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   1510152篇
  免费   27317篇
  国内免费   6936篇
电工技术   35019篇
综合类   6383篇
化学工业   273136篇
金属工艺   66023篇
机械仪表   44548篇
建筑科学   45939篇
矿业工程   11758篇
能源动力   50323篇
轻工业   110888篇
水利工程   15316篇
石油天然气   38282篇
武器工业   141篇
无线电   198374篇
一般工业技术   287800篇
冶金工业   155513篇
原子能技术   34402篇
自动化技术   170560篇
  2021年   15562篇
  2020年   11831篇
  2019年   14605篇
  2018年   18146篇
  2017年   17863篇
  2016年   22385篇
  2015年   17530篇
  2014年   28699篇
  2013年   88110篇
  2012年   35879篇
  2011年   50048篇
  2010年   44804篇
  2009年   53225篇
  2008年   46094篇
  2007年   43905篇
  2006年   44254篇
  2005年   40243篇
  2004年   41730篇
  2003年   41360篇
  2002年   40215篇
  2001年   36739篇
  2000年   35369篇
  1999年   34300篇
  1998年   41661篇
  1997年   37386篇
  1996年   34089篇
  1995年   29872篇
  1994年   28253篇
  1993年   28074篇
  1992年   26084篇
  1991年   23078篇
  1990年   23459篇
  1989年   22568篇
  1988年   21066篇
  1987年   19402篇
  1986年   18735篇
  1985年   22037篇
  1984年   22251篇
  1983年   20201篇
  1982年   19188篇
  1981年   19313篇
  1980年   17919篇
  1979年   18475篇
  1978年   17703篇
  1977年   17413篇
  1976年   18256篇
  1975年   16023篇
  1974年   15518篇
  1973年   15587篇
  1972年   13056篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
192.
To overcome the drawbacks of solid microporous materials for CO2 capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO2 through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO2 uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder.  相似文献   
193.
Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this...  相似文献   
194.
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   
195.
196.
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally.  相似文献   
197.
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   
198.
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   
199.
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   
200.
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