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排序方式: 共有117条查询结果,搜索用时 875 毫秒
1.
Abstract Listeriolysin, an SH-activated haemolysin probably involved in Listeria pathogenicity, has been cloned into the cosmid vector pHC79 and was expressed in Escherichia coli HB101 cells. Chromosomal DNA of Listeria monocytogenes serovar 1/2 was partially digested with Mbo I and ligated to the Bam HI cleaved cosmid. From 2000 recombinant clones examined, 12 (0.6%) produced haemolysin in solid and liquid media. All of them contained chromosome fragments of Listeria of about 40 kb. The cloning of the listeriolysin determinant will lead to a better understanding of the basis of Listeria pathogenicity. 相似文献
2.
The purpose of this investigation was to determine whether Madurella mycetomatis, the most frequent agent of eumycotic mycetomas, produces siderophores and synthesizes new outer membrane proteins under iron-starvation conditions. Siderophore production, only of the hydroxamate type, was demonstrated in all nine strains tested. It was regulated by extracellular iron concentrations. Under iron-restricted conditions, M. mycetomatis expressed various outer membrane iron-regulated proteins, particularly of 24-kilodalton, that may participate in iron metabolism. 相似文献
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Alexander R. Gaos Rebecca L. Lewison Michael J. Liles Velkiss Gadea Eduardo Altamirano Ana V. Henríquez Perla Torres José Urteaga Felipe Vallejo Andres Baquero Carolina LeMarie Juan Pablo Mu?oz Jaime A. Chaves Catherine E. Hart Alejandro Pe?a de Niz Didiher Chácon Luis Fonseca Sarah Otterstrom Ingrid L. Ya?ez Erin L. LaCasella Amy Frey Michael P. Jensen Peter H. Dutton 《Ecology and evolution》2016,6(4):1251-1264
Prior to 2008 and the discovery of several important hawksbill turtle (Eretmochelys imbricata) nesting colonies in the EP (Eastern Pacific), the species was considered virtually absent from the region. Research since that time has yielded new insights into EP hawksbills, salient among them being the use of mangrove estuaries for nesting. These recent revelations have raised interest in the genetic characterization of hawksbills in the EP, studies of which have remained lacking to date. Between 2008 and 2014, we collected tissue samples from 269 nesting hawksbills at nine rookeries across the EP and used mitochondrial DNA sequences (766 bp) to generate the first genetic characterization of rookeries in the region. Our results inform genetic diversity, population differentiation, and phylogeography of the species. Hawksbills in the EP demonstrate low genetic diversity: We identified a total of only seven haplotypes across the region, including five new and two previously identified nesting haplotypes (pooled frequencies of 58.4% and 41.6%, respectively), the former only evident in Central American rookeries. Despite low genetic diversity, we found strong stock structure between the four principal rookeries, suggesting the existence of multiple populations and warranting their recognition as distinct management units. Furthermore, haplotypes EiIP106 and EiIP108 are unique to hawksbills that nest in mangrove estuaries, a behavior found only in hawksbills along Pacific Central America. The detected genetic differentiation supports the existence of a novel mangrove estuary “reproductive ecotype” that may warrant additional conservation attention. From a phylogeographic perspective, our research indicates hawksbills colonized the EP via the Indo‐Pacific, and do not represent relict populations isolated from the Atlantic by the rising of the Panama Isthmus. Low overall genetic diversity in the EP is likely the combined result of few rookeries, extremely small reproductive populations and evolutionarily recent colonization events. Additional research with larger sample sizes and variable markers will help further genetic understanding of hawksbill turtles in the EP. 相似文献
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We have recently described the presence of a high proportion of Pseudomonas aeruginosa isolates (20%) with an increased mutation frequency (mutators) in the lungs of cystic fibrosis (CF) patients. In four out of 11 independent P. aeruginosa strains, the high mutation frequency was found to be complemented with the wild-type mutS gene from P. aeruginosa PAO1. Here, we report the cloning and sequencing of two additional P. aeruginosa mismatch repair genes and the characterization, by complementation of deficient strains, of these two putative P. aeruginosa mismatch repair genes (mutL and uvrD). We also describe the alterations in the mutS, mutL and uvrD genes responsible for the mutator phenotype of hypermutable P. aeruginosa strains isolated from CF patients. Seven out of the 11 mutator strains were found to be defective in the MMR system (four mutS, two mutL