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101.
In Chul Lee Young Su Kang Hee Jang Moon Seok Pil Jang Jin Kon Kim Jaye Koo 《Journal of Mechanical Science and Technology》2010,24(7):1425-1431
Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation
apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143
m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry)
was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure,
penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into
cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow
field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center
area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation
effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of
the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under
modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent
which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the
same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume
flux distribution also increased. 相似文献
102.
Kyung-Hoon Bang Gui-Yung Chung Hyung-Hoi Koo 《Korean Journal of Chemical Engineering》2011,28(1):272-278
The preparation of C/C composites by the chemical vapor infiltration (CVI) of the pyrolysis carbon from propane was studied. Pyrolysis carbon was deposited at 30 torr and at temperatures between 1,173 and 1,233 K. The rate of carbon deposition increased slightly with time. The main gas products in the exit gas were methane, ethylene, and acetylene. The fraction of ethylene decreased and that of acetylene increased with the reaction temperature and the propane concentration. The produced propyl radicals reacted further at a high temperature and at a high propane concentration. These trends were similar to those of the reported data. Changes of the shapes of deposited carbon in the pores of preform were confirmed with SEM photos. The mathematical modeling of the system with the deposition rate constant from the reference estimated experimental data well. 相似文献
103.
In this paper, we present a 600‐V reverse conducting insulated gate bipolar transistor (RC‐IGBT) for soft and hard switching applications, such as general purpose inverters. The newly developed RC‐IGBT uses the deep reactive‐ion etching trench technology without the thin wafer process technology. Therefore, a freewheeling diode (FWD) is monolithically integrated in an IGBT chip. The proposed RC‐IGBT operates as an IGBT in forward conducting mode and as an FWD in reverse conducting mode. Also, to avoid the destructive failure of the gate oxide under the surge current and abnormal conditions, a protective Zener diode is successfully integrated in the gate electrode without compromising the operation performance of the IGBT. 相似文献
104.
Myung-Yeon Cho Sung-Joon Park So-Mang Kim Dong-Won Lee Hong-Ki Kim Sang-Mo Koo Kyoung-Sook Moon Jong-Min Oh 《Ceramics International》2018,44(14):16548-16555
Alumina and polytetrafluoroethylene (Al2O3-PTFE) composite films were fabricated by a simple aerosol deposition (AD) process, to confirm its applicability for various display screens requiring water resistant, anti-smudge and easy-to-clean properties. The surface morphologies, hydrophobic properties, and transparencies of the composite films with different PTFE contents, varying from 0.01 to 1?wt% were investigated. As a result, the composite films with over 0.3?wt% PTFE showed a sudden rise in surface roughness and low transmittance, despite having the highest contact angle of 128° at a PTFE content of 0.3?wt%. From the energy dispersive spectrometer analysis, the crash-cushioning effect of PTFE and agglomerated PTFE particles were determined to be major causes of surface roughness and opacity. In contrast, the transmittance showed a tendency to be enhanced, with an increasing PTFE content in the range of 0.01, 0.05, and 0.1?wt% PTFE, respectively. Especially, the film with 0.1?wt% of PTFE had contact angle of 111° and exhibited a high transmittance of over 75%, which was inferred to be an appropriate amount of PTFE, with a high elongation filling up the surface and the internal defects, leading to an enhancement of transparency. Consequently, these results implied that the AD-prepared Al2O3-PTFE composite coatings are promising candidates for various display applications. 相似文献
105.
Wireless Personal Communications - Cognitive radio networks (CRNs) have a shortcoming in that attackers can increase their ability to disturb secondary users (SUs). This paper focuses on jamming... 相似文献
106.
Onions with or without heating (100 °C, 30 min) were extracted with water or methanol, and antioxidant and antimicrobial activities of onion extracts were evaluated. Product characteristics of fresh pork patties containing various onion extracts were measured during refrigerated storage. Water extracts of onions showed higher extraction yield and iron chelating ability than methanol extracts (P < 0.05), whereas, the latter was more effective than the former in phenolic compounds and reducing power (P < 0.05). The addition of onion extracts [water extract from fresh onion (WEFO), methanol extract from heated onion (MEHO) and their combinations (WEFMEHO)] to pork patties decreased redness, increased yellowness, and inhibited lipid peroxidation (P < 0.05). One per cent of WEFMEHO in pork patties had antioxidant activities as effective as butylated hydroxyl toluene (BHT, 0.01%). Redness and yellowness decreased and increased with the addition of onion extract, respectively (P < 0.05). 相似文献
107.
