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   639篇
  免费   196篇
  国内免费   16篇
  851篇
  2022年   7篇
  2021年   28篇
  2020年   4篇
  2019年   5篇
  2018年   1篇
  2017年   7篇
  2016年   3篇
  2015年   21篇
  2014年   24篇
  2013年   31篇
  2012年   19篇
  2011年   21篇
  2010年   50篇
  2009年   51篇
  2008年   34篇
  2007年   65篇
  2006年   17篇
  2005年   36篇
  2004年   3篇
  2003年   3篇
  2002年   3篇
  2001年   5篇
  2000年   18篇
  1999年   69篇
  1998年   50篇
  1997年   51篇
  1996年   48篇
  1995年   31篇
  1994年   25篇
  1993年   26篇
  1992年   27篇
  1991年   18篇
  1990年   17篇
  1989年   6篇
  1988年   8篇
  1987年   6篇
  1986年   7篇
  1985年   4篇
  1983年   1篇
  1982年   1篇
排序方式: 共有851条查询结果,搜索用时 0 毫秒
271.
We study the environmental regulation of industrial activities that are organized as projects. Applications arise in construction, ship and aircraft building, and film making, among other industries. Relative to manufacturing, environmental regulation is different in project‐based industries, due to the uniqueness and geographical diversity of projects, and a lack of product takeback programs. Because the amount of waste and pollution generated by project companies can be large, regulators need environmental policies to ensure reduction of waste and pollution. We consider a regulator who attempts to maximize social welfare. We model this problem as a bilevel nonlinear program. The upper level regulator specifies waste reduction targets, which the lower level project companies meet using waste stream reduction and remediation of pollution, while attempting to control their project costs. We find that high waste diversion targets lead to outcomes with little pollution, but excessive project costs and only modest waste stream reduction. Projects that have lower task precedence density, or that have pollutants with different environmental impacts, show larger increases in project cost and time resulting from regulation. We describe a subsidy for waste stream reduction that coordinates the system, and we estimate the value of coordination. We also describe a bonus that encourages truthful reporting by project companies, and evaluate the relative cost and effectiveness of the subsidy and the bonus. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 228–247, 2015  相似文献   
272.
We consider a ship stowage planning problem where steel coils with known destination ports are to be loaded onto a ship. The coils are to be stowed on the ship in rows. Due to their heavy weight and cylindrical shape, coils can be stowed in at most two levels. Different from stowage problems in previous studies, in this problem there are no fixed positions on the ship for the coils due to their different sizes. At a destination port, if a coil to be unloaded is not at a top position, those blocking it need to be shuffled. In addition, the stability of ship has to be maintained after unloading at each destination port. The objective for the stowage planning problem is to minimize a combination of ship instability throughout the entire voyage, the shuffles needed for unloading at the destination ports, and the dispersion of coils to be unloaded at the same destination port. We formulate the problem as a novel mixed integer linear programming model. Several valid inequalities are derived to help reducing solution time. A tabu search (TS) algorithm is developed for the problem with the initial solution generated using a construction heuristic. To evaluate the proposed TS algorithm, numerical experiments are carried out on problem instances of three different scales by comparing it with a model‐based decomposition heuristic, the classic TS algorithm, the particle swarm optimization algorithm, and the manual method used in practice. The results show that for small problems, the proposed algorithm can generate optimal solutions. For medium and large practical problems, the proposed algorithm outperforms other methods. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 564–581, 2015  相似文献   
273.
船体腐蚀图像分析是计算机图像处理在船体腐蚀领域的一个应用技术.该文主要研究了船体腐蚀中断层图像匹配算法的设计与实现.该算法对于研究船体腐蚀的形成和分析具有十分重要的意义.  相似文献   
274.
图像合成是计算机图像处理领域的一个关键课题.该文提出了一种基于科体素体视技术的图像合成算法.该算法对于研究船体腐蚀图像的合成具有十分重要的意义.  相似文献   
275.
提出了一种可行的闭环校射火控模型,分析了导致脱靶量产生的诸多因素,并建立了简单可用的数学模型,据此来对脱靶量进行仿真。接着重点描述了如何实现闭环火控,通过仿真和实验,说明了该火控模型的可行性和正确性。  相似文献   
276.
运用计算机技术对三向伴流场的测试进行研究,对多点三向伴流场测量系统原理、方法及计算机辅助采样、计算和分析进行了阐述.  相似文献   
277.
天波超视距雷达评述   总被引:5,自引:1,他引:5  
天波超视距雷达以其独特的工作方式使它在抗低空突防、抗隐身、抗反辐射导弹(ARM)、抗电子干扰这“四抗”性能上有天然的优势。与其它雷达相比,效费比极高。其分布式结构也使它的抗毁性很强,但它极受环境因素制约。就该雷达的工作原理和特点、设计上要考虑的环境因素、性能、开发试验和部署及应用前景进行了讨论。  相似文献   
278.
介绍了ViewEditor的功能和系统构造,并对其图形功能的层次模型与界面设计详细论述.ViewEditor是一个基于Windows NT系统的视景仿真编辑器.它集图形、图象、声音、文字编辑于一体,支持开放式接口,具有界面优良,操作直观灵活,满足WYSIWYG等特点.  相似文献   
279.
在BS理论框架下,对0~-→0~-和0~-→1~-(0~-和1~-分别代表赝标介子和矢量介子)跃迁的形状因子进行模型无关的分析.结果表明BS框架既能给出重夸克极限下的自旋—味对称性,又能给出重夸克有效理论关于1/m_Q修正的Luke定理及其它关系.  相似文献   
280.
The explosive reaction degree and protection from explosions are concerns in the military field.In this work,the reaction degree of the composition B explosive was investigated experimentally.Multi-layered compound structures were used as barriers to weaken the blast loads.A comprehensive experiment using a high-speed camera and image processing techniques,side witness plates,and bottom witness plates was presented.Using the experimental fragment velocities,fragment piercing patterns,and damage characteristics,the reaction degree of the explosive impeded by different multi-layered com-pound structures could be precisely differentiated.Reaction parameters of the explosive obstructed by compound structures were obtained by theoretical analysis and numerical simulations.Unlike the common method in which the explosive reaction degree is only distinguished based on the initial pressure amplitude transmitted into the explosive,a following shock wave reflected from the side steel casing was also considered.Different detonation growth paths in the explosive formed.Therefore,all these shock wave propagation characteristics must be considered to analyze the explosive response impeded by compound structures.  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