全文获取类型
收费全文 | 935篇 |
免费 | 94篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 28篇 |
综合类 | 15篇 |
化学工业 | 230篇 |
金属工艺 | 41篇 |
机械仪表 | 37篇 |
建筑科学 | 66篇 |
矿业工程 | 10篇 |
能源动力 | 41篇 |
轻工业 | 120篇 |
水利工程 | 17篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 92篇 |
一般工业技术 | 137篇 |
冶金工业 | 52篇 |
原子能技术 | 7篇 |
自动化技术 | 131篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 37篇 |
2020年 | 29篇 |
2019年 | 27篇 |
2018年 | 51篇 |
2017年 | 53篇 |
2016年 | 54篇 |
2015年 | 35篇 |
2014年 | 48篇 |
2013年 | 89篇 |
2012年 | 63篇 |
2011年 | 66篇 |
2010年 | 74篇 |
2009年 | 41篇 |
2008年 | 46篇 |
2007年 | 51篇 |
2006年 | 29篇 |
2005年 | 20篇 |
2004年 | 25篇 |
2003年 | 27篇 |
2002年 | 20篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 13篇 |
1997年 | 20篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1917年 | 1篇 |
1909年 | 1篇 |
1907年 | 1篇 |
排序方式: 共有1036条查询结果,搜索用时 828 毫秒
71.
Anna Gliszczyńska-Świgło Alina Kałużewicz Katarzyna Lemańska Mikołaj Knaflewski Bożena Tyrakowska 《Food chemistry》2007,100(1):241-245
The effect of solar radiation on the quercetin and kaempferol contents in the inflorescence of three broccoli cultivars (‘Lord’, ‘Marathon’ and ‘Fiesta’) was investigated from 1999 to 2001. Great differences in the contents of both flavonols, dependent on growing time and cultivar, were found. Quercetin and kaempferol contents varied from 14.3 to 81.0 mg kg−1 f.w. and from 35.9 to 213 mg kg−1 f.w., respectively. Inflorescences of the cultivar ‘Lord’ were characterised by the highest mean content of quercetin and those of cultivar ‘Fiesta’ of kaempferol. The contents of both flavonols were highly positively correlated with total solar radiation in the period from planting to the harvest of broccoli inflorescences. 相似文献
72.
I Durak O Kurtipek HS Oztürk M Birey T Güven M Kavutcu M Ka?maz B Dikmen M Yel O Canbolat 《Canadian Metallurgical Quarterly》1997,44(9):1014-1020
PURPOSE: To investigate the effects of halothane and halothane plus vitamin E treatment on myocardial free radical metabolism in guinea pigs. METHODS: Four groups of seven animals were studied: control, halothane, halothane plus vitamin E and vitamin E groups. In the halothane group, halothane 1.5% in oxygen was given for 90 min over three days. In the halothane plus vitamin E group, 300 mg.kg-1.day-1 vitamin E im was started three days before the first halothane treatment and continued for three days. Following sacrifice, the hearts were assayed for superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) and malondialdehyde (MDA) level was determined. Electron spin resonance (ESR) analysis and electron microscopy (EM) were also performed. RESULTS: In the halothane group, SOD activities and MDA concentrations were increased compared with control and GSH-Px and CAT activities were decreased. In the halothane plus vitamin E group, there were no differences in enzyme activity compared with halothane alone but the MDA level was decreased. In the vitamin E group, enzyme activities were increased compared with control. Mainly the CF3CHCl radical was identified by ESR analysis in heart tissues exposed to halothane and the concentration of this radical was reduced by vitamin E. Electron microscopy showed cytoplasmic vacuolisation and dilation in sarcoplasmic reticulum in the heart tissues exposed to halothane: both were prevented by vitamin E. CONCLUSION: Although halothane causes impairment in enzymatic antioxidant defence potential, due to lowered GSH-Px and CAT activity, and accelerates peroxidative reactions in the tissues affected, no subcellular damage occurred. Vitamin E may protect tissues against free radical attack by scavenging toxic free radicals formed in heart tissue during halothane anaesthesia. 相似文献
73.
BACKGROUND: Electrical conductivity, photoconductivity, voltage‐controlled negative resistance and thermal properties of copolymers of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid and maleic acid were investigated in order to obtain new organic semiconductors. RESULTS: The room temperature conductivity of three different copolymers was found to be in the range 1.28 × 10?8 ? 1.20 × 10?7 S cm?1. The dark‐ and photo‐current‐voltage characteristics indicate that the copolymers exhibit voltage‐controlled differential negative resistance behaviour. The electrical conductivity of the polymers increases by photo‐illumination, suggesting that the polymers exhibit photoconductivity. The width of the exponential tail in the forbidden band gap of the three polymers was determined via the transient photocurrent technique and E0 values were in the range 34.4–36.49 meV. CONCLUSION: The results suggest that the copolymers could be used as organic semiconductor materials. Copyright © 2007 Society of Chemical Industry 相似文献
74.
