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   171142篇
  免费   12730篇
  国内免费   6566篇
电工技术   9292篇
技术理论   9篇
综合类   9335篇
化学工业   27617篇
金属工艺   10281篇
机械仪表   10489篇
建筑科学   10186篇
矿业工程   4127篇
能源动力   3747篇
轻工业   10016篇
水利工程   3342篇
石油天然气   9699篇
武器工业   1157篇
无线电   17900篇
一般工业技术   27052篇
冶金工业   11136篇
原子能技术   4967篇
自动化技术   20086篇
  2023年   2287篇
  2022年   4401篇
  2021年   6410篇
  2020年   4836篇
  2019年   4098篇
  2018年   5212篇
  2017年   5631篇
  2016年   5189篇
  2015年   5859篇
  2014年   7622篇
  2013年   9270篇
  2012年   10081篇
  2011年   10830篇
  2010年   9242篇
  2009年   8998篇
  2008年   8950篇
  2007年   8436篇
  2006年   7729篇
  2005年   6590篇
  2004年   5022篇
  2003年   4867篇
  2002年   4880篇
  2001年   4430篇
  2000年   3831篇
  1999年   3337篇
  1998年   2613篇
  1997年   2201篇
  1996年   1964篇
  1995年   1727篇
  1994年   1449篇
  1993年   1239篇
  1992年   1210篇
  1991年   1075篇
  1990年   1083篇
  1989年   1003篇
  1988年   890篇
  1987年   831篇
  1986年   755篇
  1985年   715篇
  1984年   700篇
  1982年   666篇
  1981年   670篇
  1979年   737篇
  1978年   777篇
  1977年   739篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
141.
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being.  相似文献   
142.
随着科学技术水平的不断提高,在学校教育中应用多媒体CAI的现象越来越普遍,并且受到了广大师生的喜爱。在篮球技术教学中,多媒体CAI课件得到了广泛的应用,并且发挥了非常重要的作用,促进了学生篮球技术水平的提高,实现了预期的教学效果。  相似文献   
143.
144.
Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb2+ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement.  相似文献   
145.
146.
147.
Powder Metallurgy and Metal Ceramics - Multiphase La 2 MgNi 9 alloys are synthesized by induction melting. The crystalline structures of all phases in the alloys are determined with X-ray...  相似文献   
148.
149.
150.
It has been well known that the greening of Allium sativum cloves could be formed after immersed in acetic acid solution. Nonetheless, no investigation was reported on colour development of A. sativum in response to acetic acid vapour until now. In this study, the brief exposure of A. sativum to acetic acid vapour (200–400 ppm) was combined with controlled atmosphere (5%, 20% and 80% CO2) packaging storage to break cell membrane and green garlic. The garlic bulbs were fumigated with acetic acid before controlled CO2 atmosphere packaging for 25 days at 4 °C. Fumigation with 200 ppm acetic acid followed by high CO2 atmosphere packaging (80% CO2) facilitated the garlic greening. It was also verified that γ‐glutamyl transpeptidase was involved in garlic greening in present study, and the compromise of glacial acetic acid vapour fumigation and CO2 gas atmosphere in package stored at low temperature could result in garlic greening as well.  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