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   718866篇
  免费   7987篇
  国内免费   1346篇
电工技术   13125篇
综合类   699篇
化学工业   114306篇
金属工艺   28553篇
机械仪表   22609篇
建筑科学   16442篇
矿业工程   5048篇
能源动力   17768篇
轻工业   62253篇
水利工程   8417篇
石油天然气   17036篇
武器工业   65篇
无线电   75628篇
一般工业技术   142489篇
冶金工业   127584篇
原子能技术   17533篇
自动化技术   58644篇
  2021年   6508篇
  2019年   6256篇
  2018年   10669篇
  2017年   10897篇
  2016年   11390篇
  2015年   7180篇
  2014年   12152篇
  2013年   32408篇
  2012年   19100篇
  2011年   25823篇
  2010年   20654篇
  2009年   23109篇
  2008年   23520篇
  2007年   23341篇
  2006年   20492篇
  2005年   18413篇
  2004年   17617篇
  2003年   17210篇
  2002年   16755篇
  2001年   16294篇
  2000年   15710篇
  1999年   15498篇
  1998年   36399篇
  1997年   26184篇
  1996年   20383篇
  1995年   15725篇
  1994年   14135篇
  1993年   13835篇
  1992年   10818篇
  1991年   10314篇
  1990年   10349篇
  1989年   10109篇
  1988年   9732篇
  1987年   8688篇
  1986年   8524篇
  1985年   9711篇
  1984年   8940篇
  1983年   8439篇
  1982年   7687篇
  1981年   7812篇
  1980年   7540篇
  1979年   7521篇
  1978年   7443篇
  1977年   8276篇
  1976年   10477篇
  1975年   6718篇
  1974年   6410篇
  1973年   6529篇
  1972年   5584篇
  1971年   5198篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Carboxyl-terminated butadiene-acrylonitrile-rubber decreases modulus and yield stress of the studied epoxy but increases fracture toughness. The addition of glass bead compensates for the loss in modulus but has little effect on yield stress. However, it significantly contributes to the fracture toughness by providing additional mechanisms for toughening of both the unmodified and rubber-modified epoxy. For the toughened epoxies studied, fracture surfaces gave only limited information on fracture mechanisms since significant energy absorption also occurs in the material below the fracture surface. Suggestions for suitable material compositions for fiber composite matrices are given.  相似文献   
102.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
103.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented  相似文献   
104.
105.
Translated from Atomnaya Énergiya, Vol. 66, No. 6, pp. 423–424, June, 1989.  相似文献   
106.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
107.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  相似文献   
108.
109.
A method for fabricating single crystal blades that combines the techniques of seed crystals and selection is suggested. The method realizes the advantages of both techniques, i.e., the high structural perfection and the possibility of fabricating single crystals with specified spatial orientation. Metallographic and x-ray diffraction analyses are used to study the processes of nucleation of the single crystal structure of blade castings fabricated from high-temperature nickel alloys by the method of selection and seed crystals. A commercial process for fabricating cast single crystal turbine blades by the new method is suggested.  相似文献   
110.
An apparent decrease in total phosphorus concentrations of approximately 4.l μgP/L has been reported recently for the spring values of 1977 and 1978 in Lake Ontario. Investigation of the loading reduction for this period independent of sedimentation factors can account for only 10% of the change. The results indicate that changes in the sedimentation rate of total phosphorus during this period offer an explanation for the majority of the change in concentration.  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