全文获取类型
收费全文 | 1194篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
化学 | 986篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 102篇 |
物理学 | 141篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 19篇 |
2019年 | 13篇 |
2017年 | 5篇 |
2016年 | 30篇 |
2015年 | 10篇 |
2014年 | 26篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 44篇 |
2010年 | 28篇 |
2009年 | 22篇 |
2008年 | 56篇 |
2007年 | 40篇 |
2006年 | 44篇 |
2005年 | 45篇 |
2004年 | 58篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 13篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1972年 | 6篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 43篇 |
1967年 | 116篇 |
1966年 | 96篇 |
1965年 | 80篇 |
排序方式: 共有1233条查询结果,搜索用时 31 毫秒
91.
Burkhard Butschke Maria Schlangen Detlef Schröder Helmut Schwarz 《Helvetica chimica acta》2008,91(10):1902-1915
Mechanistic details for the formation of methane from the title compound as well as the combined elimination of (CH3)2S/CH4 are derived from various mass‐spectrometric experiments including deuterium‐labeling studies and DFT calculations. For the first process, i.e., methane formation, we have identified three competing pathways in which the intact, Pt‐bonded methyl group combines with a H‐atom that originates from a phenyl substituent (ca. 7%), the dimethyl sulfide ligand (ca. 41%), and a methyl group of the diazabutadiene backbone (ca. 52%). In contrast, in the combined (CH3)2S/CH4 elimination, the methane is specifically formed from the Pt‐bound CH3 group and a H‐atom provided by one of the phenyl groups (‘cyclometalation’). 相似文献
92.
Targeted analysis of protein citrullination using chemical modification and tandem mass spectrometry
Maria Stensland Anders Holm Andrea Kiehne Burkhard Fleckenstein 《Rapid communications in mass spectrometry : RCM》2009,23(17):2754-2762
Protein citrullination originates from enzymatic deimination of polypeptide‐bound arginine and is involved in various biological processes during health and disease. However, tools required for a detailed and targeted proteomic analysis of citrullinated proteins in situ, including their citrullination sites, are limited. A widely used technique for detection of citrullinated proteins relies on antibody staining after specific derivatization of citrulline residues by 2,3‐butanedione and antipyrine. We have recently reported on the details of this reaction. Here, we show that this chemical modification can be utilized to specifically detect and identify citrullinated peptides and their citrullination sites by liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. Using model compounds, we demonstrate that in collision‐induced dissociation (CID) a specific, modification‐derived fragment ion appears as the dominating signal at m/z 201.1 in the MS/MS spectra. When applying electron transfer dissociation (ETD), however, the chemical modification of citrulline remained intact and extensive sequence coverage allowed identification of peptides and their citrullination sites. Therefore, LC/MS/MS analysis with alternating CID and ETD has been performed, using CID for specific, signature ion‐based detection of derivatized citrullinated peptides and ETD for sequence determination. The usefulness of this targeted analysis was demonstrated by identifying citrullination sites in myelin basic protein deiminated in vitro. Combining antibody‐based enrichment of chemically modified citrulline‐containing peptides with specific mass spectrometric detection will increase the potential of such a targeted analysis of protein citrullination in the future. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
93.
94.
95.
We consider nonuniform black strings inside their event horizon. We present numerical evidence, that the singularity touches the horizon as the horizon topology changing transition is reached. 相似文献
96.
Tobias S. Hermann Thomas M. Klapötke Burkhard Krumm Jörg Stierstorfer 《无机化学与普通化学杂志》2017,643(2):149-151
Two highly energetic nitric acid esters were synthesized from the dimer of dihydroxyacetone. 1,3‐Dinitratoacetone ( 1 ) and its dimer 2,5‐bis(nitratomethyl‐2,5‐nitrato)‐1,4‐dioxane ( 2 ) were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, and elemental analysis. The thermal behavior was investigated with DTA measurements. Although showing the same atomic stoichiometry, dimer 2 shows significantly higher sensitivities measured by BAM methods (drophammer and friction tester). Due to the high oxygen content of 62.2 %, 1 and 2 were evaluated as potential high energy dense oxidizers. 相似文献
97.
98.
99.
Karl O. Christe David A. Dixon Mathias Hopfinger Thomas M. Klapötke Burkhard Krumm 《Journal of fluorine chemistry》2010,131(7):791-422
The [((C6H5)3P)2N]+, [(C6H5)4P]+ and [N(CH3)4]+ salts of SeF5−, SeF62− and SeOF3− and CsSeO2F were prepared and characterized. Crystal structures were obtained for [((C6H5)3P)2N][SeF5] and [((C6H5)3P)2N][SeOF3] CH2Cl2. In contrast to oxygen-bridged dimeric TeOF3−, the SeOF3− anion in [((C6H5)3P)2N][SeOF3] CH2Cl2 is monomeric and represents the first experimentally well determined molecular structure of a monomeric trifluoro-chalcogenite anion. Similarly, [((C6H5)3P)2N][SeF5] represents the first example of a structure containing a well-isolated undistorted SeF5− anion. The NMR and the vibrational spectra and their assignments were re-examined and corrected by comparison with high-level theoretical calculations. Whereas the previously published normal coordinate analysis of SeF5− is correct, that for SeOF3− needs major revision. 相似文献