全文获取类型
收费全文 | 435509篇 |
免费 | 5535篇 |
国内免费 | 1229篇 |
专业分类
化学 | 233669篇 |
晶体学 | 6491篇 |
力学 | 18797篇 |
综合类 | 13篇 |
数学 | 49981篇 |
物理学 | 133322篇 |
出版年
2021年 | 3752篇 |
2020年 | 4186篇 |
2019年 | 4520篇 |
2018年 | 5855篇 |
2017年 | 5748篇 |
2016年 | 8842篇 |
2015年 | 5568篇 |
2014年 | 8549篇 |
2013年 | 20208篇 |
2012年 | 15658篇 |
2011年 | 19281篇 |
2010年 | 13515篇 |
2009年 | 13364篇 |
2008年 | 17674篇 |
2007年 | 17570篇 |
2006年 | 16282篇 |
2005年 | 14572篇 |
2004年 | 13551篇 |
2003年 | 11922篇 |
2002年 | 11757篇 |
2001年 | 13438篇 |
2000年 | 10105篇 |
1999年 | 7925篇 |
1998年 | 6578篇 |
1997年 | 6325篇 |
1996年 | 6090篇 |
1995年 | 5481篇 |
1994年 | 5401篇 |
1993年 | 5211篇 |
1992年 | 5842篇 |
1991年 | 5936篇 |
1990年 | 5678篇 |
1989年 | 5476篇 |
1988年 | 5499篇 |
1987年 | 5380篇 |
1986年 | 5097篇 |
1985年 | 6573篇 |
1984年 | 6713篇 |
1983年 | 5309篇 |
1982年 | 5399篇 |
1981年 | 5384篇 |
1980年 | 4974篇 |
1979年 | 5362篇 |
1978年 | 5502篇 |
1977年 | 5390篇 |
1976年 | 5334篇 |
1975年 | 4920篇 |
1974年 | 4895篇 |
1973年 | 4888篇 |
1972年 | 3459篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
S. Moss de Oliveira P. M. C. de Oliveira F. C. de Sá Barreto 《Journal of statistical physics》1995,78(5-6):1619-1627
Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint. 相似文献
963.
The literature data on the catalytic synthesis and transformations of furan compounds are correlated. The compositions of the most frequently used catalysts are presented, and the prospects for the more extensive incorporation of metal-complex and interphase catalysis in processes involving the transformation of furan compounds are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1174–1187, September, 1993. 相似文献
964.
This paper considers a problem of nonlinear programming in which the objective function is the ratio of two linear functions and the constraints define a bounded and connected feasible region. Using a coordinate transformation, this problem is transformed into a simpler one, whose geometric interpretation is of particular significance. The transformation leads to a characterization of some special vertices of the feasible region from both the theoretical and operational points of view. 相似文献
965.
DAndrea A. Tomassini N. Ferrari L. Righini M. Selci S. Bruni M. R. Simeoni G. 《Il Nuovo Cimento D》1995,17(11):1423-1427
Il Nuovo Cimento D - Normalized reflection spectra in GaInAs/GaAs quantum wells are shown for two sets of samples with different alloy concentration (x=9% and 18.5%) and well thickness ranging from... 相似文献
966.
967.
Using the cyclic voltammetry (CV), the electron-transfer kinetics for the reductions of NO+ and NO2+ cations have been studied at the Pt electrode in nitromethane, sulfolane, and propylene carbonate. The heterogeneous rate constants have been determined by two independent procedures from the transfer coefficient α, the diffusion coefficient D, from a detailed examination of the CV-peak separations, and from an inspection of the values of the cathodic peak potentials at different scan rates. The results have been compared to those reported in the literature, and discussed. In the classical model, outer-sphere electron-transfer reactions are considered subject to an activation energy arising from solvent reorganization and bond reorganization processes. The solvent and molecular reorganizational barriers for these electroreductions have been assessed in aprotic media. The Marcus-Hush theory has been applied to the self-exchange reactions of the NO2+/NO2 and NO+/NO couples in an attempt to predict the rate of electron transfer. The findings indicate some improvement between theory and experiment. However, it should be noted that the experimental values of ks found for the NO2+ reduction in the solvents used are still too high in comparison with those determined theoretically. In view of the fairly strong coordination of the solvent molecule(s) as ligand(s) to NO2+ and NO+ cations, we believe that such discrepancies should stem, to some extent, from the involvement of an inner-sphere pathway by generation of an activated complex on the surface of the Pt electrode. © 1993 John Wiley & Sons, Inc. 相似文献
968.
969.
970.
The contributions to the coefficient functions of the quark and the mixed quark-gluon condensate to mesonic correlators are calculated for the first time to all orders in the quark masses, and to lowest order in the strong coupling constant. Existing results on the coefficient functions of the unit operator and the gluon condensate are reviewed. The proper factorization of short- and long-distance contributions in the operator product expansion is discussed in detail. It is found that to accomplish this task rigorously the operator product expansion has to be performed in terms ofnon-normal-ordered condensates. The resulting coefficient functions are improved with the help of the renormalization group. The scale invariant combination of dimension 5 operators, including mixing with the mass operator, which is needed for the renormalization group improvement, is calculated in the leading order.Supported by the German Bundesministerium für Forschung und Technologie, under the contract 06 TM 761 相似文献