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   301篇
  免费   30篇
  国内免费   7篇
林业   6篇
农学   6篇
  1篇
综合类   23篇
农作物   2篇
水产渔业   44篇
畜牧兽医   250篇
植物保护   6篇
  2023年   5篇
  2022年   5篇
  2021年   15篇
  2020年   17篇
  2019年   20篇
  2018年   8篇
  2017年   15篇
  2016年   15篇
  2015年   14篇
  2014年   20篇
  2013年   19篇
  2012年   22篇
  2011年   18篇
  2010年   12篇
  2009年   21篇
  2008年   15篇
  2007年   8篇
  2006年   11篇
  2005年   5篇
  2004年   11篇
  2003年   9篇
  2002年   10篇
  2001年   7篇
  2000年   6篇
  1999年   2篇
  1998年   4篇
  1997年   1篇
  1996年   6篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1988年   1篇
  1979年   2篇
  1975年   1篇
  1974年   1篇
排序方式: 共有338条查询结果,搜索用时 187 毫秒
41.
虽然没有单一因素被证实与蜂群的大量损失有直接关系,但是新发及再发感染性病原对蜂群的下降起到了重要作用。蜜蜂丝状病毒(AmFV)首次于1978年鉴定感染于意大利蜜蜂,但是最近发现广泛存在于意大利蜜蜂及独居蜜蜂中,然而蜜蜂丝状病毒是否也存在于我国的中华蜜蜂及其他相关蜂种未见报道。为了深入理解AmFV的发生、流行及分布,本文检测了我国中华蜜蜂、熊蜂、黑小蜜蜂的样本,发现均不同程度感染了该病毒,其中黑小蜜蜂感染率最高,达80%,为深入开展病毒流行与传播提供了基础数据。  相似文献   
42.
部分地区奶牛腹泻粪便样中诺如病毒的检测和演化分析   总被引:1,自引:1,他引:0  
牛诺如病毒(bovine norovirus,BNoV)是一种引起犊牛腹泻的病原,目前已在19个国家检出。本研究旨在调查该病毒在国内部分地区的流行情况及分子特征。采用RT-PCR方法检测了5个省12个奶牛场的93份腹泻粪便样本和54份健康粪便样本。结果显示:腹泻样本中BNoV检出率为25.81%,极显著高于健康粪便样本中9.26%的检出率(P<0.01),证明该病毒与犊牛腹泻具有相关性;基于29个RdRp序列的遗传进化分析显示,5份样本为GIII.1型,24份样本为GIII.2型。对获得的18个VP1和13个VP2基因片段的遗传进化分析发现,中国的BNoV毒株具有独特的演化趋势。本研究证明BNoV已在国内的奶牛中广泛流行,是国内犊牛腹泻的新发病原,且国内的BNoV毒株具有独特的演化趋势,为犊牛腹泻的防控提供了重要参考。  相似文献   
43.
The exhibition swine at agricultural fairs provides a critical human–swine interface that allows for the bidirectional transmission of influenza A virus (IAV). Previous IAV surveillance at the end of fairs has resulted in frequent detection of IAV‐infected swine; little is known, however, about the frequency with which swine arrive at fairs already infected with IAV. We investigated the IAV prevalence among exhibition swine entering fairs to better understand the epidemiology of IAV in this unique human–swine interface. In 2014, snout wipes were collected from 3547 swine during the first day of nine agricultural exhibitions in Indiana and Ohio. Samples were screened for IAV using rRT‐PCR and positive samples were inoculated into cultured cells for virus isolation. The overall IAV prevalence detected among swine arriving at exhibitions was 5.3% (188/3547) via rRT‐PCR and 1.5% (53/3547) via virus isolation, with IAV being detected and recovered from swine at 5 of the 9 exhibitions. Within the fairs with IAV‐positive swine, the individual exhibition IAV prevalence ranged from 0.2% (1/523) to 34.4% (144/419) using rRT‐PCR and 0.2% (1/523) to 10.3% (43/419) with virus isolation. Single IAV subtypes were detected at three of the fairs but subtype diversity was detected among the pigs at two fairs as both H1N1 and H3N2 were recovered from incoming swine. At two of the exhibitions, a temporal relationship was observed between the order of the individual swine in sampling and the associated IAV rRT‐PCR results, indicating the fomite transmission of IAV through common contact surfaces may occur. With the knowledge that a small proportion of swine arrive at fairs shedding IAV, resources should be directed towards preventive strategies focused on limiting transmission during fairs to protect swine and humans during exhibitions.  相似文献   
44.
