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371.
Johnson MA Jensen MT Svensson B Pinto BM 《Journal of the American Chemical Society》2003,125(19):5663-5670
Transferred nuclear Overhauser effect and rotating-frame Overhauser enhancement NMR spectroscopies are used to probe the conformation of a bicyclic sulfonium ion, which is an analogue of the naturally occurring glycosidase inhibitor castanospermine, bound to the enzyme glucoamylase G2. Enzyme inhibition assays indicate that the bicyclic sulfonium ion is a slightly better inhibitor (K(i) = 1.32 mM) of glucoamylase G2 than the naturally occurring sulfonium-ion glycosidase inhibitor, salacinol, with a K(i) value of 1.7 mM. The NMR results are interpreted in terms of the selection by the enzyme of a high-energy conformation of the ligand that is already represented in the ensemble of free-ligand conformations. 相似文献
372.
Tchaplyguine M Marinho RR Gisselbrecht M Schulz J Mårtensson N Sorensen SL de Brito AN Feifel R Ohrwall G Lundwall M Svensson S Björneholm O 《The Journal of chemical physics》2004,120(1):345-356
A new approach for obtaining an estimate of the effective size of the free neutral clusters is proposed. The approach relies on an experimental measure of the surface and interior or "bulk" cluster atoms provided by the x-ray photoelectron spectroscopy and on a model for the attenuation of photoelectrons ejected from the bulk of the cluster as the result of the ionizing irradiation. The experimental part gives the ratio of the electron signal from the bulk cluster atoms to that from the cluster surface atoms for a wide range of cluster sizes and electron kinetic energies. The attenuated response of the bulk atoms is modeled using an exponential law with the cluster size and kinetic-energy-dependent electron escape depth as parameters. For the experimental size range, model-based calculations for Ar, Kr, and Xe clusters are presented. The cluster size estimates obtained from comparison of the model calculations and experimental results agree well with those determined from the parameters of the cluster creation process. The combination of experiment and modeling also makes it possible to estimate the effective escape depth for electron propagation in free clusters. For Ar, Kr, and Xe clusters of varying mean size, absolute determination of the surface and bulk electron binding energies of the core levels used in the experiments has also been made. 相似文献
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377.
L A Svensson 《Acta chemica Scandinavica》1972,26(7):2663-2669
378.
Stefan T. Norberg Göran Svensson Jörgen Albertsson 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(3):225-227
A room-temperature structural model of titanium pyrophosphate, TiP2O7, has been determined from synchrotron X-ray data. The structure consists of TiO6 octahedra and PO4 tetrahedra sharing corners in a three-dimensional network. The PO4 tetrahedra form P2O7 groups connecting the TiO6 octahedra. The 3 × 3 × 3 superstructure differs substantially from the parent AB2O7 structure. The P—O—P bonding angles of the pyrophosphate group are between 141.21 (12) and 144.51 (13)° for those groups not located on the threefold axis. The individual TiO6 octahedra and PO4 tetrahedra are somewhat distorted. 相似文献
379.
O. Travnikova C. Miron M. Bssler R. Feifel M.N. Piancastelli S.L. Sorensen S. Svensson 《Journal of Electron Spectroscopy and Related Phenomena》2009,174(1-3):100
The present work aims at characterizing short-lived C1s(−1)π*(1) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s→π* resonance in the binding energy region 15–19 eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the , and final states. This is explained by (1) the variation in the C–O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s(−1)π*(1) intermediate states can be predicted in analogy with e.g. the N2, CO2 and N2O molecules. 相似文献
380.
Deep level transient spectroscopy (DLTS) has been employed to study electron traps in hydrothermally grown n-type ZnO samples after thermal treatments up to 1500 °C. Schottky barrier contacts were formed by e-beam evaporation of Pd, followed by DLTS and secondary ion mass spectrometry (SIMS) measurements in order to investigate possible correlations between electron traps in the upper part of the band gap and the concentration of the most prominent impurities. The DLTS results show three different levels having energy positions of , , and (Ec denotes the conduction band edge). The SIMS results showed that the most pronounced impurities were Li, Al, Si, Mg, Fe, Mn, and Ni with concentrations up to . A decrease in the level is observed after temperature treatments above 1300 °C, and in the same temperature range the Li concentration drops from ∼1017 to . However, based on absolute concentration values an association between Li and the level can be ruled out. In contrast, the level, which is not stable above 1300 °C, may be associated with Li but further experimental data are needed to substantiate this assignment. The level occurred in selected samples and is presumably impurity-related but no correlation was found with the main impurities detected by SIMS. Except for Li, the concentration of all the impurities remained essentially constant as a function of heat treatment temperature. 相似文献