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   1478616篇
  免费   25791篇
  国内免费   6968篇
电工技术   34081篇
综合类   6390篇
化学工业   268562篇
金属工艺   63818篇
机械仪表   41122篇
建筑科学   45405篇
矿业工程   11285篇
能源动力   50149篇
轻工业   108162篇
水利工程   15015篇
石油天然气   37267篇
武器工业   131篇
无线电   195056篇
一般工业技术   277307篇
冶金工业   156469篇
原子能技术   33780篇
自动化技术   167376篇
  2021年   15493篇
  2020年   11790篇
  2019年   14540篇
  2018年   14451篇
  2017年   13585篇
  2016年   20637篇
  2015年   17213篇
  2014年   28583篇
  2013年   87640篇
  2012年   34201篇
  2011年   45647篇
  2010年   41221篇
  2009年   49799篇
  2008年   43118篇
  2007年   39983篇
  2006年   43801篇
  2005年   38197篇
  2004年   40709篇
  2003年   40672篇
  2002年   39948篇
  2001年   36741篇
  2000年   35201篇
  1999年   34283篇
  1998年   42509篇
  1997年   37677篇
  1996年   34441篇
  1995年   30197篇
  1994年   28425篇
  1993年   28281篇
  1992年   25969篇
  1991年   23140篇
  1990年   23395篇
  1989年   22506篇
  1988年   21017篇
  1987年   19313篇
  1986年   18646篇
  1985年   22004篇
  1984年   22221篇
  1983年   20198篇
  1982年   19234篇
  1981年   19318篇
  1980年   17925篇
  1979年   18472篇
  1978年   17746篇
  1977年   17535篇
  1976年   18761篇
  1975年   16007篇
  1974年   15516篇
  1973年   15574篇
  1972年   13051篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Poor aqueous solubility is one of the recurrent drawbacks of many compounds in medicinal chemistry. To overcome this limitation, the dilution of drug candidates from stock solutions of an organic solvent is common practice. However, the precise characterisation of these compounds in aqueous solutions is often neglected, leading to some uncertainties regarding the nature of the actual active species. In this communication, we demonstrate that two ruthenium complexes previously reported by our group for their chemotherapeutic potential against cancer, namely [Ru(DIP)2(sq)](PF6) and [Ru(DIP)2(3-methoxysq)](PF6), where DIP is 4,7-diphenyl-1,10-phenanthroline, sq=semiquinonate and 3-methoxysq=3-methoxysemiquinonate, form colloids in water-DMSO (1 % v/v) mixtures that are invisible to the naked eyes. [Ru(DIP)2(3-methoxysq)](PF6) was found to form a highly stable and monodispersed colloid with nanoaggregates of ∼25 nm. In contrast, [Ru(DIP)2(sq)](PF6) was found to form large reticulates of mostly spherical aggregates which size was found to increase over time. The difference in size and shape distribution of drug candidates is of tremendous significance as the study of their biological activity might be severely affected. Overall, we strongly believe that these observations should be taken into account by the scientific community working on the development of metal-based drugs with poor water solubility.  相似文献   
12.
13.
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance.  相似文献   
14.
15.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution.  相似文献   
16.
17.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
18.
A method is proposed to generate categorical colour observer functions (individual colour matching functions) for any field size based on the CIE 2006 system of physiological observer functions. The method combines proposed categorical observer techniques of Sarkar et al with a physiologically-based individual observer model of Asano et al and a clustering technique to produce the optimal set of categorical observers. The number of required categorical observers varies depending on an application with as many as 50 required to predict individual observers' matches when a laser projector is viewed. However, 10 categorical observers are sufficient to represent colour-normal populations for personalized colour imaging. The proposed and recommended categorical observers represent a robust and inclusive technique to examine and quantify observer metamerism in any application of colorimetry.  相似文献   
19.
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils.  相似文献   
20.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  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