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   63篇
  免费   1篇
林业   12篇
基础科学   2篇
  9篇
综合类   10篇
农作物   2篇
畜牧兽医   21篇
园艺   5篇
植物保护   3篇
  2023年   1篇
  2022年   2篇
  2020年   2篇
  2019年   1篇
  2016年   1篇
  2015年   3篇
  2014年   2篇
  2013年   1篇
  2012年   8篇
  2011年   9篇
  2010年   3篇
  2009年   5篇
  2008年   8篇
  2007年   3篇
  2006年   8篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
  2002年   3篇
排序方式: 共有64条查询结果,搜索用时 15 毫秒
11.
12.
Silvicultural tools to develop irregular and diverse forest structures   总被引:2,自引:0,他引:2  
Schutz  Jean-Philippe 《Forestry》2002,75(4):329-337
  相似文献   
13.
OBJECTIVE: To evaluate the use of a human bladder tumor antigen test for diagnosis of lower urinary tract malignancies in dogs. SAMPLE POPULATION: Urine samples from dogs without urinary tract abnormalities (n = 18) and from dogs with lower urinary tract neoplasia (20) or nonmalignant urinary tract disease (16). PROCEDURE: Test results were compared among groups and among 3 observers. The effects of urine pH and specific gravity, degree of hematuria, and storage temperature and time of urine samples on test results were also assessed. RESULTS: Test sensitivity and specificity were 90 and 94.4%, respectively, for differentiating dogs with lower urinary tract neoplasia from dogs without abnormalities. However, specificity decreased to 35% for differentiating dogs with neoplasia from dogs with nonmalignant urinary tract disease. In dogs with neoplasia, results were significantly affected by degree of hematuria. However, addition of blood to urine from dogs without hematuria had no significant effect on test results. Although intraobserver variation was significant, urine pH, specific gravity, or storage time or temperature had no significant effect on results. CONCLUSIONS AND CLINICAL RELEVANCE: Although this bladder tumor antigen test was sensitive for differentiating dogs with malignancies of the lower urinary tract from dogs without urinary tract disease, it was not specific for differentiating dogs with neoplasia from dogs with other lower urinary tract abnormalities. It cannot, therefore, be recommended as a definitive diagnostic aid for the detection of lower urinary tract malignancies in dogs.  相似文献   
14.
15.
The HIV envelope (Env) protein gp120 is protected from antibody recognition by a dense glycan shield. However, several of the recently identified PGT broadly neutralizing antibodies appear to interact directly with the HIV glycan coat. Crystal structures of antigen-binding fragments (Fabs) PGT 127 and 128 with Man(9) at 1.65 and 1.29 angstrom resolution, respectively, and glycan binding data delineate a specific high mannose-binding site. Fab PGT 128 complexed with a fully glycosylated gp120 outer domain at 3.25 angstroms reveals that the antibody penetrates the glycan shield and recognizes two conserved glycans as well as a short β-strand segment of the gp120 V3 loop, accounting for its high binding affinity and broad specificity. Furthermore, our data suggest that the high neutralization potency of PGT 127 and 128 immunoglobulin Gs may be mediated by cross-linking Env trimers on the viral surface.  相似文献   
16.
Due to intensification and specialisation of animal production and the increasing pressure of environmental regulations, the careful management of animal wastes becomes a key point for the sustainability of livestock farming. This paper addresses the dynamic representation of a network composed by a set of production units (i.e., livestock farms) that need to transfer their wastes to a set of consumption units (i.e., crops onto which wastes may be spread over). The dynamics of stocks (taken as continuous fluxes with imprecise parameters) is combined with management decisions or actions (taken as discrete events). Various temporal constraints determine the possibilities of waste transfers. For each production or consumption unit, these constraints are modelled as a timed automaton. Possible allocation of wastes is then analysed using model-checking techniques applied to the global timed automaton resulting from the product of all the elementary timed automata. To this end, the Kronos software based on the Timed Computational Tree Logic (TCTL) is used. Our approach is illustrated through the analysis of a typical farming system made of livestock and crop enterprises in the context of the Reunion Island. Using the computer tool implementing this approach, we show how an initial waste management policy can be improved by simulation to find a better waste allocation to crops.  相似文献   
17.

'Sticky cotton' causes substantial economic loss in central Africa. The phenomenon is the result of honeydew excreted by sapsucking insects, mainly the aphid Aphis gossypii Glover. The chemical protection currently available to farmers does not limit this type of damage effectively. From exhaustive counting of infested leaves and quantitative measurement of stickiness with a thermodetector, a positive relationship can be established between the seriousness of fibre stickiness and aphid outbreaks at the end of the season. A control method involving the topping of plants after boll opening reduces the number of leaves on which aphids feed and thus the abundance of the aphids.  相似文献   
18.
The objectives of this study were to propose benchmarks for the interpretation of herd udder health using monthly individual somatic cell counts (SCC) from dairy herds in Quebec, Canada and to evaluate the association of risk factors with intramammary infection (IMI) dynamics relative to these benchmarks. The mean and percentiles of indices related to udder infection status [e.g., proportion of healthy or chronically infected cows, cows cured and new IMI (NIMI) rate] during lactation and over the dry period were calculated using a threshold of ≥ 200 000 cells/mL at test day. Mean NIMI proportion and proportion of cows cured during lactation were 0.11 and 0.27. Benchmarks of 0.70 and 0.03 for healthy and chronically infected cows over the dry period were proposed. Season and herd mean SCC were risk factors influencing IMI dynamics during lactation and over the dry period.  相似文献   
19.
Landscape Ecology - While the concept of ecosystem services (ES) is well established in the scientific and policy arenas, its operationalization faces many challenges. Indeed, ES supply, demand and...  相似文献   
20.
ABSTRACT: This study evaluated the effect of the probiotics Pediococcus acidilactici and Saccharomyces cerevisiae boulardii on the intestinal colonization of O149 enterotoxigenic Escherichia coli harbouring the F4 (K88) fimbriae (ETEC F4) and on the expression of ileal cytokines in weaned pigs. At birth, different litters of pigs were randomly assigned to one of the following treatments: 1) control without antibiotics or probiotics (CTRL); 2) reference group in which chlortetracycline and tiamulin were added to weanling feed (ATB); 3) P. acidilactici; 4) S. cerevisiae boulardii; or 5) P. acidilactici + S. cerevisiae boulardii. Probiotics were administered daily (1 × 109 CFU per pig) during the lactation period and after weaning (day 21). At 28 days of age, all pigs were orally challenged with an ETEC F4 strain, and a necropsy was performed 24 h later. Intestinal segments were collected to evaluate bacterial colonization in the small intestine and ileal cytokine expressions. Attachment of ETEC F4 to the intestinal mucosa was significantly reduced in pigs treated with P. acidilactici or S. cerevisiae boulardii in comparison with the ATB group (P = 0.01 and P = 0.03, respectively). In addition, proinflammatory cytokines, such as IL-6, were upregulated in ETEC F4 challenged pigs treated with P. acidilactici alone or in combination with S. cerevisiae boulardii compared with the CTRL group. In conclusion, the administration of P. acidilactici or S. cerevisiae boulardii was effective in reducing ETEC F4 attachment to the ileal mucosa, whereas the presence of P. acidilactici was required to modulate the expression of intestinal inflammatory cytokines in pigs challenged with ETEC F4.  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