全文获取类型
收费全文 | 14733篇 |
免费 | 2702篇 |
国内免费 | 2025篇 |
专业分类
化学 | 11776篇 |
晶体学 | 157篇 |
力学 | 764篇 |
综合类 | 164篇 |
数学 | 1619篇 |
物理学 | 4980篇 |
出版年
2024年 | 48篇 |
2023年 | 313篇 |
2022年 | 504篇 |
2021年 | 525篇 |
2020年 | 676篇 |
2019年 | 748篇 |
2018年 | 544篇 |
2017年 | 446篇 |
2016年 | 788篇 |
2015年 | 813篇 |
2014年 | 894篇 |
2013年 | 1072篇 |
2012年 | 1338篇 |
2011年 | 1289篇 |
2010年 | 934篇 |
2009年 | 859篇 |
2008年 | 966篇 |
2007年 | 863篇 |
2006年 | 740篇 |
2005年 | 678篇 |
2004年 | 587篇 |
2003年 | 580篇 |
2002年 | 691篇 |
2001年 | 623篇 |
2000年 | 385篇 |
1999年 | 332篇 |
1998年 | 195篇 |
1997年 | 170篇 |
1996年 | 141篇 |
1995年 | 129篇 |
1994年 | 84篇 |
1993年 | 73篇 |
1992年 | 84篇 |
1991年 | 89篇 |
1990年 | 76篇 |
1989年 | 41篇 |
1988年 | 35篇 |
1987年 | 21篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1959年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Preparation and characterization of nitrogen-doped TiO2 photocatalyst in different acid environments
Ye Cong Ling Xiao Jinlong Zhang Feng Chen Masakazu Anpo 《Research on Chemical Intermediates》2006,32(8):717-724
Nitrogen-doped TiO2 powders were successfully prepared by a wet method, i.e., a micro-emulsion-hydrothermal method, in different acid environments.
Several characterization techniques, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse
reflectance spectra, were combined to determine the crystal phase, concentration and chemical states of the nitrogen doped
in TiO2. The high photocatalytic activity of the nitrogen-doped TiO2 was evaluated through the decomposition of rhodanmine B under visible light irradiation. It was suggested that the doped
nitrogen formed oxynitride (NO) and produced impurity states at higher above the valence band of TiO2. Therefore, the nitrogen doping could enhance the response of photocatalyst to the visible light and improve the photocatalytic
activity because of the narrowing of band gap of TiO2. 相似文献
93.
Separation of salidroside from Rhodiola crenulata by high-speed counter-current chromatography 总被引:3,自引:0,他引:3
High-speed counter-current chromatography (HSCCC) was used to purify salidroside from an extract of Rhodiola crenulata with two steps using a two-phase solvent system composed of ethyl acetate-n-butanol-water (1:4:5, v/v) in the first run and chloroform-methanol-isopropanol-water (5:6:1:4) in the second run. The method yielded 21.9 mg of salidroside from 1.216 g of the crude sample at 98% purity determined by HPLC analyses. Identification was performed by 1H NMR, 13C NMR, and MS. 相似文献
94.
95.
96.
97.
In the degassing process of transformer oil with ultrasonic waves ,decompostition of the oil was observed.Light hydrocarbons,including methane,ethane,ethylene ,aceylene,propane etc,were found to be released continuously from the oil into headspace within a closed vial placed in an ultrasonic field ,The gases came from decomposition of hydrocarbon molecules under cavitation effect. 相似文献
98.
99.
100.
Two new compounds from Zingiber officinale 总被引:1,自引:0,他引:1
Yu Zhao Qiao Feng Tao Rong Ping Zhang Chang Xin Zhou Hui Dou Shu Yun Shi Ye Cheng Xiao Lian Li Sun Su Zeng Ke Xin Huang Xiao Dong Zhang Xiao Kun Li 《中国化学快报》2007,18(10):1247-1249
A new cyclic diarylheptanoid,1,5-epoxy-3-hydroxy-1-(3-methoxy-4,5-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptane (1),as well as a new monoterpene,10-O-β-D-glucopyranosyl-hydroxy cineole (2) were isolated from the rhizomes of Zingiber officinale. The structures of compounds 1 and 2 were established based on their spectral data.In addition,the antioxidant activities of these compounds were also measured. 相似文献