Hepatitis E has become an emerging infection in many European countries. We analysed the prevalence of hepatitis E virus (HEV) infection in selected population groups in Croatia. Overall HEV IgG seropositivity was 5.6%, while 1.9% participants showed IgM antibodies suggestive of recent infection. No IgM‐positive sample was positive for HEV RNA. HEV IgG antibodies were most prevalent in alcohol abusers (8.9%) and war veterans (8.6%), compared with 6.1% among injecting drug users and 2.7% in healthcare professionals. No individual with high‐risk sexual behaviour tested HEV seropositive. HEV IgG positivity increased significantly with age from 1.8% to 2.3% in individuals younger than 40 years to 11.3% in individuals older than 50 years (P = 0.023). The mean age of HEV‐positive participants was significantly higher than that of HEV‐negative participants (50.9 ± 11.8 years versus 41.2 ± 11.8 years, P = 0.008). Seroprevalence rates were significantly higher in residents of suburban and rural areas compared with residents of urban areas (14.5% versus 2.5%, P = 0.003). Additionally, an increasing prevalence of HEV IgG antibodies was observed from 1.8% in participants living in families with two household members to 12.1% in those living with more than four members (P = 0.046). Gender, marital status, educational level, sexual orientation, source of drinking water, history of blood transfusions, surgical procedures, tattooing and travelling were not associated with HEV seroprevalence. Logistic regression showed that living in suburban/rural areas was the main risk factor for HEV seropositivity (OR = 6.67; 95%CI = 1.89–25.0; AOR = 7.14, 95%CI = 1.89–25.0).  相似文献   
45.
Interpretation of the result of a diagnostic test depends not only on the actual test result(s) but also on information external to this result, namely the test's sensitivity and specificity. This external information (also called prior information) must be combined with the data to yield the so-called updated, posterior estimates of the true prevalence and the test characteristics. The Bayesian approach offers a natural, intuitive framework in which to carry out this estimation process. The influence of the prior information on the final result may not be ignored. Guidance for the choice of prior information not in conflict with the data can be obtained from a set of statistics and indices (DIC, p(D), Bayes-p).  相似文献   
46.
Qualitative and quantitative contamination of ready-to-eat food-stuffs with the pathogen Listeria monocytogenes was studied in 1586 samples collected from 103 supermarkets (n = 946) and 61 households (n = 640) in Vienna, Austria. Seventeen groups of ready-to-eat foods were classified into three risk categories for contamination (CP1-CP3). Three to four samples were randomly collected at the retail level from each CP. Regarding the households, the sampling procedure was started with food items of CP1, and if not available, was continued with sampling of food items of CP2 and finally of CP3. Additionally, 184 environmental samples (swabs from the kitchen area, dust samples from the vacuum cleaner) and faecal samples (household members and pet animals) were included. One-hundred and twenty-four (13.1%) and 45 (4.8%) samples out of 946 food samples collected from food retailers tested positive for Listeria spp. and L. monocytogenes, respectively, with five smoked fish samples exceeding the tolerated limit of 100 CFU/g food. Food-stuffs associated with the highest risk of contamination were twice as frequently contaminated with L. monocytogenes as food-stuffs associated with a medium risk of contamination. Products showing the highest contamination rate were fish and seafood (19.4%), followed by raw meat sausages (6.3%), soft cheese (5.5%) and cooked meat products/patés (4.5%). The overall contamination rate of foods collected at the household level was more than two times lower. Only 5.6% and 1.7% of 640 food-stuffs analysed tested positive for Listeria spp. and L. monocytogenes, respectively. However, CP1 foods were rarely collected. Pulsed-field gel electrophoresis (PFGE) typing of the collected L. monocytogenes isolates revealed a high degree of diversity between the isolates, with some exceptions. PFGE typing of isolates harvested from green-veined cheese revealed a match among strains, although the manufacturer seemed to be distinguishable. Typing of household strains revealed an epidemiological link within one family. In this case, food-stuffs and the kitchen environment were contaminated by an indistinguishable isolate. In addition, the same isolate was collected from a pooled faecal sample of the household members suggesting that consumption of even low contaminated food items (<100 CFU/g) results in Listeria shedding after the passage through the gut.  相似文献   
47.
