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   315510篇
  免费   5567篇
  国内免费   2060篇
电工技术   6707篇
技术理论   4篇
综合类   2069篇
化学工业   49874篇
金属工艺   13611篇
机械仪表   10515篇
建筑科学   9048篇
矿业工程   2689篇
能源动力   7536篇
轻工业   28048篇
水利工程   3712篇
石油天然气   9030篇
武器工业   232篇
无线电   34507篇
一般工业技术   60066篇
冶金工业   52599篇
原子能技术   7832篇
自动化技术   25058篇
  2021年   3439篇
  2020年   2707篇
  2019年   2763篇
  2018年   4575篇
  2017年   4616篇
  2016年   4752篇
  2015年   3698篇
  2014年   5651篇
  2013年   13661篇
  2012年   8571篇
  2011年   11127篇
  2010年   9203篇
  2009年   10130篇
  2008年   10495篇
  2007年   10278篇
  2006年   9294篇
  2005年   8568篇
  2004年   7612篇
  2003年   7332篇
  2002年   7477篇
  2001年   7240篇
  2000年   6801篇
  1999年   6925篇
  1998年   15245篇
  1997年   11444篇
  1996年   8930篇
  1995年   6837篇
  1994年   6167篇
  1993年   5961篇
  1992年   4622篇
  1991年   4529篇
  1990年   4369篇
  1989年   4362篇
  1988年   4295篇
  1987年   3638篇
  1986年   3619篇
  1985年   4181篇
  1984年   3974篇
  1983年   3629篇
  1982年   3426篇
  1981年   3566篇
  1980年   3432篇
  1979年   3368篇
  1978年   3446篇
  1977年   3923篇
  1976年   5037篇
  1975年   3158篇
  1974年   3007篇
  1973年   3024篇
  1972年   2651篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Communication network design is becoming increasingly complex, involving making networks more usable, affordable, and reliable. To help with this, we have proposed an expert network designer (END) for configuring, modeling, simulating, and evaluating large structured computer networks, employing artificial intelligence, knowledge representation, and network simulation tools. We present a neural network/knowledge acquisition machine-learning approach to improve the END's efficiency in solving the network design problem and to extend its scope to acquire new networking technologies, learn new network design techniques, and update the specifications of existing technologies  相似文献   
43.
Single-phase voltage source power converters (VSCs) under consideration are AC-DC current-controlled boost-type power converters with bidirectional power-handling capability. Equivalence between two series-connected two-level power converters and a single three-level power converter is considered here. Further considered is the series operation of three-level power converters. Simulation results and experimental verification for both are provided. Economical configurations of three-level power converters leading to multilevel waveforms are presented thereafter  相似文献   
44.
For part I see, ibid., p. 134, 1998. The basic approach outlined in the previous article is applied to the difficult problem of computing the optical modes of a vertical-cavity surface-emitting laser. The formulation utilizes a finite difference equation based upon the lowest order term of an infinite series solution of the scalar Helmholtz equation in a local region. This difference equation becomes exact in the one-dimensional (1-D) limit, and is thus ideally suited for nearly 1-D devices such as vertical-cavity lasers. The performance of the resulting code is tested on both a simple cylindrical cavity with known solutions and an oxide-confined vertical-cavity laser structure, and the results compared against second-order-accurate code based upon Crank-Nicolson differencing  相似文献   
45.
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   
46.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。  相似文献   
47.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information technologies and systems by the Ukrainian State Committee, of Science and Technology.  相似文献   
48.
The study presents a hypothesis on how randomness could be simulated by human subjects. Three sources of deviation from randomness are predicted: (1) the preferred application of overlearned production schemata for producing sequences of digits, (2) a wrong concept of randomness, and (3) the impossibility to monitor for redundancies of higher- than those of first-order. Deviations of random generation of digits produced by healthy subjects, patients with chronic frontal lobe damage, and patients with Parkinson's disease from random sequences produced by a computer program can be explained by the differential influence of these factors. Whereas incorrect concepts of randomness and limits on monitoring capacity distinguished all sequences produced by humans from actual random sequences, persistence on a single production strategy distinguished brain-damaged patients from controls. Random generation of digits appears to be a theoretically transparent and clinically useful test of executive function.  相似文献   
49.
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   
50.
研究了两种比活度的131Ⅰ-MIBG在正常及利血平抑制后在鼠体内的分布,结果表明:注射后4h,正常鼠心肌对3.22TBq/g的MIBG摄取为9.08%ID/g,明显高于对18.5GBq/g的摄取(4.87%ID/g)。计算表明,比活度主要影响了鼠心肌交感神经囊泡内摄取,而与囊泡外摄取无关.当MIBG用于心肌显像时,高比活度的MIBG有利于诊断。  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