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   241073篇
  免费   19742篇
  国内免费   13867篇
电工技术   37274篇
技术理论   23篇
综合类   27184篇
化学工业   12158篇
金属工艺   7878篇
机械仪表   19413篇
建筑科学   21751篇
矿业工程   9870篇
能源动力   9309篇
轻工业   5202篇
水利工程   9697篇
石油天然气   7570篇
武器工业   3940篇
无线电   23555篇
一般工业技术   12409篇
冶金工业   8108篇
原子能技术   2527篇
自动化技术   56814篇
  2024年   822篇
  2023年   2189篇
  2022年   4485篇
  2021年   5614篇
  2020年   6054篇
  2019年   4399篇
  2018年   4026篇
  2017年   5608篇
  2016年   6698篇
  2015年   7849篇
  2014年   15273篇
  2013年   12800篇
  2012年   17856篇
  2011年   18938篇
  2010年   14367篇
  2009年   14423篇
  2008年   14676篇
  2007年   18632篇
  2006年   16737篇
  2005年   14920篇
  2004年   12353篇
  2003年   11093篇
  2002年   8464篇
  2001年   7112篇
  2000年   5828篇
  1999年   4740篇
  1998年   3523篇
  1997年   2869篇
  1996年   2546篇
  1995年   2179篇
  1994年   1800篇
  1993年   1242篇
  1992年   1033篇
  1991年   735篇
  1990年   583篇
  1989年   495篇
  1988年   353篇
  1987年   200篇
  1986年   129篇
  1985年   127篇
  1984年   109篇
  1983年   95篇
  1982年   82篇
  1981年   68篇
  1980年   53篇
  1979年   55篇
  1978年   39篇
  1977年   30篇
  1959年   45篇
  1955年   33篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
81.
Fluorans are given considerable attention as functional dyes for heat-and/or pressure-sensitive recording media. Numerous potential metal complexes were synthesised to prolong the life of coloured species. The protecting effect of these compounds against the photofading was examined on cellulose. It was found that the zinc or nickel salts of 3,5-dihydroxy-2-naphthoic acid and its derivatives can be applied as effective stabilisers against the fading of fluoran dyes.  相似文献   
82.
Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning.  相似文献   
83.
本文介绍一种基于VME总线的高速A/D缓冲系统的原理和结构。着重阐述了高速数据采集技术,高速FIFO缓冲技术,存储器总线切换技术,VME及PC/ISA总线接口技术在本系统中的成功应用。  相似文献   
84.
Electric power systems are expanding in size and complexity, and the requirement for the energy management system (EMS) is becoming more important. In this computer control system, a single control computer is used mainly as the primary computer and its software is very complicated because of its hugh number of small, quick tasks to obtain high response speed. Therefore, much effort is needed to develop and modify the programs, and the responsiveness of this centralized architecture varies greatly when many faults occur in the power system. This paper describes a new distributed architecture for the EMS. Distributed processors execute the functions cooperatively with periodic access to the common bulletin board database in which information about the power system exist. This architecture facilitates the software development and maintenance, and it also enhances the performance by the parallel processing of the distributed functions.  相似文献   
85.
86.
肖长虹 《广东化工》2002,29(5):38-40
瓶组气化站的建筑,结构设计关系到安全,满足使用要求和投资的大小,本文根据多年的实践和最新的有关设计规范的要求,阐述瓶组气化站建筑,结构设计的要点。  相似文献   
87.
本文介绍北京核电站模拟器硬件构成并分析其功能和特点。  相似文献   
88.
A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380  相似文献   
89.
用EGS4分析9MeV行波直线加速器屏蔽系统   总被引:1,自引:0,他引:1  
采用了国际上广泛使用的MonteCarlo模拟计算程序EGS4对海关集装箱检测系统用加速器屏蔽系统进行了辐射模拟分析,与实际测试数据进行分析、比较,解释了特殊剂量分布的原因,提出了系统改进的参考方案。  相似文献   
90.
When a fault occurs on transmission or distribution systems due to lightning or overvoltage, often an arc discharge occurs at the fault point. The arc discharge, which is caused by a fault current, has a high current, high temperature, strong light emission, etc., thus it sometimes causes heavy damages to electric power equipment. The arc discharge is influenced by the conditions around the arcs, i.e., gas, insulation materials, gap length, weather, etc. Also, the arc voltage along the arc column indicates the characteristics of the arc. If the voltage waveforms of the arcs caused by the fault on transmission or distribution systems are classified, it is possible to find the location and the equipment where the fault occurred. In this paper, the arc voltage data in 6-kV class XLPE cables and 6-kV class overhead lines are analyzed and an artificial neural network method is applied to classify the arc voltage waveforms. The results obtained from the six artificial neural networks developed show that the artificial neural network method is effective for classification of arc voltage waveforms if adequate input parameters are selected.  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