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181.
Comparison of Ca(2+) sparks produced independently by two ryanodine receptor isoforms (type 1 or type 3) 下载免费PDF全文
Conklin MW Ahern CA Vallejo P Sorrentino V Takeshima H Coronado R 《Biophysical journal》2000,78(4):1777-1785
The molecular determinants of a Ca(2+) spark, those events that determine the sudden opening and closing of a small number of ryanodine receptor (RyR) channels limiting Ca(2+) release to a few milliseconds, are unknown. As a first step we investigated which of two RyR isoforms present in mammalian embryonic skeletal muscle, RyR type 1(RyR-1) or RyR type 3 (RyR-3) has the ability to generate Ca(2+) sparks. Their separate contributions were investigated in intercostal muscle cells of RyR-1 null and RyR-3 null mouse embryos. A comparison of Ca(2+) spark parameters of RyR-1 null versus RyR-3 null cells measured at rest with fluo-3 showed that neither the peak fluorescence intensity (DeltaF/F(o) = 1.25 +/- 0.7 vs. 1.55 +/- 0.6), spatial width at half-max intensity (FWHM = 2.7 +/- 1.2 vs. 2.6 +/- 0.6 microm), nor the duration at half-max intensity (FTHM = 45 +/- 49 vs. 43 +/- 25 ms) was significantly different. Sensitivity to caffeine (0.1 mM) was remarkably different, with sparks in RyR-1 null myotubes becoming brighter and longer in duration, whereas those in RyR-3 null cells remained unchanged. Controls performed in double RyR-1/RyR-3 null cells obtained by mice breeding showed that sparks were not observed in the absence of both isoforms in >150 cells imaged. In conclusion, 1) RyR-1 and RyR-3 appear to be the only intracellular Ca(2+) channels that participate in Ca(2+) spark activity in embryonic skeletal muscle; 2) except in their responsiveness to caffeine, both isoforms have the ability to produce Ca(2+) sparks with nearly identical properties, so it is rather unlikely that a single RyR isoform, when others are also present, would be responsible for Ca(2+) sparks; and 3) because RyR-1 null cells are excitation-contraction (EC) uncoupled and RyR-3 null cells exhibit a normal phenotype, Ca(2+) sparks result from the inherent activity of small clusters of RyRs regardless of the participation of these RyRs in EC coupling. 相似文献
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Santa-María I Hernández F Smith MA Perry G Avila J Moreno FJ 《Molecular and cellular biochemistry》2005,278(1-2):203-212
Aberrant aggregation of microtubule associated protein tau is the main characteristic of different disorders known as tauopathies.
Different compounds have been described to facilitate tau aberrant aggregation. In this work, we demonstrate that oxidized
products of dopamine (neurotoxic dopamine quinone), a neurotransmitter involved in Parkinson's disease, promote tau polymerization.
Curiously, neurons expressing dopamine (substantia nigra) show a low content of tau protein and seldom have tau aggregation
in tauopathies. In non-dopaminergic neurons, quinone oxidation products may be involved in tau polymerization. These results
support a link between oxidative damage and the onset of tauopathies. (Mol Cell Biochem 278: 203–212, 2005) 相似文献
185.
Wang Q Jia R Ye C Garcia M Li J Hidalgo IJ 《In vitro cellular & developmental biology. Animal》2005,41(3-4):97-103
Summary Uridine 5′-diphospho-N-acetylgalactosamine glycosyltransferases (UGTs) and sulfotransferases (SULTs) are 2 phase II enzymes that are actively involved
in detoxification processes as well as in drug metabolism. Compared with cytochrome P450 enzymes, the role of UGTs and SULTs
in drug metabolism has received little attention. Liver microsomes, S9 fractions, and cryopreserved hepatocytes from human,
dog, cynomolgus monkey, mouse, and rat were used as matrices in the study. Single compound, 7-hydroxycoumarin (7-HC), along
with necessary cofactors was dosed into the matrices and incubated at 37° C; formation of two metabolites, 7-HC-glucuronide
and 7-HC-sulfate, was determined with liquid chromatography with tandem mass spectrometry. Within the same species, the UGTs
activities in microsomes and S9 fractions were comparable. In addition, UGTs activities in cryopreserved hepatocytes were
lower than in the other matrices. Also, the SULTs activities were much higher in S9 fractions than in cryopreserved hepatocytes
and microsomes. Species differences on UGTs and SULTs activities were also observed. The results indicated that S9 fractions,
microsomes, and cryopreserved hepatocytes might be useful for UGTs metabolism study, whereas S9 fractions appear to be the
most appropriate matrix for both UGTs and SULTs metabolism. Species differences with respect to phase II metabolism also need
to be taken into consideration when selecting an in vitro system to evaluate various aspects of drug metabolism. 相似文献
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Ferreira EN Pires LC Parmigiani RB Bettoni F Puga RD Pinheiro DG Andrade LE Cruz LO Degaki TL Faria M Festa F Giannella-Neto D Giorgi RR Goldman GH Granja F Gruber A Hackel C Henrique-Silva F Malnic B Manzini CV Marie SK Martinez-Rossi NM Oba-Shinjo SM Pardini MI Rahal P Rainho CA Rogatto SR Romano CM Rodrigues V Sales MM Savoldi M da Silva ID da Silva NP de Souza SJ Tajara EH Silva WA Simpson AJ Sogayar MC Camargo AA Carraro DM 《Genetics and molecular research : GMR》2004,3(4):493-511
188.
