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221.
The reaction of the sterically crowded dinuclear gold(I) amidinate complex Au2(2,6-Me2Ph-form)2, 1, with the less bulky bidentate nitrogen ligands results in the formation of tetranuclear gold(I) complexes. When the less bulky amidinate, K(4-MePh-form), A, was reacted with 1 in a 1:1 stoichiometric ratio, crystals containing equal amounts of the tetranuclear and dinuclear gold(I) aryl formamidinates, Au4(4-MePh-form)4 and Au2(2,6-Me2Ph-form)2, where 2,6-Me2Ph-form = B, were found in the same unit cell, 2 x 2THF: space group P, a = 10.794(11) A, b = 14.392(15) A, c = 25.75(3) A, alpha = 82.564(17) degrees, beta = 85.443(18) degrees, gamma = 82.614(19) degrees. The reaction of K(4-MePh-form), A, and 1 in a 1:2 ratio (excess) produced the tetranuclear complex only, 3. The potassium salt of the exchanged bulky ligand, K(2,6-Me2Ph-form), formed as a byproduct. The reaction of the dinuclear gold(I) complex Au2(2,6-Me2Ph-form)2 with the 3,5-diphenylpyrazolate salt, K(3,5-Ph2pz), resulted in the formation of two tetranuclear mixed-ligand complexes, Au4(3,5-Ph2pz)2(2,6-Me2Ph-form)2 x 2THF, 4 x 2THF (space group P21/c, a = 11.5747(19) A, b = 25.497(4) A, c = 21.221(3) A, beta = 96.979(3) degrees) and Au4(3,5-Ph2pz)3(2,6-Me2Ph-form) x THF, 5 x THF (space group P21/c, a = 23.058(5) A, b = 14.314(3) A, c = 18.528(4) A, beta = 90.94(3) degrees. The block crystals from the tetranuclear complex, 4 x 2THF, contain mixed ligands with each pyrazolate ring facing an amidinate ring. The tetranuclear mixed ligand complex, 5 x THF, was isolated as needles with ligands alternating above and below the Au4 plane. The two tetranuclear mixed-ligand complexes emit at 490 and 530 nm, respectively, under UV excitation. 相似文献
222.
223.
Hetero- and homo-leptic Ru(II) complexes of a new 4,4′-bipyrimidine ligand, th2bpm (6,6′-di(2″-thienyl)-4,4′-bipyrimidine), have been synthesized and characterized. The parent ligand th2bpm has electron rich thiophene units on the periphery of a bidentate ligand which is capable of binding to metal ions. The heteroleptic complex of th2bpm [Ru(bpy)2th2bpm]2+ (bpy = 2,2′-bipyridine) exhibits a Ru-to-bpm metal-to-ligand charge transfer (MLCT) absorption centered at 547 nm and a Ru-to-bpy MLCT absorption centered at 438 nm. The assignment of the low energy absorption is supported by the relative ease of electrochemical reduction of the new complex as compared to [Ru(bpy)3]2+. The homoleptic complex, [Ru(th2bpm)3]2+, exhibits a Ru-to-bpm MLCT absorption at slightly higher energy (544 nm). Both complexes are emissive at room temperature in fluid solution and 5 is one of the lowest energy emitters based on tris-bidentate Ru(II) complexes known (λmax = 770 nm). The luminescence spectra is red-shifted compared to [Ru(bpy)3]2+ and this effect is ascribed to the delocalization in the acceptor ligand. 相似文献
224.
Medlycott EA Hanan GS Loiseau F Campagna S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(10):2837-2846
A series of new heteroleptic and homoleptic Ru(II) complexes containing variously substituted bis(pyridyl)triazine ligands has been prepared and their absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in a rigid matrix at 77 K) have been investigated. For some compounds, X-ray structures have also been determined. The new bis(pyridyl)triazines incorporate additional chromophores, such as biphenyl, phenanthrene, anthracene and bromoanthracene derivatives, so the Ru(II) species can be considered as multichromophoric species. The absorption spectra and redox properties of all the metal complexes have been assigned to features belonging to specific subunits, thus suggesting that these species can be regarded as multicomponent, supramolecular assemblies from an electronic coupling point of view. Whereas most of the complexes exhibit luminescence properties that can be attributed to metal-to-ligand charge-transfer (MLCT) states involving the metal-based subunit(s), the species containing the anthryl and, even more, the brominated anthryl chromophores exhibit complicated luminescence behaviour. For example, 2 d (the anthryl-containing heteroleptic metal compound) exhibits MLCT emission at room temperature and emission from the anthracene triplet at 77 K; 2 e (the bromo-substituted anthryl-containing heteroleptic metal compound) exhibits anthryl-based emission at 77 K and MLCT emission at room temperature, but with a prolonged lifetime, thus suggesting equilibration between two triplet states that belong to different chromophores. The equilibration regime between MLCT and aromatic hydrocarbon triplet states is therefore reached by suitable substitution on the organic chromophore. 相似文献
225.
