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   442453篇
  免费   16811篇
  国内免费   1402篇
电工技术   8328篇
综合类   322篇
化学工业   76102篇
金属工艺   16780篇
机械仪表   14201篇
建筑科学   10055篇
矿业工程   2166篇
能源动力   12488篇
轻工业   35172篇
水利工程   4534篇
石油天然气   7998篇
武器工业   17篇
无线电   55919篇
一般工业技术   93802篇
冶金工业   75748篇
原子能技术   9221篇
自动化技术   37813篇
  2022年   2697篇
  2021年   4231篇
  2020年   4440篇
  2019年   6953篇
  2018年   9556篇
  2017年   9760篇
  2016年   10686篇
  2015年   8020篇
  2014年   10789篇
  2013年   24916篇
  2012年   14055篇
  2011年   17556篇
  2010年   14683篇
  2009年   16189篇
  2008年   16025篇
  2007年   15473篇
  2006年   13920篇
  2005年   12327篇
  2004年   11744篇
  2003年   11623篇
  2002年   10979篇
  2001年   10749篇
  2000年   10124篇
  1999年   9996篇
  1998年   24463篇
  1997年   16803篇
  1996年   12858篇
  1995年   9566篇
  1994年   8409篇
  1993年   8423篇
  1992年   6089篇
  1991年   5726篇
  1990年   5704篇
  1989年   5343篇
  1988年   5063篇
  1987年   4455篇
  1986年   4325篇
  1985年   4845篇
  1984年   4454篇
  1983年   4017篇
  1982年   3674篇
  1981年   3747篇
  1980年   3455篇
  1979年   3340篇
  1978年   3350篇
  1977年   3773篇
  1976年   4869篇
  1975年   2866篇
  1974年   2674篇
  1973年   2743篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 172–176, May–June, 1994  相似文献   
64.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period  相似文献   
65.
A novel class of narrow-band tunable wavelength filters is proposed and evaluated. Wavelength selectivity of the proposed filters Is derived from the finite time response of an optical nonlinearity. The nonlinearity is gain saturation in semiconductor optical amplifier structures. The filters are shown to have very narrow passbands tunable over the entire semiconductor gain bandwidth. The key to filter implementation is a device configuration in which the wave-mixing products can be isolated from the amplified inputs. Three integrated optics compatible configurations are considered and shown to have high filter throughputs 34 to 180% and subangstrom bandwidths  相似文献   
66.
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   
67.
A fiber optic ring network, such as fiber distributed data interface (FDDI), can be operated over multiple wavelengths on its existing fiber plant consisting of point-to-point fiber links. Using wavelength division multiplexing (WDM) technology, FDDI nodes can be partitioned to operate over multiple subnetworks, with each subnetwork operating independently on a different wavelength, and inter-subnetwork traffic forwarding performed by a bridge. For this multiwavelength version of FDDI, which we refer to as wavelength distributed data interface (WDDI), we examine the necessary upgrades to the architecture of a FDDI node, including its possibility to serve as a bridge. The main motivation behind this study is that, as network traffic scales beyond (the single-wavelength) FDDI's information-carrying capacity, its multiwavelength version, WDDI, can gracefully accommodate such traffic growth. A number of design choices exist in constructing a good WDDI network. Specifically, we investigate algorithms using which, based on prevailing traffic conditions, partitioning of nodes into subnetworks can be performed in an optimized fashion. Our algorithms partition the nodes into subrings, such that the total traffic flow in the network and/or the network-wide average packet delay is minimized  相似文献   
68.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
69.
70.
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