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461.
Pratibha Sharma Renu Tomar Pankaj Sharma Radha Tomar 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):329-336
Summary Sorption
and desorption of UO22+, Th4+ and Ru3+
on the synthetic analogue of the mica mineral muscovite has been studied by a
batch technique. The synthesized gel was characterized by XRD, EDXRFS, FTIR,
TGA and SEM and was found to have a composition K1.4Al4.2(Si6Al2O20)(OH)4
. 2H2O. Different parameters like acid concentration, contact
time, amount of gel, composition of gel: OPC admixture, effect of temperature,
desorption of metal ions from loaded muscovite and effect on crystal morphology
due to loading of metal ions were studied. The results has been expressed in
terms of distribution coefficient (Kd).</p>
</p> 相似文献
462.
S. Sodaye K. Sudarshan B.S. Tomar A. Goswami S. Mukherjee K. Mahata 《The European Physical Journal A - Hadrons and Nuclei》2002,14(3):371-376
Kinetic-energy spectra and angular distribution of projectile-like fragments have been measured in the reaction of 84 MeV
12C on 169Tm, using the surface barrier silicon-based ΔE-E telescopes. The fragments close to the projectile show typical spectra of quasi-elastic transfer reactions, which were found
to be in agreement with the calculations based on the direct surface transfer reaction model. A significant cross-section
of fast alpha-particles was found at forward angles, reminiscent of incomplete fusion reactions, which could be explained
in terms of the direct surface transfer reaction model after taking into account the level density of continuum states in
the heavy reaction product. The results have been explained in terms of the continuous evolution of the reaction mechanism
as a function of the mass transfer.
Received: 13 March 2002 / Accepted: 3 May 2002 相似文献
463.
We compared the effectiveness of different forcefields for computing the density of CHNO explosives using crystal packing methodology. Densities obtained for 68 CHNO explosives of various sizes vary in chemical nature, contain different functionalities, and are compared with the experimental data. The predicted densities with Dreiding forcefield for 84% explosives without an aromatic ring in the structure (NonAr-Explosives) gave deviation within 5%. While the predicted densities with PCFF forcefield for 83% of explosives containing aromatic ring in the structure (Ar-Explosives) found within 4% deviation, the computed densities using various forcefields judged with experimental data indicate that choice of forcefield is crucial for precise density prediction. This study will be valuable in selecting forcefield for crystal packing calculations and directing research efforts towards the design of denser CHNO energetic materials. Please be informed that Graphical Abstract is not allowed per journal style. Thus, the graphical abstract provided was not captured.Author agrees with the comment. 相似文献
464.
465.
Photoluminescence studies of pure and Dy3+, Eu3+ doped Sr2CeO4 compounds are presented by oxalate precipitation method for solid state lighting. The prepared samples also characterized by XRD, SEM (EDS) and FTIR spectroscopy. The pure Sr2CeO4 compound displays a broad band in its emission spectrum when excited with 280 nm wavelength, which peaks centered at 488 nm, which is due to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce4+ ions. Emission spectra of Sr2CeO4 with different concentration of Dy3+ ions under near UV radiation excitation, shows that intensity of luminescence spectra is found to be affected by Dy3+ ions, and it increases with adding some percentages of Dy3+ ions. The maximum doping concentration for quenching is found to be Dy3+?=?0.2 mol % to Sr2+ions. The observed broad spectrum from 400 to 560 nm is mainly due to CT transitions in Sr2CeO4 matrix and some fractional contribution of transitions between 4F9/2 → 6H15/2 of Dy3+ ions. Secondly the effect of Eu3+ doping at the Sr2+ site in Sr2CeO4, have been studied. The results obtained by doping Eu3+ concentrations (0.2 mol% to 1.5 mol%), the observed excitation and emission spectra reveal excellent energy transfer between Ce4+ and Eu3+. The phenomena of concentration quenching are explained on the basis of electron phonon coupling and multipolar interaction. This energy transfer generates white light with a color tuning from blue to red, the tuning being dependent on the Eu3+ concentration. The results establish that the compound Sr2CeO4 with Eu3+?=?1 mol% is an efficient “single host lattice” for the generation of white lights under near UV-LED and blue LED irradiation. The commission internationale de I’Eclairage (CIE) coordinates were calculated by Spectrophotometric method using the spectral energy distribution of prepared phosphors. 相似文献
466.
