全文获取类型
收费全文 | 98篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 91篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 6篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1987年 | 2篇 |
1968年 | 3篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有111条查询结果,搜索用时 31 毫秒
71.
Synthesis,Aromaticity and Photophysical Behaviour of Ferrocene‐ and Ruthenocene‐Appended Semisynthetic Chlorin Derivatives
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Taru Nikkonen Dr. María Moreno Oliva Dr. Stefan Taubert Dr. Michele Melchionna Dr. Axel Kahnt Dr. Juho Helaja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12755-12768
Two novel synthetic strategies to covalently link a metallocene electron‐donor unit to a chlorin ring are presented. In one approach, pyropheophorbide a is readily converted into its 131‐ferrocenyl dehydro derivative by nucleophilic addition of the ferrocenyl anion to the 131‐carbonyl group. In another approach, the corresponding 131‐pentamethylruthenocenyl derivative is synthesised from 131‐fulvenylchlorin by a facile ligand exchange/deprotonation reaction with the [RuCp*(cod)Cl] (Cp*=pentamethylcyclopentadienyl; cod=1,5‐cyclooctadiene) complex. The resulting metallocene–chlorins exhibit reduced aromaticity, which was unequivocally supported by ring‐current calculations based on the gauge‐including magnetically induced current (GIMIC) method and by calculated nucleus‐independent chemical shift (NICS) values. The negative ring current in the isocyclic E ring suggests the antiaromatic character of this moiety and also clarifies the spontaneous reactivity of the complexes with oxygen. The oxidation products were isolated and their electrochemical and photophysical properties were studied. The ruthenocene derivatives turned out to be stable under light irradiation and showed photoinduced charge transfer with charge‐separation lifetimes of 152–1029 ps. 相似文献
72.
Wohlfarth A Toepfner N Hermanns-Clausen M Auwärter V 《Analytical and bioanalytical chemistry》2011,400(3):737-746
An LC-MS/MS method for the determination of the atypic neuroleptic clozapine and its two main metabolites norclozapine and
clozapine-N-oxide has been developed and validated for serum and urine. After addition of d4-clozapine as deuterated internal standard
a fast single-step liquid–liquid extraction under alkaline conditions and with ethyl acetate as organic solvent followed.
The analytes were chromatographically separated on a Synergi Polar RP column using gradient elution with 1 mM ammonium formate
and methanol. Data acquisition was performed on a QTrap 2000 tandem mass spectrometer in multiple reaction monitoring mode
with positive electrospray ionization. Two transitions were monitored for each analyte in order to fulfill the established
identification criteria. The validation included the determination of the limits of quantification (1.0 ng/mL for all analytes
in serum and 2.0 ng/mL for all analytes in urine), assessment of matrix effects (77% to 92% in serum, 21 to 78% in urine)
and the determination of extraction efficiencies (52% to 85% for serum, 59% to 88% for urine) and accuracy data. Imprecision
was <10%, only the quantification of norclozapine in urine yielded higher relative standard deviations (11.2% and 15.7%).
Bias values were below ±10%. Dilution of samples had no impact on the correctness for clozapine and norclozapine in both matrices
and for clozapine-N-oxide in serum. For quantification of clozapine-N-oxide in urine a calibration with diluted calibrators has to be used. Calibration curves were measured from the LOQ up to
2,000 ng/mL and proved to be linear over the whole range with regression coefficients higher than 0.98. The method was finally
applied to several clinical serum and urine samples and a cerebro-spinal fluid sample of an intoxicated 13-month-old girl. 相似文献
73.
Bjoern Moosmann Stefan Kneisel Ariane Wohlfarth Volker Brecht Volker Auwärter 《Analytical and bioanalytical chemistry》2013,405(12):3929-3935
In the age of the Internet, the variety of drugs offered online is constantly increasing, and new drugs emerge every month. One group of drugs showing such an enormous increase is that of synthetic cannabinoids. Since their first identification in ‘herbal mixtures’, new structural modifications continue to appear on the market. In order to keep up with this process, toxicological screening methods need to be up to date. This can become extremely difficult if no reference material is available. In this article, a fast and effective way to extract and purify synthetic cannabinoids from ‘herbal mixtures’ is presented. This method opens a new opportunity for a timely reaction by obtaining reference material straight out of the ‘herbal mixtures’ ordered via the Internet. Isolation was carried out on a flash chromatography system with gradient elution on a C18 column using methanol and 0.55 % formic acid as mobile phases. The obtained purity of all compounds exceeded 99 %. In addition to the isolation of single compounds, the method proved to be suitable for the separation of various synthetic cannabinoids in one mixture, including the diastereomers cis- and trans-CP-47,497-C8. This approach for obtaining pure standards of new drugs proved to be effective, inexpensive and much quicker than waiting for the substances to be commercially available as reference material. Figure
Flash chromatography method for the isolation of synthetic cannabinoids from ‘herbal mixtures’ to obtain pure reference standards. 相似文献
74.
Valérie Marvaud Juan M. Herrera Thomas Barilero Fabien Tuyeras Raquel Garde Ariane Scuiller Caroline Decroix Martine Cantuel Cédric Desplanches 《Monatshefte für Chemie / Chemical Monthly》2003,134(2):149-163
This paper points out some recent achievements in the chemistry and physics of high spin and anisotropic molecules based
on polycyanometalate complexes. Following a step by step synthetic strategy and using a localized electron orbital model,
isotropic high spin molecules were obtained with ground spin states ranging from S = 9/2 to 27/2. In the same way, anisotropic molecules with various nuclearities (bi, tri, tetra, hexa, and hepta-nuclear
complexes) have been synthesized. Mixing these two approaches, it has been possible to obtained anisotropic high spin molecules
that behave as single molecule magnets. The paper reviews some of the steps that lead to these findings and some of the prospects
opened in the field of single molecule magnets.
