全文获取类型
收费全文 | 520篇 |
免费 | 11篇 |
专业分类
化学 | 209篇 |
力学 | 9篇 |
数学 | 76篇 |
物理学 | 237篇 |
出版年
2022年 | 5篇 |
2020年 | 5篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 22篇 |
2012年 | 21篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 27篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1967年 | 6篇 |
1932年 | 3篇 |
1928年 | 3篇 |
1916年 | 4篇 |
排序方式: 共有531条查询结果,搜索用时 0 毫秒
101.
Hardy F Hillier NJ Meingast C Colson D Li Y Barišić N Yu G Zhao X Greven M Schilling JS 《Physical review letters》2010,105(16):167002
It is well known that the superconducting transition temperature (T(c)) of cuprate superconductors can be enhanced by varying certain structural and electronic parameters, such as the flatness of the CuO? planes or their doping level. We determine the uniaxial and hydrostatic pressure derivatives of T(c) in the structurally simple tetragonal compound HgBa?CuO(4+δ) near optimal doping. Our results provide experimental evidence for two further methods to enhance T(c): (i) reducing the area of the CuO? planes, and (ii) increasing the separation of the CuO? planar groups. T(c) is found to couple much more strongly to the ratio c/a of the lattice constants than to the unit cell volume. A comparison with prior results for structurally more complicated cuprates reveals a general trend of uniaxial pressure derivatives with T(c). 相似文献
102.
J. R. Hardy 《Phase Transitions》2013,86(3):521-537
An overview is presented of our studies on the nature of structural instabilities in relatively complex ionic solids. These are based on parameter-free interionic potentials based on the Gordon-Kim modified electron gas formalism extended to molecular ions. We describe the manner in which there emerge from these studies quite general concepts of “size” and “shape” as structural determinants. In particular, we discuss how these, and the approximate symmetries that they can produce, can provide a relatively simple structure-based explanation of the origins of incommensurate phases in these systems. However, we also emphasize that the existence of such symmetries does not guarantee an incommensurate phase. This can only be realized if long-range correlations are sufficiently strong to overcome random local disordering. Thus, either the molecular units are partially linked and/or there exist long-range Coulomb interactions between individual units. 相似文献
103.
In this paper we present a detailed development of our vibronic mechanism for the explanation of high temperature superconductivity. We first review the evidence for believing that some unified mechanism for “low” and “high” T c is required. We then develop the case for the existence of the double-well motions, required by our theory, in these systems, and proceed to develop our ideas further to the point of unifying, the T c ~ 100 K, and the T c ~ 40 K systems. We also advance a possible explanation of the anomalous isotope effects in these systems, and conclude with an extended discussion of non-cuprate systems and general criteria for high T c theories, including the gap to kT c ratio. 相似文献
104.
Jaudet C Vignolles D Audouard A Levallois J LeBoeuf D Doiron-Leyraud N Vignolle B Nardone M Zitouni A Liang R Bonn DA Hardy WN Taillefer L Proust C 《Physical review letters》2008,100(18):187005
The de Haas-van Alphen effect was observed in the underdoped cuprate YBa2Cu3O6.5 via a torque technique in pulsed magnetic fields up to 59 T. Above a field of approximately 30 T the magnetization exhibits clear quantum oscillations with a single frequency of 540 T and a cyclotron mass of 1.76 times the free electron mass, in excellent agreement with previously observed Shubnikov-de Haas oscillations. The oscillations obey the standard Lifshitz-Kosevich formula of Fermi-liquid theory. This thermodynamic observation of quantum oscillations confirms the existence of a well-defined, closed, and coherent, Fermi surface in the pseudogap phase of cuprates. 相似文献
105.
Xia J Schemm E Deutscher G Kivelson SA Bonn DA Hardy WN Liang R Siemons W Koster G Fejer MM Kapitulnik A 《Physical review letters》2008,100(12):127002
The polar Kerr effect in the high-T_(c) superconductor YBa2Cu3O6+x was measured at zero magnetic field with high precision using a cyogenic Sagnac fiber interferometer. We observed nonzero Kerr rotations of order approximately 1 microrad appearing near the pseudogap temperature T(*) and marking what appears to be a true phase transition. Anomalous magnetic behavior in magnetic-field training of the effect suggests that time reversal symmetry is already broken above room temperature. 相似文献
106.
