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991.
Richard E. Haaland Paulina A. Hawkins Jesus Salazar-Gonzalez Amber Johnson Amanda Tichacek Etienne Karita Olivier Manigart Joseph Mulenga Brandon F. Keele George M. Shaw Beatrice H. Hahn Susan A. Allen Cynthia A. Derdeyn Eric Hunter 《PLoS pathogens》2009,5(1)
The HIV-1 epidemic in sub-Saharan Africa is driven largely by heterosexual transmission of non-subtype B viruses, of which subtypes C and A are predominant. Previous studies of subtype B and subtype C transmission pairs have suggested that a single variant from the chronically infected partner can establish infection in their newly infected partner. However, in subtype A infected individuals from a sex worker cohort and subtype B individuals from STD clinics, infection was frequently established by multiple variants. This study examined over 1750 single-genome amplified viral sequences derived from epidemiologically linked subtype C and subtype A transmission pairs very early after infection. In 90% (18/20) of the pairs, HIV-1 infection is initiated by a single viral variant that is derived from the quasispecies of the transmitting partner. In addition, the virus initiating infection in individuals who were infected by someone other than their spouse was characterized to determine if genital infections mitigated the severe genetic bottleneck observed in a majority of epidemiologically linked heterosexual HIV-1 transmission events. In nearly 50% (3/7) of individuals infected by someone other than their spouse, multiple genetic variants from a single individual established infection. A statistically significant association was observed between infection by multiple genetic variants and an inflammatory genital infection in the newly infected individual. Thus, in the vast majority of HIV-1 transmission events in cohabiting heterosexual couples, a single genetic variant establishes infection. Nevertheless, this severe genetic bottleneck can be mitigated by the presence of inflammatory genital infections in the at risk partner, suggesting that this restriction on genetic diversity is imposed in large part by the mucosal barrier. 相似文献
992.
Sirtuin proteins comprise a unique class of NAD+-dependent protein deacetylases. Although several structures of sirtuins have been determined, the mechanism by which NAD+ cleavage occurs has remained unclear. We report the structures of ternary complexes containing NAD+ and acetylated peptide bound to the bacterial sirtuin Sir2Tm and to a catalytic mutant (Sir2Tm(H116Y)). NAD+ in these structures binds in a conformation different from that seen in previous structures, exposing the alpha face of the nicotinamide ribose to the carbonyl oxygen of the acetyl lysine substrate. The NAD+ conformation is identical in both structures, suggesting that proper coenzyme orientation is not dependent on contacts with the catalytic histidine. We also present the structure of Sir2Tm(H116A) bound to deacteylated peptide and 3'-O-acetyl ADP ribose. Taken together, these structures suggest a mechanism for nicotinamide cleavage in which an invariant phenylalanine plays a central role in promoting formation of the O-alkylamidate reaction intermediate and preventing nicotinamide exchange. 相似文献
993.
Mary A. Robinson Stephen W. Tuttle Cynthia M. Otto Cameron J. Koch 《Free radical biology & medicine》2010,48(2):189-195
Stimulated macrophages produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS) using molecular O2, L-arginine, and NADPH. Exposure of macrophages to hypoxia decreases NO production within seconds, suggesting substrate limitation as the mechanism. Conflicting data exist regarding the effect of pO2 on NADPH production via the oxidative pentose phosphate cycle (OPPC). Therefore, the present studies were developed to determine whether NADPH could be limiting for NO production under hypoxia. Production of NO metabolites (NOx) and OPPC activity by RAW 264.7 cells was significantly increased by stimulation with lipopolysaccharide (LPS) and interferon γ (IFNγ) at pO2 ranging from 0.07 to 50%. OPPC activity correlated linearly with NOx production at pO2 > 0.13%. Increased OPPC activity by stimulated RAW 264.7 cells was significantly reduced by 1400 W, an iNOS inhibitor. OPPC activity was significantly increased by concomitant treatment of stimulated RAW 264.7 cells with chemical oxidants such as hydroxyethyldisulfide or pimonidazole, at 0.07 and 50% O2, without decreasing NOx production. These results are the first to investigate the effect of pO2 on the relationship between NO production and OPPC activity, and to rule out limitations in OPPC activity as a mechanism by which NO production is decreased under hypoxia. 相似文献
994.
995.
Cynthia A. Froyd Jessica A. Lee Atholl J. Anderson Simon G. Haberle Peter E. Gasson Katherine J. Willis 《Vegetation History and Archaeobotany》2010,19(3):207-217
Charcoal fragments from five historic campsite locations in the Galápagos Islands were identified and radiocarbon dated to
investigate postulated early human presence in the archipelago, historic fuel wood collection patterns and the resultant impact
on native vegetation. A variety of taxa and fuel types were revealed to be present in the charcoal assemblages, indicating
geographically driven rather than species-specific methods of collection. Historic anthropogenic impact was therefore spread
amongst woody taxa in the lowland plant communities, with severity dependent on proximity to campsite location. All charred
remains were found to date from within the historic period, supporting the preponderance of archaeological evidence indicating
that human presence did not begin in Galápagos until after European discovery. 相似文献
996.
