全文获取类型
收费全文 | 282447篇 |
免费 | 2529篇 |
国内免费 | 759篇 |
专业分类
化学 | 153552篇 |
晶体学 | 4123篇 |
力学 | 12121篇 |
综合类 | 10篇 |
数学 | 28134篇 |
物理学 | 87795篇 |
出版年
2020年 | 2194篇 |
2019年 | 2294篇 |
2018年 | 2960篇 |
2017年 | 2954篇 |
2016年 | 4701篇 |
2015年 | 2938篇 |
2014年 | 4495篇 |
2013年 | 11768篇 |
2012年 | 9159篇 |
2011年 | 11352篇 |
2010年 | 7943篇 |
2009年 | 7980篇 |
2008年 | 10671篇 |
2007年 | 10577篇 |
2006年 | 10096篇 |
2005年 | 9245篇 |
2004年 | 8253篇 |
2003年 | 7467篇 |
2002年 | 7341篇 |
2001年 | 9216篇 |
2000年 | 6840篇 |
1999年 | 5286篇 |
1998年 | 4103篇 |
1997年 | 4152篇 |
1996年 | 3808篇 |
1995年 | 3598篇 |
1994年 | 3554篇 |
1993年 | 3247篇 |
1992年 | 3941篇 |
1991年 | 4157篇 |
1990年 | 3831篇 |
1989年 | 3780篇 |
1988年 | 3699篇 |
1987年 | 3616篇 |
1986年 | 3387篇 |
1985年 | 4350篇 |
1984年 | 4461篇 |
1983年 | 3620篇 |
1982年 | 3766篇 |
1981年 | 3557篇 |
1980年 | 3475篇 |
1979年 | 3861篇 |
1978年 | 4092篇 |
1977年 | 3905篇 |
1976年 | 3900篇 |
1975年 | 3681篇 |
1974年 | 3750篇 |
1973年 | 3731篇 |
1972年 | 2486篇 |
1971年 | 2095篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
V. F. Babenko 《Ukrainian Mathematical Journal》1991,43(9):1064-1076
We compute Kolmogorov widths in the space L1 for classes of periodic functions representable in the form of a kernel convolution that does not increase the number of sign changes with values in a given transposition invariant set of functions, and solve the optimization problem for quadrature formulas in these classes.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 9, pp. 1135–1148, September, 1991. 相似文献
952.
R. Murugesan P. Sami T. Jeyabalan A. Shunmugasundaram 《Journal of Chemical Sciences》1995,107(1):1-10
Bonding and redox properties of mono- and dititanium substituted 12-heteropolytungsto-phosphates and their complexes with
bivalent Mn, Co, Ni and Cu are studied by UV-Vis, ESR and cyclicvoltammetric techniques. The heteropoly blue analogue [TiIIITiIVW10PO40]8− is unstable and its presence in solution is proved by optical and ESR spectroscopy. ESR results reveal that the odd electron
is trapped on the titanium atom at 77 K. The optical electronegativity of Ti(III) in this heteropoly blue is estimated to
be 2.4 from the intervalence charge transfer (IVCT) bands. X-ray powder diffraction results show that the complexes K5MII[Ti2W10PO40].xH2O(MII = Cu or Mn) are isomorphous with K7[Ti2W10PO40].6H2O. Electronic spectroscopy indicates very high symmetry around the bivalent metal ion M in the K5MII[Ti2W10PO40].xH2O complexes. This high symmetry is confirmed in K5Cu[Ti2W10PO40] by the observation of dynamic Jahn-Teller (JT) distortion at 300 K and static JT distortion at 77 K. 相似文献
953.
In [1, 2] we established and dicussed the algebra of observables for 2+1 gravity at both the classical and quantum level. Here our treatment broadens and extends previous results to any genusg with a systematic discussion of the centre of the algebra. The reduction of the number of independent observables to 6g-6(g>1) is treated in detail with a precise classification forg=1 andg=2. 相似文献
954.
N. M. Agababyan M. R. Atayan M. Charlet J. Czyżewski E. A. De Wolf K. Dziunikowska A. M. F. Endler Z. Sh. Garutchava H. R. Gulkanyan R. Sh. Hakobyan J. K. Karamyan D. Kisielewska W. Kittel S. S. Mehrabyan Z. V. Metreveli E. C. Oliveira K. Olkiewicz F. K. Rizatdinova E. K. Shabalina L. N. Smirnova M. D. Tabidze L. A. Tikhonova A. V. Tkabladze A. G. Tomaradze F. Verbeure S. A. Zotkin 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):405-414
The NA22 data onπ ? π ? correlations are analyzed in terms of a number of two- and three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e+e? andµp collisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball-like models, both when including and excluding hydrodynamical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolution than in nuclear collisions. 相似文献
955.
R. Buccellato M. M. Michaelis C. A. Dempers A. Prause P. F. Cunningham 《Optics & Laser Technology》1993,25(4)
The concept of a pulsed gas lens is proposed. Potential applications are envisaged and preliminary experiments with pulsed ray refraction are reported. 相似文献
956.
957.
D. Kaptás T. Kemény J. Balogh L. F. Kiss L. Gránásy I. Vincze 《Hyperfine Interactions》1994,94(1):1861-1865
The temperature dependence of the iron hyperfine field distribution is reported in melt-quenched amorphous Fe-Zr alloys. The most remarkable feature is the compositinal change in the shape of the average hyperfine field versus temperature curves. The unusual increase in the average hyperfine field below about 85 K is a characteristic feature of the RSG systems; however, no anomaly is observed in the width of the hyperfine field distribution as a function of temperature. The results cannot be properly explained in the framework of the existing spin glass models. 相似文献
958.
An investigation was made of the resonance conditions in systems of one-dimensional potential barriers of a general kind. The types of systems are identified and the conditions determined which are necessary for observing a broad resonance in which the first three derivatives of the energy transmission coefficient are equal to zero. The conditions are found for observing an isolated resonance with complete transparency on a background of resonances with incomplete transparency.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 49–53, August, 1993. 相似文献
959.
J. Walz S. B. Ross C. Zimmermann L. Ricci M. Prevedelli T. W. Hänsch 《Hyperfine Interactions》1996,100(1):133-144
Experiments with electrons and ions in a combined trap are reported. The unique capability to confine particles with opposite charge and very different mass simultaneously in the same spatial region makes the combined trap a promising device for future synthesis of antihydrogen. 相似文献
960.
The famous 1960's construction of Golod and Shafarevich yields infinite dimensional nil, but not nilpotent, algebras. However, these algebras have exponential growth. Here, we construct an infinite dimensional nil, but not locally nilpotent, algebra which has polynomially bounded growth.