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   4866篇
  免费   677篇
  国内免费   154篇
电工技术   941篇
综合类   315篇
化学工业   892篇
金属工艺   184篇
机械仪表   209篇
建筑科学   172篇
矿业工程   257篇
能源动力   358篇
轻工业   257篇
水利工程   119篇
石油天然气   80篇
武器工业   21篇
无线电   650篇
一般工业技术   702篇
冶金工业   107篇
原子能技术   63篇
自动化技术   370篇
  2024年   29篇
  2023年   167篇
  2022年   123篇
  2021年   210篇
  2020年   250篇
  2019年   150篇
  2018年   135篇
  2017年   162篇
  2016年   176篇
  2015年   213篇
  2014年   350篇
  2013年   306篇
  2012年   379篇
  2011年   415篇
  2010年   269篇
  2009年   290篇
  2008年   269篇
  2007年   304篇
  2006年   255篇
  2005年   214篇
  2004年   172篇
  2003年   155篇
  2002年   129篇
  2001年   91篇
  2000年   98篇
  1999年   74篇
  1998年   72篇
  1997年   50篇
  1996年   45篇
  1995年   18篇
  1994年   27篇
  1993年   24篇
  1992年   10篇
  1991年   10篇
  1990年   9篇
  1989年   14篇
  1988年   9篇
  1987年   1篇
  1986年   4篇
  1985年   3篇
  1984年   7篇
  1983年   1篇
  1980年   4篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1965年   1篇
排序方式: 共有5697条查询结果,搜索用时 15 毫秒
1.
本文分析了相控阵机载预警(AEW)雷达杂波抑制的现有两种辅助通道降维技术(Klemm方法和简化方法)的性能,并提出了一种新的辅助通道方法。新方法的基本思想为:根据待处理距离段内各距离单元杂波能量在波束一多普勒域分布的统计特征自适应地选取辅助通道,使所选辅助通道实时地逼近杂波子空间,从而有效抑制杂波。本文方法不但可以用于非正侧视阵情况,而且误差鲁棒性好。计算机仿真结果证实了其有效性。  相似文献   
2.
We present the construction and some first applications of an On-line electrochemical mass spectrometry system for detecting volatile products formed during electrochemical reactions at a single-crystal electrode in hanging meniscus configuration. The system is based on a small inlet tip made of porous Teflon and a Peek holder, which is brought in close proximity (ca. 10–20 μm) to the electrode surface. The tip is connected to the mass spectrometer by glass and metal tubing. Because of the small amount of gas entering the mass spectrometer, no differential pumping is needed during the measurement. The tip construction and preparation introduced here leads to reproducible voltammetry with very good cleanliness characteristics. The presence of the tip has no significant influence on the blank voltammetry of a Pt(111) in sulfuric acid, and on voltammetric responses for CO adlayer oxidation, methanol oxidation, and hydroxylamine electrochemistry on Pt(111). The formation of gaseous products in these reactions can be followed accurately and is in good agreement with earlier results obtained by other mass spectrometric or spectroscopic techniques. The time response and tailing of the setup is on the order of seconds and mainly determined by the distance between the tip and the electrode.  相似文献   
3.
The paper deals with carbon fibre cloth electrodes, employed in the fabrication of composite materials. The electrical conductivity of single bundles, groups of bundles and cloth is studied. Ohm's law applies to the electrical conduction in the direction of the fibre length, but bundle conductivity decreases with the number of fibres in the bundle. Electrochemical mass transfer between a flowing electrolyte and a cloth arranged as a flow-through or a flow-by porous electrode indicates the existence of double porosity in the material. Due to double porosity, only the external surface of the cloth works as an electrode. This finding shows that the material is not suitable for such an application.  相似文献   
4.
Two kinds of biosensors for amino acids (one with nonspecific enzyme as bioelement, the other with specific enzyme(s) as bioelement), including their principles, applications, recent researches and future trends were discussed in detail. 61 references were given. A part of work for gaining Ph. D in chemical and biochemical application at FPMs (Mons, Belgique) Synopsis of the first author Xia Jinlan, Male, born in 1963, now at Facult’e Polytechnique de Mons, Belgique  相似文献   
5.
The current distribution and overall polarization behavior of electrodeposition at a flow-through (packed bed or fluidized bed) electrode are modeled by means of a one-dimensional model involving a primary reacting species and a simultaneous side reaction. The model equations are solved by orthogonal collocation; the time and storage requirements compare favorably to those of finite-difference methods. Experimental data obtained using a packed-bed electrode are compared with the model predictions and various methods of fitting the data are compared.  相似文献   
6.
介绍了某大型水电站施工辅助企业的建设和管理实例,探讨对该类项目的建设与管理经验。  相似文献   
7.
文章从原理上讨论了影响分米波电视发射管寿命的若干因素。并提出了若干延长寿命的建议:(1)正确的灯丝加热方法是行之有效的措施,经验证明:过分强调降低灯丝电压往往得到相反的效果。(2)必须有良好的冷却方式。(3)通过对帘栅电路的分析,说明对此电路必须作很好的处理以消除故障和防止寄生振荡。  相似文献   
8.
介绍了微机控制系统的原理、基本结构、重要参数的控制方法及使用效果。  相似文献   
9.
传统块状炭材料的发展概况   总被引:2,自引:0,他引:2  
刘明军 《炭素技术》2005,24(4):38-42
传统块状炭材料,如石墨电极、炼铝用阳极和阴极炭块、电炭制品、特种炭和石墨、炭砖等,在国民经济中占据不可替代的举足轻重的地位。本文简要概述了传统块状炭材料的国内外发展现状,在此基础上论述了我国相关领域中存在的问题,以期引起对传统但却十分重要的块状炭材料的进一步重视。  相似文献   
10.
Boron-doped diamond (BDD) electrodes were studied with respect to the formation of inorganic by-products in water electrolysis. Experiments in non-divided cells were performed with systems containing sulphate, chloride, chlorite, chlorate and nitrate ions. Discontinuous experiments in thermostated cells with rotating disk diamond anodes and expanded mesh IrO2 cathodes were carried out at 20 °C. Current density was varied between 50 and 300 A m−2. Ion chromatography was mainly used for species detection.

It was not possible to demonstrate the decomposition of sulphate although a slight tendency seems to exist in some experiments. Hydrogen peroxide is one of the anodic and cathodic by-products. Active chlorine is detectable at higher chloride concentrations compared with the use of mixed oxide anodes (MIO). One reason for this is the reaction of formed chlorine with ozone or hydrogen peroxide. Chlorate can be formed electrolysing chloride, hypochlorite and chlorite solutions. Perchlorate formation was detected. Cathodic processes are responsible for the formation of nitrite ions and ammonia. If chlorine is present, the formation of monochloramine is one possible side reaction. Results show that the processes are very complex. Reaction spectra may vary from case to case. Perchlorate formation is a high risk in drinking water treatment.  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