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131.
Activation of circulating neutrophils has been observed following challenge of horses with chronic obstructive pulmonary disease (COPD) and may facilitate the accumulation of these cells in the airways. In this study, no significant difference was observed between adherence to protein coated plastic of blood neutrophils from asymptomatic COPD-susceptible and normal horses stimulated by the mediators PAF, human recombinant (hr)IL-8 and hrC5a. Twenty-four hours after the start of a 7 h antigen challenge, adherence of unstimulated neutrophils from COPD-susceptible horses increased from 2.5 (0.5-4.1)% and 3.4 (0.6-6.6)% to 19.6 (16.9-20.3)% and 21.8 (10.6-23.1)% adherence for cells in medium containing 0.1% or 0.2% BSA, respectively; (median [range]; n = 4). Adherence of cells from normal horses remained unchanged. Addition of an anti-CD18 monoclonal antibody, H20A, inhibited the increase in adherence at 24 h by 96 (45-100)%, n = 3. The percentage of neutrophils in bronchoalveolar lavage fluid at 24 h increased from 1 (0-2) to 80 (65-94), (median (range), n = 4). These results suggest that antigen challenge results in exposure of circulating equine neutrophils to one or more factors that prime, or activate, these cells, which may enhance their recruitment to the lungs. Inhibition of circulating neutrophil activation may therefore represent a therapeutic target. 相似文献
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Four experiments using weight gain, feed efficiency and carcass analysis criteria were conducted with 148 pigs to determine the effects of feeding nicotine sulfate at various levels on protein and fat deposition. A level of 5 p.p.m. of nicotine sulfate in the ration fed to pigs from weaning until market weight significantly decreased (P<.05) the depth of loin fat in two of three experiments in which it was tested and slightly increased the carcass protein: fat ratio in all experiments. A level of 20 p.p.m. was as effective as 5 p.p.m. but higher levels of 40 and 80 p.p.m. had no effect on carcass quality. The fat content of the livers of pigs fed 5 p.p.m. of nicotine sulfate was found to be 8 to 10 per cent higher than that of controls in the two experiments in which it was measured. Higher levels of nicotine had little or no effect on liver lipids. Plasma cholesterol levels of pigs were not increased by the feeding of nicotine sulfate at levels of 5, 20 and 80 p.p.m. 相似文献
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Three Australian isolates of chicken anaemia agent (CAA) resisted treatment at 70 degrees C for 5 min and chloroform treatment. Although minor antigenic differences were detected using monoclonal antibodies to CAA, the Australian isolates were indistinguishable from the reference Cux-1 and Gifu-1 isolates in cross-immunofluorescence and cross-neutralisation tests employing polyclonal chicken antiserums. The Australian viruses were pathogenic for intramuscularly inoculated 1-day-old SPF chicks, but were less pathogenic for 7-day-old chicks. Thus the Australian isolates of CAA did not differ significantly in these properties from previously characterised CAA isolates from other continents. 相似文献
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D. B. Lindenmayer R. B. Cunningham M. T. Tanton A. P. Smith H. A. Nix 《Forest Ecology and Management》1991,40(3-4):289-308
A total of 1125 hollow-bearing trees was observed for the presence of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia. Different species of arboreal marsupials exhibited preferences for hollow-bearing trees with different characteristics. Gymnobelideus leadbeateri (Leadbeater's possum) selected short, fat trees with numerous holes and a large quantity of dense surrounding vegetation. Very large hollow-bearing trees were favoured as nest sites by Petauroides volans. Petaurus breviceps preferred trees with a large number of fissures, whereas trees favoured by Antechinus stuartii were tall and thin. Trees selected as nest sites by Trichosurus caninus were typically short and fat with few holes. Our results provide evidence of resource partitioning of hollow-bearing trees amongst arboreal marsupials. Clear-felling of montane ash forest on an 80–120-year rotation will have a highly detrimental effect on arboreal marsupials by substantially reducing the number and range of types of hollow-bearing trees required to support the complete diversity of species. The 80–120-year interval between logging operations will result in trees being harvested well before they develop characteristics which make them suitable nest sites for arboreal marsupials. 相似文献
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Voluntary culling on low milk yield and the economic returns for herds with a stable number of milk cows was investigated for spring calving dairy herds in the Republic of Ireland. The analysis was conducted at annual involuntary removal rates: 15, 20 and 25% and replacement costs as percent of beef value 94, 126, 157%. Varying cow replacement rate above involuntary removal rate by voluntary culling increased milk sold per cow in year 16 to a maximum of +5 to +10% after practicing a fixed strategy for 16 years. Greatest absolute and relative gains in yield occur from voluntary culling at the lowest involuntary replacement rate. Voluntary culling up to 3 to 8 percentage units above involuntary cow replacement rate maximizes economic returns per cow in herd when the market price for replacement heifers exceeds 150% of their beef value. Maximum voluntary culling may be practiced for prices near or below beef value. 相似文献