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811.
812.
The nonlinear propagation of ion-acoustic (IA) shock waves (SHWs) in a nonextensive multi-ion plasma system (consisting of inertial positive light ions as well as negative heavy ions, noninertial nonextensive electrons and positrons) has been studied. The reductive perturbation technique has been employed to derive the Burgers equation. The basic properties (polarity, amplitude, width, etc.) of the IA SHWs are found to be significantly modified by the effects of nonextensivity of electrons and positrons, ion kinematic viscosity, temperature ratio of electrons and positrons, etc. It has been observed that SHWs with positive and negative potential are formed depending on the plasma parameters. The findings of our results obtained from this theoretical investigation may be useful in understanding the characteristics of IA SHWs both in laboratory and space plasmas. 相似文献
813.
The 1(E), –Im–1, and Re–1 spectra of the fluorite crystal are calculated on the basis of the experimental (10–35 eV) and theoretical spectra 2(E) (10–27 and 8–20 eV). They were employed to decompose the 2(E) and –Im–1 spectra into elementary components. The most intense transverse and longitudinal components of transitions and their parameters have been determined. The correlation between two types of components of transitions and their distinguishing features have been established. 相似文献
814.
815.
Hj. Matzke 《辐射效应与固体损伤》2013,168(1):93-105
Abstract The present study contributes some new aspects to the general understanding of the ion implantation behaviour of 3 common semiconductor materials, and of diffusion processes in these materials. Single crystals of Si, Ge, and GaAs were bombarded with Kr- or Xe-ions at energies of 40 or 500 keV and doses between 1011 and 2 × 1016 ions/cm2. Gas release measurements and Rutherford scattering of 1 MeV He+-ions combined with channeling were used to study bombardment damage (amorphization) and inert gas diffusion. At low bombardment doses (1011 ions/cm2) and energy (40 keV), no damage was observed and the gas release was compatible with volume diffusion resembling Group I and VIII behaviour. Hence, the pre-exponential terms, D 0, were low (range 10-5±1 cm2 sec?1) and the activation enthalpies, Δ H, were much lower than those of self-diffusion or of diffusion of Group III and V elements. The Δ H's for gas diffusion followed the relation Δ H = (1.05±0.1) × 10?3 Tm eV with the melting point, Tm , in °K. The mechanism of gas mobility might be the Turnbull dissociative mechanism. Rutherford scattering and channeling data indicated that part of the gas occupied lattice sites. At higher doses, the bombarded layers turned amorphous. Channeling experiments showed a coincidence in temperatures for a gas release process different from the above one of volume diffusion, and recrystallization of the disordered layer to the single crystalline state. Both processes occurred in the temperature range 0.60 to 0.65 Tm . The gas release indicated a (partial) single jump character with implied Δ H's following the relation Δ H = (2.1±0.1) × 10?3 Tm eV. Contrary to previous results on oxides, this new gas release occurred at temperatures near to those or even above those of volume diffusion of the gas. Due to the easy formation of an amorphous layer it was difficult to observe the retarded release (trapping of gas) that has been found in many materials at high gas and damage concentrations. However, in a separate series of experiments with 500 keV Kr-ions, a release retarded with respect to volume diffusion of the gas was observed in Si and Ge. 相似文献
816.
817.
We synthesize small and uniform NiO nanocrystals, which can be potential for hole‐transporting of organic solar cells and transparent conducting material, based on a protecting ligand of lithium stearate by a hot‐injection method. And the reaction mechanism is alcoholysis of metal carboxylate salts with the protection ligand of lithium stearate binding to the surfaces of NiO nanocrystals to prevent them reduction into Ni. We find that the hot‐injection method is an effective way to prepare narrow size distribution and small size of NiO nanocrystals. The relatively superior optical transparency and flat surface features of the NiO nanocrystal thin films are also obtained. 相似文献
818.
基于有限差分方法,研究周期梯度磁场调制下二维电子气的电子性质.结果表明:由于周期梯度磁场的存在,体系展现出丰富的电子能带结构.其子带的宽度随|ky|增大而不断变窄,|ky|越大势阱越深;由于在ky > 0和ky < 0两个区域的有效势能不一样,其能带结构在两个区域不一致且在ky > 0的区域中形成更多束缚态.通过改变磁条周期、磁条到2DEG的距离及磁化强度研究其对电子能带结构的影响. 相似文献
819.
We represent the two K-shell electrons of neutral atoms by Hylleraas-type wave function which fulfils the exact behavior at the electron–electron and electron-nucleus coalescence points and, derive a simple method to construct expressions for single-particle position- and momentum-space charge densities, and respectively. We make use of the results for and to critically examine the effect of correlation on bare (uncorrelated) values of Shannon information entropies (S) and of Fisher information (F) for the K-shell electrons of atoms from helium to neon. Due to inter-electronic repulsion the values of the uncorrelated Shannon position-space entropies are augmented while those of the momentum-space entropies are reduced. The corresponding Fisher information are found to exhibit opposite behavior in respect of this. Attempts are made to provide some plausible explanation for the observed response of S and F to electronic correlation. 相似文献
820.
运用π电子紧束缚模型,具体研究了锯齿型石墨烯纳米带(ZGNRs)的边界结构对能带,特别是费米面附近的导带和价带电子的影响.计算了七种不同边界结构的ZGNRs的能带色散关系及费米面附近价带电子在原胞中各原子上的分布情况.计算结果表明:两边界都无悬挂原子的NN-ZGNRs,只有一边界有悬挂原子的DN-ZGNRs,两边界都有五边形环的SPP-ZGNRs和ASPP-ZGNRs为金属性.两边界都有悬挂原子的DD-ZGNRs,一边界为五边形环另一边界无悬挂原子的PN-ZGNRs和一边界为五边形环另一边界有悬挂原子的P
关键词:
锯齿型石墨烯纳米带
紧束缚模型
电子密度分布
缺陷结构 相似文献