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901.
A cohesive zone model of axisymmetric adhesive contact between a rigid sphere and a power-law graded elastic half-space is established by extending the double-Hertz model of Greenwood and Johnson (1998). Closed-form solutions are obtained analytically for the surface stress, deformation fields and equilibrium relations among applied load, indentation depth, inner and outer radii of the cohesive zone, which include the corresponding solutions for homogeneous isotropic materials and the Gibson solid as special cases. These solutions provide a continuous transition between JKR and DMT type contact models through a generalized Tabor parameter μ. Our analysis reveals that the magnitude of the pull-off force ranges from (3+k)πRΔγ/2 to 2πRΔγ, where k, R and Δγ denote the gradient exponent of the elastic modulus for the half-space, the radius of the sphere and the work of adhesion, respectively. Interestingly, the pull-off force for the Gibson solid is found to be identically equal to 2πRΔγ, independent of the corresponding Tabor parameter. The obtained analytical solutions are validated with finite element simulations. 相似文献
902.
The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution for 15 s and thermal heating SiC in hydrogen atmosphere at 1100 C for 10 min, while the H-terminated surface on C-face 6H-SiC could be obtained only by the latter method. Ti is deposited on Si-face and C-face SiC substrates with H-terminated surfaces and ohmic contact is obtained without high-temperature annealing. 相似文献
903.
Research on the electrical characteristics of an organic thin-film field-effect transistor based on alternating-current resistance 下载免费PDF全文
In this article, an organic thin-film field-effect transistor (OTFFET) with top-gate and bottom-contact geometry based on pentacene as the active layer is fabricated. The experimental data of the I-V are obtained from the OTFFET device. The alternating-current (AC) resistance value of the OTFFET device is calculated using the derivation method from the experimental data, and the AC resistance trend curves of the OTFFET device are obtained with the region fitting method. We analyse the characteristics of the OTFFET device with an AC resistance trend curve. To discover whether it has a high resistance, it is proposed to judge the region of the source/drain voltage (VDS) less than the transition voltage, thereby determining whether the contact between the metal electrode and the organic semiconductor layer of the OTFFET device is Ohmic or non-Ohmic. The theoretical analysis shows that the field-effect mobility and the AC resistance are in reverse proportion. Therefore, we point out that reducing AC resistance is necessary if field-effect mobility is to be improved. 相似文献
904.
将2种等温淬火球墨铸铁(Austempered Ductile Iron, ADI)和合金钢车轮材料分别与合金钢钢轨材料匹配,研究各摩擦副的滚动接触磨损性能.结果表明:与合金钢车轮材料相比,2种ADI材料的磨损性能均有大幅度的改善.硬度低、石墨球直径小且密度大的ADI材料自润滑效果好,相对应的摩擦副抗磨损性能最好;硬度高、石墨球直径大且密度小的ADI材料自润滑效果较差,相对应的摩擦副抗磨损性能居中;合金钢车轮材料不具备自润滑能力,相对应的摩擦副抗磨损性能最差. 相似文献
905.
通过在有机硅烷中掺杂微纳米级尺度的SiO2颗粒,利用硅烷的水解和聚合成功地制备了1种具有优异耐磨性能和稳定性的超疏水材料.通过该方法所制备的超疏水材料不仅具有良好的耐磨性,而且其超疏水性能可在一定条件下通过表面的磨损得到增强或恢复.该超疏水材料在较苛刻的环境下仍能保持良好的化学稳定性.扫描电镜分析表明贯穿于整个材料且构成材料厚度的微纳米聚合物复合层是赋予该超疏水材料耐磨损性能的主要原因. 相似文献
906.
907.
Typical VOF algorithms rely on an implicit slip that scales with mesh refinement, to allow contact lines to move along no-slip boundaries. As a result, solutions of contact line phenomena vary continuously with mesh spacing; this paper presents examples of that variation. A mesh-dependent dynamic contact angle model is then presented, that is based on fundamental hydrodynamics and serves as a more appropriate boundary condition at a moving contact line. This new boundary condition eliminates the stress singularity at the contact line; the resulting problem is thus well-posed and yields solutions that converge with mesh refinement. Numerical results are presented of a solid plate withdrawing from a fluid pool, and of spontaneous droplet spread at small capillary and Reynolds numbers. 相似文献
908.
Rosa Di Mundo Vincenzo De Benedictis Riccardo d’Agostino 《Applied Surface Science》2009,255(10):5461-5465
In this work the roughening of polystyrene by means of radiofrequency plasmas fed with CF4 has been studied. The effect of the Ar addition to the feed, the input power and the treatment duration has been investigated in terms of etching and fluorination degree. Wettability and reflectance performances of selected textured surfaces, coated with a fluorocarbon film from a C4F8 fed plasma, have been characterized. All the considered surfaces, even those poorly structured, once coated, show slippery superhydrophobicity, while antireflective transparency appears to be limited to precise texturing characteristics. 相似文献
909.
A superhydrophobic surface was obtained by embedding hydrophobically modified fumed silica (HMFS) particles in polyvinylidene fluoride (PVDF) matrix. The water contact angle (WCA) on the PVDF-HMFS hybrid composite coating is influenced by the content and nature of silica particles in the coating. As the silica concentration in PVDF matrix was increased from 33.3% to 71.4%, WCA increased from 117° to 168° and the sliding angle decreased from 90° to <1°. Surface topography of the coating was examined using scanning electron microscopy. An irregular rough surface structure composed of microcavities and nanofilaments was found to be responsible for the superhydrophobicity. The method is simple and cost-effective and can be used for preparing self-cleaning superhydrophobic coating on large areas of different substrates. 相似文献
910.