全文获取类型
收费全文 | 250篇 |
免费 | 16篇 |
专业分类
266篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 24篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 7篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有266条查询结果,搜索用时 0 毫秒
101.
Alexandra Calteau David P Fewer Amel Latifi Thérèse Coursin Thierry Laurent Jouni Jokela Cheryl A Kerfeld Kaarina Sivonen J?rn Piel Muriel Gugger 《BMC genomics》2014,15(1)
Background
Cyanobacteria are an ancient lineage of photosynthetic bacteria from which hundreds of natural products have been described, including many notorious toxins but also potent natural products of interest to the pharmaceutical and biotechnological industries. Many of these compounds are the products of non-ribosomal peptide synthetase (NRPS) or polyketide synthase (PKS) pathways. However, current understanding of the diversification of these pathways is largely based on the chemical structure of the bioactive compounds, while the evolutionary forces driving their remarkable chemical diversity are poorly understood.Results
We carried out a phylum-wide investigation of genetic diversification of the cyanobacterial NRPS and PKS pathways for the production of bioactive compounds. 452 NRPS and PKS gene clusters were identified from 89 cyanobacterial genomes, revealing a clear burst in late-branching lineages. Our genomic analysis further grouped the clusters into 286 highly diversified cluster families (CF) of pathways. Some CFs appeared vertically inherited, while others presented a more complex evolutionary history. Only a few horizontal gene transfers were evidenced amongst strongly conserved CFs in the phylum, while several others have undergone drastic gene shuffling events, which could result in the observed diversification of the pathways.Conclusions
Therefore, in addition to toxin production, several NRPS and PKS gene clusters are devoted to important cellular processes of these bacteria such as nitrogen fixation and iron uptake. The majority of the biosynthetic clusters identified here have unknown end products, highlighting the power of genome mining for the discovery of new natural products.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-977) contains supplementary material, which is available to authorized users. 相似文献102.
The nuclear receptor family orchestrates many functions related to reproduction, development, metabolism, and adaptation to the circadian cycle. The majority of these receptors are expressed in the kidney, but their exact quantitative localization in this ultrastructured organ remains poorly described, making it difficult to elucidate the renal function of these receptors. In this report, using quantitative PCR on microdissected mouse renal tubules, we established a detailed quantitative expression map of nuclear receptors along the nephron. This map can serve to identify nuclear receptors with specific localization. Thus, we unexpectedly found that the estrogen-related receptor β (ERRβ) is expressed predominantly in the thick ascending limb (TAL) and, to a much lesser extent, in the distal convoluted tubules. In vivo treatment with an ERR inverse agonist (diethylstilbestrol) showed a link between this receptor family and the expression of the Na+,K+-2Cl− cotransporter type 2 (NKCC2), and resulted in phenotype presenting some similarities with the Bartter syndrom (hypokalemia, urinary Na+ loss and volume contraction). Conversely, stimulation of ERRβ with a selective agonist (GSK4716) in a TAL cell line stimulated NKCC2 expression. All together, these results provide broad information regarding the renal expression of all members of the nuclear receptor family and have allowed us to identify a new regulator of ion transport in the TAL segments. 相似文献
103.
Amel Rayah Jean M. Kanellopoulos Francesco Di Virgilio 《Microbes and infection / Institut Pasteur》2012,14(14):1254-1262
Immune cells express receptors for extracellular nucleotides named P2 receptors. P2 receptors transduce signals delivered by nucleotides present in the extracellular environment. Accruing evidence shows that purinergic signalling has a profound effect on multiple immune cell responses such as T lymphocyte proliferation, chemotaxis, cytokine release, phagocytosis, Ag presentation and cytotoxicity. This makes P2 receptors an attractive target for the therapy of immuno-mediated disease and cancer. 相似文献
104.
Amel?Soltani Hela?Louati Amel?Hanachi Fida?Ben Salem Naceur?Essid Patricia?Aissa Ezzeddine?MahmoudiEmail author Hamouda?Beyrem 《Biologia》2012,67(2):377-383
A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels
of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg−1), P2: medium (25 mg kg−1) and P3: high (250 mg kg−1)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant
differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate
indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species
abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in
nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance
to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination. 相似文献
105.
