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排序方式: 共有103条查询结果,搜索用时 15 毫秒
1.
A cartographic-oriented model uses algebraic map operations to perform spatial analysis of medical data relative to the human body. A prototype system uses 3D visualization techniques to deliver analysis results. A prototype implementation suggests the model might provide the basis for a medical application tool that introduces new information insight.  相似文献   
2.
In this paper, the density functional theory (DFT) within the generalized gradient approximation (GGA) was used. The single crystal elastic constants for the intermetallic FeTi and its hydrides FeTiH and FeTiH2 are successfully obtained from the stress–strain relationship calculations and the strain energy-strain curves calculations, respectively. The shear modulus, Young's modulus, Poisson's ratio and shear anisotropic factors are also calculated. The bulk moduli derived from the elastic constants calculations of the cubic FeTi, orthorhombic P2221 FeTiH and Cmmm FeTiH2 are calculated. For cubic FeTi compound, the bulk modulus is in a good agreement with both theoretical results and experimental data available in the literature. More importantly, it is found that, the insertion of hydrogen into the FeTi crystal structure causes an increase in the bulk modulus. From the analysis of shear-to-bulk modulus ratio, it is found that FeTi compound and its hydrides are ductile and that this ductibility, changes with changing the concentration of hydrogen.  相似文献   
3.
An extended state observer (ESO)-based loop flter is designed for the phase-locked loop (PLL) involved in a disturbed gridconnected converter (GcC). This ESO-based design enhances the performances and robustness of the PLL, and, therefore, improves control performances of the disturbed GcCs. Besides, the ESO-based LF can be applied to PLLs with extra flters for abnormal grid conditions. The unbalanced grid is particularly taken into account for the performance analysis. A tuning approach based on the well-designed PI controller is discussed, which results in a fair comparison with conventional PItype PLLs. The frequency domain properties are quantitatively analysed with respect to the control stability and the noises rejection. The frequency domain analysis and simulation results suggest that the performances of the generated ESO-based controllers are comparable to those of the PI control at low frequency, while have better ability to attenuate high-frequency measurement noises. The phase margin decreases slightly, but remains acceptable. Finally, experimental tests are conducted with a hybrid power hardware-in-the-loop benchmark, in which balanced/unbalanced cases are both explored. The obtained results prove the efectiveness of ESO-based PLLs when applied to the disturbed GcC.  相似文献   
4.
A Real-coded Genetic Algorithm has been used to develop a new correlation to estimate the enthalpy of vaporization for pure compounds and petroleum fractions as a function of the normal boiling point and specific gravity. In developing the correlation 80% of the data was used and the remaining are used for validation. The results of the proposed correlations are compared to others in literature. The comparison indicates that the proposed model is simple to use and more accurate than the most common correlations for predicting the enthalpy of vaporization of pure compounds and petroleum fractions.  相似文献   
5.
Potentiodynamic polarization and cyclic voltametry measurements were employed to study the effect of topical fluoride preparations on corrosion of silver amalgam alloy in synthetic saliva and aqueous fluoride solutions. Results support that small amounts of copper and indium alloyed to silver – tin amalgam enhance corrosion resistance considerably. Indiloy shifts both the open circuit potential and the anodic polarization curve to more positive potential values, this lead to a decreases in the current density. The weak activity of Indiloy as compared with Spheraloy is attributed to the fact that the amount of γ2 phase (tin–mercury) present in the former is much lesser than that present in the latter. Findings also show that fluoride solutions (NaF, SnF and SnF + HCI) enhance the dissolution rate of the investigasted alloys and the polarization curves illustrate the appearance of an active – passive transitions. This behaviour was discussed on the basis of complex formation. Cyclic voltammograms confirm the results obtained from the potentiodynamic polarization measurements and elucidate the anodic oxidation peaks of silver oxide and copper verifying the proposed mechanism.  相似文献   
6.
An extended state observer(ESO)-based loop filter is designed for the phase-locked loop(PLL)involved in a disturbed grid-connected converter(GcC).This ESO-based...  相似文献   
7.
Changes in bacterial counts on beef carcasses at specific points during slaughter and fabrication were determined, and the effectiveness of nisin, lactic acid, and a combination of the lactic acid and nisin in reducing levels of microbiological contamination was assessed. Swab samples were obtained from the surfaces of randomly selected beef carcasses. Carcasses were swabbed from the neck, brisket, and renal site after skinning, splitting, and washing. Treatments involving lactic acid (1.5%), nisin (500 IU/ml), or a mixture of nisin and lactic acid were applied after the neck area was washed. A control group was not sprayed. Results indicated that the highest prevalence of aerobic plate counts (APCs), total coliforms, and Escherichia coli was found in the neck site after splitting, and the lowest level of microbial contamination was found after skinning. Washing with water did not significantly reduce the bacterial load. The largest reduction in APCs, total coliforms, and E. coli occurred on carcasses treated with a mixture of nisin and lactic acid. A mixture of nisin and lactic acid can be applied to beef carcasses through spray washing and can reduce bacterial populations by 2 log units.  相似文献   
8.
Experiments showed that a crushed groundnut–chickpea–sesame (3:2:1) mixture is an adequate source of protein comparable with casein as a constituent of a 20% protein diet for promoting growth and nitrogen retention in young rats, synthesis of their serum proteins and haemoglobin, their maturation, reproduction, lactation and breeding of three generations of normal healthy animals.  相似文献   
9.
A key challenge in the design of real-time wireless multimedia systems is the presence of fading coupled with strict delay constraints. A very effective answer to this problem is the use of diversity achieving techniques to overcome the fading nature of the wireless channels caused by the mobility of the nodes. The mobility of the nodes gives rise to the need of cooperation among the nodes to enhance the system performance. This paper focuses on comparing systems that exhibit diversity of three forms: source coding diversity, channel coding diversity, and user cooperation diversity implemented through multihop or relay channels with amplify-and-forward or decode-and-forward protocols. Commonly used in multimedia communications, performance is measured in terms of the distortion exponent, which measures the rate of decay of the end-to-end distortion at asymptotically high signal-to-noise ratio (SNR). For the case of repetition coding at the relay nodes, we prove that having more relays is not always beneficial. For the general case of having a large number of relays that can help the source using repetition coding, the optimum number of relay nodes that maximizes the distortion exponent is determined in this paper. This optimum number of relay nodes will depend on the system bandwidth as well as the channel quality. The derived result shows a trade-off between the quality (resolution) of the source encoder and the amount of cooperation (number of relay nodes). Also, the performances of the channel coding diversity-based scheme and the source coding diversity-based scheme are compared. The results show that for both relay and multihop channels, channel coding diversity provides the best performance, followed by the source coding diversity.  相似文献   
10.
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