全文获取类型
收费全文 | 6513篇 |
免费 | 849篇 |
国内免费 | 332篇 |
专业分类
化学 | 617篇 |
晶体学 | 6篇 |
力学 | 1018篇 |
综合类 | 63篇 |
数学 | 3615篇 |
物理学 | 2375篇 |
出版年
2024年 | 13篇 |
2023年 | 124篇 |
2022年 | 121篇 |
2021年 | 199篇 |
2020年 | 298篇 |
2019年 | 290篇 |
2018年 | 248篇 |
2017年 | 280篇 |
2016年 | 268篇 |
2015年 | 225篇 |
2014年 | 370篇 |
2013年 | 503篇 |
2012年 | 308篇 |
2011年 | 321篇 |
2010年 | 236篇 |
2009年 | 321篇 |
2008年 | 345篇 |
2007年 | 369篇 |
2006年 | 323篇 |
2005年 | 265篇 |
2004年 | 266篇 |
2003年 | 256篇 |
2002年 | 211篇 |
2001年 | 178篇 |
2000年 | 218篇 |
1999年 | 167篇 |
1998年 | 136篇 |
1997年 | 123篇 |
1996年 | 87篇 |
1995年 | 72篇 |
1994年 | 70篇 |
1993年 | 75篇 |
1992年 | 49篇 |
1991年 | 54篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 31篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 18篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1973年 | 12篇 |
1936年 | 4篇 |
排序方式: 共有7694条查询结果,搜索用时 0 毫秒
11.
Youssef Randjiou 《Journal of Theoretical Probability》2006,19(3):701-720
Let μ+(t) and μ−(t) be the locations of the maximum and minimum, respectively, of a standard Brownian motion in the interval [0,t]. We establish a joint integral test for the lower functions of μ+(t) and μ−(t), in the sense of Paul Lévy. In particular, it yields the law of the iterated logarithm for max(μ+(t),μ−(t)) as a straightforward consequence. Our result is in agreement with well-known theorems of Chung and Erdős [(1952) Trans. Amer. Math. Soc. 72, 179–186.], and Csáki, F?ldes and Révész [(1987) Prob. Theory Relat. Fields
76, 477–497].
相似文献
12.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of simpler linear differentialoperators and a nonlinear term. 相似文献
13.
Marianne Gerny Burkhard Alpers 《International Journal of Computers for Mathematical Learning》2004,9(1):25-57
In this article we describe a mathematical microworld for investigating car motion on a racing course and its use with a group of grade 12 students. The microworld is concerned with the mathematical construction of courses and functions which describe car motion. It is implemented in the computer algebra system, Maple®, which provides the means to represent courses and functions symbolically and graphically. We describe the learning opportunities offered by the microworld in relation to the research literature on functions. Various facets and layers of the function concept are addressed in the microworld, and we suggest how work in the microworld might help in overcoming some well-known misconceptions.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献
14.
15.
16.
尹传存 《数学物理学报(A辑)》1997,17(2):145-151
设中的角域.该文绘出了A上正调和函数的Martin表示,讨论了极小调和函数与条件Brown运动的一个0—1律之间的关系,并给出了A上极小调和函数的表现形式, 相似文献
17.
In a previous paper we gave a new formulation and derived the Euler equations and other necessary conditions to solve strong, pathwise, stochastic variational problems with trajectories driven by Brownian motion. Thus, unlike current methods which minimize the control over deterministic functionals (the expected value), we find the control which gives the critical point solution of random functionals of a Brownian path and then, if we choose, find the expected value.This increase in information is balanced by the fact that our methods are anticipative while current methods are not. However, our methods are more directly connected to the theory and meaningful examples of deterministic variational theory and provide better means of solution for free and constrained problems. In addition, examples indicate that there are methods to obtain nonanticipative solutions from our equations although the anticipative optimal cost function has smaller expected value.In this paper we give new, efficient numerical methods to find the solution of these problems in the quadratic case. Of interest is that our numerical solution has a maximal, a priori, pointwise error of O(h3/2) where h is the node size. We believe our results are unique for any theory of stochastic control and that our methods of proof involve new and sophisticated ideas for strong solutions which extend previous deterministic results by the first author where the error was O(h2).We note that, although our solutions are given in terms of stochastic differential equations, we are not using the now standard numerical methods for stochastic differential equations. Instead we find an approximation to the critical point solution of the variational problem using relations derived from setting to zero the directional derivative of the cost functional in the direction of simple test functions.Our results are even more significant than they first appear because we can reformulate stochastic control problems or constrained calculus of variations problems in the unconstrained, stochastic calculus of variations formulation of this paper. This will allow us to find efficient and accurate numerical solutions for general constrained, stochastic optimization problems. This is not yet being done, even in the deterministic case, except by the first author. 相似文献
18.
In the paper we indicate an error made in the proof of the main result of the paper [M.A. Darwish, On quadratic integral equation of fractional orders, J. Math. Anal. Appl. 311 (2005) 112-119]. Moreover, we provide correct proof of a slightly modified version of the mentioned result. The main tool used in our proof is the technique associated with the Hausdorff measure of noncompactness. 相似文献
19.
Optimality conditions are obtained for a nonlinear fractional multiobjective programming problem involving η-semidifferentiable functions. Also, a general dual is formulated and a duality result is proved using concepts of generalized ρ-semilocally type I-preinvex functions. 相似文献
20.