,其结果验证了改进方案的有效性  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