全文获取类型
收费全文 | 506篇 |
免费 | 60篇 |
国内免费 | 39篇 |
专业分类
化学 | 418篇 |
晶体学 | 6篇 |
力学 | 5篇 |
综合类 | 2篇 |
数学 | 116篇 |
物理学 | 58篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 23篇 |
2021年 | 42篇 |
2020年 | 32篇 |
2019年 | 29篇 |
2018年 | 16篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 29篇 |
2013年 | 39篇 |
2012年 | 17篇 |
2011年 | 29篇 |
2010年 | 31篇 |
2009年 | 26篇 |
2008年 | 34篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有605条查询结果,搜索用时 109 毫秒
601.
602.
Ground rubber powder (GRP) with three different sizes was incorporated into nature rubber matrix with different loading. Cure characteristics, swelling behaviour, crosslink density, tensile fractured surface, and mechanical properties have been studied. Based on the cure characteristics, it is evident that the processability of the rubber compounds has not changed obviously with the different GRP loading. The introduction of GRP in virgin rubber leads to the increase in swelling degree and the decrease in crosslink density. Tensile strength, hardness and abrasion resistant deteriorate with the increase of GRP loading, but the tear resistance gets better. If the ground rubber particles are smaller, the properties are more similar to the virgin rubber. Because of the phase separation of the GRP and matrix, the properties get worse with the bigger ground rubber powder. 相似文献
603.
The hydrophobic nature of recycled rubber particles presently limits their use only in non-aqueous media. Recycled rubber particles were chemically modified by preparation of amphiphilic semi-interpenetrating polymer networks using poly(acrylic acid) as the hydrophilic polymer. The resulting composite particles are water dispersible and suitable for various aqueous media applications. 相似文献
604.
In situ ATR-FTIR Spectroscopy of Poly(ethylene terephthalate) Subjected to High-Temperature Methanol
Summary: In situ ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopy combined with a high-pressure cell has been applied to measure IR spectra of polymers subjected to superheated or near-critical methanol (100– 200 °C). Spectra of poly(ethylene terephthalate) (PET) have been measured under exposure to high temperature methanol using this ATR-FTIR approach to understand at a molecular level the recycling process of PET. The evolution of the structure and the morphology of the polymer has been studied during the methanolysis. The quantity of trans PET conformer is generally used as a tracer of the crystallinity of PET. During depolymerisation of PET the evolution of crystallinity and of trans conformer appears to be different. The dependence of the rate constant on reaction temperature was correlated by Arrhenius plot, which shows activation energy of 5.8 kJ/mol. 相似文献
605.
Xuan Sun Li Xu Huijiao Yan Peng Li Hidayat Hussain Jiguo Liu Jinjie Zhang Daijie Wang 《Journal of separation science》2023,46(19):2300238
Gynostemma pentaphyllum (Thunb.) Makino represents the popular health food and supplemental product with broad pharmacological activities. The highly polar glycosides, including flavonoids and saponins, are major effective active components that contain diverse sugar positions and quantities, which result in diverse chemical polarities, making it challenging to separate and isolate these components. The present work described the rapid and efficient linear gradient counter-current chromatography to preparatively separate glycosides from aboveground parts of G. pentaphyllum. Besides, the ethyl acetate and n-butanol binary mobile phases were achieved through adjusting associated proportions. Six glycosides, including quercetin-3-O-neohesperidoside ( 1 ), kaempferol-3-O-robinobioside ( 2 ), kaempferol-3-O-neohesperidoside ( 3 ), gypenoside LVI ( 4 ), ginsenoside Rb3 ( 5 ), and gypenoside XLVI ( 6 ), were isolated at the purities greater than 98%. Moreover, electrospray ionization mass spectrometry and nuclear magnetic resonance tandem mass spectrometry were conducted for structural identification. According to our findings, the established linear gradient counter-current chromatography was an efficient approach to separate the highly polar glycosides from aboveground parts of G. pentaphyllum. Our proposed strategy can be used to separate active compounds from other complex natural products. 相似文献