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1.
The optical absorption spectrum of Ni2+ ion doped in lecontite (sodium ammonium sulphate dihydrate) single crystal has been studied at room and liquid air temperatures. All the bands could be assigned assumingO h symmetry for the Ni2+ ion in the crystal. The splitting of3 T 1g (F) band at liquid air temperature has been attributed to spin-orbit interaction. The crystal field and spin-orbit parameters derived areD q=1000 cm?1;B=740 cm?1;C/B=4.27 and ζ=600 cm?1. All the bands observed show a blue shift when the crystal was cooled to liquid air temperature. 相似文献
2.
The optical absorption spectrum of Ni2+ ion doped in ammonium zinc sulphate has been studied at room and liquid air temperatures. From the nature and the positions
of the bands a successful interpretation of all the bands could be made assumingO
h
symmetry for the Ni2+ ion in the crystal. The fine splitting of the3
T
1
1 band at liquid air temperature has been successfully interpreted to be due to spin-orbit interaction. The crystal field and
spin-orbit parameters derived areDq=1000 cm−1;B=750 cm−1;C=3.45B andξ=600 cm−1. 相似文献
3.
Results of the optical absorption spectrum of VO2+ ion doped in caesium cadmium sulphate hexahydrate studied at room (300 K) and liquid nitrogen (77 K) temperatures are reported. The site symmetry of the ion is found to be C4ν. Correlating the optical and ESR spectral data, the molecular orbital coefficients are evaluated. 相似文献
4.
Optical and EPR measurements are carried out on shattuckite, a copper bearing silicate. The EPR spectrum observed at 120 K reveales hyperfine structure for parallel and perpendicular components. The measured values are g6 = 2.402, g⊥ = 2.038, A6 = 112 × 10-4 cm-1 and A⊥ = 49.5 × 10-4 cm-1 and they indicate a tetragonal distortion for the Cu2+ion. Further, the constants P and K are evaluated and found to be 0.014 cm-1 and 0.0112 respectively. The bands observed at 8160, 13330 and 16125 cm-1 are assigned to the electronic states of Cu2+, in a crystal field subjected to tetragonal (C4V) distortion. The crystal field parameters evaluated are Dq = -1333, Ds = -1565 and Dt = -380 cm-1. Correlating the EPR and optical data, the orbital reduction factors are calculated as k6 = 0.89 and k⊥ = 0.59. It is confirmed from EPR and optical studies that the Cu2+ion in shattuckite is sited in an elongated octahedron. Similar studies are carried out for plancheite. The observed optical absorption spectrum of plancheite is attributed to Cu2+ sited in an elongated octahedron and tetragonal field parameters are evaluated. 相似文献
5.
Shashank Vummidi Lakshman Salil Mohan Edward L. Dreizin Mirko Schoenitz 《Journal of Thermal Analysis and Calorimetry》2014,115(1):609-620
The thermal decomposition kinetics of a synthetic K–H3O jarosite analog was determined from thermogravimetric analysis at various heating rates in air. A thermal decomposition mechanism was proposed based on X-ray analysis of partially decomposed material and distinct features observed during thermal decomposition analysis. The decomposition path is complex. The material was treated as a composite of K-jarosite, H3O-jarosite, and a “vacancy component”. The evolution of (OH)? and SO3 from these individual components was modeled. The decomposition is broken into subreactions according to distinct features in the thermoanalytical measurements. The subreactions are arranged sequentially and in parallel according to the evolution of the participating phases. A set of associated apparent activation energies was determined using isoconversion analysis. Kinetic triplets were assigned to each subreaction. A reasonable match with the observed decomposition was achieved by varying pre-exponential factors. 相似文献
6.
