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   1406860篇
  免费   25603篇
  国内免费   6896篇
电工技术   33863篇
综合类   6321篇
化学工业   266334篇
金属工艺   62659篇
机械仪表   38917篇
建筑科学   43979篇
矿业工程   11215篇
能源动力   50134篇
轻工业   99624篇
水利工程   13969篇
石油天然气   37269篇
武器工业   130篇
无线电   193318篇
一般工业技术   266781篇
冶金工业   116519篇
原子能技术   33636篇
自动化技术   164691篇
  2021年   15562篇
  2020年   11824篇
  2019年   14581篇
  2018年   13881篇
  2017年   13049篇
  2016年   20327篇
  2015年   17150篇
  2014年   28559篇
  2013年   87431篇
  2012年   32595篇
  2011年   43182篇
  2010年   40132篇
  2009年   49181篇
  2008年   40914篇
  2007年   37563篇
  2006年   42259篇
  2005年   36496篇
  2004年   39190篇
  2003年   39304篇
  2002年   38735篇
  2001年   34953篇
  2000年   33847篇
  1999年   32107篇
  1998年   29869篇
  1997年   30147篇
  1996年   29426篇
  1995年   27239篇
  1994年   26030篇
  1993年   25946篇
  1992年   25272篇
  1991年   22169篇
  1990年   22628篇
  1989年   21705篇
  1988年   20151篇
  1987年   18564篇
  1986年   17853篇
  1985年   21218篇
  1984年   21821篇
  1983年   19798篇
  1982年   18932篇
  1981年   18987篇
  1980年   17550篇
  1979年   18178篇
  1978年   17432篇
  1977年   16534篇
  1976年   16377篇
  1975年   15760篇
  1974年   15305篇
  1973年   15364篇
  1972年   12846篇
排序方式: 共有10000条查询结果,搜索用时 0 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