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   1524935篇
  免费   26147篇
  国内免费   6986篇
电工技术   34253篇
综合类   6485篇
化学工业   271597篇
金属工艺   64115篇
机械仪表   42741篇
建筑科学   47063篇
矿业工程   11374篇
能源动力   50219篇
轻工业   117910篇
水利工程   15495篇
石油天然气   37289篇
武器工业   136篇
无线电   196394篇
一般工业技术   287950篇
冶金工业   170386篇
原子能技术   33792篇
自动化技术   170869篇
  2021年   15584篇
  2020年   11849篇
  2019年   14627篇
  2018年   14845篇
  2017年   14039篇
  2016年   21057篇
  2015年   17364篇
  2014年   28772篇
  2013年   87877篇
  2012年   36171篇
  2011年   48456篇
  2010年   42202篇
  2009年   50359篇
  2008年   45359篇
  2007年   42593篇
  2006年   45610篇
  2005年   39879篇
  2004年   42437篇
  2003年   42285篇
  2002年   41337篇
  2001年   38374篇
  2000年   36638篇
  1999年   35617篇
  1998年   46948篇
  1997年   40588篇
  1996年   36347篇
  1995年   31505篇
  1994年   29560篇
  1993年   29107篇
  1992年   26536篇
  1991年   23627篇
  1990年   23873篇
  1989年   22949篇
  1988年   21448篇
  1987年   19724篇
  1986年   19187篇
  1985年   22572篇
  1984年   22691篇
  1983年   20571篇
  1982年   19425篇
  1981年   19492篇
  1980年   18096篇
  1979年   18743篇
  1978年   17922篇
  1977年   17988篇
  1976年   19538篇
  1975年   16110篇
  1974年   15646篇
  1973年   15719篇
  1972年   13209篇
排序方式: 共有10000条查询结果,搜索用时 9 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