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   124925篇
  免费   31943篇
  国内免费   35264篇
化学   82432篇
晶体学   3421篇
力学   8344篇
综合类   2410篇
数学   17962篇
物理学   77563篇
  2023年   1054篇
  2022年   2500篇
  2021年   2368篇
  2020年   2508篇
  2019年   2891篇
  2018年   2878篇
  2017年   4438篇
  2016年   3629篇
  2015年   4727篇
  2014年   5234篇
  2013年   7421篇
  2012年   8104篇
  2011年   10146篇
  2010年   13773篇
  2009年   14373篇
  2008年   8849篇
  2007年   7923篇
  2006年   7312篇
  2005年   6943篇
  2004年   6795篇
  2003年   5098篇
  2002年   5044篇
  2001年   5305篇
  2000年   4837篇
  1999年   3837篇
  1998年   2824篇
  1997年   2379篇
  1996年   2599篇
  1995年   3136篇
  1994年   3136篇
  1993年   3222篇
  1992年   2751篇
  1991年   2324篇
  1990年   2012篇
  1989年   2109篇
  1988年   2019篇
  1987年   1313篇
  1986年   1320篇
  1985年   947篇
  1984年   1089篇
  1983年   446篇
  1982年   955篇
  1981年   799篇
  1980年   809篇
  1979年   608篇
  1978年   553篇
  1977年   640篇
  1976年   1052篇
  1972年   532篇
  1971年   445篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
The qualitative and quantitative compositions of the carbohydrates of the leaf vegetables Lactuca sativa L., Spinacea oleracea L., and Rumex acetosa L. have been studied.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 349–351, May–June, 1993.  相似文献   
83.
The preparation and spectral properties of rhamnose orthoacetates of aconitine and imperialine are described.Tashkent Pharmaceutical Institute. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 743–746, September–October, 1993.  相似文献   
84.
85.
86.
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.  相似文献   
87.
88.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition.  相似文献   
89.
The properties of a polymer-concrete composed of polyester matrix and locally available rock aggregate are investigated. The formula of the concrete is found by an experimental-calculation approach in such a way as to attain a closer packing of the aggregate particles on the one hand, and to ensure the needed processing characteristics (placeability) of the mix on the other. It is shown experimentally that the material obtained has a rather high compression strength. Under prolonged compression loads, the polymer-concrete exhibits a noticeable creep behavior with a linear relation between the creep strains and stresses. After the action of half the ultimate load over 3000 h, the total strains exceed the instantaneous ones by 2.0 to 2.2 times. The accumulation of irreversible strains is also observed; however, their contribution to the total strain is small. It is found that the stress-strain relation can be represented by the equation of linear hereditary creep theory.Institute of Polymer Mechanics, University of Latvia, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 147–162, March–April, 1999.  相似文献   
90.
环状连续强激光下光学薄膜的瞬温和热畸变   总被引:1,自引:0,他引:1       下载免费PDF全文
详细研究了非冷却光学薄膜元件在环形激光光束辐照下的瞬态温度分布和随后的热畸变,并且用泰曼干涉仪实际测量了连续波氧碘激光辐照各种非冷却光学元件的热畸变量并与理论计算相比较,分析结果表明理论和实验相一致。  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