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   608592篇
  免费   7185篇
  国内免费   1044篇
电工技术   11222篇
综合类   529篇
化学工业   94958篇
金属工艺   27844篇
机械仪表   21066篇
建筑科学   13397篇
矿业工程   4650篇
能源动力   14832篇
轻工业   46586篇
水利工程   7558篇
石油天然气   15424篇
武器工业   39篇
无线电   64257篇
一般工业技术   127445篇
冶金工业   98645篇
原子能技术   15005篇
自动化技术   53364篇
  2021年   5481篇
  2019年   5274篇
  2018年   13844篇
  2017年   14153篇
  2016年   12658篇
  2015年   6278篇
  2014年   10311篇
  2013年   26154篇
  2012年   17246篇
  2011年   25761篇
  2010年   21496篇
  2009年   22560篇
  2008年   23018篇
  2007年   24006篇
  2006年   16323篇
  2005年   16716篇
  2004年   15265篇
  2003年   14840篇
  2002年   13724篇
  2001年   12906篇
  2000年   12453篇
  1999年   12025篇
  1998年   27657篇
  1997年   20045篇
  1996年   15642篇
  1995年   12018篇
  1994年   10886篇
  1993年   10633篇
  1992年   8346篇
  1991年   8121篇
  1990年   7992篇
  1989年   7765篇
  1988年   7484篇
  1987年   6747篇
  1986年   6534篇
  1985年   7391篇
  1984年   6700篇
  1983年   6438篇
  1982年   5777篇
  1981年   5898篇
  1980年   5631篇
  1979年   5734篇
  1978年   5668篇
  1977年   6186篇
  1976年   7689篇
  1975年   5112篇
  1974年   4909篇
  1973年   4987篇
  1972年   4280篇
  1971年   4042篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Refractories and Industrial Ceramics - The effect of the addition of 2 and 5 mol.% Dy2O3 during spark-plasma sintering at a compaction loading of 60 MPa in the range of 1200 – 1600°C on...  相似文献   
192.
The results of a system analysis of the efficiency of nitrous oxide(N_2O) as a propellant component for small space vehicles(SSV) were presented. A criterion for mass efficiency of the SSV propulsion system(PS) is determined. The current global state-of-the-art of SSV PSs is shown. The application field of nitrous oxide in SSV PSs is calculated and mass efficiency of N_2O application is quantitatively determined. An overview of physical and chemical as well as operational properties of nitrous oxide as a promising, non-toxic component of rocket propellant is provided. Main physical and chemical constants of gaseous and liquid nitrous oxide; chemical properties of N_2O, thermal stability of N_2O, catalytic decomposition of N_2O, a mechanism of decomposition of N_2O, catalysts for decomposition of N_2O, ballast additives to N_2O, application of nitrous oxide, nitrous oxide as a rocket propellant, production of nitrous oxide, toxicity of nitrous oxide, fire hazard of N_2O, requirements to equipment when handling N_2O; storage and transportation of N_2O are considered. It is demonstrated that nitrous oxide is a chemical compound meeting the requirements to rocket propellants, including those related to the environmental friendliness of propellants. With 75 references.  相似文献   
193.
194.
Refractories and Industrial Ceramics - Results of studying the rheotechnological properties of moldable refractory mixes based on bauxite suspensions plasticized with refractory clay are presented....  相似文献   
195.
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   
196.
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   
197.
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   
198.
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   
199.
200.
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   
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