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31.
Strub S van der Ploeg JR Nuss K Wyss C Luginbühl A Steiner A 《FEMS microbiology letters》2007,269(1):48-53
Digital dermatitis is an inflammation of uncertain aetiology in the skin of the foot of cattle. In 2005, a novel microorganism, Guggenheimella bovis, was isolated from the advancing front of digital dermatitis lesions, suggesting a possible role in pathogenesis. In the present study, tissue samples of 20 affected cows were examined by quantitative PCR for G. bovis, treponemes and the total eubacterial load. High numbers of eubacteria and treponemes were found in most lesions, whereas only a few lesions contained Guggenheimella, and only at low concentrations. The results argue against the relevance of G. bovis in the aetiology of digital dermatitis in cattle, but are consistent with a role for treponemes. 相似文献
32.
A model of the ventral visual system based on temporal stability and local memory 总被引:1,自引:0,他引:1
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The cerebral cortex is a remarkably homogeneous structure suggesting a rather generic computational machinery. Indeed, under a variety of conditions, functions attributed to specialized areas can be supported by other regions. However, a host of studies have laid out an ever more detailed map of functional cortical areas. This leaves us with the puzzle of whether different cortical areas are intrinsically specialized, or whether they differ mostly by their position in the processing hierarchy and their inputs but apply the same computational principles. Here we show that the computational principle of optimal stability of sensory representations combined with local memory gives rise to a hierarchy of processing stages resembling the ventral visual pathway when it is exposed to continuous natural stimuli. Early processing stages show receptive fields similar to those observed in the primary visual cortex. Subsequent stages are selective for increasingly complex configurations of local features, as observed in higher visual areas. The last stage of the model displays place fields as observed in entorhinal cortex and hippocampus. The results suggest that functionally heterogeneous cortical areas can be generated by only a few computational principles and highlight the importance of the variability of the input signals in forming functional specialization. 相似文献
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34.
A novel reactive perstraction system based on liquid-core microcapsules applied to lipase-catalyzed biotransformations 总被引:1,自引:0,他引:1
A novel reactive perstraction system has been developed based on liquid-core capsules, involving an enzyme-catalyzed reaction coupled with simultaneous in situ product recovery. Lipase-catalyzed reactions, hydrolysis of triprionin and nitrophenyl laurate, were selected to test the system and demonstrate the feasibility of immobilization of enzymes to the membranes of liquid-core capsules and the ability to extract hydrophobic products of the reaction within the capsule core. The lipase from Candida rugosa was immobilized to the microcapsules by adsorption and by covalent binding through activation with glutaraldehyde. In both cases improved temperature and operational stability were achieved. Both types of immobilization resulted in a basic shift of the pH optimum for activity, from 7.5 to 9.0. The presence of an organic phase within the capsule core allowed direct product separation and lead to a decrease in product inhibition of the lipase-catalyzed reaction. 相似文献
35.
Increasing evidence indicates that the progression of calcific aortic valve disease (CAVD) is influenced by the mechanical forces experienced by valvular interstitial cells (VICs) embedded within the valve matrix. The ability of VICs to sense and respond to tissue-level mechanical stimuli depends in part on cellular-level biomechanical properties, which may change with disease. In this study, we used micropipette aspiration to measure the instantaneous elastic modulus of normal VICs and of VICs induced to undergo pathological differentiation in vitro to osteoblast or myofibroblast lineages on compliant and stiff collagen gels, respectively. We found that VIC elastic modulus increased after subculturing on stiff tissue culture-treated polystyrene and with pathological differentiation on the collagen gels. Fibroblast, osteoblast, and myofibroblast VICs had distinct cellular-level elastic properties that were not fully explained by substrate stiffness, but were correlated with α-smooth muscle actin expression levels. C-type natriuretic peptide, a peptide expressed in aortic valves in vivo, prevented VIC stiffening in vitro, consistent with its ability to inhibit α-smooth muscle actin expression and VIC pathological differentiation. These data demonstrate that VIC phenotypic plasticity and mechanical adaptability are linked and regulated both biomechanically and biochemically, with the potential to influence the progression of CAVD. 相似文献
36.
