全文获取类型
收费全文 | 260044篇 |
免费 | 22816篇 |
国内免费 | 12069篇 |
专业分类
电工技术 | 16656篇 |
技术理论 | 15篇 |
综合类 | 17096篇 |
化学工业 | 41469篇 |
金属工艺 | 14375篇 |
机械仪表 | 16153篇 |
建筑科学 | 19878篇 |
矿业工程 | 7041篇 |
能源动力 | 7736篇 |
轻工业 | 18614篇 |
水利工程 | 4979篇 |
石油天然气 | 14021篇 |
武器工业 | 2052篇 |
无线电 | 32248篇 |
一般工业技术 | 31581篇 |
冶金工业 | 12648篇 |
原子能技术 | 2883篇 |
自动化技术 | 35484篇 |
出版年
2024年 | 954篇 |
2023年 | 4319篇 |
2022年 | 7981篇 |
2021年 | 11394篇 |
2020年 | 8361篇 |
2019年 | 6737篇 |
2018年 | 7609篇 |
2017年 | 8620篇 |
2016年 | 7706篇 |
2015年 | 10489篇 |
2014年 | 13277篇 |
2013年 | 16368篇 |
2012年 | 17846篇 |
2011年 | 19184篇 |
2010年 | 16506篇 |
2009年 | 15693篇 |
2008年 | 15161篇 |
2007年 | 14179篇 |
2006年 | 14132篇 |
2005年 | 11895篇 |
2004年 | 8006篇 |
2003年 | 6690篇 |
2002年 | 6253篇 |
2001年 | 5528篇 |
2000年 | 5353篇 |
1999年 | 5960篇 |
1998年 | 5139篇 |
1997年 | 4379篇 |
1996年 | 4052篇 |
1995年 | 3314篇 |
1994年 | 2633篇 |
1993年 | 1999篇 |
1992年 | 1604篇 |
1991年 | 1202篇 |
1990年 | 919篇 |
1989年 | 745篇 |
1988年 | 601篇 |
1987年 | 411篇 |
1986年 | 335篇 |
1985年 | 252篇 |
1984年 | 199篇 |
1983年 | 142篇 |
1982年 | 143篇 |
1981年 | 119篇 |
1980年 | 110篇 |
1979年 | 64篇 |
1978年 | 57篇 |
1977年 | 56篇 |
1976年 | 79篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
122.
123.
124.
Anxiang Su Gaoxing Ma Minhao Xie Yang Ji Xiangfei Li Liyan Zhao Qiuhui Hu 《International Journal of Food Science & Technology》2019,54(6):2277-2287
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota. 相似文献
125.
126.
127.
128.
129.
130.
Xiaopu Lyu Yunxi Huo Jin Yang Dawen Yao Kaimin Li Haoxian Lu Yangzong Zeren Hai Guo 《Indoor air》2021,31(5):1340-1352
Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C28-C34 even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality. 相似文献