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21.
22.
Risk factors for infection of sow herds with porcine reproductive and respiratory syndrome (PRRS) virus 总被引:10,自引:0,他引:10
Mortensen S Stryhn H Søgaard R Boklund A Stärk KD Christensen J Willeberg P 《Preventive veterinary medicine》2002,53(1-2):83-101
In 1992, the porcine reproductive and respiratory syndrome virus (PRRSV) of European type (PRRSV-EU) was introduced in Denmark. By 1996, the virus had spread to approximately 25% of the Danish herds. In January 1996, a modified-live vaccine based on the American type of the virus (PRRSV-US) was used in replacement boars for Danish artificial insemination (AI) centres and from July 1996, the vaccine was used in PRRSV-EU infected herds for prevention of disease. Soon after vaccine introduction, PRRSV non-infected herds experienced outbreaks of disease due to infection with PRRSV-US. In this study, we investigated the risk factors (biosecurity level, animals, exposure from PRRSV-US-infected neighbour herds, semen, herd size, pig density and herd density) for infection with PRRSV-US in a cohort of 1071 sow herds; we used a nested case-control study. The retrospective observation period lasted from June 1996 (when they all were non-infected) to October 1997. Seventy-three non-vaccinated, closed sow herds became infected with the vaccine strain during this period. Each case herd was matched with two control herds from the cohort (controls had not been infected at the time of infection in the case herds). The data were analysed using a Cox-regression model. The hazard of infection increased significantly with exposure from PRRSV-US-infected neighbouring herds, purchase of animals from herds incubating PRRSV-US infection, increasing herd size and purchase of semen from boars at PRRSV-US-infected AI centres. The results are consistent with the modified-live vaccine strain spread to other herds by trade with animals and semen and by neighbour (area) transmission. We suggest that virus spread by aerosols was a frequent mode of transmission. 相似文献
23.
Ludvig A. Krag Rene Holst Niels Madsen Kurt Hansen Rikke P. Frandsen 《Fisheries Research》2010,101(1-2):20-26
The critical condition of the North Sea cod stocks has resulted in restrictions on not only cod, but also haddock and other species that are caught together with cod. Thus full exploitation of the haddock stock is unachievable unless cod can be excluded from the haddock catch. We designed a selective trawl based on the behavioral differences between haddock and cod as they enter a trawl, i.e., cod stay close to the seabed whereas haddock rise above it. The trawl's fishing line is raised ~60 cm above the seabed to allow cod to escape beneath the trawl while haddock are retained. To collect the escapees, three sampling bags were attached beneath the raised fishing line. The selective haddock trawl reduced the total catch of cod by 55% during the day and 82% at night, and 99% of the marketable haddock was caught during the day and 89% at night. Cod escape rates were highly length dependent: smaller cod escaped the trawl in greater numbers than did larger individuals. Whiting, saithe, lemon sole, and plaice were included in the analysis. 相似文献
24.
Lena Kristensen Rikke Buhl Katarina Nostell Lars Bak Ellen Petersen Maria Lindholm Stine Jacobsen 《Canadian journal of veterinary research》2014,78(2):97-102
The purpose of the study was to investigate whether acute strenuous exercise (1600- to 2500-m race) would elicit an acute phase response (APR) in Standardbred trotters. Blood levels of several inflammatory markers [serum amyloid A (SAA), haptoglobin, fibrinogen, white blood cell count (WBC), and iron], muscle enzymes [creatinine kinase (CK) and aspartate transaminase (AST)], and hemoglobin were assessed in 58 Standardbred trotters before and after racing. Hemoglobin levels increased and iron levels decreased 12 to 14 h after racing and haptoglobin concentrations, white blood cell counts, and iron levels were decreased 2 and/or 7 d after racing. Concentrations of CK, AST, SAA, and fibrinogen were unaltered in response to racing.Acute strenuous exercise did not elicit an acute phase reaction. The observed acute increase in hemoglobin levels and decreases in haptoglobin and iron levels may have been caused by exercise-induced hemolysis, which indicates that horses might experience a condition similar to athlete’s anemia in humans. The pathogenesis and clinical implications of the hematological and blood-biochemical changes elicited by acute exercise in Standardbred trotters in the present study warrant further investigation. 相似文献
25.
26.
Louise Grau Nersting Sven Bode Andersen Roland von Bothmer Magne Gullord Rikke Bagger Jørgensen 《Euphytica》2006,150(3):327-337
Summary Genetic diversity in microsatellites and development of agronomical characters in Nordic oat cultivars (Avena sativa) from the 20th century, ranging from landraces to new cultivars, were studied. A clear development in agronomical characters has taken place in this period: Straw length has been reduced, harvest index has increased and heading date has declined. The persistent oat breeding effort in the northern part of the region was indicated by the data, since cultivars from this region showed higher harvest index. Also adaptation to shorter summers was apparent in cultivars from the most northern part of the area. When comparing cultivars released after 1940 to the landraces, the loss of diversity revealed for the agronomical characters was also indicated by the molecular data. This indicates that a more general loss of diversity has taken place in the period, possibly due to random factors during the breeding process (bottleneck effect). The reduction in diversity revealed by recent cultivars at an agronomical as well as a molecular level emphasises the importance of implementing a conservation strategy for older material in order to secure genetic diversity for future oat breeding efforts. 相似文献
27.
