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   805篇
  免费   47篇
  国内免费   1篇
林业   20篇
农学   27篇
基础科学   2篇
  57篇
综合类   84篇
农作物   38篇
水产渔业   54篇
畜牧兽医   522篇
园艺   9篇
植物保护   40篇
  2022年   7篇
  2021年   11篇
  2020年   12篇
  2019年   8篇
  2018年   10篇
  2017年   5篇
  2016年   15篇
  2015年   12篇
  2014年   10篇
  2013年   33篇
  2012年   26篇
  2011年   34篇
  2010年   20篇
  2009年   17篇
  2008年   25篇
  2007年   25篇
  2006年   38篇
  2005年   39篇
  2004年   35篇
  2003年   26篇
  2002年   34篇
  2001年   24篇
  2000年   31篇
  1999年   24篇
  1998年   16篇
  1997年   13篇
  1996年   13篇
  1995年   9篇
  1994年   10篇
  1993年   7篇
  1992年   14篇
  1991年   18篇
  1990年   20篇
  1989年   10篇
  1988年   16篇
  1987年   11篇
  1986年   20篇
  1985年   16篇
  1983年   12篇
  1982年   7篇
  1979年   7篇
  1978年   5篇
  1975年   5篇
  1974年   6篇
  1973年   4篇
  1972年   9篇
  1971年   4篇
  1970年   7篇
  1968年   4篇
  1966年   5篇
排序方式: 共有853条查询结果,搜索用时 15 毫秒
181.
182.
The strategies used and the results obtained in Orkney's bovine viral diarrhoea virus (BVDV) eradication programme over eight years (2001 to 2008) are presented and discussed. The venture was undertaken by local veterinary practices and the Orkney Livestock Association (OLA) with the financial support of the Orkney Islands Council. Participation is voluntary; the programme comprises screening of youngstock, a whole-herd test if required, elimination of persistently infected animals and strict biosecurity measures and/or vaccination. BVDV-free herds are certified, and certification is updated annually by retesting the youngstock. The programme aims to minimise economic losses, thereby increasing the competitiveness of the Orcadian cattle industry and to improve animal health and welfare by eliminating virus circulation. Information from databases of the Scottish Agricultural College, Biobest Laboratories and OLA show that despite a significant reduction in the overall prevalence of BVDV on Orkney during the initial stages of the eradication programme, there has been little progress made since 2006 and that some difficulties have been encountered, with herd BVDV breakdowns following initial eradication. These results highlight the need for continued motivation of farmers, strict application of biosecurity measures and/or systematic vaccination of all seronegative breeding animals.  相似文献   
183.
A 6‐year‐old castrated dromedary camel (Camelus dromedarius) presented with a non‐healing, severely pruritic, ulcerative fibrotic plaque located at the medial canthus. Histological examination of surgical biopsies identified degenerating nematode larvae within eosinophilic granulomas. Treatment involved repeated debridement of the lesion, injectable ivermectin and anti‐inflammatory therapies, and injectable and topical antibiotics . A specially constructed mask with goggles to prevent the camel from continuing to self‐traumatize the eye and lesion was also placed. Full recovery occurred approximately 1 month after diagnosis. Because of the location of the lesion, time of year, the gross and microscopic characteristics of the lesion, the presence of a likely nematode larva and the response to treatment, a diagnosis of cutaneous habronemiasis was made.  相似文献   
184.
新疆褐牛体尺性状指标与体重的主成分分析   总被引:3,自引:1,他引:2  
选择30头18月龄左右新疆褐牛进行体尺、体重测定,选择累计贡献率达89.505%的7个主成分进行分析。结果表明,新疆褐牛体尺指标尻长、腰角宽、髋宽、坐骨宽及体重的变异较大,选育潜力大;体重与体斜长、胸围、腰角宽、髋宽等指标存在极显著相关(P<0.01),与管围呈显著相关(P<0.05);从主成分的特征根与累计贡献率来看,第1至第3主成分起主导作用的第1主成分主要反映体型外貌特征,第2主成分主要反映尻部特征,第3主成分主要反映后躯特征。  相似文献   
185.
