首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   49篇
  免费   0篇
林业   5篇
  12篇
综合类   5篇
农作物   3篇
水产渔业   1篇
畜牧兽医   18篇
园艺   2篇
植物保护   3篇
  2021年   1篇
  2020年   1篇
  2017年   1篇
  2015年   1篇
  2014年   2篇
  2013年   5篇
  2012年   3篇
  2011年   6篇
  2010年   1篇
  2009年   1篇
  2008年   3篇
  2007年   3篇
  2006年   2篇
  2005年   1篇
  2003年   1篇
  2002年   1篇
  2001年   2篇
  2000年   4篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1989年   1篇
  1987年   1篇
  1983年   1篇
  1973年   1篇
  1965年   2篇
排序方式: 共有49条查询结果,搜索用时 15 毫秒
11.
Information about disease management in winter wheat (Triticum aestiva) in eight European countries was collated and analysed by scientists and extension workers within the European Network for the Durable Exploitation of Crop Protection Strategies (ENDURE). This included information about specific disease thresholds, decision support systems, host varieties, disease prevalence and pathogen virulence. Major differences in disease prevalence and economic importance were observed. Septoria tritici blotch (Mycosphaerella graminicola) was recognized as the most yield reducing disease in countries with intensive wheat production, but also rust diseases (Puccinia striiformis and Puccinia triticina), powdery mildew (Blumeria graminis) and Fusarium head blight (Fusarium spp.) were seen as serious disease problems. Examples of current integrated pest management (IPM) strategies in different countries have been reported. Disease management and fungicide use patterns showed major differences, with an average input equivalent to 2.3 full dose rates (TFI) in the UK and a TFI of 0.6 in Denmark. These differences are most likely due to a combination of different cropping systems, climatic differences, disease prevalence, and socio-economic factors. The web based information platform www.eurowheat.org was used for dissemination of information and results including information on control thresholds, cultural practices which can influence disease attack, fungicide efficacy, fungicide resistance, and pathogen virulence, which are all elements supporting 1PM for disease control in wheat. The platform is open to all users. The target groups of EuroWheat information are researchers, advisors, breeders, and similar partners dealing with disease management in wheat.  相似文献   
12.
The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light ( approximately 515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 +/- 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.  相似文献   
13.

Background

The fox tapeworm Echinococcus multilocularis has foxes and other canids as definitive host and rodents as intermediate hosts. However, most mammals can be accidental intermediate hosts and the larval stage may cause serious disease in humans. The parasite has never been detected in Sweden, Finland and mainland Norway. All three countries require currently an anthelminthic treatment for dogs and cats prior to entry in order to prevent introduction of the parasite. Documentation of freedom from E. multilocularis is necessary for justification of the present import requirements.

Methods

The probability that Sweden, Finland and mainland Norway were free from E. multilocularis and the sensitivity of the surveillance systems were estimated using scenario trees. Surveillance data from five animal species were included in the study: red fox (Vulpes vulpes), raccoon dog (Nyctereutes procyonoides), domestic pig, wild boar (Sus scrofa) and voles and lemmings (Arvicolinae).

Results

The cumulative probability of freedom from EM in December 2009 was high in all three countries, 0.98 (95% CI 0.96-0.99) in Finland and 0.99 (0.97-0.995) in Sweden and 0.98 (0.95-0.99) in Norway.

