全文获取类型
收费全文 | 1787篇 |
免费 | 186篇 |
国内免费 | 50篇 |
专业分类
化学 | 1594篇 |
晶体学 | 39篇 |
力学 | 22篇 |
综合类 | 4篇 |
数学 | 54篇 |
物理学 | 310篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 58篇 |
2019年 | 53篇 |
2018年 | 59篇 |
2017年 | 38篇 |
2016年 | 92篇 |
2015年 | 67篇 |
2014年 | 79篇 |
2013年 | 148篇 |
2012年 | 68篇 |
2011年 | 81篇 |
2010年 | 81篇 |
2009年 | 79篇 |
2008年 | 63篇 |
2007年 | 70篇 |
2006年 | 67篇 |
2005年 | 79篇 |
2004年 | 78篇 |
2003年 | 58篇 |
2002年 | 42篇 |
2001年 | 36篇 |
2000年 | 54篇 |
1999年 | 40篇 |
1998年 | 25篇 |
1997年 | 40篇 |
1996年 | 34篇 |
1995年 | 37篇 |
1994年 | 21篇 |
1993年 | 27篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 12篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2023条查询结果,搜索用时 15 毫秒
991.
Summary Three columns, mono-ol, butylphenyl and perfluorinated synthesized through the reaction of an olefin with a silica hydride intermediate, are evaluated for the separation of various model compounds. Two of the columns, mono-ol and perfluorinated, can operate in both the normal phase and reversed phase modes. Some effects of the hydride surface are detected, particularly for the perfluorinated phase. A four-component steroid mixture is tested on both the mono-ol and perfluorinated phases in the normal mode. 相似文献
992.
Flumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β-cyclodextrin dissolved in OV-1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investigated. 相似文献
993.
994.
F. Ammar-Khodja S. Guermouche M. H. Guermouche E. Rogalska M. Rogalski P. Judeinstein J. P. Bayle 《Chromatographia》2003,57(3-4):249-253
Summary The thermodynamics of four new liquid crystals were investigated in order to understand their selectivity as stationary phases
in gas chromatography. In this case study, liquid crystals with a benzoyloxy azobenzene mesogenic core substituted with heptyloxy
(C7) and/or dioxyethylene ether (DOE) groups, were used. The chromatographic separations of linalool and citronellal, and
of xylene, tetraethylbenzene and cresol isomers, which were achieved with the liquid crystal stationary phases, have been
related to the dissolution thermodynamics of the solutes. The results gave us an insight into the mechanism of the molecular
recognition involved in the separation processes. 相似文献
995.
996.
3种苄基取代的β—环糊精作为气相色谱固定相的研究 总被引:3,自引:0,他引:3
对3种苄基化β-环糊精固定相进行了研究,考察了它们的色谱性能及对各种位置异构体的分离,研究了柱温对保留行为的影响,并讨论了环糊精保留的机理。 相似文献
997.
998.
Steurer W 《Angewandte Chemie (International ed. in English)》2011,50(46):10775-10778
999.
Separation of veterinary drug alaptide ((S)-8-methyl-6,9-diazaspiro(4,5)decane-7,10-dione) from a chiral impurity (R-enantiomer) was developed. Five chiral columns (three amylose and two cellulose type) were evaluated in a reversed-phase system. Three of them offered satisfactory enantiomeric resolution. Finally, three methods were validated and proved to be applicable for the determination of a chiral impurity content below 0.1% (method A: 3-AmyCoat column, tris-[3,5-dimethylphenyl]carbamoyl amylose; mobile phase: water/methanol/propan-2-ol/butan-2-ol=75:20:3.5:1.5 v/v, flow rate: 0.40 mL/min; column temperature: 30 °C; method B: Chiralpak AS-3R, tris-[1-phenylethyl]carbamoyl amylose; water/acetonitrile=80:20 v/v, 0.40 mL/min; 40 °C; method C: Chiralcel OZ-3R, tris-[3-chloro-4-methylphenyl] carbamoyl cellulose; water/acetonitrile=80:20 v/v, 0.40 mL/min; 40 °C). Some decrease in efficiency with repeated sample injections was observed for the 3-AmyCoat column. The resistance to mass transfer in the stationary phase increased probably due to the change in chiral selector conformation. This effect was considerably suppressed by propan-2-ol or to a greater extent by butan-2-ol added to a mobile phase. Simple regeneration was also suggested to recover efficiency of the column. 相似文献
1000.
Buszewski B Jaćkowska M Bocian S Kosobucki P Gawdzik B 《Journal of separation science》2011,34(6):601-608
Synthesis and properties of the multilayered stationary phases, which contain quaternary amine functional groups for the analysis of anions by ion chromatography, are described. The bonded phases were characterized by elemental analysis, solid-state (13)C NMR spectroscopy and chromatographic methods. The surface of 1,4-di(2-hydroxy-3-methacryloyloxypropoxy)phenol (solid support) was coated with polymeric layers formed by condensation polymerization of primary amine with diepoxide. Each layer of the anion exchange stationary phase consists of copolymer of methylamine (MA) and 1,4-butanedioldiglycidyl ether (BDDE). A series of stationary phases with different numbers of polymerized layers were tested. The separation of an inorganic anions sample (F(-), Cl(-), NO(2)(-), Br(-), NO(3)(-), additionally HPO(4)(2-) and SO(4)(2-)) was performed. In the measurement, a hydroxide, carbonate, bicarbonate and their mixture were used as mobile phases. 相似文献