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   402943篇
  免费   34481篇
  国内免费   19023篇
电工技术   25070篇
技术理论   47篇
综合类   30002篇
化学工业   66088篇
金属工艺   23557篇
机械仪表   25837篇
建筑科学   31615篇
矿业工程   13153篇
能源动力   11189篇
轻工业   28839篇
水利工程   7998篇
石油天然气   25202篇
武器工业   3465篇
无线电   44382篇
一般工业技术   43440篇
冶金工业   19678篇
原子能技术   4100篇
自动化技术   52785篇
  2024年   1509篇
  2023年   6316篇
  2022年   11532篇
  2021年   16616篇
  2020年   12230篇
  2019年   9843篇
  2018年   11326篇
  2017年   12508篇
  2016年   11436篇
  2015年   16151篇
  2014年   20284篇
  2013年   23961篇
  2012年   26724篇
  2011年   29287篇
  2010年   25787篇
  2009年   24518篇
  2008年   23911篇
  2007年   22732篇
  2006年   22714篇
  2005年   19796篇
  2004年   13585篇
  2003年   12156篇
  2002年   11542篇
  2001年   10147篇
  2000年   9607篇
  1999年   9915篇
  1998年   7450篇
  1997年   6356篇
  1996年   5972篇
  1995年   4927篇
  1994年   3994篇
  1993年   2721篇
  1992年   2138篇
  1991年   1611篇
  1990年   1266篇
  1989年   1008篇
  1988年   839篇
  1987年   503篇
  1986年   404篇
  1985年   247篇
  1984年   192篇
  1983年   143篇
  1982年   140篇
  1981年   80篇
  1980年   115篇
  1979年   52篇
  1978年   18篇
  1977年   23篇
  1976年   28篇
  1951年   15篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
1.
Feng  Wenran  Li  Zhen  Chen  Yingying  Chen  Jinyang  Lang  Haoze  Wan  Jianghong  Gao  Yan  Dong  Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in...  相似文献   
2.
Zhao  Jiandong  Lei  Wei  Li  Zijian  Zhao  Dongfeng  Han  Mingmin  Hou  Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding...  相似文献   
3.
张鹏  丰梦  陈伟  杨鑫  周洁  胡东林 《变压器》2021,58(9):58-62
本文中作者研究了温度对油浸式变压器绝缘纸老化水平的影响,开展了频域介电谱测试得出不同的试验温度下绝缘纸的电导率频域谱.推导了温度、电导率和相对介电常数之间的作用情况,并进行实例验证.  相似文献   
4.
5.
6.
7.
8.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
9.
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field.  相似文献   
10.
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity.  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