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   168579篇
  免费   1174篇
  国内免费   193篇
电工技术   2553篇
综合类   119篇
化学工业   26623篇
金属工艺   9471篇
机械仪表   5715篇
建筑科学   3008篇
矿业工程   1887篇
能源动力   2704篇
轻工业   8833篇
水利工程   2729篇
石油天然气   8692篇
武器工业   12篇
无线电   14493篇
一般工业技术   38259篇
冶金工业   27815篇
原子能技术   6933篇
自动化技术   10100篇
  2018年   2980篇
  2017年   3093篇
  2016年   3344篇
  2015年   1673篇
  2014年   2957篇
  2013年   6342篇
  2012年   4312篇
  2011年   5399篇
  2010年   4420篇
  2009年   4894篇
  2008年   4942篇
  2007年   4869篇
  2006年   4144篇
  2005年   3821篇
  2004年   3638篇
  2003年   3522篇
  2002年   3451篇
  2001年   3464篇
  2000年   3363篇
  1999年   3214篇
  1998年   7022篇
  1997年   5155篇
  1996年   3823篇
  1995年   2917篇
  1994年   2593篇
  1993年   2720篇
  1992年   2254篇
  1991年   2305篇
  1990年   2410篇
  1989年   2315篇
  1988年   2314篇
  1987年   2191篇
  1986年   2246篇
  1985年   2292篇
  1984年   2206篇
  1983年   2138篇
  1982年   1980篇
  1981年   2193篇
  1980年   2053篇
  1979年   2269篇
  1978年   2431篇
  1977年   2432篇
  1976年   3096篇
  1975年   2244篇
  1974年   2307篇
  1973年   2342篇
  1972年   2156篇
  1971年   1911篇
  1970年   1701篇
  1969年   1632篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The paper describes the synthesis of N-2/4-toluyl methacrylatoethyl carbamates using 2/4-toluyl isocyanate and 2-hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N-4-toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using 1H-NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry.  相似文献   
992.
Mendeleev All-Union Metrology Research Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 393–397, November 1992.  相似文献   
993.
994.
995.
An implementation for a fast public-key cryptosystem   总被引:9,自引:0,他引:9  
In this paper we examine the development of a high-speed implementation of a system to perform exponentiation in fields of the form GF(2 n ). For sufficiently large n, this device has applications in public-key cryptography. The selection of representation and observations on the structure of multiplication have led to the development of an architecture which is of low complexity and high speed. A VLSI implementation has being fabricated with measured throughput for exponentiation for cryptographic purposes of approximately 300 kilobits per second.  相似文献   
996.
A high protein, groundnut-based powder reconstitutable into a milk-like beverage was packed in polyethylene bags and in lacquered tin cans, and stored at both room temperature (25 ± 2°C) and in a domestic refrigerator (5 ± 2°C) for 60 days. Storage stability was evaluated by analysing periodically for changes in physical characteristics, proximate composition, and development of browning and rancidity, and assessing moisture sorption characteristics. Protein, lipid, total soluble sugars, peroxide value, total carbonyls and extinction values of the ethanolic extract remained practically constant during storage. The isotherm curves exhibited the characteristic sigmoidal shape typical of high protein foods. There was a greater increase in density, hygroscopicity and wettability in polyethylene-packed samples at both temperatures suggesting that the lacquered tin can leads to better keeping quality for this product.  相似文献   
997.
A method has been developed for assay of deoxynivalenol (DON) and its metabolite desepoxideoxynivalenol (DOM-1) in animal excrements with the use of reversed-phase high-performance liquid chromatography with UV-detection (218 nm). The method includes purification in the mini-column with activated carbon and aluminium oxide. The detection limit was 50 ng/g, relative standard deviation--0.05-0.1, the degree of toxin isolation--76-89%. DON isolated from Fusarium macroceras, strain 579a, cultivated in rice under laboratory conditions, and DOM-1 obtained as a result of DON incubation with the contents of the beef first stomach, were used in the study. The structure of toxins isolated has been proved by the mass-spectrometry method. The method developed by the authors was used in the study of DON metabolism in vivo in monkeys.  相似文献   
998.
999.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 1–6, October, 1992.  相似文献   
1000.
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