全文获取类型
收费全文 | 4739篇 |
免费 | 576篇 |
国内免费 | 322篇 |
专业分类
化学 | 963篇 |
晶体学 | 8篇 |
力学 | 633篇 |
综合类 | 102篇 |
数学 | 2794篇 |
物理学 | 1137篇 |
出版年
2024年 | 5篇 |
2023年 | 58篇 |
2022年 | 145篇 |
2021年 | 128篇 |
2020年 | 124篇 |
2019年 | 117篇 |
2018年 | 106篇 |
2017年 | 186篇 |
2016年 | 186篇 |
2015年 | 157篇 |
2014年 | 248篇 |
2013年 | 334篇 |
2012年 | 195篇 |
2011年 | 268篇 |
2010年 | 252篇 |
2009年 | 230篇 |
2008年 | 276篇 |
2007年 | 274篇 |
2006年 | 278篇 |
2005年 | 247篇 |
2004年 | 184篇 |
2003年 | 208篇 |
2002年 | 201篇 |
2001年 | 183篇 |
2000年 | 160篇 |
1999年 | 142篇 |
1998年 | 108篇 |
1997年 | 102篇 |
1996年 | 103篇 |
1995年 | 79篇 |
1994年 | 58篇 |
1993年 | 51篇 |
1992年 | 44篇 |
1991年 | 21篇 |
1990年 | 28篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 19篇 |
1985年 | 26篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1974年 | 3篇 |
排序方式: 共有5637条查询结果,搜索用时 15 毫秒
21.
R. N. Miroshin 《Mathematical Notes》2007,82(3-4):357-365
Multiple integrals generalizing the iterated kernels of integral operators are expressed as single integrals in the case of a special representation of the kernel (this is our theorem). Besides integral equations, Markov processes involve these integrals as well. As a consequence of the theorem, we obtain transition probability densities of certain Markov processes. As an illustration, we consider nine examples. 相似文献
22.
We study a class of ‘nonpoissonian’ transformations of the configuration space and the corresponding transformations of the Poisson measure. For some class of Poisson measures we find conditions which are sufficient for the transformed measure (which in general is nonpoissonian) to be absolutely continuous with respect to the initial Poisson measure and get the expression for the corresponding Radon–Nikodym derivative. To solve this problem we use a distributional approach to Poisson multiple stochastic integrals. 相似文献
23.
“选择资费”的多重价格歧视特性 总被引:3,自引:0,他引:3
本文在分析电信业选择资费实例和价格结构的基础上 ,研究了选择资费中的三级和二级价格歧视 ,并提出了多重价格歧视的概念 .研究结果表明 ,电信公司在选择资费中综合运用了三级、二级价格歧视 ,且通过提供多个二部资费计费方案 ,达到双重二级价格歧视和优化二部资费的目的 .选择资费是电信公司应对市场竞争的一种定价策略 ,认识其经济特性有利于我国电信公司和电信管制部门进行科学决策 相似文献
24.
F. Sibel Salman Jayant R. Kalagnanam Sesh Murthy Andrew Davenport 《Journal of Heuristics》2002,8(2):215-239
For hard optimization problems, it is difficult to design heuristic algorithms which exhibit uniformly superior performance for all problem instances. As a result it becomes necessary to tailor the algorithms based on the problem instance. In this paper, we introduce the use of a cooperative problem solving team of heuristics that evolves algorithms for a given problem instance. The efficacy of this method is examined by solving six difficult instances of a bicriteria sparse multiple knapsack problem. Results indicate that such tailored algorithms uniformly improve solutions as compared to using predesigned heuristic algorithms. 相似文献
25.
Pankaj Mathur 《分析论及其应用》2006,22(2):105-113
In this paper, we study the explicit representation and convergence of (0, 1;0)-interpolation on infisite interval, which means to determine a polynomial of degree ≤ 3n - 2 when the function values areprescribed at two set of points namely the zeros of Hn(x) and H′n (x) and the first derivatives at the zerosof H′n(x). 相似文献
26.
本文介绍非线性方程转化直线性方程和多元线性回归法来分析近代物理实验中塞曼效应分裂干涉圆环多处选点测量的处理过程。 相似文献
27.
Let φ be a normal function on [0,1) and A'(φ)(1
相似文献
28.
Suppose that the signal X to be estimated is a diffusion process in a random medium W and the signal is correlated with the observation noise. We study the historical filtering problem concerned with estimating the signal path up until the current time based upon the back observations. Using Dirichlet form theory, we introduce a filtering model for general rough signal X
W
and establish a multiple Wiener integrals representation for the unnormalized pathspace filtering process. Then, we construct a precise nonlinear filtering model for the process X itself and give the corresponding Wiener chaos decomposition. 相似文献
29.
The interplay between inertia and elasticity is examined for transient free‐surface flow inside a narrow channel. The lubrication theory is extended for the flow of viscoelastic fluids of the Oldroyd‐B type (consisting of a Newtonian solvent and a polymeric solute). While the general formulation accounts for non‐linearities stemming from inertia effects in the momentum conservation equation, and the upper‐convected terms in the constitutive equation, only the front movement contributes to non‐linear coupling for a flow inside a straight channel. In this case, it is possible to implement a spectral representation in the depthwise direction for the velocity and stress. The evolution of the flow field is obtained locally, but the front movement is captured only in the mean sense. The influence of inertia, elasticity and viscosity ratio is examined for pressure‐induced flow. The front appears to progress monotonically with time. However, the velocity and stress exhibit typically a strong overshoot upon inception, accompanied by a plug‐flow behaviour in the channel core. The flow intensity eventually diminishes with time, tending asymptotically to Poiseuille conditions. For highly elastic liquids the front movement becomes oscillatory, experiencing strong deceleration periodically. A multiple‐scale solution is obtained for fluids with no inertia and small elasticity. Comparison with the exact (numerical) solution indicates a wide range of validity for the analytical result. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
30.
We propose a minimum mean absolute error linear interpolator (MMAELI), based on theL
1 approach. A linear functional of the observed time series due to non-normal innovations is derived. The solution equation
for the coefficients of this linear functional is established in terms of the innovation series. It is found that information
implied in the innovation series is useful for the interpolation of missing values. The MMAELIs of the AR(1) model with innovations
following mixed normal andt distributions are studied in detail. The MMAELI also approximates the minimum mean squared error linear interpolator (MMSELI)
well in mean squared error but outperforms the MMSELI in mean absolute error. An application to a real series is presented.
Extensions to the general ARMA model and other time series models are discussed.
This research was supported by a CityU Research Grant and Natural Science Foundation of China. 相似文献