全文获取类型
收费全文 | 21277篇 |
免费 | 2748篇 |
国内免费 | 2176篇 |
专业分类
化学 | 16181篇 |
晶体学 | 315篇 |
力学 | 1059篇 |
综合类 | 187篇 |
数学 | 1888篇 |
物理学 | 6571篇 |
出版年
2024年 | 39篇 |
2023年 | 289篇 |
2022年 | 580篇 |
2021年 | 649篇 |
2020年 | 693篇 |
2019年 | 691篇 |
2018年 | 545篇 |
2017年 | 550篇 |
2016年 | 932篇 |
2015年 | 899篇 |
2014年 | 1076篇 |
2013年 | 1500篇 |
2012年 | 1871篇 |
2011年 | 1919篇 |
2010年 | 1345篇 |
2009年 | 1164篇 |
2008年 | 1407篇 |
2007年 | 1199篇 |
2006年 | 1159篇 |
2005年 | 1124篇 |
2004年 | 881篇 |
2003年 | 770篇 |
2002年 | 842篇 |
2001年 | 545篇 |
2000年 | 480篇 |
1999年 | 443篇 |
1998年 | 315篇 |
1997年 | 288篇 |
1996年 | 284篇 |
1995年 | 269篇 |
1994年 | 215篇 |
1993年 | 196篇 |
1992年 | 177篇 |
1991年 | 152篇 |
1990年 | 134篇 |
1989年 | 112篇 |
1988年 | 97篇 |
1987年 | 63篇 |
1986年 | 66篇 |
1985年 | 70篇 |
1984年 | 38篇 |
1983年 | 31篇 |
1982年 | 24篇 |
1981年 | 23篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 3篇 |
1974年 | 7篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
Y. E. Kim M. Rabinowitz J. -H. Yoon 《International Journal of Theoretical Physics》1993,32(7):1197-1223
Previously overlooked condensed matter effects (CME) can significantly influence nuclear fusion rates in both laboratory and astrophysical environments. In dense plasmas, the ensemble of fusing particles has a significant exchange of kinetic and potential energies. Thus, there are diminished effective flux velocities resulting in a significant selective reduction of fusion rates. Our CME predictions are testable in laboratory experiments and have broad-ranging implications on the fusion rates for stellar media in general. By calculating reaction rates forp(p, e
+
v
e
) D and7Be(p, )8B in the sun, we show that CME help to solve the solar neutrino problem. 相似文献
34.
35.
The enantioselective synthesis of the potent, selective, cytotoxic, annonaceous acetogenin, (+)-gigantecin, has been completed. An asymmetric glycolate aldol serves to establish the stereocenters at C13,14 and at C21,22. A Carreira asymmetric acetylide addition is used to establish the C17 stereocenter. 相似文献
36.
[formula: see text] S-Nitrosoglutathione oxidized 4-substituted Hantzsch 1,4-dihydropyridines in CH3CN/H2O or CH3CN/phosphate aqueous buffer solution to give aromatic products in various yields. 相似文献
37.
We study rate processes in general Gaussian fluctuating environments using a path integral formalism. We derive a variational equation for the dominant survival path when the fluctuations relax exponentially or according to a stretched exponential law. In the case of a slowly varying barrier, the equilibrium regression approximation which is used by Frauenfelder and coworkers emerges. In this approximation, the survival path follows the ordinary law of relaxation to equilibrium. If the rate coefficients vary rapidly with environmental variables, however, the dominant survival paths exhibit more complex behaviour. Many phenomena analogous to geometrical optics occur. These include reflection off of rapid variations in rate constant, as well as refraction, giving paths very different from the equilibrium relaxation properties. A model with a piece-wise linear rate exhibits the basic phenomena, and the survival path equation is exactly solved for the general stretched exponential relaxing environment. 相似文献
38.
The reductive alkylation of amine with carbonyl compounds usingsodium hydrogen telluride has been investigated in recent years.Application of this method to the synthesis of N-alkyl derivativesof biologically important amino acids and their esters is described. 相似文献
39.
Jun-hua Shi Yuxun Zhou Ming-lei He Jian Jin Yi-chuan Xiao Jun-hua Xiao Dong-zhi Wei 《Chemistry of Natural Compounds》2006,42(3):325-327
A novel compound, biotinylated 18β-glycyrrhetinic acid (BGA), was synthesized. It is a compound of 18β-glycyrrhetinic acid linked with biotin.
Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 266–267, May–June, 2006.
An erratum to this article is available at . 相似文献
40.
An electroanalytical method, based on derivative chronopotentiometry of the copper complex with 4-[(4-diethylamino-2-hydroxyphenyl) azo]-5-hydroxy-naphthalene-2,7-disulphonic acid (Beryllon III) accumulated on the surface of a hanging mercury drop electrode, for determining trace copper in food has been developed. The dependence of the peak height of reduction of the copper complex on the preconcentration time and preconcentration potential are discussed. Optimum experimental conditions include 0.01 M HOAc, 0.01M NaOAc, 1.0 x 10(-6) Beryllon III and a preconcentration potential of 0.10 V (vs. SCE). Under these conditions the detection limit and the linear range are 4 x 10(-11)M and 6 x 10(-11) -4 x 10(-7)M, respectively. The method was applied to samples of digested rice. 相似文献