and one uvrD). In four cases (three mutS and one mutL), the genes contained frameshift mutations. The fourth mutS strain showed a 3.3 kb insertion after the 10th nucleotide of the mutS gene, and a 54 nucleotide deletion between two eight nucleotide direct repeats. This deletion, involving domain II of MutS, was found to be the main one responsible for mutS inactivation. The second mutL strain presented a K310M mutation, equivalent to K307 in Escherichia coli MutL, a residue known to be essential for its ATPase activity. Finally, the uvrD strain had three amino acid substitutions within the conserved ATP binding site of the deduced UvrD polypeptide, showing defective mismatch repair activity. Interestingly, cells carrying this mutant allele exhibited a fully active UvrABC-mediated excision repair. The results shown here indicate that the putative P. aeruginosa mutS, mutL and uvrD genes are mutator genes and that their alteration results in a mutator phenotype. 相似文献
7.
Comparative study of microbiological and histopathological techniques used for the detection of Helicobacter pylori 总被引:3,自引:0,他引:3
Muñoz E Corcuera MT Roldán M Gómez F Picazo A Baquero M Alonso MJ 《European journal of histochemistry : EJH》1998,42(4):297-302
This study evaluates the sensitivity, specificity and predictive values of several techniques commonly used for the detection of Helicobacter pylori in an analysis of 105 biopsy specimens (gastric and duodenal). For comparative purposes, the techniques investigated were divided into 2 groups: histopathological and microbiological. The former included hematoxylin-eosin and Giemsa stains, a Gram stain modified for use in tissue, and immunohistochemical techniques. Microbiological analysis was performed using culture, the urease test and the conventional Gram stain. The immunohistochemical techniques proved to be the most sensitive (93%). The modified Gram stain was sufficiently sensitive (92%) and specific (97%) for the detection of the bacterium. When combined with a microbiological technique such as the urease test, this stain showed increased sensitivity (96%) but its specificity was reduced to 94%. This combination of tests is recommended for the detection of H. pylori in biopsy specimens since it is easily performed at low cost and gives excellent results. For economical reasons, it is suggested that the use of immunohistochemical techniques should be restricted to specific cases. 相似文献
8.
Ana P. Tedim Patricia Ruiz-Garbajosa Jukka Corander Concepción M. Rodríguez Rafael Cantón Rob J. Willems Fernando Baquero Teresa M. Coque 《Applied and environmental microbiology》2015,81(5):1820-1831
The diversity of enterococcal populations from fecal samples from hospitalized (n = 133) and nonhospitalized individuals (n = 173) of different age groups (group I, ages 0 to 19 years; group II, ages 20 to 59 years; group III, ages ≥60 years) was analyzed. Enterococci were recovered at similar rates from hospitalized and nonhospitalized persons (77.44% to 79.77%) of all age groups (75.0% to 82.61%). Enterococcus faecalis and Enterococcus faecium were predominant, although seven other Enterococcus species were identified. E. faecalis and E. faecium (including ampicillin-resistant E. faecium) colonization rates in nonhospitalized persons were age independent. For inpatients, E. faecalis colonization rates were age independent, but E. faecium colonization rates (particularly the rates of ampicillin-resistant E. faecium colonization) significantly increased with age. The population structure of E. faecium and E. faecalis was determined by superimposing goeBURST and Bayesian analysis of the population structure (BAPS). Most E. faecium sequence types (STs; 150 isolates belonging to 75 STs) were linked to BAPS groups 1 (22.0%), 2 (31.3%), and 3 (36.7%). A positive association between hospital isolates and BAPS subgroups 2.1a and 3.3a (which included major ampicillin-resistant E. faecium human lineages) and between community-based ampicillin-resistant E. faecium isolates and BAPS subgroups 1.2 and 3.3b was found. Most E. faecalis isolates (130 isolates belonging to 58 STs) were grouped into 3 BAPS groups, BAPS groups 1 (36.9%), 2 (40.0%), and 3 (23.1%), with each one comprising widespread lineages. No positive associations with age or hospitalization were established. The diversity and dynamics of enterococcal populations in the fecal microbiota of healthy humans are largely unexplored, with the available knowledge being fragmented and contradictory. The study offers a novel and comprehensive analysis of enterococcal population landscapes and suggests that E. faecium populations from hospitalized patients and from community-based individuals differ, with a predominance of certain clonal lineages, often in association with elderly individuals, occurring in the hospital setting. 相似文献
9.
