全文获取类型
收费全文 | 3064篇 |
免费 | 43篇 |
国内免费 | 33篇 |
专业分类
化学 | 1758篇 |
晶体学 | 60篇 |
力学 | 67篇 |
数学 | 668篇 |
物理学 | 587篇 |
出版年
2022年 | 49篇 |
2021年 | 64篇 |
2020年 | 30篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 56篇 |
2016年 | 79篇 |
2015年 | 76篇 |
2014年 | 86篇 |
2013年 | 210篇 |
2012年 | 134篇 |
2011年 | 179篇 |
2010年 | 114篇 |
2009年 | 125篇 |
2008年 | 171篇 |
2007年 | 161篇 |
2006年 | 148篇 |
2005年 | 124篇 |
2004年 | 142篇 |
2003年 | 99篇 |
2002年 | 105篇 |
2001年 | 52篇 |
2000年 | 43篇 |
1999年 | 43篇 |
1998年 | 40篇 |
1997年 | 51篇 |
1996年 | 55篇 |
1995年 | 31篇 |
1994年 | 34篇 |
1993年 | 41篇 |
1992年 | 27篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 31篇 |
1988年 | 20篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 30篇 |
1984年 | 41篇 |
1983年 | 24篇 |
1982年 | 24篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 29篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1974年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有3140条查询结果,搜索用时 15 毫秒
191.
It is shown that in every dimension n = 3j + 2, j = 1, 2, 3, . . ., there exist compact pseudo-Riemannian manifolds with parallel Weyl tensor, which are Ricci-recurrent, but
neither conformally flat nor locally symmetric, and represent all indefinite metric signatures. The manifolds in question
are diffeomorphic to nontrivial torus bundles over the circle. They all arise from a construction that a priori yields bundles
over the circle, having as the fibre either a torus, or a 2-step nilmanifold with a complete flat torsionfree connection;
our argument only realizes the torus case. 相似文献
192.
Andrzej Schinzel 《Journal of Number Theory》2010,130(7):1572-1580
The concept of k-admissible tracks in Shamir's secret sharing scheme over a finite field was introduced by Schinzel et al. (2009) [10]. Using some estimates for the elementary symmetric polynomials, we show that the track (1,…,n) over Fp is practically always k-admissible; i.e., the scheme allows to place the secret as an arbitrary coefficient of its generic polynomial even for relatively small p. Here k is the threshold and n the number of shareholders. 相似文献
193.
Syariza Abdul-Rahman Edmund K. Burke Andrzej Bargiela Barry McCollum Ender Özcan 《Annals of Operations Research》2014,218(1):3-21
In this study, we investigate an adaptive decomposition and ordering strategy that automatically divides examinations into difficult and easy sets for constructing an examination timetable. The examinations in the difficult set are considered to be hard to place and hence are listed before the ones in the easy set in the construction process. Moreover, the examinations within each set are ordered using different strategies based on graph colouring heuristics. Initially, the examinations are placed into the easy set. During the construction process, examinations that cannot be scheduled are identified as the ones causing infeasibility and are moved forward in the difficult set to ensure earlier assignment in subsequent attempts. On the other hand, the examinations that can be scheduled remain in the easy set. Within the easy set, a new subset called the boundary set is introduced to accommodate shuffling strategies to change the given ordering of examinations. The proposed approach, which incorporates different ordering and shuffling strategies, is explored on the Carter benchmark problems. The empirical results show that the performance of our algorithm is broadly comparable to existing constructive approaches. 相似文献
194.
Anna Jaśkiewicz Janusz Matkowski Andrzej S. Nowak 《Annals of Operations Research》2014,220(1):263-278
This paper generalizes the classical discounted utility model introduced in Samuelson (Rev. Econ. Stud. 4:155–161, 1937) by replacing a constant discount rate with a function. The existence of recursive utilities and their constructions are based on Matkowski’s extension of the Banach Contraction Principle. The derived utilities go beyond the class of recursive utilities studied in the literature and enable a discussion on subtle issues concerning time preferences in the theory of finance, economics or psychology. Moreover, our main results are applied to the theory of optimal economic growth related with resource extraction models with unbounded utility function of consumption. 相似文献
195.
196.
197.
We use an idea of countable separability of points and sets in topological spaces to prove results on intersection of measurable
multifunctions and an implicit function theorem. We generalize or extend in part some well known Himmelberg's theorems. 相似文献
198.
A planar ordered set has a triangle-free, planar covering graph; on the other hand, there are nonplanar ordered sets whose covering graphs are planar. We show thatevery triangle-free planar graph has a planar upward drawing. This planar upward drawing can be constructed in time, polynomial in the number of vertices.Our results shed light on the apparently difficult problem, of long-standing, whether there is aneffective planarity-testing procedure for an ordered set.Supported in part by the Alexander von Humboldt Stiftung.Supported in part by the Deutsche Forschungsgemeinschaft. 相似文献
199.
We show that it is consistent with MA + ?CH that the Forcing Axiom fails for all forcing notions in the class of ωω–bounding forcing notions with norms of [17].
Received: 28 April 1999 / Published online: 12 December 2001 相似文献
200.
Robert Jensen Maciej Kocan Andrzej Swiech 《Proceedings of the American Mathematical Society》2002,130(2):533-542
We introduce the notion of a ``good" solution of a fully nonlinear uniformly elliptic equation. It is proven that ``good" solutions are equivalent to -viscosity solutions of such equations. The main contribution of the paper is an explicit construction of elliptic equations with strong solutions that approximate any given fully nonlinear uniformly elliptic equation and its -viscosity solution. The results also extend some results about ``good" solutions of linear equations.