Ashwani Kumar C. Nayak P. Rajput R. K. Mishra D. Bhattacharyya C. P. Kaushik B. S. Tomar 《Hyperfine Interactions》2016,237(1):143
Gamma radiation induced changes in local structure around the probe atom (Hafnium) were investigated in sodium barium borosilicate (NBS) glass, used for immobilization of high level liquid waste generated from the reprocessing plant at Trombay, Mumbai. The (NBS) glass was doped with 181Hf as a probe for time differential perturbed angular correlation (TDPAC) spectroscopy studies, while for studies using extended X-ray absorption fine structure (EXAFS) spectroscopy, the same was doped with 0.5 and 2 % (mole %) hafnium oxide. The irradiated as well as un-irradiated glass samples were studied by TDPAC and EXAFS techniques to obtain information about the changes (if any) around the probe atom due to gamma irradiation. TDPAC spectra of unirradiated and irradiated glasses were similar and reminescent of amorphous materials, indicating negligible effect of gamma radiation on the microstructure around Hafnium probe atom, though the quaqdrupole interaction frequency (ω Q) and asymmetry parameter (η) did show a marginal decrease in the irradiated glass compared to that in the unirradiated glass. EXAFS measurements showed a slight decrease in the Hf-O bond distance upon gamma irradiation of Hf doped NBS glass indicating densification of the glass matrix, while the cordination number around hafnium remains unchanged. 相似文献
467.
Jain V Jimenez A Maldarelli C Tu RS 《Langmuir : the ACS journal of surfaces and colloids》2008,24(18):9923-9928
We describe a rationally designed peptide with tunable surface activity, where the dynamics of surface activity are an outcome of helical folding. Our rationally designed model peptide is surface-active only as an alpha-helix. We apply circular dichroism to show that the folded population can be controlled with changes in electrolyte concentration, and we apply pendant bubble tensiometry to explore dynamic surfactant activity. This study shows a peptide that responds to environmental stimuli with dynamic folding and surface activity. Extending this concept to selective binding peptides will lead to new tools, where dynamic surface activity is coupled to targeted binding. 相似文献
468.
469.
R. Tomar D. Sharma S. Verma P. Sharma 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(1):112-118
The effect of temperature on the sorption behavior of a synthesized gel structurally close to the fluorine mica mineral, sodium
potassium fluorophologopite, was studied for the heavy metal ions Cd2+, Hg2+, and Pb2+. The synthesized gel was characterized by X-ray powder pattern, energy dispersive spectrometry, infrared spectroscopy, and
thermogravimetric analysis and was found to have the composition Na0.5K0.5Mg(AlSi3O10)F2·6H2O. The effect of temperature on sorption was studied with respect to varying concentrations of metal ions. The overall sorption
capacity of the synthesized gel was found to depend on the number of ion active groups per unit weight of the material. The
data were expressed in terms of distribution coefficients (K
d). Sorption data followed Freundlich adsorption isotherms. Studies showed that sorption decreased as the concentration of
metal ions increased and increased as the temperature grew, which was evidence that the process was endothermic.
The text was submitted by the authors in English. 相似文献
470.
McAllister KA Zou H Cochran FV Bender GM Senes A Fry HC Nanda V Keenan PA Lear JD Saven JG Therien MJ Blasie JK DeGrado WF 《Journal of the American Chemical Society》2008,130(36):11921-11927
We have developed a computational design strategy based on the alpha-helical coiled-coil to generate modular peptide motifs capable of assembling into metalloporphyrin arrays of varying lengths. The current study highlights the extension of a two-metalloporphyrin array to a four-metalloporphyrin array through the incorporation of a coiled-coil repeat unit. Molecular dynamics simulations demonstrate that the initial design evolves rapidly to a stable structure with a small rmsd compared to the original model. Biophysical characterization reveals elongated proteins of the desired length, correct cofactor stoichiometry, and cofactor specificity. The successful extension of the two-porphyrin array demonstrates how this methodology serves as a foundation to create linear assemblies of organized electrically and optically responsive cofactors. 相似文献