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61.
Summary Dielectric measurements on Na2B4O7(99.5%)−V2O5(0.5%) glass system, in the frequency range 10−3 to 104 Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single
mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies
(0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed
by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values
ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na+ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this
glass system. 相似文献
62.
The interactions between oppositely charged surfactant-polymer systems have been studied using surface tension and conductivity measurements and the dependence of aggregation phenomenon over the polyelectrolyte concentration and chain length of cationic ATAB surfactants, cetyltrimethyl ammonium bromide (CTAB), tetradecyltrimethyl ammonium bromide (TTAB), and dodecyltrimethyl ammonium bromide (DTAB) have been investigated. It was observed that cationic surfactants induce cooperative binding with anionic polyelectrolyte at critical aggregation concentration (cac). The cac values of ATAB surfactants in the presence of anionic polyelectrolyte, sodium carboxy methyl cellulose (NaCMC), are considerably lower than their critical micelle concentration (cmc). After the complete complexation, free micelles are formed at the apparent critical micelle concentration (acmc), which is slightly higher in polyelectrolyte aqueous solution than in pure water. Among the cationic surfactants (i.e., CTAB, TTAB, and DTAB), DTAB was found to have least interaction with NaCMC. Surfactants with longer tail size strongly favor the interaction, indicating the dependence of aggregation phenomenon on the structure, morphology, and tail length of the surfactant. 相似文献
63.
Anis Rezgui 《Acta Appl Math》2005,89(1-3):271-286
In this work we study partial differential operators of infinite order on spaces of entire functions, generalizing some of
the results presented in [2] and [5] to the new spaces introduced in [3]. 相似文献
64.
To deal with the radiation from an axially symmetric pillbox resonator embedded in LiNbO3 substrate, an eigenvalue equation is derived from the expression of the finite-element beam propagation method in a cylindrical coordinate system. By solving the eigenvalue equation iteratively, the field distributions and the angular phase constants of the pillbox resonator are evaluated. The iterative scheme of solving the eigenvalue equation is an extension of our previous direct solution method which was described for a lossless case. The results obtained by this method are compared with those obtained analytically, and excellent agreement is found. 相似文献
65.
Mohamed Rifaat Hamza Elmoghayar Abdel-Ghani Ali El-Agamey Mohamed Yousri Abdel-Samad Nasr Mohamed Mohamed Mohamed Sallam 《Journal of heterocyclic chemistry》1984,21(6):1885-1887
The reaction of 2-cyanoethanoic acid hydrazide and arylidenemalononitrile was studied as a new route for the synthesis of N-amino-2-pyridones. Pyrano[2,3-c]pyrazole and thiazolo[2,3-a]pyridine could be prepared from the reaction of arylideneazolones with the same reagent. 相似文献
66.
The use of a scanning Fabry-Perot interferometer of variable length (variable resolution) for investigating the output of a cw CO laser is reported. Under experimental conditions required to achieve maximum power it was found that the laser output consisted of two or more simultaneously occuring transitions due to the overlapping nature of the vibration- rotation bands. The frequency differences between these transitions were measured to an accuracy of 0.01 cm-1. Operation of the CO laser on a single vibration-rotation transition was obtained by controlling the laser gain with the experimental variables of discharge pressure, gas temperature, and optical alignment. An alternative approach of obtaining monochromatic radiation, by using a Fabry-Perot interferometer as a frequency selective filter external to the CO laser, is reported. 相似文献
67.
Laurent?DenisEmail author Anis?Matoussi Lucretiu?Stoica 《Probability Theory and Related Fields》2005,133(4):437-463
In this paper we prove Lp estimates (p≥2) for the uniform norm of the paths of solutions of quasilinear stochastic partial differential equations (SPDE) of parabolic
type. Our method is based on a version of Moser's iteration scheme developed by Aronson and Serrin in the context of non-linear
parabolic PDE. 相似文献
68.
Dr. M. H. Hamza 《Mathematical Methods of Operations Research》1968,12(1):121-132
Zusammenfassung An Hand von einfachen Modellen wird gezeigt, daß man die Theorie der Automatik auf das Gebiet der Lagerhaltung anwenden kann. Ein kontinuierliches lineares System und ein diskretes System werden untersucht. Für das erste System wird dieLaplace-Transformation verwendet, für das zweite diez- und modifiziertez-Transformation. Schließlich wird die Zeitbereichmethode eingeführt und eine Anwendung davon gezeigt.
Summary By means of simple models, it is shown that control theory can be applied to inventory control problems. TheLaplace transform is used in the study of a linear continuous system. Thez and modifiedz transforms are employed in the study of a discrete system. Finally, the state space approach is introduced and is applied to a model with multirate sampling.相似文献
69.
M'Hamed Ali Hamza Guy Serratrice Jean-Jacques Delpuech 《Magnetic resonance in chemistry : MRC》1981,16(2):98-102
Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors are reported for five polyfluoroaromatic compounds at 28°C. In all cases the relaxation of the fluorine bearing carbon is predominantly dipolar. Effective correlation times are smaller than those of the analogous benzene derivatives by a factor of 3–4, in qualitative agreement with predictions from the Stokes–Einstein diffusion theory. The T1 values for the para-carbon of monosubstituted fluorobenzenes is clearly shorter than the T1 values for the ortho- and meta-carbons. This phenomenon was traced to anisotropic tumbling, and D∥ and D⊥ diffusion coefficients were computed using Woessner's equations for molecules assumed to behave like symmetric rotors about their C2 in-plane principal symmetry axis. Equal tumbling ratios, D∥/D⊥, were found in this way for toluene and perfluorotoluene. 相似文献
70.
Bugarcić ZD Nandibewoor ST Hamza MS Heinemann F van Eldik R 《Dalton transactions (Cambridge, England : 2003)》2006,(24):2984-2990
Substitution reactions of the complexes [Pd(bpma)(H2O)]2+, [Pd(bpma)Cl]+, [Pd(dien)(H2O)]2+ and [Pd(dien)Cl]+, where bpma = bis(2-pyridylmethyl)amine and dien = diethylentriamine or 1,5-diamino-3-azapentane, with some nitrogen-donor ligands such as triazole, pyrazole, pyrimidine, pyrazine and pyridazine, were studied in an aqueous 0.10 M NaClO4 at pH 2.8 using variable-temperature and -pressure stopped-flow spectrophotometry. The second-order rate constants indicate that the Pd(II) complexes of bpma, viz. [Pd(bpma)(H2O)]2+ and [Pd(bpma)Cl]+, are more reactive than the complexes of dien, viz. [Pd(dien)(H2O)]2+ and [Pd(dien)Cl]+. Also, the aqua complexes, [Pd(bpma)(H2O)]2+ and [Pd(dien)(H2O)]2+, are much more reactive than the corresponding chloro complexes. The most reactive nucleophile of the five-membered rings is triazole and for the six-membered rings the most reactive one is pyridazine. Activation parameters were determined for all reactions and the negative entropies and volumes of activation (Delta S++, Delta V++) support an associative ligand substitution mechanism. The crystal structure of [Pd(bpma)(H2O)](ClO4)2.2H2O was determined by X-ray diffraction. Crystals are monoclinic with the space group P2(1)/c. The coordination geometry of [Pd(bpma)(H2O)]2+ is distorted square-planar. The Pd-N (central) bond distance, 1.958(5) A, is shorter than the other two Pd-N distances, 2.007(5) and 2.009(5) A. The Pd-O distance is 2.043(5) A. 相似文献