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841.
A new route to the imidazole-2-thiones from 2-thiohydantoins. Implications in the study of ergothioneine 总被引:1,自引:0,他引:1
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1. 2-Thiohydantoins are reduced by borohydrides to 4(5)-hydroxyimidazolidine-2-thiones, which eliminate water in acid to form imidazole-2-thiones. Both steps take place in mild conditions, in high yield. A number of imidazole-2-thiones have been synthesized by this sequence of steps, with one, two or three substituents in the 1-, 3- and 4(5)-positions. 2. 4(5)-Hydroxyimidazolidine-2-thiones are ammonium pseudo-bases, giving rise to an equilibrium mixture of amino aldehyde, carbinolamine and mesomeric ammonium cationic forms. The elimination of water is suggested to be a property of the mesomeric ammonium cation. 3. The mild conditions in which imidazole-2-thiones are formed from 4(5)-hydroxyimidazolidine-2-thiones are similar to those in which ergothioneine, a naturally occurring imidazole-2-thione of uncertain function, is normally released and measured. It is suggested that the occurrence in vivo of a precursor to ergothioneine, in the form of a 4(5)-hydroxyimidazolidine-2-thione, would explain many otherwise conflicting published data. 相似文献
842.
843.
Ester Gangoso Benjamin Southgate Leanne Bradley Stefanie Rus Felipe Galvez-Cancino Niamh McGivern Esra Güç Chantriolnt-Andreas Kapourani Adam Byron Kirsty M. Ferguson Neza Alfazema Gillian Morrison Vivien Grant Carla Blin IengFong Sou Maria Angeles Marques-Torrejon Lucia Conde Simona Parrinello Steven M. Pollard 《Cell》2021,184(9):2454-2470.e26
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844.
Julian Spagnuolo Natacha Opalka Wesley X. Wen Dragana Gagic Elodie Chabaud Pierdomenico Bellini Matthew D. Bennett Gillian E. Norris Seth A. Darst Marjorie Russel Jasna Rakonjac 《Molecular microbiology》2010,76(1):133-150
Secretins are a family of large bacterial outer membrane channels that serve as exit ports for folded proteins, filamentous phage and surface structures. Despite the large size of their substrates, secretins do not compromise the barrier function of the outer membrane, implying a gating mechanism. The region in the primary structure that forms the putative gate has not previously been determined for any secretin. To identify residues involved in gating the pIV secretin of filamentous bacteriophage f1, we used random mutagenesis of the gene followed by positive selection for mutants with compromised barrier function (‘leaky’ mutants). We identified mutations in 34 residues, 30 of which were clustered into two regions located in the centre of the conserved C‐terminal secretin family domain: GATE1 (that spanned 39 residues) and GATE2 (that spanned 14 residues). An internal deletion constructed in the GATE2 region resulted in a severely leaky phenotype. Three of the four remaining mutations are located in the region that encodes the N‐terminal, periplasmic portion of pIV and could be involved in triggering gate opening. Two missense mutations in the 24‐residue region that separates GATE1 and GATE2 were also constructed. These mutant proteins were unstable, defective in multimerization and non‐functional. 相似文献
845.
T. Ritchie Rodger 《BMJ (Clinical research ed.)》1934,2(3846):544-548
846.
Gillian R. Bullock Isabel Steyaert Graeme Bilbe Robert M. Carey Johan Kips Boel De Paepe Romain Pauwels Marleen Praet Helmy M. Siragy Marc de Gasparo 《Histochemistry and cell biology》2001,115(2):117-124
This study was designed to examine the cellular distribution of the angiotensin II type-1 (AT1) and type-2 (AT2) receptors in the normal human and pathological human lung. Riboprobes were prepared against specific portions of each receptor DNA and labelled with FITC for detection using an anti-FITC antibody in combination with the alkaline phosphatase-anti-alkaline phosphatase technique and new Fuchsin. These were used to detect the presence of receptor mRNA in the lung. Specific antibodies were used to detect receptor protein in cells by immunocytochemistry. Image analysis was used in order to semi-quantify receptor density. AT1 receptor mRNA and protein were localised on vascular smooth muscle cells, macrophages and in the stroma underlying the airways epithelium probably relating to underlying fibroblasts. The AT1 receptor protein was not expressed in the epithelium although there was a low level of mRNA. In contrast, AT2 receptor RNA and protein was observed in the epithelium, with strong staining on the bronchial epithelial cell brush border and also on many of the underlying mucous glands. The AT2 receptor was also present on some endothelial cells. These findings were supported by the presence of mRNA in each case. In patients with chronic obstructive pulmonary disease, there was a five- to sixfold increase in the ratio of AT1 to AT2 receptors in the regions of marked fibrosis surrounding the bronchioles. This correlated well with the reduced lung function as expressed by the forced expiratory volume. 相似文献
847.
Shiow-Fern Ng Jennifer J. Rouse Francis D. Sanderson Victor Meidan Gillian M. Eccleston 《AAPS PharmSciTech》2010,11(3):1432-1441
Over the years, in vitro Franz diffusion experiments have evolved into one of the most important methods for researching transdermal drug administration.
Unfortunately, this type of testing often yields permeation data that suffer from poor reproducibility. Moreover, this feature
frequently occurs when synthetic membranes are used as barriers, in which case biological tissue-associated variability has
been removed as an artefact of total variation. The objective of the current study was to evaluate the influence of a full-validation
protocol on the performance of a tailor-made array of Franz diffusion cells (GlaxoSmithKline, Harlow, UK) available in our
laboratory. To this end, ibuprofen was used as a model hydrophobic drug while synthetic membranes were used as barriers. The
parameters investigated included Franz cell dimensions, stirring conditions, membrane type, membrane treatment, temperature
regulation and sampling frequency. It was determined that validation dramatically reduced derived data variability as the
coefficient of variation for steady-state ibuprofen permeation from a gel formulation was reduced from 25.7% to 5.3% (n = 6). Thus, validation and refinement of the protocol combined with improved operator training can greatly enhance reproducibility
in Franz cell experimentation. 相似文献
848.
Janelle M. Hoskins Annette S. Gross Gillian M. Shenfield Laurent P. Rivory 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,754(2):1544
A rapid and sensitive liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) assay has been developed for the measurement of moclobemide and metabolites, Ro12-5637 and Ro12-8095, in human plasma. Sample preparation (0.5 ml plasma) involves solid-phase extraction using C18 cartridges. A Nova-Pak phenyl column (Waters, 4 μm, 150×2 mm I.D.) was employed for analyte separation with a mixture of 0.2 M ammonium formate buffer, pH 3.57 and acetonitrile as the mobile phase. The within- and between-day precisions of the assay were <18% and the limit of quantification for all analytes was 0.01 μg/ml. The total run-time was 6 min. The method described was used to measure moclobemide, Ro12-5637 and Ro12-8095 in human plasma following an oral 300 mg dose. 相似文献
849.
850.