全文获取类型
收费全文 | 56095篇 |
免费 | 5565篇 |
国内免费 | 2638篇 |
专业分类
电工技术 | 3526篇 |
技术理论 | 4篇 |
综合类 | 3638篇 |
化学工业 | 9182篇 |
金属工艺 | 3344篇 |
机械仪表 | 3826篇 |
建筑科学 | 4204篇 |
矿业工程 | 1748篇 |
能源动力 | 1777篇 |
轻工业 | 4032篇 |
水利工程 | 1163篇 |
石油天然气 | 2827篇 |
武器工业 | 553篇 |
无线电 | 6534篇 |
一般工业技术 | 6931篇 |
冶金工业 | 2642篇 |
原子能技术 | 810篇 |
自动化技术 | 7557篇 |
出版年
2024年 | 234篇 |
2023年 | 972篇 |
2022年 | 1743篇 |
2021年 | 2413篇 |
2020年 | 1793篇 |
2019年 | 1624篇 |
2018年 | 1837篇 |
2017年 | 1952篇 |
2016年 | 1847篇 |
2015年 | 2404篇 |
2014年 | 2991篇 |
2013年 | 3536篇 |
2012年 | 4063篇 |
2011年 | 4267篇 |
2010年 | 3689篇 |
2009年 | 3545篇 |
2008年 | 3344篇 |
2007年 | 3099篇 |
2006年 | 2911篇 |
2005年 | 2463篇 |
2004年 | 1863篇 |
2003年 | 1702篇 |
2002年 | 1759篇 |
2001年 | 1532篇 |
2000年 | 1229篇 |
1999年 | 1185篇 |
1998年 | 826篇 |
1997年 | 649篇 |
1996年 | 611篇 |
1995年 | 527篇 |
1994年 | 376篇 |
1993年 | 317篇 |
1992年 | 250篇 |
1991年 | 177篇 |
1990年 | 140篇 |
1989年 | 92篇 |
1988年 | 99篇 |
1987年 | 48篇 |
1986年 | 58篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1977年 | 8篇 |
1975年 | 5篇 |
1970年 | 6篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 366 毫秒
21.
22.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
23.
24.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
25.
Replacement of precious single metal catalysts with cost-effective, highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies. Organic metals were added to the feed as the oil-soluble precursors, and transformed into the catalytic active phases in this work. Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and transmission electron microscopy. The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both model compound and residue. Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system. Results showed that under the test conditions in the article, the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5. 相似文献
26.
Neural Computing and Applications - Traffic identification is currently an important challenge for network management and security. In this paper, we propose a novel application identification... 相似文献
27.
Yue Gao Miao-miao Zhang Xiao-peng Guo Wen-jian Li Dong Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(5):1290-1297
Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry 相似文献
28.
29.
30.
Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Da‐Hye Byun Hye‐Jeong Choi Hye‐Won Lee Hye‐Yeon Jeon Woo‐Jae Choung Jae‐Hoon Shim 《International Journal of Food Science & Technology》2015,50(6):1405-1412
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry. 相似文献