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191.
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193.
Background
Inference of protein interaction networks from various sources of data has become an important topic of both systems and computational biology. Here we present a supervised approach to identification of gene expression regulatory networks. 相似文献194.
Background
Satellite repeats represent one of the most dynamic components of higher plant genomes, undergoing rapid evolutionary changes of their nucleotide sequences and abundance in a genome. However, the exact molecular mechanisms driving these changes and their eventual regulation are mostly unknown. It has been proposed that amplification and homogenization of satellite DNA could be facilitated by extrachromosomal circular DNA (eccDNA) molecules originated by recombination-based excision from satellite repeat arrays. While the models including eccDNA are attractive for their potential to explain rapid turnover of satellite DNA, the existence of satellite repeat-derived eccDNA has not yet been systematically studied in a wider range of plant genomes. 相似文献195.
Ladislav Planka Petr Gal Helga Kecova Jiri Klima Jana Hlucilova Eva Filova Evzen Amler Petr Krupa Leos Kren Robert Srnec Lucie Urbanova Jana Lorenzova Alois Necas 《BMC biotechnology》2008,8(1):1-9
Background
Serum and high ionic strength solutions constitute important barriers to cationic lipid-mediated intravenous gene transfer. Preparation or incubation of lipoplexes in these media results in alteration of their biophysical properties, generally leading to a decrease in transfection efficiency. Accurate quantification of these changes is of paramount importance for the success of lipoplex-mediated gene transfer in vivo.Results
In this work, a novel time-resolved fluorescence resonance energy transfer (FRET) methodology was used to monitor lipoplex structural changes in the presence of phosphate-buffered saline solution (PBS) and fetal bovine serum. 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/pDNA lipoplexes, prepared in high and low ionic strength solutions, are compared in terms of complexation efficiency. Lipoplexes prepared in PBS show lower complexation efficiencies when compared to lipoplexes prepared in low ionic strength buffer followed by addition of PBS. Moreover, when serum is added to the referred formulation no significant effect on the complexation efficiency was observed. In physiological saline solutions and serum, a multilamellar arrangement of the lipoplexes is maintained, with reduced spacing distances between the FRET probes, relative to those in low ionic strength medium.Conclusion
The time-resolved FRET methodology described in this work allowed us to monitor stability and characterize quantitatively the structural changes (variations in interchromophore spacing distances and complexation efficiencies) undergone by DOTAP/DNA complexes in high ionic strength solutions and in presence of serum, as well as to determine the minimum amount of potentially cytotoxic cationic lipid necessary for complete coverage of DNA. This constitutes essential information regarding thoughtful design of future in vivo applications. 相似文献196.
Vale N Collins MS Gut J Ferraz R Rosenthal PJ Cushion MT Moreira R Gomes P 《Bioorganic & medicinal chemistry letters》2008,18(2):485-488
A series of primaquine-derived imidazolidin-4-ones were screened for their in vitro activity against Pneumocystis carinii and Plasmodium falciparum W2 strain. Most compounds were active against P. carinii above 10 microg/mL and displayed slight to marked activity. The imidazolidin-4-ones most active against P. carinii were also those most active antiplasmodial agents, in the muM range. One of the tested imidazolidin-4-ones was slightly more active than the parent primaquine and may represent a lead compound for the development of novel anti-P. carinii 8-aminoquinolines with increased stability and resistance to metabolic inactivation. 相似文献
197.
Vladimir Sychrovsky Silvie Foldynova-Trantirkova Nada Spackova Koen Robeyns Luc Van Meervelt Wulf Blankenfeldt Zuzana Vokacova Jiri Sponer Lukas Trantirek 《Nucleic acids research》2009,37(21):7321-7331
We describe a novel, fundamental property of nucleobase structure, namely, pyramidilization at the N1/9 sites of purine and pyrimidine bases. Through a combined analyses of ultra-high-resolution X-ray structures of both oligonucleotides extracted from the Nucleic Acid Database and isolated nucleotides and nucleosides from the Cambridge Structural Database, together with a series of quantum chemical calculations, molecular dynamics (MD) simulations, and published solution nuclear magnetic resonance (NMR) data, we show that pyramidilization at the glycosidic nitrogen is an intrinsic property. This property is common to isolated nucleosides and nucleotides as well as oligonucleotides—it is also common to both RNA and DNA. Our analysis suggests that pyramidilization at N1/9 sites depends in a systematic way on the local structure of the nucleoside. Of note, the pyramidilization undergoes stereo-inversion upon reorientation of the glycosidic bond. The extent of the pyramidilization is further modulated by the conformation of the sugar ring. The observed pyramidilization is more pronounced for purine bases, while for pyrimidines it is negligible. We discuss how the assumption of nucleic acid base planarity can lead to systematic errors in determining the conformation of nucleotides from experimental data and from unconstrained MD simulations. 相似文献
198.
