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排序方式: 共有78条查询结果,搜索用时 15 毫秒
41.
《Acta Materialia》2004,52(9):2549-2560
The kinetics of the recently discovered abnormal austenite (γ)–ferrite (α) transformation of substitutional Fe–Co and Fe–Mn alloys were measured by dilatometry and compared with the, also measured, corresponding normal transformation behaviour. A phase transformation model, involving site saturation, interface-controlled continuous growth and incorporating an impingement correction, has been employed to extract the migration velocity of the γ/α interface. It was found that the normal transformation process could be well described assuming a constant nucleus density and interface migration velocity. The thus assessed misfit-accommodation, deformation Gibbs energy is of the same order of magnitude as the chemical Gibbs energy change driving the transformation. A large austenite grain size was shown to be the precondition for the occurrence of abnormal kinetics. The abnormal transformation process involves the occurrence of additional peaks in the transformation rate for the first stage of the transformation. An autocatalytic type of nucleation was successfully incorporated in the above model to describe the occurrence of the repeated nucleation during the abnormal transformation. 相似文献
42.
高度分布函数与自相关函数对表面粗糙度参数的影响 总被引:1,自引:1,他引:0
目的研究具有不同高度分布和自相关函数的表面形貌的粗糙度参数变化。方法利用数字滤波法构造具有特定参数(如倾斜度、峰值、最快下降自相关长度和纹理高宽比、高度方差)的粗糙度表面,然后比较和分析不同类型形貌的参数。结果算术平均峰曲率不随高度分布函数和自相关函数变化,均方根斜率、界面开发面积比和峰密度随各种高度分布函数和自相关函数变化的影响较大。结论算术平均峰曲率不能表征高度分布和自相关函数。比较相同高度分布的表面形貌时,应对纹理高宽比、最快下降自相关长度、均方根斜率、界面开发面积比和峰密度进行比较。当比较不同高度分布的形貌时,应该对高度类参数倾斜度、峰值、高度均方根、最大高度、最大谷值和最大峰高进行比较。 相似文献
43.
《Solid-state electronics》1987,30(3):273-279
All the terms contributing to the dark current for an n-amorphous/p-crystalline silicon heterojunction have been evaluated. The abrupt heterojunction model with the presence of interface states has been adopted and flat quasi-Fermi levels have been assumed across both depletion regions. The gap density of states in amorphous silicon has been approximated by a V-distribution. The dominant current mechanisms at forward and reverse biases have been determined and the zero-bias spectral response has been calculated. 相似文献
44.
《Materials Letters》1987,5(4):147-152
Photoemission measurements indicate that limited interdiffusion and reaction occurs between Cu and Hf at the Cu/Hf interface. Additional amounts of Hf can be introduced into the Cu overlayer by heat treatment. Examination of our data suggests that at least 3–5 Cu layers are involved in forming the extended Cu/Hf interface. This result is in excellent agreement with EXAFS data recently reported for Cu/Hf multilayers. 相似文献
45.
《International Journal of Hydrogen Energy》2020,45(55):30659-30665
Development of efficient and highly active non-noble metal electrocatalysts to replace Pt-based catalysts for achieving pH-dependent electrochemical hydrogen generation on a large scale is extremely significant. In this study, a B-doped molybdenum carbide nanocrystal confined in a porous N-doped carbon nanostructure (B–MoC) was synthesized and evaluated as a pH-independent electrocatalyst for the hydrogen evolution reaction (HER). B-doping could modify the electronic structure of MoC by introducing electron deficiency, which resulted in excess electron transfer to MoC nanoparticles, thereby generating many proton adsorption sites and improving the electrocatalytic performance. B-doping could also increase the electrochemical surface area of the catalyst and lower its resistance. Moreover, B–MoC could participate in charge transfer processes and prevent the agglomeration of MoC nanoparticles. B–MoC showed a low overpotential of 285 mV at a current density of 10 mA cm−2, as well as excellent stability for 1000 cycles in an acidic medium. Such remarkable improvements in the activity and stability of B–MoC toward HER were also observed in alkaline and neutral media. 相似文献
46.
《材料科学技术学报》2019,35(7):1485-1490
Effect of segregation behaviors of P at different cooling rates on the precipitation of γ″ and γ′ phases and the corresponding strength are investigated. The precipitation of γ″ and γ′ phases during cooling is sensitive to P concentration. With increasing the concentration of P, the amount of γ″ and γ′ particles increases after air cooling. With decreasing the cooling rate, the accelerating effect of P on the precipitation of γ″ and γ′ phases decreased first and then increased, which demonstrates the concentration of P dissolved in the grain interior decreases first and then increases. The different effects of P on γ″ and γ′ phases with different cooling rates were analyzed by the kinetic characteristic of nonequilibrium grain-boundary segregation. The characteristic of nonequilibrium grain-boundary segregation of P in superalloy is further confirmed, and the phenomenon caused by critical cooling rate is captured. 相似文献
47.
《Organic Electronics》2014,15(7):1678-1686
A high efficient UV–violet emission type material bis[4-(9,9′-spirobifluorene-2-yl)phenyl] sulfone (SF-DPSO) has been synthesized by incorporating electron deficient sulfone and morphologically stable spirobifluorene into one molecule. The steric and bulky compound SF-DPSO exhibits an excellent solid state photoluminescence quantum yield (ΦPL = 92%), high glass transition temperature (Tg = 211 °C) and high triplet energy (ET = 2.85 eV). In addition, the uniform amorphous thin film could be formed by spin-coating from its solution. These promising physical properties of the material made it suitable for using as UV–violet emitter in non-doped device and appropriate host in phosphorescent OLEDs. With SF-DPSO as an emitter, the non-doped solution processed device achieved an efficient UV–violet emission with the EL peak around 400 nm. By using SF-DPSO as a host, solution processed blue and green phosphorescent organic light emitting diodes showed a high luminous efficiency of 13.7 and 30.2 cd A−1, respectively. 相似文献
48.
Effective mobility in amorphous organic transistors: Influence of the width of the density of states
《Organic Electronics》2014,15(1):35-39
The temperature dependence of poly(3-hexylthiophene-2,5-diyl) (P3HT)/polystyrene (PS) blend organic transistor current/voltage (I–V) characteristics has been experimentally and theoretically studied. The planar transistors, realized by drop casting the P3HT/PS ink, exhibit high mobilities (over 5 × 10−3 cm2 V−1 s−1) and good overall characteristics. A transistor model accounting for transport mechanisms in disordered organic materials was used to fit the measured characteristics. Using a single set of parameters, the measured effective mobility versus gate bias, either increasing or decreasing with the gate bias depending on temperature, is well reproduced over a wide temperature range (130–343 K). A Gaussian density of states width of 0.045 eV was determined for this P3HT/PS blend. The transistor I–V characteristics are very well described considering disordered material properties within a self-consistent transistor model. 相似文献
49.
《Organic Electronics》2014,15(1):29-34
Columnar MoO3 in situ growth prepared from direct converting soluble Mo-containing precursor during active layer thermal annealing was utilized as anode buffer layer to fabricate organic bulk heterojunction photovoltaics. The columnar morphology could improve the interface contact between active layer and buffer layer. The structure and phase of in situ formed MoO3 were studied by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We demonstrated that the organic photovoltaic devices based on P3HT:PC61BM using in situ formed columnar MoO3 as anode buffer layer presented a high open-circuit voltage and fill factor leading to an efficiency of 3.92%, which is higher than the controlled PEDOT:PSS-based devices. 相似文献
50.