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961.
The formation of macrostep during high-temperature phase of barium meta-borate (α-BaB 2 O 4) single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy (AFM).The insitu observation results demonstrate that the critical linear size of growing facet exceeding the size that the macrostep generates is significantly anisotropic.The critical linear sizes are around 280 μm and 620 μm for {1010} and {1010} planes,respectively.AFM study illustrates that macrostep train with a height of 150 nm~200 nm is one typical morphological feature of the as-grown crystal surface.The riser of each macrostep consists of several straight and parallel sub-steps,indicating the occurrence of step bunching.Additionally,triangular sub-steps with heights of several nanometers on the treads of the macrosteps are found to be another typical feature of surface morphology,which implies a microscopically competitive bunching of sub-steps between various crystallographic orientations. 相似文献
962.
E.E. Assem 《Physica B: Condensed Matter》2011,406(3):421-425
The effect of halide ions on density, electrical, magnetic and crystallization kinetics for (20X-50P2O5-30V2O5) mole% has been investigated, where X=CaO, CaF2, CaCl2 and CaBr2. Halide ions reduce the glass transition temperature, crystallization temperature and activation energy of crystallization. Density, electrical conductivity and magnetic susceptibility increase while molar volume, glass thermal stability and interatomic distance between transition metal ions decrease as the halide ions replace the oxygen ions in these glasses. 相似文献
963.
P.A. Mariño-CastellanosA.C. Moreno-Borges G. Orozco-MelgarJ.A. García E. Govea-Alcaide 《Physica B: Condensed Matter》2011,406(17):3130-3136
We present a theoretical and experimental study of the structural and magnetic properties of M-type Ti4+-doped barium hexaferrite BaFe(12−(4/3)x)TixO19 with x=0, 0.1, 0.2, 0.3, 0.5, 0.7 and 1.3. The XRD patterns and magnetic measurements show appreciable variations in the values of the saturation magnetization and the magnetic anisotropy field, Han, with increasing Ti4+ content. We did not observe significant changes in the Lotgering factor along the (0 0 l) direction and in the texture coefficient, Cex, which was estimated from the torque curves. The magnetic properties of these materials are explained by the combined effect of the coherent rotation of the magnetic domains and the replacements of Fe3+ by Ti4+ ions in the octahedral and tetrahedral sites. The influence of the Ti4+ content on the samples was studied theoretically by using a statistical phenomenological model. The main purpose of the model is to make preliminary predictions of the distribution of any dopant cation in the Fe3+ sites. As a result, we are able to analyze both structural and magnetic features of M-type barium hexaferrite. 相似文献
964.
The spin-polarized electronic band structures, density of states (DOS), and magnetic properties of Co-Mn-based Heusler alloys CoMnSb and Co2MnSb have been studied by first-principles method. The calculations were performed by using the full-potential linearized augmented plane wave (FP-LAPW) within the spin-polarized density functional theory and generalized gradient approximation (GGA). Calculated electronic band structures and the density of states are discussed in terms of the contribution of Co 3d74s2, Mn 3d54s2, and Sb 5s25p3 partial density of states and the spin magnetic moments were also calculated. The results reveal that both CoMnSb and Co2MnSb have stable ferromagnetic ground state. They are ideal half-metallic (HM) ferromagnet at their equilibrium lattice constants. The calculated total spin magnetic moments are 3μB for CoMnSb and 6μB for Co2MnSb per unit cell, which agree with the Slater-Pauling rule quite well. 相似文献
965.
C.L. Zhang J. ChenT.Z. Wang G.X. XieC. Zhu D.H. Wang 《Physica B: Condensed Matter》2011,406(14):2840-2842
The first-order phase transitions in NdFe12B6 and PrFe12B6 alloys give rise to giant values of magnetic entropy changes in relatively low field. However, the metastable nature of these alloys associates with a special procedure of preparation and considerable amount of impurities inevitably. By alloying NdFe12B6 with the iso-structural compound of NdCo12B6 appropriately, a Nd(Co1−xFex)12B6 system which possesses the stable SrNi12B6-type structure can be obtained directly via the standard casting-and-annealing method. Remarkably improved thermal and magnetic reversibility are observed in the present system. The second-order phase transitions in NdCo12B6 alloy give rise to the relative cooling power, which is comparable with that of NdFe12B6 alloy around the ordering temperature. 相似文献
966.
