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31.
The Vaal River, South Africa, historically had a rich diversity of native submerged macrophytes with at least 13 species from 5 families recorded. Over the past 10 years there has been a noticeable reduction in the occurrence and diversity of submerged macrophytes in the river. It is possible that this is linked to the recent increase in the populations of invasive alien grass carp Ctenopharyngodon idella Cuvier & Valenciennes (Cyprinidae) in the river, where populations have been a concern since 2005. Grass carp invasions worldwide have been shown to have severe impacts on macrophyte biodiversity and ecosystem functioning. This fish is an aggressive feeder on submerged macrophytes, as well as being an ecosystem engineer that can change water and sediment chemistry. 相似文献
32.
Carolyn GJ Moonen Kirsten GD Buurma Mouri RJ Faruque Maria G Balta Erol Liefferink Sergio Bizzarro Elena A Nicu Bruno G Loos 《Innate immunity》2020,26(5):331
In periodontitis, polymorphonuclear leucocytes (PMNs) are activated. They entrap and eliminate pathogens by releasing neutrophil extracellular traps (NETs). Abnormal NET degradation is part of a pro-inflammatory status, affecting co-morbidities such as cardiovascular disease. We aimed to investigate the ex vivo NET degradation capacity of plasma from periodontitis patients compared to controls (part 1) and to quantify NET degradation before and after periodontal therapy (part 2). Fresh NETs were obtained by stimulating blood-derived PMNs with phorbol 12-myristate 13-acetate. Plasma samples from untreated periodontitis patients and controls were incubated for 3 h onto freshly generated NETs (part 1). Similarly, for part 2, NET degradation was studied for 91 patients before and 3, 6 and 12 mo after non-surgical periodontal therapy with and without adjunctive systemic antibiotics. Finally, NET degradation was fluorospectrometrically quantified. NET degradation levels did not differ between periodontitis patients and controls, irrespective of subject-related background characteristics. NET degradation significantly increased from 65.6 ± 1.7% before periodontal treatment to 75.7 ± 1.2% at 3 mo post periodontal therapy, and this improvement was maintained at 6 and 12 mo, irrespective of systemic usage of antibiotics. Improved NET degradation after periodontitis treatment is another systemic biomarker reflecting a decreased pro-inflammatory status, which also contributes to an improved cardiovascular condition. 相似文献
33.
The nucleotide sequence of the maize controlling element Activator 总被引:35,自引:0,他引:35
34.
35.
Geographic range size, seedling ecophysiology and phenotypic plasticity in Australian Acacia species 总被引:2,自引:0,他引:2
Aim The degree to which eco‐physiological traits critical to seedling establishment are related to differences in geographic range size among species is not well understood. Here, we first tested the idea that seedling eco‐physiological attributes associated with establishment differ between narrowly distributed and geographically widespread plant species. Secondly, we tested the notion that species occupying wide geographic ranges have greater phenotypic plasticity in response to the environment than contrasted species with more restricted distributions. Location Eastern Australia. Methods We compared five pairs of geographically restricted and widespread Acacia species grown under glasshouse conditions for differences in seedling relative growth rate and associated allocational, morphological and physiological traits. We then examined whether widespread species displayed greater phenotypic plasticity in these traits than narrowly distributed species in response to changes in soil water availability. Results Neither relative growth rate nor any measure of biomass accumulation or allocation differed significantly between seedlings of narrowly distributed and widespread species. In addition, the plasticity of biomass allocation was not greater in widespread species. However, the leaflets of widespread species had higher photosynthetic capacity and greater plasticity of water use efficiency than the leaflets of narrowly distributed species. Main conclusions We demonstrated fundamental differences in the physiology and plasticity of leaflets of widespread and narrowly distributed species. The greater plasticity of these seedling leaflet traits may allow widespread Acacia species to utilize a wider range of environmental conditions in relation to soil moisture than restricted Acacia species. However, we did not find corresponding differences in mean or plasticity of seedling growth and allocational traits. In general, we suggest that relationships between rarity and species traits are both context and taxon specific. 相似文献
36.
