全文获取类型
收费全文 | 10261篇 |
免费 | 398篇 |
国内免费 | 784篇 |
专业分类
化学 | 815篇 |
晶体学 | 7篇 |
力学 | 371篇 |
综合类 | 55篇 |
数学 | 6717篇 |
物理学 | 1141篇 |
综合类 | 2337篇 |
出版年
2024年 | 17篇 |
2023年 | 86篇 |
2022年 | 82篇 |
2021年 | 94篇 |
2020年 | 171篇 |
2019年 | 169篇 |
2018年 | 211篇 |
2017年 | 219篇 |
2016年 | 240篇 |
2015年 | 186篇 |
2014年 | 391篇 |
2013年 | 649篇 |
2012年 | 454篇 |
2011年 | 466篇 |
2010年 | 431篇 |
2009年 | 635篇 |
2008年 | 710篇 |
2007年 | 680篇 |
2006年 | 619篇 |
2005年 | 547篇 |
2004年 | 410篇 |
2003年 | 451篇 |
2002年 | 417篇 |
2001年 | 311篇 |
2000年 | 318篇 |
1999年 | 313篇 |
1998年 | 265篇 |
1997年 | 286篇 |
1996年 | 180篇 |
1995年 | 173篇 |
1994年 | 162篇 |
1993年 | 120篇 |
1992年 | 101篇 |
1991年 | 96篇 |
1990年 | 96篇 |
1989年 | 91篇 |
1988年 | 81篇 |
1987年 | 60篇 |
1986年 | 47篇 |
1985年 | 51篇 |
1984年 | 56篇 |
1983年 | 18篇 |
1982年 | 36篇 |
1981年 | 32篇 |
1980年 | 33篇 |
1979年 | 26篇 |
1978年 | 30篇 |
1977年 | 38篇 |
1976年 | 25篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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
72.
73.
Eugene A. Ustinov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(6):683-696
An analytic approach is proposed for the evaluation of weighting functions for remote sensing of a blackbody planetary atmosphere based on straightforward, general linearization. In the present paper, this approach is applied to the case of remote sensing with the nadir (down-looking) geometry. Expressions for weighting functions for various atmospheric parameters are derived. It is demonstrated that in a realistic case of temperature-dependent atmospheric absorption, an additional term appears in the expression for the temperature weighting function which contains the temperature derivative of the atmospheric absorption coefficient. The approach is applied to the case of a semi-infinite atmosphere and then, to the atmosphere of a finite optical depth with the underlying surface. In this, latter case, the expressions are also obtained for partial derivatives of observed radiances with respect to surface parameters: surface pressure, temperature and emissivity. 相似文献
74.
We study the degree distribution of the greatest common divisor of two or more random polynomials over a finite field ??q. We provide estimates for several parameters like number of distinct common irreducible factors, number of irreducible factors counting repetitions, and total degree of the gcd of two or more polynomials. We show that the limiting distribution of a random variable counting the total degree of the gcd is geometric and that the distributions of random variables counting the number of common factors (with and without repetitions) are very close to Poisson distributions when q is large. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006 相似文献
75.
Mira Bozzini Licia Lenarduzzi Robert Schaback 《Advances in Computational Mathematics》2002,16(4):375-387
We present an adaptive method to extract shape-preserving information from a univariate data sample. The behavior of the signal is obtained by interpolating at adaptively selected few data points by a linear combination of multiquadrics with variable scaling parameters. On the theoretical side, we give a sufficient condition for existence of the scaled multiquadric interpolant. On the practical side, we give various examples to show the applicability of the method. 相似文献
76.
郭天石 《四川理工学院学报(自然科学版)》2002,15(1):5-10
研究了在控制工程中常用拉普拉斯变换式的特点,对常用控制工程教材所附拉普拉斯变换表中的一些不完善之处进行了分析和订正。给出了检验原函数准确表达的方法,对MATLAB软件的某些符号运算结果提出了质疑。 相似文献
77.
P. Recht 《Mathematical Methods of Operations Research》1992,36(3):201-210
In this paper we present a concept of the construction of generalized gradients by considering a development of directional derivatives into spherical harmonics. This leads to a derivation system as a system of generalized partial derivatives. Necessary conditions for local extrema for a broad class of not necessarily differentiable function can be given and a characterization of points of differentiability can be proved by using generalized gradients. 相似文献
78.
戚鸣皋 《清华大学学报(自然科学版)》1991,(3)
设整数n≥3,定义二次均值 其中表示对模n的所有偶特征求和.证明了下列公式: 其中 φ(n)为Euler函数。 相似文献
79.
S Ponnusamy 《Proceedings Mathematical Sciences》1994,104(2):397-411
Denote byS
* (⌕), (0≤⌕<1), the family consisting of functionsf(z)=z+a
2z2+...+anzn+... that are analytic and starlike of order ⌕, in the unit disc ⋎z⋎<1. In the present article among other things, with very
simple conditions on μ, ⌕ andh(z) we prove the f’(z) (f(z)/z)μ−1<h(z) implies f∈S*(⌕). Our results in this direction then admit new applications in the study of univalent functions. In many cases these results
considerably extend the earlier works of Miller and Mocanu [6] and others. 相似文献
80.
本文把通常的光滑信赖域算法推广到非光滑情形,目标函数仅为局部李普希兹连续,文中子问题的目标函数不必是通常的二次逼近形式。 相似文献