Jiri Dolezal Jong-Suk Song Jan Altman Stepan Janecek Tomas Cerny Miroslav Srutek Jiri Kolbek 《Ecological Research》2009,24(2):281-290
Secondary woodlands in South Korea cover most mountains from low to middle elevations. While general patterns of forest succession
are well understood, little is known about mechanisms of stand recovery after disturbance. We examined the spatio-temporal
variations in establishment, growth, size inequality, and mode of competition among trees in a 50-year-old post-logging Quercus mongolica-dominated stand. We further compared the growth and stem allometry of single trees, presumably of seed origin, with multi-stemmed
trees resprouting from stumps. Q. mongolica formed the upper canopy 16–22 m tall, 88.3% of total stand basal area, and 36.2% of total stem density, with most trees established
during the first post-logging decade (51.2% were resprouts). During the first three decades, the Q. mongolica recruits grew exponentially, and disproportionately more in diameter than few older reserved trees left after the last cutting.
This substantially decreased size inequality. The reverse trend was observed from 1994 to 2004: larger trees grow more, indicating
an increasing asymmetry of competition for light. Neighborhood analysis revealed that when target trees had more or larger
neighbors, their exponential phase of growth was reduced and maximum size was decreased. After the 50 years of stand development,
more than 70% of Q. mongolica showed growth decline as a result of competitive stress, and mortality was about 30%, concentrated in smaller size classes.
Compared to single stems, resprouts within clones do not seem to compete less asymmetric as might be expected based on studies
of clonal herbaceous plants and physiological integration within genets. As Q. mongolica was also negatively affected by competition from woody species currently prevailing in the lower tree stratum (Tilia amurensis, Acer mono, Fraxinus rhynchophylla, Acer pseudosieboldianum), we predict the stand will become increasingly dominated by these more shade-tolerant trees. 相似文献
199.
Olga Brantova Befekadu Asfaw Jana Sladkova Helena Poupetova Jan Zivny Martin Magner Jan Krusek Katerina Vesela Hana Hansikova Jana Ledvinova Marketa Tesarova Jiri Zeman 《Biologia》2009,64(2):394-401
α-Mannosidosis is a lysosomal storage disorder caused by α-mannosidase deficiency. Clinical course of the disease ranges from severe infantile to milder juvenile type and includes
mental retardation, skeletal deformities, coarse facies, hepatomegaly and hearing loss. The aim of the study was to analyse
mitochondrial ultrastructure and function in cultivated fibroblasts from three patients with α-mannosidosis. All patients were homozygous for the c.2248C>T mutation in the MAN2B1 gene encoding lysosomal α-mannosidase. The mutation results in incorrect protein folding and severe decrease of α-mannosidase activity. The misfolded protein is retained by the control system of endoplasmic reticulum (ER). In analysed
fibroblasts, we observed dilated ER, higher amount of aberrant mitochondria and reduced mitochondrial mass compared to controls.
Respiratory chain complex IV, cytochrome c oxidase (COX), activity and the ratio between COX and citrate synthase (control enzyme) were significantly increased in comparison
to controls (P < 0.05). Furthermore, the activity at least from one of other respiratory chain complexes was increased in each studied cell
line. Mitochondrial membrane potential as well as reactive oxygen species production were comparable with controls. Based
on our results, we hypothesize more profound effect of swelled and damaged mitochondria and ER dilatation on tissues with
higher energy demand than fibroblasts have. 相似文献
200.
Mapping field-scale spatial patterns of size and activity of the denitrifier community 总被引:4,自引:0,他引:4
Laurent Philippot Jiri uhel Nicolas P.A. Saby Dominique Chèneby Alicia Chroáková David Bru Dominique Arrouays Fabrice Martin-Laurent Miloslav imek 《Environmental microbiology》2009,11(6):1518-1526
There is ample evidence that microbial processes can exhibit large variations in activity on a field scale. However, very little is known about the spatial distribution of the microbial communities mediating these processes. Here we used geostatistical modelling to explore spatial patterns of size and activity of the denitrifying community, a functional guild involved in N-cycling, in a grassland field subjected to different cattle grazing regimes. We observed a non-random distribution pattern of the size of the denitrifier community estimated by quantification of the denitrification genes copy numbers with a macro-scale spatial dependence (6–16 m) and mapped the distribution of this functional guild in the field. The spatial patterns of soil properties, which were strongly affected by presence of cattle, imposed significant control on potential denitrification activity, potential N2 O production and relative abundance of some denitrification genes but not on the size of the denitrifier community. Absolute abundance of most denitrification genes was not correlated with the distribution patterns of potential denitrification activity or potential N2 O production. However, the relative abundance of bacteria possessing the nosZ gene encoding the N2 O reductase in the total bacterial community was a strong predictor of the N2 O/(N2 + N2 O) ratio, which provides evidence for a relationship between bacterial community composition based on the relative abundance of denitrifiers in the total bacterial community and ecosystem processes. More generally, the presented geostatistical approach allows integrated mapping of microbial communities, and hence can facilitate our understanding of relationships between the ecology of microbial communities and microbial processes along environmental gradients. 相似文献