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61.
The irreversible and reversible Curie-point relaxation was studied in FeNi-based liquid-quenched glasses. An unusual diffusionless transformation was detected during low temperature ageing in liquid N2 causing a hidden structural imprint in the glassy samples. The coercive force and permeability are also modified by this transformation. 相似文献
62.
Chass GA Mirasol RS Setiadi DH Tang TH Chin W Mons M Dimicoli I Dognon JP Viskolcz B Lovas S Penke B Csizmadia IG 《The journal of physical chemistry. A》2005,109(24):5289-5302
Computational and experimental determinations were carried out in parallel on the conformational probability of N-Acetyl-Phenylalanine-NH2 (NAPA). Ab initio computations were completed at the BLYP/6-311G(df,p), B3LYP/6-31G(d), B3LYP/6-31G(d,p), and B3LYP/6-31+G(d) levels of theory, labeled L/61fp, B/6, B/6p, and B/6+, respectively. Three experimentally identified conformers were compared with theoretical data, confirming their identities as the betaLanti, gammaLgauche+, and gammaLgauche- (BACKBONESIDECHAIN) conformers. Evidence comes from matching experimental and theoretical data for all three constituent N-H stretches of NAPA, with a Delta(Experimental-Theoretical) = approximately 1-3 cm(-1), approximately 0-5 cm(-1), and approximately 1-6 cm(-1), at the L/61fp and B/6+ levels, respectively. Corrected-ZPE relative energies were computed to be 0.14, 0.00, 0.26 and 0.00, 0.67, 0.57 (kcal*mol(-1)) for the betaLanti, gammaLgauche+, and gamma(Lgauche- conformers, respectively, at the L/61fp and B/6+ levels, respectively. The MP2/6-31+G(d) level of theory was subsequently found to give similar relative energies. Characterization of the intramolecular interactions responsible for red and blue shifting of the N-H stretches showed the existence of the following intramolecular interactions: C=O[i]- - -HN[i], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-Cdelta-H- - -O=C[i-1] for betaLanti; C=O[i-1]- - -HN[i+1], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-C-H- - -O=C[i] for gammaLgauche+; and C=O[i-1]- - -HN[i+1] for gammaLgauche-. Each of these interactions were further investigated and subsequently characterized by orbital population and Atoms-In-Molecules (AIM) analyses, with the identity of overlap and bond critical points (BCP) serving as 'scoring criteria', respectively. Experimental and theoretical carbonyl stretches were also compared and showed good agreement, adding further strength to the synergy between experiment and theory. 相似文献
63.
G. Kisfaludi K. Lázár Z. Schay L. Guczi Cs. Fetzer G. Konczos A. Lovas 《Applied Surface Science》1985,24(2):225-238
Fe82.2B17.8 amorphous ribbon has been used as a catalyst for the Fischer-Tropsch-type reaction of CO+H2. Specific activity has been found to be at least an order of magnitude higher than that of either the crystallized ribbon of identical composition or the supported iron catalyst. Before and after the catalytic tests the ribbons were characterized by XRD, XPS, UPS and Mössbauer spectroscopy in transmission and in conversion electron modes. Conversion electron Mössbauer spectroscopy and UPS proved that the surface of the amorphous ribbons is being partially crystallized during 8000 min reaction time at a maximum reaction temperature of 560 K. The superior catalytic activity has been explained by stabilization of the small iron particles and Fe2O3 by boron atoms at the surface and by suppressed carbide formation. 相似文献
64.
Gy. Faigel L. Gránásy T. Kemény A. Lovas I. Vincze W. Hoving P. H. L. O. Scholte F. Van der Woude R. Hauert P. Oelhafen H. -J. Güntherodt 《Hyperfine Interactions》1986,27(1-4):381-384
57Fe Mössbauer and photoemission measurements were performed on meltquenched amorphous Fe(Zr, B) and (Fe, Ni)B alloys. The atomic and electronic structure of Fe90Zr10 and Fe88B12 glasses were found to be different. Half of the Zr content could be replaced by B in the Fe90Zr10 glass without changing its structure. Mossbauer investigation of the amorphous (Fe1?xNix)100?yBy (0<=x<=0.80, 12<=y<=40) system indicates preferential arrangement of Fe and Ni atoms on the transition metal sites. According to the present XPS measurements there is a remarkable shift of 0.5 eV to higher binding energies of the B ls core level energy in the Ni rich glasses compared to Fe88B12 corresponding to a stronger binding between the Ni and the B atoms than that of Fe and B. 相似文献
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67.
G.A. Chass S. Lovas R.F. Murphy I.G. Csizmadia 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):481-497
An exhaustive ab initio and DFT search for energetically stable conformers from the topologically possible set was undertaken on the N-acetyl-phenylalanyl-N-methylamide
and N-acetyl-tyrosyl-N-methylamide systems. The geometries of all 81 phenylalanyl and 162 tyrosyl possible rotamers, described
under the rules outlined by Multi-Dimensional Conformational Analysis (MDCA), were attempted at each of the RHF/3-21G, RHF/6-31G(d)
and B3LYP/6-31G(d) levels of theory. A total of 32 and 66 stable conformational minima were found for the phenylalanyl and
tyrosyl amino acid diamides, respectively, at the B3LYP/6-31G(d) level. From the tyrosyl set, 33 unique conformers emerge
when the orientation of the A
i
3
dihedral angle (p-OH orientation) is disregarded. A total of 31 conformers were common to both sets and showed nearly identical geometries.
The comparison of the optimized DFT geometries of the two systems showed near by perfect linear fits with R2 values of 0.9997, 0.9994, 0.9997, and 0.9996 for the φ
i
, ψ
i
, A
i
1
, and A
i
2
dihedral angles, respectively. Relative energies of the matching 31 conformers also fitted to a linear plot with an R2 value of 0.9985. The geometric centroid of the aromatic ring in the sidechain of both systems was found to be within 4.1
?of the H and O atoms of the peptide groups, in 21 and 2 of the conformers, respectively. None of the non-matching conformers
showed any such interaction distance ≤4.1 ?.
Received 1st February 2002 / Received in final form 28 May 2002 Published online 13 September 2002 相似文献
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