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991.
We study the negatively and positively charged trions in bulk materials in the effective mass approximation within the framework of a potential model. The binding energies of trions in various semiconductors are calculated by employing Faddeev equation in configuration space. Results of calculations of the binding energies for are consistent with previous computational studies and are in reasonable agreement with experimental measurements, while the is unbound for all considered cases. The mechanism of formation of the binding energy of trions is analyzed by comparing contributions of a mass-polarization term related to kinetic energy operators and a term related to the Coulomb repulsion of identical particles. 相似文献
992.
Oleg L. Berman Vladimir S. Boyko Roman Ya. Kezerashvili Anton A. Kolesnikov Yurii E. Lozovik 《Physics letters. A》2018,382(31):2075-2080
Two-dimensional graphene-based photonic crystal (GPC) formed by a periodic array of the homogeneous dielectric cylinders etched in the alternating graphene and dielectric layers and its inverse counterpart are considered. The transmittance of the photonic crystal is obtained. The waveguide due to the localization of the electromagnetic wave on the lattice defect that breaks the translational symmetry of the GPC of two different topologies is studied. The different topologies of GPC are characterized by different photonic band structures with different widths of photonic band gaps (PBG) and provide different frequencies for the localized electromagnetic wave due to the defect. The frequencies of the localized mode for both type of the GPC, located inside the lowest PBG, are in the range of THz or tens of THz depending on the topology of the GPC. It is shown that the photonic band gap always can be tuned by changing the chemical potential of graphene to provide formation of the localized photonic mode due to the defect. The technological advantages of the GPC, as well as the opportunity to tune the PBG and the frequency of the localized electromagnetic wave in the terahertz region of spectrum for the GPC are discussed. 相似文献
993.
Jesús San Fabián Salama Omar José M. García de la Vega 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(6):124
Spin-spin coupling constants are reported using six ab initio and fifteen DFT methods for dimers and larger clusters of ammonia. An analysis of components (Fermi contact, spin dipole, paramagnetic spin-orbit, and diamagnetic spin-orbit) of more relevant coupling constants 1JNH′, 1hJNH′ and 2hJNN has been carried out. Fermi contact is the dominant term in the total value for all constants. For dimers, a relationship between the addition of direct and intermolecular coupling constants gives the direct constants of monomer. From the comparison of all ab initio and DFT methods for dimers, SOPPA(CCSD) and S55VWN5 methods are, respectively, more reliable taking into account their accuracy and the computing time. Both methods are employed for the analysis of the transmission of coupling constants through the hydrogen bond for ammonia clusters. A linear relation between the intermolecular constants 1hJNH′ and the length of the hydrogen bond is found. 相似文献
994.
Pham Khac Hung Fumiya Noritake Luyen Thi San To Ba Van Le The Vinh 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(10):185
A systematic analysis on sodium-silicate melt with various silica contents was carried out. The simulation revealed two diffusion mechanisms occurred in the melt: the bond-breaking and hopping between sites. The local structure was analyzed through T-simplexes. It was revealed that T-clusters have a non-spherical shape and represent the diffusion channel, in which Na atoms are dominant, but no any O atoms are located. The SiO2-poor melt acquires a long channel. In contrast, the SiO2-rich melt consists of unconnected short channels. The simulation also revealed the immobile and mobile regions which differ in local structure and constituent composition. We propose a new CL-function to characterizing the spatial distribution of different atom component. The spatial distribution of mobile and immobile atoms is found quite different. In particular, the immobile atoms are concentrated in high-density regions possessing very large density of immobile atoms. The spatial distribution of mobile atoms in contrast is more homogeneous. 相似文献
995.
D. Michelle Motley Judith A. Walmsley Julio Zukerman-Schpector Edward R. T. Tiekink 《Journal of chemical crystallography》2009,39(5):364-367
Abstract The gold(III) atom in [Au(NH2CH2CH2NH2)Cl2]NO3 is chelated by the ethylenediamine (en) ligand and the approximately square planar geometry is completed by two chloride
atoms. Weak Au···O and Au···Cl contacts are noted above and below the square plane leading to a tetragonally distorted octahedron
for the gold(III) center. Extensive charge-assisted hydrogen bonding of the type N–H···O leads to the formation of a 2-D array
and layers are consolidated into a 3-D network via C–H···O and C–H···Cl contacts. The compound crystallizes in the orthorhombic
space group Pbca with a = 10.3380(11) ?, b = 8.2105(7) ?, c = 19.625(2) ?, and Z = 8.
Index Abstract Square planar complex cations form additional Au···O and Au···Cl interactions to form a tetragonally distorted octahedron
for gold. The ionic components are connected into a 2-D array via charge-assisted N–H···O hydrogen bonding interactions.
相似文献
996.
