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1.
WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF
colonization factor
- CFA
Colonization Factor Antigen
- CS
coli-surface-associated antigen
- EAggEC
enteroaggregativeE. coli
- ECDD
E. coli diarrheal disease
- EHEC
enterohemorrhagicE. coli
- EIEC
enteroinvasiveE. coli
- EPEC
enteropathogenicE. coli
- ETEC
enterotoxigenicE. coli
- Gal
galactose
- GalNAc
N-acetyl galactosamine
- LT
heat-labile toxin
- NeuAc
N-acetyl neuraminic acid
- PCF
Putative colonization factor
- RBC
red blood cells
- SLT
Shiga-like toxin
- ST
heat-stable toxin 相似文献
2.
Summary Strain Bacillus subtilis MS was constructed with 12–22 fold increase of -amylase production, caused by presence of multiple -amylase gene copies in the chromosome of industrial strain Bacillus subtilis CCM2722, as demonstrated by DNA hybridization. The enhanced production is a result of multiple integration of plasmid pTVA1, carrying a temperature sensitive origin of replication from pE194, and containing the -amylase gene and a modified transposon Tn917. 相似文献
3.
Esterase zymograms were obtained following polyacrylamide slab gel electrophoresis of protein extractsFusarium sambucinum and related species originating from different geographic locations and different matrices. The sites of esterase activity were recorded, and the Rfs were calculated. The data were used for the construction of phenograms by cluster analysis and nonlinear mapping by computerized classification techniques. The fifteen isolates ofF. sambucinum, the eight isolates ofF. torulosum and the six isolates ofF. spec. nov. each had identical profiles, and are therefore electrophoretically distinct species. The isolates ofF. sarcochroum, one ofF. sambucinum sensu lato (BBA 64280) and fifteen isolates ofF. sambucinum were electrophoretically indistinguishable from each other. We assume they are synonymous. The isolate ofF. bactridioides, one ofF. sambucinum sensu lato (BBA 64993) and eight isolates ofF. torulosum had uniform EST patterns, therefore the two species are electrophoretically identical. We assume they are also synonymous. The remaining three isolates ofF. sambucinum sensu lato are somewhat closely related toF. sambucinum isolates on the basis of our investigations. 相似文献
4.
Dr. Jan Tur 《Development genes and evolution》1908,25(4):615-631
Résumé L'auteur décrit un blastoderme du Corbeau freux (Krähe —Corvus frugilegus L.), ayant 3,33 mm. en diamètre seulement et dépourvu des traces quelconques du corps de l'embryon. Malgré ses dimensions si réduites, ce germe anidien possédait une aire vasculaire très fortement prononcée, mais constituée d'une faÇon singulière, qui n'était jusqu'ici jamais signalée. Les formations vasculaires rayonnaient du centre du blastoderme vers sa périphérie, sous la forme des forts cordons.L'examen des coupes sériées a montré, que ce blastoderme était constitué exclusivement du parablaste et des cordons vasculaires, formés au dépens de celui-ci. L'éctoderme et le mésoderme faisaient absolument défaut; nulle trace du foyer gastruléen. Néanmoins ce germe était bien vivant au moment de la fixation, ce qui est prouvé par l'abondance des figures caryocinétiques.L'auteur considère cette forme nouvelle de l'anidie embryonnaire comme une preuve décisive, que les éléments entodermo-parablastiques peuvent fournir les formations vasculaires sans concours du mésoderme gastruléen.
Zusammenfassung Der Autor beschreibt eine Keimhaut der Krähe, welche jede Spur eines Embryos entbehrte. Ungeachtet seiner geringen Ausdehnung von nur 3.33 mm besaß dieser Keim einen sehr ausgebildeten Gefäßhof, welcher eine bisher nicht beschriebene Gestaltung zeigte. Die Gefäßbildungen gingen vom Centrum der Keimhaut gegen die Peripherie und zwar in der Form dicker Stränge. Die Schnittserien zeigten, daß die Keimhaut ausschließlich vom Parablast gebildet war und die Gefäßstränge desgleichen. Ectoderm und Mesoderm fehlten durchaus, keine Spur von Gastrulation. Nichtsdestoweniger war der Keim bei der Fixation noch in lebendem Zustand, wie sich aus reichlich vorhandenen Kernteilungsfiguren ergibt.Der Autor betrachtet diese neue Form eines Anideus als einen entscheidenden Beweis, daß die parablastischen Entodermelemente ohne Beteiligung des Mesoderms die Gefäßbildungen produzieren können.Die Anlage und ziemlich weite Ausbildung dieser nicht zur Circulation verwendeten Blutgefäße bestätigt die Auffassung W.Rouxs, daß die Bildung der typischen Blutgefäße zunächst in die erste seiner drei causalen Perioden der Entwicklung, also in die Periode der selbständigen, das heißt, von der Funktionsvollziehung noch unabhängigen Bildung gehört (s.Rouxs Gesammelte Abhandlungen über Entwicklungsmechanik. Bd. I. S. 83 u. 326). Die neue Beobachtung ist ferner eine Beantwortung der vonRoux aufgeworfenen Frage, ob nicht außer dem Sinus terminalis auch andre typische Hauptbahnen des Gefäßhofes ohne Funktionierung angelegt und ausgebildet werden können.相似文献
5.
