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   232148篇
  免费   18268篇
  国内免费   13123篇
电工技术   37884篇
技术理论   23篇
综合类   25647篇
化学工业   11022篇
金属工艺   7907篇
机械仪表   19593篇
建筑科学   19151篇
矿业工程   9135篇
能源动力   9535篇
轻工业   4859篇
水利工程   6929篇
石油天然气   6753篇
武器工业   3904篇
无线电   23788篇
一般工业技术   12045篇
冶金工业   7091篇
原子能技术   2685篇
自动化技术   55588篇
  2024年   773篇
  2023年   2086篇
  2022年   4109篇
  2021年   5249篇
  2020年   5658篇
  2019年   4104篇
  2018年   3759篇
  2017年   5396篇
  2016年   6405篇
  2015年   7521篇
  2014年   14422篇
  2013年   12278篇
  2012年   16874篇
  2011年   18208篇
  2010年   13788篇
  2009年   13812篇
  2008年   14123篇
  2007年   17907篇
  2006年   16203篇
  2005年   14597篇
  2004年   11984篇
  2003年   10740篇
  2002年   8128篇
  2001年   6796篇
  2000年   5623篇
  1999年   4652篇
  1998年   3519篇
  1997年   2811篇
  1996年   2529篇
  1995年   2140篇
  1994年   1770篇
  1993年   1250篇
  1992年   1036篇
  1991年   742篇
  1990年   587篇
  1989年   490篇
  1988年   360篇
  1987年   193篇
  1986年   122篇
  1985年   129篇
  1984年   120篇
  1983年   93篇
  1982年   75篇
  1981年   65篇
  1980年   58篇
  1979年   46篇
  1978年   35篇
  1977年   30篇
  1976年   23篇
  1959年   20篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
52.
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   
53.
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   
54.
主要介绍了热电厂近几年来在技术管理方面取得的主要工作经验,以及围绕生产经营开展科技创新所取得的成绩,并且针对当前形势,进一步提出了热电厂今后一个时期科技工作的指导思想、任务目标和措施。  相似文献   
55.
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   
56.
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   
57.
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   
58.
59.
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   
60.
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   
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