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991.
Influence of a two-dimensional electron gas on current—voltage characteristics of Al0.3{Ga}0.7 N/GaN high electron mobility transistors 下载免费PDF全文
The J-V characteristics of AltGa1 tN/GaN high electron mobility transistors(HEMTs) are investigated and simulated using the self-consistent solution of the Schro dinger and Poisson equations for a two-dimensional electron gas(2DEG) in a triangular potential well with the Al mole fraction t = 0.3 as an example.Using a simple analytical model,the electronic drift velocity in a 2DEG channel is obtained.It is found that the current density through the 2DEG channel is on the order of 10^13 A/m^2 within a very narrow region(about 5 nm).For a current density of 7 × 10^13 A/m62 passing through the 2DEG channel with a 2DEG density of above 1.2 × 10^17 m^-2 under a drain voltage Vds = 1.5 V at room temperature,the barrier thickness Lb should be more than 10 nm and the gate bias must be higher than 2 V. 相似文献
992.
ZnO nanorod arrays with tunable size and field emission properties on an ITO substrate achieved by an electrodeposition method 下载免费PDF全文
In the present work,vertically aligned ZnO nanorod arrays with tunable size are successfully synthesized on nonseeded ITO glass substrates by a simple electrodeposition method.The effect of growth conditions on the phase,morphology,and orientation of the products are studied in detail by X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).It is observed that the as-prepared nanostructures exhibit a preferred orientation along c axis,and the size and density of the ZnO nanorod can be controlled by changing the concentration of ZnCl2.Field emission properties of the as-synthesized samples with different diameters are also studied,and the results show that the nanorod arrays with a smaller diameter and appropriate rod density exhibit better emission properties.The ZnO nanorod arrays show a potential application in field emitters. 相似文献
993.
Influence of different oxidants on band alignment of HfO2 films deposited by atomic layer deposition 下载免费PDF全文
Based on X-ray photoelectron spectroscopy (XPS), influences of different oxidants on band alignment of HfO2 films deposited by atomic layer deposition (ALD) are investigated in this paper. The measured valence band offset (VBO) value for H2O-based HfO2 increases from 3.17 eV to 3.32 eV after annealing, whereas the VBO value for O3-based HfO2 decreases from 3.57 eV to 3.46 eV. The research results indicate that the silicate layer changes in different ways for H2O-based and O3-based HfO2 films after annealing process, which plays a key role in generating the internal electric field formed by the dipoles. The variations of the dipoles at the interface between the HfO2 and SiO2 after annealing may lead the VBO values of H2O-based and O3-based HfO2 to vary in different ways, which is in agreement with the varition of flat band (VFB) voltage. 相似文献
994.
A new type of bismuth silicate glass (Bi2O3-SiO2-ZnO-Al2O3-La2O3) doped with Tm2O3 is prepared by melt-quenching method. The thermal stability of the glass is examined by differential scanning calorimetry. No crystallization peak is found. Using the absorption and emission spectra, the absorption and emission cross-sections are calculated. Their maximum data are 2.9×10-21cm2 at 1663 nm and 4.7×10-21cm2 at 1826 nm, respectively. Using the Judd-Ofelt theory, the radiation transition probabilities and radiative lifetimes are obtained. The extended overlap integral method is applied to analyze energy transfer process among the Tm3+ ions. The transfer constants of cross-relaxation and energy migration among the Tm3+ ions at the 3H4 level are 7.60×10-40 and 14.98×10-40 cm6 /s, respectively. The critical transfer radius for cross-relaxation is 0.99 nm. The cross relaxation process is easy to realize and is favorable for obtaining ~2-μm laser. 相似文献
995.
B. Jiang Zh. Gong M. Chen J. Li W. Liu Y. Pan 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(6):643-647
Transparent Yb3x Y3(1 ? x )Al5O12 (x = 3, 5, 10 and 15%) ceramics were fabricated by solid-state reaction and vacuum sintering method with a mixture of commercial Al2O3, Y2O3 and Yb2O3 powders. Ethanol and 0.5 wt % tetraethoxysilane were doped. Transparent fully dense samples with grain sizes of several micrometers were obtained by sintered at 1750 K. The absorption spectra, emission spectra and fluorescence life time of these transparent Yb3x Y3(1 ? x )Al5O12 ceramics at room temperature have been measured and calculated. The air annealed effects of Yb3x Y3(1 ? x )Al5O12 ceramics have been compared with un-annealed Yb:YAG transparent ceramics which shows the difference of the Yb3+ ions between annealed and unannealed Yb:YAG ceramics is less than 1%. 相似文献
996.
997.
In 2002, Bollobás and Scott posed the following problem: for an integer and a graph G of m edges, what is the smallest f (k, m ) such that V (G ) can be partitioned into V 1,…,V k in which for all , where denotes the number of edges with both ends in ? In this paper, we solve this problem asymptotically by showing that . We also show that V (G ) can be partitioned into such that for , where Δ denotes the maximum degree of G . This confirms a conjecture of Bollobás and Scott. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 50, 59–70, 2017 相似文献
998.
利用同位旋相关的量子分子动力学(IQMD)模型,分析了中能重离子碰撞过程中相对论平均场和SkyrmeHartrere-Fork等核结构模型给出的核密度分布对原子核阻止的影响。研究表明,从费米能到的较大能量范围内,无论小质量体系还是大质量体系,原子核阻止对同位旋相关的核子-核子碰撞截面都非常灵敏,而不同模型给出的核密度分布对原子核阻止影响不大,说明原子核阻止作为提取同位旋相关核子-核子碰撞截面的灵敏探针是与原子核结构模型无关的。 Influence of densitydistributionwhichisgivenbyRMFandSkyrme-Hartrere-Fork etalnuclearstructuremodelonnuclearstoppinginheavy-ioncollisionsatintermediateenergiesarestudiedbyusingisospin-dependentquantummoleculardynamics(IQMD)model.ResearchshowsthatrangeformtheFermienergytothelargerenergyof 100 Mev/u, for bothsmallandlargemasssystem,nuclearstoppingisfoundtobestronglydependentonthenucleon-nucleoncrosssections,andweaklyondifferentdensitydistribution.ThisshowsthatnuclearstoppingcanbeusedasaprobetoextracttheinformationontheisospindependenceN-Ncrosssectionsandhasnorelationshipwithnuclearstructuremodels. 相似文献
999.
1000.