全文获取类型
收费全文 | 499320篇 |
免费 | 6176篇 |
国内免费 | 1338篇 |
专业分类
化学 | 260782篇 |
晶体学 | 6179篇 |
力学 | 22176篇 |
综合类 | 16篇 |
数学 | 59379篇 |
物理学 | 158302篇 |
出版年
2021年 | 4273篇 |
2020年 | 4883篇 |
2019年 | 5323篇 |
2018年 | 6983篇 |
2017年 | 7210篇 |
2016年 | 10495篇 |
2015年 | 6305篇 |
2014年 | 10117篇 |
2013年 | 23959篇 |
2012年 | 18131篇 |
2011年 | 21768篇 |
2010年 | 15639篇 |
2009年 | 15400篇 |
2008年 | 19587篇 |
2007年 | 19379篇 |
2006年 | 18003篇 |
2005年 | 15823篇 |
2004年 | 14551篇 |
2003年 | 12929篇 |
2002年 | 12743篇 |
2001年 | 14852篇 |
2000年 | 11279篇 |
1999年 | 8670篇 |
1998年 | 7200篇 |
1997年 | 6891篇 |
1996年 | 6258篇 |
1995年 | 5854篇 |
1994年 | 5750篇 |
1993年 | 5570篇 |
1992年 | 6367篇 |
1991年 | 6392篇 |
1990年 | 6169篇 |
1989年 | 6095篇 |
1988年 | 5884篇 |
1987年 | 6002篇 |
1986年 | 5624篇 |
1985年 | 7338篇 |
1984年 | 7367篇 |
1983年 | 6017篇 |
1982年 | 6230篇 |
1981年 | 6053篇 |
1980年 | 5732篇 |
1979年 | 6268篇 |
1978年 | 6357篇 |
1977年 | 6442篇 |
1976年 | 6265篇 |
1975年 | 5834篇 |
1974年 | 5681篇 |
1973年 | 5747篇 |
1972年 | 3989篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
991.
The adsorption of polar organic substances (methanol, pyridine, and acetonitrile) and water was studied from the vapor phase on microporous adsorbent prepared by the substitution of polyhydroxyaluminum ions for the sodium ions of natural montmorillonite clay. The differential isosteric heats of adsorption of these substances were calculated and analyzed in a wide range of fillings. 相似文献
992.
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
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.
M. A. Diniz-Ehrhardt M. A. Gomes-Ruggiero J. M. Martínez S. A. Santos 《Journal of Optimization Theory and Applications》2004,123(3):497-517
The spectral projected gradient method SPG is an algorithm for large-scale bound-constrained optimization introduced recently by Birgin, Martínez, and Raydan. It is based on the Raydan unconstrained generalization of the Barzilai-Borwein method for quadratics. The SPG algorithm turned out to be surprisingly effective for solving many large-scale minimization problems with box constraints. Therefore, it is natural to test its perfomance for solving the sub-problems that appear in nonlinear programming methods based on augmented Lagrangians. In this work, augmented Lagrangian methods which use SPG as the underlying convex-constraint solver are introduced (ALSPG) and the methods are tested in two sets of problems. First, a meaningful subset of large-scale nonlinearly constrained problems of the CUTE collection is solved and compared with the perfomance of LANCELOT. Second, a family of location problems in the minimax formulation is solved against the package FFSQP. 相似文献
995.
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
996.
In his curriculum vitae, John Hawkes lists his research interestsas geometric measure theory, probability (Lévy processes),and potential theory (probabilistic). In fact, he made significantcontributions to all three areas, and there are strong relationshipsbetween them. He used both geometric measure theory and potentialtheory as tools for his study of the trajectories of particularLévy processes, but in many cases he needed to developthe tool before it was ready to be used. We will summarise hisresearch later, but first we discuss what is known of his lifehistory. 相似文献
997.
In this paper we prove the equivalence of various algebraically or geometrically defined assembly maps used in formulating the main conjectures in K- and L-theory, and C*-theory.Partially supported by NSERC grant A4000 and NSF grant DMS 9104026. The authors also wish to thank the SFB für Geometrie und Analysis, Münster, and the Max Planck Institut für Mathematik, Bonn, for their hospitality and support.Received: 7 May 2001 相似文献
998.
999.
A note on a generalized Douglas space 总被引:1,自引:0,他引:1
Periodica Mathematica Hungarica - 相似文献
1000.