全文获取类型
收费全文 | 339530篇 |
免费 | 4919篇 |
国内免费 | 1701篇 |
专业分类
化学 | 172689篇 |
晶体学 | 3840篇 |
力学 | 16173篇 |
综合类 | 62篇 |
数学 | 63941篇 |
物理学 | 89445篇 |
出版年
2020年 | 2483篇 |
2019年 | 2564篇 |
2018年 | 13258篇 |
2017年 | 13094篇 |
2016年 | 11181篇 |
2015年 | 4614篇 |
2014年 | 5238篇 |
2013年 | 12341篇 |
2012年 | 14069篇 |
2011年 | 21789篇 |
2010年 | 13622篇 |
2009年 | 13533篇 |
2008年 | 17332篇 |
2007年 | 19266篇 |
2006年 | 10656篇 |
2005年 | 10882篇 |
2004年 | 10003篇 |
2003年 | 9352篇 |
2002年 | 8220篇 |
2001年 | 7814篇 |
2000年 | 6200篇 |
1999年 | 4451篇 |
1998年 | 3743篇 |
1997年 | 3578篇 |
1996年 | 3787篇 |
1995年 | 3167篇 |
1994年 | 3298篇 |
1993年 | 3136篇 |
1992年 | 3393篇 |
1991年 | 3374篇 |
1990年 | 3204篇 |
1989年 | 3042篇 |
1988年 | 2933篇 |
1987年 | 2851篇 |
1986年 | 2842篇 |
1985年 | 3746篇 |
1984年 | 3782篇 |
1983年 | 3126篇 |
1982年 | 3363篇 |
1981年 | 3159篇 |
1980年 | 2916篇 |
1979年 | 3077篇 |
1978年 | 3274篇 |
1977年 | 3304篇 |
1976年 | 3335篇 |
1975年 | 3038篇 |
1974年 | 3141篇 |
1973年 | 3221篇 |
1972年 | 2449篇 |
1971年 | 1951篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
What features characterize complex system dynamics? Power laws and scale invariance of fluctuations are often taken as the hallmarks of complexity, drawing on analogies with equilibrium critical phenomena. Here we argue that slow, directed dynamics, during which the system's properties change significantly, is fundamental. The underlying dynamics is related to a slow, decelerating but spasmodic release of an intrinsic strain or tension. Time series of a number of appropriate observables can be analyzed to confirm this effect. The strain arises from local frustration. As the strain is released through “quakes,” some system variable undergoes record statistics with accompanying log‐Poisson statistics for the quake event times. We demonstrate these phenomena via two very different systems: a model of magnetic relaxation in type II superconductors and the Tangled Nature model of evolutionary ecology and show how quantitative indications of aging can be found. © 2004 Wiley Periodicals, Inc. Complexity 10: 49–56, 2004 相似文献
995.
996.
This article provides a status report on discrete mathematics in America's schools, including an overview of publications
and programs that have had major impact. It discusses why discrete mathematics should be introduced in the schools and the
authors' efforts to advocate, facilitate, and support the adoption of discrete mathematics topics in the schools. Their perspective
is that discrete mathematics should be viewed not only as a collection of new and interesting mathematical topics, but, more
importantly, as a vehicle for providing teachers with a new way to think about traditional mathematical topics and new strategies
for engaging their students in the study of mathematics. 相似文献
997.
A classification of homogeneous quaternionic Kähler structures by real tensors is given and related to Fino's representation theoretic decomposition. A relationship between the modules whose dimension grows linearly and quaternionic hyperbolic space is found. To cite this article: M. Castrillón López et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
998.
Yuri L. Sachkov 《Transactions of the American Mathematical Society》2004,356(2):457-494
Flat sub-Riemannian structures are local approximations -- nilpotentizations -- of sub-Riemannian structures at regular points. Lie algebras of symmetries of flat maximal growth distributions and sub-Riemannian structures of rank two are computed in dimensions 3, 4, and 5.
999.
José L. Ló pez Nico M. Temme 《Transactions of the American Mathematical Society》2004,356(11):4323-4342
Taylor expansions of analytic functions are considered with respect to several points, allowing confluence of any of them. Cauchy-type formulas are given for coefficients and remainders in the expansions, and the regions of convergence are indicated. It is explained how these expansions can be used in deriving uniform asymptotic expansions of integrals. The method is also used for obtaining Laurent expansions in several points as well as Taylor-Laurent expansions.
1000.
It is suggested that the question of existence of a jamming phase transition in a broad class of single-lane cellular-automaton traffic models may be studied using a correspondence to the asymmetric chipping model. In models where such correspondence is applicable, jamming phase transition does not take place. Rather, the system exhibits a smooth crossover between free-flow and jammed states, as the car density is increased. 相似文献