We examined gazelle peripheral blood leucocytes using the α-Naphthyl acetate esterase (ANAE) staining technique (pH 5.8). Our purpose was to determine the percentage of ANAE positive lymphocytes. The proportion of ANAE positive T-lymphocytes was 72%. T-lymphocytes showed an ANAE positive reaction, but eosinophilic granulocytes and monocytes also showed a positive reaction. By contrast, no reaction was detected in B-lymphocytes, neutrophil granulocytes or platelets. The reaction observed in T-lymphocytes was a red-brown coloration, usually 1–2 granules, but enough granules to fill the cytoplasm were detected rarely. As a result of ANAE enzyme staining, we concluded that the staining technique can be used as a cytochemical marker for gazelle T-lymphocytes. 相似文献
6.
7.
Tellurite containing compounds are in use for industrial processes and increasing delivery into the environment generates specific pollution that may well result in contamination and subsequent potential adverse effects on public health. It was the aim of the current study to reveal mechanism of toxicity in tellurite-sensitive and tellurite-resistant E. coli at the protein level.In this work an approach using gel-based mass spectrometrical analysis to identify a differential protein profile related to tellurite toxicity was used and the mechanism of ter operon-mediated tellurite resistance was addressed.
E. coli BL21 was genetically manipulated for tellurite-resistance by the introduction of the resistance-conferring ter genes on the pLK18 plasmid. Potassium tellurite was added to cultures in order to obtain a final 3.9 micromolar concentration. Proteins from tellurite-sensitive and tellurite-resistant E. coli were run on 2-D gel electrophoresis, spots of interest were picked, in-gel digested and subsequently analysed by nano-LC-MS/MS (ion trap). In addition, Western blotting and measurement of enzymatic activity were performed to verify the expression of certain candidate proteins.Following exposure to tellurite, in contrast to tellurite-resistant bacteria, sensitive cells exhibited increased levels of antioxidant enzymes superoxide dismutases, catalase and oxidoreductase YqhD. Cysteine desulfurase, known to be related to tellurite toxicity as well as proteins involved in protein folding: GroEL, DnaK and EF-Tu were upregulated in sensitive cells. In resistant bacteria, several isoforms of four essential Ter proteins were observed and following tellurite treatment the abovementioned protein levels did not show any significant proteome changes as compared to the sensitive control.The absence of general defense mechanisms against tellurite toxicity in resistant bacteria thus provides further evidence that the four proteins of the ter operon function by a specific mode of action in the mechanism of tellurite resistance probably involving protein cascades from antioxidant and protein folding pathways. 相似文献
8.
9.
Ips amitinus and I. typographus are two serious pests of spruce in Europe, have similar bionomics and are likely to occur and meet on the same host trees. We therefore hypothesized that the two species support similar levels of similar pathogens. To test this hypothesis, we collected mature beetles from three trap trees at each of eight study sites and determined beetle numbers and pathogen infection levels. In total, 938 mature I. amitinus beetles and 3435 of I. typographus were dissected; five pathogens, as well as intestinal nematodes and endoparasitoids, were detected. The neogregarine Mattesia schwenkei is reported here for the first time as a new pathogen in 9.4% of I. amitinus individuals at one site. Average infection levels of most pathogens (Chytridiopsis typographi, Gregarina typographi, Mattesia schwenkei and parasitoids) were significantly higher in I. typographus than in I. amitinus. Metschnikowia typographi was confirmed only in Ips amitinus, while the microsporidium of Nosema typographi occurred only in I. typographus. Within‐season increases in G. typographi infection levels were documented in Ips amitinus. 相似文献
10.