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41.
This paper defines a remarkable Lie algebra of infinite dimension and rank, and conjectures that it may be related to the Fischer-Griess Monster group. 相似文献
42.
An anti-Hadamard matrix may be loosely defined as a real (0, 1) matrix which is invertible, but only just. Let A be an invertible (0, 1) matrix with eigenvalues λi, singular values σi, and inverse B = (bij). We are interested in the four closely related problems of finding λ(n) = minA, i|λi|, σ(n) = minA, iσi, χ(n) = maxA, i, j |bij|, and μ(n) = maxAΣijb2ij. Then A is an anti-Hadamard matrix if it attains μ(n). We show that λ(n), σ(n) are between and c√n (2.274)?n, where c is a constant, , and . We also consider these problems when A is restricted to be a Toeplitz, triangular, circulant, or (+1, ?1) matrix. Besides the obvious application—to finding the most ill-conditioned (0, 1) matrices—there are connections with weighing designs, number theory, and geometry. 相似文献
43.
Suppose G is a finite group of complex n × n matrices, and let RG be the ring of invariants of G: i.e., those polynomials fixed by G. Many authors, from Klein to the present day, have described RG by writing it as a direct sum Σδj=1 ηj[θ1 ,…, θn]. For example, if G is a unitary group generated by reflections, δ = 1. In this note we show that in general this approach is hopeless by proving that, for any ? > 0, the smallest possible δ is greater than | G |n-1-? for almost all primitive groups. Since for any group we can choose δ ? | G |n-1, this means that most primitive groups are about as bad as they can be. The upper bound on δ follows from Dade's theorem that the θi can be chosen to have degrees dividing | G |. 相似文献
44.
How many sublattices of index N are there in the planar hexagonal lattice? Which of them are the best from the point of view of packing density, signal-to-noise ratio, or energy? We answer the first question completely and give partial answers to the other questions. 相似文献
45.
46.
Yousoon Lee Forrest T. Sloane Dr. Geneviève Blondin Dr. Khalil A. Abboud Dr. Ricardo García‐Serres Prof. Dr. Leslie J. Murray 《Angewandte Chemie (International ed. in English)》2015,54(5):1499-1503
Reaction of a trinuclear iron(II) complex, Fe3Br3 L ( 1 ), with KC8 under N2 leads to dinitrogen activation products ( 2 ) from which Fe3(NH)3 L ( 2‐1 ; L is a cyclophane bridged by three β‐diketiminate arms) was characterized by X‐ray crystallography. 1H NMR spectra of the protonolysis product of 2 synthesized under 14N2 and 15N2 confirm atmospheric N2 reduction, and ammonia is detected by the indophenol assay (yield ~30 %). IR and Mössbauer spectroscopy, and elemental analysis on 2 and 2‐1 as well as the tri(amido)triiron(II) 3 and tri(methoxo)triiron 4 congeners support our assignment of the reduction product as containing protonated N‐atom bridges. 相似文献
47.
Evidence is presented to suggest that, in three dimensions, spherical 6-designs withN points exist forN=24, 26,≥28; 7-designs forN=24, 30, 32, 34,≥36; 8-designs forN=36, 40, 42,≥44; 9-designs forN=48, 50, 52,≥54; 10-designs forN=60, 62, ≥64; 11-designs forN=70, 72,≥74; and 12-designs forN=84,≥86. The existence of some of these designs is established analytically, while others are given by very accurate numerical
coordinates. The 24-point 7-design was first found by McLaren in 1963, and—although not identified as such by McLaren—consists
of the vertices of an “improved” snub cube, obtained from Archimedes' regular snub cube (which is only a 3-design) by slightly
shrinking each square face and expanding each triangular face. 5-designs with 23 and 25 points are presented which, taken
together with earlier work of Reznick, show that 5 designs exist forN=12, 16, 18, 20,≥22. It is conjectured, albeit with decreasing confidence fort≥9, that these lists oft-designs are complete and that no other exist. One of the constructions gives a sequence of putative sphericalt-designs withN=12m points (m≥2) whereN=1/2t
2(1+o(1)) ast→∞. 相似文献
48.
49.
The structural and electronic transport properties of La1−x
Ce
x
MnO3 (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with
Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration
up to 50% doping. The system La0.5Ce0.5MnO3 also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition. 相似文献
50.