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1.
Wolfgang Sachse A. N. Netravali A. Richard Baker 《Journal of Nondestructive Evaluation》1992,11(3-4):251-261
In the single-fiber-composite (SFC) test, a fiber imbedded in a matrix is loaded in tension, resulting in a fragmentation of the fiber. In the conventional version of this test, the final fiber fragmentation length distribution is used with a micro-mechanical model to determine the average fiber/matrix interfacial shear stress. In the enhanced version of this test, one also determines the applied stress at each fiber fracture, and from this, one can evaluate the strength of the fiber at short gage lengths. In our measurement system, we utilize an acoustic emission (AE) technique to detect the fiber fractures and to locate the fiber breaks and so determine both the fiber failure stresses as well as the fiber fragmentation lengths while the test is in progress. Critical to the success of this test is a broadband AE system that utilizes point-like AE sensors, procedures for evaluatingin situ, the wavespeed of the first wave arrival and signal processing techniques for determining the arrival time of this signal as precisely as possible for a broad range of wave shapes. Here we describe the application of such an enhanced SFC test procedure to investigate the failure of a Nicalon fiber in an epoxy matrix. 相似文献
2.
A new stripline-fed aperture coupled antenna element is proposed. An additional slot in a ground plane allows achievement of efficient electromagnetic coupling with the radiating element and good return loss of the antenna fed by a stripline. The described radiating elements can be easily integrated with a feeding network designed in the most commonly used stripline technique when a large antenna array is to be developed. 相似文献
3.
4.
The antennal lobe plays a central role for odor processing in insects, as demonstrated by electrophysiological and imaging experiments. Here we analyze the detailed temporal evolution of glomerular activity patterns in the antennal lobe of honeybees. We represent these spatiotemporal patterns as trajectories in a multidimensional space, where each dimension accounts for the activity of one glomerulus. Our data show that the trajectories reach odor-specific steady states (attractors) that correspond to stable activity patterns at about 1 second after stimulus onset. As revealed by a detailed mathematical investigation, the trajectories are characterized by different phases: response onset, steady-state plateau, response offset, and periods of spontaneous activity. An analysis based on support-vector machines quantifies the odor specificity of the attractors and the optimal time needed for odor discrimination. The results support the hypothesis of a spatial olfactory code in the antennal lobe and suggest a perceptron-like readout mechanism that is biologically implemented in a downstream network, such as the mushroom body. 相似文献
5.
The scattering matrix of asymmetric coupled two-line structures in an inhomogeneous medium terminated in a set of impedances that are equal to the characteristic impedances of the individual, uncoupled lines is derived in terms of the coupled-mode parameters. It is shown that the structures can compose an ideal backward-coupling directional coupler, perfectly matched and isolated at all frequencies, if the inductive k L and capacitive kC coupling coefficients of the coupled lines are equal. The effect of the nonideal equalization of the coupling coefficients on the coupler critical parameters is investigated. The normal-mode parameters (mode numbers and mode impedances) in the proximity of the point when kL=kC and at that point are also examined. Numerical results confirm the validity of the analysis and prove the possibility of an asymmetrical coupler design with very high directivity 相似文献
6.
Niederer SA Kerfoot E Benson AP Bernabeu MO Bernus O Bradley C Cherry EM Clayton R Fenton FH Garny A Heidenreich E Land S Maleckar M Pathmanathan P Plank G Rodríguez JF Roy I Sachse FB Seemann G Skavhaug O Smith NP 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1954):4331-4351
Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future. 相似文献
7.
Design is described as creative design problem solving. The first step of the design process is to identify and analyze the
design problem. This step has an important influence on the creation of an effective design solution. In two experiments,
we tested the benefits that sketching provides during the analysis process in design problem solving. In particular, this
paper focuses on the design process, the act of sketching, the sketch itself, and the final product. In prior studies, the
process of sketching has been shown to enhance the construction of a mental representation, and thus the sketch has improved
the analysis of the problem. The memory supporting effect of sketches is verified in the second experiment discussed in this
paper. Finally, this paper also discusses the support possibilities the sketch offers for the early stages of the design process. 相似文献
8.
Cytochrome P450 2D6 (CYP2D6) metabolizes many important drugs. CYP2D6 activity ranges from complete deficiency to ultrafast metabolism, depending on at least 16 different known alleles. Their frequencies were determined in 589 unrelated German volunteers and correlated with enzyme activity measured by phenotyping with dextromethorphan or debrisoquine. For genotyping, nested PCR-RFLP tests from a PCR amplificate of the entire CYP2D6 gene were developed. The frequency of the CYP2D6*1 allele coding for extensive metabolizer (EM) phenotype was .364. The alleles coding for slightly (CYP2D6*2) or moderately (*9 and *10) reduced activity (intermediate metabolizer phenotype [IM]) showed frequencies of .324, .018, and .015, respectively. By use of novel PCR tests for discrimination, CYP2D6 gene duplication alleles were found with frequencies of .005 (*1x2), .013 (*2x2), and .001 (*4x2). Frequencies of alleles with complete deficiency (poor metabolizer phenotype [PM]) were .207 (*4), .020 (*3 and *5), .009 (*6), and .001 (*7, *15, and *16). The defective CYP2D6 alleles *8, *11, *12, *13, and *14 were not found. All 41 PMs (7.0%) in this sample were explained by five mutations detected by four PCR-RFLP tests, which may suffice, together with the gene duplication test, for clinical prediction of CYP2D6 capacity. Three novel variants of known CYP2D6 alleles were discovered: *1C (T1957C), *2B (additional C2558T), and *4E (additional C2938T). Analysis of variance showed significant differences in enzymatic activity measured by the dextromethorphan metabolic ratio (MR) between carriers of EM/PM (mean MR = .006) and IM/PM (mean MR = .014) alleles and between carriers of one (mean MR = .009) and two (mean MR = .003) functional alleles. The results of this study provide a solid basis for prediction of CYP2D6 capacity, as required in drug research and routine drug treatment. 相似文献
9.
Yong Hyun Kim Christoph Sachse Michael L. Machala Christian May Lars Müller‐Meskamp Karl Leo 《Advanced functional materials》2011,21(6):1009-1009
Highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as stand‐alone electrodes for organic solar cells have been optimized using a solvent post‐treatment method. The treated PEDOT:PSS films show enhanced conductivities up to 1418 S cm?1, accompanied by structural and chemical changes. The effect of the solvent treatment on PEDOT:PSS has been investigated in detail and is shown to cause a reduction of insulating PSS in the conductive polymer layer. Using these optimized electrodes, ITO‐free, small molecule organic solar cells with a zinc phthalocyanine (ZnPc):fullerene C60 bulk heterojunction have been produced on glass and PET substrates. The system was further improved by pre‐heating the PEDOT:PSS electrodes, which enhanced the power conversion efficiency to the values obtained for solar cells on ITO electrodes. The results show that optimized PEDOT:PSS with solvent and thermal post‐treatment can be a very promising electrode material for highly efficient flexible ITO‐free organic solar cells. 相似文献
10.
The effect of RF sputter etching on the (111) surface of silicon was studied by observing backscatter spectra from a 2 MeV, 4He+ beam oriented along the silicon 〈111〉 channel. Silicon samples were RF sputter etched in a 5 × 10?3 torr, argon discharge at electrode bias potentials ranging from 0.5 to 2.5 kV. The samples were sputter etched for a time sufficient for the lattice damage to reach saturation. Analysis of these samples revealed that the thickness of this damage layer and the concentration of trapped argon increased with electrode bias potential. An annealing study of these damaged surfaces was carried out to 900°C. 相似文献