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61.
M. Klein H. Nachtigal M. Hansinger M. Pfitzner N. Chakraborty 《Flow, Turbulence and Combustion》2018,101(4):1173-1187
The flame curvature statistics of turbulent premixed Bunsen flames have been analysed in this paper using a Direct Numerical Simulation (DNS) database of turbulent Bunsen flames at ambient and elevated pressures. In order to be able to perform a large parametric study in terms of pressure, heat release parameter, turbulence conditions and nozzle diameter, a single step Arrhenius type irreversible chemistry has been used for the purpose of computational economy, where thermo-chemical parameters are adjusted to match the behavior of stoichiometric methane-air flames. This analysis focuses on the characterization of the local flame geometry in response to turbulence and hydro-dynamic instability. The shape of the flame front is found to be consistent with existing experimental data. Although the Darrieus Landau instability promotes cusp formation, a qualitatively similar flame morphology can be observed for hydro-dynamically stable flames. A criterion has been suggested for the curvature PDF to become negatively skewed. 相似文献
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Reiser S Brunklaus G Hong JH Chan JC Eckert H Pfitzner A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(18):4228-4233
(CuI)(3)P(4)S(4) is obtained by reaction of stoichiometric amounts of CuI, P, and S in evacuated silica ampoules. The yellow compound consists of monomeric beta-P(4)S(4) cage molecules that are separated by hexagonal columns of CuI. (CuI)(3)P(4)S(4) crystallizes isotypic to (CuI)(3)P(4)Se(4) in the hexagonal system, space group P6(3)cm (no. 185) with a=19.082(3), c=6.691(1) A, V=2109.9(6) A(3), and Z=6. Three of the four phosphorus atoms are bonded to copper, whereas no bonds between copper and sulfur are observed. The two crystallographically distinct copper sites are clearly differentiated by (65)Cu magic-angle spinning (MAS) NMR spectroscopy. Furthermore, an unequivocal assignment of the (31)P MAS-NMR spectra is possible on the basis of homo- and heteronuclear dipole-dipole and scalar interactions. Dipolar coupling to the adjacent quadrupolar spins (63, 65)Cu generates a clear multiplet structure of the peaks attributable to P1 and P2, respectively. Furthermore, the utility of a newly developed two-dimensional NMR technique is illustrated to reveal direct connectivity between P atoms based on ((31)P-(31)P) scalar interactions. 相似文献
64.
A. Pfitzner 《Nuclear Physics A》1967,100(3):673-682
Balashov's resonance approximation is used to calculate the level shifts and widths of the low-lying, negative-parity states in 17O, assuming these states to be 2p-1h structure. It turns out that the coupling to one-particle continuum states is very important not only for the widths but also for the positions of most of the levels. The results prove to be very sensitive to the positions of the single-particle resonances in the (2p, 1f) shell. 相似文献
65.
Geissoschizine (8) is enzymatically converted to 19-epi-ajmalicine (7) first by oxidation to the 4,21-dehydro-intermediate (4) of the heteroyohimbine pathway followed by cyclisation and stereospecific reduction. 相似文献
66.
CuClSe1.53Te0.47 and CuClSe0.56Te1.44 are obtained from the reaction of CuCl, Se, and Te in stoichiometric amounts. Both copper(I) selenium tellurium chlorides are monoclinic, space group P21/n (no. 14) with lattice constants of a = 7.837(1) Å, b = 4.699(1) Å, c = 10.762(2) Å, β = 104.37(2)°, V = 383.9(1) Å3 (CuClSe1.53Te0.47), and a = 8.074(1) Å, b = 4.830(1) Å, c = 10.973(1) Å, β = 103.87(2)°, V = 415.5(1) Å3 (CuClSe0.56Te1.44), and Z = 4. A common feature of these isostructural compounds are heteroatomic strands [YY'] (Y, Y' = chalcogen). These strands are running along [010] and are connected to layers by chains [CuCl]. Vibrational spectra of CuClSe1.53Te0.47, CuClSe0.56Te1.44, CuXTe2 and CuX'Se2 (X = Cl, Br, I; X' = Cl, Br) are analysed with respect to the bonding relations of the chalcogen chains. Modes derived from IR and Raman spectra are assigned by correlation with tri gonal Se and related copper(I) chalcogen halides. Both, X‐ray structural data and an analysis of the chalcogen vibrational modes in IR and Raman spectra, lead to a detailed insight into the ordering phenomena of the chalcogen chains in this type of copper(I) chalcogen halides. 相似文献
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Anika Söldner Julia Zach Melanie Iwanow Dr. Tobias Gärtner Dr. Marc Schlosser Prof. Arno Pfitzner Prof. Burkhard König 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13108-13113
Natural deep eutectic solvents (DESs) dissolve simple metal oxides and are used as a reaction medium to synthesize spinel‐type ferrite nanoparticles MFe2O4 (M=Mg, Zn, Co, Ni). The best results for phase‐pure spinel ferrites are obtained with the DES consisting of choline chloride (ChCl) and maleic acid. By employing DESs, the reactions proceed at much lower temperatures than usual for the respective solid‐phase reactions of the metal oxides and at the same temperatures as synthesis with comparable calcination processes using metal salts. The method therefore reduces the overall required energy for the nanoparticle synthesis. Thermogravimetric analysis shows that the thermolysis process of the eutectic melts in air occurs in one major step. The phase‐pure spinel‐type ferrite particles are thoroughly characterized by X‐ray diffraction, diffuse‐reflectance UV/Vis spectroscopy, and scanning electron microscopy. The properties of the obtained nanoparticles are shown to be comparable to those obtained by other methods, illustrating the potential of natural DESs for processing metal oxides. 相似文献
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