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201.
David J. Willock Donald Bethell Saskia Feast Graham J. Hutchings Frank King Philip C. Bulman Page 《Topics in Catalysis》1996,3(1-2):77-89
In an earlier paper we have shown that R-1,3-dithiane 1-oxide adsorbed in zeolite Y is able to dehydrate the S enantiomer
of butan-2-ol at a rate of up to 19 times greater than the R enantioner. Thus a heterogeneous enantioselective catalyst has
been produced by the introduction of a chiral modifier into an achiral zeolite. The modifier remains stable at temperatures
of up to at least 180°C. In this paper we present results of computer simulation work on this system which suggest that the
observed stability of the R-1,3-dithiane 1-oxide in the zeolite is due to proton transfer between the zeolite and the molecule.
We suggest that the molecule is present as a counter cation to the framework. A combination of energy minimisation, Monte
Carlo and molecular dynamics techniques are used to study the zeolite Y and R-1,3-dithiane 1-oxide system. Consistent force
field potentials are used to describe both the zeolite framework and the adsorbed molecule. 相似文献
202.
Saskia M Van Ruth Jacques P Roozen Jan L Cozijnsen 《Journal of the science of food and agriculture》1995,67(2):189-196
The effect of artificial saliva components on flavour release from dehydrated diced red bell peppers (Capsicum annuum) was studied in a mouth model system. This measured the dynamic headspace under oral conditions, such as temperature, volume of the mouth, salivation, and mastication (DHM). The results were compared with a dynamic headspace (DH) and a purge-and-trap (PT) model system. Volatile compounds were analysed by gas chromatography, using flame ionisation detection (FID), mass spectrometry (MS), and sniffing port detection (SPD). SPD revealed that only 12 of the 47 compounds identified by MS and FID possessed odour activity. For all saliva compositions FID peak areas of volatile compounds were largest in the PT system, followed by DHM and DH, respectively. In the PT system the less volatile compounds were relatively better released than other volatile compounds in comparison with the DHM and DH system, for all salivas. The saliva components mucin and α-amylase caused a relative decrease in release of the less volatile compounds in all model systems. An overall decrease in FID peak areas of volatile compounds by the latter components was observed in model system DH only. 相似文献
203.
Sabine?MüllerEmail author Merlin?Bittlinger Kirsten?Brukamp Markus?Christen Orsolya?Friedrich Malte-C.?Gruber Jon?Leefmann Grischa?Merkel Saskia?K.?Nagel Marco?Stier Ralf?J.?Jox 《Ethik in der Medizin》2018,30(2):91-106
Definition of the problem
Fifteen years after establishing neuroethics as an international academic field, neuroethics has emerged as a vibrant, dynamic area of scientific research.Arguments
Within a short period of a few years, specific conferences, journals, research funding programs, professional societies, and institutes were founded. Nonetheless, considerable disagreement about its definition and subject matter still remain. We argue for a differentiated conceptualization according to which the deliberate reflection of ethical problems arising from the neurosciences and their predominantly neurotechnological application belongs as much to neuroethics as does the ethical reflection of the neuroscience of morality. This does not comprise neuroscientific or neuropsychological research on morality itself, but includes the contemplation of the significance of such research for ethics and the law. Here, we provide an overview about the most important topics in neuroethics and elucidate the relevance of neuroethics for a vast diversity of societal domains reaching well beyond medicine and health care.Conclusion
The great potential of neuroethics as a novel branch of academic research lies in finding new answers to pressing questions of high societal relevance by linking neurophilosophy and bioethics topics as well as its broad interdisciplinary network.204.