Ramazan Kahraman 《应用聚合物科学杂志》2005,98(3):1165-1171
Epoxies are the most common of high‐performance structural adhesives, especially in automotive and aircraft manufacturing. In a variety of industrial applications, epoxy adhesives are required to have enhanced thermal conductivity. The normal method of changing this property is to add to the epoxy a filler of higher conductivity than the continuous phase. Although the improvement in the thermal properties of adhesives by the addition of metal fillers is obvious, their influence on water sorption characteristics of adhesives is not clear. It was the objective of this study to shed light on these aspects, which are lacking in the literature. The emphasis was placed on determining the moisture sorption behavior of aluminum‐powder‐filled epoxy adhesives under complete immersion in distilled water and sea water. Moisture diffusion tests show that the addition of aluminum filler into epoxy decreases the total amount of water intake at saturation in both fluids. However, there appears to be no significant effect of the aluminum filler content on the moisture diffusivity in epoxy adhesive specimens in either distilled water or seawater. It has also been determined that the adhesives adsorb a larger amount of water upon exposure to distilled water than when exposed to seawater, whereas the moisture diffusion rate in the adhesive immersed in seawater is higher than that in distilled water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1165–1171, 2005 相似文献
75.
Ka Ho Ling Chun Wai Cheung Sau Wan Cheng Ling Cheng Song-Lin Li Peter D. Nichols Robert D. Ward Alastair Graham Paul Pui-Hay But 《Food chemistry》2008
The outbreak of keriorrhea caused by the wax ester-rich oilfish and escolar has become a frequent and worldwide concern. To help prevent such episodes, rapid detection of these fishes in the supply chain of the seafood industry and by food and health inspection agencies is essential. Through a combination of DNA, GC–MS and TLC analyses with reference to authentic samples, fish steaks of oilfish and escolar mislabeled as other species could be accurately identified. The TLC method developed is inexpensive and provides a reliable and importantly rapid identification within 30 min. 相似文献
76.
77.
Saricimen Huseyin Kahraman Ramazan Malaibari Zuhair Abdur Rauf Md. 《Protection of Metals and Physical Chemistry of Surfaces》2018,54(5):926-933
Protection of Metals and Physical Chemistry of Surfaces - The objective of this study was to characterize the surfaces of the steel products produced locally during their exposure to the industrial... 相似文献
78.
Respiratory bioaerosol deposition from a cough and recovery of viable viruses on nearby seats in a cabin environment 总被引:1,自引:0,他引:1
Cunteng Wang Jingcui Xu Sau Chung Fu Ka Chung Chan Christopher Y. H. Chao 《Indoor air》2021,31(6):1913-1925
Respiratory bioaerosol deposition in public transport cabins is critical for risk analysis and control of contact transmission. In this work, we built a two-row four-seat setup and an air duct system to simulate a cabin environment. A thermal manikin on the rear left-hand seat was taken as the infected passenger (IP) and “coughed” three times through a cough generator. The deposited viruses and droplets on nearby seats were measured by a cultivation method and microscope, respectively. The effects of seat backrest and overhead gasper jet were studied. Results showed that the number of deposited virus on the front seat was one order of magnitude higher than that on other seats which only contained droplets smaller than 10 µm in diameter. When the backrest was 15 cm higher than the cough, the deposited number of viruses was reduced to 5% of that with the backrest at the same height with the cough. The gasper jet above the IP with a velocity of 1.5 m/s can reduce the deposited viruses to 4% of that with gasper off. It indicates that both the gasper jet and backrest can work as mitigation measures to block the cough jet and protect the nearby passengers. 相似文献
79.
通过松香(RA)与富马酸(FA)高温下的Diels-Alder反应合成了富马海松酸(FPA),并利用碳谱(13CNMR)、电喷雾质谱(ESI-MS)、红外光谱(IR)对其进行了表征;通过FPA与丁二醇二缩水甘油醚(BDGE)、己二醇二缩水甘油醚(HDGE)的酯化反应合成了松香基环氧树脂预聚体(FB、FH),测试了预聚体与固化剂不同配比下固化物的漆膜性能;结果表明,当n(活性氢)/n(环氧基)在1.0、1.2时,漆膜的硬度大于HB,附着力小于2级,T-弯实验小于2 T,耐冲击强度大于9.8 J,耐化学性能良好。 相似文献
80.
目的探讨动力髋螺钉手术治疗股骨粗隆间骨折的临床效果。方法对我院95例股骨粗隆间骨折患者采用DHS治疗。结果本组患者手术时间90~240min,平均140min,出血量100~600mL,平均220mL。均获得随访,随访时间为6~40个月,平均12个月。93例骨折均愈合,2例延迟愈合,与过早负重有关,限制活动后骨折愈合。平均愈合时间为3个月。完全负重时间为5个月,无伤口感染、褥疮、无骨不愈合、髋内翻发生,无螺钉穿出股骨头、退出、钢板断裂及变形。本组优75例,良18例,差2例,优良率为97.9%。结论DHS是治疗股骨粗隆间骨折内固定器械中的首选,手术时间短,内固定牢靠,减少了卧床并发症及髋内翻发生,缩短了住院时间,疗效可靠,值得临床推广应用。 相似文献