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21.
A 35Cl nuclear quadrupole resonance (35Cl-NQR) investigation of polycrystalline Ca(ClO3)2·2H2O is described. The 35Cl-NQR frequencies (νQ) for two resonance lines (νQ1 and νQ2), the spin lattice relaxation time (T1Q) for νQ2 only and the line width δνQ2 were measured in the temperature range 292–345 K, except for the frequency measured up to 455 K. The observed decrease in the resonance frequencies with increasing temperature permitted the determination of the frequencies of librations of the ClO3− ion about two axes perpendicular to the three-fold axis of the ion mainly responsible for this effect. The temperature dependence of the relaxation time T1Q proved the occurrence of water diffusion and hindered rotation of ClO3− ions. The activation energies of these two molecular motions were determined, and their effect on the electric field gradient at the site of a chlorine nucleus was discussed. Temperature measurements of the line width δνQ2 confirmed the conclusions drawn from the analysis of T1Q(T). 相似文献
22.
The correlation factors Rp and Rs are determined for the dielectric polarization and the non-linear dielectric effect in dilute solutions of nitrobenzene in benzene. Assuming dipole association of the nitrobenzene molecules to be restricted to dimerization, we determined the concentration x2 of dimers, their dipole moment μdim, and the equilibrium constant Kx and Gibbs energy ΔG of the dimerization process. 相似文献
23.
Bolesław T. Karwowski 《Central European Journal of Chemistry》2008,6(3):450-455
Reactive oxygen species (ROS) may generate different nucleoside/nucleotide radicals in a cell environment. In this study,
the possibility of cyclic-2’-deoxyadenosines formation by a rearrangement of their free radicals was investigated. It seems
that for cyclic-nucleosides formation, adoption of an O4’-exo conformation by the sugar moiety is necessary. However, this
is the energetically unfavoured form of the 2-deoxyribose ring. Moreover, the creation of a O5’, C8 bond in purine deoxy-nucleosides/nucleotides
leads to the termination of the DNA elongation process.
相似文献
24.
A correlation between the electronic structure and biological activity of chosen dichlorodiphenyltrichloroethane (DDT)-type insecticides: 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene, 2,2-bis(4-chlorophenyl)ethanoic acid and 4,4'-dichlorobenzophenone (used in agriculture) has been analysed on the basis of the (35)Cl-nuclear quadrupole resonance (NQR) spectroscopy. The (35)Cl-NQR resonance frequencies measured at 77 K have been correlated with the lethal dose (LD(50)) parameter that characterises the biological activity of these insecticides. 相似文献
25.
Bolesław Kacewicz 《BIT Numerical Mathematics》1983,23(2):217-230
We study the minimum error of algorithms for solving a scalar autonomous ODE. Information is defined asn evaluations of functionals of the right hand sidef. These functionals can be linear or nonlinear and continuous. Euler-integral information is defined and its optimality is proved in a class of regularf. 相似文献
26.
R. Boles Basit 《Mathematical Notes》1971,9(3):181-186
Conditions are obtained for the almost periodicity (or almost automorphy) of an abstract functionf (t) on a group G satisfying the difference equationsf (t)–f(t)=g(t), where, for each G, the function (t) is almost periodic (or almost automorphic) (the difference problem). The investigation of the almost periodicity of the integral
of an almost periodic function (t) on the real line R is reduced to a study of the difference problem.Translated from Matematicheskie Zametki, Vol. 9, No. 3, pp. 311–321, March, 1971.In conclusion I wish to thank V. V. Zhikov for suggesting this problem, and B. M. Levitan and E. A. Gorin for their discussion of the work. 相似文献
27.
The fluorescence quenching of polystyrene by oxygen at room temperature was investigated. The diffusion coefficient of oxygen in polystyrene films was taken as 3.1 × 10?7 cm2/sec; the energy migration coefficient of polystyrene in the excited singlet state was estimated as 6 × 10?6 cm2/sec. 相似文献
28.
Brownian dynamics simulation of protein association 总被引:1,自引:0,他引:1
Scott H. Northrup J. Alan Luton Jeffrey O. Boles John C. L. Reynolds 《Journal of computer-aided molecular design》1988,1(4):291-311
Summary The Brownian Dynamics (BD) method is applied to study the diffusive dynamics and interaction of two proteins, cytochrome c (CYTC) and cytochrome c peroxidase (CYP). We examine the role of protein electrostatic charge distribution in the facilitation of protein-protein docking prior to the electron transfer step, assessing the influence of individual charged amino acid residues. Accurate interaction potentials are computed by iterating the linearized Poisson-Boltzmann (PB) equation around the larger protein CYP. The low dielectric constant inside proteins, electrolyte screening effects and irregular protein surface topography are taken into account. We observe a large ensemble of electrostatically stable encounter complexes seemingly with acceptable geometric requirements for electron transfer rather than a single dominant complex. Stabilities of the large variety of docking complexes are rationalized in terms of generalized charged residue complementarities. However, it is found that the electrostatic interactions giving rise to complex stabilities are somewhat nonspecific in nature. A large series of additional simulations are performed in which individual charged residues on CYTC have been chemically modified. Resulting perturbations of the association rate are significant and qualitatively similar to results observed in comparable kinetics experiments. We therefore demonstrate the potential of the Brownian dynamics method to estimate the effects of site-directed mutagenesis on protein-protein and protein-ligand diffusional association rates. 相似文献
29.
The optimal solution of initial-value problems in ODEs is well studied for smooth right-hand side functions. Much less is known about the optimality of algorithms for singular problems. In this paper, we study the (worst case) solution of scalar problems with a right-hand side function having r continuous bounded derivatives in R, except for an unknown singular point. We establish the minimal worst case error for such problems (which depends on r similarly as in the smooth case), and define optimal adaptive algorithms. The crucial point is locating an unknown singularity of the solution by properly adapting the grid. We also study lower bounds on the error of an algorithm for classes of singular problems. In the case of a single singularity with nonadaptive information, or in the case of two or more singularities, the error of any algorithm is shown to be independent of r. 相似文献
30.
Louis A. Silks III Jeffrey O. Boles Brenna P. Modi R. Bruce Dunlap Jerome D. Odom 《合成通讯》2013,43(10):1555-1562
A direct and efficient route for the construction of racemic and optically active L-telluromethionine (L-Te-Met) starting from the readily available hydrochloride salt of α-amino-γ-butyrolactone and lithium methyltellurolate is described. The reaction has been successfully scaled up to afford gram quantities of L-Te-Met in 75–80% yield. 相似文献