全文获取类型
收费全文 | 959篇 |
免费 | 54篇 |
国内免费 | 50篇 |
专业分类
化学 | 167篇 |
力学 | 44篇 |
综合类 | 1篇 |
数学 | 342篇 |
物理学 | 509篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 39篇 |
2016年 | 40篇 |
2015年 | 21篇 |
2014年 | 61篇 |
2013年 | 53篇 |
2012年 | 59篇 |
2011年 | 65篇 |
2010年 | 35篇 |
2009年 | 87篇 |
2008年 | 68篇 |
2007年 | 71篇 |
2006年 | 62篇 |
2005年 | 48篇 |
2004年 | 69篇 |
2003年 | 38篇 |
2002年 | 32篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有1063条查询结果,搜索用时 15 毫秒
891.
A. Fraysse 《Journal of Functional Analysis》2010,258(6):1806-1821
In this paper we determine the multifractal nature of almost every function (in the prevalence setting) in a given Sobolev or Besov space according to different regularity exponents. These regularity criteria are based on local Lp regularity or on wavelet coefficients and give a precise information on pointwise behavior. 相似文献
892.
A wavelet-based morphological correlation (WBMC) is proposed as a new architecture to improve the properties of the classical morphological correlation (MC). For the WBMC, a dilated wavelet intensity function is introduced to filter the joint power spectrum (JPS) of the MC before final inverse Fourier transform. Computer simulation results show that, as compared with the linear correlation (LC), the conventional MC and the joint wavelet transform correlation (JWTC), the WBMC provides better discrimination capability with sharp and unmistakable correlation signal and its performance metrics are more stable under input outlier noise (salt-and-pepper noise). Although the WBMC loses illumination-invariance when input illumination factor is larger than unity, considerable discrimination capability is still maintained. 相似文献
893.
Simultaneous quantification of Cd2+ and Pb2+ in solution has been correctly targeted using the kinetic information from a single non-specific potentiometric sensor. Dual quantification was accomplished from the complex information in the transient response of an electrode used in a Sequential Injection Analysis (SIA) system and recorded after step injection of sample. Data was firstly preprocessed with the Discrete Wavelet Transform (DWT) to extract significant features and then fed into an Artificial Neural Network (ANN) for building the calibration model. DWT stage was optimized regarding the wavelet function and decomposition level, while the ANN stage was optimized on its structure. To simultaneously corroborate the effectiveness of the approach, two different potentiometric sensors were used as study case, one using a glass selective to Cd2+ and another a PVC membrane selective to Pb2+. 相似文献
894.
《应用光谱学评论》2013,48(4):429-450
ABSTRACT An introduction to the wavelet transform and its applications in spectroscopy analysis are presented. Owing to the property of the dual localization both in time and in frequency domains, the wavelet transform exhibits several useful characteristics. With the wavelet transform a signal can be decomposed into series of contributions according to the frequency difference, these contributions are respectively called discrete approximations and discrete details. By applying certain treatment to the discrete approximations (the low frequency part) or the discrete details (the high frequency part), a part of the original signal within a certain frequency range can be obtained. The wavelet transform has been applied in various fields of the analytical chemistry, including removal of high frequency noise, information extraction, resolution of overlapping signals, and data compression etc. Research concerning application in analytical chemistry are introduced in respect of photoacoustic spectroscopy, EXAFS spectrum, NMR analysis, and Raman spectrum. 相似文献
895.
896.
小波分析在气泡幕散射光信号处理中的应用 总被引:1,自引:0,他引:1
选取Daubechies小波对尾流气泡幕散射光信号做一维离散小波变换,小波阶数为3,尺度数Level为5,得到了原始信号的小波分析和重构误差结果.经db3小波分解,散射光信号的低频及高频部分区别不大,可能是信号采集频率过低(×10-1 s)导致的结果.对原始信号进行小波分析容易得到均值、中值、模式、标准差等统计量.通过对散射光信号进行一维平稳小波去噪、小波变换密度估计、小波系数选取等方面的分析,揭示了不同压强下散射光信号具有不同的性质. 相似文献
897.
898.
899.
天体光谱信号去噪的小波域复合阈值新算法 总被引:4,自引:3,他引:1
利用谱线和噪声在小波域内的不同相关特性,提出了一种小波域复合阈值去噪算法。首先将小波系数作NeighShrink阈值处理,然后对得到的小波系数进行二值化,在此基础上定义了每一小波系数所对应的横向相关性指数和纵向相关性指数,最后确定出决定小波系数取舍的决策系数。由于该决策系数是通过多重判据得到的,因此该方法克服了简单阈值方法过保留或过扼杀的缺点,同时可以去除大脉冲噪声,实验结果表明了该方法的有效性。 相似文献
900.
《Wave Motion》2020
An efficient numerical method is developed for the simulation of three dimensional transient dynamic response in thick laminated composite and sandwich plate structures involving very high frequencies and wave numbers. The proposed method incorporates Daubechies wavelet scaling functions for the interpolation of the in-plane displacements with a Galerkin formulation. It further explores the orthonormality and compact support of wavelet scaling functions to produce near diagonal consistent mass matrices and banded stiffness matrices. Hence, an uncoupled equivalent discrete spatial dynamic system is formulated, synthesized and rapidly solved in the wavelet domain using an explicit time integration scheme. The in-plane wavelet interpolation is further combined with an efficient high order layerwise laminate plate theory, that implements Hermite cubic splines for the through-the-thickness approximation of displacement fields. Numerical results are presented on the prediction of guided waves in laminated and thick sandwich composite plates and compared with respective solutions obtained by analytical, semi-analytical and time domain spectral element models. The method yielded higher convergence rates and substantial reductions in computational effort compared to respective time domain spectral finite elements. 相似文献