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   206219篇
  免费   2257篇
  国内免费   542篇
电工技术   3526篇
综合类   142篇
化学工业   31836篇
金属工艺   10272篇
机械仪表   7012篇
建筑科学   3999篇
矿业工程   2162篇
能源动力   4631篇
轻工业   12910篇
水利工程   2924篇
石油天然气   7730篇
武器工业   22篇
无线电   21521篇
一般工业技术   45183篇
冶金工业   34398篇
原子能技术   6626篇
自动化技术   14124篇
  2021年   2054篇
  2019年   1999篇
  2018年   3679篇
  2017年   3716篇
  2016年   4000篇
  2015年   2234篇
  2014年   3783篇
  2013年   8738篇
  2012年   5679篇
  2011年   7215篇
  2010年   5854篇
  2009年   6486篇
  2008年   6610篇
  2007年   6491篇
  2006年   5571篇
  2005年   5116篇
  2004年   4629篇
  2003年   4554篇
  2002年   4369篇
  2001年   4475篇
  2000年   4184篇
  1999年   4197篇
  1998年   10189篇
  1997年   7187篇
  1996年   5503篇
  1995年   4131篇
  1994年   3599篇
  1993年   3840篇
  1992年   2983篇
  1991年   2995篇
  1990年   2890篇
  1989年   2852篇
  1988年   2865篇
  1987年   2510篇
  1986年   2568篇
  1985年   2854篇
  1984年   2687篇
  1983年   2554篇
  1982年   2302篇
  1981年   2269篇
  1980年   2348篇
  1979年   2361篇
  1978年   2384篇
  1977年   2491篇
  1976年   2877篇
  1975年   2188篇
  1974年   2069篇
  1973年   2166篇
  1972年   1940篇
  1971年   1755篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A continuous oxygen uptake meter or continuous respirometer was developed which produced a rapid and reliable response to systemic shocks. The respirometer basically is a 101. Plexiglas laboratory activated sludge unit with a variable volume air tight side car. The feed enters the completely mixed aeration basin and is pumped into the side car. The side car is the site of the oxygen uptake measurements as indicated by a continuously monitoring dissolved oxygen probe. The system was most sensitive to changes in influent concentrations when run at an F/M = 0.1. Response time for a change in DO of 0.1 ppm was less than 4 min. The continuous respirometer was tested employing both synthetic and raw industrial wastes.  相似文献   
72.
Davyhulme sewage-treatment works, which serves the Manchester drainage area, is one of the lagest in the UK. The dry-weather flow is 300 000 m3/d, and the plant receives a wide range of industrial effluents. The works has been identified as a major source of pollution in the Mersey estuary, with an average discharge of 6500 kg ammonia/day. As part of its initiative to improve the Mersey estuary, North West Water intends to reduce the daily ammonia load from Davyhulme to about 1000 kg/d by 1995. In order to assess the capabilities of both conventional and novel processes to achieve this degree of ammonia removal, a number of on-site pilot plants were established. This paper reports on the pilot-plant studies and the selection of process options. Recommendations with regard to design parameters and final process selection are given.  相似文献   
73.
Fibre Chemistry - Modification of polycaproamide by 1H,1H,13H-trihydroperfluorotridecan-1-ol immobilized on montmorillonite produced an F-containing polymer composite. The structure of the...  相似文献   
74.
Theoretical Foundations of Chemical Engineering - The paper presents a study of the process of the isolation of styrene-butadiene rubber from latex with the method of mathematical planning for a...  相似文献   
75.
Glass and Ceramics - A system for technological regulation of adverse environmental impacts (AEI) that is based on the best available technologies (BAT) was analyzed. The expediency of updating the...  相似文献   
76.
Russian Engineering Research - Polymer samples based on polydicyclopentadiene produced from Russian dicyclopentadiene are investigated by thermogravimetric analysis and differential scanning...  相似文献   
77.
78.
The optical, and electrophysical characteristics of hydrogenated silicon oxycarbonitride films synthesized by the plasma enhanced chemical vapor decomposition of the mixtures of 1,1,1,3,3,3-hexamethyldisilazane with oxygen and nitrogen in the temperature range of 373–973 K have been studied. It has been shown that the obtained films are highly transparent (transmittance is ~92–99%) in the UV, visible, and IR ranges of the spectrum; they have refractive indices in the range of 1.43–2.25, a low reflection coefficient of visible light (nearly 3%), and low dielectric permittivity.  相似文献   
79.
An efficient protocol for the direct sulfanylation of various 4‐hydroxycoumarins and 4‐hydroxyquinolinones in good yield with arylsulfonylhydrazides as sulfanylating agents was developed via copper(I) bromide⋅dimethyl sulfide‐catalyzed S–O, S–N bond cleavage and C–S cross‐coupling reactions. A highly selective fluorescence turning‐on sensing of cadmium(II) ions in water using the synthesized 3‐sulfanyl‐4‐hydroxycoumarin derivative was also investigated.

  相似文献   

80.
Refractories and Industrial Ceramics - The article discusses the temperature regimes of transit pipelines for steam and hot water movement. A new device for thermal insulation of high-temperature...  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