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   235070篇
  免费   19628篇
  国内免费   12958篇
电工技术   34897篇
技术理论   22篇
综合类   26011篇
化学工业   11063篇
金属工艺   7665篇
机械仪表   18827篇
建筑科学   21038篇
矿业工程   17573篇
能源动力   8839篇
轻工业   4975篇
水利工程   6627篇
石油天然气   6696篇
武器工业   3895篇
无线电   21947篇
一般工业技术   11921篇
冶金工业   8522篇
原子能技术   2350篇
自动化技术   54788篇
  2024年   777篇
  2023年   2096篇
  2022年   4320篇
  2021年   5551篇
  2020年   6126篇
  2019年   4235篇
  2018年   3893篇
  2017年   5455篇
  2016年   6508篇
  2015年   7743篇
  2014年   14864篇
  2013年   12657篇
  2012年   17827篇
  2011年   18728篇
  2010年   14129篇
  2009年   14028篇
  2008年   14367篇
  2007年   18087篇
  2006年   16207篇
  2005年   14450篇
  2004年   11864篇
  2003年   10739篇
  2002年   8088篇
  2001年   6824篇
  2000年   5657篇
  1999年   4558篇
  1998年   3434篇
  1997年   2811篇
  1996年   2456篇
  1995年   2095篇
  1994年   1743篇
  1993年   1172篇
  1992年   986篇
  1991年   717篇
  1990年   578篇
  1989年   473篇
  1988年   338篇
  1987年   197篇
  1986年   122篇
  1985年   123篇
  1984年   104篇
  1983年   95篇
  1982年   71篇
  1981年   64篇
  1980年   51篇
  1979年   45篇
  1978年   34篇
  1977年   28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 15 毫秒
41.
简要介绍了蒸汽发生器水位控制系统的运行方式和试验方法。试验项目包括旁通阀控制试验、主给水阀控制试验和旁通阀与主给水阀的切换试验。文中给出了试验结果,即在液位扰动和核动率扰动时,蒸汽发生器液位的变化过程。经过两个月的运行和瞬态试验,证明蒸汽发生器水位控制系统满足设计要求。  相似文献   
42.
Extracted and unextracted black cherry (Prunus serotina), red oak (Quercus rubra), and red pine (Pinus resinosa) wood specimens were exposed to artificial weathering, and their discoloration process was investigated to obtain basic understanding on the role of wood extractives in the weathering of hardwoods and softwoods. Color measurements were made with a spectrometer according to ISO 2470 standards, using the CIELAB system. Results obtained showed that the rate of whiteness was not significantly affected by extractives removed with organic solvents, but were significantly affected when organic solvent extraction was followed by water extraction. The total discoloration rate had the same pattern, and chromaticity coordinates were less affected by wood extractives. These results confirm the hypothesis that some extractives contained in wood act as antioxidants and are able to provide some protection to wood surfaces against weathering degradation. However, more work is needed to understand the chemistry and mechanism of action of these extractives so as to develop any practical use for this property. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 425–434, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20248  相似文献   
43.
本文介绍了煤炭企业管理的激励方式以及激励机制的具体运用。  相似文献   
44.
龙新良 《煤炭技术》2003,22(2):49-51
总结了实际工作中防突管理的经验和问题 ,探讨了科学理论与具体实际的有机结合与统一 ,采取针对性强的有效措施 ,确保突出矿井的安全生产  相似文献   
45.
The Rainbow net simulation technique is applied to modelling the impact of system load and fault handling on the availability of a fault-tolerant multiprocessor architecture. Rainbow nets are described along with the motivation for creating this modelling technique. A Rainbow net fault-handling model is created for the fault-tolerant multiprocessor architecture and the topology is shown to remain constant in size, independent of the number of processor, memory and I/O elements configured in the system. Simulation is performed with a varying load in terms of the number of active jobs the system must support. Results are given showing how the fault-tolerant capability varies with load. Two new metrics for evaluating fault tolerance are introduced; namely full fault-tolerability and partial fault-tolerability. They are based on simple observations in the model.  相似文献   
46.
Power system control equipment needs higher sensitivity and operational reliability. Advanced voltage control equipment is needed for reducing the frequency of tap changes and improving the characteristics (the relationship between the actual voltage and reference voltage) of the voltage to meet today's power system requirements. However, these objectives are in a trade-off relationship. Studies of voltage control derived from a knowledge base suitable for electric power systems can satisfy these objectives using fuzzy inference. Compared with corresponding conventional equipment, the new equipment improved the deviation of 30 min average voltage of 30 percent. This paper describes the design concept of new voltage control equipment using fuzzy inference. In addition, field test results are described along with rules of fuzzy inference, membership functions, and the deviation of 30 min average voltage through detailed simulation.  相似文献   
47.
介绍了用自顶向下的结构化方法进行科研项目管理信息系统设计的过程。该系统的应用节省了大量人力、物力和财力,提高了企业科研项目管理水平。  相似文献   
48.
In today's competitive business environment, it is important that customers are able to obtain their preferred items in the shops they visit, particularly for convenience store chains such as 7–Eleven where popular items are expected to be readily available on the shelves of the stores for buyers. To minimize the cost of running such store chains, it is essential that stocks be kept to a minimum and at the same time large varieties of popular items are available for customers. In this respect, the replenishment system needs to be able to cope with the taxing demands of minimal inventory but at the same time keeping large varieties of needed items. This paper proposes a replenishment system which is able to respond to the fluctuating demands of customers and provide a timely supply of needed items in a cost–effective way. The proposed system embraces the principle of fuzzy logic which is able to deal with uncertainties by virtue of its fuzzy rules reasoning mechanism, thereby leveraging the responsiveness of the entire replenishment system for the chain stores. To validate the feasibility of the approach, a case study has been conducted in an emulated environment with promising results.  相似文献   
49.
苗青云 《山西建筑》2003,29(15):69-70
介绍了热水采暖系统运行及调整的注意事项,分析了立支管阀门、集气罐的作用,提出了使热水采暖系统的调节和集排气操作达到理想程度的有效措施,以实现良好的供暖效果。  相似文献   
50.
现场总线控制系统浅谈   总被引:1,自引:0,他引:1  
简述了现场总线控制系统的结构及其显优点。现场总线控制系统的结构包括:主控器、总线接口、电源、输入/输出接点、总线电揽和终端电阻。另外对其显优点做了逐一介绍。现场总线控制系统可在工业自动化控制系统中推广应用。  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