全文获取类型
收费全文 | 12036篇 |
免费 | 157篇 |
国内免费 | 89篇 |
专业分类
化学 | 4674篇 |
晶体学 | 14篇 |
力学 | 696篇 |
综合类 | 7篇 |
数学 | 4351篇 |
物理学 | 2540篇 |
出版年
2024年 | 80篇 |
2023年 | 691篇 |
2022年 | 417篇 |
2021年 | 427篇 |
2020年 | 1472篇 |
2019年 | 1087篇 |
2018年 | 940篇 |
2017年 | 765篇 |
2016年 | 751篇 |
2015年 | 581篇 |
2014年 | 762篇 |
2013年 | 2874篇 |
2012年 | 535篇 |
2011年 | 65篇 |
2010年 | 68篇 |
2009年 | 52篇 |
2008年 | 78篇 |
2007年 | 69篇 |
2006年 | 57篇 |
2005年 | 109篇 |
2004年 | 109篇 |
2003年 | 56篇 |
2002年 | 35篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1969年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Anastassia N. Rissanou Spiros H. Anastasiadis Ioannis A. Bitsanis 《Journal of polymer science. Part A, Polymer chemistry》2009,47(24):2462-2476
When a polymer chain in solution interacts with an atomically smooth solid substrate, its conformational properties are strongly modified and deviate substantially from those of chains in bulk. In this work, the interplay of two competing transitions that affect the conformations of polymer chains near an energetically attractive surface is studied by means of Monte Carlo simulations on a cubic lattice. The transition from an extended to a compact conformation of a polymer chain near an attractive wall, as solubility deteriorates, exhibits characteristics akin to the “coil-to-globule” transition in bulk. An effective θ-temperature is determined. Its role as the transition point is confirmed in a variety of ways. The nature of the coil-to-compact transition is not qualitatively different from that in the bulk. Adsorbed polymer chains may assume “globular” or “pancake” configurations depending on the competition among adsorption strength, cohesive energy, and entropy. In a very relevant range of conditions, the dependence of the adsorbate thickness on chain-length is intermediate between that of 3-d (“semidroplets”) and 2-d (“pancake”) objects. The focus of this study is on rather long polymer chains. Several crucial features of the transitions of the adsorbed chains are N-dependent and various aspects of the adsorption and “dissolution” process are manifested clearly only at the “long chain” limit. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2462–2476, 2009 相似文献
962.
YANG Guo-Hui ZHOU Ling 《理论物理通讯》2008,49(6):1635-1638
The thermal entanglement of a three-qubit Heisenberg chain under a nonuniform magnetic field is studied. It is very interesting to note that the next nearest neighbor entanglement (NNNE) could be larger than the nearest neighbor entanglement (NNE). We analyze the ground state entanglement, and give the conditions that NNNE is larger than NNE near zero temperature. Our results also show that the nonuniform field could induce the entanglement and improve the threshold temperature at certain parameter region. 相似文献
963.
Fabienne Jézéquel 《Comptes Rendus Mecanique》2006,334(6):362-367
The numerical result provided by an approximation method is affected by a global error, which consists of both a truncation error and a round-off error. Let us consider the converging sequence generated by successively dividing by two the step size used. If computations are performed until, in the convergence zone, the difference between two successive approximations is only due to round-off errors, then the global error on the result obtained is minimal. Furthermore its significant bits which are not affected by round-off errors are in common with the exact result, up to one. To cite this article: F. Jézéquel, C. R. Mecanique 334 (2006). 相似文献
964.
We discuss deformations of the classical systems in the phase space and show that one can use non-canonical transformations to relate regular and deformed models. On the other hand some of the models can be obtained as a classical limit of the deformed quantum models, i.e. as the result of the dequantization procedure. Nonrelativistic deformations are described. 相似文献
965.
Jamila Douari 《International Journal of Theoretical Physics》2006,45(5):867-879
We construct a deformed C
λ-extended Heisenberg algebra in two-dimensional space using noncommuting coordinates which close an algebra depends on statistical parameter characterizing exotic particles. The obtained symmetry is nothing but an exotic particles algebra interpolating between bosonic and deformed fermionic algebras.
PACS numbers: 03.65.Fd, 02.40.Gh, 05.30.Pr 相似文献
966.
Paolo Corradini 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):391-395
This article recalls some aspects of the fascinating history of the discovery by Giulio Natta and his research group of the stereoselective polymerization of propylene and the understanding of the relationships between structure and properties of semicrystalline polymers. The impact of the discovery of isotactic polypropylene and stereoregular polymers on pure and applied science is briefly outlined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 391–395, 2004 相似文献
967.
Karin Melnick 《Geometriae Dedicata》2007,126(1):131-154
We prove results toward classifying compact Lorentz manifolds on which Heisenberg groups act isometrically. We give a general
construction, leading to a new example, of codimension-one actions – those for which the dimension of the Heisenberg group
is one less than the dimension of the manifold. The main result is a classification of codimension-one actions, under the
assumption they are real-analytic. 相似文献
968.
In the paper we introduce stopping times for quantum Markov states. We study algebras and maps corresponding to stopping times, give a condition of strong Markov property and give classification of projections for the property of accessibility. Our main result is a new recurrence criterium in terms of stopping times (Theorem 1 and Corollary 2). As an application of the criterium we study how, in Section 6, the quantum Markov chain associated with the one-dimensional Heisenberg (usually non-Markovian) process, obtained from this quantum Markov chain by restriction to a diagonal subalgebra, is such that all its states are recurrent. We were not able to obtain this result from the known recurrence criteria of classical probability.Supported by GNAFA-CNR, Bando n. 211.01.25. 相似文献
969.
The convective instability of a horizontal liquid layer confined in an annular Hele–Shaw cell subject to a constant rotation and submitted to a centrifugal gradient of temperature is investigated. Using a linear stability analysis, we study the effects of both Coriolis forces and curvature aspect on the stationary convective threshold when the Prandtl number is of the order of unity or larger than unity. We show that the Coriolis forces have a stabilizing effect, and the wave number is independent of these forces. However, a multicellular regime in the radial direction is observed for small Ekman numbers. The results related to the influence of the curvature are also shown. To cite this article: S. Ramezani et al., C. R. Mecanique 330 (2002) 633–640. 相似文献
970.
We propose a kind of explicit sympletic Runge-Kutta-like scheme to solve operator equations of motion in quantum mechanics and in a quantum scalar field theory. 相似文献