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   19551篇
  免费   1809篇
  国内免费   798篇
电工技术   988篇
技术理论   2篇
综合类   1422篇
化学工业   3198篇
金属工艺   3499篇
机械仪表   858篇
建筑科学   844篇
矿业工程   1719篇
能源动力   439篇
轻工业   750篇
水利工程   250篇
石油天然气   345篇
武器工业   92篇
无线电   796篇
一般工业技术   1534篇
冶金工业   3842篇
原子能技术   195篇
自动化技术   1385篇
  2024年   39篇
  2023年   176篇
  2022年   421篇
  2021年   581篇
  2020年   541篇
  2019年   444篇
  2018年   438篇
  2017年   511篇
  2016年   715篇
  2015年   702篇
  2014年   1179篇
  2013年   1227篇
  2012年   1422篇
  2011年   1469篇
  2010年   1089篇
  2009年   943篇
  2008年   842篇
  2007年   1241篇
  2006年   1185篇
  2005年   1026篇
  2004年   880篇
  2003年   793篇
  2002年   718篇
  2001年   592篇
  2000年   492篇
  1999年   404篇
  1998年   348篇
  1997年   295篇
  1996年   261篇
  1995年   236篇
  1994年   193篇
  1993年   132篇
  1992年   126篇
  1991年   81篇
  1990年   85篇
  1989年   75篇
  1988年   61篇
  1987年   30篇
  1986年   27篇
  1985年   24篇
  1984年   23篇
  1983年   8篇
  1982年   20篇
  1981年   14篇
  1980年   10篇
  1978年   7篇
  1977年   5篇
  1974年   6篇
  1973年   3篇
  1966年   3篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
101.
化学模式识别法在钢铁工业中的若干应用   总被引:1,自引:0,他引:1  
本文涉及一种崭新的非函数数据处理法及其在工业诊断和优化中的应用。并对其进行要因分析和优化决策的原理作了介绍。结合钢铁工业生产中的实例进行了分析。还探讨了该方法在钢铁工业中应用的意义。  相似文献   
102.
张昕 《石油机械》1998,26(4):14-15,22
为提高抽油机减速器齿轮铸件的机械性能,提出以Sn代替Mo作为合金元素,并通过试验确定了合理的Si、Cu、Sn的加入量。指出Si加入量应控制在1.9%-2.1%范围内,同时加入0.36%~0.9%的Cu和0.025%~0.07%的Sn,可保证球铁的强度和延伸率都满足QT700-2的要求。鉴于试件与实际铸件的表面硬度有一定的差值,为提高铸件表面硬度,进行了余热正火试验,并给出了铸件在铸型内的时间-冷却温度曲线。最后根据球铁化学成分的选择结果,进行了齿轮生产试验。  相似文献   
103.
大型离心复合球墨铸铁轧辊的生产   总被引:1,自引:0,他引:1  
简述了我公司为舞阳铜厂试制4200mm厚板轧机离心复合球墨铸铁轧辊的性能要求、内外层双重金属铸造工艺参数的选择及整个铸造生产工艺过程。  相似文献   
104.
Montmorillinite clays, modified with either Zn(II) or Fe(III) chlorides have been used to catalyze the Friedel-Crafts alkylation of thiophene. High yields (ca. 80%) of 2- and 3-benzylthiophene mixtures were obtained using either catalyst in chlorobenzene or nitrobenzene solvent at 80°C. The ratio of 2–3-products was found to be controlled by their relative stability. Reactions were most rapid in nitrobenzene solution (<5 min) and resulted in formation of the 2-isomer as the only mono-substituted product. This is believed to be the first example in which an alkylation of thiophene has been limited to one regio-isomer.  相似文献   
105.
The paper describes a new powder composition specially developed for selective laser sintering (SLS). The aim is to obtain a ferro powder that can be sintered without need for a (sacrificial) polymer binder and that results in quasi dense parts that do not need any post-processing like furnace sintering, infiltration or HIP. The powder is a mixture of different types of particles (Fe, Cu, Ni and Fe3P). The composition and mixture ratio are justified by using phase diagrams. The powder has been tested using an own developed Nd: YAG SLS machine. The influence of process parameters (laser power, scan velocity, scan spacing and scan strategy) and the microstructural characteristics have been investigated. Attention is devoted to the binding mechanism (liquid phase sintering, through melting) and to the quality of resulting parts (density, balling effect,…).  相似文献   
106.
Quantitative gas chromatographic analysis of the volatile aroma components has been used as an objective measure of the effects of maturity at harvest, ripeness and storage on the aroma volatiles of kiwifruit. Increasing ripeness is associated with a rapid increase in the levels of aroma volatiles, especially esters, while increasing storage time prior to ripening is accompanied by a decrease in the amount of aroma volatiles.  相似文献   
107.
The mechanism of colour change during the pigment dispersion process and during powder application to the skin surface was studied by examining the colour extension properties of Yellow. Red , and Black iron oxides in white powder bases. A new measure for the evaluation of the degree of colour extension was devised. This measure corresponded well with human visual sensation, and was found to be useful for comparing the rates of colour extension of pigments. The rate of colour extension of pigments was found to vary in the order: Yellow acicular Red granular Red Black. This result explains colour darkening and the change towards reddish tones during the pigment dispersion process, because Yellow extends fully in the early stage of the process but Red , especially in granular form, and Black continue to extend even in the later stage. Acicular Red iron oxide is more favourably employed than the granular form to attain sufficient colour extension of foundations with lower energy expenditure, and to decrease the discrepancy between the cake colour and the colour of applied powder.
Le développement des oxydes de fer et effet sur les nuances des fonds de teint compacts  相似文献   
108.
高炉煤气干法除尘技术发展现状及宝钢应用前景   总被引:1,自引:0,他引:1  
田敬龙 《冶金动力》2007,(6):20-21,30
在对高炉煤气干法除尘技术应用现状进行综合分析的基础上结合宝钢实际,提出宝钢应用此技术的相关建议。  相似文献   
109.
The UK's vast marine energy resource is mostly located in remote areas west and north of Scotland, and transmission of this energy to the mainland will be required. This may be achieved by using this ‘stranded’ power to generate hydrogen electrolytically, which may in turn be stored or transported using sponge iron technology. This paper reviews the technology and research needed to bring such a process on stream. We propose utilising techniques that have been developed for the oxygen carriers used in chemical looping, and also those used in early processes for hydrogen generation in the chemical industry. We briefly outline the design requirements for an energy efficient sponge iron plant. It is shown that the iron sponge system presents better energy efficiencies than alternative forms of bulk storage such as liquid hydrogen, magnesium hydride slurry, some at least of the metal hydrides, or methylcyclohexane–toluene–hydrogen, provided that requirements can be met for particle durability and reactivity.  相似文献   
110.
济钢第一炼钢厂降低钢铁料消耗实践   总被引:2,自引:0,他引:2  
济钢第一炼钢厂通过优化入炉原料结构,改进冶炼工艺,实施少渣炼钢,有效减少了转炉吹损,降低了钢铁料消耗成本,2002年增加炼钢综合经济效益3100多万元。  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