全文获取类型
收费全文 | 811642篇 |
免费 | 8079篇 |
国内免费 | 2426篇 |
专业分类
化学 | 415185篇 |
晶体学 | 12100篇 |
力学 | 40405篇 |
综合类 | 26篇 |
数学 | 108843篇 |
物理学 | 245588篇 |
出版年
2020年 | 7364篇 |
2019年 | 8323篇 |
2018年 | 10943篇 |
2017年 | 10965篇 |
2016年 | 15721篇 |
2015年 | 9056篇 |
2014年 | 14751篇 |
2013年 | 35874篇 |
2012年 | 27206篇 |
2011年 | 32965篇 |
2010年 | 23663篇 |
2009年 | 23565篇 |
2008年 | 30429篇 |
2007年 | 30448篇 |
2006年 | 28160篇 |
2005年 | 25196篇 |
2004年 | 23319篇 |
2003年 | 20959篇 |
2002年 | 20853篇 |
2001年 | 22181篇 |
2000年 | 17366篇 |
1999年 | 13617篇 |
1998年 | 11748篇 |
1997年 | 11592篇 |
1996年 | 11033篇 |
1995年 | 10000篇 |
1994年 | 10070篇 |
1993年 | 9707篇 |
1992年 | 10353篇 |
1991年 | 10767篇 |
1990年 | 10326篇 |
1989年 | 10055篇 |
1988年 | 10003篇 |
1987年 | 9778篇 |
1986年 | 9260篇 |
1985年 | 12274篇 |
1984年 | 12833篇 |
1983年 | 10726篇 |
1982年 | 11163篇 |
1981年 | 10761篇 |
1980年 | 10362篇 |
1979年 | 10802篇 |
1978年 | 11308篇 |
1977年 | 11105篇 |
1976年 | 11185篇 |
1975年 | 10500篇 |
1974年 | 10444篇 |
1973年 | 10752篇 |
1972年 | 7747篇 |
1971年 | 6626篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Grigor'ev S. A. Kalinnikov A. A. Porembskii V. I. Baranov I. E. Borisova E. V. Fateev V. N. 《Russian Journal of Electrochemistry》2004,40(11):1188-1192
A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally. 相似文献
992.
Kinetic parameters of amino acid cations in an MK-40 ion-exchange membrane are calculated from the conductivity data. A theoretical quantum-chemical analysis of experimental activation energies for conduction suggests a mechanism of elementary act of transport of amino acid cations in the membrane. 相似文献
993.
On General Mixed Quasivariational Inequalities 总被引:5,自引:0,他引:5
In this paper, we suggest and analyze several iterative methods for solving general mixed quasivariational inequalities by using the technique of updating the solution and the auxiliary principle. It is shown that the convergence of these methods requires either the pseudomonotonicity or the partially relaxed strong monotonicity of the operator. Proofs of convergence is very simple. Our new methods differ from the existing methods for solving various classes of variational inequalities and related optimization problems. Various special cases are also discussed. 相似文献
994.
Cyclic Hypomonotonicity,Cyclic Submonotonicity,and Integration 总被引:9,自引:1,他引:8
Rockafellar has shown that the subdifferentials of convex functions are always cyclically monotone operators. Moreover, maximal cyclically monotone operators are necessarily operators of this type, since one can construct explicitly a convex function, which turns out to be unique up to a constant, whose subdifferential gives back the operator. This result is a cornerstone in convex analysis and relates tightly convexity and monotonicity. In this paper, we establish analogous robust results that relate weak convexity notions to corresponding notions of weak monotonicity, provided one deals with locally Lipschitz functions and locally bounded operators. In particular, the subdifferentials of locally Lipschitz functions that are directionally hypomonotone [respectively, directionally submonotone] enjoy also an additional cyclic strengthening of this notion and in fact are maximal under this new property. Moreover, every maximal cyclically hypomonotone [respectively, maximal cyclically submonotone] operator is always the Clarke subdifferential of some directionally weakly convex [respectively, directionally approximately convex] locally Lipschitz function, unique up to a constant, which in finite dimentions is a lower C2 function [respectively, a lower C1 function]. 相似文献
995.
A. J. Zaslavski 《Journal of Optimization Theory and Applications》2004,123(3):695-712
In our previous work, a generic well-posedness result (with respect to variations of the integrand of the integral functional) without the convexity condition was established for a class of optimal control problems satisfying the Cesari growth condition. In this paper, we extend this generic well-posedness result to classes of constrained variational problems in which the values at the endpoints and constraint maps are also subject to variations. 相似文献
996.
G. Z. Ruan S. Y. Wang Y. Yamamoto S. S. Zhu 《Journal of Optimization Theory and Applications》2004,123(2):409-429
In this paper, a model of a linear multilevel programming problem with dominated objective functions (LMPPD(l)) is proposed, where multiple reactions of the lower levels do not lead to any uncertainty in the upper-level decision making. Under the assumption that the constrained set is nonempty and bounded, a necessary optimality condition is obtained. Two types of geometric properties of the solution sets are studied. It is demonstrated that the feasible set of LMPPD(l) is neither necessarily composed of faces of the constrained set nor necessarily connected. These properties are different from the existing theoretical results for linear multilevel programming problems. 相似文献
997.
For vector quasivariational inequalities involving multifunctions in topological vector spaces, an existence result is obtained without a monotonicity assumption and with a convergence assumption weaker than semicontinuity. A new type of quasivariational inequality is proposed. Applications to quasicomplementarity problems and traffic network equilibria are considered. In particular, definitions of weak and strong Wardrop equilibria are introduced for the case of multivalued cost functions. 相似文献
998.
Defining speed of diffusion as the amount of time it takes to get from one penetration level to a higher one, we introduce a dynamic model in which we study the link between pricing policy, speed of diffusion, and number of competitors in the market. Our analysis shows that, in the case of strategic (oligopolistic) competition, the speed of diffusion has an important influence on the optimal pricing policy. In particular, we find that higher speeds of diffusion create an incentive to strategically interacting firms to lower their prices. 相似文献
999.
A computer construction of the Monster is used to prove thatPSL(2, 59) is a subgroup of the Monster. 相似文献
1000.
We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center. 相似文献