全文获取类型
收费全文 | 1330766篇 |
免费 | 25761篇 |
国内免费 | 7685篇 |
专业分类
化学 | 662476篇 |
晶体学 | 20197篇 |
力学 | 74315篇 |
综合类 | 101篇 |
数学 | 240380篇 |
物理学 | 366743篇 |
出版年
2021年 | 13506篇 |
2020年 | 15908篇 |
2019年 | 16037篇 |
2016年 | 27521篇 |
2015年 | 20651篇 |
2014年 | 30356篇 |
2013年 | 74257篇 |
2012年 | 37315篇 |
2011年 | 33503篇 |
2010年 | 36361篇 |
2009年 | 38805篇 |
2008年 | 33134篇 |
2007年 | 28493篇 |
2006年 | 35612篇 |
2005年 | 27356篇 |
2004年 | 29028篇 |
2003年 | 27686篇 |
2002年 | 28921篇 |
2001年 | 28038篇 |
2000年 | 24533篇 |
1999年 | 22420篇 |
1998年 | 20943篇 |
1997年 | 21002篇 |
1996年 | 21078篇 |
1995年 | 19178篇 |
1994年 | 18613篇 |
1993年 | 18162篇 |
1992年 | 18062篇 |
1991年 | 18379篇 |
1990年 | 17592篇 |
1989年 | 17680篇 |
1988年 | 17210篇 |
1987年 | 17168篇 |
1986年 | 16112篇 |
1985年 | 22520篇 |
1984年 | 23780篇 |
1983年 | 19967篇 |
1982年 | 21657篇 |
1981年 | 20882篇 |
1980年 | 20238篇 |
1979年 | 20417篇 |
1978年 | 21704篇 |
1977年 | 21319篇 |
1976年 | 21097篇 |
1975年 | 19747篇 |
1974年 | 19480篇 |
1973年 | 19951篇 |
1972年 | 14405篇 |
1968年 | 12245篇 |
1967年 | 12581篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
861.
I. P. Kayumov 《Mathematical Notes》2005,78(3-4):498-502
In this paper, we prove Brennan's conjecture for conformal mappings f of the disk {z : | z| < 1} assuming that the Taylor coefficients of the function log(zf′(z)/f(z)) at zero are nonnegative. We also obtain inequalities for the integral means over the circle |z| = r of the squared modulus of the function zf′(z)/f(z). 相似文献
862.
863.
Mrio J. Edmundo 《Mathematical Logic Quarterly》2005,51(6):639-641
We show that if G is a definably compact, definably connected definable group defined in an arbitrary o‐minimal structure, then G is divisible. Furthermore, if G is defined in an o‐minimal expansion of a field, k ∈ ? and pk : G → G is the definable map given by pk (x ) = xk for all x ∈ G , then we have |(pk )–1(x )| ≥ kr for all x ∈ G , where r > 0 is the maximal dimension of abelian definable subgroups of G . (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
864.
Azepane rings have been constructed diastereoselectively upon a carbohydrate derivative utilising reductive amination and RCM. The stereochemistry of the ring junctions was confirmed by X-ray crystallography and NMR. Diastereoselective dihydroxylation has also been employed to afford a tetrahydroxylated azepane carbohydrate derivative with potential biological activity. 相似文献
865.
G. C. Psarras 《Journal of Polymer Science.Polymer Physics》2007,45(18):2535-2545
The charge transport properties of polymer matrix–carbon black composites are investigated in this study. Direct current conductivity is examined with varying parameters: the temperature and the conductive filler content. Conductivity data are analyzed by means of percolation theory, and both percolation threshold and critical exponent are determined at each of the examined temperatures. The temperature dependence of conductivity and the agreement of experimental results with the variable range hopping model reveal hopping conduction as the predominant transport mechanism, below and in the vicinity of the critical concentration of carbon black particles. At higher concentrations, the contribution of hopping transport to the overall conductivity is reduced and a balance between hopping and conduction via geometrical contact occurs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2535–2545, 2007 相似文献
866.
Alison L. Parry 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3178-3190
The ring‐opening metathesis polymerizations (ROMP), using RuCl2 (PCy3)2CHPh, of a series of peptide‐functionalized norbornene derivatives have been investigated. Incorporation of a PEG‐monomer was found to prevent premature precipitation of polymer strands during the course of polymerization reactions and yield water compatible polymers in high conversions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3178–3190, 2007 相似文献
867.
The occurrence of two noninteracting forms of Pd-porphin in the ground electronic state in a wide number of Shpolskii matrices maintained at liquid helium temperature was observed with the help of the finestructure phosphorescence spectra of these systems. The ratio between these forms can be varied in wide limits by choosing a particular matrix, which indicates that the matrix plays a significant role in the conformation formation of the tetrapyrrole macrocycle. Based on comparison both with the resonance Raman spectra and with the results of investigations of metal complexes of porphin by the selective spectroscopy methods, the shortwavelength spectral form has been shown to correspond to the planar molecular structure, whereas the longwavelength form has been attributed to a nonplanar molecular structure with the distortion of the porphin macrocycle of the saddle type. The results obtained indicate that the methods of fine structure spectroscopy make it possible to efficiently study distorted molecular structures stabilized in solid matrices at low temperatures. 相似文献
868.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献
869.
Dedushenko S. K. Makhina I. B. Mar'in A. A. Mukhanov V. A. Perfiliev Yu. D. 《Hyperfine Interactions》2004,158(1-4):417-421
A colourless quartz crystal doped with 57Fe3+ was obtained by hydrothermal synthesis in an NH4F solution. The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by changes in the Mössbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state: Fe3+→Fe4+.
相似文献870.
R. Hefelmann P. Mann A. Aignan F. Filsinger und H. Amsel 《Fresenius' Journal of Analytical Chemistry》1902,41(1):66-68
Ohne Zusammenfassung 相似文献