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31.
Spectral studies of Co substituted Ni-Zn ferrites 总被引:1,自引:0,他引:1
M.A. Amer A. TawfikA.G. Mostafa A.F. El-ShoraS.M. Zaki 《Journal of magnetism and magnetic materials》2011,323(11):1445-1452
The spinel ferrites Zn0.35Ni0.65−xCoxFe2O4, 0≤x≤1, have been prepared using the standard ceramic technique. Room temperature Mössbauer, X-ray and infrared IR spectra were used for carrying out this study. X-ray patterns reveal that all the samples have single-phase cubic spinel structure. The Mössbauer spectra of the samples show a paramagnetic phase for x=0 and a six-line magnetic pattern and a central paramagnetic phase for x≥0.1. They are analyzed and attributed to two magnetic subpatterns and two quadrupole doublets due to Fe3+ ions at the tetrahedral A-sites and octahedral B-sites. Four absorption bands are observed in IR spectra. They confirm the spinel structure of the samples and existence of Fe3+ ions in the sample sublattices. The deduced hyperfine interactions, lattice parameters, absorption band positions and intensities and force constant are found to be dependent on the substitution factor x, where the cation distribution is estimated. The hyperfine magnetic fields, magnetization and lattice resonant frequency are found to be dependent on the interionic distance. 相似文献
32.
A reinvestigation of the reactions of urea derivatives of diaminomaleonitrile 2 with aldehydes or ketones in the presence of triethylamine has established that the products of these reactions are not pyrimidino[5,4-d]pyrimidines 9 as previously reported, but 8-oxo-6-carboxamido-1,2-dihydropurines 12, which are oxidized rapidly in air to the corresponding 6-carboxamidopurines 13. Similarly, the reaction of Schiff base derivatives of DAMN 5 with isocyanates in the presence of triethylamine gives the substituted 2-oxoimidazoles 20 and not the pyrimidine derivatives 8 as previously claimed. The compounds 20 cyclize in solution and are easily oxidized to 8-oxopurine-6-carbonitriles 22, which give the same 8-oxopurine-6-carboxamides 13 upon further hydrolysis. 相似文献
33.
Thermal decomposition and creation of reactive solid surfaces 总被引:1,自引:0,他引:1
Three chromia precursors, namely CrO3, (NH4)2Cr2O7 and chromia gel, were subjected to thorough thermal analysis by means of TG and DTA. The thermal decomposition products obtained by calcination of these precursors at various temperatures (150–500°) for 5 h were investigated by infrared and X-ray techniques. The results obtained allowed a thorough physicochemical characterization of the intermediate steps and products throughout the thermal decomposition. 相似文献
34.
Atif Fazal Sahar Al-Fayez Laila H. Abdel-Rahman Zaki S. Seddigi Abdul Rahman Al-Arfaj Bassam El Ali Mohammad A. Dastageer Mohammad A. Gondal Mohammed Fettouhi 《Polyhedron》2009,28(18):4072-4076
New copper(I) mixed-ligand complexes 1–4 of the formula Cu(N–N)PR3X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR3 = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl)3}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states. 相似文献
35.
A New and Facile Synthesis of Novel Pyrazolothienopyrimidines and Imidazopyrazolothienopyrimidines
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4‐Amino‐3‐methyl‐1‐phenyl‐1H‐thieno[2,3‐c]pyrazole‐5‐carboxamide ( 5 ), which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrazolothienopyrimidines and imidazopyrazolothienopyrimidines compounds. Reaction of amino thienopyrazole carboxamide 5 with triethyl orthoformate afforded thienopyrazolopyrimidine 6 . Chlorination of the latter compound, using phosphorus oxychloride afforded the chloro pyrazolothienopyrimidine 7 , which underwent nucleophilic substitution reactions with various primary and secondary amines to give the alkyl (aryl) amino pyrimidine compounds 8a–d . On the other hand, the reaction of chloropyrimidine 7 with thiourea afforded the pyrimidine thione compound 9 , which was alkylated with α‐halogentaed compounds to afford the S‐alkylated derivatives 10a–c . Also, chloroacetylation of the amino carboxamide 5 using chloroacetyl chloride yielded the chloromethyl pyrazolothienopyrimidine 12 , which underwent nucleophilic substitu‐ tion reactions with various primary and secondary amines to afford the alkyl (aryl) aminomethyl compounds 13a–f . The latter Compounds underwent Mannich reaction to give imidazopyrimidothieno‐ pyrazoles 14a–c . The newly synthesized compounds and their derivatives were fully characterized by elemental and spectral analysis. 相似文献
36.
This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design. 相似文献
37.
W. J. Firth C. T. Seaton E. M. Wright S. D. Smith M. E. Prise G. Litfin J. Mlynek F. Mitschke R. Deserno W. Lange H. J. Eichler F. Maßmann C. Zaki J. Heritage F. V. Karpushko G. V. Simitsyn J. A. Martin-Pereda M. A. Muriel P. W. Smith W. J. Tomlinson Ch. Harder K. Y. Lau A. Yariv J. C. Khoo S. Shepard S. Nahar S. L. Zhuang 《Applied physics. B, Lasers and optics》1982,28(2-3):131-141
38.
The tetradentate Schiff-base ligands, N,N′-bis(salicylidene)-ethylenediamine (Salen), N,N′-bis(salicylidene) butylenediamine (Salbut), and N,N′-bis(salicylidene)-o–phenylenediamine, (sal-o-phen) are very strongly sorbed by cation exchange resin (Dowex-50W) with Fe2+ ions as a counter ion, forming stable complexes. The kinetics of the catalytic decomposition of H2O2 using these complexes was studied in ethanolic medium. The reaction was first-order with salen and sal-o-phen and second-order with salbut with respect to [H2O2]. The rate of the H2O2 decomposition increased either from salen to salbut or from salen to sal-o-phen. Also, the k (per g dry resin) values decreased with increasing both the particle size and the degree of resin cross-linkage. The active species formed at the beginning of the reaction, had an inhibiting effect on the reaction rate. The corresponding activation parameters were calculated from a least-squares fit of the temperature dependence of the rate constant. A reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc. 相似文献
39.
M. A. Zaki Ewiss W. Hogervorst W. Vassen B. H. Post H. Wijnen 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(3):371-383
The Stark effect has been studied in the odd-parity 6snf1,3F3 Rydberg series of barium with high-resolution laser-atomic-beam spectroscopy. Scalar and tensor polarizabilities have been measured of 6snf1F3 levels with n=11–30 and of 6snf3F3 levels withn = 12 ? 40. The contributions of the adjacent even-parity Rydberg levels to these polarizabilities have been calculated as far as data are available. This results in important additional information on the only partly known 6sng1,3G4 series and confirms the perturbation of these series atn = 24 by a 5d7dJ= 4 level. A tentative three-channel quantum-defect-theory analysis of the1,3G4 series has been performed. It is shown that reported level energies of the 6snd1,3D2 series are systematically 0.14 cm?1 too high. 相似文献
40.