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992.
Electrical capacitance tomography (ECT) is considered as a promising process tomography (PT) technology, and its successful applications depend mainly on the precision and speed of the image reconstruction algorithms. In this paper, based on the wavelet multi-scale analysis method, an efficient image reconstruction algorithm is presented. The original inverse problem is decomposed into a sequence of inverse problems, which are solved successively from the largest scale to the smallest scale. At different scales, the inverse problem is solved by a generalized regularized total least squares (TLS) method, which is developed using a combinational minimax estimation method and an extended stabilizing functional, until the solution of the original inverse problem is found. The homotopy algorithm is employed to solve the objective functional. The proposed algorithm is tested by the noise-free capacitance data and the noise-contaminated capacitance data, and excellent numerical performances and satisfactory results are observed. In the cases considered in this paper, the reconstruction results show remarkable improvement in the accuracy. The spatial resolution of the reconstructed images by the proposed algorithm is enhanced and the artifacts in the reconstructed images can be eliminated effectively. As a result, a promising algorithm is introduced for ECT image reconstruction. 相似文献
993.
In this paper, we investigate a Cauchy problem associated with Helmholtz-type equation in an infinite “strip”. This problem is well known to be severely ill-posed. The optimal error bound for the problem with only nonhomogeneous Neumann data is deduced, which is independent of the selected regularization methods. A framework of a modified Tikhonov regularization in conjunction with the Morozov’s discrepancy principle is proposed, it may be useful to the other linear ill-posed problems and helpful for the other regularization methods. Some sharp error estimates between the exact solutions and their regularization approximation are given. Numerical tests are also provided to show that the modified Tikhonov method works well. 相似文献
994.
We propose a periodic B-spline quasi-interpolation for multivariate functions on sparse grids and develop a fast scheme for the evaluation of a linear combination of B-splines on sparse grids. We prove that both of these operations require only O(nlogd−1n) number of multiplications, where n is the number of univariate B-spline basis functions used in each coordinate direction and d is the number of variables of the functions. We also establish the optimal approximation order of the periodic B-spline quasi-interpolation. Numerical examples are presented to confirm the theoretical estimates. 相似文献
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D.W. Burr O. Link G.J. Smallwood 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(6):1099-1107
Recovering the size distribution of aerosolized soot aggregates from multiangle elastic light scattering data requires the inversion of an integral equation, which is a mathematically ill-posed problem. This paper demonstrates how maximum a posteriori (MAP) inference can be used to stabilize the inversion by introducing prior information about the size distribution of the soot aggregates. Results show that the size distribution can be recovered using only simple smoothness and non-negativity priors if the aggregate number density is known, but otherwise it is necessary to specify additional information about the presumed distribution shape. 相似文献
998.
999.
基于三维变分同化(3DVAR)的思想,提出一种适用于多普勒天气雷达资料直接同化的正则化方法.从寻求Yo=H(X)带有偏差δ的极小模解出发,引入正则化思想,并给出与3DVAR方案不同的新代价函数.针对2008年8月14日发生在北京地区的一次局地暴雨过程,设计了一组数值试验,并采用L曲线准则后验选取最优正则化参数.数值结果表明:正则化方法和3DVAR方案均能有效同化多普勒雷达资料,雷达径向速度的同化效果明显好于反射率因
关键词:
多普勒雷达资料
正则化
3DVAR
降雨预报 相似文献
1000.
针对基于散射计地球物理模型函数的合成孔径雷达资料反演海面风场中背景风向存在很大误差的问题,提出了利用正则化方法反演海面风场,并通过L曲线准则对正则化参数进行最优选择,然后对该方法进行仿真试验.试验结果显示,正则化方法反演海面风场的风速和风向的反演精度均优于变分同化方法,分析不同真实风向情况下的反演精度表明,真实风向在45°和135°附近时,风速反演的精度高,真实风向在0°和90°时,风向反演的精度高,这种现象与地球物理模型函数中后向散射截面相对于风向的导数相关.
关键词:
合成孔径雷达
正则化
L曲线准则
变分同化 相似文献