Fe(II), Co(II), Ni(II) and Cu(II) complexes based on the triazine ligand 2,4-di(2'-pyridyl)-6-(p-bromo-phenyl)-1,3,5-triazine have been synthesised and characterised. The electrochemical, magnetic and spectroscopic properties of the complexes have also been investigated, and the electron deficient triazine ligand has been shown to affect each of these properties. Further investigation of solid state structures of the ligand and its Fe(II), Co(II) and Cu(II) complexes has established that stabilising Br-Br interactions exist which link neighbouring molecules to form one-dimensional tapes. A slight modification of the ligand, i.e., using 2,4-di(2'-pyridyl)-6-(p-methylphenyl)-1,3,5-triazine, in which the phenyl substituent has changed from a bromine to a methyl group, eliminates the one-dimensional tape and gives rise to significant pi-stacking interactions in the solid state. 相似文献
226.
Abd El-halim HF Omar MM Mohamed GG 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):36-44
Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species. 相似文献
227.
Liang Di Chapman David C. Li Youli Oakley Douglas C. Napoleone Tony Juodawlkis Paul W. Brubaker Chad Mann Carl Bar Hanan Raday Omri Bowers John E. 《Applied Physics A: Materials Science & Processing》2011,102(1):213-217
β-SiC nanowires were synthesized by a simple carbothermal reduction of carbonaceous silica xerogel. The morphology and structure
of the nanowires were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscopy.
The results showed that the nanowires were hexagonal prism-shaped hierarchical nanostructures. The typical stacking faults
and twin defects of SiC nanowires were also observed. Band-gap characterization and photoluminescence properties of SiC nanowires
were investigated by UV-vis absorption spectroscopy and fluorescence photometry, respectively. The results showed the SiC
nanowire was an indirect transition semiconductor and the band gap energy for the SiC nanowires was 2.85 eV. The photoluminescence
peak value at 470 nm (2.64 eV) originating from the SiC nanowires was a little higher than the value of band-gap energy. 相似文献
228.
We derive a spin-dependent Hamiltonian that captures the symmetry of the zone edge states in silicon. We present analytical expressions of the spin-dependent states and of spin relaxation due to electron-phonon interactions in the multivalley conduction band. We find excellent agreement with experimental results. Similar to the usage of the Kane Hamiltonian in direct band-gap semiconductors, the new Hamiltonian can be used to study spin properties of electrons in silicon. 相似文献
229.
Samir Alghool Hanan F. Abd El-Halim M. S. Abd El-sadek I. S. Yahia L. A. Wahab 《Journal of Thermal Analysis and Calorimetry》2013,112(2):671-681
Metal complexes of La(III), Ce(IV), and Th(IV), with the amino Schiff base ligand, [N-(2-hydroxybenzyl)-l-methionine acid](H3L), were prepared in the presence of triethylamine as a deprotonating agent. All synthesized compounds were identified and confirmed by mass spectra, elemental analyses, molar conductivities, and spectral analyses (UV–Visible, IR, 1H NMR, and 13CNMR). Conductance measurements suggest the non-electrolytic nature and the complexes were isolated in 1:1 ratios. The thermal decomposition of the complexes was discussed in relation to structure. The data from thermogravimetric analysis clearly indicated that the decomposition of the complexes proceeds in four or five steps and the organic part of the complexes decomposed in one or two intermediates. The decomposition of all complexes ended with metal oxide and carbon residue. The Schiff bases and their complexes were screened for their antibacterial (Escherichia coli, Staphylococcus aureus) and antifungal (Aspergillus flavus and Candida Albicans) activities. 相似文献
230.
Hanan F. Abd El-Halim F. A. Nour El-Dien Gehad G. Mohamed Nehad A. Mohamed 《Journal of Thermal Analysis and Calorimetry》2012,109(2):883-892
Metal complexes having the general composition [MCl2(H2O)2(L)2]·yH2O (where y?=?1?C3, M?=?Mn(II), Cu(II), Co(II), Ni(II), and Zn(II) and L?=?miconazole drug?=?MCNZ) and [MCl2(H2O)2(L)2]Cl·3H2O (where M?=?Cr(III) and Fe(III)) have been synthesized. All the synthesized complexes were identified and confirmed by elemental analyses, IR, diffused reflectance, and thermal analyses (TG and DTA) techniques as well as molar conductivity and magnetic moment measurements. The molar conductance data reveals that bivalent metal complexes are non-electrolytes while Cr(III) and Fe(III) complexes are electrolytes and of 1:1 type. IR spectral studies reveal that MCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole-N. On the basis of magnetic and solid reflectance spectral studies, an octahedral geometry has been assigned for the complexes. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry (TG) and differential thermal analyses (DTA) techniques and the activation thermodynamic parameters are calculated using Coats?CRedfern method. The free MCNZ drug and its complexes were also evaluated against bacterial species (P. aeruginosa, S. aureus, B. subtilis, E. Coli) and fungi (A. fumigatus, P. italicum, and C. albicans) in vitro. The activity data show that the metal complexes have higher biological activity than the parent MCNZ drug. 相似文献