全文获取类型
收费全文 | 2544篇 |
免费 | 368篇 |
国内免费 | 309篇 |
专业分类
化学 | 316篇 |
晶体学 | 14篇 |
力学 | 131篇 |
综合类 | 82篇 |
数学 | 2078篇 |
物理学 | 600篇 |
出版年
2024年 | 3篇 |
2023年 | 37篇 |
2022年 | 33篇 |
2021年 | 50篇 |
2020年 | 81篇 |
2019年 | 65篇 |
2018年 | 100篇 |
2017年 | 104篇 |
2016年 | 105篇 |
2015年 | 81篇 |
2014年 | 115篇 |
2013年 | 188篇 |
2012年 | 133篇 |
2011年 | 123篇 |
2010年 | 111篇 |
2009年 | 123篇 |
2008年 | 154篇 |
2007年 | 154篇 |
2006年 | 139篇 |
2005年 | 141篇 |
2004年 | 117篇 |
2003年 | 129篇 |
2002年 | 126篇 |
2001年 | 132篇 |
2000年 | 111篇 |
1999年 | 86篇 |
1998年 | 62篇 |
1997年 | 53篇 |
1996年 | 72篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1974年 | 4篇 |
排序方式: 共有3221条查询结果,搜索用时 15 毫秒
1.
It is well known that S 12 cannot prove the injective weak pigeonhole principle for polynomial time functions unless RSA is insecure. In this note we investigate the provability of the surjective (dual) weak pigeonhole principle in S 12 for provably weaker function classes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
For each infinite cardinal κ, we give examples of 2κ many non‐isomorphic vertex‐transitive graphs of order κ that are pairwise isomorphic to induced subgraphs of each other. We consider examples of graphs with these properties that are also universal, in the sense that they embed all graphs with smaller orders as induced subgraphs. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 99–106, 2003 相似文献
3.
The transition from the quantum to the classical world is not yet understood. Here, we take a new approach. Central to this is the understanding that measurement and actualization cannot occur except on some specific basis. However, we have no established theory for the emergence of a specific basis. Our framework entails the following: (i) Sets of N entangled quantum variables can mutually actualize one another. (ii) Such actualization must occur in only one of the 2N possible bases. (iii) Mutual actualization progressively breaks symmetry among the 2N bases. (iv) An emerging “amplitude” for any basis can be amplified by further measurements in that basis, and it can decay between measurements. (v) The emergence of any basis is driven by mutual measurements among the N variables and decoherence with the environment. Quantum Zeno interactions among the N variables mediates the mutual measurements. (vi) As the number of variables, N, increases, the number of Quantum Zeno mediated measurements among the N variables increases. We note that decoherence alone does not yield a specific basis. (vii) Quantum ordered, quantum critical, and quantum chaotic peptides that decohere at nanosecond versus femtosecond time scales can be used as test objects. (viii) By varying the number of amino acids, N, and the use of quantum ordered, critical, or chaotic peptides, the ratio of decoherence to Quantum Zeno effects can be tuned. This enables new means to probe the emergence of one among a set of initially entangled bases via weak measurements after preparing the system in a mixed basis condition. (ix) Use of the three stable isotopes of carbon, oxygen, and nitrogen and the five stable isotopes of sulfur allows any ten atoms in the test protein to be discriminably labeled and the basis of emergence for those labeled atoms can be detected by weak measurements. We present an initial mathematical framework for this theory, and we propose experiments. 相似文献
4.
《Analytical letters》2012,45(5):261-265
Abstract An oscillometric titration technique has been applied to the determination of ß-diketones. Typical accuracies of about ± 1.5% were obtained for the compounds studied. The technique is rapid and simple, and should be suitable to the serial analyses of many compounds of pharmaceutical interest. 相似文献
5.
Separation theorems for an arbitrary set and a not necessarily convex set in a linear topological space are proved and applied to vector optimization. Scalarization results for weakly efficient points and properly efficient points are deduced. 相似文献
6.
利用有效场理论研究了纳米管上最近邻弱交换相互作用下spin-1纳米管中Blume-Capel模型的内能、比热和自由能,得到了系统的内能、比热和自由能与最近邻弱交换相互作用和晶场的关系。结果表明:最近邻弱交换相互作用和晶场强度等诸多因素相互竞争,使系统表现出比 = = =1时的BC模型更为复杂的热学性质;系统内能随温度的变化曲线表现出不连续性;比热随温度的变化出现奇异性;高温对自由能的影响更加明显。 相似文献
7.
Periodica Mathematica Hungarica - Let X 1,X 2,... be a sequence of independent and identically distributed random variables, and put % MATHTYPE!MTEF!2!1!+-%... 相似文献
8.
We discuss the notion of weak transversality and clarify its role in the context of Lie group theory with several examples. In particular, we present some new results concerning models of fluid dynamics. 相似文献
9.
F. Berthelin F. Bouchut 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2003,20(6):189-997
We consider isentropic gas dynamics equations with unilateral constraint on the density and mass loss. The γ and pressureless pressure laws are considered. We propose an entropy weak formulation of the system that incorporates the constraint and Lagrange multiplier, for which we prove weak stability and existence of solutions. The nonzero pressure model is approximated by a kinetic BGK relaxation model, while the pressureless model is approximated by a sticky-blocks dynamics with mass loss. 相似文献
10.
In the context of the weak solutions of the Navier-Stokes equations we study the regularity of the pressure and its derivatives in the space-time neighbourhood of regular points. We present some global and local conditions under which the regularity is further improved. 相似文献