全文获取类型
收费全文 | 234519篇 |
免费 | 4625篇 |
国内免费 | 2888篇 |
专业分类
化学 | 122514篇 |
晶体学 | 3905篇 |
力学 | 12433篇 |
综合类 | 171篇 |
数学 | 24981篇 |
物理学 | 78028篇 |
出版年
2022年 | 2116篇 |
2021年 | 2758篇 |
2020年 | 2829篇 |
2019年 | 3302篇 |
2018年 | 4403篇 |
2017年 | 4328篇 |
2016年 | 5865篇 |
2015年 | 3334篇 |
2014年 | 5583篇 |
2013年 | 10412篇 |
2012年 | 9189篇 |
2011年 | 10634篇 |
2010年 | 8259篇 |
2009年 | 8383篇 |
2008年 | 9594篇 |
2007年 | 9390篇 |
2006年 | 8534篇 |
2005年 | 7417篇 |
2004年 | 6874篇 |
2003年 | 6174篇 |
2002年 | 6140篇 |
2001年 | 6847篇 |
2000年 | 5063篇 |
1999年 | 4025篇 |
1998年 | 3297篇 |
1997年 | 3357篇 |
1996年 | 3112篇 |
1995年 | 2697篇 |
1994年 | 2784篇 |
1993年 | 2571篇 |
1992年 | 2867篇 |
1991年 | 2932篇 |
1990年 | 2814篇 |
1989年 | 2838篇 |
1988年 | 2727篇 |
1987年 | 2694篇 |
1986年 | 2533篇 |
1985年 | 3149篇 |
1984年 | 3185篇 |
1983年 | 2659篇 |
1982年 | 2600篇 |
1981年 | 2573篇 |
1980年 | 2359篇 |
1979年 | 2726篇 |
1978年 | 2687篇 |
1977年 | 2888篇 |
1976年 | 2899篇 |
1975年 | 2689篇 |
1974年 | 2620篇 |
1973年 | 2727篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
42.
Three new cytotoxic polyacetylenes, PQ-1 (1), PQ-2 (2) and PQ-3 (3), have been isolated from Panax quinquefolium. The structures of these acetylenes were determined by analyses of their 1H-1H and 1H-13C COSY spectra. All these compounds exhibited strong cytotoxic activities against leukemia cells (L 1210) in tissue culture. 相似文献
43.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
44.
A. N. Troflmchuk 《Journal of Mathematical Sciences》1991,57(5):3407-3409
We develop a method of computing the nonsteady-state and free oscillations of a framed elastic structure situated on an elastic base and containing an ideal compressible fluid. The solution uses the method of integral transforms in conjunction with the method of orthogonal polynomials. In the transform space the problem reduces to systems of linear algebraic equations. The Fourier transform is applied to return to the original space. Examples of the computation are given.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 69–72. 相似文献
45.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989. 相似文献
46.
N. N. Manuylov 《Journal of Mathematical Sciences》2006,133(6):1686-1692
Renormalization formulas connecting the points of the orbits O
0
±
, i.e., the sequences generated by an irrational shift on the half-open interval [0, 1) or (0, 1], and the points of the orbits'
derivatives dmO
0
±
, i.e., the sequences obtained by restricting O
0
±
to half-open intervals of smaller length, are obtained. Bibliography: 5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 314, 2004, pp. 142–154. 相似文献
47.
S. N. Solov’ev K. A. Minasyan A. A. Korunov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):663-664
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol. 相似文献
48.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems. 相似文献
49.
50.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献