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   480047篇
  免费   8212篇
  国内免费   5834篇
化学   231386篇
晶体学   7157篇
力学   26771篇
综合类   334篇
数学   79083篇
物理学   149362篇
  2022年   3996篇
  2021年   5349篇
  2020年   5862篇
  2019年   6403篇
  2018年   17022篇
  2017年   16842篇
  2016年   15793篇
  2015年   6994篇
  2014年   10127篇
  2013年   20169篇
  2012年   20020篇
  2011年   28752篇
  2010年   19570篇
  2009年   19922篇
  2008年   22879篇
  2007年   24591篇
  2006年   15335篇
  2005年   14373篇
  2004年   13628篇
  2003年   12624篇
  2002年   11843篇
  2001年   12597篇
  2000年   9477篇
  1999年   7398篇
  1998年   6403篇
  1997年   5989篇
  1996年   5709篇
  1995年   4850篇
  1994年   4839篇
  1993年   4642篇
  1992年   4940篇
  1991年   5191篇
  1990年   4960篇
  1989年   4804篇
  1988年   4474篇
  1987年   4583篇
  1986年   4381篇
  1985年   5325篇
  1984年   5357篇
  1983年   4487篇
  1982年   4530篇
  1981年   4212篇
  1980年   4144篇
  1979年   4492篇
  1978年   4457篇
  1977年   4437篇
  1976年   4467篇
  1975年   4212篇
  1974年   4225篇
  1973年   4245篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Gas-sensitive properties of SnO2 thin-film materials doped with antimony(III) with respect to the reducing gases CO, CH4, and H2 were studied. The materials were obtained from film-forming solutions of Sn(II) and Sb(III) complexes with acetylacetone.  相似文献   
995.
The possibility of obtaining dispersed powders of cobalt and zinc-nickel ferrites with particle size of 1-4 m by thermal treatment of the corresponding oxalates was analyzed. Changes in porous characteristics of the ferrites obtained in their thermal treatment were studied.  相似文献   
996.
The absolute fission yields of twenty seven fission products were determined in the fast neutron induced fission of 233U, employing track etch in combination with gamma-ray spectrometry. The total number of fissions was measured by registering the fission tracks on a small strip of lexan, a solid state track detector. The fission products were analysed by gamma-ray spectrometry. The measured yield values were compared to the ENDF/B-VI compilation and show a good agreement.  相似文献   
997.
998.
The results are given of a determination of the steady-state concentrations of peroxide compounds on the oxidation of lignin by oxygen in dioxane. An iodometric method of determining peroxides was used, with spectrophotometric control of the amount of iodine formed. It was established that the achievable steady-state concentration of peroxide compounds on the oxidation of lignin is 0.28–0.44 wt. % of Oact (oxygen pressure 1 atm, temperature 50–80°C). With a rise in the temperature, the steady-state concentration of peroxide compounds decreased. The addition of water (30 vol. %) to the organic solvent led to an increase in the rate of accumulation of peroxide compounds. It has been shown that the presence of alkaline and acidic catalysts exerts no appreciable influence on the achievable steady-state concentration and the rate of accumulation of peroxide compounds during the oxidation of lignin.Bratsk Industrial Institute. All-Union Scientific Production Combine of the Pulp and Paper Industry, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 413–417, May–August, 1992.  相似文献   
999.
A series of poly(styrene)/poly(styrene-co-acrylonitrile) core-shell latexes were synthesized by seeded emulsion polymerization. The dried latex was dissolved in toluene and then cast on the surface of water to form a very thin film (60–90 nm). Phase separation in the thin film was studied by transmission electron microscopy (TEM). Electron micrographs of these thin films yielded fine structure and interesting morphology that was unattainable by ultramicrotoming of the corresponding compression-molded specimens. Glass transition temperatures and percent grafted polystyrene were correlated with the TEM results. As grafting increases, mixing of the two phases improves, with the resulting Tg value being between the two Tg's of poly(styrene) and poly(styrene-co-acrylonitrile).  相似文献   
1000.
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