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61.
We have investigated the production of proteinase and phospholipase by 20 different isolates of Paracoccidioides brasiliensis. Isolates were grown in Bacto-peptone, Dextrose, pH 5.5, agar slants, at 27 °C for 30 days, and cultures were transferred
onto Petri dishes containing basis medium and bovine serum albumin fraction V and sterile egg yolk as substrates for enzyme
production, and incubated at 27 °C. After 30 days net enzyme activity was visualized and quantitavely evaluated, measuring
a ratio between colony diameter and diameter of the transparent (proteinase) or white (phospholipase) ring zone surrounding
it. Results demonstrated that all isolates had the ability to produce proteinase and phospholipase, even though variability
in enzyme production was noted among different isolates of P. brasiliensis.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
62.
Bianca Braha Herbert Tintemann Gudrun Krauss Jim Ehrman Felix Bärlocher Gerd-Joachim Krauss 《Biometals》2007,20(1):93-105
Biochemical responses to cadmium (Cd2+) and copper (Cu2+) exposure were compared in two strains of the aquatic hyphomycete (AQH) Heliscus lugdunensis. One strain (H4-2-4) had been isolated from a heavy metal polluted site, the other (H8-2-1) from a moderately polluted habitat.
Conidia of the two strains differed in shape and size. Intracellular accumulation of Cd2+ and Cu2+ was lower in H4-2-4 than in H8-2-1. Both␣strains synthesized significantly more glutathione (GSH), cysteine (Cys) and γ-glutamylcysteine
(γ-EC) in the presence of 25 and 50 μM Cd2+, but quantities and rates of synthesis were different. In H4-2-4, exposure to 50 μM Cd2+ increased GSH levels to 262% of the control; in H8-2-1 it increased to 156%. Mycelia of the two strains were analysed for
peroxidase, dehydroascorbate reductase, glutathione reductase and glucose-6-phosphate dehydrogenase. With Cd2+ exposure, peroxidase activity increased in both strains. Cu2+ stress increased dehydroascorbate reductase activity in H4-2-4 but not in H8-2-1. Dehydroascorbate reductase and glucose-6-phosphate
dehydrogenase activities progressively declined in the presence of Cd2+, indicating a correlation with Cd2+ accumulation in both strains. Cd2+ and Cu2+ exposure decreased glutathione reductase activity. 相似文献
63.
This study assessed the effect of nutrient enrichment on organic matter breakdown in an alpine springbrook, using alder leaf
packs to which phosphorus and nitrogen were added in the form of slow-release fertilizer briquettes. The breakdown of leaf
packs with nutrients added (k=0.0284 day–1) was significantly faster than that of unfertilized packs (k=0.0137 day–1), resulting in a 30% higher mass loss after 42 days. Unfertilized leaves enclosed in fine-mesh bags broke down at an even
slower rate (k=0.0062 day–1). Phosphorus and nitrogen concentrations were initially higher in leaf packs with nutrients added, but this difference disappeared
within 3 weeks. Fungal biomass developing in decomposing leaves was substantial (c. 55 mg dry mass per 1 g leaf dry mass) although similar between fertilized and unfertilized packs, as was the sporulation activity of aquatic hyphomycetes.
There was a significantly greater number and higher biomass of macroinvertebrates (shredding nemourid stoneflies in particular)
on the fertilized packs, suggesting that the increased leaf mass loss was brought about by shredder feeding.
Received: 11 March 1999 / Accepted: 6 September 1999 相似文献
64.
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66.
The survival of naked and clay-coated Beauveria blastospores in soil was investigated with an experimental biodegradation method using a trap technique. At various times of incubation, traps were collected to study changes in biomass, inoculum potential, and infection potential of degraded blastospores, and to investigate the colonization of blastospore biomass by antagonistic soil-borne microorganisms. Infection potential was tested on larvae of Plutella maculipennis and Leptinotarsa decemlineata. Naked blastospores were inactivated after 3 weeks incubation, while clay-coated blastospores were still active after 2 months incubation in soil at 20°C. All investigations demonstrated the protective role of clay coating against biodegradation of fungal propagules by soil bacteria and protozoa. Consequently, clay coating of blastospores is proposed for the formulation of entomopathogenic hyphomycetes propagules. Moreover, antagonists implicated in lysis of blastospores, must be considered as an important part of the environmental response to a massive introduction of a fungus used for insect control. 相似文献
67.
Syed Hussain Iqbal 《Mycoscience》1994,35(4):331-343
Freshwater hyphomycete communities in four streams were sampled by filtration of water samples, trapping conidia in artificial foam, and examination of alder leaf pack baits and random sampling of naturally occurring submerged leaves. No two communities of freshwater hyphomycetes detected by different sampling techniques used singly in a stream showed 100% similarity. Based on relative frequency values, the same 10 top-ranking species in a stream were detected by artificial foam trap and on the baited leaves. These species differed in ranking, and the community in artificial foam was riche than on baited leaves. Of the various communities detected by different sampling techniques used singly or in combination, those detected by artificial foam trap or a combination of this technique with leaf baiting or with leaf baiting and randomly sampled leaves or filtration showed the highest similarity to the total community based on data generated using four sampling techniques simultaneously.This work was conducted under Grant No. PSF Project Environment 3 from the Pakistan Science Foundation. 相似文献
68.
