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51.
An automated system for preparative gas chromatography with capillary columns is described. The effluet from the capillary column is switched to the FID detector or to the traps by means of a Live-T switching device. The pneumatics is controlled by a microprocessor so that repetitive sampling can be performed over a period of days in order to enrich sufficient amount of material for NMR or other spectroscopic methods. The effluent containing the compounds is collected in glass tubes filled with column packing material (e.g. Chromosorb coated with 3% OV - 101, crosslinked). The trap temperatue can be adjusted from + 20°C to ? 80°C, depending on the trapping material and volatility of trapped substances. The analysis of enriched substances or chromatographic fractions can be performed by thermal desorption of the same traps or by solven elution. The recovery of enriched substances is higher than 90%. High capacity and resolution for enrichment of trace components are obtained with the aid of a double column-double oven system. Examples of such applications are given. 相似文献
52.
Afrati T Zaleski CM Dendrinou-Samara C Mezei G Kampf JW Pecoraro VL Kessissoglou DP 《Dalton transactions (Cambridge, England : 2003)》2007,(25):2658-2668
The use of di-2-pyridyl ketone oxime (Hpko)/X- "blends" (X- = OH-, Cl-, ClO4-) in copper chemistry has yielded neutral binuclear and cationic trinuclear, pentanuclear or hexanuclear complexes. Various synthetic procedures have led to the synthesis of compounds [Cu5(pko)7].[ClO4]3.2CH3OH.2H2O (1), [Cu3(pko)3(OH)(Cl)]2[Ph4B]2.4DMF.2H2O (2), [Cu2(pko)4] (3), {[Cu6(pko)6ClO4(CH3CN)6][Cu6(pko)6(ClO4)3(CH3CN)4]}.8ClO4.14CH3CN.H2O (4). The structures of the complexes have been determined by single-crystal X-ray crystallography. 相似文献
53.
A. Kamzin B. Stahl R. Gellert G. Klingelhofer E. Kankeleit L. G. Ol’khovik D. Vcherashnii 《Physics of the Solid State》2000,42(5):897-902
The magnetic properties of a 50-to 2-nm-thick surface layer in hexagonal ferrite BaFe12O19 single crystals are investigated for the first time. Measurements are made on a conversion-electron Mössbauer spectrometer constructed on the basis of a unique ultrahigh-vacuum magnetostatic electron analyzer of the “orange” type. An analysis of the experimental Mössbauer spectra obtained from the surface layer of BaFe12O19 50-to 2-nm-thick single crystals reveals that (1) the spectral line widths are close to the natural widths of Mössbauer lines and neither changes nor a set of the values of effective magnetic fields, as well as a paramagnetic state of iron ions, could appear due to a defect such as the “surface,” and (2) the experimental spectra are best described only under the assumption that the surface of a hexaferrite BaFe12O19 single crystal contains a 2-nm-thick layer, in which the magnetic moments of iron ions are deflected through ~20° from the crystallographic C axis along which the magnetic moments of ions located in the bulk of the crystal are oriented. 相似文献
54.
Uwe Gellert 《International Journal of Mathematical Education in Science & Technology》2013,44(3):365-374
Developments in mathematics, technology, science, culture and society are closely interwoven with each other. Beyond that, these interrelations tend to be very complex due to the multiplicity of factors involved. In this contribution, three examples from the human story are analysed in order to sensitize for possible characteristics of the interrelation. For the historical cases of early Mesopotamia, the Inca state and Renaissance Italy, it is demonstrated how specific socio-cultural conditions affect the development of mathematics and technology as well as their use. These findings lead to questions about our use of mathematics and the ways in which mathematics, society, technology, culture and science may be linked, today. 相似文献
55.
