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   95038篇
  免费   12064篇
  国内免费   5102篇
电工技术   49410篇
技术理论   4篇
综合类   7539篇
化学工业   2682篇
金属工艺   1780篇
机械仪表   3804篇
建筑科学   2989篇
矿业工程   1995篇
能源动力   8045篇
轻工业   1092篇
水利工程   2542篇
石油天然气   802篇
武器工业   601篇
无线电   12768篇
一般工业技术   3061篇
冶金工业   1730篇
原子能技术   2115篇
自动化技术   9245篇
  2024年   467篇
  2023年   1290篇
  2022年   2455篇
  2021年   2882篇
  2020年   3334篇
  2019年   2674篇
  2018年   2425篇
  2017年   3430篇
  2016年   3674篇
  2015年   4152篇
  2014年   7014篇
  2013年   5591篇
  2012年   7787篇
  2011年   8404篇
  2010年   6118篇
  2009年   6140篇
  2008年   6092篇
  2007年   7146篇
  2006年   6296篇
  2005年   5040篇
  2004年   4108篇
  2003年   3317篇
  2002年   2529篇
  2001年   2187篇
  2000年   1822篇
  1999年   1308篇
  1998年   862篇
  1997年   682篇
  1996年   664篇
  1995年   500篇
  1994年   452篇
  1993年   269篇
  1992年   240篇
  1991年   145篇
  1990年   119篇
  1989年   104篇
  1988年   76篇
  1987年   58篇
  1986年   37篇
  1985年   37篇
  1984年   59篇
  1983年   49篇
  1982年   51篇
  1981年   24篇
  1980年   12篇
  1979年   12篇
  1978年   13篇
  1977年   8篇
  1959年   14篇
  1956年   4篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Photovoltaic (PV) cells, when integrated within a building facade, offer the possibility of generating electric power and heat for local use or export. This paper reports on a project to investigate the practical operational efficiencies that might be delivered from such facades. The results from laboratory experiments and computer simulations are presented: the former were used to develop an empirical relationship between cell temperature and power output; the latter were undertaken to assess operational efficiencies under a range of climate conditions representative of the UK.  相似文献   
152.
Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.  相似文献   
153.
Local stress and strain variations in the deformation zone can be ascertained by measuring hardness. Hardness is correlated with strain and stress. The expressions discussed later are useful in determining the local variations in stress and strain from hardness measurement. It is a simple method compared to visioplasticity. One can estimate the forces required for a forming process. It helps in the choice of equipment, design of tooling and selection of lubricant for the particular process.  相似文献   
154.
根据7号高炉中控室供电状况,进行了供电平衡分析。调整两段负荷,使供电平衡安全。  相似文献   
155.
The Technical University of Catalonia (UPC) has been jointly working with the Asociación Nuclear Ascó-Vandellòs (ANAV) for a number of years in order to establish, qualify and use best estimate (BE) models for the reactors under the control of ANAV. ANAV is the consortium that is responsible for operation of the Ascó and Vandellòs-II reactors. The reactors are Westinghouse-design three-loop PWRs with an approximate electrical power of 1000 MW. The existing integral plant models for each plant are currently used for many different purposes among which are support of plant operation and control. Quite a number of studies have been done in order to improve both safety and plant competitiveness. Most of these dynamic analyses were carried out in relation to transients starting at nominal full power or at least, very close to full power. This paper develops a specific use of the Vandellòs-II plant model for operation and control support at low power involving new ranges of system actuation parameters. It also examines scenarios that are somewhat different from those typically analysed. The study starts showing the results of an assessment case, which is a start-up test and provides some additional qualification, and subsequently attempts to establish calculations to support both an improvement in feed water controls and to set up operating recommendations for low-load manual operation of feed water turbo-pump. Both results hopefully, will produce an outcome, which leads to an improvement in safety and reduces reactor trip probability.  相似文献   
156.
流量测量装置在自动化系统中应用非常广泛,在热力发电厂中流体的流量直接反映负荷高低、工作状况和运行效率。基于不同测量原理的装置其应用场合也不尽一样,在风量控制领域近几年也出现了十几种形式各异的产品,各种产品都有其自身的优缺点。分析了各种装置的原理及优缺点,重点介绍了一种新型的基于面积流测量原理的测量装置。  相似文献   
157.
张帆  张煦芳 《信息技术》2005,29(5):108-110
首先讨论了现有线路巡检模式的不足,然后提出了利用windows CE来构建线路巡检系统。分析了该系统的硬件平台之后,提出了线路巡检系统的体系结构,阐述了该系统应具有的软件功能。在实际应用中表明,该系统在线路巡检中有较强的推广价值。  相似文献   
158.
介绍了城市轨道交通直流牵引供电系统的构成,详细叙述了直流牵引供电系统的主要电气设备及其连接方法,以及系统的运行方式.另外,还简单介绍了系统配置的直流保护以及保护原理和保护作用.  相似文献   
159.
改善高平均功率固体激光器光束质量的研究   总被引:5,自引:0,他引:5  
本文首先概述了内含热透镜的激光谐振腔的分析方法,提出影响高平均功率固体激光器光束质量的主要因素是激光介质的热效应,尤其是非对称的热透镜象差。因此,改善光束质量的途径是补偿或修正透镜象差,使光束质量达到非相干多模振荡的理论值。  相似文献   
160.
热轧厂35kV右母线滤波装置优化   总被引:4,自引:0,他引:4  
周世民 《宝钢技术》1996,(6):21-23,45
热轧厂在轧制难度大的产品时,引进的35kV右母线滤波装置经常过流跳闸,并影响主变压器跳闸。通过现场测试,对过流跳闸原因进行综合分析,确定了设备优化改造对策。经1年多时间的实践考核证明改造是成功的。  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