全文获取类型
收费全文 | 9080篇 |
免费 | 975篇 |
国内免费 | 873篇 |
专业分类
化学 | 1978篇 |
晶体学 | 15篇 |
力学 | 816篇 |
综合类 | 98篇 |
数学 | 6543篇 |
物理学 | 1478篇 |
出版年
2024年 | 39篇 |
2023年 | 143篇 |
2022年 | 267篇 |
2021年 | 322篇 |
2020年 | 449篇 |
2019年 | 332篇 |
2018年 | 297篇 |
2017年 | 274篇 |
2016年 | 321篇 |
2015年 | 283篇 |
2014年 | 341篇 |
2013年 | 809篇 |
2012年 | 347篇 |
2011年 | 429篇 |
2010年 | 365篇 |
2009年 | 544篇 |
2008年 | 564篇 |
2007年 | 564篇 |
2006年 | 465篇 |
2005年 | 376篇 |
2004年 | 349篇 |
2003年 | 328篇 |
2002年 | 295篇 |
2001年 | 245篇 |
2000年 | 241篇 |
1999年 | 219篇 |
1998年 | 240篇 |
1997年 | 190篇 |
1996年 | 145篇 |
1995年 | 115篇 |
1994年 | 109篇 |
1993年 | 91篇 |
1992年 | 81篇 |
1991年 | 61篇 |
1990年 | 59篇 |
1989年 | 45篇 |
1988年 | 45篇 |
1987年 | 46篇 |
1986年 | 50篇 |
1985年 | 65篇 |
1984年 | 57篇 |
1983年 | 30篇 |
1982年 | 42篇 |
1981年 | 40篇 |
1980年 | 50篇 |
1979年 | 45篇 |
1978年 | 31篇 |
1977年 | 31篇 |
1976年 | 33篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Wing-Sum Cheung Patricia J.Y. Wong 《Journal of Mathematical Analysis and Applications》2007,329(2):851-869
We consider a system of focal boundary value problems where the nonlinearities may be singular in the independent variable and may also be singular in the dependent arguments. Using Schauder fixed point theorem, we establish criteria such that the system of boundary value problems has at least one fixed-sign solution. 相似文献
92.
Alexandre N. Carvalho German Lozada-Cruz 《Journal of Mathematical Analysis and Applications》2007,325(2):1216-1239
We obtain existence of asymptotically stable nonconstant equilibrium solutions for semilinear parabolic equations with nonlinear boundary conditions on small domains connected by thin channels. We prove the convergence of eigenvalues and eigenfunctions of the Laplace operator in such domains. This information is used to show that the asymptotic dynamics of the heat equation in this domain is equivalent to the asymptotic dynamics of a system of two ordinary differential equations diffusively (weakly) coupled. The main tools employed are the invariant manifold theory and a uniform trace theorem. 相似文献
93.
A generalized inverse problem for the identification of the absorption coefficient for a hyperbolic system is considered. The well-posedness of the problem is examined. It is proved that the regular part of the solution is an L 2 function, which reduces the inverse problem to minimizing the error functional. The gradient of the functional is determined in explicit form from the adjoint problem, and approximate formulas for its calculation are derived. A regularization algorithm for the solution of the inverse problem is considered. Numerical results obtained for various excitation sources are displayed. 相似文献
94.
V. V. Panić A. B. Dekanski S. K. Milonjić V. B. Mišković-Stanković B. Ž. Nikolić 《Russian Journal of Electrochemistry》2006,42(10):1055-1060
Electrocatalytic properties of RuO2/Ti anode with different coating masses, which are prepared by the alkoxide sol-gel procedure, are investigated in chlorine
and oxygen evolution reactions by polarization measurements and electrochemical impedance spectroscopy in H2SO4 and NaCl electrolytes. According to polarization measurements, the activity of anodes at overpotentials below 100 mV is independent
of coating mass. However, impedance measurements above 100 mV reveal changes in the activity of anodes in chlorine evolution
reaction for different coating masses. The diffusion limitations related to the evolved chlorine are registered in low-frequency
domain at 1.10 V (SCE), diminishing with the increase in potential to the 1.15 V (SCE). The observed impedance behavior is
discussed with respect to the activity model for activated titanium anodes in chlorine evolution reaction involving formation
of gas channels within porous coating structure. Gas channels enhance the mass transfer rate similarly to the forced convection,
which also increases the activity of anode. This is more pronounced for the anode of greater coating mass due to its more
compact surface structure. The more compact structure appears to be beneficial for gas channels formation.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1173–1179.