Daniele Kasper Elisabete Fernandes Albuquerque Palermo Christina Wyss Castelo Branco Olaf Malm 《Hydrobiologia》2012,694(1):87-98
Hydroelectric reservoirs can stratify, producing favorable conditions for mercury methylation in the hypolimnion. The methylmercury (MeHg) can be exported downstream, increasing its bioavailability below the dam. Our objective was to assess the mercury levels in plankton, suspended particulate matter (SPM) and fish collected upstream (UP) and downstream (DW) from the Reservatório de Samuel dam, an Amazonian reservoir that stratifies during half of the year. Mercury concentrations in both SPM and plankton were similar between the two sites, which could indicate there are no conditions favoring methylation at the moment of sampling (absence of stratification). Almost all mercury found in the muscle of fishes was in organic form, and differences of mercury levels between sites were dependent on the fishes trophic level. Herbivores showed similar mean organic mercury levels (UP = 117 μg g?1; DW = 120 μg g?1; n = 12), whereas omnivores (UP = 142 μg g?1; DW = 534 μg g?1; n = 27) and carnivores (UP = 545 μg g?1; DW = 1,366 μg g?1; n = 69) showed significantly higher values below the dam. The absence of a reservoir effect in herbivores is expected, since they feed on grassy vegetation, near the riverbanks, which is not much influenced by mercury in aquatic systems. On the other hand, the higher mercury levels below the dam observed for omnivores and carnivores suggest a possible influence of the reservoir since they feed on items that could be contaminated by MeHg exported from upstream. The results highlight the necessity of assessing areas downstream of reservoirs. 相似文献
37.
Granado J Thürig B Kieffer E Petrini L Fliessbach A Tamm L Weibel FP Wyss GS 《Microbial ecology》2008,56(4):720-732
The effects of organic and integrated production systems on the culturable fungal microflora of stored apple fruits from five
matched pairs of certified organic and integrated ‘Golden Delicious’ farms were studied at five representative production
sites in Switzerland. Isolated fungi were identified morphologically. Colonization frequency (percentage of apples colonized),
abundance (colony numbers), and diversity (taxon richness) were assessed for each orchard. The standard quality of the stored
fruits was comparable for both organic and integrated apples and complied with national food hygiene standards. Yeasts (six
taxa) and the yeast-like fungus Aureobasidium pullulans were the dominant epiphytes, filamentous fungi (21 taxa) the dominant endophytes. The most common fungi occurred at all sites
and belonged to the “white” and “pink” yeasts, yeast-like A. pullulans, filamentous fungi Cladosporium spp., Alternaria spp., and sterile filamentous fungi. Canonical correspondence analysis of the total fungal community revealed a clear differentiation
among production systems and sites. Compared to integrated apples, organic apples had significantly higher frequencies of
filamentous fungi, abundance of total fungi, and taxon diversity. The effects of the production system on the fungal microflora
are most likely due to the different plant protection strategies. The incidence of potential mycotoxin producers such as Penicillium and Alternaria species was not different between production systems. We suggest that higher fungal diversity may generally be associated
with organic production and may increase the level of beneficial and antagonistically acting species known for their potential
to suppress apple pathogens, which may be an advantage to organic apples, e.g., in respect to natural disease control. 相似文献
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39.
C. Wyss 《Experimental cell research》1980,125(1):121-126
Three independently established Drosophila cell lines, Schneider's line 3 (S3), Dübendorfer's line 1 (D1) and MDR3, an adenine salvage deficient clone of the Kc line, all cease to proliferate in the presence of ecdysterone. This is also observed with hybrids between S3 and MDR3 and between D1 and MDR3. It is shown that cells derived directly from wild-type Drosophila embryos can be hybridized with MDR3. Of nine such hybrids all proved to be able to proliferate in the presence of ecdysterone. 相似文献
40.