全文获取类型
收费全文 | 195篇 |
免费 | 8篇 |
专业分类
化学 | 176篇 |
数学 | 23篇 |
物理学 | 4篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 6篇 |
2005年 | 16篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 2篇 |
1998年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1966年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有203条查询结果,搜索用时 15 毫秒
51.
Ern? Müller Rita Skoda-Földes Eszter Takács George Kokotos László Kollár 《Tetrahedron》2005,61(4):797-802
Amino acid methyl esters were used as amine nucleophiles in palladium catalysed aminocarbonylation of iodobenzene and iodoalkenes (1-iodo-cyclohexene and 17-iodo-androst-16-ene). 2-Oxo-carboxamide type derivatives can be isolated as a result of double CO insertion by using iodobenzene as a substrate at elevated carbon monoxide pressure. On the contrary, carboxamides of expected structure were obtained exclusively in excellent yields in the whole pressure range by using iodoalkenes. The aminocarbonylation of 17-iodo-androst-16-ene in [bmim][PF6] or [bmim][BF4] (where bmim=1-butyl-3-methyl-imidazolium cation) ionic liquids was also carried out and the ionic liquid-catalyst mixtures have been reused several times with only a small loss of activity. 相似文献
52.
JPC – Journal of Planar Chromatography – Modern TLC - A study has been conducted to investigate the metabolism of 14C-labeled denaverine in the rat. The metabolites were mainly excreted... 相似文献
53.
DDQ treatment of the Diels-Alder products 1 unexpectedly led to chloroderivatives 2. Chlorination did not occur during DDQ treatment of the fully aromatised compounds 3. These results point out that DDQ acted as an oxidant and source of chlorine. 相似文献
54.
Convergence chromatographic determination of camphor in the essential oil of Tanacetum parthenium L.
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Krisztina Végh Eszter Riethmüller Anita Tóth Ágnes Alberti Szabolcs Béni József Balla Ágnes Kéry 《Biomedical chromatography : BMC》2016,30(12):2031-2037
Feverfew (Tanacetum parthenium L., Asteraceae) is a perennial medicinal plant which has been used to alleviate the symptoms of migraine, headache and rheumatoid arthritis and possesses numerous pharmacological activities. An ultra‐high‐performance supercritical fluid chromatographic method (UHPSFC) was developed and validated in accordance with the International Conference on Harmonization guidelines in order to determine the camphor content of the volatile oil, which was accurate, precise, robust and selective. The method was validated for specificity, accuracy (100.2%), repeatability and intermediate precision, linearity (r2 > 0.999), limit of detection (2.055 μg/mL), limit of quantification (6.228 μg/mL) and robustness. The common range of accuracy and linearity was between 0.125 and 1.000 mg/mL. Steam distillation was carried out in order to study the essential oil yield of three different T. parthenium L. samples originating from Hungarian medicinal herb collections. The camphor content of the essential oils from the aerial parts of feverfew samples from different origin was compared. Although the composition of the essential oil is well reported, a validated quantitative UHPSFC method for the determination of the constituents is presented herein for the first time. 相似文献
55.
Comprehensive carbohydrate analysis of glycoproteins from human biological samples and biotherapeutics are important from diagnostic and therapeutic points of view. This review summarizes the current state-of-the-art liquid phase separation techniques used in N-glycosylation analysis. The different liquid chromatographic techniques and capillary electrophoresis methods are critically discussed in detail. Miniaturization of these methods is also important to increase throughput and decrease analysis time. The sample preparation and labeling methods for asparagine linked oligosaccharides are also addressed. 相似文献
56.
Orsolya Demeter Eszter A. Fodor Prof. Dr. Mihály Kállay Prof. Dr. Gábor Mező Dr. Krisztina Németh Dr. Pál T. Szabó Dr. Péter Kele 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(18):6382-6388
Herein, we give the very first example for the development of a fluorogenic molecular probe that combines the two‐point binding specificity of biarsenical‐based dyes with the robustness of bioorthogonal click‐chemistry. This proof‐of‐principle study reports on the synthesis and fluorogenic characterization of a new, double‐quenched, bis‐azide fluorogenic probe suitable for bioorthogonal two‐point tagging of small peptide tags by double strain‐promoted azide–alkyne cycloaddition. The presented probe exhibits remarkable increase in fluorescence intensity when reacted with bis‐cyclooctynylated peptide sequences, which could also serve as possible self‐labeling small peptide tag motifs. 相似文献
57.