Single crystals of cobalt — doped ammonium perchlorate were grown at room temperature. The electronic absorption bands observed at room and liquid air temperatures have been assigned transitions from the ground4T1(F) state to the excited4T2(F),4A2(F),2T1(G) and4T1(P) states. The crystal parameters derived areDq=880 cm–1,B=865 cm–1 andC= 4·63B.The authors wish to express their thanks to the authorities of the Indian Institute of Science, Bangalore for kind permission to use their spectrophotometer. Two of the authors (B. C. V.Reddy and J. L.Rao) express their greatful thanks to the council of scientific and Industrial Research (New Delhi) for financial assistance. 相似文献
7.
Pd-catalyzed coupling of the axially constrained, less reactive benzo[a]pyrene bay-region amino benzoates, derived from the tetrahydro and diol epoxides, with C-6 and C-2 halopurine deoxynucleosides offers an efficient approach to the synthesis of the corresponding nucleoside-epoxide adducts. Also reported are the first examples involving the coupling of a 6-chloropurine deoxynucleoside with these amines, a reaction that is difficult by direct halide displacement. Certain mechanistic aspects of this metal-catalyzed C-N bond formation are also discussed. [reaction--see text] 相似文献
8.
Lakshman MK Ngassa FN Bae S Buchanan DG Hahn HG Mah H 《The Journal of organic chemistry》2003,68(15):6020-6030
Single-electron oxidation of the carcinogenic hydrocarbon benzo[a]pyrene (BaP) is thought to result in a radical cation intermediate and this species has been proposed to cause alkylation at the nitrogens of the purine nucleobases. Although several different nucleoside adducts have been isolated as arising from this mode of metabolic activation, there are no selective, total syntheses of the stable exocyclic amino group adducts formed by the single-electron oxidation of any hydrocarbon with the purine 2'-deoxynucleosides to date. In this paper we disclose the synthesis of the model adducts N(6)-(1-pyrenyl)-2'-deoxyadenosine and N(2)-(1-pyrenyl)-2'-deoxyguanosine as well as the first synthesis of the carcinogen-linked nucleoside derivatives N(6)-(6-benzo[a]pyrenyl)-2'-deoxyadenosine and N(2)-(6-benzo[a]pyrenyl)-2'-deoxyguanosine via a palladium-mediated C-N bond formation. Two different coupling strategies were attempted: coupling of an aryl bromide with a suitably protected nucleoside and the coupling of an arylamine with a suitable halonucleoside. The former had somewhat limited applicability in that only N(6)-(1-pyrenyl)-2'-deoxyadenosine was prepared by this method; on the other hand, the latter was more general. However, there are noteworthy differences in the amination reactions at the C-6 and C-2 positions. Reactions at the C-6 resulted in the competing formation of a 1:2 amine-nucleoside adduct in addition to the desired monoaryl nucleoside. Such a dimer formation was not observed at the C-2. The C-2 adducts, however, displayed an interesting conformational behavior. 相似文献
9.
S.V.J. Lakshman S. Buddhudu 《Journal of Quantitative Spectroscopy & Radiative Transfer》1980,24(3):251-257
The values of the Slater-Condon (F2, F4, F6), Racah (E1, E2, E3) and Lande ξ4f coefficients the nephelauxetic ratio (β), the bonding parameter (σ), and the Judd-Ofelt intensity (Tλ) parameters have been calculated from the reported absorption spectra of Pr3+, Nd3+, and Er3+ ions in an aprotic solvent SeOCl2 acidified with antimony pentachloride. The nature of the bonding is suggested to be covalent for praseodymium, neodymium and erbium ions in the laser liquid in view of the magnitude of the respective bonding parameters. 相似文献
10.
The electronic absorption spectrum of the Fe2+ ion doped in ammonium chloride has been studied at room and liquid air temperatures. The observed bands have been assigned transitions from the ground 6A1g(S) state to the excited 4A1g(4Eg), 4T1g(G) and 4T2g(G) states. The cubic field approximation with Dq = 675 cm?1, B = 645 cm?1 and C = 4.4 B is found to give a good fit to the observed band positions.It is further concluded that the site symmetry of the Fe3+ ion in the crystal is lowered from Oh to C4v symmetry at liquid air temperature. 相似文献