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   206745篇
  免费   2209篇
  国内免费   569篇
电工技术   3540篇
综合类   141篇
化学工业   31979篇
金属工艺   10279篇
机械仪表   7017篇
建筑科学   4003篇
矿业工程   2161篇
能源动力   4660篇
轻工业   12903篇
水利工程   2921篇
石油天然气   7726篇
武器工业   22篇
无线电   21574篇
一般工业技术   45249篇
冶金工业   34533篇
原子能技术   6634篇
自动化技术   14181篇
  2021年   2061篇
  2019年   2004篇
  2018年   3682篇
  2017年   3724篇
  2016年   4002篇
  2015年   2235篇
  2014年   3794篇
  2013年   8759篇
  2012年   5695篇
  2011年   7237篇
  2010年   5875篇
  2009年   6506篇
  2008年   6636篇
  2007年   6512篇
  2006年   5586篇
  2005年   5138篇
  2004年   4642篇
  2003年   4575篇
  2002年   4381篇
  2001年   4488篇
  2000年   4201篇
  1999年   4218篇
  1998年   10245篇
  1997年   7218篇
  1996年   5536篇
  1995年   4143篇
  1994年   3619篇
  1993年   3860篇
  1992年   2990篇
  1991年   2999篇
  1990年   2900篇
  1989年   2861篇
  1988年   2869篇
  1987年   2510篇
  1986年   2578篇
  1985年   2863篇
  1984年   2695篇
  1983年   2560篇
  1982年   2310篇
  1981年   2276篇
  1980年   2350篇
  1979年   2362篇
  1978年   2385篇
  1977年   2489篇
  1976年   2883篇
  1975年   2191篇
  1974年   2069篇
  1973年   2168篇
  1972年   1940篇
  1971年   1757篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Conclusions The process of drying cellulose triacetate in a vibrating bed has been studied.For final drying of cellulose triacetate before solution, it is recommended to use an industrial specimen of a unit with a vibrating bed having a capacity of 2700 kg/h.This assembly can be used to dry other fibre-forming disperse polymeric materials containing strongly bound moisture.Translated from Khimicheskie Volokna, No. 3, pp. 49–51, May–June, 1984.  相似文献   
74.
Conclusions The change in some properties of polyvinyl fluoride during the process of fibre spinning has been investigated.It has been found that during the process of converting PVF powder into fibre, the degree of polymer crystallinity plus its resistance to thermal and thermooxidative degradation is increased; depending on the spinning regime, the densities and physicomechanical properties of PVF fibres are different.Translated from Khimicheskie Volokna, No. 4, pp. 34–35, July–August, 1984.  相似文献   
75.
Unsaturated Polyester resins were prepared by the reaction of cinnamylsuccinic acid with saturated diols, namely, ethylene, diethylene, propylene, dipropylene, tetramethylene, and hexamethylene glycols, and the unsaturated diols, namely, 1,4-butene- and 1,4-butynediols. All the polyester resins obtained have been characterized and were found to cure with styrene, with relatively low conversions. The properties of the cured polyesters in the form of films were determined. IR and 1H-NMR spectroscopy were used for both qualitative and quantitative analyses of the polyesters and their hydrolyzate products, after curing with styrene.  相似文献   
76.
77.
78.
79.
80.
Groups of 32 and 16 subjects of both sexes were exposed in an environmental chamber to radiant asymmetry caused by a cool wall, a warm wall, and a cool ceiling. Each subject was tested individually while seated and clothed at 0.6 clo. During each 3.5-hour experiment the subject was exposed to six radiant temperature asymmetries. He was asked whether and where he experienced any local cool or warm sensation, and whether it was felt to be uncomfortable. During the entire experiment he was kept thermally neutral by changing the air temperature according to his wishes.For cool walls, warm walls, and cool ceilings curves have been established showing the percentage of dissatisfied subjects as a function of the radiant asymmetry. Radiant asymmetry at a warm wall caused less discomfort than a cool wall. A cool ceiling caused less discomfort than a warm ceiling. Accepting that 5% of the subjects may feel uncomfortable. a radiant temperature asymmetry of 10°C is allowable at a cool wall, 23°C at a warm wall, and 14°C under a cool ceiling. A previous study showed that 4°C is allowable under a warm ceiling. Radiant asymmetry had no significant impact on the operative temperatures preferred by the subjects. No significant differences were observed between the responses of men and women exposed to radiant asymmetry.  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