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Lawrence R. Williams Melody R. Donald Karen S. Jodelis 《Biotechnic & histochemistry》1989,64(4):175-180
A modified method for improved preservation and optical resolution of acetylcholinesterase (AChE)-containing structures in adult rat brain is described. Optimal tissue preparation included fixation in paraformaldehyde 4%, glutaraldehyde 0.1%, and sucrose 7% in 0.1 M Sorensen's phosphate buffer, pH 7.4, rinsing in buffer 50 mM with respect to NLL, Q and 2% with respect to sucrose, acetone dehydration, vacuum infiltration widi LKB Historesin, and polymerization at 4 C, overnight incubation of 10 μm sections at 37 C in the AChE histochemical reaction mixture and silver intensification according to Hedreen et al. Demonstration of AChE enzyme activity in the cholinergic projection from the rat basal forebrain to the ipsilateral hippocampus exemplifies the usefulness of the technique. The method provides an excellent demonstration of AChE-positive axonal processes and enables the pharmacohis-tochemical visualization of cholinergic neurons. This procedure offers a convenient method for analysis of cholinergic neurons that avoids potential artifacts inherent in other AChE histochemical procedures. 相似文献
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Christa P. H. Mulder M. Nicole Grant-Hoffman David R. Towns Peter J. Bellingham David A. Wardle Melody S. Durrett Tadashi Fukami Karen I. Bonner 《Biological invasions》2009,11(7):1671-1688
Introduced rats (Rattus spp.) can affect island vegetation structure and ecosystem functioning, both directly and indirectly (through the reduction
of seabird populations). The extent to which structure and function of islands where rats have been eradicated will converge
on uninvaded islands remains unclear. We compared three groups of islands in New Zealand: islands never invaded by rats, islands
with rats, and islands on which rats have been controlled. Differences between island groups in soil and leaf chemistry and
leaf production were largely explained by burrow densities. Community structure of woody seedlings differed by rat history
and burrow density. Plots on islands with high seabird densities had the most non-native plant species. Since most impacts
of rats were mediated through seabird density, the removal of rats without seabird recolonization is unlikely to result in
a reversal of these processes. Even if seabirds return, a novel plant community may emerge. 相似文献
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Cell cycle plays a crucial role in regulating the pathway used to repair DNA double-strand breaks (DSBs). In Saccharomyces cerevisiae, homologous recombination is primarily limited to non-G1 cells as the formation of recombinogenic single-stranded DNA requires CDK1-dependent 5′ to 3′ resection of DNA ends. However, the effect of cell cycle on non-homologous end joining (NHEJ) is not yet clearly defined. Using an assay to quantitatively measure the contributions of each repair pathway to repair product formation and cellular survival after DSB induction, we found that NHEJ is most efficient at G1, and markedly repressed at G2. Repression of NHEJ at G2 is achieved by efficient end resection and by the reduced association of core NHEJ proteins with DNA breaks, both of which depend on the CDK1 activity. Importantly, repression of 5′ end resection by CDK1 inhibition at G2 alone did not fully restore either physical association of Ku/Dnl4-Lif1 with DSBs or NHEJ proficiency to the level at G1. Expression of excess Ku can partially offset the inhibition of end joining at G2. The results suggest that regulation of Ku/Dnl4-Lif1 affinity for DNA ends may contribute to the cell cycle-dependent modulation of NHEJ efficiency. 相似文献
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James M Williams Charles R White Melody M Chang Elisha R Injeti Lubo Zhang William J Pearce 《Journal of applied physiology》2006,100(6):1857-1866
The present study tests the hypothesis that chronic hypoxia enhances reactivity to nitric oxide (NO) through age-dependent increases in soluble guanylate cyclase (sGC) and protein kinase G (PKG) activity. In term fetal and adult ovine carotids, chronic hypoxia had no significant effect on mRNA levels for the beta1-subunit of sGC, but depressed sGC abundance by 16% in fetal and 50% in adult arteries, through possible depression of rates of mRNA translation (15% in fetal and 50% in adult) and/or increased protein turnover. Chronic hypoxia also depressed the catalytic activity of sGC, but only in fetal arteries (63%). Total sGC activity was reduced by chronic hypoxia in both fetal (69%) and adult (37%) carotid homogenates, but this effect was not observed in intact arteries when sGC activity was measured by timed accumulation of cGMP. In intact arteries treated with 300 microM 3-isobutyl-1-methylxanthine (IBMX), chronic hypoxia dramatically enhanced sGC activity in fetal (186%) but not adult (89%) arteries. This latter observation suggests that homogenization either removed an sGC activator, released an sGC inhibitor, or altered the phosphorylation state of the enzyme, resulting in reduced activity. In the absence of IBMX, chronic hypoxia had no significant effect on rates of cGMP accumulation. Chronic hypoxia also depressed the ability of the cGMP analog, 8-(p-chlorophenylthio)-cGMP, to promote vasorelaxation in both fetal (8%) and adult (12%) arteries. Together, these results emphasize the fact that intact and homogenized artery studies of sGC activity do not always yield equivalent results. The results further suggest that enhancement of reactivity to NO by chronic hypoxia must occur upstream of PKG and can only be possible if changes in cGMP occurred in functional compartments that afforded either temporal or chemical protection to the actions of phosphodiesterase. The range and age dependence of hypoxic effects observed also suggest that some responses to hypoxia must be compensatory and homeostatic, with reactivity to NO as the primary regulated variable. 相似文献
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Melody Puckridge Nikos Andreakis Sharon A. Appleyard Robert D. Ward 《Molecular ecology resources》2013,13(1):32-42
Identification of taxonomical units underpins most biological endeavours ranging from accurate biodiversity estimates to the effective management of sustainably harvested, protected or endangered species. Successful species identification is now frequently based on a combination of approaches including morphometrics and DNA markers. Sequencing of the mitochondrial COI gene is an established methodology with an international campaign directed at barcoding all fishes. We employed COI sequencing alongside traditional taxonomic identification methods and uncovered instances of deep intraspecific genetic divergences among flathead species. Sixty‐five operational taxonomic units (OTUs) were observed across the Indo‐West Pacific from just 48 currently recognized species. The most comprehensively sampled taxon, Platycephalus indicus, exhibited the highest levels of genetic diversity with eight lineages separated by up to 16.37% genetic distance. Our results clearly indicate a thorough reappraisal of the current taxonomy of P. indicus (and its three junior synonyms) is warranted in conjunction with detailed taxonomic work on the other additional Platycephalidae OTUs detected by DNA barcoding. 相似文献