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   177943篇
  免费   15756篇
  国内免费   11822篇
电工技术   30053篇
技术理论   7篇
综合类   16846篇
化学工业   9416篇
金属工艺   6878篇
机械仪表   16278篇
建筑科学   15112篇
矿业工程   7143篇
能源动力   4948篇
轻工业   4709篇
水利工程   5501篇
石油天然气   5938篇
武器工业   2707篇
无线电   14110篇
一般工业技术   8538篇
冶金工业   8128篇
原子能技术   1230篇
自动化技术   47979篇
  2024年   753篇
  2023年   2084篇
  2022年   3353篇
  2021年   4131篇
  2020年   5020篇
  2019年   4014篇
  2018年   3526篇
  2017年   5118篇
  2016年   5708篇
  2015年   6266篇
  2014年   11903篇
  2013年   10288篇
  2012年   12965篇
  2011年   13821篇
  2010年   10457篇
  2009年   10782篇
  2008年   10740篇
  2007年   13188篇
  2006年   11810篇
  2005年   10306篇
  2004年   8540篇
  2003年   7555篇
  2002年   6068篇
  2001年   5054篇
  2000年   4342篇
  1999年   3488篇
  1998年   2673篇
  1997年   2354篇
  1996年   1868篇
  1995年   1530篇
  1994年   1312篇
  1993年   941篇
  1992年   753篇
  1991年   555篇
  1990年   429篇
  1989年   382篇
  1988年   270篇
  1987年   157篇
  1986年   112篇
  1985年   111篇
  1984年   158篇
  1983年   121篇
  1982年   116篇
  1981年   79篇
  1980年   54篇
  1979年   66篇
  1978年   48篇
  1977年   48篇
  1964年   13篇
  1959年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
梁辉 《铜业工程》2002,(4):69-71,76
提出VPN接入设备的体系结构 ,包括系统的应用模型、层次划分和内部详细结构 ,阐述实现VPN的关键技术。  相似文献   
62.
概述了鞍钢1780mm生产线技术改造工程中供电、传动及自动控制系统的构成、安装及调试技术要点,以及技术经济效果评述,可供同类工程施工参考.  相似文献   
63.
Time-domain limitations due to right half-plane zeros and poles in linear multivariable control systems are studied. Lower bounds on the interaction are derived. They show not only how the location of zeros and poles are critical in multivariable systems, but also how the zero and pole directions influence the performance. The results are illustrated on the quadruple-tank process, which is a new multivariable laboratory process.  相似文献   
64.
李建宏 《信息技术》2002,(1):65-65,67
针对企业集团分权化管理的缺点,设计出一套利用互联网络技术实现企业集团财务集中控制的模式,给出了模式的图示及说明。  相似文献   
65.
The objective, strategy, and implementation details of a new undergraduate course, Internet-based Instrumentation and Control, are presented. The course has a companion laboratory that is supported by the National Science Foundation and industry. The combination is offered to senior-level undergraduate engineering students interested in sensing, instrumentation, control, and web programming that want to learn more about the integration of these technologies for solving real-world engineering problems. The course will also be offered to gifted high school seniors with similar interests and can serve as a vehicle to attract them to engineering disciplines. Preliminary assessment of the first offering of the course is encouraging and has shown that the course has achieved success in helping students understand concepts and master basic technologies for developing Internet-based automatic systems.  相似文献   
66.
A method for the time suboptimal control of an industrial manipulator from an initial position and orientation to a final position and orientation as it moves along a specified path is proposed. Nonlinear system equations that describe the manipulator motion are linearized at each time step along the path. A method which gives the control inputs (joint angular velocities) for time suboptimal control of the manipulator is developed. In the formulation, joint angular velocity and acceleration limitations are also taken into consideration. A six degree of freedom elbow type manipulator is used in numerical examples to verify the method developed.  相似文献   
67.
Acceptance, the willingness to experience thoughts, feelings, and physiological sensations without having to control them or let them determine one's actions, is a major individual determinant of mental health and behavioral effectiveness in a more recent theory of psychopathology. This 2-wave panel study examined the ability of acceptance also to explain mental health, job satisfaction, and performance in the work domain. The authors hypothesized that acceptance would predict these 3 outcomes 1 year later in a sample of customer service center workers in the United Kingdom (N = 412). Results indicated that acceptance predicted mental health and an objective measure of performance over and above job control, negative affectivity, and locus of control. These beneficial effects of having more job control were enhanced when people had higher levels of acceptance. The authors discuss the theoretical and practical relevance of this individual characteristic to occupational health and performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
An optimal control problem with nonsmooth performance criterion described by a system of ordinary differential equations is considered. Necessary first-order optimality conditions are obtained.  相似文献   
69.
Cyclamate and its metabolite cyclohexylamine affect male fertility in high dose animal studies, but this affect has not been investigated in epidemiological studies. This paper reports the first epidemiological study designed to investigate the possibility of a relationship between cyclamate and cyclohexylamine and male fertility in humans, in which 405 cases of clinically defined infertility in men and 379 controls were surveyed. Semen evaluation, urine analysis for cyclamate and cyclohexylamine and dietary questionnaires were compared between cases and controls. No evidence was found of a significant association between cyclamate intake and male infertility; neither high cyclamate nor high cyclohexylamine excretion were associated with elevated risk. The lack of association remained after adjusting by age, area of residence, education, total energy intake and other variables. No significant correlations were observed between cyclamate intake, metabolism or excretion, and sperm count and motility. The results demonstrate no effect of cyclamate or cyclohexylamine on male fertility at the present levels of cyclamate consumption.  相似文献   
70.
This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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