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   201578篇
  免费   2315篇
  国内免费   644篇
电工技术   4112篇
综合类   145篇
化学工业   27485篇
金属工艺   7575篇
机械仪表   5549篇
建筑科学   4215篇
矿业工程   765篇
能源动力   4767篇
轻工业   14626篇
水利工程   1734篇
石油天然气   2876篇
武器工业   7篇
无线电   27678篇
一般工业技术   38071篇
冶金工业   45917篇
原子能技术   3583篇
自动化技术   15432篇
  2021年   1353篇
  2020年   1010篇
  2019年   1367篇
  2018年   2231篇
  2017年   2197篇
  2016年   2278篇
  2015年   1594篇
  2014年   2743篇
  2013年   8205篇
  2012年   4626篇
  2011年   6377篇
  2010年   5102篇
  2009年   5966篇
  2008年   6338篇
  2007年   6381篇
  2006年   5788篇
  2005年   5422篇
  2004年   5327篇
  2003年   5166篇
  2002年   4973篇
  2001年   5372篇
  2000年   4970篇
  1999年   5486篇
  1998年   15704篇
  1997年   10375篇
  1996年   7990篇
  1995年   5831篇
  1994年   5065篇
  1993年   5059篇
  1992年   3423篇
  1991年   3285篇
  1990年   3257篇
  1989年   3079篇
  1988年   2824篇
  1987年   2263篇
  1986年   2325篇
  1985年   2642篇
  1984年   2339篇
  1983年   2088篇
  1982年   1934篇
  1981年   2076篇
  1980年   1808篇
  1979年   1679篇
  1978年   1672篇
  1977年   2039篇
  1976年   2727篇
  1975年   1440篇
  1974年   1394篇
  1973年   1334篇
  1972年   1133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
24.
Open Shortest Path First (OSPF) traffic engineering (TE) is intended to bring long-awaited traffic management capabilities into IP networks, which still rely on today's prevailing routing protocols: OSPF or IS-IS. In OSPF, traffic is forwarded along, and split equally between, equal cost shortest paths. In this letter, we formulate the basic requirements placed on a practical TE architecture built on top of OSPF and present a theoretical framework meeting these requirements of practicality. The main contribution of our work comes from the recognition that coupled with an instance of the maximum throughput problem there exists a related inverse shortest-path problem yielding optimal OSPF link weights.  相似文献   
25.
26.
27.
This article investigates the asymptotic performance of single parity-check (SPC) product codes (PCs) from a decoding point of view. Specifically, the probability of bit error is bounded before and after the decoding of each dimension, similar to the analysis of "iterated codes" by Elias (1954). It is shown that the asymptotic probability of bit error can be driven to zero as the number of dimensions, and hence the block length, increases at signal-to-noise ratios (SNRs) within 2 dB of capacity over the additive white Gaussian noise (AWGN) channel.  相似文献   
28.
Passivated single damascene copper SiO2 damascene lines were evaluated in combination with TiSiN and Ta(N)/Ta diffusion barriers. Leakage current, breakdown and time-dependent dielectric breakdown properties were investigated on a wafer level basis for temperatures ranging between room temperature and 150 °C. It is found that the leakage performance of the wafers with a TiSiN barrier is better at room temperature, but at 150 °C the performance levels out with Ta(N)/Ta. Time-dependent dielectric breakdown measurements at 150 °C show that the lifetime of the interconnect is higher with the selected Ta(N)/Ta barrier than for TiSiN.  相似文献   
29.
The aim of this study was to evaluate the use of total coliforms (TC) and faecal coliforms (FC) using a membrane filtration method for precise monitoring of faecal pollution in Korean surface water. The samples were collected in Korea from both main rivers and their tributaries. Presumptive TC * FC were enumerated. The ratios of presumptive FC to TC were not constant, but varied widely, and TC were difficult to enumerate because of overgrowth by background colonies. For FC this was not the case. Seven hundred and three purified strains of presumptive TC * FC and their background colonies were biotyped using API 20E. Among 272 presumptive TC, non-faecal related species, Aeromonas hydrophila dominated (34.6%) and E. coli accounted for only 5.1%. In contrast, E. coli made up 89% of the 209 presumptive FC. Furthermore, of 164 background colonies on Endo Agar LES, 54.9% was A. hydrophila, while background colonies on m-FC Agar were few (58 strains), and despite their atypical colony appearance, most of them were biotyped as enteric bacteria. These results reveal that the detection of FC rather than TC using m-FC Agar is more appropriate for faecal pollution monitoring in eutrophicated surface water located in a temperate region.  相似文献   
30.
For realizing a naturalistic collaboration between the human and the robot, we have to establish the intention sharing from the series of motion data that are observed and exchanged between the human and the machine. In a word, this is a problem to detect "meanings" out of the digitized data stream. In this paper, we propose a novel approach based on semiosis, and present a method of interpreting bodily motions using recurrent neural networks called Elman networks. We made some experiments using the raw data acquired while a human performs a simple task of fetching objects by stretching and folding his/her arm, and demonstrate that the network can learn invariant features of the generalized motion concepts, classify the motion by referring to self-organized memory structure, and understand a task structure of the observed human bodily motion. These capabilities are essential for machine intelligence to establishing the human-robot shared autonomy, a new style of human-machine collaboration proposed in the area of robotics.  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