全文获取类型
收费全文 | 1528篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
化学 | 846篇 |
晶体学 | 18篇 |
力学 | 46篇 |
数学 | 255篇 |
物理学 | 384篇 |
出版年
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 22篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 54篇 |
2012年 | 50篇 |
2011年 | 52篇 |
2010年 | 32篇 |
2009年 | 32篇 |
2008年 | 64篇 |
2007年 | 59篇 |
2006年 | 71篇 |
2005年 | 60篇 |
2004年 | 60篇 |
2003年 | 40篇 |
2002年 | 37篇 |
2001年 | 37篇 |
2000年 | 36篇 |
1999年 | 20篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 34篇 |
1991年 | 26篇 |
1990年 | 28篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 19篇 |
1976年 | 24篇 |
1975年 | 19篇 |
1974年 | 15篇 |
1973年 | 10篇 |
1967年 | 9篇 |
排序方式: 共有1549条查询结果,搜索用时 0 毫秒
871.
L. Semichon M. Flanzy F. Ehrlich E. Schowalter J. Dubaqnié C. A. Grau G. Bonifazi J. Estalella Ch. Lagneau P. Balavoine A. Widmer Ph. Malvezin O. Reichard G. Filaudeau H. Boßelmann C. von der Heide W. Lohmann Duyk M. Klostermann K. Scholta A. Kickton R. Murdfield O. Korn und P. Berg 《Fresenius' Journal of Analytical Chemistry》1928,73(1-3):108-115
Ohne Zusammenfassung 相似文献
872.
Ohne Zusammenfassung 相似文献
873.
874.
875.
876.
877.
R. Berg 《Fresenius' Journal of Analytical Chemistry》1927,71(1-2):23-36
Ohne Zusammenfassung 相似文献
878.
J. R. Berg 《Journal of separation science》1989,12(3):133-137
A high temperature gas chromatograph has been developed which is capable of operating at column oven temperatures up to 500°C. In addition, the detector can operate at temperatures up to 500°C, and the injector up to 450°C. The injector on this instrument is a temperature programmable direct injector, designed specifically to introduce labile or high molecular weight samples into the GC without molecular weight discrimination. The design of this GC and injector will be described, and high temperature applications will be discussed. 相似文献
879.
van den Berg RJ Korevaar CG Overkleeft HS van der Marel GA van Boom JH 《The Journal of organic chemistry》2004,69(17):5699-5704
The synthesis of naturally occurring D-erythro-(2R,3S,4E)-sphingosine from commercially available D-ribo-(2S,3S,4R)-phytosphingosine is described. The key step in the reaction sequence comprises TMSI/DBN promoted regio- and stereoselective oxirane opening of intermediate 2-phenyl-4-(S)-[(1S,2S)-1,2-epoxyhexadecyl]-1,3-oxazoline followed by the in situ trans-elimination of 2-phenyl-4-(S)-[(1S,2R)-1,2-dideoxy-2-iodo-1-trimethylsilyloxyhexadecyl]-1,3-oxazoline. 相似文献
880.
van den Berg JD Vermist ND Carlyle L Holcapek M Boon JJ 《Journal of separation science》2004,27(3):181-199
Different oil processing methods were performed, which included washing with water and treatment with lead-based driers, with and without heating to different temperatures, giving a set of 7 oils to be investigated. The effects of the traditional processing methods of linseed oil on its triacylglycerol (TAG) composition were studied, using the following analytical methods: high performance size exclusion chromatography (HPSEC), Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (HPLC-APCI-MS), direct temperature resolved mass spectrometry (DTMS), matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), and electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). A decrease of the initial cis-double bonds and the formation of trans-double bonds upon heating of the oils was observed. Heating a lead and oil mixture to 150 degrees C, or heating the oil alone to 300 degrees C led to the highest degree of oxidation. A difference was observed for the oxidation patterns for oils with and without the addition of lead. Furthermore, levels of oxygen incorporation were higher when lead was added to the oil. High temperature treatment of the oils resulted in an increased average molecular weight. The changes in the initial conformation of the double bond systems observed with FTIR were supported by HPLC-APCI-MS measurements that showed the formation of a number of new isomeric TAGs in the heated oil compared to freshly pressed, untreated oil. Oligomerisation up to hexamers was observed with HPSEC, and MALDI-TOF-MS. The formation of oligomers up to trimers only, however, was observed with ESI-FTICR-MS. Incorporation of oxygen was mainly observed with MALDI-TOF-MS and ESI-FTICR-MS whereas with DTMS and FTIR hardly any evidence was found for this. 相似文献