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   477517篇
  免费   7716篇
  国内免费   2430篇
电工技术   9735篇
技术理论   5篇
综合类   1489篇
化学工业   73181篇
金属工艺   19381篇
机械仪表   14765篇
建筑科学   11906篇
矿业工程   2618篇
能源动力   11175篇
轻工业   43419篇
水利工程   5048篇
石油天然气   9096篇
武器工业   311篇
无线电   56460篇
一般工业技术   90537篇
冶金工业   87514篇
原子能技术   9834篇
自动化技术   41189篇
  2021年   4142篇
  2019年   3771篇
  2018年   6225篇
  2017年   6258篇
  2016年   6718篇
  2015年   4754篇
  2014年   7871篇
  2013年   20975篇
  2012年   13020篇
  2011年   17440篇
  2010年   13931篇
  2009年   15212篇
  2008年   16589篇
  2007年   16702篇
  2006年   14933篇
  2005年   13256篇
  2004年   12313篇
  2003年   11804篇
  2002年   11472篇
  2001年   11591篇
  2000年   10983篇
  1999年   11065篇
  1998年   25045篇
  1997年   18280篇
  1996年   14274篇
  1995年   10963篇
  1994年   9882篇
  1993年   9709篇
  1992年   7726篇
  1991年   7197篇
  1990年   7150篇
  1989年   6841篇
  1988年   6518篇
  1987年   5702篇
  1986年   5599篇
  1985年   6494篇
  1984年   6140篇
  1983年   5636篇
  1982年   5130篇
  1981年   5422篇
  1980年   5041篇
  1979年   5066篇
  1978年   4841篇
  1977年   5382篇
  1976年   6799篇
  1975年   4388篇
  1974年   4239篇
  1973年   4289篇
  1972年   3541篇
  1971年   3270篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
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   
53.
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   
54.
Potato processing industry has a high degree of discarding, which currently has low added value being used primarily for animal feed. However, potato wastes offer a broad range of interesting components such as antioxidants, starch, protein or fibre with potential applications in the food and non-food industries. The recovery of these high valuable fractions using efficient multistage and multiproduct processes could be of great interest. This short review provides a general overview on the integral valorisation of potato wastes, offering an updated vision of the main residual parts generated during potato harvesting and processing, the high valuable obtained components focusing on the bioactive ones and the potential of the emerging extraction techniques over conventional ones. In addition, innovative applications are discussed to highlight the scientific and applied interest of these underutilised and undervalued fractions and to emphasise the integral valorisation of raw materials.  相似文献   
55.
56.
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   
57.
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   
58.
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   
59.
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   
60.
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st  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