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   619751篇
  免费   10294篇
  国内免费   2993篇
电工技术   13279篇
技术理论   5篇
综合类   3457篇
化学工业   99231篇
金属工艺   26510篇
机械仪表   21706篇
建筑科学   16320篇
矿业工程   6066篇
能源动力   16100篇
轻工业   49420篇
水利工程   7804篇
石油天然气   18732篇
武器工业   435篇
无线电   65914篇
一般工业技术   122469篇
冶金工业   98469篇
原子能技术   15331篇
自动化技术   51790篇
  2022年   5348篇
  2021年   7771篇
  2020年   5674篇
  2019年   6700篇
  2018年   10833篇
  2017年   11175篇
  2016年   11409篇
  2015年   8104篇
  2014年   12916篇
  2013年   29169篇
  2012年   19037篇
  2011年   24646篇
  2010年   20138篇
  2009年   21645篇
  2008年   21849篇
  2007年   21464篇
  2006年   19131篇
  2005年   17173篇
  2004年   15523篇
  2003年   15016篇
  2002年   14500篇
  2001年   13830篇
  2000年   13510篇
  1999年   13475篇
  1998年   28800篇
  1997年   21014篇
  1996年   16610篇
  1995年   12879篇
  1994年   11546篇
  1993年   11071篇
  1992年   8693篇
  1991年   8397篇
  1990年   8224篇
  1989年   7954篇
  1988年   7646篇
  1987年   6857篇
  1986年   6627篇
  1985年   7446篇
  1984年   6751篇
  1983年   6473篇
  1982年   5805篇
  1981年   5924篇
  1980年   5647篇
  1979年   5740篇
  1978年   5668篇
  1977年   6188篇
  1976年   7695篇
  1975年   5111篇
  1974年   4905篇
  1973年   4982篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included  相似文献   
62.
63.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
64.
65.
The process of combustion of homogeneous and heterogeneous nongasifying and slightly gasifying systems over the range of a number of parameters characterizing the reactive composition and the conditions for the arrangement of the combustion process is studied by using thermocouple and optical methods. The regions of the implementation of different combustion regimes, namely, steady, pulsating, multiple-point, and spin, are determined experimentally.Institute of Structural Macrokinetics, Russian Academy of Sciences, Chernogolovka. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 4, pp. 407–411, October, 1993.  相似文献   
66.
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   
67.
An experimental and theoretical analysis of the nonlinear coupling mechanism between the two solitary pulses circulating in a two-color femtosecond laser is presented. Two operation regimes; synchronized; and nonsynchronized; and a hysteresis of the transition between the two regimes are clearly observed; while independent modelocking and tunability of the output pulse trains is found in both regimes. Pulses in the range from 15 to 100 fs are synchronized with a timing jitter below 2 fs. The combined effects of cross-phase modulation and negative group velocity dispersion are shown to be responsible for the strong pulse correlation in the synchronized regime. Our experimental observations are in agreement with numerical simulations, thus confirming the theoretical model  相似文献   
68.
69.
70.
A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated power converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated power converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the power converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated power converter most suitable for a given application and in the design of this power converter with minimum switch stresses, high power density, and low cost  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