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81.
Polyharmonic splines are used to interpolate data in a stationary multilevel iterative refinement scheme. By using such functions the necessary tools are provided to obtain simple pointwise error bounds on the approximation. Linear convergence between levels is shown for regular data on a scaled multiinteger grid, and a multilevel domain decomposition method. 相似文献
82.
83.
J. Fang 《Optics & Laser Technology》1991,23(6):349-352
A rotational mismatch of gratings is used to generate a fringe carrier of an in-plane moiré pattern so that specimen deformation shows itself in the form of modulation of the carrier frequency. As both the unmodulated and modulated carriers are the patterns without fringe-loop or fringe-connection, they are automatically numbered with monotonical increasing orders by a digital image processing system without any ambiguity. The orders at every pixel of the image are determined by interpolation of the orders of the tracked fringes to establish two grey image files, from the difference of which, the orders of the in-plane displacement moiré are displayed with grey-level variation. 相似文献
84.
We have generalized the coherent potential approximation (CPA) of Tripathi and Behera to the case of ann-component alloy. It is seen that then-component CPA density of states reproduces the binary, ternary quartenary alloys etc when the appropriate limits are adopted. 相似文献
85.
对称正交反对称矩阵反问题解存在的条件 总被引:25,自引:1,他引:24
戴华 《高等学校计算数学学报》2002,24(2):169-178
矩阵反问题和矩阵特征值反问题在科学和工程技术中具有广泛的应用,有关它们的研究已取得了许多进展[1,2].[3]和[4]分别研究了反对称矩阵反问题和双反对称矩阵特征值反问题等.本文研究一类更广泛的对称正交反对称矩阵反问题.用Rn×m(Cn×m)表示n×m实(复)矩阵的全体,ASRn×n表示n阶反对称矩阵的全体,ABSRn×n表示n阶双反对称矩阵的全体,ORn×n表示n阶正交矩阵的全体.A+表示矩阵A的Moore-Penrose广义逆.In表示n阶单位矩阵.ei表示n阶单位矩阵的第i列,Sn=[en,en-1, 相似文献
86.
Roland Opfer 《Advances in Computational Mathematics》2006,25(4):357-380
This paper reconstructs multivariate functions from scattered data by a new multiscale technique. The reconstruction uses
standard methods of interpolation by positive definite reproducing kernels in Hilbert spaces. But it adopts techniques from
wavelet theory and shift-invariant spaces to construct a new class of kernels as multiscale superpositions of shifts and scales
of a single compactly supported function φ. This means that the advantages of scaled regular grids are used to construct the
kernels, while the advantages of unrestricted scattered data interpolation are maintained after the kernels are constructed.
Using such a multiscale kernel, the reconstruction method interpolates at given scattered data. No manipulations of the data
(e.g., thinning or separation into subsets of certain scales) are needed. Then, the multiscale structure of the kernel allows
to represent the interpolant on regular grids on all scales involved, with cheap evaluation due to the compact support of
the function φ, and with a recursive evaluation technique if φ is chosen to be refinable. There also is a wavelet-like data
reduction effect, if a suitable thresholding strategy is applied to the coefficients of the interpolant when represented over
a scaled grid. Various numerical examples are presented, illustrating the multiresolution and data compression effects. 相似文献
87.
Carsten Franz 《Proceedings of the American Mathematical Society》2006,134(8):2437-2446
A method to approximate the eigenvalues of linear operators depending on an unknown distribution is introduced and applied to weighted sums of squared normally distributed random variables. This area of application includes the approximation of the asymptotic null distribution of certain degenerated U- and V-statistics.
88.
Two matrix approximation problems are considered: approximation of a rectangular complex matrix by subunitary matrices with
respect to unitarily invariant norms and a minimal rank approximation with respect to the spectral norm. A characterization
of a subunitary approximant of a square matrix with respect to the Schatten norms, given by Maher, is extended to the case
of rectangular matrices and arbitrary unitarily invariant norms. Iterative methods, based on the family of Gander methods
and on Higham’s scaled method for polar decomposition of a matrix, are proposed for computing subunitary and minimal rank
approximants. Properties of Gander methods are investigated in details.
AMS subject classification (2000) 65F30, 15A18 相似文献
89.
利用傅里叶光学理论,证明了一种新型波面传感器——旋转软刀口波面传感器的概念.在经典刀口法的刀口区,以渐变透过率代替突变透过率函数,在光瞳象面上可获得反映光瞳面位置待测波面位相梯度及位相梯度方向的调制信号.文中给出了实验结果和讨论. 相似文献
90.
We generalize a variational principle for the mean spherical approximation for a system of charged hard spheres in 3D to arbitrary
dimensions. We first construct a free energy variational trial function from the Debye-Hückel excess charging internal energy
at a finite concentration and an entropy obtained at the zero-concentration limit by thermodynamic integration. In three dimensions
the minimization of this expression with respect to the screening parameter leads to the mean spherical approximation, usually
obtained by solution of the Ornstein-Zernike equation. This procedure, which interpolates naturally between the zero concentration/coupling
limit and the high-concentration/ coupling limit, is extended to arbitrary dimensions. We conjecture that this result is also
equivalent to the MSA as originally defined, although a technical proof of this point is left for the future. The Onsager
limitT ΔS
MSA
/ΔE
MSA
→ 0 for infinite concentration/coupling is satisfied for all d ≠ 2, while ford=2 this limit is 1.
On leave from Department of Physics, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico, 00681. 相似文献