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排序方式: 共有144条查询结果,搜索用时 15 毫秒
1.
This paper presents a new method for balancing voltages of series-connected insulated gate bipolar transistors (IGBTs). This method can be implemented only by adding simple circuits to the gate drive system of the IGBTs, and its effect of balancing the IGBT's collector-emitter voltages during the switching transients is remarkable. This principal strategy and experimental results with series-connected IGBTs are first described. After that, further experimental results are shown from the switching tests of four 2.5-kV flat-packaged IGBTs connected in series. Through the switching tests, superior characteristics of the proposed method have been confirmed. 相似文献
2.
Karima Rabaani Noureddine Boulejfen Ammar B. Kouki Fadhel M. Ghannouchi 《国际射频与微波计算机辅助工程杂志》2020,30(4)
A novel, low complexity approach for the analysis of nonuniform lossy substrate‐integrated waveguide transmission lines based on the method of moments is proposed. The approach uses frequency‐dependent basis functions derived from the structure's propagation characteristics. Two tapered structures are analyzed, fabricated, and measured to validate the proposed approach. The analytical results of the proposed approach for both structures are compared to those obtained by measurement and by three‐dimensional field simulation. Excellent agreement is observed between the three sets of results with simulation time savings on more than 98% and memory requirement reduction of more than 97%. 相似文献
3.
Syntheses of Spinon Thermal Conductivity Materials in Sr–Cu–O System by Glass‐Ceramics Technique 下载免费PDF全文
Nobuaki Terakado Yuudai Yokochi Kouki Watanabe Yoshihiro Takahashi Takumi Fujiwara 《Journal of the American Ceramic Society》2016,99(5):1565-1572
We have synthesized spinon thermal conductivity materials in Sr–Cu–O system by glass‐ceramics technique. The materials are promising for active control of thermal energy in microelectronic devices because of high and anisotropic thermal conduction, its controllability, and electric insulation. Nevertheless, research on these materials has been limited to that concerning theoretical perspectives and investigation of physical properties using large single crystals. In this study, we adopt glass‐ceramics technique to synthesize these materials: We prepared melt‐quenched multicomponent oxides including SrO and CuO, and checked its glass‐forming ability and crystallization behaviors by heating. As a result, we have found that SrCuO2 and Sr14Cu24O41, known as the spinon thermal conductivity materials, are synthesized using SrO–CuO–?Li2O–?Al2O3?–Ga2O3 system. This synthesis process for the system will provide practical application of the spinon thermal conductivity materials. 相似文献
4.
Yamamoto S Manabe N Fujioka K Hoshino A Yamamoto K 《IEEE transactions on nanobioscience》2007,6(1):94-98
Vitreous is transparent tissue located between the lens and the retina of the eye, thus, difficult to look at by even ophthalmological microscope. But vitreous is connected with some sight-threatening eye diseases, for example, retinal detachment, macular hole, epi-retinal membrane, and so forth. Quantum dots (QDs) have been applied to a wide range of biological studies by taking advantage of their fluorescence properties. We established a novel technique of aqueous colloidal QD (ACQD) as a vitreous lesion detector. When compared with some conventional dyes used for clinical situation, i.e. fluorescein, indocyanine green, and triamcinolone acetonide, ACQD exerted a higher performance to detect a Weiss Ring. Furthermore ACQD is also effective to perform vitrectomy, an eye surgery to cut and eliminate vitreous. Some functional structures in vitreous are detected clearly when ACQD was injected into an enucleated porcine eye. We demonstrated that ACQD enabled any ophthalmic surgeon to perform vitrectomy reliably, easily, and more safely. Taken together, the ACQD-oriented vitreous staining system will promote ophthalmological science, and it will raise the cure rate of eye diseases 相似文献
5.
With the application of an energy rebound circuit for the pulsewidth modulation (PWM)-controlled rectifier, an improved current source gate turn-off thyristor (GTO) inverter system capable of producing sinusoidal inputs and outputs is presented. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier for applying PWM control techniques and also to clamp the spike voltage produced in the inverter circuit. The principles and circuit operations of this system are described in detail, and requirements for PWM control of the rectifier are investigated. The conditions for satisfying the requirements of the energy rebound circuit are analyzed by experimental and theoretical methods. The PWM-controlled current source GTO inverter system is used to drive an eight-pole 400 Hz 5.5 kW induction motor. Analytical and experimental results, as well as the characteristics of the motor drives, are given 相似文献
6.
