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   409563篇
  免费   43129篇
  国内免费   16744篇
电工技术   23014篇
技术理论   46篇
综合类   27271篇
化学工业   78505篇
金属工艺   22138篇
机械仪表   24593篇
建筑科学   30560篇
矿业工程   12189篇
能源动力   11329篇
轻工业   32007篇
水利工程   7512篇
石油天然气   24092篇
武器工业   2966篇
无线电   46873篇
一般工业技术   51051篇
冶金工业   19479篇
原子能技术   3956篇
自动化技术   51855篇
  2024年   1251篇
  2023年   5499篇
  2022年   10179篇
  2021年   14507篇
  2020年   11872篇
  2019年   11383篇
  2018年   12779篇
  2017年   14330篇
  2016年   13735篇
  2015年   17963篇
  2014年   21800篇
  2013年   26621篇
  2012年   26488篇
  2011年   28721篇
  2010年   26039篇
  2009年   24579篇
  2008年   23789篇
  2007年   22754篇
  2006年   22823篇
  2005年   19965篇
  2004年   14110篇
  2003年   12943篇
  2002年   12417篇
  2001年   10971篇
  2000年   10471篇
  1999年   10343篇
  1998年   7558篇
  1997年   6482篇
  1996年   6099篇
  1995年   4997篇
  1994年   4041篇
  1993年   2745篇
  1992年   2180篇
  1991年   1658篇
  1990年   1298篇
  1989年   1052篇
  1988年   856篇
  1987年   521篇
  1986年   429篇
  1985年   256篇
  1984年   201篇
  1983年   151篇
  1982年   139篇
  1981年   87篇
  1980年   113篇
  1979年   51篇
  1978年   23篇
  1977年   31篇
  1976年   37篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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