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31.
Zerrouki  A.  Allouchi  H.  Nicolaï  B.  El Kadiri  S.  Bahari  Z.  Céolin  R.  Rietveld  I. B. 《Structural chemistry》2016,27(2):697-704
Structural Chemistry - The crystal structure of N,N,N′,N′-tetrakis-[(1H,2,4-triazol-1-yl)methyl]-ethane-1,2-diamine has been fully determined at six different temperatures by X-ray...  相似文献   
32.
33.
This paper models airline competition as a two-stage game in frequency and prices, allowing for asymmetric frequency equilibria. The approach follows the spatial multiproduct oligopoly literature. The dynamic structure gives airlines an incentive to choose asymmetric frequency equilibria such that price competition is reduced. This feature is most pronounced in the case of inelastic demand, for which a maximum differentiation result is derived. We apply the model in a simulation study of airline deregulation of the Amsterdam—Maastricht market in The Netherlands, calculating welfare effects for various types of post-deregulation entry.  相似文献   
34.
l-Tyrosine alkyl esters are used as prodrugs for l-tyrosine. Although prodrugs are often designed for their behavior in solution, understanding their solid-state properties is the first step in mastering drug delivery. The crystal structure of l-tyrosine methyl ester has been determined and compared to published structures of l-tyrosine and its ethyl and n-butyl esters. It is almost isostructural with the other esters: it crystallizes in the orthorhombic chiral space group P212121, a = 5.7634(15) Å, b = 12.111(2) Å, c = 14.3713(19) Å, V = 1003.1(4) Å3 with Z′ = 1. Their main packing motif is a C(9) infinite hydrogen-bond chain, but the conformation of l-tyrosine methyl ester is different from the other two: eclipsed versus U-shaped, respectively. The published structure of the ethyl ester, which was incomplete, has been confirmed by X-ray powder diffraction data. Because l-tyrosine methyl ester is very stable (28 years stored at room temperature), and its hydrolysis rate is relatively low, it should be one of the better prodrugs among the alkyl esters of tyrosine.  相似文献   
35.
This is a continuation of the preceeding paper, Part I, and presents a discussion of the nature of the precursor structure formation process observed in the flow-induced crystallization experiments described in I. A discussion of stress-induced crystallization theory as applied to these experiments is also given and a first-order analysis of crystal nucleation rates is presented. Conclusions regarding the nature of flow-induced crystallization and our current ability to quantitatively model the overall process are also presented.  相似文献   
36.
From the reaction of MeReO3 with the neutral arylamine C6H5CH2NMe2 and the aryldiamine C6H4(CH2NMe2)2−1,3, have been isolated in good yields the 1/1 adduct complex [MeReO3 · C6H5CH2NMe2], 1, and the 2/1 adduct complex [(MeReO3)2 · C6H4(CH2NMe2)2− 1,3], 2, respectively. The X-ray molecular structure of 2 shows that both rhenium centres have a trigonal bipyramidal geometry and in the axial positions of each rhenium centre are one of the NMe2 units of the aryldiamine ligand and a methyl group. The mono(ortho)-chelated arylaminorhenium trioxide complex [ReO3(C6H4CH2NMe2−2], 3, can be synthesized by a transmetallation reaction of ClReO3 with [ZnC6H4CH2NMe2−22] in a 2:1 molar ratio. In a similar way the bis(ortho)-chelated arylaminorhenium trioxide complex [ReO3C6H3(CH2NMe2)2−2,6], 4, can be synthesized by addition of a mixture of [Li2C6H3(CH2NMe2)2−2,62] and ZnCl2 to ClReO3. Complexes 3 and 4 have been isolated as white solids in 66% and 81% yields respectively. The rhenium centre in complex 4 has a bicapped tetrahedral geometry in which the monoanionic C6H3(CH2NMe2)2−2,6 ligand is pseudo-facially bonded with a characteristic N1-Re-N2 angle of 107.7(3)°, a Re-Cipso bond length of 2.112(11) Å and Re-N1 and Re-N2 bond lengths of 2.518(9) Å and 2.480(8) Å respectively.  相似文献   
37.
Although polymorphism of drug molecules is often studied with extensive and excellent experimental data, pressure appears to be a forgotten variable. In this article, an analysis is provided of the phase behavior of Atovaquone using available literature data. A pressure–temperature diagram is constructed topologically by way of the Clapeyron equation. The method leads to the conclusion that Atovaquone phase I and III behave enantiotropically, like α- and β-sulfur do in their paradigmatic P–T diagram, and that phase I is stable at room temperature and under “ordinary” pressure.  相似文献   
38.
Indomethacin crystallizes from solutions in tetrahydrofuran as a solvate exhibiting the mole ratio 1 indomethacin:2 tetrahydrofuran. Upon heating, desolvation into indomethacin phase I occurs through partial amorphization and transitory formation of a phase, which is different from the crystallographically known polymorphs. The X-ray powder diffraction pattern of the solvate was tentatively indexed on a triclinic lattice (a = 31.454(5) Å, b = 17.883(3) Å, c = 10.551(2) Å, α = 70.55(2)°, β = 105.31(2)°, γ = 136.70(1)°). Assuming Z = 6 (1 indomethacin + 2 tetrahydrofuran) formula units per unit cell, the solvate’s specific volume is similar to the value calculated using additivity.  相似文献   
39.
Uniaxial negative thermal expansion in crystals of tienoxolol   总被引:1,自引:0,他引:1  
The thermal expansion of tienoxolol has been investigated by X-ray powder diffraction up to its melting temperature. The data indicate that the expansion is anisotropic and even negative in one direction of the unit cell. The supramolecular structure formed by hydrogen-bonds reflects that of a trellis, which explains the observed behavior of tienoxolol crystals.  相似文献   
40.
This paper aims to present a newly developed distance friction minimization (DFM) method in the context of data envelopment analysis (DEA) in order to generate an appropriate (non-radial) efficiency-improving projection model, for both input reduction and output increase. In this approach, a generalized distance function, based on a Euclidean distance metric in weighted spaces, is proposed to assist a decision making unit (DMU) to improve its performance by an appropriate movement towards the efficiency frontier surface. A suitable form of multidimensional projection function for efficiency improvement is given by a Multiple Objective Quadratic Programming (MOQP) model. The paper describes the various steps involved in a systematic manner.  相似文献   
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