This paper presents a method to calculate the transient characteristics of synchronous reluctance motor (SynRM). Using an approximate equation suitable for expressing d- and q-axes inductance variation, the authors derive a nonlinear state equation considering both iron loss and cross-magnetic saturation. All electrical motor parameters used for the calculation are measured from tests. Calculation results on transient and steady-state characteristics of a vector-controlled flux-barrier-type 1.1-kW SynRM are verified with experimental results 相似文献
7.
Kaname Kanai Takahiro Miyazaki Takanori Wakita Kouki Akaike Takayoshi Yokoya Yukio Ouchi Kazuhiko Seki 《Advanced functional materials》2010,20(13):2046-2052
How annealing influences the morphology of a highly regioregular poly(3‐hexylthiophene) (RR‐P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high‐molecular‐weight (MW) RR‐P3HT films tend to show low crystallinity even after annealing, it is found that high‐MW RR‐P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X‐ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR‐P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high‐MW RR‐P3HT film. 相似文献
8.
A two-ray ground multipath deterministic model for worst-case fading-depth prediction in microwave link budget analysis is presented. Simple formulas, providing insight into fading depth as a function of geometrical and electrical parameters, are derived. A detailed analysis shows that, in many cases, the fading depth depends mainly on the path-clearance angle. Comparison with the Olsen-Segal model shows that both models have roughly the same path-clearance-angle factor. To the best of the authors' knowledge, this can be considered the first theoretical justification of the path elevation factor in the Olsen-Segal model 相似文献
9.
Kazuo Oka Kouki Matsuse 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(4):476-478
This paper presents a robust current control method with a disturbance observer for a matrix converter (MC) under an abnormal input voltage. The MC can directly convert power from an input alternating current (AC) source to a load without any direct current (DC) link. Since the MC has no reactive elements, the imbalance and distortion of the input voltage immediately influence the load. Therefore, a high‐performance current control of the load is impossible in this condition. In this letter, we propose a robust current control method for the MC under an abnormal input voltage. Adapting the disturbance observer to a load current control, current control is possible without the influence of the imbalance and distortion of the input voltage and of a fluctuation of a load paramerter, a resistance, an inductance and so on. This current control is robust under these conditions. The proposed method is effective for the application of a high‐performance AC motor drive employing vector control because it is necessary for the proposed method to coordinate with a reference frame. The validity of the proposed method is confirmed by simulation results. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
10.
Y Obase T Shimoda N Matsuo H Matsuse S Asai S Kohno 《Canadian Metallurgical Quarterly》1998,114(4):1028-1032
BACKGROUND: Leukotriene (LT) and thromboxane A2 (TXA2) receptor antagonists have been used in the treatment of asthma. OBJECTIVES: We examined the effects of an LT receptor antagonist, TXA2 receptor antagonist, and TXA2 synthetase inhibitor on bronchoprovocation test (BPT) in patients with mild-to-moderate atopic asthma. METHODS: BPT was performed four times in each of six asthmatics. Development of the immediate asthmatic reaction (IAR) and late asthmatic reaction (LAR) was confirmed on the first BPT (BPT1). After a 7-day washout period, an LT receptor antagonist (pranlukast, 450 mg/d), TXA2 receptor antagonist (seratrodast, 80 mg/d), or TXA2 synthetase inhibitor (ozagrel, 800 mg/d) was administered orally over 7 days at random using a cross-over method (BPT2-4). Blood levels of LTB4, LTC4, LTD4, 11-dehydrothromboxane B2, eosinophil cationic protein, and histamine were measured at reaction phases of pre-BPT, IAR, and LAR. RESULTS: Administration of pranlukast suppressed IAR by 80.5% (p < 0.0001) and LAR by 54.6% (p = 0.0391). Ozagrel significantly suppressed IAR by 39.5% (p = 0.0413), but the fall in FEV1 was >20% (21.56+/-4.173%). Seratrodast did not suppress IAR or LAR. Blood levels of chemical mediators did not correlate with the suppressive effects of the tested drugs. CONCLUSIONS: The LT receptor antagonist was considered to be the most effective. LT might play a more important role in the pathogenesis of asthma than TXA2. Our data showed that measurement of blood levels of chemical mediators is not useful in identifying the pathogenic mechanisms of asthma. 相似文献