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961.
The influence of the physical properties of the membrane layer of a soft particle, which comprises a rigid core and a porous membrane layer, on its electrophoretic behavior, is investigated. Because that influence was almost always neglected in the previous studies, the corresponding results can be unrealistic. The applicability of the model proposed is verified by the available theoretical and experimental results. The electrophoretic mobility of the particle under various conditions is simulated through varying the dielectric constant, the thickness, and the drag coefficient of the membrane layer, and the bulk ionic concentration. We show that under typical conditions, the deviation in the electrophoretic mobility arising from assuming that the dielectric constant of the membrane layer is the same as that of the bulk liquid phase can be in the order of 50%. In addition, the thicker the membrane layer and/or the higher the bulk ionic concentration, the larger the deviation. If the surface of the core of the particle is charged, as in the case of inorganic particles covered by an artificial membrane layer, the deviation at constant core surface potential is larger than that under other types of charged conditions. However, if the surface of the core is uncharged, as in the case of biocolloids, then that deviation becomes negligible. These findings are of fundamental significance to theoreticians in their analysis on the electrokinetic behaviors of soft particles, and to experimentalists in the interpretation of their data. 相似文献
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965.
Chen CL Dong CL Chen JL Guo JH Yang WL Hsu CC Yeh KW Huang TW Mok BH Chan TS Lee JF Chang CL Rao SM Wu MK 《Physical chemistry chemical physics : PCCP》2011,13(34):15666-15672
Critical issues concerning emerging Fe-based superconductors include the degree of electron correlation and the origin of the superconductivity. X-Ray absorption spectra (XAS) and resonant inelastic X-ray scattering spectra (RIXS) of FeSe(1-x)Te(x) (x = 0-1) single crystals were obtained to study their electronic properties that relate to electron correlation and superconductivity. The linewidth of Fe L(2,3)-edges XAS of FeSe(1-x)Te(x) is narrower than that of Fe-pnictides, revealing the difference between their hybridization effects and localization character and those of other Fe-pnictides. While no significant differences exist between the Fe L-edge XAS and RIXS of FeSe(1-x)Te(x) and those of Fe-pnictides, Se K-edge and Te K-edge XAS exhibit substantial edge shift, suggesting that the superconductivity in an Fe-Se superconductor is strongly associated with the ligand states. A comparison of the Se K-edge and Te K-edge spectra reveals that the charge transfer may occur between Se and Te. Given the Coulomb interaction and the bandwidth, the spectral results indicate that FeSe(1-x)Te(x) is unlikely to be a weakly correlated system unlike the Fe-pnictides of the "1111" and "122" families. The spectral results further demonstrate that superconductivity in this class of Fe-based compounds is strongly associated with the ligand 4p hole state. 相似文献
966.
Aggregation of carbon nanotubes reduces quantum efficiency and the phenomenon is found to be related to photocurrent leakage through oxygenated lattices acting as low barrier intertube channels. This outcome is supported by calculation and optical excitation experiments. 相似文献
967.
The charge mobility is a key property in many electro-optical materials, with charge transfer (CT) taking place in a solid matrix of molecules. Large intermolecular electronic interaction is one of the key factors for a good CT rate, which is dependent on both intra- and intermolecular structures. The connection of the molecular structure with the intermolecular CT property would facilitate the search for a new material with desirable CT property, but currently it is still quite limited by the lack of knowledge for intermolecular configurations. In the present work, we study factors influencing the intermolecular configurations, and subsequently the CT property, in tris(8-hydroxyquinolinato) aluminium(III) (AlQ(3)) from all currently available crystal structures. We found that there exists a pair of CH-π interactions in a good majority of the π-π stacked bimolecular configurations. Such CH-π and π-π interacting structures are also seen in the crystal structures of many other similar molecules. With both experimental and simulated structures, we show that the CH-π interaction stabilizes the bimolecular configurations, and drives the structure towards a region with a higher electron transfer coupling and lower hole transfer coupling. This effect likely affects the electron transport property of AlQ(3), since it is consistent with recent experimental results, where AlQ(3) analogs with their CH-π interaction blocked either require a higher operating voltage in light-emitting devices [Sapochak et al., J. Am. Chem. Soc., 2001, 123, 6300], or become bipolar in their charge mobilities [Liao et al., J. Am. Chem. Soc., 2009, 131, 763]. CH-π interaction is commonly seen in aromatic molecules, which are frequently used as building blocks in molecules for electro-optical applications. Our work points out a possible way to enhance the desired CT property in the design of new materials. 相似文献
968.
