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1.
William F. Guerin 《Microbial ecology》1989,17(1):89-104
Paired surface microlayer and bulk water samples from five sites in the Great Bay Estuary, New Hampshire, were examined with regard to numbers of bacteria,14C-phenanthrene biodegradation potentials, and organic and inorganic chemical characteristics. Microlayer samples were generally enriched in nutrients (N and P), dissolved organic matter, and culturable heterotrophic bacteria compared with their corresponding bulk waters. Microlayer samples from marina environments were also enriched in aromatic hydrocarbons, as determined by UV spectrophotometric and fluorometric analyses, and demonstrated substantial phenanthrene biodegradation activity in the assay employed. Biodegradation activity of marina bulk water samples ranged from nil to levels exceeding those exhibited by microlayer samples. No diminution of biodegradation activity was observed after filtration (1.2 m effective retention) of microlayer water, indicating that the responsible organisms were not particle-associated. Phenanthrene-degrading bacteria, enumerated by counting clearing zones in a crystalline phenanthrene overlay after colony development on a phenanthrene/toluene agar (PTA) medium, were superior to epifluorescence direct counts or standard plate counts on PTA or estuarine nutrient agar in predicting14C-phenanthrene biodegradative activity. 相似文献
2.
The role of subunit 4, a nuclear-encoded protein of the F0 sector of yeast mitochondrial ATP synthase, in the assembly of the whole complex 总被引:3,自引:0,他引:3
M F Paul J Velours G Arselin de Chateaubodeau M Aigle B Guerin 《European journal of biochemistry》1989,185(1):163-171
The yeast nuclear gene ATP4, encoding the ATP synthase subunit 4, was disrupted by insertion into the middle of it the selective marker URA3. Transformation of the Saccharomyces cerevisiae strain D273-10B/A/U produced a mutant unable to grow on glycerol medium. The ATP4 gene is unique since subunit 4 was not present in mutant mitochondria; the hypothetical truncated subunit 4 was never detected. ATPase was rendered oligomycin-insensitive and the F1 sector of this mutant appeared loosely bound to the membrane. Analysis of mitochondrially translated hydrophobic subunits of F0 revealed that subunits 8 and 9 were present, unlike subunit 6. This indicated a structural relationship between subunits 4 and 6 during biogenesis of F0. It therefore appears that subunit 4 (also called subunit b in beef heart and Escherichia coli ATP synthases) plays at least a structural role in the assembly of the whole complex. Disruption of the ATP4 gene also had a dramatic effect on the assembly of other mitochondrial complexes. Thus, the cytochrome oxidase activity of the mutant strain was about five times lower than that of the wild type. In addition, a high percentage of spontaneous rho- mutants was detected. 相似文献
3.
Expression of class I genes in the major histocompatibility complex: identification of eight distinct mRNAs in DBA/2 mouse liver 总被引:12,自引:0,他引:12
The mouse H-2 multigene family includes the genes coding for the major transplantation antigens and for genes located in the Qa-TIa region. We have studied a collection of class I cDNA clones made from liver mRNA of DBA/2 mice (H-2d haplotype) and found that at least six distinct class I genes are transcribed, including three genes of the Qa-TIa region. Two of these six genes each yield two distinct mRNAs, resulting from alternate splicing. Altogether, liver cells may express at least eight distinct class I polypeptides, of which three might be secreted, while one may be a new presumptive nonpolymorphic surface antigen. 相似文献
4.
Astrocytes induce neural microvascular endothelial cells to form capillary-like structures in vitro 总被引:9,自引:0,他引:9
Astrocytes maintain a unique association with the central nervous system microvasculature and are thought to play a role in neural microvessel formation and differentiation. We investigated the influence of astroglial cells on neural microvascular endothelial differentiation in vitro. Using an astroglial-endothelial coculture system, rat brain astrocytes and C6 cells of astroglial lineage are shown to induce bovine retinal microvascular endothelial (BRE) cells to form capillary-like structures. Light microscopic evidence for endothelial reorganization began within 48 hours and was complete 72-96 hours following the addition of BRE cells to 1-day-old astroglial cultures. The extent of BRE reorganization was quantitated by computer-assisted analysis and shown to be dependent upon the density of both the BRE and C6 cells within the cocultures. Coculture conditions in which BRE cells were separated from C6 cells by porous membranes failed to generate this endothelial cell change. Likewise, C6-conditioned media and C6-endothelial coculture conditioned media did not induce BRE cell reorganization. Extracellular laminin within the C6-endothelial cocultures, identified by indirect immunofluorescence, was concentrated at the endothelial-astroglial interface of capillary-like structures consistent with incipient basement membrane formation. Astroglial cells accumulated adjacent to capillary-like structures suggesting the presence of bidirectional influences between the reorganized endothelial cells and astroglia. This is the first demonstration of astroglial induction of angiogenesis in vitro and these findings support a functional role for perivascular astrocytes in the vascularization of neural tissue such as retina and brain. 相似文献
5.
34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals. 相似文献
6.
