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排序方式: 共有135条查询结果,搜索用时 312 毫秒
61.
Priv.‐Doz. Dr. Alban Kellerbauer 《Physik in unserer Zeit》2012,43(4):174-180
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Grégoire Petitjean Fabrice Aman-Pommier François Coudoré Najoua El Helali Alban Le Monnier 《Biomedical chromatography : BMC》2020,34(2):e4759
Temocillin is a β-lactamase-resistant penicillin used for the treatment of multiple drug-resistant Gram-negative bacteria. To maximize efficacy and avoid adverse effects, the dose regimen has to be quickly adjusted to the clinical situations. This necessitates the development of a rapid, reliable and accurate analytical method. Temocillin and the stable isotopically labeled internal standard ([13C6]-amoxicillin) were extracted from either serum or cerebrospinal fluid by a turbulent flow liquid chromatographic method and eluted onto an octadecyl-silica phase with polar endcapping. Mass spectrometry was conducted using an exact mass determination method by electrospray positive ionization high-resolution mass spectrometry. The LLOQ and ULOQ of the present method were determined to be 0.4 and 200 μg/ml for serum and cerebrospinal fluid samples, respectively. The total analysis time was <7 min. The recovery ranged from 87.7 to 120.8%. Intra- and inter-day precision and trueness were tested at four concentration levels: 0.4, 8, 40 and 160 μg/ml. Values were 6.33 ± 1.53, 8.8 ± 1.3, 8.8 ± 0.36 and 2.1 ± 0.76%, and 5.0 ± 0.54, 9.9 ± 1.0, 5.8 ± 1.6 and 0.1 ± 1.1%, for inter- and intra-day analysis, respectively. Temocillin was found to be stable under all relevant laboratory conditions. The method was cross-validated with a microbiological assay. This method is suitable for accurate measurement of temocillin concentration in small volumes of serum or cerebrospinal fluid. Thanks to the online extraction procedure, the overall analytical time is compatible with high-throughput analysis for clinical application. 相似文献
64.
Feroci M Orsini M Palombi L Sotgiu G Colapietro M Inesi A 《The Journal of organic chemistry》2004,69(2):487-494
The diastereoselective electrochemical carboxylation of chiral N-(2-bromoacyl)oxazolidin-2-ones has been studied. This reaction was carried out by cathodic reduction of the C-Br bond, in the presence of carbon dioxide, followed by treatment with diazomethane. The yields and the diastereomeric ratio of the two epimeric alkylmalonic acid derivatives are strongly affected by various factors: solvent-supporting electrolyte system, temperature, electrode material, electrolysis conditions, oxazolidinone moiety. The higher yields (88%) were obtained starting from N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one 1a, but with poor diastereoselectivity (61:39). The two epimers were easily separated by flash chromatography. The best results were achieved using a different chiral auxiliary: Oppolzer's camphor sultam. Starting from 1j a good yield in carboxylated product was obtained (80%) with excellent diastereoselectivity (98:2). These chiral alkylmalonic acid derivatives are valuable building blocks in the synthesis of molecules with biological activity and of chiral propane-1,3-diols derivatives. 相似文献
65.
Dr. Pedro N. Leão Hitomi Nakamura Margarida Costa Dr. Alban R. Pereira Prof. Rosário Martins Prof. Vitor Vasconcelos Prof. William H. Gerwick Prof. Emily P. Balskus 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(38):11215-11219
The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C‐glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural‐elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR‐forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation. 相似文献
66.
We addressed an unexplored application of the Suzuki-Miyaura protocol to the cross-coupling of 1,1-dichloro-1-alkenes with 9-alkyl-9-BBN. The use of bisphosphine ligands with a large P-Pd-P bite angle allowed us to synthesize Z-chlorinated internal alkenes in good yields resulting from a selective monocoupling process, a recurrent challenge with 1,1-dichloro-1-alkenes. Moreover, these monochlorinated olefins could be further transformed providing stereospecifically trisubstituted olefins. 相似文献
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In this work, a Control Volume Radial Basis Function technique (CV-RBF) is adapted to solve ground water flow in the saturated
zone of the semi-confined aquifer. The CV-RBF method differs from classical CV methods in the way that the flux at the cell
surfaces is computed. A local RBF interpolation of the field variable is performed at the centres of the cell being integrated
and its neighbours. This interpolation is then used to reconstruct the solution and its gradient in the integration points
which support the flux computation. In addition, it is required that such interpolation satisfies the governing equation in
a certain number of points placed around the cell centres. In this way, the local interpolations become equivalent to local
boundary-value problems. The CV-RBF method is combined with a local remeshing technique in order to track the phreatic surface,
where the gradients required to satisfy the kinematic condition are computed by the same local RBF interpolations used for
the flux computation. The proposed numerical approach is validated in a series of three-dimensional groundwater flow problems
where the operations of recharging and extracting water from a semi-confined aquifer are modelled. 相似文献
70.
J. Gaubicher F. Orsini T. Le Mercier S. Llorente A. Villesuzanne J. Angenault M. Quarton 《Journal of solid state chemistry》2000,150(2):250
Two new compounds of the AxMOXO4 family, β-LiVOAsO4 and β-VOAsO4, have been synthesized by solid state reaction and electrochemical lithium deintercalation from β-LiVOAsO4, respectively. Both compounds are isostructural and are built like other β-VOXO4 (X=S, P) by (VO5)∞ chains of distorted VO6 octahedra connected via corner-shared AsO4 tetrahedra. For β-LiVOAsO4 the additional Li+ ions occupy chains of edge-shared octahedra running perpendicularly to the (VO5)∞ chains. The one-dimensional antiferromagnetic behavior suggested by the structure has been experimentaly confirmed. It is shown that lithium deintercalation occurs through a first-order transition at 4.02 V vs Li+/Li0. From chemical bond considerations it is shown why the redox potential of a given transition element M in a six-fold coordination involving (M=O)m+ units lies between those observed in oxides and in M2(XO4)3 compounds with (XO4)n− oxo anions (X=S, P, As). 相似文献