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   524篇
  免费   9篇
电工技术   3篇
化学工业   47篇
金属工艺   35篇
机械仪表   19篇
建筑科学   1篇
能源动力   9篇
水利工程   14篇
石油天然气   131篇
无线电   37篇
一般工业技术   137篇
冶金工业   44篇
原子能技术   6篇
自动化技术   50篇
  2022年   5篇
  2021年   6篇
  2020年   5篇
  2019年   7篇
  2018年   9篇
  2017年   12篇
  2016年   15篇
  2015年   6篇
  2014年   11篇
  2013年   13篇
  2012年   14篇
  2011年   31篇
  2010年   13篇
  2009年   14篇
  2008年   22篇
  2007年   16篇
  2006年   7篇
  2005年   9篇
  2004年   18篇
  2003年   18篇
  2002年   12篇
  2001年   10篇
  2000年   15篇
  1999年   9篇
  1998年   10篇
  1997年   12篇
  1996年   11篇
  1995年   7篇
  1994年   11篇
  1993年   16篇
  1992年   12篇
  1991年   12篇
  1990年   8篇
  1989年   6篇
  1987年   10篇
  1983年   5篇
  1982年   6篇
  1981年   5篇
  1980年   5篇
  1979年   5篇
  1978年   6篇
  1977年   10篇
  1976年   6篇
  1975年   6篇
  1974年   6篇
  1973年   6篇
  1972年   7篇
  1971年   6篇
  1970年   7篇
  1968年   7篇
排序方式: 共有533条查询结果,搜索用时 31 毫秒
501.
502.
503.
Abstract Acryloyl chloride (AC) was radiation grafted from 30% solution of monomer in toluene onto polydiethyleneglycol-bis-allylcarbonate (CR-39) by their simultaneous -iradiation. The grafting process was more efficient at dose rate of 4.4 kGy/h as compared with 0.4 kGy/h, and grafting values of 15-18% were achieved at 2.2-5.5 kGy. Subsequent immobilization of disperse red 1 (DR1) onto the grafted polymer was carried out from 0.02 M solution of this dye in dichloroethane, and the immobilized DR1 yield increased with the grafted polyAC value. Surfaces of the starting and modifed CR-39 were characterized with the FTIR-ATR spectroscopy and atomic force microscopy. An essential difference in chemical structure and topography of the CR-39 surface before and after the DR1 immobilization has been shown. The colourless plates of CR-39 became red after the DR1 immobilization, and the color intensity increased with the dye content. Changes in visible absorption spectra of the immobilzed DR1 caused by the photoinduced trans-cis isomerization of this dye were discussed.  相似文献   
504.
Flame propagation in a closed deformable channel   总被引:1,自引:0,他引:1  
Izhevsk. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 3, pp. 27–33, May–June, 1990.  相似文献   
505.
Volumetric (PVT) and calorimetric (C V VT) properties of pure methanol were measured in the liquid phase with a twin-cell adiabatic calorimeter. Temperatures were measured in a range from 314 to 411 K, densities between 699.3 and 775.6 kgm–3, and pressures to 20 MPa. The calorimetric cell (70 cm3 capacity) was surrounded by adiabatic thermal shielding (high vacuum). The sample pressures were measured by means of a quartz crystal transducer to within an uncertainty of about ±7 kPa. The relative uncertainty of C V was estimated to be 2%, with a coverage factor k = 2, by combining the various sources of experimental uncertainty using a root-sum-of-squares formula. The results for pure methanol were compared with other recent measurements performed with a second high-temperature, high-pressure adiabatic calorimeter. Deviations of less than 3% were found between the earlier C V data and the present results for pure methanol. The uncertainty of the density measurements was estimated to be 0.2% (k = 2). The measured densities and isochoric heat capacities were compared with values calculated with an IUPAC equation of state. Agreement of density was within 0.088% and that for isochoric heat capacity was within 0.95%. Values of vapor pressure were determined by extrapolating experimental PT data to the saturated temperature along a fixed isochore. In the temperature range of this study, decomposition of methanol was not observed.  相似文献   
506.
Methane activation on magnesium-oxide-cased catalysts for methane dehydrodimerization has been studied. As found, the rate of dehydrodimerization changes proportionally with the concentration of base sites on the catalytic surface. The activation of methane results in the formation of the methyl anion, as ascertained by IR-Fourier spectroscopy. The dehydrodimerization rates have been compared with the concentration of one-electron sites and the rate of the CH4---CD4 isotope exchange. Based on the data obtained a new mechanism of methane dehydrodimerization has been proposed; at the first reaction step a fast heterolytic dissociation of methane on base sites takes place. The rate-determining step is that of the metal-methyl dissociation leading to the formation of the methyl radical which determines a high activation energy of methane dehydrodimerization on oxide catalysts.  相似文献   
507.
508.
509.
510.
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