全文获取类型
收费全文 | 233篇 |
免费 | 19篇 |
出版年
2023年 | 2篇 |
2021年 | 5篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 12篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 14篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1966年 | 3篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1962年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有252条查询结果,搜索用时 15 毫秒
11.
Alyssa A. Carrell Max Kolton Jennifer B. Glass Dale A. Pelletier Melissa J. Warren Joel E. Kostka Colleen M. Iversen Paul J. Hanson David J. Weston 《Global Change Biology》2019,25(9):2993-3004
Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N2 fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N2 fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N2 fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N2 fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands. 相似文献
12.
Will A. Overholt Patrick Schwing Kala M. Raz David Hastings David J. Hollander Joel E. Kostka 《Environmental microbiology》2019,21(11):4316-4329
The microbial ecology of oligotrophic deep ocean sediments is understudied relative to their shallow counterparts, and this lack of understanding hampers our ability to predict responses to current and future perturbations. The Gulf of Mexico has experienced two of the largest accidental marine oil spills, the 1979 Ixtoc-1 blowout and the 2010 Deepwater Horizon (DWH) discharge. Here, microbial communities were characterized for 29 sites across multiple years in > 700 samples. The composition of the seafloor microbiome was broadly consistent across the region and was well approximated by the overlying water depth and depth within the sediment column, while geographic distance played a limited role. Biogeographical distributions were employed to generate predictive models for over 4000 OTU that leverage easy-to-obtain geospatial variables which are linked to measured sedimentary oxygen profiles. Depth stratification and putative niche diversification are evidenced by the distribution of taxa that mediate the microbial nitrogen cycle. Furthermore, these results demonstrate that sediments impacted by the DWH spill had returned to near baseline conditions after 2 years. The distributions of benthic microorganisms in the Gulf can be constrained, and moreover, deviations from these predictions may pinpoint impacted sites and aid in future response efforts or long-term stability studies. 相似文献
13.
14.
A strain of naked amoeba isolated from pikeperch (Sander lucioperca (L.)) kidney tissue has been characterized using light- and transmission electron microscopy. Sequencing of SSU rDNA and phylogenetic analysis based on a broad dataset of sequences completed our study. All data obtained suggest that this strain belongs to a species that has not been described before. As none of the existing genera of amoebae is applicable to this organism, the new genus Grellamoeba is established and the type species Grellamoeba robusta is described. Although the phylogenetic position of the SSU rDNA sequence of the type strain of G. robusta is sensitive to the method of analysis applied, a tendency to group with Acramoeba dendroida Smirnov, Nassonova et Cavalier-Smith, 2008 is evident. 相似文献
15.
Fibulins are a newly recognized family of extracellular matrix proteins. The five known members of the family share an elongated structure and many calcium-binding sites, owing to the presence of tandem arrays of epidermal growth factor-like domains. They have overlapping binding sites for several basement-membrane proteins, tropoelastin, fibrillin, fibronectin and proteoglycans, and they participate in diverse supramolecular structures. New insights into their biological roles are now emerging from studies of transgenic mice and of some inherited human diseases. 相似文献
16.
17.
Sulfate-reducing bacteria methylate mercury at variable rates in pure culture and in marine sediments 总被引:5,自引:0,他引:5
King JK Kostka JE Frischer ME Saunders FM 《Applied and environmental microbiology》2000,66(6):2430-2437
Differences in methylmercury (CH(3)Hg) production normalized to the sulfate reduction rate (SRR) in various species of sulfate-reducing bacteria (SRB) were quantified in pure cultures and in marine sediment slurries in order to determine if SRB strains which differ phylogenetically methylate mercury (Hg) at similar rates. Cultures representing five genera of the SRB (Desulfovibrio desulfuricans, Desulfobulbus propionicus, Desulfococcus multivorans, Desulfobacter sp. strain BG-8, and Desulfobacterium sp. strain BG-33) were grown in a strictly anoxic, minimal medium that received a dose of inorganic Hg 120 h after inoculation. The mercury methylation rates (MMR) normalized per cell were up to 3 orders of magnitude higher in pure cultures of members of SRB groups capable of acetate utilization (e.g., the family Desulfobacteriaceae) than in pure cultures of members of groups that are not able to use acetate (e.g., the family Desulfovibrionaceae). Little or no Hg methylation was observed in cultures of Desulfobacterium or Desulfovibrio strains in the absence of sulfate, indicating that Hg methylation was coupled to respiration in these strains. Mercury methylation, sulfate reduction, and the identities of sulfate-reducing bacteria in marine sediment slurries were also studied. Sulfate-reducing consortia were identified by using group-specific oligonucleotide probes that targeted the 16S rRNA molecule. Acetate-amended slurries, which were dominated by members of the Desulfobacterium and Desulfobacter groups, exhibited a pronounced ability to methylate Hg when the MMR were normalized to the SRR, while lactate-amended and control slurries had normalized MMR that were not statistically different. Collectively, the results of pure-culture and amended-sediment experiments suggest that members of the family Desulfobacteriaceae have a greater potential to methylate Hg than members of the family Desulfovibrionaceae have when the MMR are normalized to the SRR. Hg methylation potential may be related to genetic composition and/or carbon metabolism in the SRB. Furthermore, we found that in marine sediments that are rich in organic matter and dissolved sulfide rapid CH(3)Hg accumulation is coupled to rapid sulfate reduction. The observations described above have broad implications for understanding the control of CH(3)Hg formation and for developing remediation strategies for Hg-contaminated sediments. 相似文献
18.
