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D. Hahn R. Kester M. J. C. Starrenburg A. D. L. Akkermans 《Archives of microbiology》1990,154(4):329-335
Sequences of 16S rRNA of the nitrogen-fixing Frankia strain Ag45/Mut15 and the ineffective Frankia strain AgB1.9 were used to design a genus-specific oligonucleotide probe. Hybridization experiments of this Frankia probe and a second probe, specific for Nif+-Frankia strains only, were used to detect Frankia specific target sequences in RNA isolations from soil. A method is described for direct isolation of RNA from a loamy soil and a peat. Yields of about 10 ng RNA/g wet soil are obtained without detectable contamination with humic acids. Isolation of RNA after initial extraction of bacteria from soil resulted in significantly lower RNA yields, compared to the direct isolation procedure. Hybridization with both probes against rRNA isolations from Frankia-containing soil could detect target sequences within RNA isolations from 1 g wet soil with an estimated detection limit of 104 cells. 相似文献
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Observations on the ultrastructure ofFrankia sp. in root nodules ofDatisca cannabina L. 总被引:1,自引:1,他引:0
Summary The fine structures of the microsymbiont inside the root nodules ofDatisca cannabina have been studied by light, by transmission- and by scanning-electron microscopy. The endophyte is prokaryotic and actinomycetal in nature. The hyphae are septate and branched, diameter 0.3–0.5 m. The tips of hyphae are swollen to form electron-dense, clubshaped to filamentous vesicles, ranging in diameter: 0.4–1.4 m. The endophyte penetrates through walls of the cortial cells. The infected zone is kidney shaped and confined to one side of the acentric stele. The orientation of infection is reversed from other actinorhizae exceptCoriaria. The hyphae are near the host cell wall and vesicles are directed towards the central vacuole. Vesicles are aseptate and no collapsing of the vesicle cell wall (void area) has been observed. Vesicle clusters structures are globular with an opening at one side of the cluster. The host cell is multinucleate or contains a lobed nucleus. Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production. The consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed.Isolated vesicles clusters showed dehydrogenase activity, indicated by the presence of formazan crystals, after incubation with NADH and NBT. Strongest reducing activity was found within the vesicles. The possible role of filamentous vesicles in nitrogen fixation has been discussed. 相似文献
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Felske AD Tzeneva V Heyrman J Langeveld MA Akkermans AD De Vos P 《Microbial ecology》2004,48(1):111-119
The hitherto largely not described phylogenetic neighborhood of Bacillus niacini has been explored by a comprehensive cultivation experiment and genomic variety studies. Previous culture-independent studies demonstrated that ~15% of all Bacillus 16S rDNA directly extracted from soils worldwide was affiliated to B. niacini. Seven different media were inoculated with soil suspensions in serial dilutions and incubated at different temperatures. Then, bacterial colonies were picked and analyzed by sequencing. A mineral medium with acetate as carbon source yielded a B. niacini rate of >3% of all picked colonies. Other media were less efficient but also successful. Applying this culturing approach, we succeeded in obtaining 64 isolates from different Dutch soils. The isolates turned out to be diverse, although closely related to B. niacini as revealed by 16S rDNA sequencing. Close matches with environmental clones were also found, thus demonstrating much more diversity beyond previously known 16S rDNA sequences. The rep-PCR fingerprinting method revealed a high genomic variety, redundancy could not be observed among our isolates. Hence, the hitherto neglected B. niacini lineage, apparently among the most abundant soil Bacillus, was accessible to our cultivation approach. 相似文献
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Sipkema D Heilig HG Akkermans AD Osinga R Tramper J Wijffels RH 《Marine biotechnology (New York, N.Y.)》2003,5(5):443-449
Dissociated sponge cells are easily confused with unicellular organisms. This has been an obstacle in
the development of sponge-cell lines. We developed a molecular detection method to identify cells of the
sponge Dysidea avara in dissociated cell cultures. The 18S ribosomal RNA gene from a Dysidea avara specimen
was sequenced and compared to eukaryotic 18S rDNA sequences picked up from a proliferating cell culture
that originated from a dissociated Dysidea avara specimen. Our method proved unambiguously that this was
not a sponge-cell culture. Therefore, it provides a valuable tool for further research on sponge-cell cultures. 相似文献
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