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   686136篇
  免费   8331篇
  国内免费   1153篇
电工技术   12280篇
综合类   518篇
化学工业   107311篇
金属工艺   30526篇
机械仪表   22454篇
建筑科学   15127篇
矿业工程   5998篇
能源动力   16883篇
轻工业   51162篇
水利工程   9023篇
石油天然气   19988篇
武器工业   48篇
无线电   70193篇
一般工业技术   146729篇
冶金工业   112396篇
原子能技术   18895篇
自动化技术   56089篇
  2021年   6576篇
  2019年   6294篇
  2018年   11245篇
  2017年   11416篇
  2016年   11958篇
  2015年   7326篇
  2014年   12500篇
  2013年   31251篇
  2012年   19013篇
  2011年   25302篇
  2010年   20317篇
  2009年   22712篇
  2008年   23015篇
  2007年   22577篇
  2006年   19411篇
  2005年   17505篇
  2004年   16782篇
  2003年   16449篇
  2002年   15921篇
  2001年   15381篇
  2000年   14816篇
  1999年   14335篇
  1998年   32102篇
  1997年   23529篇
  1996年   18298篇
  1995年   14149篇
  1994年   12958篇
  1993年   12686篇
  1992年   9986篇
  1991年   9713篇
  1990年   9619篇
  1989年   9258篇
  1988年   8918篇
  1987年   8232篇
  1986年   7978篇
  1985年   8953篇
  1984年   8225篇
  1983年   7934篇
  1982年   7212篇
  1981年   7370篇
  1980年   7131篇
  1979年   7350篇
  1978年   7343篇
  1977年   8004篇
  1976年   9678篇
  1975年   6629篇
  1974年   6539篇
  1973年   6599篇
  1972年   5796篇
  1971年   5360篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Russian Engineering Research - The strategic efficiency of a project is defined. An approach to assessing the strategic efficiency of projects is outlined. This approach, incorporated in the State...  相似文献   
92.
93.
94.
95.
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   
96.
97.
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   
98.
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   
99.
ABSTRACT

Solvent extraction studies were performed to understand the extraction behavior of Np4+ and NpO2 2+ from acidic feeds with CMPO (octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide) dissolved in 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide, a water immiscible ionic liquid. Slope analyses on the distribution data revealed the extraction of ML2 type species, where M = Np4+ or NpO2 2+, and L = CMPO. Studies were also carried out with Pu4+ and UO2 2+ under identical conditions. The nature of the extracted species was found to vary with the nature of the ionic species.  相似文献   
100.
Abstract

An eco-friendly catalyst system was synthesized using three step reaction. The Cu nanoparticles bridged aminoclay catalyst was analyzed using various analytical techniques. The structure of the catalyst was confirmed by FTIR and XRD. The synthesized catalyst system was used for the reduction of p-nitrophenol (NP), Cr(VI), and fluorescein (Flur) dye individually, as well as in their mixture forms. The kapp value was computed to access the efficiency of the catalyst. The results indicated that the kapp value of the individual system is higher than that of the mixture systems due to the absence of the complex formation reaction. The catalytic performance of the catalyst was also tested for the Schiff base (SB) formation between poly(ethyleneglycol) (PEG) and aniline (ANI) in an oxygen atmosphere. The 1H-NMR spectroscopy result indicates that the present catalyst system produced 86% yield.  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