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921.
Three aza‐aromatic base adducts of cadmium(II) furoyltrifluoroacetonate, [Cd(4,4′‐bpy)(ftfa)2]n ( 1 ), [Cd(2,2′‐bpy)(ftfa)2] ( 2 ) and [Cd(dmp)(ftfa)2] ( 3 ) (“4,4′‐bpy”, “2,2′‐bpy”, “dmp” and “ftfa” are the abbreviations of 4,4′‐bipyridine, 2,2′‐bipyridine, 2,9‐dimethyl‐1,10‐phenanthroline and furoyltrifluoroacetonate, respectively) have been synthesized and characterized by elemental analysis and IR, 1H NMR and 13C NMR spectroscopy and studied by thermal as well as X‐ray crystallography. The single‐crystal structure of these complexes shows that the coordination number of the CdII ions are six with two N‐donor atoms from aza‐aromatic base ligands and four O‐donors from two the furoyltrifluoroacetonates. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular interactions. 相似文献
922.
In the present study, chemometric analysis of visible spectral data of phospho-and silico-molybdenum blue complexes was used to develop artificial neural networks (ANNs) for the simultaneous determination of the phosphate and silicate. Combinations of principal component analysis (PCA) with feed-forward neural networks (FFNNs) and radial basis function networks (RBFNs) were built and investigated. The structures of the models were simplified by using the corresponding important principal components as input instead of the original spectra. Number of inputs and hidden nodes, learning rate, transfer functions and number of epochs and SPREAD values were optimized. Performances of methods were tested with root mean square errors prediction (RMSEP, %), using synthetic solutions. The obtained satisfactory results indicate the applicability of this ANN approach based on PCA input selection for determination in highly spectral overlapping. The results obtained by FFNNs and by RBF networks were compared. The applicability of methods was investigated for synthetic samples, for detergent formulations, and for a river water sample. 相似文献
923.
Ramin Ghahremanzadeh Somayyeh Ahadi Maryam Sayyafi Ayoob Bazgir 《Tetrahedron letters》2008,49(29-30):4479-4482
Some new phthalazine derivatives were prepared by reaction of phthalhydrazide and dialkyl acetylenedicarboxylates in the presence of N-heterocycles. 相似文献
924.
Issa Yavari Zinatossadat Hossaini Maryam Sabbaghan 《Monatshefte für Chemie / Chemical Monthly》2008,139(8):945-948
The reaction of dialkyl acetylenedicarboxylates or diaroylacetylenes with ethyl bromopyruvate in the presence of enaminones
led to 2-ethyl 3,4-dialkyl 4-bromo-4,5-dihydro-2,3,4-furantricarboxylates or ethyl 3,4-diaroyl-4-bromo-4,5-dihydro-2-furancarboxylate
in excellent yields. These compounds are quantitatively converted to the corresponding 2,3,4-trisubstituted furans by 4-dimethylaminopyridine.
Correspondence: Issa Yavari, Chemistry Department, Tarbiat Modares University, PO Box 14115-175, Tehran, Iran. 相似文献
925.
Substituent effects on cyclonona‐3,5,7‐trienylidenes: a quest for stable carbenes at density functional theory level 下载免费PDF全文
Maryam Koohi Mohammad Zaman Kassaee Bibi Narjes Haerizade Monireh Ghavami Samaneh Ashenagar 《Journal of Physical Organic Chemistry》2015,28(8):514-526
Nine boat‐shaped cyclonona‐3,5,7‐trienylidenes are compared and contrasted with respect to their multiplicity, nucleophilicity, electrophilicity, band gap (ΔEHOMO ? LUMO), Natural bond orbital (NBO) atomic charge, force constant, as well as the aptitude for dimerization, and rearrangement through proper isodesmic reactions at B3LYP/AUG‐cc‐pVTZ and B3LYP/6‐311++G**//B3LYP/6‐31+G* levels of theory. The nine cyclic carbenes include unsubstituted (1CH2) plus eight α‐cyclopropylcyclonona‐3,5,7‐trienylidenes, which are substituted with ?‐SiMe2, ?‐NMe, ?‐PMe, ?‐O, ?‐S, ?‐CH2, ?‐cyclopropyl, and ?‐CMe2 (2SiMe2, 2NMe, 2PMe, 2O, 2S, 2CH2, 2cyclopropyl, and 2CMe2, respectively). The latter eight species enjoy the stabilizing interaction of the occupied Walsh orbital of cyclopropyl with the vacant pπ orbital of the carbene center (Walshcyclopropyl → pπ carbene). Among them, the singlet closed shell 2NMe appears the most promising for exhibiting the highest relative singlet–triplet energy gap (ΔEs ? t = 27.1 kcal mol?1). In contrast, the least stable derivative is triplet 2SiMe2, which exhibits the lowest relative ΔEs ? t of ?5.5 kcal mol?1. The overall trend of ΔEs‐t is 2NMe > 2PMe > 2S > 2O > 2cyclopropyl > 2CMe2 > 2CH2 > 1CH2 > 2SiMe2. With one negative force constant, the unsubstituted 1CH2 turns out to be a transition state, whereas the rest emerge as minima. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
926.
