全文获取类型
收费全文 | 111篇 |
免费 | 1篇 |
国内免费 | 15篇 |
专业分类
化学 | 106篇 |
晶体学 | 1篇 |
力学 | 1篇 |
物理学 | 19篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有127条查询结果,搜索用时 15 毫秒
51.
本文以氧化亚氮(N_2O)为反应气首次研究了一些有机硅立体异构体的负化学电离(NCI)质谱。反应离子(Reactant ions)和样品分子中硅及活性氢原子作用分别产生加合离子[M+O]~-和准分子离子[M-H]~-,它们的碎裂过程显示一定的立体专一性,为这些立体异构体的辨析提供了判据。 相似文献
52.
Dr. Xiangyu Guo Dr. Wenbo Cao Xiaomin Fan Dr. Zhiying Guo Donghui Zhang Haoyue Zhang Prof. Xiaoxiao Ma Prof. Jiahong Dong Prof. Yunfang Wang Prof. Wenpeng Zhang Prof. Zheng Ouyang 《Angewandte Chemie (International ed. in English)》2023,62(9):e202214804
Mass spectrometry imaging (MSI) of lipids in biological tissues is useful for correlating molecular distribution with pathological results, which could provide useful information for both biological research and disease diagnosis. It is well understood that the lipidome could not be clearly deciphered without tandem mass spectrometry analysis, but this is challenging to achieve in MSI due to the limitation in sample amount at each image spot. Here we develop a multiplexed MS2 imaging (MS2I) method that can provide MS2 images for 10 lipid species or more for each sampling spot, providing spatial structural lipidomic information. Coupling with on-tissue photochemical derivatization, imaging of 20 phospholipid C=C location isomers is also realized, showing enhanced molecular images with high definition in structure for mouse brain and human liver cancer tissue sections. Spatially mapped t-distributed stochastic neighbor embedding has also been adopted to visualize the tumor margin with enhancement by structural lipidomic information. 相似文献
53.
A series of 1,3-alternate conformation thiacalix[4]arenes containing different isomeric aminopyridyl pendent arms have been synthesized. It was found that their self-assembly behaviors and complexation properties strongly depended on the structures of aminopyridyl pendent arms. The crystal structures demonstrate that tetra(meta-aminopyridyl)-thiacalix[4]arene motif is capable of forming intramolecular hydrogen bondings between the sp2 nitrogen donors in the meta position of the aminopyridyl groups and the facing amide N-H of the adjacent aminopyridyl groups, and self-assembles via C-H?O weak hydrogen bondings and C-H?π interaction to generate a double stranded rectilineal networks. By contrast, in the case of tetra(para-aminopyridyl)-thiacalix[4]arene, the presence of para-aminopyridyl units enables the formation of N-H?N strong hydrogen bondings between the individual molecules leading to the solid-state structure with water-bridged double strands. Their complexation properties had been also studied by measurement of the stability constants for their complexation in a range of metal cations and investigation of their binding models via 1H NMR titration and ESI-MS experiments. It was found that the three ligands exhibited high and selective extractability toward Ag+, and their stoichiometry of ligand to Ag+ was 1:1, while the meta-aminopyridyl derivative showed the best extraction capacity and possessed the most efficient binding sites. 相似文献
54.
55.
Domenico Acierno Eugenio Amendola Cosimo Carfagna Luigi Nicolais Rossella Nobile 《Molecular Crystals and Liquid Crystals》2013,570(1):553-562
In this work the effect of the inclusion of low percentages of theliquid crystal polymer PET/PHBGO on the rheological and mechanical behaviour of Polycarbonate is described. 相似文献
56.
《Journal of Coordination Chemistry》2012,65(7):1056-1065
Four polyaniline hybrid materials doped with iron-substituted silicotungstate isomers α,?β i - K5?n H n [SiW11Fe(H2O)O39]?·?xH2O (βi?=?β1, β2, β3) were prepared. The materials were characterized by elemental analysis, IR spectra, UV-Vis spectra, scanning electron microscopy (SEM), TG-DTA and X-ray diffraction (XRD). The conductivity and fluorescence were determined and thermal stability was studied. The UV-Vis, IR and XRD results confirm the existence of Keggin anions. Thermal analysis indicates that SiW11Fe/PANI has better thermal stability. The images of scanning electron microscopy (SEM) show that the materials are microporous. The materials exhibit excellent proton conductivity of 8.5?×?10?2?S?cm?1 at room temperature (20°C). The spectral data indicate that polyaniline doped with α, βi-SiW11Fe have similar fluorescence, λem?=?418–470?nm, and emit blue light. 相似文献
57.
Malaria is one of the most widespread and deadly diseases on the planet. Every year, about 500 million new cases are diagnosed, and the annual death toll is about 3 million. Primaquine has strong antiparasitic effects against gametocytes and can therefore prevent the spread of the parasite from treated patients to mosquitoes. It is also used in radical cures and prevents relapse. Consequently, primaquine is an often-used drug. In this study the separation of unprocessed primaquine from the contaminant quinocide based on gas chromatography–mass spectrometry with supersonic molecular beam (SMB) is presented and 7.5 mg primaquine diphosphate tablets were analyzed. We present a novel method for fast determination of quinocide which is an isomer of primaquine as the main contaminant in unprocessed primaquine and in its medical form as tablets by gas chromatography–mass spectrometry with SMB (also named supersonic GC–MS). Supersonic GC–MS provides enhanced molecular ion without any ion source related peak tailing plus extended range of compounds amenable for GC–MS analysis. In addition, major isomer mass spectral effects were revealed in the mass spectra of primaquine and quinocide which facilitated the unambiguous identification of quinocide in primaquine tablets. Fast GC–MS analysis is demonstrated with less then 2 min elution time of the drug and its main contaminants. 相似文献
58.
SUN Ming-qian LU Jian-qiu ZHANG Hong-gui ZHANG Qun-shu XIAO Nan XI Rui-yun 《高等学校化学研究》2010,26(1):27-32
Based on the LC-ESI/MSn technique, the four pairs of isomers of psoralen and isopsoralen, imperatorin and isoimperatorin, neohesperidin and hesperidin, naringin and narirutin were distinguished mainly by comparison of the relative abundances of their major fragment ions. Because of the effect of the hydrogen on the C8 of psoralen, the intensity of the fragment ion formed by the loss of CO2 was relatively increased. By comparing the abundance of the product ions formed by the loss of CO and 2CO, the isomers ... 相似文献
59.
NOESY在立体化学研究中的某些应用 总被引:1,自引:0,他引:1
应用二维NOESY技术,对同分异构体1-4、顺反异构体5、6及两个环丙烷衍生物7、8在溶液中的构型、构象等立体化学问题进行了研究,并对化合物5-8进行了计算机分子模拟,取得与NOESY一致的结果. 相似文献
60.
Rosana Cassia de Souza Schneider Vanessa Zanon Baldissarelli Márcia Martinelli Elina Bastos Caramão 《Analytica chimica acta》2004,505(2):223-226
Optimization of the analytical conditions for determination of the partially hydrogenated products of castor oil obtained by catalytic hydrogen transfer, using Pd/C, with limonene as hydrogen source, was carried out in this work. The study involved the use of three capillary columns: SPB-1, HP-5 and HP-20 M. The best resolution for the oleic acids isomers, C18:1, was obtained with HP-20 M column while, the best resolution, identification and quantification for the products containing OH and CO were obtained with a HP-5 column after the silylation of the methyl esters. 相似文献