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排序方式: 共有95条查询结果,搜索用时 15 毫秒
71.
Elisangela F Silva Mariana Orsi ?ngela L Andrade Rosana Z Domingues Breno M Silva Helena RC de Araújo Paulo FP Pimenta Michael S Diamond Eliseu SO Rocha Erna G Kroon Luiz CC Malaquias Luiz FL Coelho 《Journal of nanobiotechnology》2012,10(1):1-5
Background
Dengue is a major public health problem worldwide, especially in the tropical and subtropical regions of the world. Infection with a single Dengue virus (DENV) serotype causes a mild, self-limiting febrile illness called dengue fever. However, a subset of patients experiencing secondary infection with a different serotype progresses to the severe form of the disease, dengue hemorrhagic fever/dengue shock syndrome. Currently, there are no licensed vaccines or antiviral drugs to prevent or treat dengue infections. Biodegradable nanoparticles coated with proteins represent a promising method for in vivo delivery of vaccines.Findings
Here, we used a murine model to evaluate the IgG production after administration of inactivated DENV corresponding to all four serotypes adsorbed to bovine serum albumin nanoparticles. This formulation induced a production of anti-DENV IgG antibodies (p < 0.001). However, plaque reduction neutralization assays with the four DENV serotypes revealed that these antibodies have no neutralizing activity in the dilutions tested.Conclusions
Our results show that while the nanoparticle system induces humoral responses against DENV, further investigation with different DENV antigens will be required to improve immunogenicity, epitope specicity, and functional activity to make this platform a viable option for DENV vaccines. 相似文献72.
Stability studies were performed on the mono-oxygenase system involved, in particular, in the activation of polynuclear aromatic hydrocarbons (PAHs) present in rat-liver preparations used in the Ames mutagenicity test. The results indicated a good stability of the spectral response of the cytochrome-P-450 system, but a much lower stability of its enzymatic activities measured with various substrates, thus showing the inadequacy of the spectral response to characterize the PAH mono-oxygenase activity of the preparations. Epoxide hydrolase activity was found to be stable. Various mono-oxygenase activities were measured in preparations induced with phenobarbital, 3-methylcholanthrene or Aroclor 1254. The activities of two enzymes, benzo[a]pyrene hydroxylase and ethoxyresorufin-O-dealkylase, were found suitable to characterize the capacity of the preparations to metabolize PAH to mutagens. The efficiency of the same preparations to promote the mutagenicity of benzo[a]pyrene and aflatoxin B1 in the Ames test was determined. There was an excellent general correlation between the efficiencies for mutagenic activation of the preparations and the two enzymatic activities mentioned above. Determination of ethoxyresorufin-O-dealkylase (or benzo[a]pyrene hydroxylase) and benzo[a]pyrene 4,5-oxide hydrolase activities is proposed for characterizing the rat-liver preparations used in the Ames test. 相似文献
73.
Ph. Looten D. Blanchet J. P. Vandecasteele 《Applied microbiology and biotechnology》1987,25(5):419-425
Summary The -fructofuranosidase activities of a strain of Clostridium acetobutylicum, selected for its capacity to grow on inulinic substrates, were investigated. When grown on inulin, this strain produced extracellular and intracellular -fructofuranosidases, both of which hydrolysed inulin (inulinase activity) and sucrose (invertase activity). Inulinase activity was higher than invertase activity in the extracellular preparation, the opposite being observed for the cellular preparation. The effects of pH and temperature, substrate specificity and the kinetic constants for inulin and sucrose were studied on both preparations, as well as induction by inulin and repression by glucose and fructose of inulinase and invertase activities. The overall results were consistent with the existence of a least one inulinase, (EC 3.2.1.7), mainly but not entirely released in the extracellular medium, and an invertase (3.2.1.26) localized within the cell.Time course hydrolysis experiments of dalhia inulin and Jerusalem artichoke inulofructans by extracellular inulinase showed that this preparation had a remarkably high specificity for hydrolysis of long chain inulofructans. 相似文献
74.
Fréderic Monot Emmanuelle Paccard Frédérique Borzeix Marc Bardin Jean-Paul Vandecasteele 《Applied microbiology and biotechnology》1993,39(4-5):483-486
Different modes of conditioning of a crude lipase from Rhizomucor miehei were investigated in terms of activity for synthesis of butyl butyrate either by esterification or transesterification in organic media. It was found that lyophilisation alone had a positive effect on reaction rates and that this effect was greatly enhanced when incorporating the substrates of the reaction prior to lyophilisation.These improvements were no longer observed when adding water to the reaction medium. Removal of the insoluble matter from the crude enzyme had a favourable effect on activity only in biphasic water-organic solvent media.
Correspondence to: F. Monot 相似文献
75.
76.
