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31.
A. Anastassov Yu. P. Gangrsky B. K. Kul'djanov K. P. Marinova B. N. Markov S. G. Zemlyanoi 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(3):177-181
Isotope shifts and hyperfine structures in three optical transitions of HfI are investigated. Magnetic dipole coupling constant A and electric quadrupole coupling constant B of four atomic levels for both stable odd-even isotopes177Hf and179Hf are determined. Nuclear charge radii changesδ〈r 2〉 of the stable Hf isotopes and182 Hf (T 1/2=9×106 y) are extracted using the standard semiempirical procedure. Strong deviation from muonic atom data onδ〈r 2〉 is observed. The course of theδ〈r 2〉 dependence on mass number indicates changes in nuclear deformation at A=174 and influence of higher order deformations on nuclear shape in this region. 相似文献
32.
Marinova P. Marinov M. Kazakova M. Feodorova Y. Blazheva D. Slavchev A. Sbirkova-Dimitrova H. Sarafian V. Stoyanov N. 《Russian Journal of General Chemistry》2021,91(5):939-946
Russian Journal of General Chemistry - The presented study is devoted to the structural and biological properties of four derivatives of fluorenylspirohydantoin based on experimental data. The... 相似文献
33.
M. Sendova-Vassileva D. Dimova-Malinovska M. Kamenova A. Kakanakova-Georgieva Ts. Marinova 《Journal of luminescence》1998,80(1-4):179-182
Porous silicon (PS) is studied by stepwise peeling of the surface layer to clarify the non-uniformity in the photoluminescence (PL) and correlate it with the in-depth chemical bonding and structure of the 30 μm thick layer. The PL intensity grows by an order of magnitude after the peeling off of the first 10 μm and decreases five times in the next 5 μm while the peak maximum position shifts from 730 to 800 nm. X-ray photoelectron spectroscopy (XPS) measurements show that Si–Si and Si–O bonds are present both on the surface and below, and the preferential oxidation state of silicon changes from 3+ and 4+ on the surface to 1+ and 2+ below 10 μm. Using Raman spectroscopy silicon nanocrystals are shown to exist. Their mean size can be estimated at about 3 nm. These results show that the strongest PL comes from a region in the PS layer where silicon nanocrystallites are surrounded by oxides with a low level of oxidation and not from the strongly oxidized surface layer. 相似文献
34.
Rossitza S. Marinova Raymond J. Spiteri 《Journal of Computational and Applied Mathematics》2010,235(2):460-469
We present a fully implicit finite difference method for the unsteady incompressible Navier-Stokes equations. It is based on the one-step θ-method for discretization in time and a special coordinate splitting (called vectorial operator splitting) for efficiently solving the nonlinear stationary problems for the solution at each new time level. The resulting system is solved in a fully coupled approach that does not require a boundary condition for the pressure. A staggered arrangement of velocity and pressure on a structured Cartesian grid combined with the fully implicit treatment of the boundary conditions helps us to preserve the properties of the differential operators and thus leads to excellent stability of the overall algorithm. The convergence properties of the method are confirmed via numerical experiments. 相似文献
35.
Oxygen adsorption on a Mo(111) surface is investigated at low pressures (10?7 to 10?5 Pa) and room temperature by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS). In agreement with previous studies it is established that the surface is not reconstructed during adsorption and the oxygen forms no ordered structures. On the basis of kinetic and spectroscopy data, the formation of two adsorption states on the surface within 1 monolayer is established. The valence band of a clean surface is studied in detail. An attempt is made to ascribe the peaks obtained to definite d states. The interaction between O2 and Mo(111) is discussed in terms of the results obtained and a comparison with the O2/W(111) system is made. 相似文献
36.
Anife Ahmedova Petja Marinova Gordana Pavlovi? Maya Guncheva Neyko Stoyanov Mariana Mitewa 《Journal of the Iranian Chemical Society》2012,9(3):297-306
A series of seven 2-cinnamoyl-1,3-indandiones and their metal(II) complexes were synthesized and characterized by means of spectroscopic (IR, NMR, electron absorption and emission spectroscopy) and/or single-crystal X-ray diffraction methods. The optical spectra of the organic compounds show very strong absorption in the visible region and weak fluorescence with moderate to strong Stokes shift. The effect of concentration, water addition and metal ion complexation on the optical properties was also studied. In search of potential practical application, the complexation of 2-cinnamoyl-1,3-indandiones with metal(II) ions was investigated. A series of non-charged complexes with Cu(II), Cd(II), Zn(II), Co(II) and Ni(II) was isolated and analyzed by elemental analyses and IR. Most of the complexes show presence of water molecules, most probably coordinated to the metal ion, thus forming octahedral geometry. For the paramagnetic Cu(II) complexes a distorted, flattened tetrahedral structure is proposed, basing on the EPR data. The optical properties of the metal complexes, however, do not differ appreciably from those of the free ligands. 相似文献
37.
