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排序方式: 共有404条查询结果,搜索用时 62 毫秒
271.
Grala A Ejfler J Jerzykiewicz LB Sobota P 《Dalton transactions (Cambridge, England : 2003)》2011,40(16):4042-4044
Alkyl-(S,S)-O-lactyllactate was prepared by chemoselective alcoholysis of lactide LA mediated by a magnesium catalyst. When ROH reacted with LA it yielded the ring-opened product R-(S,S)-O-lactyllactate exclusively, which remained intact as long as LA was present in the reaction mixture. Consumption of LA caused the reaction to proceed further giving R-(S)-lactate. 相似文献
272.
Jacek W. Morzycki Yliana Lpez Jolanta Poszyska Rosa Santillan Leszek Siergiejczyk Andrzej Sobkowiak 《Journal of Electroanalytical Chemistry》2007,610(2):205-210
Electrooxidation of tigogenin acetate afforded two products: 3β-acetoxy-16β-hydroxy-23,24-dinor-5α-cholanoic acid lactone (2) and 20-epitigogenin acetate (3). The structure of the latter compound was confirmed by an X-ray analysis. The tentative mechanism of reaction is proposed. 相似文献
273.
Fukuhara G Madenci S Polkowska J Bastkowski F Klärner FG Origane Y Kaneda M Mori T Wada T Inoue Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(9):2473-2479
Inherently chiral molecular clips (MCs), pseudoenantiomeric anti-1 and anti-2, as well as mesoid syn-3, were synthesized by diastereodifferentiating repetitive Diels-Alder reactions of the achiral bisdienophile 6 with chiral diene 5 generated in situ from (-)-menthyl 3,4-bis(dibromomethyl)benzoate 4. These MCs were successfully separated by chiral HPLC to give optically active anti-1 and anti-2 and almost optically inactive syn-3. The structures of anti-1, anti-2, and syn-3 were assigned by high-resolution NMR and the absolute configurations of anti-1 and anti-2 were determined by the exciton-chirality method. Optically active anti-2 can serve as a chiral host. It binds the HCl adduct of D-tryptophan methyl ester (D-TrpOMeHCl) 3.5 times stronger than the L-enantiomer (KD/KL=3.5). 相似文献
274.
Comparison of mouse plasma and brain tissue homogenate sample pretreatment methods prior to high‐performance liquid chromatography for a new 1,2,4‐triazole derivative with anticonvulsant activity 下载免费PDF全文
Jolanta Flieger Anna Kowalska Magdalena Pizoń Tomasz Plech Jarogniew Łuszczki 《Journal of separation science》2015,38(12):2149-2157
The focus of the study was to develop a bio‐analytical assay for a 1,2,4‐triazole derivative from plasma and brain tissue homogenate samples. The goal was to compare analytical techniques that facilitate high accuracy with simplified sample processing. In this study, commonly used standard protein precipitation and solid‐phase extraction methods utilizing C18 and cartridges of Hybrid technology were compared in terms of their ability for sample pretreatment and removal of biological matrices before high‐performance liquid chromatography quantification. Fast classical reversed‐phase chromatography on a C18 column paired with selective sample preparation using Hybrid solid‐phase extraction technology resulted in the most precise bio‐analytical determination of the hydrophobic 1,2,4‐triazole derivative in both biological samples studied. The obtained recovery values were above 95% with the coefficient of variation lower than 5%. 相似文献
275.
Krzysztof Komodziński Joanna Nowak Jolanta Lepczyńska Jan Milecki Bohdan Skalski 《Tetrahedron letters》2012,53(18):2316-2318
In aqueous solution, 6-azido-9-β-d-ribofuranosylpurine undergoes an efficient photoinduced purine ring expansion to give a novel imidazole-fused 1,3,5-triazepinone nucleoside and partial conversion into adenosine. The structure of the major product was established as 1-(β-d-ribofuranosyl)-4,6-dihydroimidazo[4,5-f][1,3,5]triazepin-5(1H)-one based on HRMS and NMR spectral data. 相似文献
276.
Jolanta Somiska 《K-Theory》2006,37(4):379-394
We show that a duality of the Hopf-cyclic homology and cohomology can be explained in terms of functors defined on a PROP for Hopf algebras. 相似文献
277.
Selection of a method for determination of activity of pectinolytic enzymes in berry fruit materials
The goal of the study was to find the most accurate and sensitive method for the determination of activity of pectinolytic
enzymes in complex mixtures obtained from fruit materials such as raw cloudberry and raspberry juices. Several assay methods
based on enzymatic reactions using viscometric, colourimetric, spectrophotometric, or pH-titration detection of the reaction
products were tested. Problems with the application of the selected methods, such as very low detection signal or very large
background signal, were observed. Among the tested methods, only a modified method based on the continuous recording of the
released carboxyl groups titration allowed to assay the activity of exogenous pectin methylesterase with a good linearity,
sensitivity, accuracy, and minimised the interference of other fruit components. 相似文献
278.
279.
Kamila Gajcy Jolanta Pękala Bożena Frąckowiak-Wojtasek Tadeusz Librowski Stanisław Lochyński 《Tetrahedron: Asymmetry》2010,21(16):2015-2020
Several novel cyclopropyl-rigidified γ- and δ-amino acids 3–4 have been prepared starting from monoterpene (+)-3-carene 2. These compounds are proposed as chiral analogues of γ-aminobutyric acid (GABA) 1 and are expected to be of interest as potential inhibitors of GABA receptors. 相似文献
280.
Jolanta Bucher Olivier Blacque Helmut W. Schmalle Heinz Berke 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(2):m87-m90
The title compounds, [Mo(C2H4NO2)2(NO)2], (I), and [Mo(C2H6NS)2(NO)2]·CH3CN, (II), contain distorted octahedral complexes in which the monoanionic N,S‐ and N,O‐bidentate ligands coordinate the molybdenum centres in different modes. The anionic O atoms of the glycinate ligands in (I) are coordinated trans to the nitrosyl ligands and the amine N atoms are located trans to each other, whereas in (II) the anionic S atoms are coordinated trans to each other and the amine N atoms are located trans to the nitrosyl ligands. Each compound has a single complete complex in the asymmetric unit on a general position. Six N—H...O contacts with N...O distances of less than 3.2 Å are observed in (I) between the amine groups and the nitrosyl and carboxylate O atoms. In the 1:1 solvate (II), the acetonitrile molecule forms short N—H...N contacts (N...N < 3.2 Å) between the solvent N atoms and one of the amine H atoms. In addition, three weak intermolecular N—H...S interactions (N...S > 3.3 Å) contribute to the stabilization of the structure of (II). 相似文献