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   756261篇
  免费   8707篇
  国内免费   1764篇
电工技术   13868篇
综合类   692篇
化学工业   119187篇
金属工艺   30946篇
机械仪表   23788篇
建筑科学   17718篇
矿业工程   5341篇
能源动力   19265篇
轻工业   62817篇
水利工程   8862篇
石油天然气   18412篇
武器工业   59篇
无线电   81023篇
一般工业技术   152793篇
冶金工业   131177篇
原子能技术   18305篇
自动化技术   62479篇
  2021年   6913篇
  2019年   6561篇
  2018年   11502篇
  2017年   11624篇
  2016年   12320篇
  2015年   7886篇
  2014年   13105篇
  2013年   34698篇
  2012年   20309篇
  2011年   27019篇
  2010年   21943篇
  2009年   24462篇
  2008年   24865篇
  2007年   24503篇
  2006年   21311篇
  2005年   19455篇
  2004年   18375篇
  2003年   17871篇
  2002年   17472篇
  2001年   17008篇
  2000年   16365篇
  1999年   16194篇
  1998年   37869篇
  1997年   27685篇
  1996年   21498篇
  1995年   16500篇
  1994年   14924篇
  1993年   14560篇
  1992年   11258篇
  1991年   10980篇
  1990年   10789篇
  1989年   10580篇
  1988年   10171篇
  1987年   9074篇
  1986年   8854篇
  1985年   10145篇
  1984年   9361篇
  1983年   8908篇
  1982年   8034篇
  1981年   8281篇
  1980年   7876篇
  1979年   7935篇
  1978年   7825篇
  1977年   8873篇
  1976年   11249篇
  1975年   7080篇
  1974年   6793篇
  1973年   6881篇
  1972年   5908篇
  1971年   5528篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
This paper describes the distributed system, network and software architecture, the application development environment, the performance, and the early lessons learned on the ATM LAN testbed Mercuri established at the Honeywell Technology Center, to develop distributed multimedia technologies for real-time control applications. We have developed a client-server-based software architecture on Sun Sparcstation-2s connected by a Fore Systems' ASX-100 ATM switch, with video processing handled by Parallax's X Video cards. The architecture enables network-transparent applications and provides simple primitives for multimedia capture, display, transmission, storage, and retrieval. A real-time multimedia-in-the-loop control application was developed as the vehicle for testing the capabilities and performance of the network. Our test measurements focus on the end-user-level performance metrics such as message throughput and round-trip delay as well as video-frame jitter under no-load and load conditions. Our results show that the maximum burst throughput that can be supported at the user level is 48 Mb/s using AAL 5, while round-trip delays for 4-kbyte messages are about 3 ms. Our experience reveals a number of performance bottlenecks and open issues in using commercial ATM switches for practical applications. Our conclusions are outlined  相似文献   
995.
996.
We describe the sensitivity of sub-micron via integrity to high-temperature processing following via etch. It has been observed that thermal expansion of Al into the via hole, before tungsten deposition, may result in the fabrication of a deformed tungsten plug. Our results indicate that relaxation of the Al can give rise to stress-void formation under the tungsten plug. This may manifest itself either during electromigration stress or high-temperature storage. This mechanism represents a new reliability hazard for a tungsten-plug interconnect system  相似文献   
997.
The anticipated emergence of third-generation mobile systems, referred to as universal mobile telecommunication systems (UMTS), raises the problem of reconsidering the design of the databases destined to contain the user information. In particular, it is expected that the key concepts of the new database architectures will be high distribution and fast updating of information. So far, the problem of determining the most appropriate distributed database (DDB) architectures for third-generation mobile systems has not been widely dealt with in literature. This paper presents a methodology for evaluating hierarchical DDB architectures by means of an analytical model of the data querying operation. This methodology allows for structural alternatives, differing on account of the number of levels and branches in the hierarchy, to be evaluated in terms of query loads and mean response times, according to a given user mobility characterization and a given search protocol operation. By way of illustration, the paper discusses a case study, concerning a query operation arising from a location updating procedure and applied to a hierarchical tree-like DDB in which some structural alternatives are considered  相似文献   
998.
This article presents a fundamentally new method for controlling the position of an object in three-dimensional space by using a microinterferometer. This method assures high accuracy and efficiency. The method can be used for verifying accuracy of contact gauges in position-measuring machinery. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 17–18, April, 1996.  相似文献   
999.
The Warehouse Scheduling Problem is a deterministic multi-item inventory problem with a restriction on warehouse floor space available. We formulate a mixed integer nonlinear programming problem for the objective of minimizing long run inventory holding and order costs per unit of time. We integrate algorithms for staggering orders, described in companion papers, with a heuristic to choose the order sequences. The result is called Sequenced Staggering. We describe a new algorithm to generate order frequencies, called the powers-of-two-factor-of-three technique, as a generalization of Roundy's roundoff technique for powers-of-two policies. We report on a computational study of four hybrid algorithms for solving the warehouse scheduling problem, including the competing algorithm of Gallego, Queyranne, and Simchi-Levi. Based on these results, we recommend the combination of powers-of-two frequencies with Sequenced Staggering.  相似文献   
1000.
Translated from Izmeritel'naya Tekhnika, No. 11, pp. 66–67, November, 1994.  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