全文获取类型
收费全文 | 135751篇 |
免费 | 1874篇 |
国内免费 | 537篇 |
专业分类
化学 | 60302篇 |
晶体学 | 1126篇 |
力学 | 7599篇 |
综合类 | 5篇 |
数学 | 41824篇 |
物理学 | 27306篇 |
出版年
2023年 | 394篇 |
2022年 | 604篇 |
2021年 | 829篇 |
2020年 | 885篇 |
2019年 | 914篇 |
2018年 | 11128篇 |
2017年 | 10904篇 |
2016年 | 7848篇 |
2015年 | 2475篇 |
2014年 | 2012篇 |
2013年 | 4054篇 |
2012年 | 7221篇 |
2011年 | 13662篇 |
2010年 | 7800篇 |
2009年 | 7915篇 |
2008年 | 9516篇 |
2007年 | 11411篇 |
2006年 | 2938篇 |
2005年 | 3875篇 |
2004年 | 3703篇 |
2003年 | 3811篇 |
2002年 | 2624篇 |
2001年 | 1520篇 |
2000年 | 1502篇 |
1999年 | 1038篇 |
1998年 | 881篇 |
1997年 | 782篇 |
1996年 | 997篇 |
1995年 | 691篇 |
1994年 | 731篇 |
1993年 | 702篇 |
1992年 | 671篇 |
1991年 | 586篇 |
1990年 | 614篇 |
1989年 | 521篇 |
1988年 | 512篇 |
1987年 | 495篇 |
1986年 | 469篇 |
1985年 | 593篇 |
1984年 | 567篇 |
1983年 | 441篇 |
1982年 | 448篇 |
1981年 | 452篇 |
1980年 | 410篇 |
1979年 | 378篇 |
1978年 | 348篇 |
1977年 | 332篇 |
1976年 | 340篇 |
1974年 | 296篇 |
1973年 | 329篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
S. B. Beri K. B. Bhalla R. Bhanja A. Bharti V. S. Bhatia G. Claesson S. Garpman S. K. Gupta V. K. Gupta N. Y. Herrstrom B. Jakobsson R. Joseph G. L. Kaul G. Kaur M. Kaur S. Kitroo V. Kumar S. Lokanathan I. Lund L. K. Mangotra I. S. Mitra S. Mookerjee B. Norén A. Oskarsson I. Otterlund Y. Prakash S. Persson N. K. Rao S. Sankhyadhar S. Satti M. M. Sherif K. Söderström S. K. Tuli 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(4):431-441
40Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level. 相似文献
994.
In very dilute water solutions, ca 10−7 M, pyrene-3-carboxaldehyde fluoresces with a high quantum yield, øF = 0.98. This emission is quenched at low pH and, if the proton activity is high enough, a new weak, red shifted fluorescence appears. These effects are explained by the existence of a fast proton transfer in the excited state. The emitting singlet is believed to be 6–7 orders of magnitude more basic than the ground electronic state. By measuring the changes in fluorescence intensity and lifetime of pyrene-3-carboxaldehyde as a function of pH, a value for the quenching rate constant k2 = (2.2 ± 0.3) × 1010 M−1 s−1 was obtained. The quenching of the neutral form fluorescence is proposed to be produced by the protonation of the excited aldehyde, followed by a fast radiationless deactivation of the conjugated acid, before prototropic equilibrium can be attained. 相似文献
995.
J. Blčák 《Czechoslovak Journal of Physics》1979,29(9):945-980
A complete account of the Hamiltonian approach to the coupled perturbations of the Reissner-Nordström black hole, initiated by Moncrief, is given. All Hamiltonian equations are expressed explicitly in suitable forms; the metric and electromagnetic field perturbations are found in terms of Moncrief's gauge invariant canonical variables in the Regge-Wheeler gauge. The basic (both tetrad and coordinate) gauge invariant scalars occurring in the perturbation studies based on the Newman-Penrose formalism are then related to Moncrief's variables. The strikingly simple relations obtained enable us to show that the fundamental pair of decoupled equations, derived recently within the Newman-Penrose formalism by Chandrasekhar, can be cast into gauge invariant form, and that it can be obtained from Moncrief's formalism.It is demonstrated how the fundamental equations, supplemented by another combination of the Newman — Penrose equations, generalize the Bardeen-Press equations for uncoupled electromagnetic and gravitational perturbations of the Schwarzschild black hole.The odd and the even parityl=1 perturbations are also considered in detail. In the Appendix the relations to Zerilli's work on coupled perturbations of the Reissner-Nordström black hole are given. 相似文献
996.
J. Říkovská A. Machová W. D. Hamilton J. Dupák Chan Chen Mo M. Finger N. A. Lebedev B. S. Neganov V. N. Pavlov A. F. Shchus 《Czechoslovak Journal of Physics》1979,29(6):620-639
The anisotropy of the angular distribution of gamma-rays from the decay of156Tb, oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ156¦=(9·6±1·3)×10?27 J/T and the electric quadrupole momentQ 156=(2·9±0·9)×10?28 m2 of the156Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in156Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models. 相似文献
997.
P. A. Maksimyuk S. E. Litvin V. Navrátil M. Hamerský 《Czechoslovak Journal of Physics》1979,29(8):924-927
Internal friction measurements were used for the examination of Cd + Zn alloy single crystals. It was established that the interaction energy between solute Zn atoms and dislocations in basal planes is 0·12 eV.The authors thank Dr. P.Luká, CSc., for valuable discussions. 相似文献
998.
999.
In this work the deexcitation of the B3Π+(Ou+), v′ = 14 level of I2 after pulsed laser excitation has been studied. The quenching cross sections by collisions with I2, H2, CO, and CH4 have been measured. The experimental results are 190 ± 14, 2.5 ± 0.3, 15.1 ± 0.4, and 18.0 ± 0.6 Å2, respectively. These values are compatible (within 30%) with the semiempirical scaling law of proportionality with the product of polarizability and the square root of reduced mass. 相似文献
1000.
Armando Fernández Guillermet Per Gustafson Mats Hillert 《Journal of Physics and Chemistry of Solids》1985,46(12):1427-1429
It is sometimes advantageous to have an expression for the Gibbs energy, Gm(T,P), from which one can analytically derive an expression for the Heimholtz energy, Fm(T, Vm). Such an expression is suggested for solid substances and it is shown how expressions for other physical properties can be derived from it. 相似文献