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   707891篇
  免费   3442篇
  国内免费   1222篇
电工技术   12470篇
综合类   718篇
化学工业   107099篇
金属工艺   30562篇
机械仪表   22350篇
建筑科学   15888篇
矿业工程   5066篇
能源动力   17459篇
轻工业   54069篇
水利工程   8439篇
石油天然气   18332篇
武器工业   50篇
无线电   73717篇
一般工业技术   145825篇
冶金工业   125667篇
原子能技术   18517篇
自动化技术   56327篇
  2021年   7003篇
  2020年   5482篇
  2019年   6934篇
  2018年   11384篇
  2017年   11373篇
  2016年   12122篇
  2015年   7743篇
  2014年   12851篇
  2013年   31184篇
  2012年   19598篇
  2011年   26292篇
  2010年   20774篇
  2009年   23259篇
  2008年   23874篇
  2007年   23217篇
  2006年   19785篇
  2005年   17967篇
  2004年   17401篇
  2003年   17166篇
  2002年   16340篇
  2001年   16278篇
  2000年   15265篇
  1999年   15519篇
  1998年   37737篇
  1997年   26984篇
  1996年   20575篇
  1995年   15680篇
  1994年   13784篇
  1993年   13637篇
  1992年   10194篇
  1991年   9792篇
  1990年   9781篇
  1989年   9423篇
  1988年   8773篇
  1987年   8067篇
  1986年   7876篇
  1985年   8642篇
  1984年   8175篇
  1983年   7440篇
  1982年   6960篇
  1981年   7129篇
  1980年   6887篇
  1979年   6922篇
  1978年   6895篇
  1977年   7794篇
  1976年   9765篇
  1975年   6069篇
  1974年   5916篇
  1973年   5984篇
  1972年   5116篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
This paper presents an overview of the ways in which self-esteem operates in employee communication. As they develop effective communication skills, managers need to consider the consequence of stress on employee self-esteem and performance. Persons with high self-esteem are less likely to experience workplace demands as stressful and are better able to respond effectively to those demands. This paper discusses the relationship among self-esteem, occupational stress, and communication quality, then recommends ways in which self-esteem can be enhanced through employee communication  相似文献   
993.
Enormous changes that have taken place in the last few years in Russia have revealed a need for Russian technical communicators to refocus their expertise and skills in order to enter the global marketplace successfully and competitively. Rather than dwell on the familiar differences between Americans and Russians, Cold War adversaries, a common ground exists and is growing. We share a mutual interest in the successful entry of Russian technical communicators in the global marketplace. We also share an understanding that technology is central to civilization as we know it, and that the masters of technology have a substantial influence on all activities that they touch; a belief that technology has had a major beneficial effect on the peoples of the world, but that with such power comes the potential for large, serious, and potentially devastating influences; the idea that the embrace of technology is a good cultural fit with cultures formed from revolutions, for technology in the later part of this century has come to be synonymous with rapid change, and cultures with revolutionary heritage welcome change; the notion that technological breakthroughs have profound influences on the nature of work, liberating the traditional intensive physical nature of labor to the emergence of a knowledge worker; and the belief that the global marketplace forces the need for clear and rapid communication across borders, as well as among cultures. If we can agree on these technical communications issues, then we have a firm foundation for building a gateway to communication in the global market  相似文献   
994.
995.
996.
997.
This paper presents a new technique for designing a jointly optimized residual vector quantizer (RVQ). In conventional stage-by-stage design procedure, each stage codebook is optimized for that particular stage distortion and does not consider the distortion from the subsequent stages. However, the overall performance can be improved if each stage codebook is optimized by minimizing the distortion from the subsequent stage quantizers as well as the distortion from the previous stage quantizers. This can only be achieved when stage codebooks are jointly designed for each other. In this paper, the proposed codebook design procedure is based on a multilayer competitive neural network where each layer of this network represents one stage of the RVQ. The weight connecting these layers form the corresponding stage codebooks of the RVQ. The joint design problem of the RVQ's codebooks (weights of the multilayer competitive neural network) is formulated as a nonlinearly constrained optimization task which is based on a Lagrangian error function. This Lagrangian error function includes all the constraints that are imposed by the joint optimization of the codebooks. The proposed procedure seeks a locally optimal solution by iteratively solving the equations for this Lagrangian error function. Simulation results show an improvement in the performance of an RVQ when designed using the proposed joint optimization technique as compared to the stage-by-stage design, where both generalized Lloyd algorithm (GLA) and the Kohonen learning algorithm (KLA) were used to design each stage codebook independently, as well as the conventional joint-optimization technique  相似文献   
998.
A distributed circuit-switched approach for supporting the deployment of high speed wireless personal communication services in urban areas through the interconnection of base stations via metropolitan area networks (MANs) is proposed. Broadband MANs minimize traffic congestion by dynamic sharing of link capacity and by serving as distributed switches for partitioning call control functions. While the DQDB protocol readily supports distributed packet-switching over the IEEE 802.6 MAN, isochronous traffic such as voice and video is best supported by circuit-switched connections. The authors present an enhanced bi-state pre-arbitrated (PA) transport mechanism, and associated call control and handoff management techniques, which enable distributed circuit-switching over the MAN. These capabilities are not currently addressed in the 802.6 standards. The bi-state PA transport mechanism facilitates statistical multiplexing of variable rate isochronous traffic sources. The network capacity is constrained by the call setup delay performance, and is analyzed by simulations. Alternative signaling architectures, involving different placements of call control network elements, are evaluated. The effects of erasure nodes, and close bus versus open bus architectures, are considered. The overlap inter-MAN call setup procedure is proposed to reduce delays. Different call handoff procedures are formulated according to the type of handoff and the resulting change in call connectivity. Most handoffs are intra-MAN, requiring simple procedures with short delays  相似文献   
999.
The viability of distributed control restoration using digital cross-connect systems (DCS) depends on its capability for restoring services within specified time requirements, and its economics for providing restoration compared to other alternatives. The authors report a Bellcore study for the impact of the DCS architecture on distributed restoration. This study concludes that currently proposed distributed control DCS self-healing schemes may not meet the 2 second restoration objective for large metropolitan local exchange carrier's networks, regardless of the distributed algorithm used, if the present DCS system architecture which uses serial message processing and serial path cross-connection remains unchanged. They also discuss several DCS architecture enhancement options, including a parallel processing/cross-connect DCS architecture, which may improve the service restoration time  相似文献   
1000.
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