Relationships between physico-chemical factors of waters, riparian vegetation, altitude and species richness of the hyphomycete communities in six rivers and a sulfur spring in the Western Ghats of Karnataka were analysed statistically. Linear regression and correlation between log fungal species and riparian vegetation was highly significant. The similarity in the fungal diversity between different rivers and the sulphur spring was evaluated by Sorensen's index. Generally, the indices of similarity in the mycoflora between the streams were high. However, in the streams of Lakya, Bhadra, Ranganathittu bird sanctuary and the sulfur spring the indices of similarity were low compared with the rest of the water systems. The low pH, low oxygen concentration, hardness, high iron, high temperature and sulfide contents of the waters of these streams are thought to be the reasons for the differences in these streams. Anguillospora longissima, Helicomyces roseus, Lunulospora curvula, Triscelophorus monosporus and Wiesneriomyces laurinus were found to be the most abundant species. 相似文献
69.
We assessed the effect of whole-stream nitrate enrichment on decomposition of three substrates differing in nutrient quality
(alder and oak leaves and balsa veneers) and associated fungi and invertebrates. During the 3-month nitrate enrichment of
a headwater stream in central Portugal, litter was incubated in the reference site (mean NO3-N 82 μg l−1) and four enriched sites along the nitrate gradient (214–983 μg NO3-N l−1). A similar decomposition experiment was also carried out in the same sites at ambient nutrient conditions the following
year (33–104 μg NO3-N l−1). Decomposition rates and sporulation of aquatic hyphomycetes associated with litter were determined in both experiments,
whereas N and P content of litter, associated fungal biomass and invertebrates were followed only during the nitrate addition
experiment. Nitrate enrichment stimulated decomposition of oak leaves and balsa veneers, fungal biomass accrual on alder leaves
and balsa veneers and sporulation of aquatic hyphomycetes on all substrates. Nitrate concentration in stream water showed
a strong asymptotic relationship (Michaelis–Menten-type saturation model) with temperature-adjusted decomposition rates and
percentage initial litter mass converted into aquatic hyphomycete conidia for all substrates. Fungal communities did not differ
significantly among sites but some species showed substrate preferences. Nevertheless, certain species were sensitive to nitrogen
concentration in water by increasing or decreasing their sporulation rate accordingly. N and P content of litter and abundances
or richness of litter-associated invertebrates were not affected by nitrate addition. It appears that microbial nitrogen demands
can be met at relatively low levels of dissolved nitrate, suggesting that even minor increases in nitrogen in streams due
to, e.g., anthropogenic eutrophication may lead to significant shifts in microbial dynamics and ecosystem functioning.
Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
70.
Stimulation of leaf litter decomposition and associated fungi and invertebrates by moderate eutrophication: implications for stream assessment 总被引:5,自引:1,他引:4
1. We investigated the effect of moderate eutrophication on leaf litter decomposition and associated invertebrates in five reference and five eutrophied streams in central Portugal. Fungal parameters and litter N and P dynamics were followed in one pair of streams. Benthic invertebrate parameters that are considered useful in bioassessment were estimated in all streams. Finally, we evaluated the utility of decomposition as a tool to assess stream ecosystem functional integrity. 2. Decomposition of alder and oak leaves in coarse mesh bags was on average 2.3–2.7× faster in eutrophied than in reference streams. This was attributed to stimulation of fungal activity (fungal biomass accrual and sporulation of aquatic hyphomycetes) by dissolved nutrients. These effects were more pronounced for oak litter (lower quality substrate) than alder. N content of leaf litter did not differ between stream types, while P accrual was higher in the eutrophied than in the reference stream. Total invertebrate abundances and richness associated with oak litter, but not with alder, were higher in eutrophied streams. 3. We found only positive correlations between stream nutrients (DIN and SRP) and leaf litter decomposition rates in both fine and coarse mesh bags, associated sporulation rates of aquatic hyphomycetes and, in some cases, total invertebrate abundances and richness. 4. Some metrics based on benthic invertebrate community data (e.g. % shredders, % shredder taxa) were significantly lower in eutrophied than in reference streams, whereas the IBMWP index that is specifically designed for the Iberian peninsula classified all 10 streams in the highest possible class as having ‘very good’ ecological conditions. 5. Leaf litter decomposition was sufficiently sensitive to respond to low levels of eutrophication and could be a useful functional measure to complement assessment programmes based on structural parameters. 相似文献