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   741篇
  免费   16篇
  国内免费   3篇
化学   592篇
晶体学   5篇
力学   13篇
数学   70篇
物理学   80篇
  2024年   1篇
  2023年   5篇
  2022年   31篇
  2021年   21篇
  2020年   20篇
  2019年   21篇
  2018年   6篇
  2017年   15篇
  2016年   27篇
  2015年   24篇
  2014年   23篇
  2013年   41篇
  2012年   43篇
  2011年   50篇
  2010年   32篇
  2009年   33篇
  2008年   49篇
  2007年   52篇
  2006年   43篇
  2005年   40篇
  2004年   28篇
  2003年   28篇
  2002年   33篇
  2001年   7篇
  2000年   10篇
  1999年   17篇
  1998年   9篇
  1997年   3篇
  1996年   8篇
  1995年   6篇
  1994年   2篇
  1993年   3篇
  1992年   3篇
  1990年   2篇
  1989年   4篇
  1988年   2篇
  1987年   2篇
  1986年   3篇
  1985年   2篇
  1984年   4篇
  1983年   2篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
排序方式: 共有760条查询结果,搜索用时 15 毫秒
101.
102.
We define and study the Hopf structures in the ternary (and n-ary) Nambu-Lie algebra. The fundamental concepts of 3-coalgebra, 3-bialgebra, and Hopf 3-algebra are introduced. Some examples of the Hopf structures and analyzed. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 114, No. 1, pp. 87–93, January, 1998.  相似文献   
103.
104.
In this paper we define the Kμ- transformation on certain spaces of generalized functions introduced by A.C. McBride by employing the kernel method. we also establish relations between the generalized Kμ- transformation and certain fractional integral operators.  相似文献   
105.
In the present paper, the adsorption of nucleic acid bases (A, adenine; C, cytosine; U, uracil; and T, thymine) on clays (bentonite, kaolinite, and montmorillonite) was studied at different pH (2.00 and 7.20). It should be pointed out there is no reported study of adsorption of nucleic acid bases on clays using seawater (with the major elements), and a wide range of pH. The main finding of this study was that the ratio of A and T adsorbed on clays ranged from 4.68 to 25.1, much higher than the ratio of their occurrence in organisms ranging from 0.95 to 1.05. The weaker adsorption of U and T on clays raises the question of the possibility of a genetic code based on purines only. The FT-IR spectra at pH 2.00 showed that the interaction of A, C, T, and U with the clays occurs through positively charged, protonated groups. Correspondence: Dr. Dimas A. M. Zaia, Departamento de Química-CCE, Universidade Estadual de Londrina, 86051-990 Londrina-PR, Brazil.  相似文献   
106.
A set of time series generated by stationary linear processes with an absolutely continuous spectral distribution is analysed. The time series can then be considered realizations of a linear process of random coefficients. Likewise, each spectral density function is a realization of a stochastic process whose function of means is called a population spectrum. We propose a kernel estimator for the population spectrum and give conditions for its consistency. We then illustrate the properties of this estimator in a simulation study and compare its performance with an alternative parametric estimator that can be found in the literature.   相似文献   
107.
Poly(ester amide)s with a regular sequence and derived from diamine, dicarboxylic acid, and glycolic acid units can be easily synthesized by using a thermal polycondensation method based on the formation of metal halide salts as a driving force. These new poly(ester amide)s have tuneable properties depending on the number of methylene groups and constitute a group of materials with potential interest as biodegradable materials in applications such as surgical sutures. The present work reveals that the proposed synthesis can also be applied when esters of L ‐lysine are used as a diamine unit since no secondary reactions such as transesterification occur under the required polymerization conditions. The possibility of linking compounds with pharmacological activity to the carboxylic acid groups of lysine extends the interest of the referred materials, for example, as drug delivery systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 661–667, 2008  相似文献   
108.
From the mantle of the Caribbean Sea gastropod molluskStrombus gigas a bioglycan containing carbohydrates (73%), protein (22%), and lipid (about 5%) components has been isolated. It has been shown by hydrolysis, periodate oxidation, and methylation that the bioglycan is a D-glucan constructed of -1,4-bound D-glucose residues and has side chains of D-glucose residues linked by -1,6-bonds.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 36–40, January–February, 1988.  相似文献   
109.
110.
We study the problem of finding conditions for two star products of n vectors to be equal when the vectors in each star product are not linearly independent, and the problem of finding conditions for one star product to be zero. We reprove results of M. Marcus and J. Chollet in a very simple way. We present also some open problems.  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