Conclusions

Results from the model confirm that there is a high probability that in 2009 the countries were free from E. multilocularis. The sensitivity analyses showed that the choice of the design prevalences in different infected populations was influential. Therefore more knowledge on expected prevalences for E. multilocularis in infected populations of different species is desirable to reduce residual uncertainty of the results.  相似文献   
14.
Meat extracts with acid-soluble glycogen (macroglycogen) from M. longissmus dorsi of carriers and noncarriers of the PRKAG3 mutation (RN(-) and rn(+) genotype) were analyzed by both (1)H liquid-state NMR spectroscopy and a biochemical method. The (1)H NMR analysis revealed that shorter polymers (dimers, trimers, etc.) of α-1,4-linked glucose were generated 24-48 h post-mortem. This is not possible to elucidate with the biochemical method, by which only the total amount of hydrolyzed glucose residues is determined. The shorter polymers were primarily formed in carriers of the PRKAG3 mutation, suggesting different post-mortem glycogen degradation mechanisms in the two genotypes.  相似文献   
15.
A rapid quantitative method for the gas chromatographic determination of volatile fatty acids in aqueous media is described. It includes the use of formic acid for the elimination of “ghost peaks” and of iso-valeric acid as an internal standard. The method has been used for the examination of bovine rumen fluid and of silage.Statistical treatment of the result shows that the fluid from lactating cows has a significantly higher content of butyric acid than has the fluid from dry cows; such a difference could not be demonstrated as to acetic, propionic and valeric acid.Some experience from the determination of the volatile fatty acids in silage is also reported.  相似文献   
16.
Ferulic acid (FA) and para-coumaric acid (p-CA) may mediate the protective effects of whole-grain cereals against colon cancer. Therefore, the effects of FA and p-CA on the metabolic activity, proliferation, cell cycle phase distribution, and kinetics of the colonic endothelial tumor cell line Caco-2 was studied. Both compounds at 1500 microM decreased the number of cells to 43-75% of control after 2-3 days of treatment. Cell cycle phase distribution and cell cycle kinetics were determined by flow cytometric analysis after bromodeoxyuridine labeling. Each compound at 1500 microM decreased the proportion of cells in the G(1) phase and increased the proportion of cells in the S and G(2) phases. Treatment with 1500 microM FA significantly increased the length of the S phase, while p-CA did not. It was concluded that FA and p-CA inhibited cell proliferation by presumably affecting different cell cycle phases, and this warrants further investigations because this inhibition may be one explanation for the diet-related protection against cancer.  相似文献   
17.
In this study, we investigate how metabolic fingerprints are related to temperature. Six common northern temperate diatoms (Attheya longicornis, Chaetoceros socialis, Chaetoceros furcellatus, Porosira glacialis, Skeletonema marinoi, and Thalassiosira gravida) were cultivated at two different temperatures, 0.5 and 8.5 °C. To exclude metabolic variations due to differences in growth rates, the growth rates were kept similar by performing the experiments under light limited conditions but in exponential growth phase. Growth rates and maximum quantum yield of photosynthesis were measured and interpreted as physiological variables, and metabolic fingerprints were acquired by high-resolution mass spectrometry. The chemical diversity varied substantially between the two temperatures for the tested species, ranging from 31% similarity for C. furcellatus and P. glacialis to 81% similarity for A. longicornis. The chemical diversity was generally highest at the lowest temperature.  相似文献   
18.
Infection with Brucella canis has been diagnosed in Sweden for the first time. It was diagnosed in a three-year-old breeding bitch with reproductive disturbances. Fifteen in-contact dogs were tested repeatedly and all of them were negative for B. canis. The source of infection could not be defined. The present article describes the case and the measures undertaken and gives a short review over B. canis. Recommendations on how to avoid the infection in non-endemic countries are given.  相似文献   
19.
Milberg  Hallgren  & Palmer 《Weed Research》2000,40(3):311-321
Data were analysed on weed biomass from untreated plots in 2672 field experiments conducted in spring- and autumn-sown cereal and oilseed crops in Sweden 1972–1992. The coefficient of variation (CV) among years in the biomass of annual weeds per square metre was 29% in autumn-sown crops. In spring-sown crops, which had less weed biomass, the corresponding value was 49%. The biomass of summer annuals varied most (105%). Low winter temperatures seemed to increase the biomass of weeds in autumn-sown crops. In spring-sown crops, weed biomass production was higher in years with high rainfall during late spring. Partial ordination (pCCA) of weed data indicated that the interannual variations in autumn-sown crops were mainly manifested by the occurrence of summer annuals. Results from similar ordination of data from spring-sown crops were partly explained by the occurrence of winter annuals.  相似文献   
20.
Acute lymphoblastic leukemic cells with T (thymus-derived) lymphocyte markers   总被引:14,自引:0,他引:14  
Five of nine children with acute lymphoblastic leukemia had lymphoblasts that bound sheep erythrocytes or reacted with antiserum to thymocytes, suggesting involvement of T (thymus-derived) cells. When lymphoblasts from all patients were examined by immunofluorescence they were found to lack a marker for B (bone marrow or bursa-equivalent) cells, that is, the presence of surface immunoglobulins.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号