全文获取类型
收费全文 | 15673篇 |
免费 | 1040篇 |
国内免费 | 538篇 |
专业分类
化学 | 1454篇 |
晶体学 | 28篇 |
力学 | 1599篇 |
综合类 | 192篇 |
数学 | 12086篇 |
物理学 | 1892篇 |
出版年
2024年 | 23篇 |
2023年 | 153篇 |
2022年 | 360篇 |
2021年 | 383篇 |
2020年 | 314篇 |
2019年 | 336篇 |
2018年 | 359篇 |
2017年 | 459篇 |
2016年 | 439篇 |
2015年 | 347篇 |
2014年 | 633篇 |
2013年 | 1083篇 |
2012年 | 818篇 |
2011年 | 738篇 |
2010年 | 674篇 |
2009年 | 903篇 |
2008年 | 943篇 |
2007年 | 982篇 |
2006年 | 782篇 |
2005年 | 700篇 |
2004年 | 553篇 |
2003年 | 540篇 |
2002年 | 492篇 |
2001年 | 440篇 |
2000年 | 441篇 |
1999年 | 342篇 |
1998年 | 402篇 |
1997年 | 334篇 |
1996年 | 253篇 |
1995年 | 244篇 |
1994年 | 218篇 |
1993年 | 179篇 |
1992年 | 171篇 |
1991年 | 130篇 |
1990年 | 112篇 |
1989年 | 89篇 |
1988年 | 85篇 |
1987年 | 76篇 |
1986年 | 79篇 |
1985年 | 99篇 |
1984年 | 88篇 |
1983年 | 37篇 |
1982年 | 57篇 |
1981年 | 47篇 |
1980年 | 58篇 |
1979年 | 72篇 |
1978年 | 47篇 |
1977年 | 52篇 |
1976年 | 47篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
在等离子体增强化学气相淀积系统中,采用aSi:H层淀积和原位等离子体氧化相结合的逐层生长技术制备了aSi:H/SiO_2多层膜.在激光诱导限制结晶原理基础上,使用KrF准分子脉冲激光为辐照源,对aSi:H/SiO_2多层膜进行辐照,使纳米级厚度的aSi:H子层晶化.Raman散射谱和电子衍射谱的结果表明,经过激光辐照后纳米Si颗粒在原始的aSi:H子层内形成,晶粒尺寸可以根据aSi:H层的厚度精确控制.还研究了样品的光致发光(PL)特性以及激光辐照能量密度对PL性质的影响.
关键词:
脉冲激光
多层膜
限制结晶 相似文献
53.
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
54.
We introduce extensions of the Mangasarian-Fromovitz and Abadie constraint qualifications to nonsmooth optimization problems with feasibility given by means of lower-level sets. We do not assume directional differentiability, but only upper semicontinuity of the defining functions. By deriving and reviewing primal first-order optimality conditions for nonsmooth problems, we motivate the formulations of the constraint qualifications. Then, we study their interrelation, and we show how they are related to the Slater condition for nonsmooth convex problems, to nonsmooth reverse-convex problems, to the stability of parametric feasible set mappings, and to alternative theorems for the derivation of dual first-order optimality conditions.In the literature on general semi-infinite programming problems, a number of formally different extensions of the Mangasarian-Fromovitz constraint qualification have been introduced recently under different structural assumptions. We show that all these extensions are unified by the constraint qualification presented here. 相似文献
55.
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
56.
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
57.
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
58.
By extracting combinatorial structures in well-solved nonlinear combinatorial optimization problems, Murota (1996,1998) introduced the concepts of M-convexity and L-convexity to functions defined over the integer lattice. Recently, Murota–Shioura (2000, 2001) extended these concepts to polyhedral convex functions and quadratic functions in continuous variables. In this paper, we consider a further extension to more general convex functions defined over the real space, and provide a proof for the conjugacy relationship between general M-convex and L-convex functions.Mathematics Subject Classification (1991): 90C10, 90C25, 90C27, 90C35This work is supported by Grant-in-Aid of the Ministry of Education, Culture, Sports, Science and Technology of Japan 相似文献
59.
Patrick Guidotti 《Mathematische Nachrichten》2004,272(1):32-45
We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
60.
Many real problems can be modelled as robust shortest path problems on interval digraphs, where intervals represent uncertainty about real costs and a robust path is not too far from the shortest path for each possible configuration of the arc costs.A branch and bound algorithm for this problem is presented. 相似文献