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   166229篇
  免费   10970篇
  国内免费   4413篇
电工技术   6685篇
技术理论   11篇
综合类   6688篇
化学工业   30749篇
金属工艺   8080篇
机械仪表   10195篇
建筑科学   9851篇
矿业工程   3111篇
能源动力   5426篇
轻工业   10924篇
水利工程   2016篇
石油天然气   6393篇
武器工业   704篇
无线电   22455篇
一般工业技术   25679篇
冶金工业   10292篇
原子能技术   2004篇
自动化技术   20349篇
  2024年   494篇
  2023年   2372篇
  2022年   3850篇
  2021年   5593篇
  2020年   4220篇
  2019年   3885篇
  2018年   4568篇
  2017年   4913篇
  2016年   4855篇
  2015年   5309篇
  2014年   7192篇
  2013年   9570篇
  2012年   10077篇
  2011年   11410篇
  2010年   9334篇
  2009年   9348篇
  2008年   9227篇
  2007年   8129篇
  2006年   8238篇
  2005年   7273篇
  2004年   5402篇
  2003年   4831篇
  2002年   4308篇
  2001年   4006篇
  2000年   3976篇
  1999年   4416篇
  1998年   4662篇
  1997年   3657篇
  1996年   3194篇
  1995年   2570篇
  1994年   2080篇
  1993年   1673篇
  1992年   1298篇
  1991年   1040篇
  1990年   881篇
  1989年   772篇
  1988年   619篇
  1987年   485篇
  1986年   347篇
  1985年   302篇
  1984年   216篇
  1983年   154篇
  1982年   130篇
  1981年   105篇
  1980年   83篇
  1979年   73篇
  1978年   61篇
  1977年   72篇
  1976年   122篇
  1973年   37篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
通过几个典型事例的分析、判断和处理,介绍了该厂怎样利用91l型数采器对2D12—100/8型空压机运行状态进行监测,以预报早期故障,为设备检修提供指导.  相似文献   
62.
The temperature dependence characteristics of hydrogenated amorphous silicon thin-film transistors were investigated. The results indicate that as the temperature was increased, the threshold voltage and the field-effect mobility were first increased, and then decreased, which may be controlled by different mechanisms at low and high temperatures. In addition, if the temperature was higher than 420 K, the Fermi level was promoted to the degenerate-like states, the current channel always existed due to the temperature effect, and the threshold voltage became negative.  相似文献   
63.
This newsletter provides information on past and upcoming events related to the IEEE Computer Society's Test Technology Technical Council and the test community.  相似文献   
64.
Double-step generation of ellipses   总被引:4,自引:0,他引:4  
The principle of double-step incremental generation of nonparametric curves on a discrete plane is used to develop a double-step algorithm for scan converting ellipses in sixteen separate segments. The algorithm iterates only half as many times as current algorithms, while each iteration demands the same number of operations or slightly fewer operations than M. Pitteway's (1967, 1985) algorithm (previously the fastest one). This marked gain in the speed of scan conversion is due to the fact that the middle pixel in a two-step increment is obtained without computation  相似文献   
65.
The secondary effluent from municipal plants in Korea generally represents higher BOD with lower SS. Therefore, more soluble forms of organics and NH4-N need to be removed to improve its effluent for reuse. In this study reuse possibility of secondary effluent and CSO (combined sewer overflow) using BAF (biological aerated filter) was evaluated. The tertiary application with 1.2 h EBCT, SS, BOD and COD showed stable concentrations less than 1.3, 1.3 and 6.2 mg/L, respectively. Nitrogen could be nitrified even at 7 degrees suggesting BAF can be used for a water reuse method as well as an effective add-on facility in cold regions. However, BAF was not stable with CSO application at increased flow rates suggesting CSO must be equalised prior to application. Disinfection was necessary even during normal weather conditions.  相似文献   
66.
本文介绍β放射性气体浓度计的一种新的分度方法——泄漏元件排气法。其特点是一只元件可分度放射性气体浓度计的许多读出数(甚至是几个量程),操作方便。  相似文献   
67.
68.
The mode of fuel management of the HTR-10 was studied, including the simulation of the fuel shuffling process and the measurement of the burnup of a fuel element. The prior consideration was the design of the equilibrium state. Based on this the fuel loading of the initial core and the fuel shuffling mode from the initial core through the running-in phase into the equilibrium state were studied. The code system VSOP was used for the physical layout of the HTR-10 at the equilibrium state and in the running-in phase. For the equilibrium state, in order to lessen the difference between the peak and the average burnup, 5-fuel-passage-through-the-core was chosen for the fuel management. The average burnup of the spent fuel for the equilibrium core is 80 000 MWd t−1, and the peak value of it is less than 100 000 MWd t−1 when the burnup of the recycled fuel element is under 72 000 MWd t−1. The mixture of fuel element and graphite element was used for the initial core loading, the volume fractions of the fuel and the graphite elements were 0.57 and 0.43, respectively. During the running-in phase, the volume fraction of graphite will decrease with the fresh fuel elements being loaded from the top of the core and the graphite elements discharged from the bottom of the core. The fuel shuffling mode is similar to that of the equilibrium state. The burnup limit of recycled fuel element is also 72 000 MWd t−1 and the peak burnup is less than 100 000 MWd t−1. Finally the core will be full of fuel elements with a certain profile of burnup and reaches the equilibrium state. According to the characteristics of the pebble-bed high temperature gas-cooled reactor, a calibrating method of concentration of 137Cs was proposed for the measurement of fuel burnup.  相似文献   
69.
The tool portfolio of a plant refers to the makeup, in quantity and type, of processing machines in the plant. It is determined by taking into consideration the future trends of process and machine technologies and the forecasts of product evolution and product demands. Portfolio planning is also a multicriteria decision-making task involving tradeoffs among, investment cost, throughput, cycle time, and risk. Tool portfolio planning is a complex task that has strong bearing on manufacturing efficiency. In the first part of this paper, a multicriteria economic decision model is presented for optimal configuration. of the portfolio and to determine the optimal factory loading. The second and third parts of the paper contain applications of the model. If plants are closely located or have a twin-plant design, portfolio planning at multiple plants can be integrated to enhance the overall effectiveness of portfolios. In the second part, a novel methodology for arbitrating capacity backup between plants is described. Because the economic model is constructed upon a valuation of both cycle time and throughput, it is a suitable method for the evaluation of cycle time reduction projects. The application procedure is outlined in the third part.  相似文献   
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