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81.
Lee G. Moradi James S. Davidson Robert J. Dinan 《Canadian Metallurgical Quarterly》2008,22(3):131-142
This paper first describes the current state of analysis for the response of unreinforced concrete masonry walls subjected to lateral uniform pressure. The formulation is based on the initial elastic response, the subsequent initiation of cracks and the nonlinear rocking response, and the eventual large displacement and potential collapse. The necessary equations are developed for these phases in the form of a resistance function. The paper then incorporates membrane retrofit materials to strengthen the wall’s resistance to lateral pressure, and develops the necessary resistance function equations. In blast tests, membrane retrofit unreinforced masonry walls have experienced severe cracking and large displacements without collapse. This is of high interest to the Department of Defense, the protection of diplomatic facilities, and the construction industry impacted by hurricanes and other high wind events. The paper concludes with examples that demonstrate application of membrane retrofits indeed increase the resistance of the wall to lateral pressure. 相似文献
82.
J. N. Johnson L. A. Almeida M. Martinka J. D. Benson J. H. Dinan 《Journal of Electronic Materials》1999,28(6):817-820
Without any additional preparation, Cd1−yZnyTe (211)B (y∼3.5%) wafers were cleaned by exposure to an electron cyclotron resonance (ECR) Ar/H2 plasma and used as substrates for HgCdTe molecular beam epitaxy. Auger electron spectra were taken from as-received wafers,
conventionally prepared wafers (bromine: methanol etching, followed by heating to 330–340°C), and wafers prepared under a
variety of ECR process conditions. Surfaces of as-received wafers contained ∼1.5 monolayers of contaminants (oxygen, carbon,
and chlorine). Conventionally prepared wafers had ∼1/4 monolayer of carbon contamination, as well as excess tellurium and/or
excess zinc depending on the heating process used. Auger spectra from plasma-treated CdZnTe wafers showed surfaces free from
contamination, with the expected stoichiometry. Stoichiometry and surface cleanliness were insensitive to the duration of
plasma exposure (2–20 s) and to changes in radio frequency input power (20–100 W). Reflection high energy electron diffraction
patterns were streaked indicating microscopically smooth and ordered surfaces. The smoothness of plasma-etched CdZnTe wafers
was further confirmed ex situ using interferometric microscopy. Surface roughness values of ∼0.4 nm were measured. Characteristics of HgCdTe epilayers
deposited on wafers prepared with plasma and conventional etching were found to be comparable. For these epilayers, etch pit
densities on the order of 105 cm−2 have been achieved. ECR Ar/H2 plasma cleaning is now utilized at Night Vision and Electronic Sensors Directorate as the baseline CdZnTe surface preparation
technique. 相似文献
83.
N. K. Dhar P. R. Boyd M. Martinka J. H. Dinan L. A. Almeida N. Goldsman 《Journal of Electronic Materials》2000,29(6):748-753
Tellurium adsorption studies were made on clean and arsenic passivated (112) silicon surfaces. Quantitative surface coverage
values for tellurium were determined by Auger electron spectroscopy. Saturation coverage of up to 1.2 monolayers of tellurium
could be obtained on a clean (112) silicon surface. On an arsenic passivated (112) Si surface however, the tellurium saturation
coverage was limited to only ∼0.3 monolayer. Analysis of the adsorption behavior suggested that tellurium and arsenic chemisorption
occurs preferentially at step edges and on terraces, respectively. The study revealed that arsenic passivation led to a significant
decrease in the sticking coefficient of tellurium and an increase in it’s surface mobility. A model describing zinc telluride
nucleation on a (112) Si surface is proposed. Thin templates of ZnTe followed by Cd1−xZnxTe layers were deposited on (112) Si by molecular beam epitaxy (MBE). The characteristics of the MBE Cd1−xZnxTe layers were found to be sensitive to the initial ZnTe nucleation and Si surface preparation. 相似文献
84.
85.
J. B. Varesi J. D. Benson M. Martinka A. J. Stoltz W. E. Mason L. A. Almeida A. W. Kaleczyc P. R. Boyd J. H. Dinan 《Journal of Electronic Materials》2005,34(6):758-761
We have examined the etching of HgCdTe (x=0.2) with bromine/ethylene glycol (Br/EG) solutions. Using a spectroscopic ellipsometer,
we tracked the ellipsometric parameters (ψ and Δ) of the freshly etched HgCdTe surfaces. Parameters ψ and Δ were measured
periodically as these values changed with the surface exposed to air. A second set of Br/EG-etched samples was stored in deionized
(DI) water. We found that DI water effectively preserved the freshly etched HgCdTe surface for a period of several hours.