Heat shock protein 90 (HSP90) is a conserved molecular chaperone that functions as part of complexes in which different client
proteins target it to diverse sets of substrates. In this paper, HSP90 complexes were investigated in γ-proteobacteria from
mild (Shewanella oneidensis) and cold environments (Shewanella frigidimarina and Psychrobacter frigidicola), to determine changes in HSP90 interactions with client proteins in response to the adaptation to cold environments. HSP90
participation in cold adaptation was determined using the specific inhibitor 17-allylamino-geldanamycin. Then, HSP90 was immunoprecipitated
from bacterial cultures, and the proteins in HSP90 complexes were analyzed by two-dimensional gel electrophoresis and identified
by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. According to HSP90-associated protein analysis,
only 15 common proteins were found in both species from the same genus, S. oneidensis and S. frigidimarina, whereas a significant higher number of common proteins were found in both psychrophilic species S. frigidimarina and P. frigidicola 21 (p < 0.001). Only two HSP90-interacting proteins, the chaperone proteins DnaK and GroEL, were common to the three species. Interestingly,
some proteins related to energy metabolism (isocitrate lyase, succinyl-CoA synthetase, alcohol dehydrogenase, NAD(+) synthase,
and malate dehydrogenase) and some translation factors only interacted with HSP90 in psychrophilic bacteria. We can conclude
that HSP90 and HSP90-associated proteins might take part in the mechanism of adaptation to cold environments, and interestingly,
organisms living in similar environments conserve similar potential HSP90 interactors in opposition to phylogenetically closely
related organisms of the same genus but from different environments. 相似文献
10.
Goi G Massaccesi L Burlina AP Baquero Herrera CJ Lombardo A Tettamanti G Burlina AB 《Biochimica et biophysica acta》2005,1741(3):300-306
OBJECTIVE: Fabry disease results from a deficiency in the activity of alpha-d-galactosidase A and subsequent accumulation of neutral glycosphingolipids in lysosomes. This study investigated whether lysosomal enzymes can indicate biochemical changes in the lysosomal apparatus induced by enzyme replacement therapy (ERT). DESIGN AND METHODS: Eight patients were monitored by clinical and biochemical tests and several lysosomal glycohydrolases were measured in plasma and leucocytes. RESULTS: Before starting ERT, beta-d-glucuronidase in leukocytes was markedly increased. After 1 month of therapy, enzyme levels dropped in all patients. In the patients who regularly followed the therapy, the enzyme levels remained stable for the next 20 months. In one patient who interrupted therapy for 2 months, the enzyme levels rose again. CONCLUSIONS: Lysosomal enzymes can be useful for monitoring biochemical changes in patients with Fabry disease receiving ERT. Though these findings refer to only a small number of patients, the correlation between beta-d-glucuronidase levels and ERT is interesting and might serve as a basis for further studies to define the potential of this enzyme in monitoring the effects of ERT in lysosomal storage disorders. 相似文献