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   591612篇
  免费   4118篇
  国内免费   1258篇
化学   272096篇
晶体学   8861篇
力学   33500篇
综合类   24篇
数学   91219篇
物理学   191288篇
  2021年   5189篇
  2020年   5508篇
  2019年   6423篇
  2018年   13357篇
  2017年   13781篇
  2016年   14712篇
  2015年   7016篇
  2014年   11785篇
  2013年   24573篇
  2012年   21726篇
  2011年   29335篇
  2010年   21487篇
  2009年   21835篇
  2008年   26813篇
  2007年   28390篇
  2006年   19359篇
  2005年   19412篇
  2004年   17099篇
  2003年   15972篇
  2002年   15125篇
  2001年   15782篇
  2000年   12303篇
  1999年   9254篇
  1998年   8170篇
  1997年   7844篇
  1996年   7342篇
  1995年   6430篇
  1994年   6390篇
  1993年   6252篇
  1992年   6587篇
  1991年   7122篇
  1990年   6835篇
  1989年   6776篇
  1988年   6405篇
  1987年   6585篇
  1986年   6148篇
  1985年   7476篇
  1984年   7767篇
  1983年   6563篇
  1982年   6724篇
  1981年   6300篇
  1980年   6091篇
  1979年   6725篇
  1978年   6778篇
  1977年   6835篇
  1976年   6881篇
  1975年   6434篇
  1974年   6254篇
  1973年   6456篇
  1972年   5027篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
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   
55.
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   
56.
The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml−1 chloride. For solutions below this concentration, the relation is linear.  相似文献   
57.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
58.
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex variables. Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61.  相似文献   
59.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2] n ·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993.  相似文献   
60.
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