Anteiso fatty acids (aFAs)-long-chain carboxylic acids with a methyl branch on the (n - 2)-carbon-are among the most simple fatty acids that are chiral. The most frequently occurring aFAs in food are 12-methyltetradecanoic acid (a15:0) and 14-methylhexadecanoic acid (a17:0), structures where the asymmetric carbon is more than 10 carbons separated from the polar head group. Previously, only enantioseparation of 4-methyl-substituted carboxylic fatty acids has been reported by gas chromatography. Here we present the first direct partial enantioresolution of synthesized racemic a15:0-a17:0 on a capillary column coated with 50% heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin diluted in OV1701. Synthesized (S)-(+)-enantiomers were used to demonstrate that the elution order was (R)- prior to (S)-enantiomers. Using this system, food samples (butter, goat's milk fat, suet, human milk, seal oil, cod liver oil) known to contain aFAs were analyzed. Prior to the enantioselective gas chromatography, unsaturated fatty acids were preseparated by urea complexation, silver ion high performance liquid chromatography (Ag+-HPLC), or both from food samples. The fractions of the food samples enriched with methyl-branched fatty acids were then analyzed by GC/MS in the SIM mode. The measurements confirmed that the (S)-enantiomer of a15:0 (ee >96%), a16:0, and a17:0 (ee >90%, respectively) dominated in all samples. While the (R)-enantiomers could not be identified in samples from ruminants and human milk, their presence could be established in cod liver and seal oil (ee <86%). 相似文献
205.
206.
Biosynthesis of the Peptide Antibiotic Feglymycin by a Linear Nonribosomal Peptide Synthetase Mechanism
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Melanie Gonsior Dr. Agnes Mühlenweg Marcel Tietzmann Dr. Saskia Rausch Annette Poch Prof. Dr. Roderich D. Süssmuth 《Chembiochem : a European journal of chemical biology》2015,16(18):2610-2614
Feglymycin, a peptide antibiotic produced by Streptomyces sp. DSM 11171, consists mostly of nonproteinogenic phenylglycine‐type amino acids. It possesses antibacterial activity against methicillin‐resistant Staphylococcus aureus strains and antiviral activity against HIV. Inhibition of the early steps of bacterial peptidoglycan synthesis indicated a mode of action different from those of other peptide antibiotics. Here we describe the identification and assignment of the feglymycin (feg) biosynthesis gene cluster, which codes for a 13‐module nonribosomal peptide synthetase (NRPS) system. Inactivation of an NRPS gene and supplementation of a hydroxymandelate oxidase mutant with the amino acid l ‐Hpg proved the identity of the feg cluster. Feeding of Hpg‐related unnatural amino acids was not successful. This characterization of the feg cluster is an important step to understanding the biosynthesis of this potent antibacterial peptide. 相似文献
207.
Chlorine and sodium chemical shift imaging during acute stroke in a rat model at 9.4 Tesla 总被引:1,自引:1,他引:0
Sebastian Baier Philipp Krämer Saskia Grudzenski Marc Fatar Stefan Kirsch Lothar R. Schad 《Magma (New York, N.Y.)》2014,27(1):71-79
Object
A triple-resonant coil setup with an 1H linear resonator and a double-tuned 23Na/35Cl surface coil was used to study the evolution of T 2 * and M 0 for 35Cl and 23Na in a rat stroke model during the acute phase at 9.4 Tesla.Materials and methods
In vivo measurements were performed 1.5–7 h after onset of stroke (n = 2), ten days after onset (n = 1) and on a healthy control rat by a chemical shift imaging sequence. Measurement times were 15 min (23Na) and 57 min (35Cl).Results
The relaxation times ten days after onset [T 2 * = 14.3 ± 1.8 ms (23Na) and 6.0 ± 1.3 ms (35Cl)] are clearly prolonged in comparison to a healthy rat [T 2 * = 4.8 ± 0.6 ms (23Na) and 2.1 ± 0.3 ms (35Cl)] and the acute phase [T 2 * = 5.6 ± 0.2 ms (23Na) and 1.9 ± 0.1 ms (35Cl)].Conclusion
M 0 in the infarcted region clearly rises later and slower for chlorine than for sodium. To the best of our knowledge, these are the first combined proton, sodium, and chlorine measurements in an animal stroke model during the acute phase. 相似文献208.
209.
210.