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   7303篇
  免费   299篇
  国内免费   8篇
林业   300篇
农学   388篇
基础科学   85篇
  938篇
综合类   398篇
农作物   266篇
水产渔业   216篇
畜牧兽医   3969篇
园艺   117篇
植物保护   933篇
  2022年   42篇
  2021年   65篇
  2020年   86篇
  2019年   95篇
  2018年   109篇
  2017年   114篇
  2016年   120篇
  2015年   102篇
  2014年   138篇
  2013年   512篇
  2012年   332篇
  2011年   377篇
  2010年   203篇
  2009年   187篇
  2008年   358篇
  2007年   355篇
  2006年   302篇
  2005年   301篇
  2004年   311篇
  2003年   269篇
  2002年   263篇
  2001年   251篇
  2000年   226篇
  1999年   210篇
  1998年   58篇
  1997年   59篇
  1996年   63篇
  1995年   64篇
  1994年   44篇
  1993年   53篇
  1992年   112篇
  1991年   122篇
  1990年   143篇
  1989年   122篇
  1988年   109篇
  1987年   91篇
  1986年   73篇
  1985年   86篇
  1984年   73篇
  1983年   50篇
  1982年   37篇
  1981年   43篇
  1980年   47篇
  1979年   48篇
  1975年   32篇
  1974年   32篇
  1973年   33篇
  1972年   38篇
  1971年   41篇
  1969年   31篇
排序方式: 共有7610条查询结果,搜索用时 125 毫秒
961.
A good intake of fluids and essential nutrients in the first fourteen days is of vital importance to recuperating animals. Moreover, it is important to encourage cats and dogs to eat after illness or surgery, in order to promote optimal functioning of the gut and the immune system. Enteral nutrition is to be preferred to nasogastric feeding or parenteral nutrition. In the first stage of recovery, during the first 24 to 48 hours, it is important to feed the gut' with nutrients, and thereafter, in the second stage of recovery (after day 3), the calorie intake can be increased. Timely nutritional support with nutraceuticals, such as arginine, glutamine, taurine, long-chain polyunsaturated omega-3 fatty acids, and prebiotic fibres, can considerably shorten the recovery period of cats and dogs after illness or surgery  相似文献   
962.
963.
964.
965.
CKRD     
Boersma A  van Look W 《Tijdschrift voor diergeneeskunde》2012,137(5):341; discussion 341
  相似文献   
966.
967.
The economic losses due to porcine reproductive and respiratory syndrome virus (PRRSv) outbreaks are reported in the literature to be substantially high, but recent figures are not available. The aim of this study was to quantify the economic effects of epidemic PRRSv outbreaks in Dutch sow herds. Nine sow herds were selected based on a confirmed PRRSv outbreak within those populations. The economic impact during the first 18 weeks after the outbreak was estimated by comparing the overall costs between pre- and postoutbreak periods, using different factors (production data, medication, diagnostics, labour, etc.). An outbreak of PRRSv resulted in a reduced number of sold pigs per sow of 1.7. The economic loss varied between €59 and €379 for one sow per 18-week period outbreak. The mean loss per sow per outbreak was €126. The costs after the outbreak varied significantly from €3 to 160 per sow, due to the different methods used by farmers to tackle PRRSv outbreaks. The calculated costs in this study correlate with the costs of the initial outbreak in The Netherlands of 98 per sow.  相似文献   
968.
A novel, recombinant myxoma virus-rabbit haemorrhagic disease virus (RHDV) vaccine has been developed for the prevention of myxomatosis and rabbit haemorrhagic disease (RHD). A number of laboratory studies are described illustrating the safety and efficacy of the vaccine following subcutaneous administration in laboratory rabbits from four weeks of age onwards. In these studies, both vaccinated and unvaccinated control rabbits were challenged using pathogenic strains of RHD and myxoma viruses, and 100 per cent of the vaccinated rabbits were protected against both myxomatosis and RHD.  相似文献   
969.
970.
Since July 2007, Belgium has implemented a national surveillance and control program for Salmonella in pigs. Pig farms are designated as Salmonella high risk farms based on serological profiles and are obliged to subsequently take part in a Salmonella specific action plan (SSAP). The SSAP was evaluated and potential risk factors for the persistence of Salmonella on the farm were investigated. First, the Kaplan-Meier method was used in order to study the period during which a farm maintains a Salmonella high risk status. Farms recovered more slowly from their high risk status before the SSAP was implemented compared to after the program was implemented (p<0.001). However, results showed that 29% of the farms were withdrawn from the program possibly only because of sampling error. The program should thus be adapted to accommodate for this. Secondly, the influence of several risk factors (type of farm, season of entrance into the SSAP, size of farm and farm density of the municipality) on the time to withdrawal from the high risk status was evaluated using univariable methods and a Cox multiple regression model for survival data. A statistically significant association was identified between the type of farm and the time to withdrawal from the high risk status. At any point in time after the onset of the SSAP, withdrawals from the high risk status occurred at a 39% and 28% higher rate in mixed (p=0.01) and fattening farms (p=0.05), respectively, compared to closed farms. The risk attributed to closed pig farms is related to the presence of sows in this particular type of structure, which underlines the importance of implementing control measures in this category of animals.  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