Cynthia Sequeiros Marisol Vallejo Emilio Rogelio Marguet Nelda Lila Olivera 《Archives of microbiology》2010,192(4):237-245
After enrichment of Odontesthes platensis intestinal contents, 53 lactic acid bacteria (LAB) were isolated. From the four isolates that showed inhibitory activity
against Lactococcus garvieae 03/8460, strain TW34 was selected because it exerted the strongest inhibition. It also inhibited other Gram-positive bacteria,
but not Gram-negative fish pathogens. Phenotypic and 16S rDNA phylogenetic analyses showed that TW34 belongs to Lactococcus lactis. In addition, TW34 showed to be sensitive to different antibiotics. The production of the inhibitory agent against L. garvieae was growth associated, and it was significantly influenced by the incubation temperature. The optimal temperature for the
antimicrobial production was as low as 15°C. Both acidification and hydrogen peroxide production were ruled out as the source
of inhibition. In contrast, the antimicrobial activity was completely lost by treatment with proteolytic enzymes, which confirmed
that the inhibitory substance was a bacteriocin. The bacteriocin was highly thermostable (121°C for 15 min) and active between
pH 3 and 11. It remained stable for up to 2 months when stored at 4°C and up to 6 months at −20°C. Our results suggest that
the strain L. lactis TW34 could provide an alternative for lactococcosis control and therefore be considered for future challenge experiments
with fish. 相似文献
997.
998.
999.
Monica M. Lins-de-Barros Ricardo P. Vieira Alexander M. Cardoso Vivian A. Monteiro Aline S. Turque Cynthia B. Silveira Rodolpho M. Albano Maysa M. Clementino Orlando B. Martins 《Microbial ecology》2010,59(3):523-532
Reef-building corals may be seen as holobiont organisms, presenting diverse associated microbial communities. Best known is
the symbiotic relationship with zooxanthellae, but Archaea, Bacteria, fungi, viruses, and algal plastids are also abundant.
Until now, there is little information concerning microbial communities associated with Brazilian corals. The present study
aims to describe the diversity of Archaea, Bacteria, and eukaryotic algal plastid communities associated with two sympatric
species, Siderastrea stellata and Mussismilia hispida, from Southeastern Brazil, using 16S rRNA gene libraries. Since corals present a high number of other associated invertebrates,
coral barcoding (COI) was performed to confirm the exclusive occurrence of coral DNA in our samples. Our analysis yielded
354 distinct microbial OTUs, represented mainly by novel phylotypes. Richness (Chao1 and ACE) and diversity (H') estimations
of the microbial communities associated with both species were high and comparable to other studies. Rarefaction analyses
showed that microbial diversity of S. stellata is higher than that of M. hispida. Libshuff comparative analyses showed that the highest microbial community similarity between the two coral species occurred
in the bacterial libraries, while archaeal and plastidial communities were significantly different. Crenarchaeota dominated
archaeal communities, while Proteobacteria was the most abundant bacterial phylum, dominated by alpha-Proteobacteria. Plastids
were also represented by novel phylotypes and did not match with any 16S rRNA sequences of Cyanobacteria and zooxanthellae
from GenBank. Our data improves the pool of available information on Brazilian coral microbes and shows corals as sources
of diverse prokaryotic and picoeukaryotic communities. 相似文献
1000.
Didier F. Pisani Cynthia D.K. Bottema Christian Dani 《Biochemical and biophysical research communications》2010,396(3):767-773
Fat cell accumulation in skeletal muscle is a major characteristic of various disorders, such as obesity, sarcopenia and dystrophies. Moreover, these fat cells could be involved in muscle homeostasis regulation as previously described for adipocytes in bone marrow. Despite recent advances on the topic, no clearly characterized mouse model is currently available to study fat accumulation within skeletal muscle. Here, we report a detailed characterization of a mouse model of skeletal muscle fat cell accumulation after degeneration induced by intra-muscular injection of glycerol. Information is provided on the kinetics of degeneration/fat deposition, including the quantity of fat deposited based on various parameters such as glycerol concentration, age, sex and strain of mice. Finally, these fat cells are characterized as true white adipocytes morphologically and molecularly. Our study shows that the mouse adipocyte accumulation within skeletal muscle after glycerol degeneration is a reproducible, transposable and easy model to use. This mouse model should allow a more comprehensive understanding of the impact of adipocyte accumulation in skeletal muscle pathophysiology. 相似文献