Mette E Fertner Rikke H Olsen Magne Bisgaard Henrik Christensen 《Acta veterinaria Scandinavica》2011,53(1):56
Background
Studies on transmission of Enterococcus faecalis among chickens during hatch have not been carried out so far. Information about vertical transmission and subsequent spreading and colonization of the cloacal mucosa through cloacal ''drinking'' during hatch are important to understand the epidemiology of E. faecalis infections. In the present investigation vertical transmission and subsequent spreading and colonization of the cloacal mucosa of chickens by E. faecalis through cloacal ''drinking'' were examined.Methods
Two different batches of layer chickens originating from 45 weeks old Brown and White Lohmann parents, respectively from the same farm were sampled in the hatcher. Isolates were confirmed to be E. faecalis by polymerase chain reaction (PCR) and further by multilocus sequence typing (MLST) to state their population structure and comparison made to sequence types previously obtained from chicken.Results
A total of 480 chickens were swabbed from the cloacae just after hatch and after 24 hours. A total of 101 isolates were confirmed as E. faecalis by a species specific PCR. The prevalence of E. faecalis increased from 14% at 0 h to 97% after 24 h for the Brown Lohmann chickens and from 0.5% to 23% for the White Lohmann flock. The 84 isolates analysed by MLST were distributed on 14 sequence types (ST). Three ST (401, 82 and 249) accounted for 64% of all isolates analysed by MLST after 24 h. ST 82 has previously been reported from amyloid arthropathy and other lesions in poultry.Conclusions
The present findings demonstrated a high potential of a few contaminated eggs or embryos to rapidly facilitate the spread of E. faecalis to almost all chickens during hatch. 相似文献28.
Stina Christensen Roland von Bothmer Gert Poulsen Lorenzo Maggioni Marianne Phillip Bente Anni Andersen Rikke Bagger Jørgensen 《Genetic Resources and Crop Evolution》2011,58(5):657-666
AFLP markers were used to characterize diversity and asses the genetic structure among 17 accessions of kale landraces, cultivars
and wild populations from Europe. The range of average gene diversity in accessions was 0.11–0.27. Several landraces showed
higher levels of diversity than the wild populations and one cultivar had the lowest diversity measures. The landraces that
were most genetically diverse were from areas where kales are known to be extensively grown, suggesting in situ conservation in these areas as a supplement to storage of seeds in gene banks. An analysis of molecular variance (AMOVA)
showed that 62% of the total variation was found within accessions. For most accessions, genetic distance was not related
to geographic distance. Similarities among accessions were probably not caused by recent gene flow since they were widely
separated geographically; more likely the relationship among them is due to seed dispersal through human interactions. Our
results indicate that a kale population found in a natural habitat in Denmark was probably not truly wild but most likely
an escape from a cultivated Danish kale that had subsequently become naturalized. 相似文献
29.
Ida Cecilie Jensen Rikke Reisner Hansen Christian Damgaard Joachim Offenberg 《Pest management science》2023,79(7):2415-2422
BACKGROUND
Ants can become efficient biocontrol agents in plantation crops as they prey on pest insects and may inhibit plant pathogens by excreting broad-spectrum antibiotics. However, ants also provide a disservice by augmenting attended honeydew producing homopterans. This disservice may be avoided by offering ants artificial sugar as an alternative to honeydew. Here we tested the effect of artificial sugar feeding on aphid abundance in an apple plot with wood ants (Formica polyctena, Förster), and tested the effect of ant presence on apple scab (Venturia inaequalis, Cooke) disease incidence.RESULTS
Over a 2-year period, sugar feeding eliminated ant-attended aphid populations on the apple trees. Furthermore, scab symptoms on both leaves and apples were reduced considerably on ant trees compared to control trees without ants. The presence of ants on the trees reduced leaf scab infections by 34%, whereas spot numbers on fruits were reduced by between 53 and 81%, depending on apple variety. In addition, the spots were 56% smaller.CONCLUSION
This shows that problems with wood ant-attended homopterans can be solved and that ants can control both insect pests and plant pathogens. We therefore propose wood ants as a new effective biocontrol agent suitable for implementation in apple orchards and possibly other plantation crops. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献30.
Rikke W Larsen Matti Kiupel Hans-J?rg Balzer J?rgen S Agerholm 《Acta veterinaria Scandinavica》2015,57(1)