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   2135738篇
  免费   64352篇
  国内免费   26015篇
电工技术   61736篇
技术理论   45篇
综合类   35903篇
化学工业   351617篇
金属工艺   90351篇
机械仪表   76590篇
建筑科学   85774篇
矿业工程   26542篇
能源动力   62596篇
轻工业   165106篇
水利工程   25308篇
石油天然气   66420篇
武器工业   3884篇
无线电   248049篇
一般工业技术   360080篇
冶金工业   292418篇
原子能技术   38819篇
自动化技术   234867篇
  2022年   23581篇
  2021年   33854篇
  2020年   25839篇
  2019年   25804篇
  2018年   31356篇
  2017年   32655篇
  2016年   35717篇
  2015年   35152篇
  2014年   50741篇
  2013年   114302篇
  2012年   68742篇
  2011年   86340篇
  2010年   72915篇
  2009年   78338篇
  2008年   75959篇
  2007年   72810篇
  2006年   72891篇
  2005年   65068篇
  2004年   58704篇
  2003年   56454篇
  2002年   53906篇
  2001年   50601篇
  2000年   48923篇
  1999年   51686篇
  1998年   86365篇
  1997年   66526篇
  1996年   55621篇
  1995年   44450篇
  1994年   39989篇
  1993年   38236篇
  1992年   30745篇
  1991年   27756篇
  1990年   27352篇
  1989年   26125篇
  1988年   24484篇
  1987年   22067篇
  1986年   21503篇
  1985年   24572篇
  1984年   23694篇
  1983年   21555篇
  1982年   20305篇
  1981年   20517篇
  1980年   19118篇
  1979年   19352篇
  1978年   18587篇
  1977年   20174篇
  1976年   24607篇
  1975年   16628篇
  1974年   16029篇
  1973年   16123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.
4.
Journal of Materials Science -  相似文献   
5.
6.
Grachev  A. I. 《Semiconductors》2022,56(2):67-70
Semiconductors - In this work, we discuss for the first time the principle of rotation in the constant electric field of a conducting particle with participation of the Lorentz force, which ensures...  相似文献   
7.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
8.
Hepatic fibrosis occurs when liver tissue becomes scarred from repetitive liver injury and inflammatory responses; it can progress to cirrhosis and eventually to hepatocellular carcinoma. Previously, we reported that neoagarooligosaccharides (NAOs), produced by the hydrolysis of agar by β-agarases, have hepatoprotective effects against acetaminophen overdose-induced acute liver injury. However, the effect of NAOs on chronic liver injury, including hepatic fibrosis, has not yet been elucidated. Therefore, we examined whether NAOs protect against fibrogenesis in vitro and in vivo. NAOs ameliorated PAI-1, α-SMA, CTGF and fibronectin protein expression and decreased mRNA levels of fibrogenic genes in TGF-β-treated LX-2 cells. Furthermore, downstream of TGF-β, the Smad signaling pathway was inhibited by NAOs in LX-2 cells. Treatment with NAOs diminished the severity of hepatic injury, as evidenced by reduction in serum alanine aminotransferase and aspartate aminotransferase levels, in carbon tetrachloride (CCl4)-induced liver fibrosis mouse models. Moreover, NAOs markedly blocked histopathological changes and collagen accumulation, as shown by H&E and Sirius red staining, respectively. Finally, NAOs antagonized the CCl4-induced upregulation of the protein and mRNA levels of fibrogenic genes in the liver. In conclusion, our findings suggest that NAOs may be a promising candidate for the prevention and treatment of chronic liver injury via inhibition of the TGF-β/Smad signaling pathway.  相似文献   
9.
Koroteev  A. S. 《Atomic Energy》2021,130(4):202-208
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,...  相似文献   
10.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  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