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   95437篇
  免费   7342篇
  国内免费   3921篇
电工技术   4100篇
技术理论   8篇
综合类   8783篇
化学工业   16432篇
金属工艺   1682篇
机械仪表   2131篇
建筑科学   14818篇
矿业工程   5650篇
能源动力   5575篇
轻工业   5675篇
水利工程   19161篇
石油天然气   7882篇
武器工业   212篇
无线电   1548篇
一般工业技术   4265篇
冶金工业   4239篇
原子能技术   1133篇
自动化技术   3406篇
  2024年   275篇
  2023年   1022篇
  2022年   1999篇
  2021年   2461篇
  2020年   2775篇
  2019年   2274篇
  2018年   2194篇
  2017年   2703篇
  2016年   3091篇
  2015年   3053篇
  2014年   5736篇
  2013年   5768篇
  2012年   7035篇
  2011年   7174篇
  2010年   5345篇
  2009年   5601篇
  2008年   4932篇
  2007年   6567篇
  2006年   6038篇
  2005年   5491篇
  2004年   4360篇
  2003年   3989篇
  2002年   3419篇
  2001年   2792篇
  2000年   2268篇
  1999年   1758篇
  1998年   1281篇
  1997年   1045篇
  1996年   809篇
  1995年   728篇
  1994年   539篇
  1993年   409篇
  1992年   334篇
  1991年   253篇
  1990年   201篇
  1989年   202篇
  1988年   124篇
  1987年   133篇
  1986年   107篇
  1985年   109篇
  1984年   96篇
  1983年   60篇
  1982年   36篇
  1981年   11篇
  1980年   20篇
  1979年   22篇
  1978年   8篇
  1977年   8篇
  1976年   9篇
  1951年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
分析了DFMC(大规模定制设计)关键技术及相关技术,提出了运用该项技术开发产品企业应作好的前期准备,研究了水利机械产品"大型移动启闭机"的定制开发。  相似文献   
82.
Visually perceiving an action may activate corresponding motor programs. This automatic motor activation can occur both for higher level (i.e., the goal of an action) and for lower level (i.e., the specific effector with which it is executed) aspects of an action. The authors used a tool-use action paradigm to experimentally dissociate priming effects for observing the target, the movement, or the target-to-movement mapping of a tool-use action. In 3 experiments, participants took turns in acting, observing the tool-use action of another person in trial n-1, and executing an action in trial n. Trial transitions from n-1 to n were manipulated in 4 conditions with (a) mapping repeated and movement and target changed, (b) target repeated and movement and mapping changed, (c) movement repeated and target and mapping changed, or (d) all components repeated. Results indicate priming effects for repeating the target-to-movement mapping (i.e., the action rule) of a tool-use action and suggest that a rather abstract action schema is activated during action observation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
83.
随着我国经济的迅速发展,能源消耗不断增加,节约能源、降低能源消耗势在必行,余热利用是节约能源的一个重要环节,冶金行业高炉冲渣水作为采暖热媒可以节约大量能源。  相似文献   
84.
不停车清洗预膜在2号高炉净循环水系统的应用   总被引:1,自引:0,他引:1  
张会刚 《梅山科技》2007,(2):16-17,22
循环冷却水系统长期运行过程中,由于多种因素影响,管道、阀门、水泵等设备产生结垢和腐蚀,为使水系统保持长期正常运行,减缓腐蚀结垢速度,需投加杀菌剂和阻垢缓蚀剂,2a进行一次清洗和预膜。主要介绍了2号高炉净循环水系统不停车清洗预膜的步骤、效果,并推荐在工况相似循环水系统中参考应用。  相似文献   
85.
Monitoring water quality in reservoirs with IRS-1A-LISS-I   总被引:1,自引:1,他引:0  
An attempt has been made to quantify the relationship between the variation in IRS-IA-LISS-I (Indian Remote Sensing Satellite-1A Linear Imaging Self-Scanning System) radiance data and field measured change in secchi disc depth. Secchi disc depth was measured for 47 predetermined sampling locations on reservoir surface water. At extinction depth (secchi depth), water samples were collected from all the sampling locations. Suspended sediments of eight locations representing various reaches of the reservoir were selected for mineralogical, particle size and optical properties analysis. The LISS-I radiance value in band 1 (0.45–0.52µm) band 2 (0-52–0.59 µm) and band 3 (0.62–0.68 µm) were used in a regression analysis. The absorption infrared band 4 (0.77–0.86 µm) was not included in the analysis. In these, the dependable variable was secchi depth (SD) and the LISS-I-radiance data was the estimator variable. Forty-seven data sets of 20 October 1988 from Tawa reservoir surface water were used to obtain an estimator equation for SD. The verification of the estimator equation was tested by applying it to a data set of 21 measurements of 28 September 1988 for this reservoir. The coefficient of correlation between observed and estimated values for the 28 September 1988 data set wasr=0.92 for SD, indicating that the equation could accurately predict the water clarity (SD) for this reservoir on new occasions from IRS-IA-LISS-I spectral data. It is shown that mineral composition and optical properties of suspended sediments influence the reflected radiance of water quality. It is concluded that IRS-IA-LISS-I data provide a useful means of mapping water quality in reservoir.  相似文献   
86.
