全文获取类型
收费全文 | 99篇 |
免费 | 1篇 |
专业分类
化学 | 26篇 |
力学 | 7篇 |
数学 | 14篇 |
物理学 | 53篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 0 毫秒
41.
42.
ac Conductivity measurements are carried out across the metal to insulator transition in NiAl0.7Cr0.7Fe0.6O4. The low frequency data is analyzed using Summerfield scaling theory for hopping conductivity. The exponent of the scaling
behavior has significantly different values in the conducting and insulating regimes. The hopping frequency and the zero frequency
conductivity are found to increase with temperature, slowly in the metallic regime and rapidly in the insulating regime. 相似文献
43.
Open- and closed-loop aberration correction by use of a quadrature interferometric wave-front sensor
Baker KL Stappaerts EA Wilks SC Young PE Gavel DT Tucker JW Silva DA Olivier SS 《Optics letters》2004,29(1):47-49
Experimental results are presented for an adaptive optics system based on a quadrature Twyman-Green interferometric wave-front sensor. The system uses a circularly polarized reference beam to form two interferograms with a pi/2 phase shift. The experiments conducted used Kolmogorov phase screens to simulate atmospheric phase distortions. Strehl ratio improvements by a factor of 8, to an absolute value of 0.45, are demonstrated. 相似文献
44.
45.
Caignan GA Deshmukh R Zeng Y Wilks A Bunce RA Rivera M 《Journal of the American Chemical Society》2003,125(39):11842-11852
13C NMR spectroscopic studies have been conducted with the hydroxide complex of Pseudomonas aeruginosa heme oxygenase (Fe(III)-OH), where OH(-) has been used as a model of the OOH(-) ligand to gain insights regarding the elusive ferric hydroperoxide (Fe(III)-OOH) intermediate in heme catabolism at ambient temperatures. Analysis of the heme core carbon resonances revealed that the coordination of hydroxide in the distal site of the enzyme results in the formation of at least three populations of Fe(III)-OH complexes with distinct electronic configurations and nonplanar ring distortions that are in slow exchange relative to the NMR time scale. The most abundant population exhibits a spin crossover between S = (1)/(2) and S = (3)/(2) spin states, and the two less abundant populations exhibit pure, S = (3)/(2) and S = (1)/(2), (d(xy)())(1) electronic configurations. We propose that the highly organized network of water molecules in the distal pocket of heme oxygenase, by virtue of donating a hydrogen bond to the coordinated hydroxide ligand, lowers its ligand field strength, thereby increasing the field strength of the porphyrin (equatorial) ligand, which results in nonplanar deformations of the macrocycle. This tendency to deform from planarity, which is imparted by the ligand field strength of the coordinated OH(-), is likely reinforced by the flexibility of the distal pocket in HO. These findings suggest that if the ligand field strength of the coordinated OOH(-) in heme oxygenase is modulated in a similar manner, the resultant large spin density at the meso carbons and nonplanar deformations of the pophyrin ring prime the macrocycle to actively participate in its own hydroxylation. 相似文献
46.
P. CsöRGő A. Drápal 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2006,76(1):17-34
A loopQ is said to be left conjugacy closed (LCC) if the left translations form a set of permutations that is closed under conjugation. This papers investigates those LCC loops where the group generated by left translations is normal in the group generated by both left and right translations. 相似文献
47.
G. Wilks 《Applied Scientific Research》1974,29(1):121-129
A uniform transverse magnetic field acts across an infinite flat plate immersed in a conducting fluid of arbitrary magnetic Prandtl number. The skin friction on the plate for the class of accelerated motions Ut
k is discussed for a), a perfect conductor and b), an insulator. Residual stresses are demonstrated in both instances. 相似文献
48.
Ronald L. Graham Jeffrey C. Lagarias Colin L. Mallows Allan R. Wilks Catherine H. Yan 《Discrete and Computational Geometry》2006,35(1):1-36
Apollonian circle packings arise by repeatedly filling the interstices
between four mutually tangent circles with further tangent circles.
Such packings can be described in terms of the Descartes configurations
they contain, where a Descartes configuration is a set of four mutually tangent
circles in the Riemann sphere, having disjoint interiors.
Part I showed there exists a discrete group, the Apollonian group,
acting on a parameter space of (ordered, oriented) Descartes configurations,
such that the Descartes configurations in a packing formed an
orbit under the action of this group. It is observed there
exist infinitely many types of integral Apollonian packings in which all circles had integer curvatures, with the integral
structure being related to the integral nature of the Apollonian group. Here we consider the action of a larger discrete group,
the super-Apollonian group, also having an integral structure, whose orbits describe the Descartes quadruples of a geometric
object we call a super-packing. The circles in a super-packing never cross each other but are nested to an arbitrary depth.
Certain Apollonian packings and super-packings are strongly integral in the sense that the curvatures of all circles are integral
and the curvature x centers of all circles are integral. We show that (up to scale) there are exactly eight different (geometric)
strongly integral super-packings, and that each contains a copy of every integral Apollonian circle packing (also up to scale).
We show that the super-Apollonian group has finite volume in the group of all automorphisms of the parameter space of Descartes
configurations, which is isomorphic
to the Lorentz group O(3, 1). 相似文献
49.
Cross-sectional scanning tunneling microscopy and spectroscopy have been used to probe the unreconstructed (1 1 0) surface of a commercially available buried heterostructure laser in ultra high vacuum. Complex re-growth above the non-linear blocking layers is shown to induce tensile strain in the device. Spectroscopic measurements show an increase in both the density of filled valence band states and empty conduction band states as a result of the strain, with a particularly large increase at −3.1 V. Current imaging tunneling spectroscopy measurements show an increase in the tunneling current in to and out of the strained regions at both gap voltage polarities, consistent with the spectroscopy. Moving towards tensile strain, InP is known to maintain much the same bandgap, with the split-off level and lower lying states being drawn up towards the valence band edge, consistent with the data. 相似文献
50.
Energy relaxation of the hot electron population generated by relativistic laser pulses in overdense plasma is analyzed for densities ranging from below to 1000 times solid density. It is predicted that longitudinal beam-plasma instabilities, which dominate energy transfer between hot electrons and plasma at lower densities, are suppressed by collisions beyond solid density. The respective roles of collisional energy transfer modes, i.e., direct collisions, diffusion, and resistive return current heating, are identified with respect to plasma density. The transition between the kinetic and the collisional regimes and scalings of collisional process are demonstrated by a fully integrated one-dimensional collisional particle simulation. 相似文献