全文获取类型
收费全文 | 4195篇 |
免费 | 132篇 |
国内免费 | 75篇 |
专业分类
化学 | 121篇 |
晶体学 | 1篇 |
力学 | 193篇 |
综合类 | 8篇 |
数学 | 3406篇 |
物理学 | 673篇 |
出版年
2024年 | 3篇 |
2023年 | 24篇 |
2022年 | 44篇 |
2021年 | 65篇 |
2020年 | 137篇 |
2019年 | 139篇 |
2018年 | 109篇 |
2017年 | 86篇 |
2016年 | 80篇 |
2015年 | 99篇 |
2014年 | 224篇 |
2013年 | 655篇 |
2012年 | 207篇 |
2011年 | 280篇 |
2010年 | 250篇 |
2009年 | 291篇 |
2008年 | 293篇 |
2007年 | 291篇 |
2006年 | 186篇 |
2005年 | 89篇 |
2004年 | 89篇 |
2003年 | 79篇 |
2002年 | 73篇 |
2001年 | 55篇 |
2000年 | 52篇 |
1999年 | 42篇 |
1998年 | 49篇 |
1997年 | 39篇 |
1996年 | 45篇 |
1995年 | 41篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 27篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 3篇 |
排序方式: 共有4402条查询结果,搜索用时 328 毫秒
11.
Jeannette H. C. Woerner 《商业与工业应用随机模型》2005,21(1):27-44
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
12.
A tomographic reconstruction method based on Monte Carlo random searching guided by the information contained in the projections
of radiographed objects is presented. In order to solve the optimization problem, a multiscale algorithm is proposed to reduce
computation. The reconstruction is performed in a coarse-to-fine multigrid scale that initializes each resolution level with
the reconstruction of the previous coarser level, which substantially improves the performance. The method was applied to
a real case reconstructing the internal structure of a small metallic object with internal components, showing excellent results. 相似文献
13.
A new stochastic method of reconstructing porous media 总被引:1,自引:0,他引:1
We present a new stochastic method of reconstructing porous medium from limited morphological information obtained from two-dimensional
micro- images of real porous medium. The method is similar to simulated annealing method in the capability of reconstructing
both isotropic and anisotropic structures of multi-phase but differs from the latter in that voxels for exchange are not selected
completely randomly as their neighborhood will also be checked and this new method is much simpler to implement and program.
We applied it to reconstruct real sandstone utilizing morphological information contained in porosity, two-point probability
function and linear-path function. Good agreement of those references verifies our developed method’s powerful capability.
The existing isolated regions of both pore phase and matrix phase do quite minor harm to their good connectivity. The lattice
Boltzmann method (LBM) is used to compute the permeability of the reconstructed system and the results show its good isotropy
and conductivity. However, due to the disadvantage of this method that the connectivity of the reconstructed system’s pore
space will decrease when porosity becomes small, we suggest the porosity of the system to be reconstructed be no less than
0.2 to ensure its connectivity and conductivity. 相似文献
14.
A stochastic approximation algorithm for estimating multichannel coefficients is proposed, and the estimate is proved to converge to the true parameters a.s. up-to a constant scaling factor. The estimate is updated after receiving each new observation, so the output data need not be collected in advance. The input signal is allowed to be dependent and the observation is allowed to be corrupted by noise, but no noise statistics are used in the estimation algorithm. 相似文献
15.
We present some results on the impact of demand variability on stocking policies and incentives to forecast, in the context of single period inventory-based contracts in a manufacturer-retailer channel. 相似文献
16.
Robust linear optimization under general norms 总被引:1,自引:0,他引:1
We explicitly characterize the robust counterpart of a linear programming problem with uncertainty set described by an arbitrary norm. Our approach encompasses several approaches from the literature and provides guarantees for constraint violation under probabilistic models that allow arbitrary dependencies in the distribution of the uncertain coefficients. 相似文献
17.
Yan Zhibin 《东北数学》1998,(2)
SomeNotesaboutTanaka'sEquationYanZhibin(严质彬)(DepartmentofMathematics,HarbinInstituteofTechnology,Harbin,150001)AbstractLet{Wt... 相似文献
18.
Fully and partially observed stochastic control of systems with nonlinear dynamics and terminal and running costs are considered.
Measure changes are introduced which allow both state and observation dynamics to be thought of as linear. In the case when
the terms of the cost have a special form the measure change transformation “cancels out” the nonlinearities and changes the
original nonlinear problem into a classical LQG one and standard results can be applied. We also consider unnormalized conditional
densities of the whole path as state variables and obtain dynamic programming and verification results.
R. J. Elliott wishes to acknowledge support of the Natural Sciences and Engineering Research Council of Canada, Grant A7964. 相似文献
19.
Recently, Fishbum and Lavalle (1995) and Lefèvre and Utev (1996) have considered some stochastic order relations specific for arithmetic random variables. The present work is concerned with these orderings, together with two other classes of stochastic order relations closely related. First, attention is paid to characterizations and various properties of all these orderings. Then, sufficient conditions of crossing-type for the two new classes of orderings are derived and extrema among discrete random variables are deduced. This is applied in actuarial sciences to obtain new bounds for the classical single life premiums as well as for the probability of ruin in the compound binomial risk model. 相似文献
20.
Y. Yavin 《Journal of Optimization Theory and Applications》1993,78(1):77-91
Stochastic optimal control techniques are applied to compare the performance of identical medium-range air-to-air missiles which have different thrust-mass profiles. The measure of the performance is the probability of reaching a lock-on-point with a favorable range of guidance and flight parameters, during a fixed time interval [0,t
f
], given that, during the flight, the trajectories of the missile are subjected to a variety of constraints including dynamic pressure constraints. 相似文献