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   582531篇
  免费   50592篇
  国内免费   28187篇
电工技术   38391篇
技术理论   55篇
综合类   42300篇
化学工业   92483篇
金属工艺   33030篇
机械仪表   37279篇
建筑科学   45527篇
矿业工程   18058篇
能源动力   16317篇
轻工业   41683篇
水利工程   12415篇
石油天然气   33141篇
武器工业   5246篇
无线电   66811篇
一般工业技术   64113篇
冶金工业   28714篇
原子能技术   6444篇
自动化技术   79303篇
  2024年   2139篇
  2023年   8613篇
  2022年   17192篇
  2021年   23759篇
  2020年   17546篇
  2019年   13748篇
  2018年   16183篇
  2017年   18123篇
  2016年   16368篇
  2015年   23336篇
  2014年   29775篇
  2013年   35958篇
  2012年   39730篇
  2011年   43592篇
  2010年   38315篇
  2009年   35843篇
  2008年   35578篇
  2007年   33690篇
  2006年   32735篇
  2005年   27978篇
  2004年   19031篇
  2003年   16379篇
  2002年   15354篇
  2001年   13525篇
  2000年   13111篇
  1999年   13349篇
  1998年   10639篇
  1997年   9022篇
  1996年   8408篇
  1995年   6956篇
  1994年   5662篇
  1993年   4031篇
  1992年   3244篇
  1991年   2440篇
  1990年   1918篇
  1989年   1611篇
  1988年   1310篇
  1987年   866篇
  1986年   713篇
  1985年   568篇
  1984年   434篇
  1983年   391篇
  1982年   330篇
  1981年   267篇
  1980年   288篇
  1979年   200篇
  1978年   142篇
  1977年   138篇
  1976年   166篇
  1973年   94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.
Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO2-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag+/Nb5+ co-doped (Ag1/4Nb3/4)xTi1−xO2 (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 103 and 1.6 × 104 at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics.  相似文献   
3.
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   
4.
5.
6.
7.
8.
9.
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results.  相似文献   
10.
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   
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