Comparison with the literature on HgCdTe surface chemistry implies that oxide growth is inhibited on the etched HgCdTe samples
immersed in DI water. Modeling results based on the measured ψ and Δ values agree with this assessment. 相似文献
86.
L. A. Almeida M. Thomas W. Larsen K. Spariosu D. D. Edwall J. D. Benson W. Mason A. J. Stoltz J. H. Dinan 《Journal of Electronic Materials》2002,31(7):669-676
We report the development and fabrication of two-color mid-wavelength infrared (MWIR) and short-wavelength infrared (SWIR)
HgCdTe-based focalplane arrays (FPAs). The HgCdTe multilayers were deposited on bulk CdZnTe (ZnTe mole fraction ∼3%) using
molecular beam epitaxy (MBE). Accurate control of layer composition and growth rate was achieved using in-situ spectroscopic
ellipsometry (SE). Epilayers were evaluated using a variety of techniques to determine suitability for subsequent device processing.
These techniques included Fourier transform infrared (FTIR) spectroscopy, Hall measurement, secondary ion mass spectroscopy
(SIMS), defect-decoration etching, and Nomarski microscopy. The FTIR transmission measurements confirmed SE’s capability to
provide excellent compositional control with run-to-run x-value variations of ∼0.002. Nomarski micrographs of the as-grown
surfaces featured cross-hatch patterns resulting from the substrate/epilayer lattice mismatch as well as various surface defects
(voids and “microvoids”), whose densities ranged from 800–8,000 cm−2. A major source of these surface defects was substrate particulate contamination. Epilayers grown following efforts to reduce
these particulates exhibited significantly lower densities of surface defects from 800–1,700 cm−2. Dislocation densities, as revealed by a standard defect-decoration etch, were 2–20×105 cm−2, depending on substrate temperature during epitaxy. The FPAs (128×128) were fabricated from these epilayers. Preliminary
performance results will be presented. 相似文献
87.
J. D. Benson A. J. Stoltz A. W. Kaleczyc M. Martinka L. A. Almeida P. R. Boyd J. H. Dinan 《Journal of Electronic Materials》2002,31(7):822-826
The factors that affect the trench width and aspect ratio in electron-cyclotron resonance (ECR) etched HgCdTe and CdTe are
investigated. The ECR etch bias and anisotropy are found to be predominately determined by the photoresist feature-erosion
rate. The physical characteristics of the trenches are attributed to ECR plasma-etch chemistry. A method for fabricating high
aspect-ratio, HgCdTe isolation trenches is demonstrated through a combination of advanced photolithography and ECR etching. 相似文献
88.
Humayun Arafat James Dinan Sriram Krishnamoorthy Pavan Balaji P. Sadayappan 《Concurrency and Computation》2016,28(13):3637-3654
Task parallelism is an attractive approach to automatically load balance the computation in a parallel system and adapt to dynamism exhibited by parallel systems. Exploiting task parallelism through work stealing has been extensively studied in shared and distributed‐memory contexts. In this paper, we study the design of a system that uses work stealing for dynamic load balancing of task‐parallel programs executed on hybrid distributed‐memory CPU‐graphics processing unit (GPU) systems in a global‐address space framework. We take into account the unique nature of the accelerator model employed by GPUs, the significant performance difference between GPU and CPU execution as a function of problem size, and the distinct CPU and GPU memory domains. We consider various alternatives in designing a distributed work stealing algorithm for CPU‐GPU systems, while taking into account the impact of task distribution and data movement overheads. These strategies are evaluated using microbenchmarks that capture various execution configurations as well as the state‐of‐the‐art CCSD(T) application module from the computational chemistry domain. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
89.
90.
Effects of hydrogen on majority carrier transport and minority carrier lifetimes in long-wavelength infrared HgCdTe on Si 总被引:4,自引:0,他引:4
P. Boieriu C. H. Grein J. Garland S. Velicu C. Fulk A. Stoltz L. Bubulac J. H. Dinan S. Sivananthan 《Journal of Electronic Materials》2006,35(6):1385-1390
We present extended results on the use of a hydrogen plasma to passivate the effects of defects in long-wave ir HgCdTe/Si.
Annealed and as-grown epilayers, in situ doped with indium, were exposed to a hydrogen plasma generated in an electron cyclotron
resonance (ECR) reactor. Secondary ion mass spectrometry was used to measure the extent of hydrogen incorporation into the
epilayers. Hall and photoconductive lifetime measurements were used to assess the efficacy of passivation. The passivation
of defects responsible for the scattering and recombination of electrical carriers was observed for most ECR conditions over
a range of dislocation densities. 相似文献