全文获取类型
收费全文 | 1354篇 |
免费 | 50篇 |
国内免费 | 5篇 |
专业分类
化学 | 854篇 |
晶体学 | 6篇 |
力学 | 22篇 |
数学 | 273篇 |
物理学 | 254篇 |
出版年
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 19篇 |
2018年 | 12篇 |
2016年 | 28篇 |
2015年 | 25篇 |
2014年 | 38篇 |
2013年 | 61篇 |
2012年 | 64篇 |
2011年 | 57篇 |
2010年 | 56篇 |
2009年 | 39篇 |
2008年 | 69篇 |
2007年 | 50篇 |
2006年 | 57篇 |
2005年 | 40篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 33篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 21篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 32篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 26篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 16篇 |
1974年 | 22篇 |
1971年 | 9篇 |
1970年 | 17篇 |
1969年 | 12篇 |
排序方式: 共有1409条查询结果,搜索用时 15 毫秒
81.
82.
Bruno Albrecht Michael Allan Edwin Haselbach Louis Neuhaus Pierre-Alain Carrupt 《Helvetica chimica acta》1984,67(1):220-223
Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured. I = 8.20 eV and I = 8.65 eV were found, the dominant vibrational progression (? = 725 cm?1) indicating that in the course of 1(X)→1 +( X? ) flattening around the N-atom occurs. The Franck-Condon profile of this band, however, suggests that a skeletal mode of ? ≈ 1400 cm?1 (observed also in the iso-π-electronic systems vinyl-alcohol-cation and allyl radical) may also be excited. Comparison with the data for the isomer acetaldehyde-imine 2 and its cation s + shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from the neutrals to the cations. 相似文献
83.
Albrecht Lindner 《Nuclear Physics A》1976,268(2):369-380
We define real functions which form a complete, orthogonal and rotational invariant basis for all problems depending on four directions. Their usefulness is demonstrated for processes of the type . The special case of all four directions in one plane has many applications too, e.g. in two- and three-body problems. 相似文献
84.
Albrecht Pietsch 《Archiv der Mathematik》1969,20(1):65-71
Ohne Zusammenfassung 相似文献
85.
A friction force is derived from the two-body collisions of projectile nucleons with target nucleons in the overlap region of their densities. We treat the diffuse surfaces of the heavy ions as Fermi gases. A certain average of the resulting friction force turns put to be identical in structure with the phenomenological Tsang-Swiatecki linear force. In our approach, the strength coefficient of the latter force can be calculated from the free two-nucleon scattering cross section without adjustable parameters. We obtain a strength which agrees well with the value found by Siwek-Wilczyńska and Wilczyński from an empirical fit. 相似文献
86.
It is shown that s-wave induced reactions with polarized particles can be described much more conveniently in new coordinates. Even with higher partial waves, cross sections can be fitted with less parameters than in conventional expansions. 相似文献
87.
For the investigation of the barrier to rotation about the C(sp2)—C(aryl) bond in non-planar pivalophenones five derivatives were prepared and their 1H and 13C NMR spectra assigned. Methyl and bromine groups in the 3-position have opposite substituent effects on the chemical shifts of the 1H and 13C signals of Me2 and Me4. The ΔG values were determined from the coalescence temperatures of the signal splittings generated by the addition of optically active shift reagents. The accuracy of this method was estimated by using different signals of 3-bromo-2,4,6-trimethylpivalophenone and by computer simulation of the line shape. A buttressing effect of substituents in the aromatic ring was observed. A change of the twist angle by the substitution of methyl by bromine in the tert-butyl group was suggested in order to explain the changes in ΔG and the chemical shifts. 相似文献
88.
We show that the wave function of a coupled quantum system may factorize for certain coupling operators, resulting in wave functions and effective nonlinear Hamiltonians for the subsystems. Systems of coupled harmonic oscillators with discrete or continuous spectra are considered, where all degrees of freedom move in time-dependent coherent Glauber states.We present the general formalism and study two examples in detail. The problem of radiation damping results under drastic assumptions in exponentially damped harmonic motion, obeying a nonlinear Schrödinger equation. In the second example, a different type of coupling is studied which yields inverse power law damping. 相似文献
89.
Andreas Albrecht Savas Dimopoulos W. Fischler Edward W. Kolb Stuart Raby Paul J. Steinhardt 《Nuclear Physics B》1983,229(2):528-540
A new inflationary universe scenario is considered based upon phase transitions in supersymmetric unified models where the Higgs potential is of the Witten-O'Raifeartaigh type. 相似文献
90.