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排序方式: 共有197条查询结果,搜索用时 15 毫秒
1.
J. Y. Barbeau R. Marchal J. P. Vandecasteele 《Applied microbiology and biotechnology》1988,29(5):447-455
Summary The stability of solvent production by Clostridium acetobutylicum has been studied in continuous single-stage and two-stage fermentations. At low dilution rates, metabolic oscillations resulting from product inhibition have been observed especially in the case of fermentations controlled by product accumulation. A second type of instability also observed in product-controlled fermentations, but not in fermentations controlled by nitrogen limitation, was a long-term metabolic drift towards acid production. This acid drift has been shown to be identical to the phenomenon of culture degeneration occurring upon subculturing in batch fermentation. In addition, it was found that acid drift could be reversed by decreases in pH, temperature and dilution rate, by growth limitation in nitrogen-deficient conditions and by the addition of butyric and acetic acids. The existence of two distinct mechanisms, a short-term control (shift) and a long-term control (drift), both triggered by the same physiological conditions, is proposed in the regulation of acid and solvent production. 相似文献
2.
Isolation and characterization of butanol-resistant mutants of Clostridium acetobutylicum. 总被引:2,自引:1,他引:1 下载免费PDF全文
M Hermann F Fayolle R Marchal L Podvin M Sebald J P Vandecasteele 《Applied microbiology》1985,50(5):1238-1243
In a wild-type strain of Clostridium acetobutylicum isolated from soil, solvent production appeared limited by butanol toxicity. Butanol-resistant mutants have been obtained which produced significantly higher solvent concentrations (about 30%) than the wild-type strain. Some other physiological differences were observed between a selected resistant mutant and the wild-type strain at the level of solvent resistance and sporulation. 相似文献
3.
Versieck Jacques Vanballenberghe Lidia Wittoek Ann Vermeir Gerda Vandecasteele Carlo 《Biological trace element research》1990,(1):683-689
A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation
analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the
method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of
serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same
samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as
well as the figures determined in a “second-generation” biological reference material (freeze-dried human serum), prepared
and conditioned at the University of Ghent. 相似文献
4.
The microbiological fate of polycyclic aromatic hydrocarbons: carbon and oxygen balances for bacterial degradation of model compounds 总被引:3,自引:0,他引:3
M. Bouchez D. Blanchet J. -P. Vandecasteele 《Applied microbiology and biotechnology》1996,45(4):556-561
A series of pure bacterial strains belonging mainly to theRhodococcus andPseudomonas genera were grown on one of the following polycyclic aromatic hydrocarbons (PAH) supplied as sole carbon and energy source: naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. In each case, a quantitative evaluation of the carbon repartition of the PAH degraded into CO2, biomass and water-soluble metabolites was carried out. In addition, the kinetics of oxygen consumption and of water-soluble metabolite accumulation during PAH biodegradation was followed with respirometric equipment. Satisfactory carbon balances were obtained and the data correlated well with oxygen consumption values. The results show that growth on PAH presents high mineralization yields (from 56% to 77% of carbon) and sizeable production of biomass (from 16% to 35% of carbon) and limited but significant accumulation of metabolites (from 5% to 23% of carbon). The mineralization yields were higher and biomass yields lower in the case of higher PAH. Some differences between strains were also observed. 相似文献
5.
R. W. Mayes N. A. Beresford B. J. Howard C. M. Vandecasteele G. Stakelum 《Radiation and environmental biophysics》1996,35(2):101-109
Limitations of existing methods to describe the bioavailability of dietary radionuclides to ruminants (the transfer coefficient
and apparent absorption coefficient) have led to the alternative suggestion of using the true absorption coefficient (A
t). Various approaches to estimatingA
t for radiocaesium, involving the intravenous administration of a second isotope, are presented and discussed with reference
to results from studies in which a range of radiocaesium sources were examined in sheep. Although estimates ofA
t differed between the sources, they were reasonably consistent between measurement techniques. Those methods which involved
the estimation of endogenous faecal excretion of radiocaesium could be used with previously contaminated animals and did not
require continuous administrations of radiocaesium isotopes, but gave unreliable results for sources of low bioavailability.
Methods based on estimating the turnover rate of dietary radiocaesium through blood plasma were sufficiently sensitive to
measureA
t for the range of sources studied. However, they require previously uncontaminated animals and continuous administration of
both isotopes for approximately 7 days. Bioavailability is more effectively measured asA
t than as the transfer or apparent absorption coefficients sinceA
t does not incorporate factors relating to the metabolism of radiocaesium in the tissues of the animal. The results of these
studies show that differences in transfer coefficients between sheep and cattle and between sheep of differing ages are not
due to variation in absorption across the gut. The potential for applying these approaches to other radioactive elements is
discussed. 相似文献
6.
Davila Anne-Marie Marchal Rémy Vandecasteele Jean-Paul 《Journal of industrial microbiology & biotechnology》1994,13(4):249-257
Summary Sophorose lipids stand out as biosurfactants with a wide potential for industrial application and which can be produced in good yield from glucose and a lipidic cosubstrate.Candida bombicola CBS 6009 (ATCC 22214) was used in the present study. The influence of the lipidic cosubstrate on various aspects of production performance of these glycolipids (final concentration, yield) and on product composition (in particular, the structure of the hydroxy fatty acid vegetable and animal oils, markedly influenced product composition. In terms of production performance, the best substrates were oils or esters rich in C18:0 and C18:1 fatty acids. Optimal overall performance was obtained with esters (340 g L–1 sophorose lipids with rapeseed esters). Conclusions drawn from the results allow predictive evaluation of lipidic industrial substrates. 相似文献
7.
8.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
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