Besbes M Omri A Cheraif I Daami M Jannet HB Mastouri M Aouni M Selmi B 《Chemistry & biodiversity》2012,9(4):829-839
The essential oils isolated from three organs, i.e., fruits, stems and leaves, and flowers, of the endemic North African plant Scabiosa arenaria Forssk. were screened for their chemical composition, as well as their possible antibacterial, anticandidal, and antifungal properties. According to the GC-FID and GC/MS analyses, 61 (99.26% of the total oil composition), 79 (98.43%), and 51 compounds (99.9%) were identified in the three oils, respectively. While α-thujone (34.39%), camphor (17.48%), and β-thujone (15.29%) constituted the major compounds of the fruit oil, chrysanthenone (23.43%), together with camphor (12.98%) and α-thujone (10.7%), were the main constituents of the stem and leaf oil. In the case of the flower oil, also chrysanthenone (38.52%), camphor (11.75%), and α-thujone (9.5%) were identified as the major compounds. Furthermore, the isolated oils were tested against 16 Gram-positive and Gram-negative bacteria, four Candida species, and nine phytopathogenic fungal strains. It was found that the oils exhibited interesting antibacterial and anticandidal activities, comparable to those of thymol, which was used as positive control, but no activity against the phytopathogenic fungal strains was observed. 相似文献
106.
Jeanjean R Talla E Latifi A Havaux M Janicki A Zhang CC 《Environmental microbiology》2008,10(10):2574-2585
Non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) are necessary for the production of a variety of secondary metabolites, such as siderophores involved in iron acquisition. In response to iron limitation, the cyanobacterium Anabaena sp. strain PCC 7120 synthesizes several siderophores. The chromosome of this organism contains a large gene cluster of 76 kb with 24 open-reading frames from all2658 to all2635, including those that encode seven NRPSs and two PKSs. The function of this gene cluster was unknown, and one possibility could be the synthesis of siderophores. These genes were indeed activated under conditions of iron limitation. One mutant, MDelta41-49, bearing a large deletion of 43.4 kb in this gene cluster, synthesized considerably less siderophores and contained less iron as compared with the wild type. Its growth rate was similar to the wild type in the presence of iron, but was reduced when iron became limiting. Two other mutants, MDelta44-45 and MDelta47-49, lacking either all2644 and all2645, or all2647, all2648 and all2649 respectively, produced more siderophores than MDelta41-49, but less than the wild type. These genes were also activated under oxidative stress conditions to which MDelta41-49 was highly sensitive, consistent with the importance of iron in oxidative stress response. We propose that this gene cluster is involved in the synthesis of siderophores in Anabaena sp. PCC 7120 and plays an important role in defence against oxidative stress. 相似文献
107.
Haj Khelil A Deguillien M Morinière M Ben Chibani J Baklouti F 《The FEBS journal》2008,275(6):1150-1162
It has long been considered that cryptic splice sites are ignored by the splicing machinery in the context of intact genuine splice sites. In the present study, it is shown that cryptic splice sites are utilized in all circumstances, when the authentic site is intact, partially functional or completely abolished. Their use would therefore contribute to a background lack of fidelity in the context of the wild-type sequence. We also found that a mutation at the 5' splice site of beta-globin intron 1 accommodates multiple cryptic splicing pathways, including three previously reported pathways. Focusing on the two major cryptic 5' splice sites within beta-globin exon 1, we show that cryptic splice site selection ex vivo varies depending upon: (a) the cell stage of development during terminal erythroid differentiation; (b) the nature of the mutation at the authentic 5' splice site; and (c) the nature of the promoter. Finally, we found that the two major cryptic 5' splice sites are utilized with differential efficiencies in two siblings sharing the same beta-globin chromosome haplotype in the homozygous state. Collectively, these data suggest that intrinsic, sequence specific factors and cell genetic background factors both contribute to promote a subtle differential use of cryptic splice sites in vivo. 相似文献
108.
109.
110.
Jean-Fran?ois Humbert Valérie Barbe Amel Latifi Muriel Gugger Alexandra Calteau Therese Coursin Aurélie Lajus Vanina Castelli Sophie Oztas Ga?lle Samson Cyrille Longin Claudine Medigue Nicole Tandeau de Marsac 《PloS one》2013,8(8)
Microcystis aeruginosa is one of the most common bloom-forming cyanobacteria in freshwater ecosystems worldwide. This species produces numerous secondary metabolites, including microcystins, which are harmful to human health. We sequenced the genomes of ten strains of M. aeruginosa in order to explore the genomic basis of their ability to occupy varied environments and proliferate. Our findings show that M. aeruginosa genomes are characterized by having a large open pangenome, and that each genome contains similar proportions of core and flexible genes. By comparing the GC content of each gene to the mean value of the whole genome, we estimated that in each genome, around 11% of the genes seem to result from recent horizontal gene transfer events. Moreover, several large gene clusters resulting from HGT (up to 19 kb) have been found, illustrating the ability of this species to integrate such large DNA molecules. It appeared also that all M. aeruginosa displays a large genomic plasticity, which is characterized by a high proportion of repeat sequences and by low synteny values between the strains. Finally, we identified 13 secondary metabolite gene clusters, including three new putative clusters. When comparing the genomes of Microcystis and Prochlorococcus, one of the dominant picocyanobacteria living in marine ecosystems, our findings show that they are characterized by having almost opposite evolutionary strategies, both of which have led to ecological success in their respective environments. 相似文献