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71.
A technique based on the optical density (D) measurement of the etched track is useful for charged particles spectroscopy using SSNTD. It was shown that the stopping power of alpha particles in CR-39 is proportional to D. We measured the optical density and derived an expression to estimate the range of alpha particles in CR-39 detector as a function of the bulk etching rate and etching time. The relation between the etching time, track parameters (depth, radius) and D for different alpha particles energy and etching conditions were studied. A relation describing D as a function of track size is proposed. 相似文献
72.
Mahajan A. Arafa M. Fay P. Caneau C. Adesida I. 《Electron Devices, IEEE Transactions on》1998,45(12):2422-2429
The fabrication and characterization of high-speed enhancement-mode InAlAs/InGaAs/InP high electron mobility transistors (E-HEMTs) have been performed. The E-HEMT devices were made using a buried-Pt gate technology. Following a Pt/Ti/Pt/Au gate metal deposition, the devices were annealed in a nitrogen ambient, causing the bottom Pt layer to sink toward the channel. This penetration results in a positive shift in threshold voltage. The dc and RF performance of the devices has been investigated before and after the gate annealing process. In addition, the effect of the Pt penetration was investigated by fabricating two sets of devices, one with 25 nm of Pt as the bottom layer and the other with a 5.0 nm bottom Pt layer. E-HEMTs were fabricated with gate lengths ranging from 0.3 to 1.0 μm. A maximum extrinsic transconductance (gmext) of 701 mS/mm and a threshold voltage (VT) of 167 mV was measured for 0.3 μm gate length E-HEMTs. In addition, these same devices demonstrated excellent subthreshold characteristics as well as large off-state breakdown voltages of 12.5 V. A unity current-gain cutoff frequency (f t) of 116 GHz was measured as well as a maximum frequency of oscillation (fmax) of 229 GHz for 0.3 μm gate-length E-HEMTs 相似文献
73.
A. A. M. Arafa 《Journal of statistical physics》2011,145(5):1357-1367
In this paper, Adomian’s decomposition method (ADM) has been used for solving time-fractional host-parasitoid system. The
derivatives are understood in the Caputo sense. The reason of using fractional order differential equations (FOD) is that
FOD are naturally related to systems with memory which exists in most biological systems. Also they are closely related to
fractals which are abundant in biological systems. Numerical example justifies the proposed scheme. 相似文献
74.
In this paper, generalized Euler method (GEM) and homotopy analysis method (HAM) are performed to solve the problem of the population dynamics of the human immunodeficiency type 1 virus (HIV-1). We introduce fractional orders to the model of HIV-1 whose components are plasma densities of uninfected CD4+ T-cells, the infected such cells and the free virus. The effect of the drug treatment of HIV-1 will be discussed in this paper. 相似文献
75.
76.
Isam M. Arafa Mohammad F. Gharaibeh Mazin Shatnawi Javier Perez 《Journal of Non》2012,358(6-7):1044-1051
Three hybrid materials composed of planar s-triazine rings and polyhedral silica (SiO2), phenylsilsesquioxane (PhSiO1.5) and diphenylsiloxane (Ph2SiO) building blocks were investigated by differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) techniques. These measurements revealed that the geometrically dissimilar components were fully integrated into intact glassy hybrid structures. Their DSC thermograms showed that these hybrids are thermally stable below 350 °C with moderate glass transition temperatures (Tg) of 56–110 °C consistent with the increasing structural connectivity of the silicone component. The SAXS data was analyzed to obtain different structural information using Porod, Guinier and Kratky approximations. The general features of each of the SAXS profiles of these hybrids are very similar to those of polyphenylsilsesquioxane (PPhSQ). The SAXS profiles reveal that these hybrids can be described as nano-scale primary particles that are self-organized in macromolecular ensembles to form extended unfolded textures of varying scattering lengths (91–168 Å). The obtained hybrid particles adopt either 3-D bulk fractals with open structures or 2-D surface fractals with dense cores. The short interfacial thickness (< 3 Å) and the low thermal fluctuation parameters strongly suggest that these particles are held together by substantial cohesion forces. 相似文献
77.
78.
In this paper, the homotopy analysis method (HAM) has been employed to obtain analytical solution of a two reaction–diffusion systems of fractional order (fractional Schnakenberg systems) which has been modeling morphogen systems in developmental biology. Different from all other analytic methods, HAM provides us with a simple way to adjust and control the convergence region of solution series by choosing proper values for auxiliary parameter h. The fractional derivative is described in the Caputo sense. The reason of using fractional order differential equations (FOD) is that FOD are naturally related to systems with memory which exists in most biological systems. Also they are closely related to fractals which are abundant in biological systems. The results derived of the fractional system are of a more general nature. Respectively, solutions of FOD spread at a faster rate than the classical differential equations, and may exhibit asymmetry. However, the fundamental solutions of these equations still exhibit useful scaling properties that make them attractive for applications. 相似文献
79.
Alberto PlazaGiuseppe Bifulco Arafa I. HamedCosimo Pizza Sonia Piacente 《Tetrahedron letters》2003,44(47):8553-8558
Argeloside A and B, two novel 14,15-secopregnane glycosides characterized by the presence of two hemiketal functions involved in two five-membered rings, were isolated from Solenostemma argel fruits. Their structures have been established by ESIMS and NMR experiments. In particular the relative configuration of the molecules has been defined by combining the available NMR data with quantum chemical calculations of the geometries and 13C chemical shifts. 相似文献
80.
Ali Ali Arafa Fathi Sultan Ahmed Sultan Ibrahim Sayed Shafie 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1956,7(1):75-80
Zusammenfassung Ein Hitzdrahtmanometer bildet, mit einem Thermistor in eine Wheatstone-Anordnung geschaltet, ein Thermistor-Pirani-Messgerät hoher Empfindlichkeit, das in einem weiten Gebiet eine lineare Druck-Strom-Abhängigkeit zeigt. Dabei wird von der verstärkenden Wirkung der negativen Widerstandcharakteristik eines Thermistors Gebrauch gemacht, um die von winzigen Druckänderungen herrührenden kleinen Widerstandvariationen zu verstärken. 相似文献