全文获取类型
收费全文 | 653398篇 |
免费 | 5290篇 |
国内免费 | 1806篇 |
专业分类
化学 | 337717篇 |
晶体学 | 9212篇 |
力学 | 31426篇 |
综合类 | 21篇 |
数学 | 85670篇 |
物理学 | 196448篇 |
出版年
2021年 | 5743篇 |
2020年 | 6336篇 |
2019年 | 7109篇 |
2018年 | 9570篇 |
2017年 | 9658篇 |
2016年 | 13432篇 |
2015年 | 7415篇 |
2014年 | 12239篇 |
2013年 | 28728篇 |
2012年 | 21974篇 |
2011年 | 26253篇 |
2010年 | 19476篇 |
2009年 | 19250篇 |
2008年 | 25043篇 |
2007年 | 24914篇 |
2006年 | 22876篇 |
2005年 | 20567篇 |
2004年 | 18868篇 |
2003年 | 17069篇 |
2002年 | 16944篇 |
2001年 | 17856篇 |
2000年 | 13991篇 |
1999年 | 10769篇 |
1998年 | 9332篇 |
1997年 | 9249篇 |
1996年 | 8660篇 |
1995年 | 7705篇 |
1994年 | 7708篇 |
1993年 | 7532篇 |
1992年 | 7996篇 |
1991年 | 8481篇 |
1990年 | 8127篇 |
1989年 | 8018篇 |
1988年 | 7846篇 |
1987年 | 7615篇 |
1986年 | 7340篇 |
1985年 | 9448篇 |
1984年 | 9879篇 |
1983年 | 8200篇 |
1982年 | 8682篇 |
1981年 | 8106篇 |
1980年 | 7706篇 |
1979年 | 8259篇 |
1978年 | 8680篇 |
1977年 | 8546篇 |
1976年 | 8493篇 |
1975年 | 8073篇 |
1974年 | 7958篇 |
1973年 | 8306篇 |
1972年 | 5959篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
An analytic solution of the problem concerning the frequencies and shapes of free axially symmetric oscillations of a truncated spherical sector filled with an ideal compressible fluid is constructed. A spherical wall of smaller radius and the radial wall of the sector are absolutely rigid. A thin elastic shell whose edge is clamped in the radial wall is located on a spherical boundary of larger radius. The outer surface of the shell borders vacuum. The phenomenon of an anomalous decrease in the fundamental frequency as the spherical walls approach each other is discovered. An approximate formula for determination of the lowest fundamental frequencies, which are approximately proportional to the square root of the difference of the radii of spherical walls for small values of this difference, is constructed and tested numerically. Bibliography: 13 titles. 相似文献
992.
E. V. Radkevich 《Journal of Mathematical Sciences》2004,123(5):4428-4455
The paper is devoted to the study of the asymptotic behavior of solutions to linearized systems of equations of the so-called nonequilibrium thermodynamic moments. 相似文献
993.
A. I. Madunts 《Journal of Mathematical Sciences》2004,120(4):1609-1612
Some isomorphism criteria for Lubin–Tate formal groups over the ring of integers of a multidimensional local field are given. Bibliography: 4 titles. 相似文献
994.
The nonprimary subgroups of the symmetric group S
9 are investigated. Embedding properties of these subgroups are listed in a table. Properties such as abnormality, pronormality, paranormality, weak normality, etc. were checked with the help of a computer. Algorithms and codes of the first author were used for this purpose. The research leans upon the technique of Burnside marks, as well as upon pertinent information on the table of marks of S
9 from the computer algebra package GAP. The subgroups were investigated up to conjugacy; the total number of conjugacy classes of nonprimary subgroups of S
9 is 432. Some subgroups were additionally checked by other programs based on the double coset method. Bibliography: 24 titles. 相似文献
995.
E. A. Sopkina 《Journal of Mathematical Sciences》2004,124(1):4832-4836
An invariant of a closed set that is equal to the sum of roots is introduced. For a closed subset in a root system, we describe symmetric and special parts and its stabilizer in the Weyl group by means of the sum of roots. We determine associated bases with respect to which the closed set has the simplest form. All possible values of the root sum are found. Bibliography: 9 titles. 相似文献
996.
David E. Anderson 《Proceedings of the American Mathematical Society》2004,132(9):2517-2527
With an explicit example, we confirm a conjecture by Neumann and Wahl that there exist cusps with no Galois cover by a complete intersection. Some computational techniques are reviewed, and a method for deciding whether a given cusp has a complete intersection Galois cover is developed.
997.
998.
Surzhikov A. P. Ghyngazov S. A. Lysenko E. N. Frangulyan T. S. 《Russian Physics Journal》2003,46(9):939-943
It is shown that activation of the process of oxygen diffusion in polycrystalline lithium-titanium ferrites heated by a beam of high-energy electrons in the range of temperatures 873–1173 K occurs due to two factors: gas medium ionization by an e-beam and acceleration of diffusion processes directly in the matrix in the irradiation field. 相似文献
999.
G. Kocher-Oberlehner W. Jantsch L. Palmetshofer A. Ulyashin 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):347
Erbium (Er)- and oxygen (O)-doped Cz–Si was additionally doped with hydrogen, using plasma enhanced chemical vapour deposition. Photoluminescence (PL) spectra show a large enhancement especially for samples treated with solid phase epitaxy before hydrogenation and annealing at 900°C later. Secondary ion mass spectroscopy measurements give evidence for an enhanced diffusion of O and Er at this temperature towards the surface. Etching shows that the PL does not stem from the heavily doped surface layer but from a deeper region with lower Er concentration. This conclusion is supported by the appearance of the so-called “cubic” centre with low solubility. Comparing the PL yield of the hydrogenated samples to that of samples with similar Er volume concentration but without hydrogenation still gives a large enhancement. We thus conclude that hydrogen can enhance the solubility of the cubic centre in Si:Er,O. 相似文献
1000.
We propose a normal form for nonlinear control systems with scalar output. We follow an approach proposed by Poincaré and adapted for control systems by Kang and Krener which consists of analyzing, step-by-step, the action of the change of coordinates on the system. To cite this article: I.A. Tall, M. Balde, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献