全文获取类型
收费全文 | 1559篇 |
免费 | 402篇 |
国内免费 | 154篇 |
专业分类
2115篇 |
出版年
2024年 | 8篇 |
2023年 | 11篇 |
2022年 | 20篇 |
2021年 | 24篇 |
2020年 | 24篇 |
2019年 | 34篇 |
2018年 | 28篇 |
2017年 | 84篇 |
2016年 | 102篇 |
2015年 | 58篇 |
2014年 | 124篇 |
2013年 | 107篇 |
2012年 | 125篇 |
2011年 | 116篇 |
2010年 | 79篇 |
2009年 | 131篇 |
2008年 | 99篇 |
2007年 | 91篇 |
2006年 | 85篇 |
2005年 | 96篇 |
2004年 | 99篇 |
2003年 | 75篇 |
2002年 | 62篇 |
2001年 | 58篇 |
2000年 | 55篇 |
1999年 | 43篇 |
1998年 | 38篇 |
1997年 | 42篇 |
1996年 | 35篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 31篇 |
1992年 | 23篇 |
1991年 | 29篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 2篇 |
排序方式: 共有2115条查询结果,搜索用时 15 毫秒
201.
202.
203.
We study a pull‐type, flexible, multi‐product, and multi‐stage production/inventory system with decentralized two‐card kanban control policies. Each stage involves a processor and two buffers with finite target levels. Production stages, arranged in series, can process several product types one at a time. Transportation of semi‐finished parts from one stage to another is performed in fixed lot sizes. The exact analysis is mathematically intractable even for smaller systems. We present a robust approximation algorithm to model two‐card kanban systems with batch transfers under arbitrary complexity. The algorithm uses phase‐type modeling to find effective processing times and busy period analysis to identify delays among product types in resource contention. Our algorithm reduces the effort required for estimating performance measures by a considerable margin and resolves the state–space explosion problem of analytical approaches. Using this analytical tool, we present new findings for a better understanding of some tactical and operational issues. We show that flow of material in small procurement sizes smoothes flow of information within the system, but also necessitates more frequent shipments between stages, raising the risk of late delivery. Balancing the risk of information delays vis‐à‐vis shipment delays is critical for the success of two‐card kanban systems. Although product variety causes time wasted in setup operations, it also facilitates relatively short production cycles enabling processors to switch from one product type to another more rapidly. The latter point is crucial especially in high‐demand environments. Increasing production line size prevents quick response to customer demand, but it may improve system performance if the vendor lead‐time is long or subject to high variation. Finally, variability in transportation and processing times causes the most damage if it arises at stages closer to the customer. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007 相似文献
204.
高层建筑消防用电设备的安全运行非常重要,其中消防供电系统的安全是重中之重。以消防电气设计应遵循的规范为依据,从消防设备供电设计、消防设备控制、消防系统的接地及过电压保护几个方面论述了确保高层建筑消防供电安全的措施。 相似文献
205.
While there has been significant previous literature on inventory transshipment, most research has focused on the dealers' demand filling decision (when to fill transshipment requests from other dealers), ignoring the requesting decision (when to send transshipment requests to other dealers). In this paper we develop optimal inventory transshipment policies that incorporate both types of decisions. We consider a decentralized system in which the dealers are independent of the manufacturer and of each other. We first study a network consisting of a very large number of dealers. We prove that the optimal inventory and transshipment decisions for an individual dealer are controlled by threshold rationing and requesting levels. Then, in order to study the impact of transshipment among independent dealers in a smaller dealer network, we consider a decentralized two‐dealer network and use a game theoretic approach to characterize the equilibrium inventory strategies of the individual dealers. An extensive numerical study highlights the impact of the requesting decision on the dealers' equilibrium behavior in a decentralized setting. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 相似文献
206.
针对目前潜艇装备软件的现状,结合工程实践,运用软件模块化思想,提出了基于构件的潜艇指控系统软件开发模型和层次化的潜艇指控系统软件体系结构,并在此基础之上,对潜艇指控系统软件进行了模块化研究,给出了潜艇指控系统软件模块框架。实践表明,该设计方法实现了软件与其他系统的集成,提高了软件的质量与可靠性。 相似文献
207.
The laser technology has made remarkable progress over the past couple of decades.It is being widely employed in diverse domains,such as holography,space sciences,spectroscopy,medical sciences,micro and power electronics,industrial engineering,and most distinctively,as directed energy military weapons.Owing to their active transmissions,laser systems are similar to microwave radars to some extent;however,unlike conventional radars,the laser operates at very high frequencies thus making it a potent enabler of narrow-beam and high energy aerial deployments,both in offensive and defensive roles.In modern avionics systems,laser target indicators and beam riders are the most common devices that are used to direct the Laser Guided Weapons(LGW)accurately to the ground targets.Additionally,compact size and outstanding angular resolution of laser-based systems motivate their use for drones and unmanned aerial applications.Moreover,the narrow-beam divergence of laser emissions offers a low probability of intercept,making it a suitable contender for secure transmissions and safety-critical operations.Furthermore,the developments in space sciences and laser technology have given syner-gistic potential outcomes to use laser systems in space operations.This paper comprehensively reviews laser applications and projects for strategic defense actions on the ground or in space.Additionally,a detailed analysis has been done on recent advancements of the laser technology for target indicators and range-finders.It also reviews the advancements in the field of laser communications for surveillance,its earlier state of the art,and ongoing scientific research and ad-vancements in the domain of high energy directed laser weapons that have revolutionized the evolving military battlefield.Besides offering a comprehensive taxonomy,the paper also critically analyzes some of the recent contributions in the associated domains. 相似文献
208.
209.
210.