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   694608篇
  免费   9468篇
  国内免费   1644篇
电工技术   12354篇
综合类   618篇
化学工业   104148篇
金属工艺   30556篇
机械仪表   22307篇
建筑科学   15722篇
矿业工程   5370篇
能源动力   17204篇
轻工业   52780篇
水利工程   8624篇
石油天然气   18053篇
武器工业   50篇
无线电   73156篇
一般工业技术   145202篇
冶金工业   125708篇
原子能技术   17772篇
自动化技术   56096篇
  2021年   6689篇
  2020年   4948篇
  2019年   6397篇
  2018年   11369篇
  2017年   11350篇
  2016年   11916篇
  2015年   7664篇
  2014年   12786篇
  2013年   31147篇
  2012年   19589篇
  2011年   26224篇
  2010年   20794篇
  2009年   23286篇
  2008年   23753篇
  2007年   23185篇
  2006年   19741篇
  2005年   17983篇
  2004年   17489篇
  2003年   17317篇
  2002年   16387篇
  2001年   16435篇
  2000年   15256篇
  1999年   15487篇
  1998年   37718篇
  1997年   26945篇
  1996年   20542篇
  1995年   15654篇
  1994年   13745篇
  1993年   13617篇
  1992年   10176篇
  1991年   9772篇
  1990年   9668篇
  1989年   9232篇
  1988年   8648篇
  1987年   7939篇
  1986年   7763篇
  1985年   8534篇
  1984年   8080篇
  1983年   7331篇
  1982年   6858篇
  1981年   7045篇
  1980年   6806篇
  1979年   6841篇
  1978年   6819篇
  1977年   7719篇
  1976年   9699篇
  1975年   6014篇
  1974年   5858篇
  1973年   5941篇
  1972年   5094篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
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   
82.
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   
83.
84.
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   
85.
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   
86.
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   
87.
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   
88.
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   
89.
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to...  相似文献   
90.
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