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   429731篇
  免费   4822篇
  国内免费   960篇
电工技术   7100篇
综合类   843篇
化学工业   65222篇
金属工艺   21575篇
机械仪表   15056篇
建筑科学   8148篇
矿业工程   5140篇
能源动力   8254篇
轻工业   22636篇
水利工程   6461篇
石油天然气   16169篇
武器工业   45篇
无线电   38463篇
一般工业技术   94914篇
冶金工业   77879篇
原子能技术   14132篇
自动化技术   33476篇
  2021年   4133篇
  2019年   3975篇
  2018年   7863篇
  2017年   8326篇
  2016年   9138篇
  2015年   5234篇
  2014年   8035篇
  2013年   16870篇
  2012年   12972篇
  2011年   16182篇
  2010年   11918篇
  2009年   13300篇
  2008年   13389篇
  2007年   12981篇
  2006年   10866篇
  2005年   12494篇
  2004年   11335篇
  2003年   10582篇
  2002年   9149篇
  2001年   8963篇
  2000年   8265篇
  1999年   8063篇
  1998年   21586篇
  1997年   15247篇
  1996年   11313篇
  1995年   8359篇
  1994年   7332篇
  1993年   7639篇
  1992年   5576篇
  1991年   5704篇
  1990年   5632篇
  1989年   5425篇
  1988年   5348篇
  1987年   4981篇
  1986年   4908篇
  1985年   5319篇
  1984年   5011篇
  1983年   4829篇
  1982年   4544篇
  1981年   4613篇
  1980年   4697篇
  1979年   4755篇
  1978年   4905篇
  1977年   5571篇
  1976年   6981篇
  1975年   4528篇
  1974年   4490篇
  1973年   4586篇
  1972年   4082篇
  1971年   3742篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Theoretical Foundations of Chemical Engineering - Using gas–liquid chromatography, the activity coefficients upon the infinite dilution of the components of the reaction mixture for obtaining...  相似文献   
12.
Theoretical Foundations of Chemical Engineering - The main approaches to developing a reactor block for the hydrodesulfurization of diesel fuels are considered taking into account the reactivity of...  相似文献   
13.
Journal of Signal Processing Systems - Convolutional Neural Networks (CNNs) have improved several computer vision applications, like object detection and classification, when compared to other...  相似文献   
14.
The phospholipid composition of lipoproteins is determined by the specificity of hepatic phospholipid biosynthesis. Plasma phospholipid 20:4n-6 and 22:6n-3 concentrations are higher in women than in men. We used this sex difference in a lipidomics analysis of the impact of endocrine factors on the phospholipid class and molecular species composition of fasting plasma from young men and women. Diester species predominated in all lipid classes measured. 20/54 Phosphatidylcholine (PtdCho) species were alkyl ester, 15/48 phosphatidylethanolamine (PtdEtn) species were alkyl ester, and 12/48 PtdEtn species were alkenyl ester. There were no significant differences between sexes in the proportions of alkyl PtdCho species. The proportion of alkyl ester PtdEtn species was greater in women than men, while the proportion of alkenyl ester PtdEtn species was greater in men than women. None of the phosphatidylinositol (PtdIns) or phosphatidylserine (PtdSer) molecular species contained ether-linked fatty acids. The proportion of PtdCho16:0_22:6, and the proportions of PtdEtn O-16:0_20:4 and PtdEtn O-18:2_20:4 were greater in women than men. There were no sex differences in PtdIns and PtdSer molecular species compositions. These findings show that plasma phospholipids can be modified by sex. Such differences in lipoprotein phospholipid composition could contribute to sexual dimorphism in patterns of health and disease.  相似文献   
15.
Journal of Communications Technology and Electronics - Abstract—The matrix coefficients of projection models of strip lines obtained using the Chebyshev basis are presented as a sum of...  相似文献   
16.
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The...  相似文献   
17.
18.
Refractories and Industrial Ceramics - Technology for producing alumina-periclase-carbon refractories of the brands APUK-D and APU-D is developed and implemented. Use of complex antioxidant and...  相似文献   
19.
Laser ablation of high-temperature ceramic coatings results in thermal residual stresses due to which the coatings fail by cracking and debonding. Hence, the measurement of such residual stresses during laser ablation process holds utmost importance from the view of performance of coatings in extreme conditions. The present research aims at investigating the effect of laser parameters such as laser pulse energy, scanning speed and line spacing on thermal residual stresses induced in tantalum carbide-coated graphite substrates. Residual stresses were measured using micro-Raman spectroscopy and correlated with Raman peak shifts. Transient thermal analysis was performed using COMSOL Multiphysics to model the single ablated track and residual stresses were reported at low, moderate and high pulse energy regimes. The results showed that the initial laser conditions caused higher tensile residual stresses. Moderate pulse energy regime comprised higher compressive residual stresses due to off centre overlapping of the laser pulses. Higher pulse energy (250 μJ), higher scanning speed (1000 mm/s) and moderate line spacing (20 μm) caused accumulation of tensile residual stresses during the final stage of laser ablation. The deviation of experimental residual stresses from COMSOL numerical model was attributed to unaccounted additional stresses induced during thermal spraying process and deformation potentials in the numerical model.  相似文献   
20.
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,...  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