38.
Anife Ahmedova Petja Marinova Samuele Ciattini Neyko Stoyanov Michael Springborg Mariana Mitewa 《Structural chemistry》2009,20(1):101-111
The synthesis, structure and spectral properties of a new cinnamoyl derivative of 2-acetyl-1,3-indandione (2AID), p-fluoro-cinnamoyl-1,3-indandione, LH and its metal(II) complexes with Cu(II), Zn(II) and Cd(II), are described. In order to
verify the molecular structure of the free ligand and its metal complexes, model geometries based on the spectroscopic data
were optimized using quantum chemical methods. The experimental spectroscopic data (IR and NMR) of the ligand, LH, complemented
by the calculated ones, show that it exists in the exocyclic enolic form in the gas phase, solution and solid state. Good
quality single crystals of Cd(II) complex were obtained from a DMSO solution and were studied by means of single-crystal X-ray
diffraction. The data show bidentate coordination of the ligand and two DMSO molecules coordinated to the metal centre, thus
forming a complex with octahedral geometry. On the contrary, the spectroscopic data on the amorphous samples indicate a square
planar geometry of the Cu(II) complex and distorted octahedral geometry for Zn(II) and Cd(II) complexes with two water molecules
coordinated to the metal centre. The used quantum chemical method for structure optimization of the transition metal complexes,
B3LYP/LANL2DZ, shows very good agreement with the crystallographic data and, therefore, was also employed for structural determination
for the non-crystalline complexes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
39.
J. Lorenzzi G. Zoulis M. Marinova O. Kim-Hak J.W. Sun N. Jegenyes H. Peyre F. Cauwet P. Chaudouët M. Soueidan D. Carole J. Camassel E.K. Polychroniadis G. Ferro 《Journal of Crystal Growth》2010,312(23):3443-3450
We report on a comparative investigation of the incorporation of group III, IV and V impurities in 3C–SiC heteroepitaxial layers grown by the vapour–liquid–solid (VLS) mechanism on on-axis α-SiC substrates. To this end, various Si-based melts have been used with addition of Al, Ga, Ge and Sn species. Homoepitaxial α-SiC layers grown using Al-based melts were used for comparison purposed for Al incorporation. Nitrogen incorporation depth profile systematically displays an overshoot at the substrate/epilayer interface for all the layers. Ga and Al incorporations follow the same distribution shape as N whereas this is not the case for the isoelectronic impurities Ge and Sn. This suggests some interaction between Ga/Al and N coming from the high bonding energy between the group III and V elements, which does not exist with Ge and Sn. This is why both incorporate as a cluster. A model of incorporation is proposed taking into account metal-N and metal-C bonding energies together with the solid solubility of the corresponding nitrides. 相似文献
40.
Anife Ahmedova Vasil Atanasov Petja Marinova Neyko Stoyanov Mariana Mitewa 《Central European Journal of Chemistry》2009,7(3):429-438
New 2-acyl-1,3-indandione derivatives, compounds 1–4, were obtained by condensation of 2-acetyl-1,3-indandione with benzaldehyde,
thiophene-2-aldehyde, thiophene-3-aldehyde and furane-2-aldehyde, respectively. The structures of the newly synthesized 2-substituted
1,3-indandiones were characterized by means of spectroscopic methods (FT-IR, 1H and 13C NMR, UV-Vis and MS). Based on the obtained results it is suggested that the compounds exist in the exocyclic enolic form.
Mass spectral fragmentation paths are also proposed. In order to verify the possibility for tautomerization processes of the
newly synthesized compounds their absorption spectra were recorded in various solvents. Furthermore, the complexation properties
of the compounds with metal(II) ions were also studied. A series of non-charged complexes with Cu(II), Cd(II), Zn(II), Co(II)
and Ni(II) was isolated and analyzed by elemental analyses and IR. The paramagnetic Cu(II) complexes were studied by EPR and
distorted, flattened tetrahedral structures are predicted. The other metal complexes show the presence of water molecules,
most probably coordinated to the metal ion, thus forming octahedral geometry. Ultimately, the studied properties of the newly
synthesized compounds, 1–4, suggest that they may find application as extracting agents for metal ions, rather than as optical
sensors.
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