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51.
Support vector machine based decision for mechanical fault condition monitoring in induction motor using an advanced Hilbert-Park transform 总被引:1,自引:0,他引:1
In this work we suggest an original fault signature based on an improved combination of Hilbert and Park transforms. Starting from this combination we can create two fault signatures: Hilbert modulus current space vector (HMCSV) and Hilbert phase current space vector (HPCSV). These two fault signatures are subsequently analysed using the classical fast Fourier transform (FFT). The effects of mechanical faults on the HMCSV and HPCSV spectrums are described, and the related frequencies are determined. The magnitudes of spectral components, relative to the studied faults (air-gap eccentricity and outer raceway ball bearing defect), are extracted in order to develop the input vector necessary for learning and testing the support vector machine with an aim of classifying automatically the various states of the induction motor. 相似文献
52.
Trir H. Radjehi L. Sengouga N. Tibermacine T. Arab L. Filali W. Abdelkader D. Attaf N. 《Semiconductors》2020,54(5):534-542
Semiconductors - This paper presents the Ultrasonic Spray Pyrolysis system fabrication of gallium-doped zinc oxide (ZnO:Ga)|cuprous oxide (Cu2O) thin film hetero-junction. The deposition parameters... 相似文献
53.
Abdelkader Nabili Arbi Fattoum Marie-Christine Brochier-Salon Julien Bras Elimame Elaloui 《Iranian Polymer Journal》2017,26(2):137-147
Cellulose triacetate (CTA) has successfully been synthesized from microfibrillated date seeds cellulose. The cellulosic material under study constituted 84.9% amorphous phase with a degree of polymerization of 950. Acetylation was conducted at 50 °C under optimized heterogeneous conditions by acetic anhydride as acetyl donor, acetic acid as solvent and sulfuric acid as catalyst. In this process, cellulose was acetylated without dissolving the material throughout. The acetylated cellulose chains on the surface were dissolved gradually in acetic acid, which created new accessible zones. The yield of cellulose triacetate was studied varying acetic acid, acetic anhydride and catalyst concentrations, as well as reaction times. The ratio between the intensity of the acetyl C=O stretching band at around 1740 cm?1 and the intensity of C–O stretching vibration of the cellulose backbone at 1020–1040 cm?1 was used to optimize the reaction time. The optimal reaction conditions of 8% concentration of sulfuric acid, acetic anhydride/cellulose weight ratio of 3:1, acetic acid/cellulose weight ratio of 7:1, reaction time of 3 h and reaction temperature of 50 °C have given highest yield of cellulose triacetate, of about 79%. The obtained date seeds-based cellulose triacetate was characterized thoroughly by Fourier transform infrared (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized product was identified as cellulose triacetate-I (CTA-I) characterized by a melting temperature of 217 °C and a decomposition temperature of 372 °C. These results demonstrated that date seeds can be used as potential source of microfibrillated cellulose which can be easily functionalized. 相似文献
54.
Yanagitani T Mishima N Matsukawa M Watanabe Y 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(4):701-704
The (1120) textured polycrystalline ZnO films with a high shear mode electromechanical coupling coefficient k15 are obtained by sputter deposition. An over-moded resonator, a layered structure of metal electrode film/(1120) textured ZnO piezoelectric film/metal electrode film/silica glass substrate was used to characterize k15 by a resonant spectrum method. The (1120) textured ZnO piezoelectric films with excellent crystallite c-axis alignment showed an electromechanical coupling coefficient k15 of 0.24. This value was 92% of k15 value in single-crystal (k15 = 0.26). 相似文献
55.
Abdelkader Mojtabi D. Andrew S. Rees 《International Journal of Heat and Mass Transfer》2011,54(1-3):293-301
We present an analytical and numerical stability analysis of the onset of natural convection in a horizontal fluid-saturated porous cavity. The cavity is bounded by thin horizontal plates with uniform thickness whose outer surfaces are subject to a constant heat flux. The main aim is to determine the effect of the presence of the bounding plates on the onset of convection. The onset criterion is found to be sensitively dependent on the relative thickness of the plates and the porous layer, δ, and their relative conductivities, d. For the long wavelength mode it is precisely Rac = 12(1 + 2δd). 相似文献
56.
On the evaluation of wind loads for wind turbines' foundation design: Experimental and numerical investigations 下载免费PDF全文
A. Abdelkader A. M. Aly M. Rezaee G. T. Bitsuamlak M. H. El Naggar 《The Structural Design of Tall and Special Buildings》2017,26(9)
In the past two decades, wind farms have been enjoying renewed interest as means for clean and renewable energy production. Larger and taller wind turbines are used for harvesting wind energy. In this paper, a boundary‐layer wind tunnel experiment was carried out on a model of the 5‐MW National Renewable Energy Laboratory (NREL) wind turbine, to evaluate overall wind‐induced base loadings in a parked condition. While mean and background base loadings were measured experimentally, a posttest dynamic analysis framework is developed to assess inertial loads analytically. The analytical analysis is carried out under both rigid and flexible tower‐foundation assumptions. Whenever applicable, the wind tunnel measurements are compared with NREL results, which were obtained by using the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) software. The comparison shows a good agreement between the proposed approach and the available FAST results. In addition, the study indicates that the flexibility of the foundation may result in a reduced overall wind loads, due to base isolation effects. However, the assumption of a rigid foundation results in a slightly conservative base loads. This said, depending on the available foundation system, the methodology followed in the current paper remains in force and the base stiffness can be updated to permit the estimation of actual foundation loadings. 相似文献
57.
