全文获取类型
收费全文 | 271967篇 |
免费 | 13081篇 |
国内免费 | 9680篇 |
专业分类
化学 | 130159篇 |
晶体学 | 3592篇 |
力学 | 12885篇 |
综合类 | 589篇 |
数学 | 27445篇 |
物理学 | 80608篇 |
无线电 | 39450篇 |
出版年
2022年 | 3341篇 |
2021年 | 4607篇 |
2020年 | 4803篇 |
2019年 | 5302篇 |
2018年 | 6057篇 |
2017年 | 6203篇 |
2016年 | 7672篇 |
2015年 | 5579篇 |
2014年 | 8138篇 |
2013年 | 12770篇 |
2012年 | 12311篇 |
2011年 | 13547篇 |
2010年 | 10904篇 |
2009年 | 11327篇 |
2008年 | 12452篇 |
2007年 | 11937篇 |
2006年 | 10998篇 |
2005年 | 9567篇 |
2004年 | 8516篇 |
2003年 | 7557篇 |
2002年 | 7567篇 |
2001年 | 7586篇 |
2000年 | 6148篇 |
1999年 | 4976篇 |
1998年 | 4424篇 |
1997年 | 4036篇 |
1996年 | 3718篇 |
1995年 | 3365篇 |
1994年 | 3211篇 |
1993年 | 3029篇 |
1992年 | 2972篇 |
1991年 | 3150篇 |
1990年 | 3033篇 |
1989年 | 2958篇 |
1988年 | 2794篇 |
1987年 | 2654篇 |
1986年 | 2486篇 |
1985年 | 3001篇 |
1984年 | 2928篇 |
1983年 | 2517篇 |
1982年 | 2530篇 |
1981年 | 2411篇 |
1979年 | 2477篇 |
1978年 | 2606篇 |
1977年 | 2695篇 |
1976年 | 2782篇 |
1975年 | 2595篇 |
1974年 | 2516篇 |
1973年 | 2683篇 |
1972年 | 2189篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dabiri D. Blake I.F. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(4):873-885
The problem of decoding cyclic error correcting codes is one of solving a constrained polynomial congruence, often achieved using the Berlekamp-Massey or the extended Euclidean algorithm on a key equation involving the syndrome polynomial. A module-theoretic approach to the solution of polynomial congruences is developed here using the notion of exact sequences. This technique is applied to the Welch-Berlekamp (1986) key equation for decoding Reed-Solomon codes for which the computation of syndromes is not required. It leads directly to new and efficient parallel decoding algorithms that can be realized with a systolic array. The architectural issues for one of these parallel decoding algorithms are examined in some detail 相似文献
992.
993.
P. V. Rogovskii S. L. Panasyuk A. A. Evstratov S. I. Kol'tsov 《Theoretical and Experimental Chemistry》1993,28(3):220-223
ESR shows that V(IV) may occur in isolated or interacting vanadium-oxygen groups on the surfaces of catalytically active P-V and Ti-V-bearing silica gels; there is a relationship between the V(IV) content and the phthalic anhydride selectivity in the oxidation of o-xylene.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 3, pp. 277–282, May–June, 1992. 相似文献
994.
The complete symmetry algebras of the Veselov-Novikov equation and of the modified Kadomtsev-Petviashvili equation are constructed. Some related questions are discussed.P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 95, No. 1, pp. 34–41, April, 1993. 相似文献
995.
996.
H. M. Ortner H. H. Xu J. Dahmen K. Englert H. Opfermann W. Görtz 《Fresenius' Journal of Analytical Chemistry》1996,355(5-6):657-664
Surface characterization of new unused PTFE, PFA and PVDF labware has been carried out by light microscopy, scanning electron microscopy, profilometry and atomic force microscopy. It has been found that in spite of higher micro-roughness, PFA exhibits the lowest nano-roughness and hence seems best suited as vessel material for relatively mild pressureless chemical operations for sample preparation of ultrapure substances, as container material for storage of ultrapure liquids, and for transport of such liquids, e.g., from the producer in the chemical to the end user in the microelectronics industry. This suitability refers only to the surface quality of the investigated materials. PTFE-surfaces, due to the sintering process of production, exhibit the most unfavourable surface quality of the investigated fluorinated polymers. 相似文献
997.
998.
Th. Mühge Yu. V. Goryunov K. Theis-Bröhl K. Westerholt H. Zabel I. A. Garifullin 《Applied magnetic resonance》1998,14(4):567-582
Magnetic and superconducting properties of Fe/Nb epitaxial bilayers have been studied. Single crystal Fe/Nb (110) bilayers with a Nb thicknessd Nb in the range from 250 to 650 Å and with a Fe thicknessd Fe in the range from 7 to 27 Å were prepared using molecular beam epitaxy techniques. Magnetization measurements showed the existence of a magnetically “dead” Fe-interface layer with a thicknessd NM varying strongly with minor modifications of the growth conditions. For bilayers with a small magnetic layer thicknessd M and a smalld NM the FMR measurements revealed an anomalous decrease of the effective magnetization 4πM eff of the ferromagnetic Fe layer below the superconducting transition temperatureT c. The absolute change of 4πM eff belowT c depends strongly on the actual values ofd M andd NM: upon decreasing bothd M andd NM the effect increases considerably. As a possible mechanism for the anomalous temperature dependence of 4πM eff belowT c we discuss a spatial modulation of ferromagnetic order due to a modification of the RKKY inter-action in the superconducting state. 相似文献
999.
A. I. Golovashkin N. V. Anshukova L. I. Ivanova O. T. Maljuchkov A. P. Rusakov 《Czechoslovak Journal of Physics》1996,46(3):1191-1192
On the basis of new experimental studies of specific heat, magnetic properties and thermal expansion, it was shown that dielectric-metal phase transitions were the consequence of delocalization of the heavy holes located on metalapical oxygen bonds in the high-Tc oxide systems. The ordered arrays of such holes (CDW) results in the dielectric gaps in electron spectrum and anomalous negative thermal expansion. The free carriers introduced by doping can couple through excitations of these localized holes, (local bosons). The high-Tc superconductivity will possess anomalous Hc2(T) dependence and γ-type specific heat jump at Tc. This local bosons model is the basis for explanation of the obtained experimental data. 相似文献
1000.