利用水提法制备绿茶、乌龙茶、红茶、青砖茶和普洱茶提取物,研究5种提取物对体外小肠Caco-2细胞吸收葡萄糖的抑制效果。结果表明:在相同质量浓度(0.5mg/mL)条件下,5种茶叶提取物均能抑制Caco-2细胞吸收葡萄糖的活性,抑制能力大小依次为绿茶!乌龙茶!红茶!青砖茶!普洱茶;与对照相比,绿茶、乌龙茶、红茶和青砖茶提取物极显著抑制葡萄糖的吸收,但普洱茶提取物的抑制效果并未达到显著水平(P>0.05)。茶叶提取物抑制小肠Caco-2细胞吸收葡萄糖的能力可能与加工过程中儿茶素的转化有关。  相似文献   
186.
Technologies that increase the efficiency and sustainability of food animal production to provide meat for a growing population are necessary and must be used in a manner consistent with good veterinary practices, approved labeled use, and environmental stewardship. Compounds that bind to beta-adrenergic receptors (β-AR), termed beta-adrenergic receptor ligands (β-ligands), are one such technology and have been in use globally for many years. Though all β-ligands share some similarities in structure and function, the significance of their structural and pharmacological differences is sometimes overlooked. Structural variations in these molecules can affect absorption, distribution, metabolism, and excretion as well as cause substantial differences in biological and metabolic effects. Several β-ligands are available for use specifically in cattle production. Ractopamine and zilpaterol are beta-adrenergic agonists approved to increase weight gain, feed efficiency, and carcass leanness in cattle. They both bind to and activate β1- and β2-AR. Lubabegron is a newly developed selective beta-adrenergic modulator with unique structural and functional features. Lubabegron displays antagonistic behavior at the β1- and β2-AR but agonistic behavior at the β3-AR. Lubabegron is approved for use in cattle to reduce ammonia emissions per unit of live or carcass weight. Additionally, lubabegron can withstand prolonged use as the β3-AR lacks structural features needed for desensitization. Due to these unique features of lubabegron, this new β-ligand provides an additional option in cattle production. The individual properties of each β-ligand should be considered when making risk management decisions, as unique properties result in varying human food safety profiles that can determine appropriate safe β-ligand use.  相似文献   
187.
ABSTRACT: Experimental infections of Sminthopsis crassicaudata, the fat-tailed dunnart, a carnivorous marsupial widely distributed throughout the arid and semi-arid zones of Australia, show that this species can act as an intermediate host for Neospora caninum. In contrast to existing models that develop relatively few N. caninum tissue cysts, dunnarts offer a new animal model in which active neosporosis is dominated by tissue cyst production. The results provide evidence for a sylvatic life cycle of N. caninum in Australia between marsupials and wild dogs. It establishes the foundation for an investigation of the impact and costs of neosporosis to wildlife.  相似文献   
188.
The purpose of this report is to describe the clinical course and pathological findings in a horse admitted to the emergency service of the University of Georgia Large Animal Teaching Hospital for evaluation of colic, fever and diarrhoea of several days' duration. A presumptive historical diagnosis of colitis was made initially, but, due to the lack of faecal output during the first 12 h of hospitalisation and subsequent examination findings, an impaction of the ascending colon was suspected. Initial therapy consisted of rehydration with oral fluids and management of the abdominal pain with analgesic therapy. The horse did not respond to medical therapy and because of signs of persistent abdominal pain and financial constraints, the owner elected euthanasia after several days of supportive care. At necropsy, the horse was diagnosed with a colocolic intussusception.  相似文献   
189.
190.
A 12-month study was conducted to assess and monitor gastrointestinal tract nematodes and liver fluke in cohorts of cattle on a Scottish organic dairy farm. Various diagnostic markers for helminth parasites of cattle from different age groups were assessed monthly from April 2007 to March 2008. First season grazing stock were subjected to significant challenge from Ostertagia ostertagi nematodes as reflected in serum pepsinogen concentrations, which rose markedly in the second half of the grazing season. In addition, plasma albumin concentrations decreased and faecal egg counts (FEC) increased moderately, indicating exposure to both O ostertagi and probably Cooperia oncophora. Second season grazing animals had a peak FEC early in the grazing period, suggestive of a potential carry-over of Ostertagia species infection ('Type 2') during housing. All classes of cattle showed evidence of fluke (Fasciola hepatica) infection. Adult cow exposure to O ostertagi and fluke was estimated via the use of ELISA testing to detect antibodies to O ostertagi and F hepatica and the high levels detected suggested a significant exposure response. Despite low stocking densities and sympathetic grazing management, there was a significant challenge to all grazing stock from gastrointestinal nematodes and liver fluke.  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