W. B. Hardy 《Colloid and polymer science》1928,46(4):268-277
Ohne ZusammenfassungUebersetzt von W. Haller (Leipzig). 相似文献
107.
M. Belhadi O. Rafil R. Tigrine A. Khater J. Hardy A. Virlouvet K. Maschke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):435-443
The influence of linear defect boundaries on the transmission and scattering of elastic waves in quasi-two-dimensional wave-guides
is studied using the matching method. A linear defect boundary separating two wave-guide crystalline lattice domains is characterised
here by a linear chain of defect masses and by modified elastic constants in the boundary, different from their values in
the bulk of the domains. In particular a square lattice is considered to model the domains of the two-dimensional planar wave-guide
containing the linear defect. The reflection and transmission probabilities, and the total transmission probabilities are
calculated numerically and presented for the scattering processes in a variety of cases. We show that the interaction between
the localised modes introduced by the defect boundary and the propagating modes of the system leads to Fano resonances. These
resonances shift to higher (lower) frequencies for smaller (larger) defect masses, and for the same mass as function of the
angle of the incident wave. Other spectral features shown to exist are due to interference effects especially at oblique incidence
and when modifying the boundary elastic constants.
Received 8 November 1999 and Received in final form 14 January 2000 相似文献
108.
Summary In 1963, Zaretskiį established a one-to-one correspondence between the setB
X of binary relations on a set X and the set of triples of the form (W, ϕ, V) where W and V are certain lattices and ϕ: W→V
is an isomorphism. We provide a multiplication for these triples making the Zaretskiį correspondence a semigroup isomorphism.
In addition, we consider faithful representations ofB
X by pairs of partial transformations and also as the translational hull of its rectangular relations. Using these triples,
we study idempotents, regular and completely regular elements and relationsH-equivalent to some relations with familiar properties such as reflexivity, transitivity, etc.
Entrata in Redazione il 14 aprile 1998. 相似文献
109.
Presented here is a new approach for analysis of the so-called holey photonic crystals—a class of electro-optical components, in which periodicity of air holes in dielectric media is used for confinement of light. This class includes several kinds of microstructured fibers, semiconductor lasers etc. Accurate evaluation of optical characteristics of those devices is usually a complicated problem due to the large dimensions and the fine structure of their refractive index distribution. Furthermore, usually, only numerical solutions for this class of optical components are available. The overwhelming majority of the physical models, suitable for analysis of holey photonic devices, proceed from the “natural” assumption: the devices are considered as arrays of air holes, surrounded by dielectric material. In this work we propose another model. Namely, we treat them as arrays of dielectric spots (waveguides), embedded in the air (cladding material). This model allows utilization of the extended coupled-mode theory (a relatively new approach designed for analysis of infinite arrays of coupled waveguides and previously considered inapplicable to holey optical components) for calculations of the latter. In this sense, we present a new method for analysis of holey photonic crystals. On the one hand, our method allows analytical evaluation of some optical characteristics of holey optical components (such as the number of photonic bands and bandwidth). On the other hand, accurate numerical computation of the photonic band structure of the holey photonic devices, incorporating a large number of holes, can be done with this technique on a timescale of several minutes. 相似文献
110.
A. Hardy C. Adelmann H. Van den Rul M.K. Van Bael S. De Gendt M. D’Olieslaeger M. Heyns J.A. Kittl 《Applied Surface Science》2009,255(17):7812-7817
Grazing angle attenuated total reflectance Fourier transform infrared spectroscopy is applied to study ultrathin film Hf4+, Sc3+ and Dy3+oxides, due to its high surface sensitivity. The (multi)metal oxides studied, are of interest as high-k dielectrics. Important properties affecting the permittivity, such as the amorphous or crystalline phase and interfacial reactions, are characterized.Dy2O3 is prone to silicate formation on SiO2/Si substrates, which is expressed in DyScO3 as well, but suppressed in HfDyOx. Sc2O3, HfScOx and HfO2 were found to be stable in contact with SiO2/Si. Deposition of HfO2 in between Dy2O3 or DyScO3 and SiO2, prevents silicate formation, showing a buffer-like behavior for the HfO2.Doping of HfO2 with Dy or Sc prevents monoclinic phase crystallization. Instead, a cubic phase is obtained, which allows a higher permittivity of the films. The phase remains stable after anneal at high temperature. 相似文献