Wu LC Hsu CW Chuang YC Lee GH Tsai YC Wang Y 《The journal of physical chemistry. A》2011,115(45):12602-12615
A combined experimental and theoretical charge density study on a quintuply bonded dichromium complex, Cr(2)(dipp)(2) (dipp = (Ar)NC(H)N(Ar) and Ar = 2,6-i-Pr(2)-C(6)H(3)), is performed. Two dipp ligands are bridged between two Cr ions; each Cr atom is coordinated to two N atoms of the ligands in a linear fashion. The Cr atom is in a low oxidation state, Cr(I), and in low coordination number condition, which stabilizes a metal-metal multiple bond, in this case, a quintuple bond. Indeed, it gives an ultrashort Cr-Cr bond distance of 1.7492(1) ? in the complex. The bond characterization of such a quintuple bond is undertaken both experimentally by high-resolution single-crystal X-ray diffraction and theoretically by density functional calculation (DFT). Electron densities are depicted via deformation density and Laplacian distributions. Bond characterizations of the complex are presented in terms of topological properties, Fermi hole function, source function (SF), and natural bonding orbital (NBO) analysis. The electron density at the Cr-Cr bond critical point (BCP) is 1.70 e/?(3), quite a high value for metal-metal bonding and mainly contributed from the metal ion itself. The quintuple bond is confirmed with one σ, two π, and two δ interactions by NBO analysis and Fermi hole function. The molecular orbitals (MOs) illustrate that five bonding orbitals are predominantly contributed from the 3d orbitals of the Cr(I) ion. The effective bond order from NBO analysis is 4.60. The detail comparison between experiment and theory will be given. Additionally, three closely related complexes are calculated for systematic comparison. 相似文献
969.
We have studied the triplet energy transfer (TET) for photosynthetic light-harvesting complexes, the bacterial light-harvesting complex II (LH2) of Rhodospirillum molischianum and Rhodopseudomonas acidophila, and the peridinin-chlorophyll a protein (PCP) from Amphidinium carterae. The electronic coupling factor was calculated with the recently developed fragment spin difference scheme (You and Hsu, J. Chem. Phys. 2010, 133, 074105), which is a general computational scheme that yields the overall coupling under the Hamiltonian employed. The TET rates were estimated based on the couplings obtained. For all light-harvesting complexes studied, there exist nanosecond triplet energy transfer from the chlorophylls to the carotenoids. This result supports a direct triplet quenching mechanism for the photoprotection function of carotenoids. The TET rates are similar for a broad range of carotenoid triplet state energy, which implies a general and robust TET quenching role for carotenoids in photosynthesis. This result is also consistent with the weak dependence of TET kinetics on the type or the number of π conjugation lengths in the carotenoids and their analogues reported in the literature. We have also explored the possibility of forming triplet excitons in these complexes. In B850 of LH2 or the peridinin cluster in PCP, it is unlikely to have triplet exciton since the energy differences of any two neighboring molecules are likely to be much larger than their TET couplings. Our results provide theoretical limits to the possible photophysics in the light-harvesting complexes. 相似文献
970.
Chang YC Wang CL Pan TY Hong SH Lan CM Kuo HH Lo CF Hsu HY Lin CY Diau EW 《Chemical communications (Cambridge, England)》2011,47(31):8910-8912
We designed highly efficient porphyrin sensitizers with two phenyl groups at meso-positions of the macrocycle bearing two ortho-substituted long alkoxyl chains for dye-sensitized solar cells; the ortho-substituted devices exhibit significantly enhanced photovoltaic performances with the best porphyrin, LD14, showing J(SC) = 19.167 mA cm(-2), V(OC) = 0.736 V, FF = 0.711, and overall power conversion efficiency η = 10.17%. 相似文献