The present study is the first conducted in Spain to estimate the bacteriological herd prevalence of Salmonella enterica in fattening units and to describe the Salmonella serovar diversity on these farms using a sample representative of the entire swine population. For this purpose, 10 faecal samples were collected from 10 different pens containing pigs close to market weight in a total of 232 fattening units. Total sample size was proportionally distributed according to the fattener census in each of the regions of the country and all the samples were examined by culture of 25 g of faecal material. One hundred (43.1%) farms had at least one Salmonella-positive sample (95% CI: 37-49.1%). Salmonella enterica was detected in 290 (12.5%) pooled faecal floor samples (95% CI: 11.2-13.8%). The apparent herd prevalence of salmonellosis was similar among multi-site, finishing and farrow to finish farms. Overall, 24 different serovars were identified, with S. Typhimurium, S. Rissen and S. Derby being the most common both at herd and sample level. Results of phage typing were available for the 91 isolates of S. Typhimurium. A total number of 10 different phage types were identified, with DT 193 being the most frequent. Phage types DT 104, DT 104b and DT U302, which have been associated with several multi-resistant patterns, accounted for 23% and 29% of the Typhimurium total isolates or Typhimurium infected farms respectively.  相似文献   
48.
An intermediate-technology pattern matching model and decision support system for veterinary diagnosis is described. Six diseases of cattle occurring in the tropics are used to illustrate the model. The pattern matching model is composed of a series of transparent overlays and a template. Each transparent overlay represents a sign state and contains sign frequency information for the diseases on the template. By superimposing multiple transparent overlays upon the disease template, a ranked list of differential diagnoses can be obtained. Ranking is by summation of disease sign frequencies. Modifications to accommodate observational uncertainty are presented. Disease prevalences can be represented in the model.  相似文献   
49.
50.
The marine leech, Zeylanicobdella arugamensis, is a major threat to aquaculture in grouper-producing countries including Indonesia. This study aimed at investigating prevalence, intensity and histopathology of the ectoparasite in humpback and hybrid groupers cultured in different rearing systems. A total of 260 groupers (60 humpback groupers and 200 hybrid groupers) were used for samples. The marine leech was observed on skin, fins, gills and mouth, followed by histopathological assay on the skin tissue. The results showed that prevalence of the leech in both groupers was higher when they were cultured in the floating net cages compared with the hatchery, p < .05. Furthermore, humpback grouper had a higher prevalence than hybrid grouper when they were cultured in a similar system, p < .05. Meanwhile, there was no significant difference in intensity between the two groupers, p > .05. Within the hybrid groupers, the highest prevalence was obtained from hybrid groupers reared in the earthen ponds. Histopathological studies showed that the infected groupers exhibited inflammation, congestion and erosion of the epidermis layer. Hybrid grouper had more severe histopathological lesions in the skin tissues. These results suggested that species and type of aquaculture system had significantly determined the prevalence, intensity and severity of lesion in Z. arugamensis infestation.  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