Corresponding author. E-mail: marvaud@ccr.jussieu.fr
Received July 19, 2002; accepted July 23, 2002 相似文献
75.
76.
Haas M Liu SX Kahnt A Leiggener C Guldi DM Hauser A Decurtins S 《The Journal of organic chemistry》2007,72(20):7533-7543
An unsymmetric, peripherally octasubstituted phthalocyanine (Pc) 1, which contains a combination of dipyrido[3,2-f:2',3'-h] quinoxaline and 3,5-di-tert-butylphenoxy substituents, has been obtained via a statistical condensation reaction of two corresponding phthalonitriles. Synthetic procedures for the selective metalation of the macrocyclic cavity and the periphery of 1 were developed, leading to the preparation of the key precursor metallophthalocyanines 3-5 in good yields. Two different strategies were applied to the synthesis of compact dyads MPc-Ru(II) 6-8 (M = Mg(II), Co(II), Zn(II)). Intramolecular electronic interactions in these dyads were studied by absorption, emission, and transient absorption spectroscopy. Upon photoexcitation, these dyads exhibit efficient intramolecular energy transfer from the Ru(II) chromophore to the MPc moiety. 相似文献
77.
Magnetic Control of Macromolecular Conformations in Supramolecular Anionic Polysaccharide–Iron Complexes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Larissa Schefer Ariane Bulant Christophe Zeder Dr. Abhijit Saha Prof. Dr. Raffaele Mezzenga 《Angewandte Chemie (International ed. in English)》2015,54(45):13289-13292
The anionic iota carrageenan polysaccharide is enriched with FeII and FeIII by ion exchange against FeSO4 and FeCl3. With divalent iron, portions of polymer chains undergo a secondary structure transition from random coils to single helices. The single‐chain macromolecular conformations can be manipulated by an external magnetic field: upon exposure to 1.1 T, the helical portions exhibit 1.5‐fold stiffening and 1.1‐fold stretching, whereas the coil conformations respond much less as a result of lower contents of condensed iron ions. Along with the coil–helix transition, the trivalent iron triggers the formation of superstructures. The applicability of iron‐enriched iota carrageenan as functional ingredient for food fortification is tested by free Fe2+ and Fe3+ contents, respectively, with the most promising iota‐FeIII yielding 53 % of bound iron, which is due to the superstructures, where the ferric ions are chelated by the supramolecularly self‐assembled polymer host. 相似文献
78.
LetC be a generically smooth, locally complete intersection curve defined over an algebraically closed fieldk of characteristicp≥0. LetG⊃ Aut
k
C be a finite group of automorphisms ofC. We develop a theory ofG-equivariant deformations of the Galois coverC→C/G. We give a thorough study of the local obstructions, those localized at singular or widely ramified points, to deform equivariantly
a cover. As an application, we discuss the case ofG-equivariant deformations of semistable curves.
相似文献
79.
Fuchs Beate Schiller Jürgen Süß Rosmarie Nimptsch Ariane Schürenberg Martin Suckau Detlev 《平面色谱法杂志一现代薄层色谱法》2009,22(1):35-42
JPC – Journal of Planar Chromatography – Modern TLC - Lipids are important natural products and essential in nutrition, cosmetic formulations, pharmaceuticals, etc. Lipids and,... 相似文献
80.
A general method for the synthesis of cage-carbon-functionalized cyclopentadienyl iron and cyclopentadienyl ruthenium tricarbadecaboranyl complexes has been developed that employs palladium-catalyzed Sonogashira, Heck, and Stille cross-coupling reactions directed at a cage-carbon haloaryl substituent. The key Li(+)[6-(p-XC(6)H(4))-nido-5,6,9-C(3)B(7)H(9)(-)] (X = I (1), Br (2), Cl (3)) haloaryl-tricarbadecaboranyl anionic ligands were synthesized in high yields via the reaction of the arachno-4,6-C(2)B(7)H(12)(-) anion with the corresponding p-halobenzonitriles (p-XC(6)H(4)-CN). The reactions of the salts 1-3 with (η(5)-C(5)H(5))Fe(CO)(2)I and (η(5)-C(5)H(5))Ru(CH(3)CN)(3)PF(6) were then used to produce the haloaryl complexes 1-(η(5)-C(5)H(5))-2-(p-XC(6)H(4))-closo-1,2,3,4-MC(3)B(7)H(9) (M = Fe, X = I (4), Br (5), Cl (6) and M = Ru, X = I (7), Br (8), Cl (9)). The sonication-promoted Sonogashira coupling reactions of 4 with terminal alkynes catalyzed by Pd(dppf)(2)Cl(2)/CuI yielded the alkynyl-linked derivatives 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhC≡C)- (10), (CH(3)CH(2)C(O)OCH(2)C≡C)- (11), ((η(5)-C(5)H(5))Fe(η(5)-C(5)H(4)C≡C))- (12)). Heck reactions of 4 with terminal alkenes catalyzed by Pd(OAc)(2) yielded the alkene-functionalized products 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhCH(2)CH═CH)- (13), (CH(3)(CH(2))(2)CH═CH)- (14)), while the Stille cross-coupling reactions of 4 with organotin compounds catalyzed by Pd(PPh(3))(2)Cl(2) afforded the complexes 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = Ph- (15), (CH(2)═CH)- (16), (CH(2)═CHCH(2))- (17)). These reactions thus provide facile and systematic access to a wide variety of new types of functionalized metallatricarbadecaboranyl complexes with substituents needed for potential metallocene-like biomedical and/or optoelectronic applications. 相似文献