全文获取类型
收费全文 | 668篇 |
免费 | 22篇 |
国内免费 | 3篇 |
专业分类
化学 | 538篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 63篇 |
物理学 | 87篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 8篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 36篇 |
2011年 | 45篇 |
2010年 | 31篇 |
2009年 | 24篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 43篇 |
2005年 | 33篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 25篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有693条查询结果,搜索用时 31 毫秒
151.
Tetracoordinated Mn(II) complexes providing different molecular structures were investigated using various spectroscopical procedures. Na(6)MnS(4) contains separate pseudotetrahedral Mn-S complex units, K(2)MnS(2) has chains of edge-shared tetrahedra, and Cs(2)Mn(3)S(4) crystallizes in corresponding layers. Also doped materials, i.e., Cs(2)(Mn(x)Zn(1-x))(3)S(4) with 0.0 < x < 1.0, are considered. Absorption spectra recorded from samples incorporated in polyethylene pellets and excitation spectra taken from pure materials at 15-20 K temperature are assigned on the basis of energy level calculations obtained from the angular overlap model. All compounds exhibit intensive emission in the red, some of them also in the yellow region, which both are investigated in the temperature range from 12.5 to 250 K, in some cases varying the excitation power and excitation wavelength. Decay measurements supply lifetimes and activation energies evaluated from Arrhenius plots. The results support an assignment of both types of emissions to MnS(4) complex entities for all compounds, the red emission from the lowest excited level (Kasha luminescence) and the yellow emission, observed for some of the compounds with increasing intensity at lower temperature, from higher electronic levels. 相似文献
152.
The oxidation of catechol by hydrogen peroxide, catalyzed by cobalt(II), is a highly sensitive and selective reaction. It makes it possible to analyze a small sample of urine (5.0 ml) for cobalt without the need for isolation of the analyte from the matrix. The sample is dried and dry-ashed according to a temperature programme, and the residue is dissolved in hydrochloric acid. After filtration of the solution, acetate buffer and sodium citrate are added and cobalt is determined catalytically in an aliquot of the solution, by the standard-addition method. 相似文献
153.
Summary On the basis of some theoretical considerations a new catalytic reaction is proposed for determination of silver-the oxidation of sulphanilic acid with persulphate. In the presence of the catalyst, silver(I), the formation of the coloured reaction product proceeds much faster, which permits the determination of 1 ppm of the catalyst. The influence of the temperature, the acidity and 17 other ions on the reaction rate was also studied.
Zusammenfassung Auf der Grundlage einiger theoretischer Überlegungen wurde eine neue katalytische Reaktion zur Silberbestimmung vorgeschlagen, nämlich die Oxydation der Sulfanilsäure mit Persulfat. In Gegenwart von Silber als Katalysator bildet sich das gefärbte Reaktionsprodukt viel schneller, so daß sich 1 ppm des Katalysators bestimmen läßt. Der Einfluß der Temperatur, der Acidität sowie die Wirkung von 17 anderen Ionen auf die Reaktion wurden ebenfalls untersucht.相似文献
154.
155.
A new, fast, solvent-free and efficient method is provided to prepare thioformamides by reacting isocyanides derivatives, carbon disulfide and benzylamine under microwave irradiation. 相似文献
156.
Dr. Ulrike Warzok Lisa K. Mahnke Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1405-1419
Polyoxometalates (POMs) are an intriguing class of compounds due to their tremendous structural variety and the wide spectrum of resulting properties, which make them interesting for applications in fields such as catalysis, material science or nanotechnology. Their ability to form large supramolecular architectures by self-assembly offers an entry to complex, functional systems. After an introduction into the structure and synthesis of POMs of the early transition metals, recently discovered water-soluble antimonato polyoxovanadates (Sb-POVs) and the investigation of their chemical reactivity are discussed. Electrospray ionization mass spectrometry (ESI-MS) is presented as an analytical technique suitable to investigate the structure of complex POM assemblies in solution and to probe the underlying reactivity and formation mechanisms. This Minireview highlights the first studies on the soluble Sb-POVs and how the knowledge of their reactivity obtained by ESI-MS has fostered the syntheses of numerous novel Sb-POV compounds. 相似文献
157.
158.
159.
160.
Miloš R. Filipović Dr. Alaric C. W. Koh Dr. Stéphane Arbault Dr. Vesna Niketić Dr. Andrea Debus Ulrike Schleicher Dr. Christian Bogdan Dr. Manon Guille Dr. Fréderic Lemaître Dr. Christian Amatore Dr. Ivana Ivanović‐Burmazović Dr. 《Angewandte Chemie (International ed. in English)》2010,49(25):4228-4232