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The complete genome sequence of Roseobacter denitrificans reveals a mixotrophic rather than photosynthetic metabolism 下载免费PDF全文
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George B. Chuyong David Kenfack Kyle E. Harms Duncan W. Thomas Richard Condit Liza S. Comita 《Plant Ecology》2011,212(8):1363-1374
Niche differentiation with respect to habitat has been hypothesized to shape patterns of diversity and species distributions
in plant communities. African forests have been reported to be relatively less diverse compared to highly diversed regions
of the Amazonian or Southeast Asian forests, and might be expected to have less niche differentiation. We examined patterns
of structural and floristic differences among five topographically defined habitats for 494 species with stems ≥1 cm dbh in
a 50-ha plot in Korup National Park, Cameroon. In addition, we tested for species–habitat associations for 272 species (with
more than 50 individuals in the plot) using Torus translation randomization tests. Tree density and basal area were lowest
in areas with negative convexity, which contained streams or were inundated during rainy periods and highest in moist well-drained
habitats. Species composition and diversity varied along the topographical gradient from low flat to ridge top habitats. The
low depression and low flat habitats were characterized by high diversity and similar species composition, relative to slopes,
high gullies and ridge tops. Sixty-three percent of the species evaluated showed significant positive associations with at
least one of the five habitat types. The majority of associations were with low depressions (75 species) and the fewest with
ridge tops (8 species). The large number of species–habitat associations and the pronounced contrast between low (valley)
and elevated (ridgetop) habitats in the Korup plot shows that niche differentiation with respect to edaphic variables (e.g.,
soil moisture, nutrients) contributes to local scale tree species distributions and to the maintenance of diversity in African
forests. 相似文献
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Background
Human metapneumovirus and respiratory syncytial virus can cause severe respiratory diseases, especially in infants, young children, and the elderly. So far it remains unclear why infections in the elderly become life threatening despite the presence of neutralizing antibodies in the serum, and to which extent double infections worsen the clinical course.Methods
Young and aged BALB/c-mice were infected with RSV or/and HMPV. Appearance of the mice was observed during course of infection. On day 5 p.i. animals were dispatched by cervical dislocation and levels of TNF-α and NF-κB were determined.Results
The observation of activity, weight and appearance of the different mice showed no differences among the tested groups. Despite this, the immunologic response depends on the animals'' age and the virus they were infected with. In young animals, NF-κB levels were elevated if infected with HMPV and HMPV/RSV but remained low in RSV infections, whereas in aged animals the opposite was observed: solely RSV-infected animals showed elevated levels of NF-κB. TNF-α was slightly elevated in HMPV-infected young and old animals, but only in young animals this elevation was significant.Conclusions
Contrary to other studies, no weight loss or change in activity despite productive lung infection with the different viruses were observed. This may be due to the weaker anaesthesia or the lesser volume of virus solution used, leading to less stress in the animals. The observed differences in TNF-α and NF-κB elevation lead to the assumption that young and old individuals have different mechanisms to react against the viruses. 相似文献56.
Sampey BP Vanhoose AM Winfield HM Freemerman AJ Muehlbauer MJ Fueger PT Newgard CB Makowski L 《Obesity (Silver Spring, Md.)》2011,19(6):1109-1117
Obesity has reached epidemic proportions worldwide and reports estimate that American children consume up to 25% of calories from snacks. Several animal models of obesity exist, but studies are lacking that compare high-fat diets (HFD) traditionally used in rodent models of diet-induced obesity (DIO) to diets consisting of food regularly consumed by humans, including high-salt, high-fat, low-fiber, energy dense foods such as cookies, chips, and processed meats. To investigate the obesogenic and inflammatory consequences of a cafeteria diet (CAF) compared to a lard-based 45% HFD in rodent models, male Wistar rats were fed HFD, CAF or chow control diets for 15 weeks. Body weight increased dramatically and remained significantly elevated in CAF-fed rats compared to all other diets. Glucose- and insulin-tolerance tests revealed that hyperinsulinemia, hyperglycemia, and glucose intolerance were exaggerated in the CAF-fed rats compared to controls and HFD-fed rats. It is well-established that macrophages infiltrate metabolic tissues at the onset of weight gain and directly contribute to inflammation, insulin resistance, and obesity. Although both high fat diets resulted in increased adiposity and hepatosteatosis, CAF-fed rats displayed remarkable inflammation in white fat, brown fat and liver compared to HFD and controls. In sum, the CAF provided a robust model of human metabolic syndrome compared to traditional lard-based HFD, creating a phenotype of exaggerated obesity with glucose intolerance and inflammation. This model provides a unique platform to study the biochemical, genomic and physiological mechanisms of obesity and obesity-related disease states that are pandemic in western civilization today. 相似文献
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