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41.
The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae 总被引:1,自引:0,他引:1
The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point. 相似文献
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The acute toxicity for sheep of 3 alkaloids that occur in Phalaris acquatica was examined by intravenous and oral administration. The lowest tested dose rates that produced clinically observed signs were, for 5-methoxy dimethyltryptamine, 0.1 mg/kg body weight intravenously and 40 mg/kg orally; for gramine, 10 mg/kg intravenously and 500 mg/kg orally; and for hordenine, 20 mg/kg intravenously and 800 mg/kg orally. All induced the clinical signs observed in the nervous form of phalaris toxicity, but none induced the cardiac, sudden death, syndrome. 相似文献
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Temporal change in fragmentation of continental US forests 总被引:1,自引:0,他引:1
James D. Wickham Kurt H. Riitters Timothy G. Wade Collin Homer 《Landscape Ecology》2008,23(8):891-898
Changes in forest ecosystem function and condition arise from changes in forest fragmentation. Previous studies estimated
forest fragmentation for the continental United States (US). In this study, new temporal land-cover data from the National
Land Cover Database (NLCD) were used to estimate changes in forest fragmentation at multiple scales for the continental US.
Early and late dates for the land-cover change data were ca. 1992 and ca. 2001. Forest density was used as a multi-scale index
of fragmentation by measuring the proportion of forest in neighborhoods ranging in size from 2.25 to 5314.41 ha. The multi-scale
forest density maps were classified using thresholds of 40% (patch), 60% (dominant), and 90% (interior) to analyze temporal
change of fragmentation. The loss of dominant and interior forest showed distinct scale effects, whereas loss of patch forest
was much less scale-dependent. Dominant forest loss doubled from the smallest to the largest spatial scale, while interior
forest loss increased by approximately 80% from the smallest to the second largest spatial scale, then decreased somewhat.
At the largest spatial scale, losses of dominant and interior forest were 5 and 10%, respectively, of their ca. 1992 amounts.
In contrast, patch forest loss increased by only 25% from the smallest to largest spatial scale. These results indicate that
continental US forests were sensitive to forest loss because of their already fragmented state. Forest loss would have had
to occur in an unlikely spatial pattern in order to avoid the proportionately greater impact on dominant and interior forest
at larger spatial scales. 相似文献
47.
LJ DEPIAZZI WD ROBERTS CD HAWKINS MA PALMER DR PITMAN NC MCQUADE PD JELINEK DJ DEVEREAUX RJ RIPPON 《Australian veterinary journal》1998,76(1):32-38
Objective To test the hypothesis that ovine footrot associated with a thermostable protease strain of Dichelobacter nodosus undergoes self cure or is sustained as an annually recurring disease, depending on the environment.
Design and procedure Forty Merino sheep from a single blood line were infected with a protease thermostable strain of D nodosus a t each of five sites in Western Australia. Footrot lesions and microscopic evidence of D nodosus were recorded every fortnight for 2.5 years, supplemented by laboratory culture. Rainfall, soil and air temperature, pasture quantity and composition and soil types were also recorded. Flocks that apparently self cured were relocated to a more favourable site for footrot in the final spring season.
Results The maximum prevalence of feet with clinical footrot lesions was 80.6, 1.3, 14.4, 3.8 and 88.1% at the five sites. Severe footrot occurred for three consecutive spring seasons at one site that had clay loam soil and at least 3500 kg/ha total pasture dry matter annually. However, the infection was asymptomatic for up to 10 weeks between outbreaks. D nodosus was isolated from flocks for 2.5 years at only two sites, although there was microscopic evidence of the organism at other sites in the final year. A thermolabile variant (strain U6) of D nodosus was isolated from the two sites where footrot persisted.
Conclusion Depending on time and location, ovine footrot induced by a protease thermostable strain of D nodosus either self cured or persisted as annual outbreaks interspersed with periods of asymptomatic infection. 相似文献
Design and procedure Forty Merino sheep from a single blood line were infected with a protease thermostable strain of D nodosus a t each of five sites in Western Australia. Footrot lesions and microscopic evidence of D nodosus were recorded every fortnight for 2.5 years, supplemented by laboratory culture. Rainfall, soil and air temperature, pasture quantity and composition and soil types were also recorded. Flocks that apparently self cured were relocated to a more favourable site for footrot in the final spring season.
Results The maximum prevalence of feet with clinical footrot lesions was 80.6, 1.3, 14.4, 3.8 and 88.1% at the five sites. Severe footrot occurred for three consecutive spring seasons at one site that had clay loam soil and at least 3500 kg/ha total pasture dry matter annually. However, the infection was asymptomatic for up to 10 weeks between outbreaks. D nodosus was isolated from flocks for 2.5 years at only two sites, although there was microscopic evidence of the organism at other sites in the final year. A thermolabile variant (strain U6) of D nodosus was isolated from the two sites where footrot persisted.
Conclusion Depending on time and location, ovine footrot induced by a protease thermostable strain of D nodosus either self cured or persisted as annual outbreaks interspersed with periods of asymptomatic infection. 相似文献
48.
Fox LE Ford S Alleman AR Homer BL Harvey JW 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1993,22(3):89-92
Trimethoprim-sulfadiazine (TMP-SDZ) (Tribressin tablets 120 - 100 mg sulfadiazine, 20-mg trimethoprim [Coopers Animal Health, Inc., A Pitman-Moore Company, Mundelein, Ill.]) is a broad spectrum antibiotic combination effective in the treatment of bacterial pneumonia, urinary tract infections, pyoderma, meningitis, and prostatitis.(1) In clinical trials in puppies and adult dogs, TMP-SDZ was considered safe at both the manufacturer's recommended dose (15 mg/kg, b.i.d., or 30 mg/kg, u.i.d., per os for < 14 days(2)) and at 10 times that dose for 20 dayS.(3) Many infections, however, require prolonged high-dose therapy for resolution. The following study describes two cases of aplastic anemia and sepsis associated with intermittent, chronic (17-25 days), high-dose (25-30 mg/kg, b.i.d., per os) TMP-SDZ therapy recommended for the treatment of pyoderma.(4-7) 相似文献
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S Chakraborty R Knoche H Schulze DC Rubie D Dobson NL Ross RJ Angel 《Science (New York, N.Y.)》1999,283(5400):362-365
Rates of cation diffusion (magnesium, iron, and nickel) have been determined in olivine and its high-pressure polymorph, wadsleyite, at 9 to 15 gigapascals and 1100 degrees to 1400 degreesC for compositions that are relevant to Earth's mantle. Diffusion in olivine becomes strongly dependent on composition at high pressure. In wadsleyite, diffusion is one to two orders of magnitude faster than in olivine, depending on temperature. Homogenization of mantle heterogeneities (chemical mixing) and mineral transformations involving a magnesium-iron exchange will therefore occur considerably faster in the transition zone than at depths of less than 410 kilometers. 相似文献