全文获取类型
收费全文 | 251篇 |
免费 | 68篇 |
国内免费 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 4篇 |
2015年 | 14篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 11篇 |
2011年 | 19篇 |
2010年 | 20篇 |
2009年 | 29篇 |
2008年 | 18篇 |
2007年 | 18篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 12篇 |
2000年 | 1篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有327条查询结果,搜索用时 15 毫秒
171.
采用一种新的碳纤维自分散工艺和专用分散设备制备出了掺量达胶结材质量8%的碳纤维增强活性粉末混凝土;研究了碳纤维掺量对活性粉末混凝土的力学性能影响规律。实验结果表明,在碳纤维掺量高时,活性粉末混凝土的力学性能受碳纤维掺量和水胶比两个因素共同作用。 相似文献
172.
为增强水泥基材料的电磁屏蔽性能,通过混凝土骨料替换的方法,实验研究了碳化硼、硼砂及石墨组合对复合材料电磁屏蔽效能的影响规律。实验结果表明单纯的碳化硼或碳化硼一硼砂作为水泥基材料骨料时,样品电磁屏蔽性能提升有限,但在添加硼介质时引入适当比例的石墨能有效改善材料的电磁屏蔽性能;另外,硼砂的添加会造成样品明显的缓凝现象,并且会对石墨导电吸波机制产生负面影响。 相似文献
173.
We study the problem of designing a two‐echelon spare parts inventory system consisting of a central plant and a number of service centers each serving a set of customers with stochastic demand. Processing and storage capacities at both levels of facilities are limited. The manufacturing process is modeled as a queuing system at the plant. The goal is to optimize the base‐stock levels at both echelons, the location of service centers, and the allocation of customers to centers simultaneously, subject to service constraints. A mixed integer nonlinear programming model (MINLP) is formulated to minimize the total expected cost of the system. The problem is NP‐hard and a Lagrangian heuristic is proposed. We present computational results and discuss the trade‐off between cost and service. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009 相似文献
174.
Logistical planning problems are complicated in practice because planners have to deal with the challenges of demand planning and supply replenishment, while taking into account the issues of (i) inventory perishability and storage charges, (ii) management of backlog and/or lost sales, and (iii) cost saving opportunities due to economies of scale in order replenishment and transportation. It is therefore not surprising that many logistical planning problems are computationally difficult, and finding a good solution to these problems necessitates the development of many ad hoc algorithmic procedures to address various features of the planning problems. In this article, we identify simple conditions and structural properties associated with these logistical planning problems in which the warehouse is managed as a cross‐docking facility. Despite the nonlinear cost structures in the problems, we show that a solution that is within ε‐optimality can be obtained by solving a related piece‐wise linear concave cost multi‐commodity network flow problem. An immediate consequence of this result is that certain classes of logistical planning problems can be approximated by a factor of (1 + ε) in polynomial time. This significantly improves upon the results found in literature for these classes of problems. We also show that the piece‐wise linear concave cost network flow problem can be approximated to within a logarithmic factor via a large scale linear programming relaxation. We use polymatroidal constraints to capture the piece‐wise concavity feature of the cost functions. This gives rise to a unified and generic LP‐based approach for a large class of complicated logistical planning problems. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009 相似文献
175.
王清 《中国人民武装警察部队学院学报》2010,26(9):42-45
旨在以世界的眼光观察中国的问题,借鉴国际经验,解决中国问题。不仅介绍了美国、德国和日本的反商业贿赂立法,而且对《联合国反腐败公约》——联合国向世界推荐的反腐败指南的相关规定做了详细介绍。在此基础上,提出了一些可资我国借鉴的立法经验。 相似文献
176.
177.
军用导航系统是数字化部队不可缺少的重要装备,但不同军兵种之间导航终端所采用的硬件平台和操作系统各不相同.在分析军用导航应用需求的基础上,采用中间件技术设计了一种"通用嵌入式GIS应用构架",屏蔽了多种操作系统间的差异,满足跨平台运行,大大加强了各类型平台间装备的互操作性和通用性;将构件技术应用于导航功能模块设计,使其可以在导航系统中快速集成,具有灵活开放的扩充能力;最后讨论了导航系统的实时性. 相似文献
178.
179.
180.
Factor screening is performed to eliminate unimportant factors so that the remaining important factors can be more thoroughly studied in later experiments. Controlled sequential bifurcation (CSB) and controlled sequential factorial design (CSFD) are two new screening methods for discrete‐event simulations. Both methods use hypothesis testing procedures to control the Type I Error and power of the screening results. The scenarios for which each method is most efficient are complementary. This study proposes a two‐stage hybrid approach that combines CSFD and an improved CSB called CSB‐X. In Phase 1, a prescreening procedure will estimate each effect and determine whether CSB‐X or CSFD will be used for further screening. In Phase 2, CSB‐X and CSFD are performed separately based on the assignment of Phase 1. The new method usually has the same error control as CSB‐X and CSFD. The efficiency, on the other hand, is usually much better than either component method. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2010 相似文献