全文获取类型
收费全文 | 914篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
化学 | 560篇 |
晶体学 | 4篇 |
力学 | 8篇 |
数学 | 145篇 |
物理学 | 219篇 |
出版年
2019年 | 11篇 |
2016年 | 22篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 27篇 |
2012年 | 33篇 |
2011年 | 35篇 |
2010年 | 28篇 |
2009年 | 24篇 |
2008年 | 37篇 |
2007年 | 35篇 |
2006年 | 37篇 |
2005年 | 44篇 |
2004年 | 33篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 17篇 |
2000年 | 9篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 19篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1967年 | 9篇 |
1966年 | 11篇 |
1938年 | 8篇 |
1935年 | 8篇 |
1875年 | 6篇 |
排序方式: 共有936条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Dr. Alexey S. Kiryutin Dr. Grit Sauer Dr. Daniel Tietze Martin Brodrecht Stephan Knecht Prof. Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Dr. Olga Avrutina Prof. Dr. Harald Kolmar Prof. Dr. Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(16):4025-4030
Two-dimensional NMR spectroscopy is one of the most important spectroscopic tools for the investigation of biological macromolecules. However, due to the low sensitivity of NMR spectroscopy, it takes usually from several minutes to many hours to record such spectra. Here, the possibility of detecting a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), a tetradecapeptide, by combining parahydrogen-induced polarization (PHIP) and ultrafast 2D NMR spectroscopy is shown. The PHIP activity of the inhibitor was achieved by labeling with O-propargyl-l -tyrosine. In 1D PHIP experiments a signal enhancement of a factor of approximately 1200 compared to standard NMR was found. This enhancement permits measurement of 2D NMR correlation spectra of low-concentrated SFTI-1 in less than 10 seconds, employing ultrafast single-scan 2D NMR detection. As experimental examples PHIP-assisted ultrafast single-scan TOCSY spectra of SFTI-1 are shown. 相似文献
46.
47.
48.
49.
50.
Sauer C Peters FT Staack RF Fritschi G Maurer HH 《Journal of mass spectrometry : JMS》2008,43(3):305-316
Studies are described on the metabolism and the toxicological detection of the phencyclidine-derived designer drugs N-(1-phenylcyclohexyl)-2-ethoxyethanamine (PCEEA) and N-(1-phenylcyclohexyl)-2-methoxyethanamine (PCMEA) in rat urine using gas chromatographic/mass spectrometric (GC/MS) techniques. The identified metabolites indicated that PCEEA and PCMEA were transformed to the same metabolites by N-dealkylation and O-dealkylation partially followed by oxidation of the resulting alcohol to the respective carboxylic acid and hydroxylation of the cyclohexyl ring at different positions and combinations of those. Finally, aromatic hydroxylation of the O-dealkylated metabolites was partially followed by hydroxylation of the cyclohexyl ring at different positions. All metabolites were partially excreted in conjugated form. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid-liquid extraction and microwave-assisted acetylation allowed the detection of an intake of a common drug users' dose both of PCEEA and PCMEA in rat urine. Assuming similar metabolism in humans, the STA should be suitable for proof of an intake of PCEEA and PCMEA in human urine, although their differentiation is not possible due to common metabolites. 相似文献