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   529412篇
  免费   4175篇
  国内免费   1284篇
化学   269600篇
晶体学   7660篇
力学   25998篇
综合类   17篇
数学   67814篇
物理学   163782篇
  2021年   5040篇
  2020年   5486篇
  2019年   6231篇
  2018年   8421篇
  2017年   8563篇
  2016年   11631篇
  2015年   6184篇
  2014年   10458篇
  2013年   23510篇
  2012年   18382篇
  2011年   21830篇
  2010年   16435篇
  2009年   16302篇
  2008年   20714篇
  2007年   20542篇
  2006年   18647篇
  2005年   16657篇
  2004年   15505篇
  2003年   13989篇
  2002年   13884篇
  2001年   14753篇
  2000年   11355篇
  1999年   8763篇
  1998年   7611篇
  1997年   7480篇
  1996年   6943篇
  1995年   6272篇
  1994年   6273篇
  1993年   6030篇
  1992年   6386篇
  1991年   6877篇
  1990年   6585篇
  1989年   6492篇
  1988年   6330篇
  1987年   6142篇
  1986年   5886篇
  1985年   7418篇
  1984年   7778篇
  1983年   6546篇
  1982年   6825篇
  1981年   6332篇
  1980年   6010篇
  1979年   6515篇
  1978年   6749篇
  1977年   6637篇
  1976年   6596篇
  1975年   6312篇
  1974年   6135篇
  1973年   6435篇
  1972年   4708篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases Tmp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994.  相似文献   
42.
By changing the conditions of the electrohydraulic treatment of aqueous plant heterodisperse systems comparatively high degradation of the lignin component of plant tissue has been achieved. In addition to free monosaccharides, their reduced forms have been detected in the aqueous phase. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 795–798, November–December, 1994.  相似文献   
43.
44.
The influence of sunflowerseed and cottonseed oils and also of fractions of normal and oxidized triacylglycerols isolated from them on cytochrome P-450 from rat liver microsomes has been investigated.  相似文献   
45.
6-Halogeno-1,3-benzodioxane analogs of chalcones have been synthesized by various methods. Flavanone and flavone analogs of silandrin and hydnocarpin have been obtained from them. The structures of the new flavonoids have been shown by their PMR spectra.  相似文献   
46.
The electron-impact mass spectra of a number of phenylpropanoids and iridoid glycosides containing a phenylethanoid fragment in their structure have been studied. This has revealed features of the formation of fragments of 4-hydroxyphenylethyl and 3,4-dihydroxyphenylethyl alcohols and also of fragments of phenylethylamine and indolylethylamine derivatives present in the structures of the compounds investigated.  相似文献   
47.
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties.  相似文献   
48.
49.
The phsicochemical indices and the fatty-acid and triacylglycerol compositions of cottonseed and palm oils, of cottonseed oil hydrogenate, and of compositions based on them have been determined with the aid of IR and UV spectroscopies, GLC analysis, and chemical transformations. The compositions and amounts of the main classes of lipids in the initial oils and the hydrogenate have been studied. It has been found that in the process of hydrogenation the amount of oxygenated components falls. The work was conducted with the financial support of the Uzbek Fund for Fundamental Investigations.  相似文献   
50.
Institute of Botany, Academy of Sciences of the Republic of Azerbaidzhan, Baku. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 291–292, March–April, 1994.  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