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81.
Amira S Spångberg D Zelin V Probst M Hermansson K 《The journal of physical chemistry. B》2005,109(29):14235-14242
The optimized geometry and energetic properties of Fe(D2O)n 3+ clusters, with n = 4 and 6, have been studied with density-functional theory calculations and the BLYP functional, and the hydration of a single Fe 3+ ion in a periodic box with 32 water molecules at room temperature has been studied with Car-Parrinello molecular dynamics and the same functional. We have compared the results from the CPMD simulation with classical MD simulations, using a flexible SPC-based water model and the same number of water molecules, to evaluate the relative strengths and weaknesses of the two MD methods. The classical MD simulations and the CPMD simulations both give Fe-water distances in good agreement with experiment, but for the intramolecular vibrations, the classical MD yields considerably better absolute frequencies and ion-induced frequency shifts. On the other hand, the CPMD method performs considerably better than the classical MD in describing the intramolecular geometry of the water molecule in the first hydration shell and the average first shell...second shell hydrogen-bond distance. Differences between the two methods are also found with respect to the second-shell water orientations. The effect of the small box size (32 vs 512 water molecules) was evaluated by comparing results from classical simulations using different box sizes; non-negligible effects are found for the ion-water distance and the tilt angles of the water molecules in the second hydration shell and for the O-D stretching vibrational frequencies of the water molecules in the first hydration shell. 相似文献
82.
Summary 1,2-Diphenyl-2-(benzoylhydrazino)ethanol (DBE) and 1,2-diphenyl-2-(p-nitrobenzoylhydrazino)ethanol (DPNBE) form complexes of general formulae [M(H2L)2]X2 and [M2L2] (where M = Co or Ni, H2L and L are the neutral and dibasic forms of the ligands and X = Cl or NO3). The analytical, spectral, magnetic and physical studies show the complexes to be of two types, namely monomeric cationic species prepared in neutral media and neutral binuclear oxygen-bridged species formed in alkaline solution. The ligands are tridentate, coordinating through carbonyl (or enolic) oxygen, azomethine nitrogen and alcoholic oxygen atoms. 相似文献
83.
[structure: see text] A novel cyclic peptide, callynormine A, was isolated from the Kenyan marine sponge Callyspongia abnormis and its structure elucidated by interpretation of its NMR data and X-ray diffraction analysis. Callynormine A represents a new class of heterodetic cyclic peptides (designated endiamino peptides) possessing an alpha-amido-beta-aminoacrylamide cyclization functionality. 相似文献
84.
Kinetics of oxidation of 1-phenylsemicarbazide (PSC) by peroxydisulphate ion (PDS) have been carried out where by the pseudo first order condition was verified at large excess of PDS concentration. The rate of the reaction was followed spectrophotometrically, The stoichiometry was found to be 1:1 where 1-phenylazoformamide is the oxidation product. The effect of acidity on the rate of oxidation was investigated for different temperatures. The parameters of activation ΔG*, ΔH* and ΔS* were computed for both hydrogen ion depedent and hydrogen ion independent reaction pathes. A free radical mechanism was proposed. 相似文献
85.
Treatment of the unsymmetrical β-iminoamine ligands [PhCN(Ar)CHCNH(Ar)Me] with the zerovalent complex Pd(dba)2 in the presence of the methallyloxyphosphonium salt, gives high yields of the cationic β-diimine complexes [PhCN(Ar)CH2CN(Ar)(Me)Pd(η3-C4H7)]+[PF6]− (Ar = 2-Me-C6H4 (7); 2-MeO-C6H4 (8); 2,6-Me2-C6H3 (9); 2,6-iPr2-C6H3 (10)). All the new complexes have been characterised by NMR and IR spectroscopy. The structure of the cationic methallyl palladium complex (10) has been solved by X-ray crystallography. 相似文献
86.
87.
Amira Zaouak Ahlem Noomen Haikel Jelassi 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(1):37-47
Cesium uptake by natural zeolite clinoptilolite from Bulgaria was studied using batch technique and model solutions. The optimal conditions of interaction were determined. The pseudo-second-order rate model better describes the kinetic data obtained at different concentrations. The intraparticle diffusion and the surface diffusion models were tested to identify the rate-controlling step. The sites in the structure of clinoptilolite that are preferable for exchange were studied by application of Rietveld structural approach and the sequence of site occupation by cesium was followed. The Langmuir isotherm model provides a good fit of the equilibrium experimental data. The thermodynamic parameters for the system were calculated. 相似文献
88.
Norbani Abdullah Suhana Mohd Said Yanti Yana Halid Megat Muhammad Ikhsan Megat Hasnan Naima Sharmin Siti Amira Mat Hussin 《Journal of Coordination Chemistry》2016,69(19):2954-2971
Nickel(II) carboxylates [Ni(CH3(CH2)14COO)2(H2O)2] (1) and [Ni(C6H5COO)2(H2O)2] (2) were obtained from reactions of NiCl2·6H2O with CH3(CH2)14COONa and C6H5COONa, respectively. Complex 1 reacted with pyridine (pyr) to form [Ni(CH3(CH2)14COO)2(pyr)2(H2O)2] (3) and [Ni2(μ2-H2O)(CH3(CH2)14COO)4(pyr)4] (4) in the same reaction mixture, and reacted with cyclam to form an ionic complex, [Ni(CH3(CH2)14COO)(cyclam)(H2O)]CH3(CH2)14COO·4H2O (5). In contrast, 2 reacted with cyclam to form [Ni(C6H5COO)2(cyclam)] (6). Finally, 6 reacted with p-(hexadecyloxy)pyridine (L) to form an ionic complex, [Ni(cyclam)(L)2](C6H5COO)2 (7). Complexes 3–6 were single crystals. All complexes have octahedral Ni(II) center(s) and were magnetic. Complexes with cyclam as co-ligand were more thermally stable than those with pyridine and its derivative, L. Complexes 3 and 4 were mesomorphic after partial loss of water and/or pyridine ligands on heating. The ionic complexes 5 and 7 were not mesomorphic, but showed good thermoelectrical behavior with negative Se values in CHCl3 (?0.28 mV K?1 for 5; -0.39 mV K?1 for 7) and positive Se values in C2H5OH (+0.25 mV K?1 for 5; +0.20 mV K?1 for 7). 相似文献
89.
Helwa Amira A. Gedawy Ehab M. Abou-Seri Sahar M. Taher Azza T. El-Ansary Afaf K. 《Research on Chemical Intermediates》2018,44(4):2685-2702
Research on Chemical Intermediates - New series of pyrimidinone-5-carbonitriles 3a–i, 4a–e, 5a–c, 6 and 7 have been synthesized and explored for their activities as anticancer,... 相似文献
90.
Chrif Sada Fatma Amor Rym Ben Chrif Amira Zid Mohamed Faouzi 《Journal of Solid State Electrochemistry》2021,25(7):1987-1997
Journal of Solid State Electrochemistry - Crystals of Ag0.2K0.8Nb4AsO13 (I) and Ag0.62K0.38Nb4AsO13 (II) were synthesized by a solid-state reaction. Both of them crystallize in the orthorhombic... 相似文献