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Hiromu Kurosaki April A. Tucker Sarah E. Iden Shirley M. Sexton Benito D. Gonzalez Govind R. Rao 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1017-1022
Routine monitoring of urine is an effective way to detect occupational intake of radioactive material. Historically, determinations of uranium isotopic ratios have been performed by radiochemical separation followed by alpha spectrometry. With recent advancements in technology, inductively coupled plasma-mass spectrometry (ICP-MS) has become widely available for the determination of trace metals as well as radioactive nuclides with long half-lives, such as 238U in urine. Furthermore, ICP-MS measurements of 238U do not require radiochemical separation since the number of atoms in the sample is determined instead of the number of alpha particles emitted. However, this method does not provide good sensitivity for the determination of 235U due to its shorter half-life. An improved procedure using pre-concentration of uranium and determination by ICP-MS decreases the detection limit by a factor of ten or greater with only slight increase in total analysis time. The method also has the capability of accurately determining the isotopic ratio of the sample, which is very important in cases where enriched or depleted uranium is involved. 相似文献
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Molecular vibrations of C2H2 and C2D2 adsorbed on Pt(111) at 140 K and ∼300K have been measured by high resolution electron energy loss spectroscopy. The comparison
of C2H2 and C2D2 spectra allows an unambiguous assignment of the observed losses to the excitation of C−H bending, C−H stretching, and C−C
stretching modes of nondissociatively adsorbed acetylene. From the relative intensities of losses the hybridisation state
is determined to be nearsp
2. The C−C stretching frequency indicates a C−C bond order of ∼1.8. 相似文献
5.
John Pattinson Gibb Kay Sexton David Watson W. J. Ward T. Egleston O. Pufahl und K. A. Åkerblom 《Fresenius' Journal of Analytical Chemistry》1886,25(1):255-258
Ohne Zusammenfassung 相似文献
6.
The interaction of visible light with surface plasmons in a periodic array of silver channels is studied experimentally and theoretically. Channels of width 130 nm and depth 280 nm on a pitch of 468 nm were fabricated using electron beam lithography. Measurements of the reflectance of the channels show strong absorption for a specific angle of incidence at a given wavelength of the light. It is shown using a simple geometric model that this is consistent with the excitation and propagation of surface plasmons in the deep sub-wavelength channels. A numerical simulation of the electromagnetic fields excited in the channels confirms this result. 相似文献
7.
R.A. Sexton 《Journal of Pure and Applied Algebra》2006,207(2):433-468
Using the category of frames we consider various generalizations of the patch space of a topological space. Some of these constructions are old and some are new. We consider how these variants interact and under what circumstances they agree. 相似文献
8.
Acetonitrile (CH3CN) coordination to a Pt(111) surface has been studied with electron energy loss vibrational spectroscopy (EELS), XPS, thermal desorption and work function measurements. We compare data for the surface states with known acetonitrile coordination complexes. For CH3CN adsorbed on Pt(111) at 100 K, the molecule is rehybridized and adsorbs with the CN bond parallel or slightly inclined to the surface plane in an η2(C, N) configuration. The ν(CN) frequency is 1615 cm?1 and the C ls and N ls binding energies are 284.6 eV and 397.2 eV respectively. By contrast, weakly adsorbed multilayer acetonitrile exhibits a ν(CN) vibrational frequency of 2270 cm?1, and C ls and N ls binding energies of 286.9 eV and 400.1 eV respectively. Both the EELS and XPS results are consistent with rehybridization of the CN triple bond to a double bond with both C and N atoms of the CN group attached to the surface. In addition to this majority η2(C, N) monolayer state, evidence is found for a second, more strongly bound minority molecular state in thermal desorption spectra. As a result of the low coverage of this state, EELS was unable to spectroscopically identify it and we tentatively assign it as an η4(C, N) species associated with accidental step sites. By contrast to the surface complexes, almost all of the known platinum-nitrile coordination complexes are end-bonded via the N lone-pair orbital. Several cases of side-on bonding are known, however, and we compare the results with the known complex Fe3(η2-NCCH3)(CO)9. The difference in the coordinative properties of a Pt(111) surface versus a single Pt atom must be due to the increased ability of multi-atom arrays to back-donate electrons into the π1 system of acetonitrile. Previously published EELS and XPS results for monolayer acetonitrile on Ni(111) and polycrystalline films are almost identical to the present results on Pt(111). We believe that the monolayer of is also an η2(C, N) species, not an end-bonded species previously proposed by Friend, Muetterties and Gland. 相似文献
9.
We have measured the angle and energy dependence of the inelastic cross sections for NH3 chemisorbed on Pt(111). The relative contributions of dipole and nondipole processes in the on-specular intensities were determined. The angular dependence (off-specular scattering) was found to be more useful than the impact energy dependence for discrimination between the two scattering mechanisms. For both molecular states of NH3/Pt(111), strong impact scattering contributions were found in the NH stretching mode intensities. One particular mode, the degenerate stretch [νd(NH)] was selectively excited by impact scattering. The energy dependence showed an enhancement of all of the inelastic intensities at low impact energies (1 eV). This enhancement was found to be a result of a surface reflectivity increase, coupled with an increase in the inelastic cross section. The latter increase is not predicted by dipole theory. Determination of the molecular orientation was not possible, due to the complex contributions of dipole and impact scattering. 相似文献
10.
Comments are made regarding the implementation of a Toeplitz-matrix inversion algorithm described by Bitmead and Anderson in [1]. We show that although the algorithm is asymptotically efficient with O(N(logN)2) operations, it requires a 106×106 matrix to break even with the class of algorithms whose operation count is of the order of O(N2) (as found in [4]). 相似文献