收费全文 | 3541篇 |
免费 | 139篇 |
国内免费 | 26篇 |
化学 | 2504篇 |
晶体学 | 20篇 |
力学 | 53篇 |
数学 | 552篇 |
物理学 | 577篇 |
2024年 | 5篇 |
2023年 | 27篇 |
2022年 | 65篇 |
2021年 | 97篇 |
2020年 | 88篇 |
2019年 | 105篇 |
2018年 | 118篇 |
2017年 | 81篇 |
2016年 | 138篇 |
2015年 | 129篇 |
2014年 | 147篇 |
2013年 | 205篇 |
2012年 | 239篇 |
2011年 | 259篇 |
2010年 | 174篇 |
2009年 | 113篇 |
2008年 | 242篇 |
2007年 | 241篇 |
2006年 | 215篇 |
2005年 | 190篇 |
2004年 | 149篇 |
2003年 | 119篇 |
2002年 | 99篇 |
2001年 | 44篇 |
2000年 | 32篇 |
1999年 | 38篇 |
1998年 | 34篇 |
1997年 | 23篇 |
1996年 | 31篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1973年 | 7篇 |
1954年 | 5篇 |
We present closed-form solutions to the problems of pricing of the perpetual American double lookback put and call options on the maximum drawdown and the maximum drawup with floating strikes in the Black-Merton-Scholes model. It is shown that the optimal exercise times are the first times at which the underlying risky asset price process reaches some lower or upper stochastic boundaries depending on the current values of its running maximum or minimum as well as the maximum drawdown or maximum drawup. The proof is based on the reduction of the original double optimal stopping problems to the appropriate sequences of single optimal stopping problems for the three-dimensional continuous Markov processes. The latter problems are solved as the equivalent free-boundary problems by means of the smooth-fit and normal-reflection conditions for the value functions at the optimal stopping boundaries and the edges of the three-dimensional state spaces. We show that the optimal exercise boundaries are determined as either the unique solutions of the associated systems of arithmetic equations or the minimal and maximal solutions of the appropriate first-order nonlinear ordinary differential equations.
相似文献
相似文献
38.
We study the partial differential equation
39.
Pavel Novotný 《Geometriae Dedicata》1994,50(1):53-55
This paper deals with the following kind of approximation of a convex bodyQ in Euclidean space E
n
by simplices: which is the smallest positive numberh
S(Q) such thatS
1 Q S
2 for a simplexS
1 and its homothetic copyS
2 of ratioh
S(Q). It is shown that ifS
0 is a simplex of maximal volume contained inQ, then a homothetic copy ofS
0 of ratio 13/3 containsQ. 相似文献
40.
Pavel Pyrih 《Potential Analysis》1994,3(3):273-281
We study the set of functions in quasi-analytic classes and the set of finely holomorphic functions. We show that no one of these two sets is contained in the other.LetI denote the set of complex functionsf: for which there exists a quasi-analytic classC{M
n} containingf. Let denote the set of complex functionsf: for which there exist a fine domainU containing the real line and a function
finely holomorphic onU satisfyingf(x)=
(x) for allx . The power of unique continuation is incomparable in these two cases (I\ is non-empty, \I is non-empty).Research supported by the grant No. 201/93/2174 of Czech Grant Agency and by the grant No. 354 of Charles University. 相似文献
|