Prof. Dr.-Ing. R. Hatami 《Heat and Mass Transfer》1980,14(2):109-118
The problem of heat transfer in industrial processes, heat exchangers, and combustion chambers is formulated for a case where flow inside the chamber consists of a periodic motion imposed on a fully developed turbulent flow. It is shown that the velocity pulsations induce harmonic oscillations in temperature, thus breaking the temperature field into a steady mean part and a harmonic part. The interaction between the velocity and temperature oscillations introduces an extra term into the energy equation which reflects the effect of pulsations in producing higher heat transfer rates. The analysis shows that when the mean temperature is fully developed with constant heat flux at the wall, there is no effect of the velocity pulsations on the total heat transfer rate along the chamber. For the case where the mean temperature profile is not fully developed, analytical solutions are obtained for asymptotic values of the pulsations frequency. The results show the temperature gradient and its dependence on the frequency. These results are used to evaluate the feasibility of pulsating the flow in a heat exchanger for obtaining higher rates of heat transfer. 相似文献
927.
Hassan Keypour Maryam Shayesteh Reza Golbedaghi Allan G. Blackman Scott A. Cameron 《Transition Metal Chemistry》2013,38(6):611-616
A new potentially octadentate N2O6 Schiff base ligand, H2L derived from the condensation of 2,2′-(1,1′-binaphthyl-2,2′-diylbis(oxy))dianiline and o-vanillin, along with its copper(II) and zinc(II) complexes, is synthesized and has been characterized by elemental analyses, IR, UV–vis, 1H and 13C NMR spectra, as well as conductivity measurements. H2L forms mononuclear complexes of 1:1 (metal:ligand) stoichiometry with Cu(II) and Zn(II), and conductivity data confirm the non-electrolyte nature of these complexes. The [ZnL] and [CuL] complexes display very different solid-state structures, as determined by X-ray crystallography. While the [ZnL] complex has a distorted octahedral geometry about the metal, the [CuL] complex displays a distorted square planar geometry about the copper, with long Cu–O(ether) distances of 2.667 Å. 相似文献
928.
We have performed a density functional theory study to investigate the effect of carbon doping on Stone–Wales (SW) defective sites in the armchair (4, 4), (5, 5) and (6, 6) BNNTs, in order to remove structural instability induced by homonuclear N–N and B–B bonds. Two different orientations of SW defect are considered, parallel and diagonal, and then C atoms are doped at different positions of the defect sites. In general, it seems that among the considered arrangements, C atoms prefer to be substituted for the homonuclear B–B bond. The larger HOMO–LUMO band gaps for the most stable configurations indicate that C doping at B–B sites is kinetically more favorable than the other ones. According to calculated nuclear quadrupole resonance (NQR) parameters as a result of C-doping on SW defective sites, the quadrupole coupling constants (C Q ) of boron nuclei at defective sites decrease by about 0.508–1.406 MHz while 14N C Q of the defective sites, except for N8, increases. Interestingly, C Q of the N sites directly connected to dopant sites has maximum increment (0.612–2.596 MHz) while C Q of the N sites belonging to the B2N3 pentagon is undergone to some minor changes. 相似文献
929.
Ali Ramazani Abbas Azizian Maryam Bandpey Nader Noshiranzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2731-2734
Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 2,2,2-trichloroethanol leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce the corresponding chlorine-containing stabilized phosphorus ylides. An intermolecular Wittig reaction of the chlorine-containing stabilized phosphorus ylides with ninhydrin leads to the corresponding highly electron-poor chlorine-containing alkenes. 相似文献
930.
Maryam Khashi Jamshidkhan Chamani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):839-848
4-(N,N-Dimethylamino)pyridine (DMAP), with a dual role as a basic nucleophilic catalyst, was shown to be a highly efficient catalyst for the synthesis of some new N-(2-aryl-7-benzyl-5,6-diphenyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)benzenesulfonamides through the reaction of 2-aryl-7-benzyl-5,6-diphenyl-7H-pyrrolo[2,3-d]pyrimidin-4-amines (7-deazaadenines) with benzenesulfonyl chlorides. It was also found that the use of DMAP under solvent-free conditions is much more effective than other catalytic systems such as pyridine as both the catalyst and solvent, t-BuOK in t-BuOH, Et3N in ethanol (EtOH), and even DMAP in dimethylformamide (DMF). The influences of the reaction parameters, temperature, and the catalyst amount, on the catalytic performance have been studied. All synthetic compounds were characterized on the basis of their full spectral data. 相似文献