全文获取类型
收费全文 | 2106篇 |
免费 | 58篇 |
国内免费 | 59篇 |
专业分类
化学 | 9篇 |
力学 | 212篇 |
综合类 | 2篇 |
数学 | 1893篇 |
物理学 | 107篇 |
出版年
2023年 | 28篇 |
2022年 | 27篇 |
2021年 | 26篇 |
2020年 | 33篇 |
2019年 | 55篇 |
2018年 | 48篇 |
2017年 | 43篇 |
2016年 | 36篇 |
2015年 | 34篇 |
2014年 | 114篇 |
2013年 | 211篇 |
2012年 | 55篇 |
2011年 | 129篇 |
2010年 | 121篇 |
2009年 | 147篇 |
2008年 | 180篇 |
2007年 | 143篇 |
2006年 | 113篇 |
2005年 | 86篇 |
2004年 | 90篇 |
2003年 | 81篇 |
2002年 | 57篇 |
2001年 | 49篇 |
2000年 | 33篇 |
1999年 | 31篇 |
1998年 | 44篇 |
1997年 | 36篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2223条查询结果,搜索用时 15 毫秒
991.
王启华 《数学物理学报(B辑英文版)》1997,(2)
1IntroductionInmaplifetimestudies,someOfthesubjects"liderstudyarecensoredontherightbyapriorcensoringtime.LetTI,T2,'',TibeindependentandidenticallydistributednonnegativerandomvariableswithcommoncontinuousdistributionfullctionFandcontinuousprobabilitydensityfunctionf.Inthemodelofrightrandomcensoring,associatedwitheachZthereisanindependentnonnegativecensringtimeCiandCI,C2,'',CdareassumedtobelidrandomvariableswithcontinuotisdistributionfunctiollG.Illthismodelwecanobserveonlythepairs(Xi,hi)… 相似文献
992.
Let be the group of monomial matrices, i.e., the group generated by all permutation matrices and diagonal matrices in . The group acts on the set of all subspaces of . The number of orbits of this action, denoted by Nn,q, is the number of non-equivalent linear codes in . It was conjectured by Lax that as n→∞. We confirm this conjecture in this paper. 相似文献
993.
In this letter we consider a linear differential system with multiple delays which has nonisolated equilibria. In order to study the asymptotic behavior of linear delay differential equations, characteristic equations are generally used. But it is hard to establish the properties of zeros of the characteristic equations, especially if there are multiple time delays. So we use the invariance principle combined with two functionals to show whether any solutions converge. One of the functionals plays the role of a Lyapunov functional, and the other is a conserved quantity. Furthermore we give explicit expressions for the limits of the solutions by using the conserved quantity. 相似文献
994.
M. H. Lantsman 《Mathematische Nachrichten》1999,204(1):137-156
Given a linear differential equation of the form x (n) + a1 (t) x (n-1) + …+ an (t) x = 0 with variable coefficients defined on the positive semi -axis for t ? 1. We denote its fundamental set of solutions (FSS) by {exp [∫ ri (t) dt] } (i = 1, 2,…,n). In this paper we look for the asymptotic connection (as t → ∞) between the logarithmic derivatives ri (t) of an FSS and of the roots of the characteristic equation yn + a1 (t) yn-1 +… + an (t) = 0. We mainly consider the case when the coefficients of the equation and the characteristic roots are comparable and have the power order of growth for t → ∞. We discuss the conditions when the functions λii(t) are equivalent to the corresponding roots λii(t) of the characteristic equation as t → ∞. 相似文献
995.
Annalisa Cesaroni 《Applied Mathematics and Optimization》2006,53(1):1-29
We prove optimality principles for semicontinuous bounded viscosity solutions of Hamilton-Jacobi-Bellman equations. In particular,
we provide a representation formula for viscosity supersolutions as value functions of suitable obstacle control problems.
This result is applied to extend the Lyapunov direct method for stability to controlled Ito stochastic differential equations.
We define the appropriate concept of the Lyapunov function to study stochastic open loop stabilizability in probability and
local and global asymptotic stabilizability (or asymptotic controllability). Finally, we illustrate the theory with some examples. 相似文献
996.
An approximate formula for the Black–Scholes implied volatility is given by means of an asymptotic representation of the Black–Scholes formula. This representation is based on a variable change that reduces the number of meaningful variables from five to three. It is stated clearly which is the family of functions we are going to work, specially the inverse of the normal accumulative function. Estimates for the error in the resulting approximate formulas for both the option value and the volatility are obtained as well. 相似文献
997.
Albrecht Böttcher Harold Widom 《Journal of Mathematical Analysis and Applications》2006,322(2):990-1000
We consider the operator of taking the 2pth derivative of a function with zero boundary conditions for the function and its first p−1 derivatives at two distinct points. Our main result provides an asymptotic formula for the eigenvalues and resolves a question on the appearance of certain regular numbers in the eigenvalue sequences for p=1 and p=3. 相似文献
998.
李傅山 《数学年刊A辑(中文版)》2007,(1)
应用渐近分析的方法和拉普拉斯变换,证明了3维线性粘弹性壳的位移在一定条件下收敛于2维线性粘弹性弯壳方程组的解. 相似文献
999.
The asymptotic behavior of the least squares (LS) estimators of the parameters in threshold autoregressive models has been completely studied in the literature. It is well known that in some cases the least absolute deviation (LAD) estimators are superior to the LS-estimators. This paper is devoted to studying the strong consistency and the asymptotic normality of the LAD-estimators in two cases where the threshold is known and/or unknown. 相似文献
1000.
Solomon W. Harrar Arjun K. Gupta 《Annals of the Institute of Statistical Mathematics》2007,59(3):531-556
In this paper we derive the asymptotic expansion of the null distribution of the F-statistic in one-way ANOVA under non-normality. The asymptotic framework is when the number of treatments is moderate but
sample size per treatment (replication size) is small. This kind of asymptotics will be relevant, for example, to agricultural
screening trials where large number of cultivars are compared with few replications per cultivar. There is also a huge potential
for the application of this kind of asymptotics in microarray experiments. Based on the asymptotic expansion we will devise
a transformation that speeds up the convergence to the limiting distribution. The results indicate that the approximation
based on limiting distribution are unsatisfactory unless number of treatments is very large. Our numerical investigations
reveal that our asymptotic expansion performs better than other methods in the literature when there is skewness in the data
or even when the data comes from a symmetric distribution with heavy tails. 相似文献