A.-M. Davila R. Marchal J.-P. Vandecasteele 《Applied microbiology and biotechnology》1997,47(5):496-501
Sophorose lipid production by Candida bombicola is a two-step process where sophorose lipids are mainly produced after a first stage of growth, ending because of nitrogen
limitation. The influence of the following parameters was individually studied for both the stages of growth and of product
formation with respect to final sophorose lipid production performance: pH, temperature and carbon source. Glucose and rapeseed
ethyl esters were supplied individually or as a dual carbon source. The lipidic substrate was added by continuous feeding.
It was found that supplying both carbon sources during the production step was crucial for obtaining a high production performance
ranging from 250 g l−1 to 300 g l−1 or more. Controlling the feeding of rapeseed ethyl esters to avoid inhibition by fatty acids was essential for a successful
scale-up of the fermentation on the industrial scale. The conditions of substrate feeding markedly affected the composition
of the mixture of sophorose lipids produced, namely the extent of acetylation of the sophorose moieties and distribution of
the acidic and lactonic forms. The results suggest that the physiological role of sophorose lipid production is related to
the regulation of energy metabolism.
Received: 26 June 1996 / Received revision: 12 December 1996 / Accepted: 15 December 1996 相似文献
77.
Vandecasteele Carlo Vanhoe Hans Dams Richard Versieck Jacques 《Biological trace element research》1990,(1):553-560
The determination of trace and ultratrace elements in human serum by ICP-MS is described. The accuracy of the method is tested
using a “second generation” human serum reference material. Elements determined include Fe, Co, Cu, Zn, Br, Rb, Sr, Mo, and
Cs. The method is compared to nuclear analytical methods (NAA, PIXE). Perspectives for the future are also discussed. 相似文献
78.
Efficiency of defined strains and of soil consortia in the biodegradation of polycyclic aromatic hydrocarbon (PAH) mixtures 总被引:9,自引:0,他引:9
The microbiological characteristics of the bacterialdegradation of mixtures of five polycyclic aromatichydrocarbons (PAH), phenanthrene, fluorene,anthracene, fluoranthene and pyrene, wereinvestigated. Three pure bacterial strains using oneor several of these PAH as carbon sources wereselected. The interactions between PAH during thedegradation of PAH pairs by each of these strains werestudied and their effects on the kinetics and thebalance of degradation were characterised. Competitionbetween PAH and degradation by cometabolism werefrequently observed. Mixed cultures of two or threestrains, although possessing the global capacity tomineralise the set of five PAH, achieved limiteddegradation of the mixture. In contrast, a consortiumfrom a PAH-contaminated soil readily mineralised thefive-PAH mixture. The results suggested that soilconsortia possessed a wider variety of strains capableto compensate for the competitive inhibition betweenPAH as well as specialised strains that mineralisedpotentially inhibitory PAH metabolites produced bycometabolism. 相似文献
79.
N. A. Beresford C. L. Barnett R. W. Mayes K. Pollaris C. M. Vandecasteele B. J. Howard 《Radiation and environmental biophysics》1995,34(3):191-194
The validity of an in vitro extraction technique to predict the availability for absorption of radiocaesium in the sheep gut has been assessed. The technique (a 2-h extraction with caesium chloride) was found to be valid for sources with a low availability for transfer across the gut, but inappropriate for ionic radiocaesium or radiocaesium incorporated internally within herbage. For such radiocaesium sources, which have a high in vitro availability, no correlation was found between in vitro extraction and true absorption measurements. A true absorption value of 0.80 is recommended for these sources, although values for individual sheep in the range 0.60 to 1.00 should be expected. 相似文献
80.
Leen De Gelder Frederik P. J. Vandecasteele Celeste J. Brown Larry J. Forney Eva M. Top 《Applied microbiology》2005,71(9):5309-5317
Horizontal transfer of multiresistance plasmids in the environment contributes to the growing problem of drug-resistant pathogens. Even though the plasmid host cell is the primary environment in which the plasmid functions, possible effects of the plasmid donor on the range of bacteria to which plasmids spread in microbial communities have not been investigated. In this study we show that the host range of a broad-host-range plasmid within an activated-sludge microbial community was influenced by the donor strain and that various mating conditions and isolation strategies increased the diversity of transconjugants detected. To detect transconjugants, the plasmid pB10 was marked with lacp-rfp, while rfp expression was repressed in the donors by chromosomal lacIq. The phylogeny of 306 transconjugants obtained was determined by analysis of partial 16S rRNA gene sequences. The transconjugants belonged to 15 genera of the α- and γ-Proteobacteria. The phylogenetic diversity of transconjugants obtained in separate matings with donors Pseudomonas putida SM1443, Ralstonia eutropha JMP228, and Sinorhizobium meliloti RM1021 was significantly different. For example, the transconjugants obtained after matings in sludge with S. meliloti RM1021 included eight genera that were not represented among the transconjugants obtained with the other two donors. Our results indicate that the spectrum of hosts to which a promiscuous plasmid transfers in a microbial community can be strongly influenced by the donor from which it transfers. 相似文献