The text was submitted by the authors in English. 相似文献
95.
In general, we will use the numerical differentiation when dealing with the differential equations. Thus the differential equations can be transformed into algebraic equations and then we can get the numerical solutions. But as we all have known, the numerical differentiation process is very sensitive to even a small level of errors. In contrast it is expected that on average the numerical integration process is much less sensitive to errors. In this paper, based on the Sinc method we provide a new method using Sinc method incorporated with the double exponential transformation based on the interpolation of the highest derivatives (SIHD) for the differential equations. The error in the approximation of the solution is shown to converge at an exponential rate. The numerical results show that compared with the exiting results, our method is of high accuracy, of good convergence with little computational efforts. It is easy to treat nonhomogeneous mixed boundary condition for our method, which is unlike the traditional Sinc method. 相似文献
96.
Chen-liang Li Jin-ping Zeng 《应用数学学报(英文版)》2007,23(1):79-90
We consider several synchronous and asynchronous multisplitting iteration schemes for solving aclass of nonlinear complementarity problems with the system matrix being an H-matrix.We establish theconvergence theorems for the schemes.The numerical experiments show that the schemes are efficient forsolving the class of nonlinear complementarity problems. 相似文献
97.
98.
Lina Mallozzi 《Operations Research Letters》2007,35(2):151-154
A noncooperative game theoretical approach is considered for the multifacility location problem. It turns out that the facility location game is a potential game in the sense of Monderer and Shapley and some properties of the game are studied. 相似文献
99.
Ivan Nunes da Silva Wagner Caradori do AmaralLucia Valeria de Arruda 《Applied Mathematical Modelling》2007
This paper presents an efficient approach based on recurrent neural network for solving nonlinear optimization. More specifically, a modified Hopfield network is developed and its internal parameters are computed using the valid subspace technique. These parameters guarantee the convergence of the network to the equilibrium points that represent an optimal feasible solution. The main advantage of the developed network is that it treats optimization and constraint terms in different stages with no interference with each other. Moreover, the proposed approach does not require specification of penalty and weighting parameters for its initialization. A study of the modified Hopfield model is also developed to analyze its stability and convergence. Simulation results are provided to demonstrate the performance of the proposed neural network. 相似文献
100.
A Hybrid Multiobjective Evolutionary Algorithm for Solving Vehicle Routing Problem with Time Windows 总被引:2,自引:0,他引:2
Vehicle routing problem with time windows (VRPTW) involves the routing of a set of vehicles with limited capacity from a central
depot to a set of geographically dispersed customers with known demands and predefined time windows. The problem is solved
by optimizing routes for the vehicles so as to meet all given constraints as well as to minimize the objectives of traveling
distance and number of vehicles. This paper proposes a hybrid multiobjective evolutionary algorithm (HMOEA) that incorporates
various heuristics for local exploitation in the evolutionary search and the concept of Pareto's optimality for solving multiobjective
optimization in VRPTW. The proposed HMOEA is featured with specialized genetic operators and variable-length chromosome representation
to accommodate the sequence-oriented optimization in VRPTW. Unlike existing VRPTW approaches that often aggregate multiple
criteria and constraints into a compromise function, the proposed HMOEA optimizes all routing constraints and objectives simultaneously,
which improves the routing solutions in many aspects, such as lower routing cost, wider scattering area and better convergence
trace. The HMOEA is applied to solve the benchmark Solomon's 56 VRPTW 100-customer instances, which yields 20 routing solutions
better than or competitive as compared to the best solutions published in literature. 相似文献