全文获取类型
收费全文 | 42篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 17篇 |
晶体学 | 1篇 |
数学 | 11篇 |
物理学 | 16篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 1篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有45条查询结果,搜索用时 218 毫秒
1.
Vonderheide AP Meija J Tepperman K Puga A Pinhas AR States JC Caruso JA 《Journal of chromatography. A》2004,1024(1-2):129-137
High-performance chelation ion chromatography (HPCIC) was employed to retain cationic Cr(III) on an anion-exchange column and hence allow the separation of the two most prevalent forms of chromium, Cr(II) and Cr(VI). A mobile phase of nitric acid was utilized at pH = 1.5; additionally, 2,6-pyridinedicarboxylic acid was used at a concentration of 6 mM. Additives with different structural characteristics were used in an effort to elucidate retention mechanisms. Inductively-coupled plasma mass spectrometry was used for chromium detection. A collision cell was utilized to reduce chloride-based polyatomic ions that may interfere with the detection of Cr(III), and a detection limit study yielded levels in the low part-per-billion range. The newly developed method was applied to the chromatographic analysis of samples of an incubation medium containing Cr(VI) incubated with cell nuclei. 相似文献
2.
Matthew T. HancockAllan R. Pinhas 《Tetrahedron letters》2003,44(29):5457-5460
The conversion of an aziridine to the corresponding oxazolidinone using only carbon dioxide and a catalytic amount of lithium iodide is discussed. In all cases, either no reaction occurred or a high yield of product was obtained. HMPA has been added to the reaction mixture, as needed, to drastically improve the regioselectivity. Net retention of stereochemistry between the starting aziridine and the product oxazolidinone was observed. 相似文献
3.
E. Delée L. Le Garrec I. Jullien S. Béranger J. C. Pascal H. Pinhas 《Chromatographia》1987,24(1):357-359
Summary A routine chiral analysis has been developed to control the optical purity of chiral drugs and to monitor their asymmetric
synthesis. The recent advent of new chiral stationary phases for HPLC enabled us to achieve the direct resolution of chiral
drugs without any derivatization.
The factors affecting chiral resolution on a new alpha1-acid glycoprotein column (EnantioPac, LKB) were assessed with three beta-aminoalcohols. 相似文献
4.
We report the experimental realization of a new type of optical parametric oscillator in which oscillation is achieved by polarization rotation in a linear retarder, followed by nonlinear polarization mixing. The mixing is performed by a type II degenerate parametric downconversion in a periodically poled KTP crystal pumped by a 1064 nm pulsed Nd:YAG pump. A single, linearly polarized beam, precisely at the degenerate wavelength is generated. The output spectrum has a narrow linewidth (below the instrumentation bandwidth of 1 nm) and is highly stable with respect to variations in the crystal temperature. 相似文献
5.
AR Engel 《Contemporary Physics》2013,54(6):523-526
This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given. 相似文献
6.
7.
The coupling reaction of water-soluble alkyl nitriles using Fenton's reagent (Fe(II) and H2O2) is described. The best metal for the reaction is iron(II), and the greatest yields are obtained when the concentration of the metal is kept low. Hydrogen-atom abstraction is selective, preferentially producing the radical alpha to the nitrile. In order to increase the production of dinitrile, in situ reduction of iron(III) to iron(II), using a variety of reducing agents, was investigated. 相似文献
8.
James R. Hermanson Timothy M. Figley Anna L. Seibert Allan R. Pinhas 《Journal of organometallic chemistry》2008,693(11):2061-2064
The reactivity of a nucleophilic nickel acylate complex with a tungsten carbene complex, Fe(CO)5, Cr(CO)6, PPh3, and CO was investigated. With the tungsten carbene complex, a methyl transfer occurred. With the metal carbonyl complexes, the acylate group on the nickel and a carbonyl on the iron or chromium traded places. With the PPh3 and CO, the acylate anion was replaced by the phosphine or CO ligand. 相似文献
9.
In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•+), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•+, DPPH•, and FRAP activities (IC50: 0.05 ± 0.0001 mg/mL, IC50: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC50: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source. 相似文献
10.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献