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31.
This paper presents a new hybrid dc circuit breaker producing no conducting power loss under normal operating conditions and having the capability to interrupt a large amount of short‐circuiting current within several milliseconds. It consists of two reactors for current limiting and current control, two mechanical contactors, and a multilevel converter based on the cascade connection of multiple full‐bridge dc/dc converter cells. It is characterized by achieving current commutation from the main mechanical contactor to the multilevel converter with fast current control. This results in eliminating auxiliary power semiconductor switches that produce a nonnegligible conducting power loss under normal operating conditions. This paper discusses both principles of operation and control method of the new hybrid dc circuit breaker. Experimental verification is performed by a downscaled system rated at 300 V and 150 A, along with verification by computer simulation.  相似文献   
32.
Phosphatidylethanolamine (PE), which contains highly unsaturated fatty acid (HUFA) specifically in sn -2 position, was synthesized by porcine pancreatic phospholipase A2-catalysed esterification of lysophosphatidylethanolamine with HUFA. the use of glycerol containing only a little water as solvent was the important key to this reaction. A 27% yield of up to 94.5% sn -2 eicosapentaenoic acid (EPA)-containing PE was obtained using >99% EPA as a substrate HUFA.  相似文献   
33.
A mixture of casein and methyl linoleate was stored at 50°C and 80% relative humidity for 0 - 14 days and damage to amino acid residues assessed. The damage was estimated by determining the amino acid composition of the hydrolysate by using proteolytic enzymes (pepsin-pancreatin digestion, followed by aminopeptidase-prolidase hydrolysis). The damage to amino acid residues was the most extensive in methionine, followed by tryptophan, histidine, and lysine. The degree of damage to these amino acids was also determined by chemical methods without using proteolytic enzymes. The efficiency of detecting damage by the present enzymatic method was close to that of the chemical methods.  相似文献   
34.
The microscopic mechanism of a demixing of binary oxide solid solution in an oxidizing atmosphere under a temperature gradient is investigated by the path probability method of irreversibly statistical mechanics. The problem is reduced to a steady-state metal ion transport under the coexistence of an oxygen partial pressure gradient and a temperature gradient. Calculations are performed under two different conditions: (i) demixing in a steady-state diffusion process under the two driving forces and (ii) a redistribution of constituent metal ions in a closed system under a given temperature gradient (Soret effect). The results can be interpreted as the superposition of the contributions of two driving forces plus a cross term which tends to zero as the driving forces become small. The difference between these two cases is discussed in detail and some controversies in the past work with respect to the difference are pointed out.  相似文献   
35.
We describe the construction and characterization of a laser‐line‐scanning microscope capable of detection of broad fluorescence spectra with a resolution of 1 nm. A near‐infrared femtosecond pulse train at 800 nm was illuminated on a line (one lateral axis, denoted as X axis) in a specimen by a resonant scanning mirror oscillating at 7.9 kHz, and total multi‐photon–induced fluorescence from the linear region was focused on the slit of an imaging polychromator. An electron‐multiplying CCD camera was used to resolve fluorescence of different colours at different horizontal pixels and fluorescence of different spatial positions in a specimen at different vertical pixels. Scanning on the other two axes (Y and Z) was achieved by a closed‐loop controlled sample scanning stage and a piezo‐driven objective actuator. The full widths at half maximum of the point‐spread function of the system were estimated to be 0.39–0.40, 0.33 and 0.56–0.59 μm for the X (lateral axis along the line‐scan), Y (the other lateral axis) and Z axes (the axial direction), respectively, at fluorescence wavelengths between 644 and 690 nm. A biological application of this microscope was demonstrated in a study of the sub‐cellular fluorescence spectra of thylakoid membranes in a cyanobacterium, Anabaena PCC7120. It was found that the fluorescence intensity ratio between chlorophyll molecules mainly of photosystem II and phycobilin molecules of phycobilisome (chlorophyll/phycobilin), in the thylakoid membranes, became lower as one probed deeper inside the cells. This was attributable not to position dependence of re‐absorption or scattering effects, but to an intrinsic change in the local physiological state of the thylakoid membrane, with the help of a transmission spectral measurement of sub‐cellular domains. The efficiency of the new line‐scanning spectromicroscope was estimated in comparison with our own point‐by‐point scanning spectromicroscope. Under typical conditions of observing cyanobacterial cells, the total exposure time became shorter by about 50 times for a constant excitation density. The improvement factor was proportional to the length of the line‐scanned region, as expected.  相似文献   
36.
This paper presents an approach to high‐precision sensorless force control for positioning devices that engage in a contact operation. The sensorless force control is designed with a sliding mode controller and contact model that provide the required control specifications to compensate for the nonlinear spring characteristics of the contact mechanism. The effectiveness of the proposed control approach was verified through numerical simulations and experiments using a prototype.  相似文献   
37.
The Si resonator is applied for measuring the voltage in a highly isolated manner. The working principle is based on the resonant frequency shift caused by the electrical field from the electrode connected to the high‐voltage source (supposing the battery). Here, the resonator is electrically floated, and its potential is decided by the relative position against the electrodes which are connected to the high voltage and the driving voltage. The induced voltage on the resonator is analyzed against the driving frequency. The resonance is found by the paired peaks in the amplitude curve. The setup for the electrical measurement can make the sensor system compact. A new sensor design for avoiding the electrical field concentration realizes the measurement over 400 V without the breakdown. This will match with the high‐voltage dc power supply system.  相似文献   
38.
Effect of sugars on the stabilization of hen egg yolk immunoglobulin (IgY) under various processing conditions was investigated. By adding 30–50% (w/v) sucrose or invert sugar to an IgY solution heat denaturation of the IgY antibody at 75–80°C was markedly suppressed. A high concentration of sugar was also effective to retain the IgY activity under acidic conditions of pH 3 or high pressure of 5,000 kg/cm2 at 60°C. Addition of high concentrations of sucrose may be a simple means to stabilize IgY for processing and preservation.  相似文献   
39.
A peptide corresponding to the 23 N-terminal residues of αs1-casein, αs1(1-23), was purified from a peptic hydrolyzate of αs1-casein. The emulsifying activity of αs1(1-23) varied depending on the concentration. When the concentration was higher than 2%, αs1(1-23) showed a similar emulsifying activity to αs1-casein in neutral pHs. The emulsion capacity of αs1(1-23) was about one half that of αs1-casein. The extent of adsorption of αs1(1-23) onto the oil globule surface was markedly high. In the acidic pH region (pH 5.5 – 3.0), αs1(1-23) maintained a high emulsifying activity, whereas αs1-casein lost its emulsifying activity. These results suggest that αs1(1-23) acts as an emulsifying agent and probably can be used in some foods such as processed cheese or fermented milk products.  相似文献   
40.
Semiconductive Trimethylamine Gas Sensor for Detecting Fish Freshness   总被引:3,自引:0,他引:3  
Characteristics were studied on In2O3 treated with 5 mol% MgO responses to 300 ppm trimethylamine (TMA), dimethylamine (DMA), ammonia and other gases evolved from several different fish muscles stored under different conditions. Sensitivities of the In2O3-MgO sensor element were higher in order of TMA, DMA and ammonia over the operating range 330–620°C. Sensor responses were directly proportional to concentrations of TMA in fish muscle in the presence of other evolved gases, irrespective of types of fish muscle or storage time.  相似文献   
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