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   5781篇
  免费   395篇
  国内免费   245篇
电工技术   285篇
综合类   944篇
化学工业   754篇
金属工艺   183篇
机械仪表   346篇
建筑科学   995篇
矿业工程   208篇
能源动力   92篇
轻工业   408篇
水利工程   184篇
石油天然气   206篇
武器工业   78篇
无线电   304篇
一般工业技术   292篇
冶金工业   338篇
原子能技术   17篇
自动化技术   787篇
  2024年   7篇
  2023年   29篇
  2022年   134篇
  2021年   128篇
  2020年   112篇
  2019年   88篇
  2018年   75篇
  2017年   137篇
  2016年   141篇
  2015年   160篇
  2014年   441篇
  2013年   268篇
  2012年   453篇
  2011年   455篇
  2010年   393篇
  2009年   404篇
  2008年   330篇
  2007年   417篇
  2006年   347篇
  2005年   362篇
  2004年   261篇
  2003年   239篇
  2002年   226篇
  2001年   169篇
  2000年   141篇
  1999年   111篇
  1998年   67篇
  1997年   63篇
  1996年   49篇
  1995年   48篇
  1994年   44篇
  1993年   29篇
  1992年   15篇
  1991年   17篇
  1990年   14篇
  1989年   9篇
  1988年   6篇
  1987年   8篇
  1986年   3篇
  1985年   5篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1979年   1篇
  1972年   1篇
  1961年   1篇
  1959年   1篇
  1956年   1篇
  1954年   1篇
排序方式: 共有6421条查询结果,搜索用时 31 毫秒
11.
综述了硫酸锆,碳酸锆产品的性质,生产技术及应用,收集整理了国内外部分厂家和公司该产品的化学指标与生产技术;介绍了“分步液相沉淀法”生产工艺,与“一步法”生产工艺相比,其具有流程短,投入少,操作简单,制造成本低等优点。  相似文献   
12.
The adoption of unified fracture mechanics terminology (UFMT) will promote efficient communication between specialists in different fields of fracture research, harmonization of national and international standards relating to fracture mechanics, and last but not least improvement of the existing methodology for teaching and education in fatigue and fracture. In this paper the definitions of some basic and related terms included in different standards on fracture mechanics terminology are confronted with one another. Alternative definitions of the same terms are offered. By this strategy the author tries to show that the definitions of basic and related terms appropriate for the UFMT should emerge as a consequence of harmonizing a crack model with an actual crack and then both taken together with a fracture model, laboratory test methods, and failure assessment codes.Published in Problemy Prochonsti, No. 1, pp. 17–29, January, 1996.This paper is published as a matter of discussion.  相似文献   
13.
电动自行车充电器自动检测系统设计   总被引:1,自引:0,他引:1  
介绍了基于PC虚拟仪器和VB环境的电动自行车充电器自动检测系统,阐述了系统检测原理,硬件结构设计及应用软件的编制方法,文中还给出了一个实用的恒流放电电子负载电路。  相似文献   
14.
电子化政府是运用信息技术创新政府服务的整合概念。建构电子政府已经成为世界范围内政府再造的新趋势。这里讨论了电子化政府基本模式及规划的内容和特点,并具体提出实现的模式、技术路径及方法。  相似文献   
15.
In order to develop a basic electrode with low fume and good usability, a uew slag system has been designed after analyzing several basic electrode slag systems. Then in view of uniform design method, arranging the experiment points by it, the influenced laws of the uew system coating compouents on the arc stability had been searched. In the formula, niue coating compouents were taken as independent variables and they were divided into six levels in all twenty-four experiments. The arc stability was taken as function and taken down the data when welding and then put them into the computer to be processed statistically. The analysis results give the mathematical model and trend diagrams between independent variables and the function. They indicate that the effects of many coating compouents on the arc stability are in the mutual form. The mutual effects between CaCO3 and BaF2, BaF2 and BaCO3 , increases the arc stability separately. While the mutual effects between CaF2 and iron powder, the square item of iron powder itself decreases the arc stability separately.  相似文献   
16.
以莱钢万力H型钢有限公司抽柱换梁工程为例,介绍行车梁拼装、柱加固拆除及托粱吊装前后的测量观测。  相似文献   
17.
An increasing number of avian flu cases in humans, arising primarily from direct contact with poultry, in several regions of the world have prompted the urgency to develop pandemic preparedness plans worldwide. Leading recommendations in these plans include basic public health control measures for minimizing transmission in hospitals and communities, the use of antiviral drugs and vaccination. This paper presents a mathematical model for the evaluation of the pandemic flu preparedness plans of the United States (US), the United Kingdom (UK) and the Netherlands. The model is used to assess single and combined interventions. Using data from the US, we show that hospital and community transmission control measures alone can be highly effective in reducing the impact of a potential flu pandemic. We further show that while the use of antivirals alone could lead to very significant reductions in the burden of a pandemic, the combination of transmission control measures, antivirals and vaccine gives the most 'optimal' result. However, implementing such an optimal strategy at the onset of a pandemic may not be realistic. Thus, it is important to consider other plausible alternatives. An optimal preparedness plan is largely dependent on the availability of resources; hence, it is country-specific. We show that countries with limited antiviral stockpiles should emphasize their use therapeutically (rather than prophylactically). However, countries with large antiviral stockpiles can achieve greater reductions in disease burden by implementing them both prophylactically and therapeutically. This study promotes alternative strategies that may be feasible and attainable for the US, UK and the Netherlands. It emphasizes the role of hospital and community transmission control measures in addition to the timely administration of antiviral treatment in reducing the burden of a flu pandemic. The latter is consistent with the preparedness plans of the UK and the Netherlands. Our results indicate that for low efficacy and coverage levels of antivirals and vaccine, the use of a vaccine leads to the greatest reduction in morbidity and mortality compared with the singular use of antivirals. However, as these efficacy and coverage levels are increased, the use of antivirals is more effective.  相似文献   
18.
主要研究了单层工业厂房可靠性模糊综合评判法的基本理论与实施方法.通过一工程实例,表明用这种定量方法来处理厂房可靠性评判中的大量不确定信息是科学、合理而又实用的.  相似文献   
19.
随着国家投资体制改革的不断深入,为进一步规范政府投资行为,提高投资效益,国家发展改革委对中央预算内基建投资计划的编制提出了一些新的、更加严格的要求。为尽快适应新要求,努力稳定中央水利基建投资计划规模,建议正确把握政策,界定公共财政投资的水利基建范畴;加快前期工作,增加政府投资项目储备:调整结构,把握中央水利基建投资的方向和重点;调整思路,努力稳定部门自身建设项目投资规模等。  相似文献   
20.
在天然河道中,河势演变虽具有一定的随机性,但仍有一定的规律可循,在一个河段内,一般可归纳出2-3条基本流路,为控制河势变化,需要选择出一条基本流路进行河道整治,当连续发生枯水期或洪水期时,部分河段的河势可能出现大的变化,为防止不利河势向下游传播,可修建较长的龙头弯道工程,利用龙头弯道工程分段调整,控导河势,保持河势稳定。  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