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   358582篇
  免费   3802篇
  国内免费   880篇
电工技术   6777篇
综合类   328篇
化学工业   51764篇
金属工艺   16445篇
机械仪表   11590篇
建筑科学   7061篇
矿业工程   2686篇
能源动力   7159篇
轻工业   22486篇
水利工程   4494篇
石油天然气   11032篇
武器工业   30篇
无线电   40885篇
一般工业技术   74655篇
冶金工业   70425篇
原子能技术   10057篇
自动化技术   25390篇
  2021年   2976篇
  2019年   3019篇
  2018年   5445篇
  2017年   5538篇
  2016年   5954篇
  2015年   3543篇
  2014年   5978篇
  2013年   14557篇
  2012年   9108篇
  2011年   11550篇
  2010年   9561篇
  2009年   10903篇
  2008年   11230篇
  2007年   11124篇
  2006年   9820篇
  2005年   8983篇
  2004年   8606篇
  2003年   8255篇
  2002年   8017篇
  2001年   8414篇
  2000年   8061篇
  1999年   8409篇
  1998年   21593篇
  1997年   14898篇
  1996年   11221篇
  1995年   8321篇
  1994年   7249篇
  1993年   7362篇
  1992年   5366篇
  1991年   5264篇
  1990年   5321篇
  1989年   5080篇
  1988年   4826篇
  1987年   4181篇
  1986年   4293篇
  1985年   4626篇
  1984年   4259篇
  1983年   3966篇
  1982年   3685篇
  1981年   3986篇
  1980年   3656篇
  1979年   3746篇
  1978年   3859篇
  1977年   4202篇
  1976年   5530篇
  1975年   3479篇
  1974年   3468篇
  1973年   3466篇
  1972年   3084篇
  1971年   2703篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Golubev  N. V.  Ignat’eva  E. S.  Maurus  A. A.  Ziyatdinova  M. Z.  Lopatina  E. V.  Lorenzi  R.  Paleari  A.  Sigaev  V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence...  相似文献   
32.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
33.
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing...  相似文献   
34.
35.
36.
37.
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   
38.
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   
39.
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   
40.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  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