Erika Bálint Eszter Fazekas Judit Takács Ádám Tajti Amadej Juranovič Marijan Kočevar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):48-50
Abstract Kabachnik-Fields reactions of a variety of amines, phospha-Michael additions to maleimide derivatives and alcoholysis of dialkyl phosphites were studied under microwave conditions. 相似文献
58.
The title compounds were synthesized by the microwave‐assisted, mostly solvent‐free bis Kabachnik–Fields condensation of β‐alanine and γ‐aminobutyric acid or their esters with formaldehyde and >P(O)H species, such as dialkyl phosphites and diphenylphosphine oxide. 相似文献
59.
Tams Firkala Emília Tlas Sndor Kristyn Gyrgy Szllsi Eszter Drotr Jnos Mink Judith Mihly 《Journal of Raman spectroscopy : JRS》2015,46(11):1102-1109
The strength and geometry of adsorption of substituted propenoic acids on silver surface were studied by means of surface enhanced Raman spectroscopy (SERS) using silver sol. Based on their SERS behavior, two classes of phenylpropenoic acids studied were distinguished. The first class of propenoic acids (atropic acid, (E)‐2,3‐diphenylpropenoic acid, (E)‐2‐(2‐methoxyphenyl)‐3‐phenylpropenoic acid, (E)‐2,3‐di‐(4‐methoxyphenyl)phenylpropenoic acid and (E)‐2‐(2‐methoxyphenyl)‐3‐(4‐fluorophenyl)propenoic acid) has shown strong charge transfer (CT) effect. We suggest bidentate carboxyl bonded species based on the SERS enhanced bands of νCOO− around 1394 cm−1 and νC―C of the ―C―COO− moiety at 951 cm−1. In these series the plane of the α‐phenyl group (γCH out‐of‐plane vibrations at 850–700 cm−1) is almost parallel to the silver surface, while the β‐phenyl group is in tilted position depending on the type and the position of substituent(s) showing strong SERS enhanced bands of νCC + βCH (in‐plane mode) at 1075 cm−1, νCC (ring breathing mode, in‐plane) at 1000 cm−1 and γCCC (out‐of‐plane mode) around 401 cm−1. The other class of propenoic acids (cinnamic acid, (E)‐2‐phenyl‐3‐(4‐methoxyphenyl)propenoic acid) has shown weak electromagnetic (EM) enhancement (CC bands is enhanced in cinnamic acid). In this case no significant carboxyl enhancement was observed, so we suggest that adsorbed species lie parallel to the surface. The two types of adsorption can be related to the dissociation ability of the carboxylic group. In the first case the carboxylic H dissociates, while in the second case it does not, as indicated also by the characteristic νCO band at 1686 cm−1 in the FT‐Raman spectra of methanolic solutions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
60.
Lanthanide(III) Complexes of Cyclen Triacetates and Triamides Bearing Tertiary Amide-Linked Antennae
Salauat R. Kiraev Emilie Mathieu Fiona Siemens Daniel Kovacs Ellen Demeyere K. Eszter Borbas 《Molecules (Basel, Switzerland)》2020,25(22)
The coordination compounds of the trivalent lanthanide ions (Ln(III)) have unique photophysical properties. Ln(III) excitation is usually performed through a light-harvesting antenna. To enable Ln(III)-based emitters to reach their full potential, an understanding of how complex structure affects sensitization and quenching processes is necessary. Here, the role of the linker between the antenna and the metal binding fragment was studied. Four macrocyclic ligands carrying coumarin 2 or 4-methoxymethylcarbostyril sensitizing antennae linked to an octadentate macrocyclic ligand binding site were synthesized. Complexation with Ln(III) (Ln = La, Sm, Eu, Gd, Tb, Yb and Lu) yielded species with overall −1, 0, or +2 and +3-charge. Paramagnetic 1H NMR spectroscopy indicated subtle differences between the coumarin- and carbostyril-carrying Eu(III) and Yb(III) complexes. Cyclic voltammetry showed that the effect of the linker on the Eu(III)/Eu(II) apparent reduction potential was dependent on the electronic properties of the N-substituent. The Eu(III), Tb(III) and Sm(III) complexes were all luminescent. Coumarin-sensitized complexes were poorly emissive; photoinduced electron transfer was not a major quenching pathway in these species. These results show that seemingly similar emitters can undergo very different photophysical processes, and highlight the crucial role the linker can play. 相似文献