全文获取类型
收费全文 | 29411篇 |
免费 | 3094篇 |
国内免费 | 3226篇 |
专业分类
化学 | 2913篇 |
晶体学 | 46篇 |
力学 | 2315篇 |
综合类 | 760篇 |
数学 | 22006篇 |
物理学 | 7691篇 |
出版年
2024年 | 36篇 |
2023年 | 266篇 |
2022年 | 370篇 |
2021年 | 507篇 |
2020年 | 583篇 |
2019年 | 640篇 |
2018年 | 641篇 |
2017年 | 814篇 |
2016年 | 910篇 |
2015年 | 694篇 |
2014年 | 1420篇 |
2013年 | 1919篇 |
2012年 | 1426篇 |
2011年 | 1808篇 |
2010年 | 1653篇 |
2009年 | 2072篇 |
2008年 | 2103篇 |
2007年 | 2231篇 |
2006年 | 1923篇 |
2005年 | 1806篇 |
2004年 | 1432篇 |
2003年 | 1427篇 |
2002年 | 1207篇 |
2001年 | 1059篇 |
2000年 | 1059篇 |
1999年 | 908篇 |
1998年 | 837篇 |
1997年 | 746篇 |
1996年 | 541篇 |
1995年 | 387篇 |
1994年 | 350篇 |
1993年 | 251篇 |
1992年 | 205篇 |
1991年 | 172篇 |
1990年 | 175篇 |
1989年 | 115篇 |
1988年 | 114篇 |
1987年 | 90篇 |
1986年 | 80篇 |
1985年 | 116篇 |
1984年 | 95篇 |
1983年 | 56篇 |
1982年 | 89篇 |
1981年 | 71篇 |
1980年 | 58篇 |
1979年 | 52篇 |
1978年 | 42篇 |
1977年 | 36篇 |
1976年 | 37篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A greedy method for choosing an optimum reduced set of control points is integrated with RBF interpolation and evaluated for the purpose of interpolating large‐volume data sets in CFD. Given a function defined at a set of points, the greedy method selects a small subset of these points that is sufficient to keep the interpolation error at all the remaining points below a chosen bound. This is equivalent to a type of data compression and would have useful storage, post‐processing, and computational applications in CFD. To test the method in terms of both the point selection scheme and the suitability of reduced control point volume interpolation, a trial application of the interpolation to velocity fields in CFD volume meshes is considered. To optimise the point selection process, and attempt to be able to capture multiple length scales, a variable support radius formulation has also been included. Structured and unstructured mesh cases are considered for aerofoils, a wing case and a wing‐body case. For smooth volume functions, the method is shown to work well, producing accurate velocity interpolations using a very small number of the cells in the mesh. For general complex fields including large gradients, the method is still shown to be effective, although large gradients require more interpolation points to be used.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
992.
R. L. Ollerton A. G. Shannon 《International Journal of Mathematical Education in Science & Technology》2013,44(1):135-143
Teachers of first-year college mathematics and engineering courses must often spend considerable time reviewing material originally taught in high school. Instead of this being a mere exercise in repetition, this article suggests that such a review can enrich and revitalize by unifying some of the subjects that need to be re-taught. In the example presented, the subjects in question are absolute values, graphs and solutions of equations, and domains of definition. These are unified by the problem of finding an analytic expression for a square and triangle and their interiors. In the course of the development, basic notions such as the additive property of areas and convexity are introduced. The approach presented in the article was tried with secondary school teachers participating in professional development workshops and with students at a technical college; the teachers and students responded enthusiastically to the material. 相似文献
993.
Yoshihiro Hamaya 《Journal of Difference Equations and Applications》2013,19(9):805-817
We introduce the concept of the second Liapunov differences in difference equations and show that, in the autonomous case, the second variations can guarantee the existence of solutions tending to zero while others starting arbitrarily near 0 go to ∞. These are based on Yorke's results for ordinary differential equations. 相似文献
994.
Magdy H. Metry Allan R. Sampson 《Journal of computational and graphical statistics》2013,22(2):209-223
Abstract This article introduces an approach for characterizing the classes of empirical distributions that satisfy certain positive dependence notions. Mathematically, this can be expressed as studying certain subsets of the class SN of permutations of 1, …, N, where each subset corresponds to some positive dependence notions. Explicit techniques for it-eratively characterizing subsets of SN that satisfy certain positive dependence concepts are obtained and various counting formulas are given. Based on these techniques, graph-theoretic methods are used to introduce new and more efficient algorithms for constructively generating and enumerating the elements of various of these subsets of SN. For example, the class of positively quadrant dependent permutations in SN is characterized in this fashion. 相似文献
995.
给出了随机变量变换分布的三个推论,这些推论提供了在不同变换下求二维随机变量的函数的概率密度的计算公式,实例应用表明,这些公式应用简便,灵活,实用. 相似文献
996.
《Optimization》2012,61(2):305-319
The scalarization functions were used in vector optimization for a long period. Similar functions were introduced and used in economics under the name of shortage function or in mathematical finance under the name of (convex or coherent) measures of risk. The main aim of this article is to study Lipschitz continuity properties of such functions and to give some applications for deriving necessary optimality conditions for vector optimization problems using the Mordukhovich subdifferential. 相似文献
997.
998.
In the present investigation we define a new class of meromorphic functions on the punctured unit disk △*:= {z ∈ C : 0 < |z| < 1} by making use of the generalized Dziok-Srivastava operator H l m [α1 ]. Coefficient inequalities, growth and distortion inequalities, as well as closure results are obtained. We also establish some results concerning the partial sums of meromorphic functions and neighborhood results for functions in new class. 相似文献
999.
《Optimization》2012,61(8):1009-1028
Bilevel convex models are studied after being cast into a parametric programming form. This form has a lexicographic inner-outer structure where the optimal value of the outer model is optimized on the set of optimal solutions of the inner model. Optimal solutions are characterized using a Lagrangian saddle-point approach and a marginal value formula is given for the outer model. These are used to formulate a general method for finding an optimal solution by input optimization. 相似文献
1000.