In nuclear installations, tritiated water is generally produced in the process of detritiation of air circulating in the glove boxes. The goal of this work concerns enrichment of this tritiated water at low concentration by electrolysis. The choice of this electrolyzer was dictated by the passivity of selected materials to the radiolysis in low-level tritiated water and the selectivity of the method avoiding further elimination of tritiated water and moisture before release in environment. According to the results, it is feasible to treat non-negligible volume of low-level tritiated water using a cathodic palladium membrane coated on an ionic solid polymer membrane. Presence of a palladium black deposit on the palladium membrane improves effectiveness. Enrichment in tritiated water depends on the isotopic separation factor, thereby the current and the permeability values.  相似文献   
87.
Dendrimers have attracted immense attention during the last decade due to their interesting properties both from a basic and an applied research viewpoint. Encapsulation of metal nanoparticles for catalysis, drug delivery and light harvesting are only some applications of dendrimers that are breaking new ground. A novel application of dendrimer technology is described in the present paper that relates to industrial water treatment. Industrial water systems often suffer from undesirable inorganic deposits. These can form either in the bulk or on metallic surfaces, such as heat exchangers or pipelines. Silica (SiO2) scale formation and deposition is a major problem in high‐silica‐containing cooling waters. Scale prevention rather than removal is highly desired. In this paper, benchtop screening tests on various silica inhibition chemistries are reported, with emphasis on materials with a dendrimeric structure. Specifically, the inhibition properties of commercially available STARBURST® polyaminoamide (PAMAM) dendrimers generations 0.5, 1, 1.5, 2, and 2.5 are investigated in detail together with other commonly‐used scale inhibitors. Experimental results show that inhibition efficiency largely depends on structural features of PAMAM dendrimers such as generation number and nature of the end groups. PAMAM dendrimers are effective inhibitors of silica scale growth at 40 ppm dosage levels. PAMAM dendrimers also act as silica nucleators, forming SiO2–PAMAM composites. This occurs because the SiO2 formed by incomplete inhibition interacts with cationic PAMAM‐1 and ‐2. The general scope of silica formation and inhibition in industrial waters is also discussed. Copyright © 2005 Society of Chemical Industry  相似文献   
88.
The Technical University of Catalonia (UPC) has been jointly working with the Asociación Nuclear Ascó-Vandellòs (ANAV) for a number of years in order to establish, qualify and use best estimate (BE) models for the reactors under the control of ANAV. ANAV is the consortium that is responsible for operation of the Ascó and Vandellòs-II reactors. The reactors are Westinghouse-design three-loop PWRs with an approximate electrical power of 1000 MW. The existing integral plant models for each plant are currently used for many different purposes among which are support of plant operation and control. Quite a number of studies have been done in order to improve both safety and plant competitiveness. Most of these dynamic analyses were carried out in relation to transients starting at nominal full power or at least, very close to full power. This paper develops a specific use of the Vandellòs-II plant model for operation and control support at low power involving new ranges of system actuation parameters. It also examines scenarios that are somewhat different from those typically analysed. The study starts showing the results of an assessment case, which is a start-up test and provides some additional qualification, and subsequently attempts to establish calculations to support both an improvement in feed water controls and to set up operating recommendations for low-load manual operation of feed water turbo-pump. Both results hopefully, will produce an outcome, which leads to an improvement in safety and reduces reactor trip probability.  相似文献   
89.
Using qualitative data, Blom and Monk (2003) derived a theory of why people choose to personalise the appearance of their PCs and mobile phones. This paper describes some quantitative data that provide some support for, and some modifications to, the theory. Individuals having personal home pages were recruited to fill in a questionnaire that assesses dispositions to personalise and its effects. In addition the 82 home pages were inspected to assess the extent of personalisation. This correlated significantly with the dispositions 'Frequency of Use' and 'Knowledge of Personalisation'. The questionnaire items corresponding to effects were factor analysed. A four-factor solution suggested item groupings similar, but not identical, to those used in the theory. There are significant positive correlations between the extent of personalisation and cognitive effects and enduring emotional effects. The value of quantitative data for confirming and refining a qualitative theory is discussed.  相似文献   
90.
周秋珍 《节能》2005,(3):10-11,20
介绍了标准型直燃机的分类、原理及长庆至呼和浩特输气管道工程冷冻供热站的设计实例 ,重点论述了标准型直燃机在严寒地区使用的利弊  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