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   8173篇
  免费   525篇
  国内免费   10篇
电工技术   77篇
综合类   3篇
化学工业   2099篇
金属工艺   84篇
机械仪表   200篇
建筑科学   322篇
矿业工程   17篇
能源动力   270篇
轻工业   1429篇
水利工程   107篇
石油天然气   31篇
无线电   447篇
一般工业技术   1109篇
冶金工业   1122篇
原子能技术   30篇
自动化技术   1361篇
  2023年   59篇
  2022年   182篇
  2021年   326篇
  2020年   221篇
  2019年   235篇
  2018年   290篇
  2017年   253篇
  2016年   308篇
  2015年   249篇
  2014年   333篇
  2013年   663篇
  2012年   505篇
  2011年   602篇
  2010年   415篇
  2009年   471篇
  2008年   416篇
  2007年   389篇
  2006年   306篇
  2005年   277篇
  2004年   243篇
  2003年   201篇
  2002年   186篇
  2001年   103篇
  2000年   90篇
  1999年   79篇
  1998年   109篇
  1997年   82篇
  1996年   83篇
  1995年   74篇
  1994年   74篇
  1993年   65篇
  1992年   63篇
  1991年   33篇
  1990年   57篇
  1989年   61篇
  1988年   40篇
  1987年   63篇
  1986年   49篇
  1985年   49篇
  1984年   49篇
  1983年   27篇
  1982年   52篇
  1981年   23篇
  1980年   31篇
  1979年   17篇
  1978年   28篇
  1977年   19篇
  1976年   16篇
  1975年   20篇
  1974年   17篇
排序方式: 共有8708条查询结果,搜索用时 15 毫秒
1.
Several studies have reported that nicotine, the main bioactive component of tobacco, exerts a marked negative energy balance. Apart from its anorectic action, nicotine also modulates energy expenditure, by regulating brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning. These effects are mainly controlled at the central level by modulation of hypothalamic neuropeptide systems and energy sensors, such as AMP-activated protein kinase (AMPK). In this study, we aimed to investigate the kappa opioid receptor (κOR)/dynorphin signaling in the modulation of nicotine’s effects on energy balance. We found that body weight loss after nicotine treatment is associated with a down-regulation of the κOR endogenous ligand dynorphin precursor and with a marked reduction in κOR signaling and the p70 S6 kinase/ribosomal protein S6 (S6K/rpS6) pathway in the lateral hypothalamic area (LHA). The inhibition of these pathways by nicotine was completely blunted in κOR deficient mice, after central pharmacological blockade of κOR, and in rodents where κOR was genetically knocked down specifically in the LHA. Moreover, κOR-mediated nicotine effects on body weight do not depend on orexin. These data unravel a new central regulatory pathway modulating nicotine’s effects on energy balance.  相似文献   
2.
A recent development in tactile technology enables an improvement in the appreciation of the visual arts for people with visual impairment (PVI). The tactile sense, in conjunction with, or a possibly as an alternative to, the auditory sense, would allow PVIs to approach artwork in a more self‐driven and engaging way that would be difficult to achieve with just an auditory stimulus. Tactile colour pictograms (TCPs), which are raised geometric patterns, are ideographic characters that are designed to enable PVIs to identify colours and interpret information by touch. In this article, three TCPs are introduced to code colours in the Munsell colour system. Each colour pattern consists of a basic cell size of 10 mm × 10 mm to represent the patterns consistently in terms of regular shape. Each TCP consists of basic geometric patterns that are combined to create primary, secondary, and tertiary colour pictograms of shapes indicating colour hue, intensity and lightness. Each TCP represents 29 colours including six hues; they were then further expanded to represent 53 colours. Two of them did not increase the cell size, the other increased the cell size 1.5 times for some colours, such as yellow‐orange, yellow, blue, and blue‐purple. Our proposed TCPs use a slightly larger cell size compared to most tactile patterns currently used to indicate colour, but code for more colours. With user experience and identification tests, conducted with 23 visually impaired adults, the effectiveness of the TCPs suggests that they were helpful for the participants.  相似文献   
3.
An alternative for reducing emissions from marine fuel is to blend bio-oil from lignocellulose non-edible feedstocks to diesel fossil fuels. Phase diagrams of the ternary systems were built to represent the transition from heterogeneous regions to homogeneous regions. Four homogeneous blends of bio-oil of eucalyptus-bioethanol-marine gasoil were experimentally characterized with respect to the most important fuel parameters for marine engines: water content, flash point, low heating value, viscosity, and acidity. Blends with closer properties to marine gasoil replacement, lower costs, and environmental impacts should be tested for large engines.  相似文献   
4.
Food Analytical Methods - The habanero pepper (Capsicum chinense Jacq.) is very aromatic and is the hottest pepper in the world. In this study, a headspace solid-phase microextraction/gas...  相似文献   
5.
6.
7.
8.
9.
10.
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