Microsites are created by abiotic and biotic features of the landscape and may provide essential habitats for the persistence of biota. Forest canopies and understorey plants may moderate wind and solar radiation to create microclimatic conditions that differ considerably from regional climates. Skirt-forming plants, where senescent leaves create hut-like cavities around the stem, create microsites that are sheltered from ambient conditions and extreme weather events, constituting potential refuges for wildlife. We investigate day and night temperatures and humidity for four locations (grass tree cavities, soil, 20 cm above-ground, 1 m above-ground) in a South Australian forest with relatively open canopy of stringybark eucalypts (Eucalyptus baxteri, E. obliqua) and an understorey of skirt-forming grass trees (Xanthorrhoea semiplana) at 5, 10, 20, and 40 m from the forest edge. We also measured the percentage of canopy and understorey covers. Generally, temperature and humidity differed significantly between more sheltered (grass tree cavities, soil) and open-air microsites, with the former being cooler during the day and warmer and more humid during the night. Furthermore, our results suggest that canopy cover tends to decrease, and understorey cover tends to increase, the temperature of microsites. Distance to the edge was not significantly related to temperature for any microsite, suggesting that the edge effect did not extend beyond 10 m from the edge. Overall, grass trees influenced microclimatic conditions by forming a dense understorey and providing cavities that are relatively insulated. The capacity of grass tree cavities to buffer external conditions increased linearly with ambient temperatures, by 0.46°C per degree increase in maximum and 0.25°C per degree decrease in minimum temperatures, potentially offsetting climate warming and enabling persistence of fauna within their thermal limits. These climate moderation properties will make grass trees increasingly important refuges as extreme weather events become more common under anthropogenic climate change. 相似文献
7.
Laetitia Mathon Virginie Marques Stéphanie Manel Camille Albouy Marco Andrello Emilie Boulanger Julie Deter Régis Hocdé Fabien Leprieur Tom B. Letessier Nicolas Loiseau Eva Maire Alice Valentini Laurent Vigliola Florian Baletaud Sandra Bessudo Tony Dejean Nadia Faure Pierre-Edouard Guerin Meret Jucker Jean-Baptiste Juhel Kadarusman Andrea Polanco F. Laurent Pouyaud Dario Schwörer Kirsten F. Thompson Marc Troussellier Hagi Yulia Sugeha Laure Velez Xiaowei Zhang Wenjun Zhong Loïc Pellissier David Mouillot 《Global Ecology and Biogeography》2023,32(8):1336-1352
Aim
Coastal fishes have a fundamental role in marine ecosystem functioning and contributions to people, but face increasing threats due to climate change, habitat degradation and overexploitation. The extent to which human pressures are impacting coastal fish biodiversity in comparison with geographic and environmental factors at large spatial scale is still under scrutiny. Here, we took advantage of environmental DNA (eDNA) metabarcoding to investigate the relationship between fish biodiversity, including taxonomic and genetic components, and environmental but also socio-economic factors.Location
Tropical, temperate and polar coastal areas.Time period
Present day.Major taxa studied
Marine fishes.Methods
We analysed fish eDNA in 263 stations (samples) in 68 sites distributed across polar, temperate and tropical regions. We modelled the effect of environmental, geographic and socio-economic factors on α- and β-diversity. We then computed the partial effect of each factor on several fish biodiversity components using taxonomic molecular units (MOTU) and genetic sequences. We also investigated the relationship between fish genetic α- and β-diversity measured from our barcodes, and phylogenetic but also functional diversity.Results
We show that fish eDNA MOTU and sequence α- and β-diversity have the strongest correlation with environmental factors on coastal ecosystems worldwide. However, our models also reveal a negative correlation between biodiversity and human dependence on marine ecosystems. In areas with high dependence, diversity of all fish, cryptobenthic fish and large fish MOTUs declined steeply. Finally, we show that a sequence diversity index, accounting for genetic distance between pairs of MOTUs, within and between communities, is a reliable proxy of phylogenetic and functional diversity.Main conclusions
Together, our results demonstrate that short eDNA sequences can be used to assess climate and direct human impacts on marine biodiversity at large scale in the Anthropocene and can further be extended to investigate biodiversity in its phylogenetic and functional dimensions. 相似文献8.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
9.
10.
Amino acid sequence of a new mitochondrially synthesized proteolipid of the ATP synthase of Saccharomyces cerevisiae. 总被引:4,自引:2,他引:2 下载免费PDF全文
The purification and the amino acid sequence of a proteolipid translated on ribosomes in yeast mitochondria is reported. This protein, which is a subunit of the ATP synthase, was purified by extraction with chloroform/methanol (2/1) and subsequent chromatography on phosphocellulose and reverse phase h.p.l.c. A mol. wt. of 5500 was estimated by chromatography on Bio-Gel P-30 in 80% formic acid. The complete amino acid sequence of this protein was determined by automated solid phase Edman degradation of the whole protein and of fragments obtained after cleavage with cyanogen bromide. The sequence analysis indicates a length of 48 amino acid residues. The calculated mol. wt. of 5870 corresponds to the value found by gel chromatography. This polypeptide contains three basic residues and no negatively charged side chain. The three basic residues are clustered at the C terminus. The primary structure of this protein is in full agreement with the predicted amino acid sequence of the putative polypeptide encoded by the mitochondrial aap1 gene recently discovered in Saccharomyces cerevisiae. Moreover, this protein shows 50% homology with the amino acid sequence of a putative polypeptide encoded by an unidentified reading frame also discovered near the mitochondrial ATPase subunit 6 gene in Aspergillus nidulans. 相似文献