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   289篇
  免费   13篇
化学   190篇
晶体学   2篇
力学   4篇
数学   28篇
物理学   78篇
  2022年   4篇
  2021年   4篇
  2020年   4篇
  2019年   3篇
  2018年   3篇
  2017年   5篇
  2016年   12篇
  2015年   6篇
  2014年   8篇
  2013年   29篇
  2012年   14篇
  2011年   17篇
  2010年   14篇
  2009年   17篇
  2008年   18篇
  2007年   19篇
  2006年   15篇
  2005年   16篇
  2004年   7篇
  2003年   9篇
  2002年   6篇
  1999年   2篇
  1996年   3篇
  1995年   4篇
  1994年   3篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1987年   3篇
  1986年   1篇
  1985年   3篇
  1984年   4篇
  1983年   3篇
  1982年   3篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1969年   4篇
  1968年   2篇
  1967年   2篇
  1966年   1篇
  1958年   1篇
  1942年   1篇
排序方式: 共有302条查询结果,搜索用时 31 毫秒
1.
In this paper we prove a uniqueness theorem for meromorphic functions sharing three values with some weight which improves some known results.  相似文献   
2.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is energetically much more unstable than the neutron matter of identical physical condition.  相似文献   
3.
An exact formalism for the relativistic version of Landau theory of Fermi liquid in presence of strong quantizing magnetic field is developed. Both direct and exchange type interactions with scalar and vector coupling cases are considered.  相似文献   
4.
In earlier studies, the interactions of isolated ionic species with various solvents were investigated using ab initio calculations. The ionic species investigated included cations (proton, hydronium, ammonium, and metal cations) and anions (single electron, hydroxide, and halide anions). However in the present study, we investigate the interactions of these ionic species with the solvent in the presence of other competing ionic species. We also elaborate on how the information obtained from these extensive studies have been employed in designing and synthesizing various kinds of novel ionophores and receptors.  相似文献   
5.
Proton and alpha particle spectra have been measured in the 12C+93Nb and 12C+58Ni reactions at E(12C)=40 and 50 MeV and in the 16O + 93Nb reaction at E(16O) =75 MeV. The spectra are compared with the statistical model calculations. The shapes of the calculated spectra are in agreement with experimental data except for the alpha spectrum in the 12C + 93Nb reaction at 40 MeV. The observed evaporation bump is at ∼2 MeV lower energy compared to the calculated one. This discrepancy could imply alpha particle emission from a deformed configuration before compound nucleus formation at this near Coulomb barrier beam energy.  相似文献   
6.
Chain transfer constants of some fluoroalcohols [HCF2(CF2)n?1CH2OH, n = 2, 4, 6] in the catalyzed polymerization of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate at 60°C have been evaluated by a method based on degree of polymerization. Since fluoroalcohols are normally nonsolvents for polymers, a homogeneous reaction phase is maintained by carrying out the polymerization in benzene (except in case of acrylonitrile, where no solvent was used). The transfer constants vary, depending on the reactivity as well as the polarity of the radicals, in the following order: vinyl acetate > styrene > methyl methacrylate > acrylonitrile. Of the three fluoroalcohols studied, the transfer constants increase with the increasing value of n. The results have been interpreted in terms of polar structure contribution in the transition state of the transfer reactions.  相似文献   
7.
Decomposition of isopropanol on V2O5 and the bonzes Li0.02V2O5, Na0.02V2O5, Na0.06V2O5, Li0.33V2O5, and Na0.33V2O5 has been studied in the temperature range 168–300°C. The main reaction was found to be dehydration to propene with negligible dehydrogenation to acetone on the first four catalysts. Dehydration on these catalysts increased with the alkali metal content, but the energy of activation remained unchanged. On the last two catalysts, dehydration and dehydrogenation proceeded at comparable rates. A tentative mechanism for the dehydration of isopropanol is proposed, based on the effect of the product on the initial rate, the electric conductivity of the catalysts and their ESR spectra.
V2O5 : Li0,02V2O5, Na0,02V2O5, Na0,06V2O5, Li0,33V2O5 Na0,33V2O5 186–300°C. . , . . , , .
  相似文献   
8.
The effects of confinement of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate on solvation dynamics and rotational relaxation of Coumarin 153 (C-153) in Triton X-100/cyclohexane microemulsions have been explored using steady-state and picosecond time-resolved emission spectroscopy. The steady-state and rotational relaxation data indicate that C-153 molecules are incorporated in the core of the microemulsions. The average rotational relaxation time increases with increase in w ([bmim][BF(4)]/[TX-100]) values. The solvent relaxation in the core of the microemulsion occurs on two different time scales and is almost insensitive to the increase in w values. The solvent relaxation is retarded in the pool of the microemulsions compared to the neat solvent. Though, the retardation is very small compared to several-fold retardation of the solvation time of the conventional solvent inside the pool of the microemulsions.  相似文献   
9.
10.
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