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   1526731篇
  免费   26415篇
  国内免费   7188篇
电工技术   34621篇
综合类   6434篇
化学工业   272215篇
金属工艺   65020篇
机械仪表   43501篇
建筑科学   46755篇
矿业工程   11573篇
能源动力   50321篇
轻工业   115680篇
水利工程   15613篇
石油天然气   37891篇
武器工业   145篇
无线电   197708篇
一般工业技术   287860篇
冶金工业   170807篇
原子能技术   34078篇
自动化技术   170112篇
  2021年   15681篇
  2020年   11958篇
  2019年   14753篇
  2018年   16582篇
  2017年   16035篇
  2016年   21777篇
  2015年   17435篇
  2014年   28746篇
  2013年   87895篇
  2012年   36185篇
  2011年   49311篇
  2010年   43383篇
  2009年   51633篇
  2008年   45711篇
  2007年   43241篇
  2006年   45153篇
  2005年   40391篇
  2004年   42066篇
  2003年   41883篇
  2002年   40726篇
  2001年   37809篇
  2000年   36062篇
  1999年   35363篇
  1998年   48472篇
  1997年   40993篇
  1996年   36283篇
  1995年   31266篇
  1994年   29190篇
  1993年   29099篇
  1992年   26198篇
  1991年   23345篇
  1990年   23638篇
  1989年   22672篇
  1988年   21249篇
  1987年   19470篇
  1986年   18875篇
  1985年   22217篇
  1984年   22398篇
  1983年   20376篇
  1982年   19293篇
  1981年   19412篇
  1980年   18011篇
  1979年   18579篇
  1978年   17766篇
  1977年   17523篇
  1976年   18288篇
  1975年   16058篇
  1974年   15554篇
  1973年   15654篇
  1972年   13103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