全文获取类型
收费全文 | 298031篇 |
免费 | 1345篇 |
国内免费 | 326篇 |
专业分类
化学 | 136822篇 |
晶体学 | 4651篇 |
力学 | 16869篇 |
综合类 | 3篇 |
数学 | 41998篇 |
物理学 | 99359篇 |
出版年
2021年 | 3095篇 |
2020年 | 3413篇 |
2019年 | 4189篇 |
2018年 | 6225篇 |
2017年 | 6438篇 |
2016年 | 7937篇 |
2015年 | 3516篇 |
2014年 | 6871篇 |
2013年 | 12103篇 |
2012年 | 10107篇 |
2011年 | 11772篇 |
2010年 | 9970篇 |
2009年 | 10125篇 |
2008年 | 11394篇 |
2007年 | 11187篇 |
2006年 | 9960篇 |
2005年 | 8593篇 |
2004年 | 8348篇 |
2003年 | 7759篇 |
2002年 | 8046篇 |
2001年 | 7662篇 |
2000年 | 6055篇 |
1999年 | 4486篇 |
1998年 | 4263篇 |
1997年 | 4122篇 |
1996年 | 3733篇 |
1995年 | 3296篇 |
1994年 | 3358篇 |
1993年 | 3374篇 |
1992年 | 3379篇 |
1991年 | 3786篇 |
1990年 | 3787篇 |
1989年 | 3794篇 |
1988年 | 3545篇 |
1987年 | 3628篇 |
1986年 | 3320篇 |
1985年 | 3850篇 |
1984年 | 4083篇 |
1983年 | 3488篇 |
1982年 | 3686篇 |
1981年 | 3372篇 |
1980年 | 3132篇 |
1979年 | 3621篇 |
1978年 | 3687篇 |
1977年 | 3855篇 |
1976年 | 3929篇 |
1975年 | 3672篇 |
1974年 | 3527篇 |
1973年 | 3688篇 |
1972年 | 3177篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Chemical kinetics of benzonitrile nitration with mixed acid is investigated in the temperature range 283–299 K. Pseudo-first-order rate constants are evaluated by means of rate experiments on homogeneous reacting mixtures having large stoichiometric excesses of nitric acid. The second-order kinetic constants for nitronium ion attack to the aromatic substrate are derived on the basis of the assessed nitration mechanism. An activation energy of 604 ± 37 kJ mol?1 is calculated for this reaction step. © 1993 John Wiley & Sons, Inc. 相似文献
82.
83.
V. Yu. Novokshenov 《Theoretical and Mathematical Physics》1992,93(2):1279-1291
Potentials of the Schrödinger equation, slowly decreasing at infinity, generate an infinite discrete spectrum converging to zero. The inverse scattering problem in the class of such potentials is solved in a constructive way similarly to the classical soliton theory. An infinite-dimensional system arising from Backlund transformations over soliton solutions plays the role of a determinant representation of the potential. The asymptotics at infinity is derived by use of the Poisson summation formula. An application to the long-time asymptotics of the solution of the Korteweg-de Vries equation is considered.In Memory of Prof. M. C. PolivanovInstitute of Mathematics, Urals Branch, Russian Academy of Sciences, 450000, Chernyshevsky str. 112, Ufa, Russia. Published in Teoreticheskaya i Matematicheskaya Fizika, Vol. 93, No. 2, pp. 286–301, November, 1992. 相似文献
84.
85.
V. B. Kuznetsov 《Theoretical and Mathematical Physics》1992,91(1):385-404
Integrable systems associated with separation of the variables in real Riemannian spaces of constant curvature are considered. An isomorphism between all such systems and the hyperbolic Gaudin magnet is established. This isomorphism is used in a classification of all coordinate systems that admit separation of the variables, the basis of which is the classification of the correspondingL operators of the Gaudin magnet.Leningrad State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 91, No. 1, pp. 83–111, April, 1992. 相似文献
86.
Cheriyan and Hagerup developed a randomized algorithm to compute the maximum flow in a graph with n nodes and m edges in O(mn + n2 log2n) expected time. The randomization is used to efficiently play a certain combinatorial game that arises during the computation. We give a version of their algorithm where a general version of their game arises. Then we give a strategy for the game that yields a deterministic algorithm for computing the maximum flow in a directed graph with n nodes and m edges that runs in time O(mn(logm/n log nn)). Our algorithm gives an O(mn) deterministic algorithm for all m/n = Ω(nε) for any positive constant ε, and is currently the fastest deterministic algorithm for computing maximum flow as long as m/n = ω(log n). 相似文献
87.
G. V. Plyatsko V. N. Maksimovich L. V. Khomlyak 《Journal of Mathematical Sciences》1992,62(1):2518-2523
We solve the thermoplastic problem for a semi-infinite plate under local nonstationary heating by heat sources. The physical equations are taken to be the relations of the nonisothermic theory of plastic flow associated with the Mises fluidity condition. The solution of the problem is constructed by the method of integral equations and the self-correcting method of sequential loading, where time is taken as the loading parameter. We carry out numerical computations of the stresses in the case of heating a plate with heat output by normal-circular heat sources. We study the problem of optimization of heating regimes in order to introduce favorable residual compressive stresses (from the point of view of hardness) in a given region of a half-plane. Two figures.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 27, 1988, pp. 29–34. 相似文献
88.
James V. Crivello 《Journal of polymer science. Part A, Polymer chemistry》2007,45(18):4331-4340
The irradiation of hybrid photopolymer systems consisting of a free radically polymerizable multifunctional acrylate monomer and a cationically polymerizable epoxide or oxetane monomer was conducted under conditions where only the free radical polymerization takes place. This results in the formation of a free‐standing polyacrylate network film containing quiescent oxonium ions along with the unreacted cyclic ether monomer. The subsequent application of a point source of heat to the film ignites a cationic ring‐opening frontal polymerization that emanates from that site and propagates to all portions of the irradiated sample. This article examines the impact of various molecular structural and experimental parameters on these novel hybrid frontal polymerizations that produce interpenetrating network polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4331–4340, 2007 相似文献
89.
90.