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191.
192.
Survival of Escherichia coli and Campylobacter jejuni in untreated and filtered lake water 总被引:1,自引:0,他引:1
The survival of Campylobacter jejuni and Escherichia coli in lake water was studied using viable counts. Escherichia coli survived better than C. jejuni in all the test conditions studied. Both the species survived better in filtered than in untreated water. This suggests that predation and/or competition for nutrients affect the survival of both the species in an aquatic environment. Campylobacter jejuni survived less well in filtered autoclaved water and in 0.9% NaCl than in filtered water without autoclaving. The lack of some essential nutrients, which may be degraded by autoclaving, might explain these results. 相似文献
193.
The complete mitochondrial DNA sequence of the shark Mustelus manazo: evaluating rooting contradictions to living bony vertebrates 总被引:5,自引:0,他引:5
A remarkable example of a misleading mitochondrial protein tree is
presented, involving ray-finned fishes, coelacanths, lungfishes, and
tetrapods, with sea lampreys as an outgroup. In previous molecular
phylogenetic studies on the origin of tetrapods, ray-finned fishes have
been assumed as an outgroup to the tetrapod/lungfish/coelacanth clade, an
assumption supported by morphological evidence. Standard methods of
molecular phylogenetics applied to the protein-encoding genes of
mitochondria, however, give a bizarre tree in which lamprey groups with
lungfish and, therefore, ray-finned fishes are not the outgroup to a
tetrapod/lungfish/coelacanth clade. All of the dozens of published
phylogenetic methods, including every possible modification to maximum
likelihood known to us (such as inclusion of site heterogeneity and
exclusion of potentially misleading hydrophobic amino acids), fail to place
the ray-finned fishes in a biologically acceptable position. A likely cause
of this failure may be the use of an inappropriate outgroup. Accordingly,
we have determined the complete mitochondrial DNA sequence from the shark,
Mustelus manazo, which we have used as an alternative and more proximal
outgroup than the lamprey. Using sharks as the outgroup, lungfish appear to
be the closest living relative of tetrapods, although the possibility of a
lungfish/coelacanth clade being the sister group of tetrapods cannot be
excluded.
相似文献
194.
Jaana M. Kusnetsov Hannele R. Jousimies-Somer Aino I. Nevalainen P. J. Martikainen 《Journal of applied microbiology》1994,76(2):155-162
The efficacy of a non-selective medium and two selective media were compared for the isolation of legionellas from water samples. The effect of acid wash treatment for decontamination of the water samples on the isolation frequency of legionellas was also studied. The 236 samples were taken from cooling, humidifying and drinking water systems; 21% were legionella-positive when inoculated directly on modified Wadowsky-Yee (MWY) medium and 26% were positive when concentrated (x 200) before cultivation on MWY or CCVC media. Inoculation on MWY medium after concentration followed by decontamination by the acid-wash technique gave the highest isolation frequency (31%). The lowest frequency (8%) was found with the non-selective BCYEα medium. An isolation frequency of 28% was achieved with the BCYEα medium after concentration and acid-wash treatment of the samples. Forty per cent of the samples were positive for legionellas when the results from all the culture methods were combined. Not all the legionella-positive samples were identified by a single culture method. Ninety-three of the 95 positive samples were detected with the two best combinations of three culture methods. The best culture method for detecting legionellas depended on the source of the water sample. Some water quality characteristics, like temperature and organic matter content, affected the isolation frequency of Legionella spp. 相似文献
195.
Demonstration of immunoreactive acid cysteine-proteinase inhibitor in reticulum cells of lymph node germinal centres 总被引:2,自引:0,他引:2
A Rinne M Alavaikko M J?rvinen J Martikainen T Karttunen V Hopsu-Havu 《Virchows Archiv. B, Cell pathology including molecular pathology》1983,43(2):121-126
Seven human lymph nodes showing different types of reactive change, were examined for the presence of acid cysteine-proteinase inhibitor (ACPI) by the peroxidase-antiperoxidase method. A clear positive reaction was found in the germinal centres. The staining pattern indicated immunoreactivity of the dendritic reticulum cells, but the possibility that other cells, particularly histiocytic reticulum cells, may also react with antiserum raised against ACPI cannot be excluded. 相似文献
196.
197.
Decomposable graphical Gaussian model determination 总被引:8,自引:0,他引:8
198.
Green-tree retention is a relatively new forestry application, which aims at decreasing the negative effects of clear-cut
logging on forest biodiversity. In this study, the value of retained aspens in maintaining diverse assemblages of wood-decaying
fungi (polypores; Basidiomycota) on clear-cuts was investigated, after the retention trees had died, fallen and started to
decay. A total of 110 fallen aspen trunks were investigated on clear-cuts and within old-growth forests in eastern Finland,
southern boreal zone; and 499 records of polypores belonging to 46 species were made. The intermediately decayed trunks on
a clear-cut area hosted more species and more red-listed species than did trunks within forests. Most of the polypore species
with more than two records were found in both habitats. These results suggest that many aspen-associated polypores are able
to live and reproduce in sun-exposed habitats, if the quality and quantity of dead wood fulfill the species-specific requirements.
This unexpected result, however, may be partly due to the exceptionally great abundance of aspen in the study area. Furthermore,
in the long term, the local benefits of fallen retention trees can be limited, unless the local continuity of large aspens,
both living and dead, is ensured. 相似文献