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   566323篇
  免费   6703篇
  国内免费   1003篇
电工技术   10509篇
综合类   466篇
化学工业   90054篇
金属工艺   23338篇
机械仪表   18499篇
建筑科学   12532篇
矿业工程   4312篇
能源动力   14430篇
轻工业   45762篇
水利工程   6941篇
石油天然气   14961篇
武器工业   39篇
无线电   60284篇
一般工业技术   116226篇
冶金工业   95566篇
原子能技术   14681篇
自动化技术   45429篇
  2021年   5480篇
  2019年   5269篇
  2018年   9202篇
  2017年   9409篇
  2016年   9832篇
  2015年   6027篇
  2014年   10243篇
  2013年   26106篇
  2012年   15775篇
  2011年   21096篇
  2010年   16971篇
  2009年   18819篇
  2008年   19071篇
  2007年   18771篇
  2006年   16286篇
  2005年   14742篇
  2004年   14012篇
  2003年   13691篇
  2002年   13247篇
  2001年   12851篇
  2000年   12330篇
  1999年   12012篇
  1998年   27650篇
  1997年   20042篇
  1996年   15628篇
  1995年   12005篇
  1994年   10860篇
  1993年   10613篇
  1992年   8332篇
  1991年   8102篇
  1990年   7990篇
  1989年   7763篇
  1988年   7478篇
  1987年   6747篇
  1986年   6533篇
  1985年   7390篇
  1984年   6700篇
  1983年   6437篇
  1982年   5776篇
  1981年   5896篇
  1980年   5630篇
  1979年   5733篇
  1978年   5663篇
  1977年   6178篇
  1976年   7685篇
  1975年   5108篇
  1974年   4903篇
  1973年   4980篇
  1972年   4279篇
  1971年   4038篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature.  相似文献   
172.
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes.  相似文献   
173.
Power Technology and Engineering - The major results from the survey and geotechnical monitoring during the leveling of the model foundation of the Zagorsk PSP-2 in test site No. 3 are presented....  相似文献   
174.
Russian Engineering Research - The machining precision in grinding a flexible shaft by sharp and blunt wheels is compared for a CNC system with a specified cycle of radial supply velocities. To...  相似文献   
175.
176.
International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...  相似文献   
177.
Measurement Techniques - A comparative analysis of the results of estimation of measurement uncertainty is conducted. The results are obtained by a method described in the Handbook on the...  相似文献   
178.
The purpose of this research was to determine the effect of high-intensity ultrasound (HIU) on physical properties, degree of oxidation, and oxidative stability of structured lipids (SLs). Caprylic acid (C) and stearic acid (S) were incorporated into menhaden oil using Lipozyme® 435 lipase to obtain five samples: (1) LC 20 (menhaden oil with 20% of C), (2) LC 30 (menhaden oil with 30% C), (3) LS 20 (menhaden oil with 20% S), (4) LS 30 (menhaden oil with 30% S), and (5) Blend C (menhaden oil with 16.24% C and 13.04% S). Samples were crystallized for 90 min at the following temperatures: (1) LC 20 at 15.5°C, (2) LC 30 at 17.5°C, (3) LS 20 at 24°C, (4) LS 30 at 30°C, and (5) Blend C at 18.0°C, and HIU was applied at the onset of crystallization. Physical properties, degree of oxidation, and oxidative stability were evaluated in sonicated and nonsonicated samples. All SLs had statistically higher G′ after sonication. Sonicated LS 30, LC 30, and Blend C had a higher melting enthalpy than the nonsonicated ones, while enthalpy values in sonicated LS 20 and LC 20 samples were not statistically different than the nonsonicated ones. No significant difference between sonicated and nonsonicated samples was observed in peroxide values (1.2 ± 0.1 meq/kg, p > 0.05) and in the oxidative stability index (6.3 ± 0.2 h, p > 0.05). These results showed that HIU was effective at changing physical properties without affecting the oxidation of the samples.  相似文献   
179.
Protection of Metals and Physical Chemistry of Surfaces - The conditions for carrying out molecular dynamics calculations of adsorption isotherms of gases and vapors in micropores of active carbons...  相似文献   
180.
Journal of Inorganic and Organometallic Polymers and Materials - This work aimed to investigate the impact of Lead-fluoride based glasses via theoretical and simulation techniques on mechanical and...  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