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C.J. van der Beek S. Demirdis M. Konczykowski Y. Fasano N.R. Cejas Bolecek H. Pastoriza D. Colson F. Rullier-Albenque 《Physica B: Condensed Matter》2012,407(11):1746-1749
The pinning of quantized flux lines, or vortices, in the mixed state is used to quantify the effect of impurities in iron-based superconductors (IBS). Disorder at two length scales is relevant in these materials. Strong flux pinning resulting from nm-scale heterogeneity of the superconducting properties leads to the very disordered vortex ensembles observed in the IBS, and to the pronounced maximum in the critical current density jc at low magnetic fields. Disorder at the atomic scale, most likely induced by the dopant atoms, leads to “weak collective pinning” and a magnetic field-independent contribution jccoll. The latter allows one to estimate quasiparticle scattering rates. 相似文献
23.
E. R. Colson 《Chromatographia》1991,32(1-2):95-97
Summary The functions of gas sample injection and column backflushing have been combined in a chromatographic system incorporating switching valves only of the three port solenoid type, installed away from injected sample contact. The system pressures are dynamically adjusted during analytic cycles by a simple dome-loaded regulator network. A sulfur analysis (natural gas odorant) application is demonstrated which also includes a foreflush-to-vent sidestream. The coefficient of variation found for the target analytes was less than 0.8%. 相似文献
24.
Engel S Skoumbourdis AP Childress J Neumann S Deschamps JR Thomas CJ Colson AO Costanzi S Gershengorn MC 《Journal of the American Chemical Society》2008,130(15):5115-5123
Virtual screening has become a major focus of bioactive small molecule lead identification, and reports of agonists and antagonists discovered via virtual methods are becoming more frequent. G protein-coupled receptors (GPCRs) are the one class of protein targets for which success with this approach has been limited. This is likely due to the paucity of detailed experimental information describing GPCR structure and the intrinsic function-associated structural flexibility of GPCRs which present major challenges in the application of receptor-based virtual screening. Here we describe an in silico methodology that diminishes the effects of structural uncertainty, allowing for more inclusive representation of a potential docking interaction with exogenous ligands. Using this approach, we screened one million compounds from a virtual database, and a diverse subgroup of 100 compounds was selected, leading to experimental identification of five structurally diverse antagonists of the thyrotropin-releasing hormone receptors (TRH-R1 and TRH-R2). The chirality of the most potent chemotype was demonstrated to be important in its binding affinity to TRH receptors; the most potent stereoisomer was noted to have a 13-fold selectivity for TRH-R1 over TRH-R2. A comprehensive mutational analysis of key amino acid residues that form the putative binding pocket of TRH receptors further verified the binding modality of these small molecule antagonists. The described virtual screening approach may prove applicable in the search for novel small molecule agonists and antagonists of other GPCRs. 相似文献
25.
Rullier-Albenque F Tourbot R Alloul H Lejay P Colson D Forget A 《Physical review letters》2006,96(6):067002
We have studied the influence of disorder induced by electron irradiation on the Nernst effect in optimally and underdoped YBa2Cu3O(7-delta) single crystals. The fluctuation regime above T(c) expands significantly with disorder, indicating that the T(c) decrease is partly due to the induced loss of phase coherence. In pure crystals the temperature extension of the Nernst signal is found to be narrow whatever the hole doping, contrary to data reported in the low-T(c) cuprate families. Our results show that the presence of intrinsic disorder can explain the enhanced range of the Nernst signal found in the pseudogap phase of the latter compounds. 相似文献
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The high-resolution (0.06 cm?1) FT-IR spectra of pyridine and pyridine-d5 at various path lengths (up to 10 m) have been obtained. These spectra reveal many new features that were not observed before. For example, the observation of many difference bands allows accurate determination of vibrational term values of some inactive and/or weak fundamental vibrations. The five CH stretching modes have been resolved for the first time. Frequency accuracy and internal consistency (since only high-resolution FT-IR data are used) are essential to the present analysis which provides accurate, isolated molecule term values for most of the fundamental vibrations of pyridine and pyridine-d5. These results will be useful for more accurate force field analyses and serve as a guide for future, higher-resolution rotational studies for which the perturbations can now be predicted with more certainty. 相似文献
28.
We report electronic Raman scattering from Ni-substituted YBa2Cu3O6.95 single crystals with T(c) ranging from 92.5 to 78 K. The fully symmetrical A(1g) channel and the B(1g) channel which is sensitive to the d(x(2)-y(2)) gap maximum have been explored. The energy of the B(1g) pair-breaking peak remains constant under Ni doping while the energy of the A(1g) peak scales with T(c) ( E(A(1g))/k(B)T(c) = 5). Our data show that the A(1g) peak tracks the magnetic resonance peak observed in inelastic neutron scattering yielding a key explanation to the long-standing problem of the origin of the A(1g) peak. 相似文献
29.
G. Le Bras P. BonvilleD. Colson A. ForgetN. Genand-Riondet R. Tourbot 《Physica B: Condensed Matter》2011,406(8):1492-1495
We have performed magnetization and magnetocapacitance measurements on ceramic samples of the multiferroic series Bi1−xLaxFeO3 for 0≤x≤.0.25. We show that doping with La reduces the transition magnetic field from the spatially modulated state to a homogenous one and increases the magnetocapacitance, these effects being the strongest for x=0.15, which is the highest concentration for maintaining the non-centrosymmetric rhomboedral structure (R3c) of BiFeO3. For highest La content (x≥0.17), analysis of the XRD patterns shows that the lattice symmetry gradually changes to orthorhombic (C222), giving rise to an enhancement of the latent magnetization and to a drop of the magnetodielectric constant. 相似文献
30.
The phosphorescence spectra of the C6H6C6H5D1p-C6H4D2symp-C6H3D3, C6D6 and 13CC5D in a borazine host crystal are analyzed at high resolution. The spectral lines are sharp (~2 cm?1 wide) indicating that the impurity molecules occupy a unique site in the borazine lattice which is probably substitutional. The phonon sidebands are weak,giving clean, well-resolved spectra much like those of isotopic mixed crystals. In contrast, however, the crystal field effects on the ground state vibrational levels are much smaller than those found for isotopic mixed crystals. The gas-to-crystal shifts are very small, the vibrational degeneracies are not removed and orientational splittings are only observable for a few select vibrational levels. For most vibrational levels and for the derivation of selection rules one can asume the effective crystal site symmetry to be D3d. The data provide the first conclusive evidence that the splitting observed in the benzene phosphorescence spectrum results from a distortion of the molecule when excited to the zeroth vibrational level of the T1 state. Furthermore, the data suggest that the distortion is intrinsic in nature (i.e.,is not caused by the crystal field). 相似文献