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   437783篇
  免费   44836篇
  国内免费   17846篇
电工技术   24742篇
技术理论   49篇
综合类   29837篇
化学工业   82057篇
金属工艺   24003篇
机械仪表   26716篇
建筑科学   33185篇
矿业工程   13015篇
能源动力   11784篇
轻工业   34044篇
水利工程   8171篇
石油天然气   25634篇
武器工业   3351篇
无线电   49337篇
一般工业技术   53515篇
冶金工业   20684篇
原子能技术   4174篇
自动化技术   56167篇
  2024年   1275篇
  2023年   5605篇
  2022年   10713篇
  2021年   15231篇
  2020年   12433篇
  2019年   11698篇
  2018年   13245篇
  2017年   14890篇
  2016年   14318篇
  2015年   18988篇
  2014年   23091篇
  2013年   28219篇
  2012年   28515篇
  2011年   31090篇
  2010年   28224篇
  2009年   26759篇
  2008年   26051篇
  2007年   24788篇
  2006年   24957篇
  2005年   21870篇
  2004年   15264篇
  2003年   13609篇
  2002年   12817篇
  2001年   11432篇
  2000年   10962篇
  1999年   10956篇
  1998年   8013篇
  1997年   6887篇
  1996年   6439篇
  1995年   5268篇
  1994年   4300篇
  1993年   2921篇
  1992年   2309篇
  1991年   1769篇
  1990年   1383篇
  1989年   1121篇
  1988年   920篇
  1987年   537篇
  1986年   432篇
  1985年   275篇
  1984年   206篇
  1983年   158篇
  1982年   135篇
  1981年   82篇
  1980年   106篇
  1979年   50篇
  1978年   18篇
  1977年   24篇
  1976年   30篇
  1973年   9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.
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   
8.
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   
9.
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   
10.
Neural Processing Letters - The boundedness and the global Mittag-Leffler synchronization (GMLS) of fractional-order inertial Cohen–Grossberg neural networks (CGNNS) with time delays are...  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