A. S. Kamzin B. Stahl R. Gellert M. Müller E. Kankeleit D. B. Vcherashnii 《Physics of the Solid State》2000,42(9):1691-1695
First measurements of the effective magnetic fields as a function of the depth at which the iron ions are in the surface layer of α-Fe2O3 and FeBO3 single crystals are reported. The method used is the depth-selective conversion-electron Mössbauer spectroscopy. An analysis of experimental spectra revealed that the magnetic properties of the crystal surface vary smoothly from the bulk to surface characteristics within a layer ~100 nm thick. The layers lying below ~100 nm from the surface are similar in properties to the bulk of the crystal, and their spectra consist of narrow lines. The spectral linewidths increase smoothly as one approaches the crystal surface. The spectra obtained from a ~10-nm thick surface layer consist of broad lines indicating a broad distribution of effective magnetic fields. Calculations show that the field distribution width in this layer is δ=2.1(3) T, for an average value H eff=32.2(4) T. It has been experimentally established that, at room temperature (291 K), the effective magnetic fields smoothly decrease as one approaches the crystal surface. The effective fields in a 2.4(9)-nm surface layer of α-Fe2O3 crystals are lower by 0.7(2)% than the fields at the ion nuclei in the bulk of the sample. In the case of FeBO3, the effective fields decrease by 1.2(3)% in a surface layer 4.9(9) nm thick. 相似文献
56.
A. S. Kamzin B. Stahl R. Gellert M. Muller E. Kankeleit D. B. Vcherashnii 《JETP Letters》2000,71(4):134-137
Depth-selective conversion electron Mössbauer spectroscopy was used to study magnetic properties of the thin surface layers of the α-Fe2O3 and FeBO3 single crystals. An analysis of the experimental spectra indicates that the magnetic properties of the layers at a depth of more than ~100 nm from the surface are similar to the properties of crystal bulk, and the corresponding spectra consist of narrow lines. The lines gradually broaden as the crystal surface is approached. The spectra of the ~10-nm-thick surface layers consist of broad lines, indicating a wide distribution δ=2.1 T of the effective magnetic field about its mean value of 32.2(4) T. The experimental spectra were used to determine the effective magnetic fields (H eff) for the iron ions situated in the surface layers of thickness ~100 nm. The effective fields in these layers were found to gradually decrease at room temperature (291 K) as the crystal surface was approached. The H eff values in the 2.4(9)-nm-thick surface layer of the α-Fe2O3 crystal and 4.9(9)-nm layer of FeBO3 are 0.7(2) and 1.2(3)%, respectively, smaller than for the nuclei of the ions in the bulk of these crystals. 相似文献
57.
B. Gellert 《Optics Communications》1983,46(2):106-111
Ion acoustic harmonic generation is a heavy damping mechanism of stimulated Brillouin scattering. The theory of first harmonic ion wave production is extended to frequencies four times the fundamental. Besides, the corresponding set of 6 differential equations is solved numerically for the steady state, and spatial solutions of the ion wave amplitudes are obtained. By varying typical parameters of laser plasma interaction experiments some characteristics properties are gained which might be of use for comparison with experiments. 相似文献
58.
B. Gellert 《Physics letters. A》1983,96(1):16-20
The theory of ion acoustic harmonic production with stimulated Brillouin scattering is extended up to the third harmonic. Stationary spatial solutions are given for normalized ion acoustic wave amplitudes and characteristic properties derived, which may serve experimentalists for future detailed investigations. 相似文献
59.
60.
R. B. Alexander E. J. Ansaldo B. I. Deutch J. Gellert L. C. Feldman 《Hyperfine Interactions》1977,3(1):45-62
A combined study has been made of the lattice location and hyperfine field of Yb implanted into Fe single crystals. The location has been determined by ion channeling and back-scattering, the hyperfine field by perturbed angular correlation (PAC) measurements on169Yb (decaying to excited states in169Tm). The channeling experiments indicate that initially about 60% of the Yb atoms occupy substitutional sites in the Fe lattice, while the remaining atoms are not in any specific crystallographic site. On annealing, Yb migrates from substitutional to non-substitutional sites. No Yb atoms remain substitutional after a 600°C anneal. By making PAC measurements at two temperatures for two - cascades in169Tm, it is found that the PAC pattern can be described using a combined static and time-dependent magnetic interaction. The PAC results show that the average hyperfine field and relaxation parameter decrease on annealing, and that the field disappears after a 600°C anneal. The correlation between the location and the hyperfine field is discussed. A comparison of the results with previous Mössbauer results for151Gd implanted in Fe, together with relaxation parameter measurements on a169Yb2O3 source, suggests that the non-substitutional Yb is internally oxidized in the Fe host.Work partly carried out while at the Clarendon Laboratory, Oxford, England and Nuclear Physics Division, AERE, Harwell, England. 相似文献