全文获取类型
收费全文 | 2434篇 |
免费 | 350篇 |
国内免费 | 92篇 |
专业分类
化学 | 309篇 |
晶体学 | 3篇 |
力学 | 73篇 |
综合类 | 25篇 |
数学 | 1108篇 |
物理学 | 1358篇 |
出版年
2023年 | 17篇 |
2022年 | 53篇 |
2021年 | 51篇 |
2020年 | 47篇 |
2019年 | 59篇 |
2018年 | 47篇 |
2017年 | 66篇 |
2016年 | 73篇 |
2015年 | 67篇 |
2014年 | 146篇 |
2013年 | 178篇 |
2012年 | 115篇 |
2011年 | 150篇 |
2010年 | 103篇 |
2009年 | 133篇 |
2008年 | 176篇 |
2007年 | 168篇 |
2006年 | 138篇 |
2005年 | 115篇 |
2004年 | 98篇 |
2003年 | 102篇 |
2002年 | 94篇 |
2001年 | 77篇 |
2000年 | 74篇 |
1999年 | 75篇 |
1998年 | 70篇 |
1997年 | 46篇 |
1996年 | 46篇 |
1995年 | 28篇 |
1994年 | 29篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有2876条查询结果,搜索用时 15 毫秒
891.
H.?X.?Chen N.?A.?LiuEmail author L.?F.?Shu R.?W.?Zong 《Journal of Thermal Analysis and Calorimetry》2004,78(3):1029-1041
Due to the experimental errors, the chemical effect of minor reactions, and some physical effects of heat and mass transfer, there usually exists much noise in the mass loss data resulted from thermal decomposition experiments, and thus high quality smoothing algorithm plays an important role in obtaining reliable derivative thermogravimetric (DTG) curves required for differential kinetic analysis. In this paper three smoothing methods, i.e. Moving Average smoothing, Gaussian smoothing, and Vondrak smoothing, are investigated in detail for pre-treatment of biomass decomposition data to obtain the DTG curves, and the smoothing results are compared. It is concluded that by choosing reasonable smoothing parameters based on the spectrum analysis of the data, the Gaussian smoothing and Vondrak smoothing can be reliably used to obtain DTG curves. The kinetic parameters calculated from the original TG curves and smoothed DTG curves have excellent agreement, and thus the Gaussian and Vondrak smoothing algorithms can be used directly and accurately in kinetic analysis.This work was sponsored by National Natural Science Foundation of China under Grants 50346038 and 50323005, the China NKBRSF project (No. 2001CB409600), the Anhui Excellent Youth Scientist Fundation (2004–2005), the Specialized Research Fund for the Doctoral Program of Higher Education and the National Key Technologies R&D Programme (2001BA510B09-03). 相似文献
892.
T. Sottinen 《Journal of Theoretical Probability》2004,17(2):309-325
We consider Gaussian processes that are equivalent in law to the fractional Brownian motion and their canonical representations. We prove a Hitsuda type representation theorem for the fractional Brownian motion with Hurst index H1/2. For the case H>1/2 we show that such a representation cannot hold. We also consider briefly the connection between Hitsuda and Girsanov representations. Using the Hitsuda representation we consider a certain special kind of Gaussian stochastic equation with fractional Brownian motion as noise. 相似文献
893.
In this paper we consider the existence problem for the elliptic equation on , which arises in the study of conformal deformation of the hyperbolic disc. We prove an existence result for the above equation.
894.
The maximum of a continuous, locally stationary Gaussian process which satisfies Bermans condition on the long range dependence is compared with the maximum of this process sampled at discrete time points. These two extreme values are asymptotically totally dependent if the grid of the discrete time points is sufficiently dense, and asymptotically independent if the the grid points are sparse.AMS 2000 Subject Classification. Primary—60F05, Secondary—60G15 相似文献
895.
HuiXiaHE ZiZhouTANG 《数学学报(英文版)》2004,20(6):961-964
The main purpose of this paper is to show that there is an isometric embedding from Moebius band to R4 with positive Gaussian curvature. 相似文献
896.
Let X, X
1, X
2,... be a sequence of independent and identically distributed random variables with common distribution function F. Denote by F
n
the distribution function of centered and normed sum S
n
. Let F belong to the domain of attraction of the standard normal law , that is, lim F
n
(x)= (x), as n , uniformly in x . We obtain extended asymptotic expansions for the particular case where the distribution function F has the density p(x) = cx
––1 ln(x), x > r, where 2, , c > 0, and r > 1. We write the classical asymptotic expansion (in powers of n
–1/2) and then add new terms of orders n
–/2 ln
n, n
–/2 ln-1
n, etc., where 0. 相似文献
897.
A class of functions and the corresponding solutions of
are obtained as a special case of the solutions of
where is defined as .
898.
899.
In the presence of Gaussian white noise, we study the properties of voltage-controlled oscillator neuron model and discuss the effects of the additive and multiplicative noise.
It is found that the additive noise can accelerate and counterwork
the firing of neuron, which depends on the value of central frequency of neuron itself, while multiplicative noise can induce the continuous change or mutation of membrane potential. 相似文献
900.
There exists rare integration formulas over quaternions due to the
noncommutativity of quarternions multplication. Based on the class
operator's formula of rotation group we derive a Gaussian integral formula
for quaternions, which is similar in form to the integration for coherent
state's completeness relation. 相似文献