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   911219篇
  免费   11342篇
  国内免费   2057篇
电工技术   16640篇
综合类   824篇
化学工业   139573篇
金属工艺   35299篇
机械仪表   27538篇
建筑科学   21719篇
矿业工程   5559篇
能源动力   23816篇
轻工业   76251篇
水利工程   10192篇
石油天然气   19150篇
武器工业   64篇
无线电   99804篇
一般工业技术   179301篇
冶金工业   171385篇
原子能技术   20045篇
自动化技术   77458篇
  2021年   8723篇
  2020年   6594篇
  2019年   7883篇
  2018年   13443篇
  2017年   13484篇
  2016年   14208篇
  2015年   9391篇
  2014年   15614篇
  2013年   41514篇
  2012年   24402篇
  2011年   33434篇
  2010年   26664篇
  2009年   29757篇
  2008年   30386篇
  2007年   29990篇
  2006年   26051篇
  2005年   23767篇
  2004年   22736篇
  2003年   22392篇
  2002年   21456篇
  2001年   21142篇
  2000年   19972篇
  1999年   20562篇
  1998年   51143篇
  1997年   36441篇
  1996年   28145篇
  1995年   21285篇
  1994年   18857篇
  1993年   18477篇
  1992年   13708篇
  1991年   12986篇
  1990年   12867篇
  1989年   12454篇
  1988年   11827篇
  1987年   10629篇
  1986年   10380篇
  1985年   11684篇
  1984年   10678篇
  1983年   9913篇
  1982年   9137篇
  1981年   9274篇
  1980年   8845篇
  1979年   8781篇
  1978年   8588篇
  1977年   9910篇
  1976年   12845篇
  1975年   7582篇
  1974年   7214篇
  1973年   7369篇
  1972年   6170篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Abstract

In the present work, we compare the structure and transport properties of carbon nanohorns (CNHs) synthesized by arc evaporation of graphite alone and with the addition of some portion of toluene. The materials have been investigated using transmission electron microscopy, Raman and infrared spectroscopies, thermogravimetric and BET analyses. The addition of a small amount of toluene during the evaporation of graphitic rod increases the length of CNHs, affects their hierarchical arrangement in aggregates and results in surface functionalization. All these features significantly enhance the conductivity of CNHs obtained with toluene additive in comparison with the pristine CNHs.  相似文献   
12.
The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T2), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T2 relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products.  相似文献   
13.
14.
The security of future supply with natural resources has to comply with objectives towards a sustainable and responsible development. Resources from the geosphere and recycling material from the technosphere may be grouped in a hierarchy the top of which is made up by fossil energy raw materials and of resources from occurrences which were formed by enrichment processes. The base of the hierarchy is made up by bulk raw materials which occur in unlimited amounts in the crust of the Earth and in the sea water and by waste and residues as potential raw materials. Optimising the efficiency of raw materials takes place if material from a lower level substitutes material from a higher level. Highest efficiency is reached if fossil energy from the top of the hierarchy is substituted or consumption is reduced.  相似文献   
15.
Search for conditions of conservation of fast ionic transport (FIT) in nanosystems of advanced superionic conductors (ASIC)[1-4] and synthesis of new types of device thin-film heterostructures on this basis is a fundamental scientific problem. ASICs (α-AgI, solid electrolytes of the family RbAg4I5, etc. ) are crystals with a record high level of ionic conductivity and a low value of activation energy E~0. 1 eV.  相似文献   
16.
根据实验室的试验结果,推荐应用浮选萃取联合工艺从水溶液中回收Mo(Ⅵ)。这一工艺包括制取以钼酸铵形式的商品,和对所有的有机试剂作再生处理。萃取Mo(Ⅵ)的准备系统,应包括在反萃取胺和用NaOH使水溶液碱化到pH=12以后,通过添加水溶液以使煤油、壬醇和AHII捕收剂按规定的比例进行混合等作业。对在萃取器中获得的混合液进行相分离后,有机溶液可用作泡沫浮选萃取Mo(Ⅵ)的萃取剂,而水溶液则加入到原始溶液中。  相似文献   
17.
Training and continuous education is today for the management of a mineral producing operation more important than ever before. The focus of education today in the field of mineral producing industry has not only to be dedicated versus the needs of the industry but also versus the importance of the ever increasing need of societal acceptance of industrial operations. Therefore it is expected that graduates from mining schools not only have a good knowledge of technical and economical subjects but also a good background for the realisation of environmental and safety targets for the people at work and in the neighbourhood of an operation. A strong request to the education and training at university level is therefore not only to deliver a broad knowledge but also the formation of a basis which allows to obtain authority for functions as “safety expert”, “Mine rescuer”, “waste disposal expert” and others. In the text the contents of the BSc study program “Natural resources” are reviewed and the training and education for a “Natural Resources Manager” together with the required continuous education is discussed.  相似文献   
18.
19.
20.
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