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   635630篇
  免费   15824篇
  国内免费   6927篇
电工技术   15711篇
技术理论   12篇
综合类   8939篇
化学工业   94872篇
金属工艺   28551篇
机械仪表   21878篇
建筑科学   19550篇
矿业工程   5824篇
能源动力   14678篇
轻工业   51069篇
水利工程   8170篇
石油天然气   14204篇
武器工业   1082篇
无线电   72084篇
一般工业技术   118163篇
冶金工业   95848篇
原子能技术   12763篇
自动化技术   74983篇
  2022年   4931篇
  2021年   7788篇
  2020年   5656篇
  2019年   5821篇
  2018年   22231篇
  2017年   21280篇
  2016年   18537篇
  2015年   8709篇
  2014年   12210篇
  2013年   26323篇
  2012年   21477篇
  2011年   32323篇
  2010年   26687篇
  2009年   25375篇
  2008年   27374篇
  2007年   28072篇
  2006年   18523篇
  2005年   17357篇
  2004年   15594篇
  2003年   14600篇
  2002年   13641篇
  2001年   13067篇
  2000年   12367篇
  1999年   12528篇
  1998年   27452篇
  1997年   19869篇
  1996年   15520篇
  1995年   11809篇
  1994年   10555篇
  1993年   10383篇
  1992年   7846篇
  1991年   7423篇
  1990年   7331篇
  1989年   7270篇
  1988年   6762篇
  1987年   5953篇
  1986年   5960篇
  1985年   6618篇
  1984年   6275篇
  1983年   5800篇
  1982年   5250篇
  1981年   5500篇
  1980年   5219篇
  1979年   5173篇
  1978年   5144篇
  1977年   5518篇
  1976年   7238篇
  1975年   4477篇
  1974年   4268篇
  1973年   4294篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
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.
张鹏  丰梦  陈伟  杨鑫  周洁  胡东林 《变压器》2021,58(9):58-62
本文中作者研究了温度对油浸式变压器绝缘纸老化水平的影响,开展了频域介电谱测试得出不同的试验温度下绝缘纸的电导率频域谱.推导了温度、电导率和相对介电常数之间的作用情况,并进行实例验证.  相似文献   
4.
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   
5.
6.
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   
7.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
8.
Fan  Deng-Ping  Huang  Ziling  Zheng  Peng  Liu  Hong  Qin  Xuebin  Van Gool  Luc 《国际自动化与计算杂志》2022,19(4):257-287
Machine Intelligence Research - This paper aims to conduct a comprehensive study on facial-sketch synthesis (FSS). However, due to the high cost of obtaining hand-drawn sketch datasets, there is a...  相似文献   
9.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
10.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  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