全文获取类型
收费全文 | 7170篇 |
免费 | 873篇 |
国内免费 | 490篇 |
专业分类
化学 | 490篇 |
晶体学 | 2篇 |
力学 | 565篇 |
综合类 | 189篇 |
数学 | 5705篇 |
物理学 | 1582篇 |
出版年
2024年 | 8篇 |
2023年 | 77篇 |
2022年 | 152篇 |
2021年 | 200篇 |
2020年 | 173篇 |
2019年 | 184篇 |
2018年 | 176篇 |
2017年 | 271篇 |
2016年 | 290篇 |
2015年 | 186篇 |
2014年 | 407篇 |
2013年 | 607篇 |
2012年 | 349篇 |
2011年 | 372篇 |
2010年 | 352篇 |
2009年 | 417篇 |
2008年 | 467篇 |
2007年 | 421篇 |
2006年 | 359篇 |
2005年 | 364篇 |
2004年 | 262篇 |
2003年 | 243篇 |
2002年 | 258篇 |
2001年 | 240篇 |
2000年 | 216篇 |
1999年 | 191篇 |
1998年 | 162篇 |
1997年 | 145篇 |
1996年 | 123篇 |
1995年 | 111篇 |
1994年 | 96篇 |
1993年 | 63篇 |
1992年 | 51篇 |
1991年 | 53篇 |
1990年 | 56篇 |
1989年 | 44篇 |
1988年 | 29篇 |
1987年 | 48篇 |
1986年 | 25篇 |
1985年 | 62篇 |
1984年 | 32篇 |
1983年 | 22篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1974年 | 11篇 |
排序方式: 共有8533条查询结果,搜索用时 15 毫秒
1.
2.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients
下载免费PDF全文
![点击此处可从《分析论及其应用》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献
3.
Motor Imagery Electroencephalography (MI-EEG) has shown good prospects in neurorehabilitation, and the entropy-based nonlinear dynamic methods have been successfully applied to feature extraction of MI-EEG. Especially based on Multiscale Fuzzy Entropy (MFE), the fuzzy entropies of the τ coarse-grained sequences in τ scale are calculated and averaged to develop the Composite MFE (CMFE) with more feature information. However, the coarse-grained process fails to match the nonstationary characteristic of MI-EEG by a mean filtering algorithm. In this paper, CMFE is improved by assigning the different weight factors to the different sample points in the coarse-grained process, i.e., using the weighted mean filters instead of the original mean filters, which is conductive to signal filtering and feature extraction, and the resulting personalized Weighted CMFE (WCMFE) is more suitable to represent the nonstationary MI-EEG for different subjects. All the WCMFEs of multi-channel MI-EEG are fused in serial to construct the feature vector, which is evaluated by a back-propagation neural network. Based on a public dataset, extensive experiments are conducted, yielding a relatively higher classification accuracy by WCMFE, and the statistical significance is examined by two-sample t-test. The results suggest that WCMFE is superior to the other entropy-based and traditional feature extraction methods. 相似文献
4.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
5.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
6.
ZHANG Shibin ZHANG Xinsheng & SUN Shuguang School of Management Fudan University Shanghai China Department of Mathematics Shanghai Maritime University Shanghai China 《中国科学A辑(英文版)》2006,49(9):1231-1257
The stationary Gamma-OU processes are recommended to be the volatility of the financial assets. A parametric estimation for the Gamma-OU processes based on the discrete observations is considered in this paper. The estimator of an intensity parameter A and its convergence result are given, and the simulations show that the estimation is quite accurate. Assuming that the parameter A is estimated, the maximum likelihood estimation of shape parameter c and scale parameter a, whose likelihood function is not explicitly computable, is considered. By means of the Gaver-Stehfest algorithm, we construct an explicit sequence of approximations to the likelihood function and show that it converges the true (but unkown) one. Maximizing the sequence results in an estimator that converges to the true maximum likelihood estimator and the approximation shares the asymptotic properties of the true maximum likelihood estimator. Some simulation experiments reveal that this method is still quite accurate in most of rational situations for the background of volatility. 相似文献
7.
8.
随着图像系统的广泛应用,对图像的稳定要求也越来越高。图像的运动和不稳定是常见的,往往是由于载体的运动引起的,为了达到图像稳定的目的,就需要对其运动进行描述,然后采用相应的算法进行补偿。给出了运动对图像清晰度的影响及像偏移的估算,并对数字电子图像稳定系统进行了简单阐述。 相似文献
9.
We consider some Sobolev-type spaces and obtain a necessary and sufficient condition for their embedding in a Lebesgue space. 相似文献
10.
文贤章 《高校应用数学学报(A辑)》2002,17(3):291-302
利用最大值原理结合上、下解的方法,讨论了一类具有扩散的竞争-捕食的Lotka-Volterra系统静态解的存在性与持续生存。 相似文献