108.
Jae‐Hoon Lee Woo‐Jin Nam Hee‐Sun Shin Min‐Koo Han Yong‐Min Ha Hong‐Seok Choi Chang‐Hwan Lee Soon Kwang Hong 《Journal of the Society for Information Display》2006,14(4):411-417
Abstract— A novel active‐matrix organic light‐emitting‐diode (AMOLED) display employing a new current‐mirror pixel circuit, which requires four‐poly‐Si TFTs and one‐capacitor and no additional signal lines, has been proposed and sucessfully fabricated. The experimental results show that a new current mirror can considerably compensate luminance non‐uniformity and scale down a data current more than a conventional current‐mirror circuit in order to reduce the pixel charging time and increase the minimum data current. Compared with a conventional two‐TFT pixel, the luminance non‐uniformity induced by the grain boundaries of poly‐Si TFTs can be decreased considerably from 41% to 9.1%. 相似文献
109.
Organs used for transplantation undergo varying degrees of cold ischemia and reperfusion injury after transplantation. In renal transplantation, prolonged cold ischemia is strongly associated with delayed graft function, an event that contributes to inferior graft survival. At present, the pathophysiological changes associated with ischemia/reperfusion injury in clinical renal transplantation are poorly understood. We have performed an immunohistochemical analysis of pre- and postreperfusion biopsies obtained from cadaver (n = 55) and living/related donor (LRD) (n = 11) renal allografts using antibodies to adhesion molecules and leukocyte markers to investigate the intragraft changes after cold preservation and reperfusion. Neutrophil infiltration and P-selectin expression were detected after reperfusion in 29 of 55 (53%) and 24 of 55 (44%) cadaver renal allografts, respectively. In marked contrast, neutrophil infiltration was not observed in LRD allografts, and only 1 of 11 (9%) had an increased level of P-selectin after reperfusion. Immunofluorescent double-staining demonstrated that P-selectin expression resulted from platelet deposition and not from endothelial activation. No statistically significant association was observed between neutrophil infiltration and P-selectin expression in the glomeruli or intertubular capillaries despite the large number of cadaver renal allografts with postreperfusion changes. Neutrophil infiltration into the glomeruli was significantly associated with long cold ischemia times and delayed graft function. Elevated serum creatinine levels at 3 and 6 months after transplantation were also associated with the presence of neutrophils and platelets after reperfusion. Our results suggest that graft function may be influenced by early inflammatory events after reperfusion, which can be targeted for future therapeutic intervention. 相似文献
110.
Lukasik J Bradley ML Scott TM Dea M Koo A Hsu WY Bartz JA Farrah SR 《Journal of food protection》2003,66(2):188-193
The efficacy levels of different physical and chemical washing treatments in the reduction of viral and bacterial pathogens from inoculated strawberries were evaluated. Escherichia coli O157:H7, Salmonella Montevideo, poliovirus 1, and the bacteriophages PRD1, phiX174, and MS2 were used as model and surrogate organisms. Chemicals readily available to producers and/or consumers were evaluated as antimicrobial additives for the production of washes. The gentle agitation of contaminated strawberries in water for 2 min led to reductions in microbial populations ranging from 41 to 79% and from 62 to 90% at water temperatures of 22 and 43 degrees C, respectively. Significant reductions (> 98%) in numbers of bacteria and viruses were obtained with sodium hypochlorite (50 to 300 ppm of free chlorine), Oxine or Carnebon (200 ppm of product generating "stabilized chlorine dioxide"), Tsunami (100 ppm of peroxyacetic acid), and Alcide (100 or 200 ppm of acidified sodium chlorite) washes. Overall, 200 ppm of acidified sodium chlorite produced the greatest reductions of microorganisms. Hydrogen peroxide (0.5%) was slightly less effective than free chlorine in a strawberry wash and caused slight fruit discoloration. Cetylpyridinium chloride (0.1%) was effective in the reduction of bacterial species, while trisodium phosphate (1%) was effective against viruses. The consumer-oriented produce wash Fit was very effective (> 99%) in reducing the numbers of bacteria but not in reducing the numbers of viruses. Another wash, Healthy Harvest, was significantly less effective than Fit in reducing bacterial pathogens but more effective for viruses. The performance of automatic dishwashing detergent was similar to that of Healthy Harvest and significantly better than that of liquid dishwashing detergent. Solutions containing table salt (2% NaCl) or vinegar (10%) reduced the numbers of bacteria by about 90%, whereas only the vinegar wash reduced the numbers of viruses significantly (ca. 95%). 相似文献