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   176711篇
  免费   1878篇
  国内免费   219篇
电工技术   2682篇
综合类   125篇
化学工业   28368篇
金属工艺   9784篇
机械仪表   6290篇
建筑科学   3170篇
矿业工程   1887篇
能源动力   3047篇
轻工业   9427篇
水利工程   2756篇
石油天然气   8702篇
武器工业   12篇
无线电   16186篇
一般工业技术   40035篇
冶金工业   28402篇
原子能技术   7070篇
自动化技术   10865篇
  2021年   1821篇
  2019年   1749篇
  2018年   3211篇
  2017年   3356篇
  2016年   3654篇
  2015年   1894篇
  2014年   3284篇
  2013年   6869篇
  2012年   4847篇
  2011年   6045篇
  2010年   4891篇
  2009年   5386篇
  2008年   5395篇
  2007年   5222篇
  2006年   4465篇
  2005年   4112篇
  2004年   3899篇
  2003年   3749篇
  2002年   3692篇
  2001年   3670篇
  2000年   3560篇
  1999年   3402篇
  1998年   7318篇
  1997年   5322篇
  1996年   3957篇
  1995年   3008篇
  1994年   2689篇
  1993年   2794篇
  1992年   2295篇
  1991年   2356篇
  1990年   2444篇
  1989年   2345篇
  1988年   2341篇
  1987年   2219篇
  1986年   2263篇
  1985年   2304篇
  1984年   2217篇
  1983年   2148篇
  1982年   1990篇
  1981年   2207篇
  1980年   2060篇
  1979年   2273篇
  1978年   2432篇
  1977年   2440篇
  1976年   3105篇
  1975年   2247篇
  1974年   2312篇
  1973年   2343篇
  1972年   2155篇
  1971年   1912篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
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   
3.
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   
4.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
5.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
6.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
7.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium...  相似文献   
8.
Russian Engineering Research - Digital tools for managing improvements in automobile production are developed. An operative tool provides warnings regarding the operational quality of the vehicles...  相似文献   
9.
Theoretical Foundations of Chemical Engineering - Using gas–liquid chromatography, the activity coefficients upon the infinite dilution of the components of the reaction mixture for obtaining...  相似文献   
10.
Ceria-based solid solutions are important materials for high- and medium-temperature electrochemical applications. However, the stabilities of both binary and ternary ceria-based solid solutions are insufficient at elevated temperatures, which limits their application as solid electrolytes or SOFC cathodes. Data on the high-temperature stability of ceria-based ceramics are unavailable in the literature. In the present study, we report a thermodynamic stability investigation of Y2O3-CeO2 and Y2O3-ZrO2-CeO2 solid solutions. The thermal prehistories of binary and ternary systems were investigated using STA, XRD, and ESCA techniques. The vaporization processes were investigated in the temperature range of 1577–2227°С via the Knudsen effusion mass spectrometry technique. Using data on the component activity in solid-phase thermodynamic properties of Y2O3-CeO2 solid solutions, which is represented as the Gibbs energy, the excess Gibbs energy was calculated as a function of the ceria mol. %. It was shown that the reduction of Ce4+ to Ce3+ in Y2O3-CeO2 and Y2O3-ZrO2-CeO2 solid solutions corresponds to less-negative Gibbs energy compared to ZrO2-CeO2 solid solutions.  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