Pulmonary acariasis is a sporadic, incidental finding in colony‐raised rhesus macaques (Macaca mulatta). Prophylactic treatment in indoor‐raised and indoor‐housed macaques is not routine due to low prevalence, lack of clinical significance, and potential risk of toxicosis. This case is an unusually severe infestation of Pneumonyssus simicola in an indoor‐housed rhesus macaque, which ultimately resulted in this animal's death. 相似文献
37.
Summary Aerobic and anaerobic N2-fixing bacteria developed in the rhizosphere of barley seedlings and exhibited N2ase activity when seedlings were grown in sterilized sand-nutrient cultures containing low levels of combined nitrogen. The
source of the N2-fixing bacteria appeared to be the seed. Average daily rates up to 0.9 μmoles C2H4 h−1 g−1 dry root tissue were measured, but the intensity of the activity was affected by moisture levels and concentration of combined
N in the rhizosphere. Removal and washing of the roots did not remove the activity, and roots remained active even after surface-sterilization.
An unidentified aerobic N2-fixing bacterium was isolated from the rhizoplane of active barley roots. Inoculation of barley seedlings with the aerobic
N2-fixing bacterium enhanced N2ase activity of excised roots 10-fold, with average rates of 0.9, 1.1 and 1.3 μmoles h−1 g−1 dry root assayed under pO2 of 0.01, 0.02 and 0.04 atm respectively. The aerobic N2-fixing bacterium also exhibited N2ase activity when inoculated into the rhizosphere of oat, rice and wheat seedlings. Microscopic observations of sterilized
live and stained barley roots suggest that the aerobic N2-fixing bacterium is an endophyte which infects root tissue and metamorphoses into vesicle-like structures. 相似文献
38.
James GD Prendergast Harry Campbell Nick Gilbert Malcolm G Dunlop Wendy A Bickmore Colin AM Semple 《BMC evolutionary biology》2007,7(1):72
Background
Evolutionary rates are not constant across the human genome but genes in close proximity have been shown to experience similar levels of divergence and selection. The higher-order organisation of chromosomes has often been invoked to explain such phenomena but previously there has been insufficient data on chromosome structure to investigate this rigorously. Using the results of a recent genome-wide analysis of open and closed human chromatin structures we have investigated the global association between divergence, selection and chromatin structure for the first time. 相似文献39.
40.
Dissolved Oxygen Saturation Controls PAH Biodegradation in Freshwater Estuary Sediments 总被引:1,自引:0,他引:1
Boyd TJ Montgomery MT Steele JK Pohlman JW Reatherford SR Spargo BJ Smith DC 《Microbial ecology》2005,49(2):226-235
Polycyclic aromatic hydrocarbons (PAHs) are common contaminants in terrestrial and aquatic environments and can represent a significant constituent of the carbon pool in coastal sediments. We report here the results of an 18-month seasonal study of PAH biodegradation and heterotrophic bacterial production and their controlling biogeochemical factors from 186 sediment samples taken in a tidally influenced freshwater estuary. For each sampling event, measurements were averaged from 25–45 stations covering ∼250 km2. There was a clear relationship between bacterial production and ambient temperature, but none between production and bottom water dissolved oxygen (DO) % saturation or PAH concentrations. In contrast with other studies, we found no effect of temperature on the biodegradation of naphthalene, phenanthrene, or fluoranthene. PAH mineralization correlated with bottom water DO saturation above 70% (r2 > 0.99). These results suggest that the proportional utilization of PAH carbon to natural organic carbon is as much as three orders of magnitude higher during cooler months, when water temperatures are lower and DO % saturation is higher. Infusion of cooler, well-oxygenated water to the water column overlying contaminated sediments during the summer months may stimulate PAH metabolism preferentially over non-PAH organic matter. 相似文献