Mami Yamaguchi Sri Ayu Anggraini Yuki Fujio Tomoaki Sato Michael Breedon Norio Miura 《International Journal of Hydrogen Energy》2013
A highly selective hydrogen (H2) sensor has been successfully developed by using an yttria-stabilized zirconia (YSZ)-based mixed-potential-type sensor utilizing SnO2 (+30 wt.% YSZ) sensing electrode (SE) with an intermediate Al2O3 barrier layer which was coated with a catalyst layer of Cr2O3. The sensor utilizing SnO2 (+30 wt.% YSZ)-SE was found to be capable of detecting H2 and propene (C3H6) sensitively at 550 °C. In order to enhance the selectivity towards H2, a selective C3H6 oxidation catalyst was employed to minimize unwanted responses caused by interfering gases. Among the examined metal oxides, Cr2O3 facilitated the selective oxidation of C3H6. However, the addition or lamination of Cr2O3 to SnO2 (+30 wt.% YSZ)-SE was found to diminish the sensing responses to all examined gases. Therefore, an intermediate layer of Al2O3 was sandwiched between the SE layer and the catalyst layer to prevent the penetration of Cr2O3 particles into the SE layer. The sensor using SnO2 (+30 wt.% YSZ)-SE coated with a catalyst layer of Cr2O3 as well as an intermediate layer of Al2O3 exhibited a sensitive response toward H2, with only minor responses toward other examined gases at 550 °C under humid conditions (21 vol.% O2 and 1.35 vol.% H2O in N2 balance). A linear relationship was observed between sensitivity and H2 concentration in the range of 20–800 ppm on a logarithmic scale. The results of sensing performance evaluation and polarization curve measurements indicate that the sensing mechanism is based on the mixed-potential model. 相似文献
58.
This paper investigates oil–water two‐phase flows in microchannels of 793 and 667 µm hydraulic diameters made of quartz and glass, respectively. By injecting one fluid at a constant flow rate and the second at variable flow rate, different flow patterns were identified and mapped and the corresponding two‐phase pressure drops were measured. Measurements of the pressure drops were interpreted using the homogeneous and Lockhart–Martinelli models developed for two‐phase flows in pipes. The results show similarity to both liquid–liquid flow in pipes and to gas–liquid flow in microchannels. We find a strong dependence of pressure drop on flow rates, microchannel material, and the first fluid injected into the microchannel. 相似文献
59.
Mori H Kanemura Y Onaya J Hara M Miyake J Yamasaki M Kariya Y 《Journal of Bioscience and Bioengineering》2005,100(1):54-61
Heparin binds various growth factors and activates them to interact with high-affinity cell surface receptors; a specific array of sulfate groups in the heparin backbone structure is very important for this interaction. In the present study, we evaluated the effects of two novel heparin derivatives, 6-O-desulfated heparin (6-DSH) and 2-O-desulfated heparin (2-DSH), on blood coagulation and the proliferation of human neural stem/progenitor cells (NSPCs). 6-DSH showed lower anticoagulant activity than intact heparin or 2-DSH, as measured by the activated partial thromboplastin time and thrombin time. In the presence of FGF-2, 6-DSH and 2-DSH promoted approximately the same rate of proliferation of human NSPCs, without noticeably changing the expression of nestin. The mitotic effects of 6-DSH and 2-DSH on human NSPCs were different from their effects on mouse hematopoietic stem cells and fibroblasts. These findings indicate that 6-DSH and 2-DSH have the same ability to promote the growth of human NSPCs as intact heparin. Our results suggest that these two novel heparin derivates, especially 6-DSH, could be used in clinical applications for ex vivo human NSPC culture, as a lower-risk growth co-adjuvant than intact heparin. 相似文献
60.
For an induction machine, we suggest a theoretical development of the mechanical unbalance effect on the analytical expressions of radial vibration and stator current. Related spectra are described and characteristic defect frequencies are determined. Moreover, the stray flux expressions are developed for both axial and radial sensor coil positions and a substitute diagnosis technique is proposed. In addition, the load torque effect on the detection efficiency of these diagnosis media is discussed and a comparative investigation is performed. The decisive factor of comparison is the fault sensitivity. Experimental results show that spectral analysis of the axial stray flux can be an alternative solution to cover effectiveness limitation of the traditional stator current technique and to substitute the classical vibration practice. 相似文献