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61.
Using the equations of motion of pulse width and chirp, we present an analytical method for designing dispersion-managed (DM) fiber systems without optical losses. We show that the initial Gaussian pulse considered for the analytical design of periodically amplified DM fiber systems with losses will propagate as a proximity fixed point. Then averaging the DM soliton fields obtained from the slow dynamics of the proximity fixed point will yield the exact fixed point.  相似文献   
62.
Encapsulation of 4−[(4′-hydroxy−3′,5′-dimethylphenyl)(aryl)-methylene]−2,6−dimethyl-cyclohexa−2,5−dienones (when aryl=4−hydroxyphenyl 1, 4−methoxyphenyl 2, 2,3,4-trimethoxy phenyl 3) by β-cyclodextrin is studied. The compound 2 is selectively encapsulated by β-cyclodextrin. The result is rationalised by analysing the structural parameters from the crystal structure of 13. The visible spectra of the compounds 2 and 3 at pH 9.0 show red shifts on the absorption maxima upon addition of cetyltrimethylammonium bromide (CTAB). For example, addition of a solution of CTAB to aqueous ethanolic solution of 2 at pH 9 causes shift of the absorption at 578–593 nm (Δλmax=15 nm). The advantage of this observation is taken to use 2 and 3 to determine the critical micelle concentration of CTAB in basic medium.Graphical Abstract Structural investigations on quinone methides for understanding their properties in confined media Rupam J. Sarma, Andrei S. Batsanov, Ritu Kataky, Jubaraj B. Baruah   相似文献   
63.
We present experiments that show achievement of highly efficient generation of parametric sidebands in an optical fiber with dual-frequency, circularly polarized pump waves. An appropriate choice of the separation between the pump frequencies permits a strong reduction of the optimum power for highly efficient frequency conversion.  相似文献   
64.
65.
Aqua-bridged binuclear cobalt (II) benzoate complexes having pyridine as auxiliary ligands are synthesised through solid state reactions and characterised. The binuclear core in these complexes comprise of two bridging benzoates and an aqua bridge. Each of the cobalt (II) centre is further co-ordinated to one benzoate and two pyridine ligands. The aqua-bridged cobalt (II) benzoate complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4] ·  (C6H6)(BzOH) (1a) is inclusion compounds with benzoic acid and benzene (where OBz  =  benzoate, py  =  pyridine). Analogous complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4] · 1.5(C6H6) without benzoic acid included is also prepared by an alternative method and structurally characterised. Analogous aqua-bridged complex derived from p-chlorobenzoic acid in unsolvated form is characterised. The Co–O–Co separation in these complexes is in the range of 3.55–3.64 Å with angles Co–O–Co varying from 111.8° to 116.4°. While similar reaction in solution leads to the formation of mononuclear complex having composition [Co(OBz)2(Py)2(H2O)]. The unsubstituted benzoate complex 1a can be easily oxidised to form a tetrameric cobalt (III) complex having benzoate and oxo-bridged structure with a Co4O4 core.  相似文献   
66.
67.
The role of pH in the formation of metal-organic frameworks (MOFs) has been studied for a series of magnesium-based carboxylate framework systems. Our investigations have revealed the formation of five different zero-dimensional (0D) to three-dimensional (3D) ordered frameworks from the same reaction mixture, merely by varying the pH of the medium. The compounds were synthesized by the hydrothermal method and characterized by single-crystal X-ray diffraction. Increase of the pH of the medium led to abstraction of the imine hydrogen from the ligand and a concomitant increase in the OH(-) ion concentration in the solution, facilitating the construction of higher dimensional framework compounds. A stepwise increase in pH resulted in a stepwise increase in the dimensionality of the network, ultimately leading to the formation of a 3D porous solid. A gas adsorption study of the 3D framework compound confirmed its microporosity with a BET surface area of approximately 450?m(2) g(-1). Notably, the 3D framework compound catalyzes aldol condensation reactions of various aromatic aldehydes with acetone under heterogeneous conditions.  相似文献   
68.
A microwave-promoted aza-Diels-Alder reaction between 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil and aldimines has been developed for the construction of dihydropyrido[4,3-d]pyrimidines. Urea is effectively employed as an environmentally benign source of ammonia in the absence of any catalyst or solvent. The key step in the reaction is in situ generation and trapping of the reactive aldimine formed from urea and aldehyde by the diene system of the uracil. The reaction is clean, and excellent yields are obtained in a matter of a few minutes.  相似文献   
69.
Some new oxovanadium(V) complexes, [VOL1-3(OEt)(EtOH)] (1-3), have been reported, which were obtained from the reaction of the Schiff bases H2L1-3 (where H2L1 = the salicylhydrazone of diacetyl monoxime; H2L2 = the 4-methoxy salicylhydrazone of diacetyl monoxime and H2L3 = the 4-hydroxy salicylhydrazone of diacetyl monoxime) with VO(acac)2 in a 1:1 molar ratio. Three 4-R-aroylhydrazoneoximes (V) have been used as ligands in the present study, differing in the inductive effect of the substituent R (R = H, OCH3 and OH), in order to observe their influence, if any, on the redox potentials and biological activity of the complexes. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV-Vis and NMR spectroscopy. An X-ray diffraction study of [VOL1(OEt)(EtOH)] (1) reveals that the metal center has a distorted octahedral O5N coordination sphere, where the O,N,O donor ligand and the ethoxo group constitute a satisfactory O3N basal plane. Cyclic voltammetry of the complexes show a quasi-reversible cyclic voltammetric response in the potential range 0.29-0.36 V involving a single electron V(V)-V(IV) reduction. The complexes have also been screened for their antibacterial activity against Escherichia coli, Bacillus, Proteus and Klebsiella. Minimum inhibitory concentrations of these complexes and the antibacterial activities indicate compound 1 as the potential lead molecule for drug design.  相似文献   
70.
We address the problem of characterization of light pulses that propagate in long-haul high-bit-rate optical communication systems, under strongly perturbed conditions. We show that the conventional technique for characterization of the phase and intensity profile of such pulses becomes qualitatively inconsistent when the pulse’s profile is asymmetrically distorted with respect to its center-of-mass. We resolve these inconsistencies by partially reformulating the conventional technique by means of appropriate pulse parameters, which we call upgraded parameters, which allow a fair characterization of the intensity and phase of all types of light pulses, including those which are asymmetrically distorted. We illustrate the effectiveness of the upgraded parameters by applying them to a meticulous characterization of light pulses in a dispersion-managed optical fiber system in which third-order dispersion is acting as a strong perturbation.  相似文献   
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