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   129篇
  免费   15篇
  国内免费   1篇
林业   2篇
农学   3篇
  9篇
综合类   16篇
农作物   1篇
水产渔业   4篇
畜牧兽医   93篇
园艺   1篇
植物保护   16篇
  2022年   1篇
  2021年   1篇
  2020年   4篇
  2019年   4篇
  2018年   5篇
  2017年   2篇
  2016年   7篇
  2015年   4篇
  2014年   3篇
  2013年   15篇
  2012年   4篇
  2011年   4篇
  2010年   5篇
  2009年   11篇
  2008年   6篇
  2007年   5篇
  2006年   4篇
  2005年   6篇
  2004年   2篇
  2003年   1篇
  2002年   9篇
  2001年   2篇
  2000年   4篇
  1999年   4篇
  1998年   5篇
  1997年   2篇
  1995年   8篇
  1994年   1篇
  1992年   1篇
  1990年   3篇
  1989年   3篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1978年   1篇
  1948年   1篇
  1941年   1篇
  1937年   1篇
排序方式: 共有145条查询结果,搜索用时 15 毫秒
71.
The urodynamic changes in 10 bitches up to 18 months after they had undergone ovariectomy were investigated. There were significant decreases in the maximum urethral closure pressure, the functional urethral length and the total integrated pressure profile 18 months after spaying, resulting in a caudal shift of the urethral profile, and a deterioration of urethral closure function. Each urethral pressure profile was divided into three equal sections; the mean cranial and middle integrated pressure decreased significantly and consistently over the 18-month observation period whereas the caudal integrated pressure increased.  相似文献   
72.
ABSTRACT

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status.

Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control.

Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only.

Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options.  相似文献   
73.
Fusarium graminearum causes important diseases of small-grain cereals and maize and produces several mycotoxins. Among them, deoxynivalenol (DON) and zearalenone (ZEA) can accumulate in feedstuffs and foods to health-threatening levels. Although DON is important for fungal virulence in wheat, disease severity in the field does not correlate with mycotoxin concentrations. We compared gene expression and mycotoxin production of lipase-deficient mutants (Δfgl1), strongly reduced in virulence, and the respective wild-type isolate. Δfgl1 mutants exhibited up-regulated DON production during wheat head infection. On isolated wheat kernels, DON was only produced in low quantities, but higher in wild-type than in Δfgl1 mutants. In contrast, neither wild-type nor Δfgl1 mutants produced ZEA during wheat head infection. However, ZEA was clearly detectable on wheat kernels. Here, Δfgl1 mutants revealed a dramatically enhanced ZEA production. We could correlate the altered amounts of DON and ZEA directly with the expression of the toxin-related genes Tri5 for DON and PKS4 and PKS13 for ZEA. Based on Tri5 expression and the infection pattern of the wild-type and Δfgl1 mutants, we suggest that the transition zone of rachilla and rachis is important in the induction of DON synthesis. Gene expression studies indicate an involvement of the lipase FGL1 in regulation of 8 PKS genes and ZEA production.  相似文献   
74.
Environmental exposure to metal appears to enhance susceptibility to Transmissible Spongiform Encephalopathies (TSEs); however, published data are not conclusive. The current study focuses on assessing the effects of copper depletion and/or manganese enhancement in the diet on susceptibility to Scrapie and this disease progression. The degree of spongiosis was the highest in the animals that received a copper‐ depleted diet. These observations suggest that this diet contributes to the Scrapie lesions and to the worsening of the condition in animals that have been inoculated with Scrapie. The highest intensities of GFAP immunostaining were also associated with the copper‐ depleted diet. Dietary supplementation with manganese had a negative effect on neuronal counts. In conclusion, this study demonstrates that certain environmental factors may aggravate neuropathological Scrapie lesions. This is consistent with reports from other neurodegenerative diseases where some metalloenzymes play a pivotal protector role against the oxidative stress associated with pathogenesis.  相似文献   
75.
76.
77.
Marine macroalgae are considered an untapped source of healthy natural metabolites and their market demand is rapidly increasing. Intertidal macroalgae present chemical defense mechanisms that enable them to thrive under changing environmental conditions. These intracellular chemicals include compounds that can be used for human benefit. The aim of this study was to test cultivation protocols that direct seaweed metabolic responses to enhance the production of target antioxidant and photoprotective biomaterials. We present an original integrated multi-trophic aquaculture (IMTA) design, based on a two-phase cultivation plan, in which three seaweed species were initially fed by fish effluents, and subsequently exposed to various abiotic stresses, namely, high irradiance, nutrient starvation, and high salinity. The combined effect of the IMTA’s high nutrient concentrations and/or followed by the abiotic stressors enhanced the seaweeds’ content of mycosporine-like amino acids (MAAs) by 2.3-fold, phenolic compounds by 1.4-fold, and their antioxidant capacity by 1.8-fold. The Sun Protection Factor (SPF) rose by 2.7-fold, and the chlorophyll and phycobiliprotein synthesis was stimulated dramatically by an order of magnitude. Our integrated cultivation system design offers a sustainable approach, with the potential to be adopted by emerging industries for food and health applications.  相似文献   
78.
79.
Plants recognize conserved molecular structures from microorganisms, which triggers active immune responses. Successful pathogens have to overcome this level of immunity; however, plants in turn can adapt their immune system, thus plants and pathogens are in an evolutionary arms race. As being sessile organisms, plants need to integrate and adapt to changing environmental conditions such as light, temperature, drought, or microorganisms. Plants protect themselves against diseases through sensitive recognition of potential pathogens and effective defense systems. The first level of the plant immune system provides recognition of a broad spectrum of microorganisms leading to defense activation (Bittel and Robatzek 2007). The second level of the plant immunity allows certain plant cultivars to detect of specific pathogen strains??a phenomenon also referred to as ??gene-for-gene resistance?? (Jones and Dangl 2006). The first level of immunity occurs rapidly and triggers active defenses normally without harm to the plant cell. The second level of plant immunity develops over days and deploys a local cell death, which prevents pathogens from further spread into tissues. In addition to these cell-autonomous defense systems, plants have also evolved strategies of systemic immunity.  相似文献   
80.
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