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   1812篇
  免费   170篇
  国内免费   80篇
电工技术   86篇
综合类   276篇
化学工业   175篇
金属工艺   60篇
机械仪表   138篇
建筑科学   85篇
矿业工程   32篇
能源动力   41篇
轻工业   83篇
水利工程   35篇
石油天然气   43篇
武器工业   7篇
无线电   199篇
一般工业技术   163篇
冶金工业   64篇
原子能技术   4篇
自动化技术   571篇
  2025年   6篇
  2024年   15篇
  2023年   27篇
  2022年   35篇
  2021年   37篇
  2020年   38篇
  2019年   33篇
  2018年   44篇
  2017年   54篇
  2016年   58篇
  2015年   47篇
  2014年   100篇
  2013年   96篇
  2012年   133篇
  2011年   122篇
  2010年   98篇
  2009年   71篇
  2008年   119篇
  2007年   121篇
  2006年   103篇
  2005年   80篇
  2004年   92篇
  2003年   78篇
  2002年   66篇
  2001年   49篇
  2000年   44篇
  1999年   43篇
  1998年   33篇
  1997年   33篇
  1996年   22篇
  1995年   29篇
  1994年   19篇
  1993年   20篇
  1992年   12篇
  1991年   13篇
  1990年   10篇
  1989年   7篇
  1988年   2篇
  1987年   3篇
  1986年   3篇
  1985年   6篇
  1984年   10篇
  1983年   11篇
  1982年   3篇
  1978年   2篇
  1976年   4篇
  1975年   3篇
  1957年   1篇
  1956年   1篇
  1954年   1篇
排序方式: 共有2062条查询结果,搜索用时 0 毫秒
1.
This paper is a review of the approachesdeveloped to solve 2D packing problems withmeta-heuristic algorithms. As packing tasks arecombinatorial problems with very large searchspaces, the recent literature encourages theuse of meta-heuristic search methods, inparticular genetic algorithms. The objective ofthis paper is to present and categorise thesolution approaches in the literature for 2Dregular and irregular strip packing problems.The focus is hereby on the analysis of themethods involving genetic algorithms. Anoverview of the methods applying othermeta-heuristic algorithms including simulatedannealing, tabu search, and artificial neuralnetworks is also given.  相似文献   
2.
二维小波变换理论在地震信号去噪中的应用   总被引:3,自引:0,他引:3  
针对地震信号随机干扰和规则干扰的特点,运用二维小波变换的理论,设计了相应的变换域去噪滤波器。理论记录和实际野外记录试算表明,二维小波变换具有较强的信噪分离作用。只要运用得当就能取得满意的效果。  相似文献   
3.
染色过程中取得深色效果的几种途径   总被引:1,自引:0,他引:1  
文章针对纺织品深浓色染色较为困难的实际情况,从分析深色效果的基本理论着手,对染色中常用的提高织物上染率手段进行比较分析,并对几种取得深浓色效果的主要途径作出综述。  相似文献   
4.
An experimental study was performed on the nucleate boiling of water in the narrow space formed between an interference piece and the heating surface of heat‐proof glass. A past study analyzed the bubble growth due to the conduction of heat through the thinner liquid layer under a growing bubble; however, the thickness of the liquid layer was not shown experimentally. This study investigates the thickness of this thinner layer by the interference method. Almost no change was found on the thickness of the liquid layer under both the interference‐piece and on the heating surface. The experimental results indicate the great contribution of superheating of the test liquid to bubble growth. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 165–177, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/htj.20100  相似文献   
5.
We discuss the problem of designing a telecommunication network with the survivability requirement that the network should be composed of connected rings of links. The network design problem is then to choose links from a given network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. The traffic between rings may pass through other rings. Each ring is associated with a certain fixed cost depending on the length of the ring. We describe the problem, modeled as a linear integer programming problem, and a heuristic solution method, based on column generation and Lagrangean relaxation.  相似文献   
6.
The rapid introduction of wavelength division multiplexing (WDM) technology to cope with the increased bandwidth requirements of transmission networks has intensified the need for recovery mechanisms at the optical layer. A first step towards survivable optical networking will be seen through the introduction of optical rings. This paper presents different types of optical rings (dedicated and shared protection WDM rings) and the planning issues associated with these WDM rings. In particular, we give mathematical models as well as solution methods for the ring loading and wavelength assignment problem. We compare the wavelength requirement of dedicated and shared protection rings under scenarios with different demand patterns. We also discuss the influence of the WDM equipment cost, and present a mathematical model for the optimization of hybrid networks with both dedicated and shared protection rings.  相似文献   
7.
Much work has focused on traffic grooming in SONET/WDM ring networks. Previous work has considered many aspects of traffic grooming, including minimizing the number of ADMs, minimizing the number of wavelengths, considering different traffic models, using different network architectures, incorporating switching capability and so on. In this work, we study traffic grooming in unidirectional ring networks with no switching capability under both uniform traffic and non-uniform traffic models to reduce electronic multiplexing costs. Based on the clustering notion, we derive a general and tighter lower bound for the number of ADMs required in traffic grooming under the uniform all-to-all traffic model. This bound reduces to special cases obtained in previous work. We also derive general, tighter, and closed form lower bounds for the number of ADMs required under two non-uniform traffic models: the distance-dependent traffic model and the non-uniform symmetric traffic model. Cost-effective multi-phase algorithms that exploit traffic characteristics are then designed and studied to efficiently groom traffic streams under different traffic models. Our numerical and simulation results show that the proposed multi-phase algorithms outperform existing traffic grooming algorithms by using a fewer number of ADMs. Our algorithms in several cases also achieve the lower bounds derived.  相似文献   
8.
提出了一种新型移位计数器,用实例讨论了各种双模、多模移位计数器的设计。因为移位计数器的设计可查已有的反馈函数表达式,所以十分容易。这种新型移位计数器不仅可以用于在吞脉冲技术中提高前置分频器的工作速率,而且特别适宜在有较大延迟的反馈控制系统中使用。  相似文献   
9.
通过分析各种SPWM采样算法的优点与缺陷,提出了一种新的SPWM采样算法,并采用Matlab软件计算出在该算法下开关器件的开通与关断时刻点,同时将其与规则采样法、切线采样法的时刻点比较。结果表明:新型的采样算法产生的SPWM脉冲比规则采样法、切线采样法更接近自然采样算法产生的脉冲,计算量远远小于自然算法,体现了该新型采样算法的优越性。最后通过DsP验证该新型算法的可行性。  相似文献   
10.
This work describes a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for application in WDM mesh networks. This study explores the choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays. Accordingly, the primary aim of this work is to use networking segments near faults to share the restoration load throughout a mesh network. Each node searches for restoration paths in their near environment using the proposed DMRA. Nodes use distributed control to search for neighboring nodes and to establish the relationship between them to build numerous logical rings. Nodes can also locate faults in the logical rings. These rings establish the restoration paths. The traffic load over failed links or nodes can be diverted to other paths in the networking segments. The cost of the restoration paths is computed at each node based on both the current capacity and the transmission delay. The selected restoration paths are suitable transmission routes in the network neighborhood. Hence, restoration paths can be identified and wavelength assigned quickly according to network bandwidth and traffic load. Simulation results reveal that the proposed method works extremely quickly and has a high success rate. Consequently, it is very useful for applications in real WDM networks, where the status varies from minute to minute.Corresponding author is presently a guest scientist with the National Institute of Standards and Technology, USA. This research was partially supported by the Grant of National Science Council, ROC (NSC-92-2218-E-155-004 and NSC-93-2917-I-155-001).  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