Steiner H Kostka M Romig H Basset G Pesold B Hardy J Capell A Meyn L Grim ML Baumeister R Fechteler K Haass C 《Nature cell biology》2000,2(11):848-851
Endoproteolysis of beta-amyloid precursor protein (betaAPP) and Notch requires conserved aspartate residues in presenilins 1 and 2 (PS1 and PS2). Although PS1 and PS2 have therefore been proposed to be aspartyl proteases, no homology to other aspartyl proteases has been found. Here we identify homology between the presenilin active site and polytopic aspartyl proteases of bacterial origin, thus supporting the hypothesis that presenilins are novel aspartyl proteases. 相似文献
19.
Urlaub H Hartmuth K Kostka S Grelle G Lührmann R 《The Journal of biological chemistry》2000,275(52):41458-41468
We describe a novel approach to identify RNA-protein cross-linking sites within native small nuclear ribonucleoprotein (snRNP) particles from HeLa cells. It combines immunoprecipitation of the UV-irradiated particles under semi-denaturing conditions with primer extension analysis of the cross-linked RNA moiety. In a feasibility study, we initially identified the exact cross-linking sites of the U1 70-kDa (70K) protein in stem-loop I of U1 small nuclear RNA (snRNA) within purified U1 snRNPs and then confirmed the results by a large-scale preparation that allowed N-terminal sequencing and matrix-assisted laser desorption ionization mass spectrometry of purified cross-linked peptide-oligonucleotide complexes. We identified Tyr(112) and Leu(175) within the RNA-binding domain of the U1 70K protein to be cross-linked to G(28) and U(30) in stem-loop I, respectively. We further applied our immunoprecipitation approach to HeLa U5 snRNP, as part of purified 25 S U4/U6.U5 tri-snRNPs. Cross-linking sites between the U5-specific 220-kDa protein (human homologue of Prp8p) and the U5 snRNA were located at multiple nucleotides within the highly conserved loop 1 and at one site in internal loop 1 of U5 snRNA. The cross-linking of four adjacent nucleotides indicates an extended interaction surface between loop 1 and the 220-kDa protein. In summary, our approach provides a rapid method for identification of RNA-protein contact sites within native snRNP particles as well as other ribonucleoprotein particles. 相似文献
20.
A C Frantz A D McDevitt L C Pope J Kochan J Davison C F Clements M Elmeros G Molina-Vacas A Ruiz-Gonzalez A Balestrieri K Van Den Berge P Breyne E Do Linh San E O ?gren F Suchentrunk L Schley R Kowalczyk B I Kostka D ?irovi? N ?prem M Colyn M Ghirardi V Racheva C Braun R Oliveira J Lanszki A Stubbe M Stubbe N Stier T Burke 《Heredity》2014,113(5):443-453
Although the phylogeography of European mammals has been extensively investigated
since the 1990s, many studies were limited in terms of sampling distribution, the
number of molecular markers used and the analytical techniques employed, frequently
leading to incomplete postglacial recolonisation scenarios. The broad-scale genetic
structure of the European badger (Meles meles) is of interest as it may
result from historic restriction to glacial refugia and/or recent anthropogenic
impact. However, previous studies were based mostly on samples from western Europe,
making it difficult to draw robust conclusions about the location of refugia,
patterns of postglacial expansion and recent demography. In the present study,
continent-wide sampling and analyses with multiple markers provided evidence for two
glacial refugia (Iberia and southeast Europe) that contributed to the genetic
variation observed in badgers in Europe today. Approximate Bayesian computation
provided support for a colonisation of Scandinavia from both Iberian and southeastern
refugia. In the whole of Europe, we observed a decline in genetic diversity with
increasing latitude, suggesting that the reduced diversity in the peripheral
populations resulted from a postglacial expansion processes. Although MSVAR v.1.3
also provided evidence for recent genetic bottlenecks in some of these peripheral
populations, the simulations performed to estimate the method''s power to
correctly infer the past demography of our empirical populations suggested that the
timing and severity of bottlenecks could not be established with certainty. We urge
caution against trying to relate demographic declines inferred using MSVAR with
particular historic or climatological events. 相似文献