Vilar M Saurí A Monné M Marcos JF von Heijne G Pérez-Payá E Mingarro I 《The Journal of biological chemistry》2002,277(26):23447-23452
Virus-encoded movement proteins (MPs) mediate cell-to-cell spread of viral RNA through plant membranous intercellular connections, the plasmodesmata. The molecular pathway by which MPs interact with viral genomes and target plasmodesmata channels is largely unknown. The 9-kDa MP from carnation mottle carmovirus (CarMV) contains two potential transmembrane domains. To explore the possibility that this protein is in fact an intrinsic membrane protein, we have investigated its insertion into the endoplasmic reticulum membrane. By using in vitro translation in the presence of dog pancreas microsomes, we demonstrate that CarMV p9 inserts into the endoplasmic reticulum without the aid of any additional viral or plant host components. We further show that the membrane topology of CarMV p9 is N(cyt)-C(cyt) (N and C termini of the protein facing the cytoplasm) by in vitro translation of a series of truncated and full-length constructs with engineered glycosylation sites. Based on these results, we propose a topological model in which CarMV p9 is anchored in the membrane with its N- and C-terminal tail segments interacting with its soluble, RNA-bound partner CarMV p7, to accomplish the viral cell-to-cell movement function. 相似文献
189.
Carvalho W Silva SS Vitolo M Felipe MG Mancilha IM 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(1-2):109-112
Candida guilliermondii cells were immobilized in Ca-alginate beads and used for xylitol production from concentrated sugarcane bagasse hydrolysate during five successive fermentation batches, each lasting 48 hours. The bioconversion efficiency of 53.2%, the productivity of 0.50 g/l x h and the final xylitol concentration of 23.8 g/l obtained in the first batch increased to 61.5%, 0.59 g/l x h and 28.4 g/l, respectively, in the other four batches (mean values), with variation coefficients of up to 2.3%. 相似文献
190.
Iron deficiency changed markedly the shape of the leaf chlorophyll fluorescence induction kinetics during a dark-light transition,
the so-called Kautsky effect. Changes in chlorophyll fluorescence lifetime and yield were observed, increasing largely the
minimal and the intermediate chlorophyll fluorescence levels, with a marked dip between the intermediate and the maximum levels
and loss of the secondary peak after the maximum. During the slow changes, the lifetime-yield relationship was found to be
linear and curvilinear (towards positive lifetime values) in control and Fe-deficient leaves, respectively. These results
suggested that part of the Photosystem II antenna in Fe-deficient leaves emits fluorescence with a long lifetime. In dark-adapted
Fe-deficient leaves, measurements in the picosecond-nanosecond time domain confirmed the presence of a 3.3-ns component, contributing
to 15% of the total fluorescence. Computer simulations revealed that upon illumination such contribution is also present and
remains constant, indicating that energy transfer is partially interrupted in Fe-deficient leaves. Photosystem II-enriched
membrane fractions containing different pigment-protein complexes were isolated from control and Fe-deficient leaves and characterized
spectrophotometrically. The photosynthetic pigment composition of the fractions was also determined. Data revealed the presence
of a novel pigment-protein complex induced by Fe deficiency and an enrichment of internal relative to peripheral antenna complexes.
The data suggest a partial disconnection between internal Photosystem II antenna complexes and the reaction center, which
could lead to an underestimation of the Photosystem II efficiency in dark-adapted, low chlorophyll Fe-deficient leaves, using
chlorophyll fluorescence.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献