Alfaisal A. Hasan 《Physica B: Condensed Matter》2011,406(2):234-240
The electrogravitational instability of on oscillating streaming fluid cylinder under the action of the selfgravitating, capillary and electrodynamic forces has been discussed. The model is governed by the Mathieu second order integro-differential equation. Some limiting cases are recovering from the present general one. The capillary force is destabilizing in a small axisymmetric domain 0<x<1 and stabilizing otherwise. In the absence of electric fields, we found that the model is unstable in a small domain while it is selfgravitating stable in all other domains. The presence of the electric field led to the presence of a great number of stable waves. The electric field has a strong stabilizing influence on the selfgravitating instability of the model. The capillary force has a strong destabilizing influence on the selfgravitating instability of the model.Generally, the uniform stream supports the unstable waves, while the oscillating streaming has stability tendency. 相似文献
967.
We report ab-initio calculations of the structural, electronic, magnetic and optical properties of the alloy Cd1-xMnxTe as a function of the Mn concentration ‘x’. Ab-initio calculations are based on the density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constants of the Cd1-xMnxTe alloys exhibit Vegard's law downward bowing parameter. For the minority spin channel the Fermi level shifts toward higher energy with the value of ‘x’ in Cd1-xMnxTe. The spin-exchange splitting energy Δx(d) increases with increasing ‘x’ in Cd1-xMnxTe and the values of p-d exchange splitting energy Δx(pd) of Cd1-xMnxTe show that the effective potential for the minority spin is more attractive than that for the majority spin. The values of exchange constants N0α and N0β obtained for Cd1-xMnxTe are in agreement with the reported data. The magnetic moment per Mn atom reduces from its free space charge value of 5μB to around 4μB due to p-d hybridization and this results into an appearance of small local magnetic moments on the non-magnetic Cd and Te sites. The absorption threshold shifts toward higher energy and the static refractive index decreases with the increasing value of ‘x’ in Cd1-xMnxTe. 相似文献
968.
P. IranmaneshN. Tajabor M. Rezaee Roknabadi D. FruchartF. Pourarian 《Physica B: Condensed Matter》2011,406(18):3359-3362
Magnetoelastic properties of Nd6Fe13Cu intermetallic compound are reported. To study the magnetoelastic behaviour of this compound, the thermal expansion as well as the longitudinal (λl) and transverse (λt) magnetostriction were measured by using the strain gauge method in the selected temperature range of 80-500 K under applied magnetic fields up to 1.5 T. An anomaly and invar-type effects are observed in the linear thermal expansion and α(T) curves at the Néel temperature. The linear spontaneous magnetostriction decreases sharply by approaching the Néel temperature and also shows the short-range magnetic ordering effects when antiferromagnetic-paramagnetic transition occurs. In the low field region, the absolute values of the anisotropic magnetostriction are small and then start to increase with applied magnetic field. Each isofield curve of the anisotropic magnetostriction passes through a minimum and then approaches to zero with increasing temperature. This magnetostriction compensation arises from the difference in the magnetoelastic coupling constants of the sublattices in this compound. 相似文献
969.
Amitesh Paul Thomas KristAnke Teichert Roland Steitz 《Physica B: Condensed Matter》2011,406(8):1598-1606
We report on the enhanced capabilities of neutron reflectometer V6 at the research reactor BER II at Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) in investigating magnetic thin films and multilayers. It is now fully equipped for simultaneous measurements of specular and off-specular scattering with polarization and polarization analysis. The magnetization configuration of a [CoO/Co/Au]×16 polycrystalline multilayer at room temperature is reported in demonstrating the efficiency of the instrument. The data is simulated within the supermatrix formalism under the distorted wave Born approximation for a quantitative analysis. 相似文献
970.
R. Khordad 《Physica B: Condensed Matter》2011,406(3):620-623
The threshold frequency of absorption in a quantum pseudodot under the influence of temperature and applied magnetic field is calculated. The threshold frequency of absorption is computed as a function of temperature and applied magnetic field. The linear and nonlinear dependence of the absorption threshold frequency on magnetic field and temperature has been showed. According to the results obtained from the present work, we find that the linear and nonlinear dependence of the absorption threshold frequency depends on used range of the temperatures and magnetic fields. 相似文献