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21.
Diffraction grating scanners using polysilicon micromotors 总被引:1,自引:0,他引:1
Azzam Yasseen A. Smith S.W. Merat F.L. Mehregany M. 《IEEE journal of selected topics in quantum electronics》1999,5(1):75-82
This paper describes polysilicon micromotors with single and pyramidal diffraction grating elements fabricated on the polished surface of large-area rotors for optical scanning applications. While taking full advantage of planar processing, such scanners have high-quality scan profiles, good efficiency, meter working distances, and multiple out of plane beam diffraction orders. Chemical-mechanical polishing was used to reduce the 5-μm-thick polysilicon rotors' average surface roughness from 420 Å to below 17 Å, with less than 1500-Å film removal, improving the optical performance of the gratings as well as the definition, delineation, and side wall quality of the device features. Self-assembled monolayers (SAM) were found to improve the overall micromotor's dynamic performance. SAM-coated scanners could operate at voltages as low as 15 V and maximum operational speeds of 5200 rpm. The gratings were tested optically at 633-nm wavelength and were verified to have spatial periods of 1.80 and 3.86 μm, closely matching their design values. Stepping and continuous mode dynamic operation of the scanners was demonstrated with visible diffraction orders at meter distances away 相似文献
22.
Kamal Al-Malah Mohammed O. J. Azzam Nehal I. Abu-Lail 《Separation and Purification Technology》2000,20(2-3):225-234
Olive mill effluent (OME) wastewater embodies a challenge for environmental scientists and engineers. It is characterized by high values of COD, BOD, and phenolic content. A series of treatment steps composed of settling, centrifugation, and filtration was consecutively used to condition OME wastewater. The filtrate was then subjected to a post-treatment process, namely adsorption on activated clay. The dynamic response of phenols concentration, pH, and COD, using different concentrations of activated clay, showed a peak at which maximum adsorption capacity was achieved. The maximum adsorption capacity for the tested concentrations of activated clay was reached in less than 4 h. It is thought that adsorption of phenols and organics is reversible and mainly due to hydrophobic interactions. The maximum removal of phenols was about 81%, while it reached about 71% for organic matter. 相似文献
23.
A new algorithm for subcube assignment and decomposition is introduced to solve the fragmentation problem in hypercube (n-cube) processor allocation. The sharing density vector introduced in the prime cube graph strategy is used as a vehicle to develop the new algorithm. A bit decision table is devised to provide the key parameters for determining the decomposition. It is proven that the result of the algorithm is at least 22% better than the sharing density vector approach.<> 相似文献
24.
Potentiodynamic anodic polarization curves have been traced for an electrode of the steel Delta-52 (0.40, 0.78Mn, 0.045 S, 0.06P, 0.23 Si): the aggresive media used were potassium hydroxide without and with additions of potassium chloride, bromide and iodide. The oxide film present on the steel surface does not inhibit active dissolution; only at potentials exceeding+2 (S. C. E.) passivity sets in. The polarization behaviour of the steel is not influenced by the addition of the halide salts; above a certain salt concentration, however, there is a sharp increase in dissolution current. This phenomenon is an indication of the start of pitting. Between the pitting potential and the anion concentration there exists a well defined relation. 相似文献
25.
R M Azzam 《Microscopica acta》1979,81(4):313-316
A need exists for new experimental approaches for the direct detection of cell-surface changes associated with malignant transformations. The usual methods of fractionating the cell to obtain plasma-membrane segments are disruptive and are influenced by uncertainties that frustrate most attempts to distinguish between the cell memebrane in the normal and malignant states. Here we describe a non-destructive microprobe technique using a light beam to monitor cell-surface changes in situ. Many investigations of tumor-cell behavior in culture are based on substrate-adherent populations of cells. By choosing the substrate to be optically dense and transparent, and by striking the substrate/cell interface by a light beam from the substrate side at an angle of incidence greater than the critical angle of total-internal reflection, an evanescent electromagnetic wave interacts with the peripheral zone of the substrate-adherent cells. Both the intensity and ellipse of polarization of the reflected wave can be monitored as the malignant transformation takes place, either chemically or virally. This technique should also provide new information concerning the molecular organization of the cell periphery from measurements on living cells. 相似文献
26.
W. R. Azzam 《应用聚合物科学杂志》2012,123(1):299-306
This article describes the application of using polymer stabilization to create a new hydrophobic (nanocomposite) material with swollen clay. A series of tests were performed with different polymer contents to study the effect of using polypropylene as a partial soil stabilizer and a shrinkage–swelling modifier for expansive soils. The effect of the obtained clay–polymer nanocomposites on the shear strength of swelling soils was also investigated. The tests showed that the resulting nanocomposites acted as nanofiller materials and decreased both the plasticity index and permeability. The optimum moisture content and dry density decreased relatively with increasing polymer content. The polymer inclusions significantly reduced the free swelling and swelling pressure values. In addition, the produced nanocomposites reduced the volumetric shrinkage of the expansive soils and created isotropic and compressible materials. The unconfined compressive strength of the soil increased significantly with increasing polymer content. The proposed stabilized technique increased the bearing capacity under the model footing and modified the stress settlement relationship. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
27.
Noureddine Azzam Julien Chaves-Jacob Salim Boukebbab Jean-Marc Linares 《The International Journal of Advanced Manufacturing Technology》2014,72(5-8):1073-1083
This study proposes a method to adapt the geometry of the toolpath to a specified target. In the case study presented, the geometrical target is to remove a constant thickness on the rough workpiece. This case is normally present in the polishing of the femoral component of knee prostheses. In fact, an operator carries out these operations manually. The aim of this study is to contribute to the automation of prosthesis production, notably, in the preparation of surface polishing. The proposed method can deform and adapt a toolpath to ensure the required geometry of the machined surface. The proposed toolpath deformation method is composed of three steps: alignment, toolpath deformation, and toolpath smoothing. Alignment between the measured surface of the roughcast prostheses and the nominal toolpath is carried out by an Iterative Closest Point (ICP) algorithm. The principle of this algorithm is to find the optimal rigid transformation to readjust the toolpath on the measured surface. Subsequently, the toolpath is deformed to remove the constant thickness of the roughcast prostheses. Next, to increase the machined quality, a smoothing stage is carried out on the obtained toolpath. Experimental tests on industrial prostheses geometry are conducted to validate the effectiveness of this method. 相似文献
28.
Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t50 is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration Cmax in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C0 at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t25%-t75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t25%-t50%) / (t25%-t75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed. 相似文献
29.
30.
Anodic destruction of 4-chlorophenol solution 总被引:2,自引:0,他引:2
The electrochemical oxidation of 4-chlorophenol solutions was studied using a dimensional stable anode (DSA), made of pure titanium sheet mesh coated with Ti/TiO(2) and RuO(2) film. An electrochemical cell with one working electrode and two counter-electrodes was designed. A gas collecting system to collect the electrolysis gaseous products was also designed. The influence of current density (6.51-21.58 mA/cm(2)), pH (2.0-12.6) and initial 4-chlorophenol concentration (25-100 mg/l) on the destruction was investigated. Complete elimination was successfully achieved within 2 h for most investigated conditions. Highest rates of elimination were achieved at a pH of 12.6.A new approach to calculate the current efficiency (CE) of the cell was proposed. The volumes of the gases produced at the anode and at the cathode were the basis for the new CE calculations. It was observed that the worst CE was approximately 20% and the best CE was approximately 89%. The most efficient pH was at 12.6 and the most efficient current density was at 11.39 mA/cm(2). 相似文献