A Versatile Iron–Tannin‐Framework Ink Coating Strategy to Fabricate Biomass‐Derived Iron Carbide/Fe‐N‐Carbon Catalysts for Efficient Oxygen Reduction
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Dr. Jing Wei Yan Liang Yaoxin Hu Biao Kong Prof. George P. Simon Jin Zhang Prof. San Ping Jiang Prof. Huanting Wang 《Angewandte Chemie (International ed. in English)》2016,55(4):1355-1359
The conversion of biomass into valuable carbon composites as efficient non‐precious metal oxygen‐reduction electrocatalysts is attractive for the development of commercially viable polymer electrolyte membrane fuel‐cell technology. Herein, a versatile iron–tannin‐framework ink coating strategy is developed to fabricate cellulose‐derived Fe3C/Fe‐N‐C catalysts using commercial filter paper, tissue, or cotton as a carbon source, an iron–tannin framework as an iron source, and dicyandiamide as a nitrogen source. The oxygen reduction performance of the resultant Fe3C/Fe‐N‐C catalysts shows a high onset potential (i.e. 0.98 V vs the reversible hydrogen electrode (RHE)), and large kinetic current density normalized to both geometric electrode area and mass of catalysts (6.4 mA cm?2 and 32 mA mg?1 at 0.80 V vs RHE) in alkaline condition. This method can even be used to prepare efficient catalysts using waste carbon sources, such as used polyurethane foam. 相似文献
997.
Libia L. Julio Jesus Lezama Alexis Maldonado José R. Mora Gabriel Chuchani 《Journal of Physical Organic Chemistry》2014,27(5):450-455
The kinetics of the gas‐phase elimination of α‐methyl‐trans‐cinamaldehyde catalyzed by HCl in the temperature range of 399.0–438.7 °C, and the pressure range of 38–165 Torr is a homogeneous, molecular, pseudo first‐order process and undergoing a parallel reaction to produce via (A) α‐methylstyrene and CO gas and via (B) β‐methylstyrene and CO gas. The decomposition of substrate E‐2‐methyl‐2‐pentenal was performed in the temperature range of 370.0–410.0 °C and the pressure range of 44–150 Torr also undergoing a molecular, pseudo first‐order reaction gives E‐2‐pentene and CO gas. These reactions were carried out in a static system seasoned reactions vessels and in the presence of toluene free radical inhibitor. The rate coefficients are given by the following Arrhenius expressions:
- Products formation from α‐methyl‐trans‐cinamaldehyde
- α‐methylstyrene :
- β‐methylstyrene :
- Products formation from E‐2‐methyl‐2‐pentenal
- E‐2‐pentene :
998.
We study the nonlinear positive map of the density matrix of two-qubit Werner states, called the nonlinear channel. The map ρ → Φ(ρ) is realized by the rational function Φ. We discuss the influence of the map on the entanglement properties of the transformed density matrix. We investigate the violation of the Bell inequality (CHSH inequality) for the two-qubit state Φ(ρ). The nonlinear channels under discussion create the entangled state from a separable Werner state. We study the quantum spin tomograms of the states. 相似文献
999.
Diego Julio Cirilo-Lombardo 《Physics of Particles and Nuclei Letters》2014,11(4):502-505
New bounded coherent state construction, based in a Keldysh conjecture, is presented. The particular group structure arising from the model leads a new symmetry transformations for the coherent state system. The emergent new symmetry transformations are reminiscent of the Bogoliubov ones. This construction is applied to describe an excitonic system. We discuss how the symmetry of these transformations is intrinsically related with the stability and the behavior of the physical systems as in the excitonic case. 相似文献
1000.
Electrical and dielectric properties of Al/p-Si and Al/perylene/p-Si type diodes in a wide frequency range
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The perylene(C20H12) layer effect on the electrical and dielectric properties of Al/p-Si(MS) and Al/perylene/p-Si(MPS) diodes have been investigated and compared in the frequency range of 0.7 kHz–2 MHz. Experimental results show that C–V characteristics give an anomalous peak for two structures at low frequencies due to interface states(Nss) and series resistance(Rs). The increases in C and G/ω at low frequencies confirm that the charges at interface can easily follow an ac signal and yield excess capacitance and conductance. The frequency-dependent dielectric constant(ε) and dielectric loss(ε) are subtracted using C and G/ω data at 1.5 V. The ε and ε values are found to be strongly dependent on frequency and voltage, and their large values at low frequencies can be attributed to the excess polarization coming from charges at traps. Plots of ln(σac)–ln(ω) for two structures have two linear regions, with slopes of 0.369 and 1.166 for MS, and of 0.077 and 1.061 for MPS, respectively. From the C 2–V characteristics, the doping acceptor atom concentration(NA) and barrier height(ΦB) for Schottky barrier diodes(SBDs) of MS and MPS types are also obtained to be 1.484 × 1015 and 1.303 × 1015cm 3, and 1.10 and 1.13 eV, respectively. 相似文献