全文获取类型
收费全文 | 30808篇 |
免费 | 361篇 |
国内免费 | 163篇 |
专业分类
林业 | 1072篇 |
农学 | 258篇 |
基础科学 | 73篇 |
4423篇 | |
综合类 | 6929篇 |
农作物 | 1004篇 |
水产渔业 | 316篇 |
畜牧兽医 | 16234篇 |
园艺 | 159篇 |
植物保护 | 864篇 |
出版年
2022年 | 45篇 |
2015年 | 56篇 |
2014年 | 91篇 |
2013年 | 77篇 |
2012年 | 2584篇 |
2011年 | 3059篇 |
2010年 | 627篇 |
2009年 | 417篇 |
2008年 | 2428篇 |
2007年 | 2549篇 |
2006年 | 2372篇 |
2005年 | 2357篇 |
2004年 | 2129篇 |
2003年 | 2085篇 |
2002年 | 1796篇 |
2001年 | 1237篇 |
2000年 | 1578篇 |
1999年 | 670篇 |
1998年 | 113篇 |
1997年 | 99篇 |
1996年 | 87篇 |
1995年 | 119篇 |
1994年 | 177篇 |
1993年 | 247篇 |
1992年 | 219篇 |
1991年 | 244篇 |
1990年 | 240篇 |
1989年 | 205篇 |
1988年 | 269篇 |
1987年 | 256篇 |
1986年 | 223篇 |
1985年 | 234篇 |
1984年 | 209篇 |
1983年 | 189篇 |
1982年 | 156篇 |
1981年 | 140篇 |
1980年 | 90篇 |
1979年 | 59篇 |
1976年 | 45篇 |
1975年 | 57篇 |
1974年 | 52篇 |
1973年 | 43篇 |
1969年 | 51篇 |
1966年 | 49篇 |
1963年 | 68篇 |
1960年 | 51篇 |
1959年 | 42篇 |
1958年 | 41篇 |
1957年 | 42篇 |
1956年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Cannas da Silva J Noordhuizen JP Vagneur M Bexiga R Gelfert CC Baumgartner W 《The Veterinary quarterly》2006,28(1):23-32
The nature of veterinary work in dairy health management in Europe has changed over the past years and will change even more dramatically in the near future. The consumers and the media show increasing concern about animal welfare, safety of products of animal origin and traceability of animal products. Farmers in Europe have to produce under strict, often expensive and laborious regulations, while still commercially competing with farmers outside the EU and not subject to the same rules. Veterinarians should adapt their knowledge and skills to the new challenges and developments of the dairy sector. Dairy farmers nowadays ask for support in areas that go beyond clinical activities: environmental protection, welfare, nutrition, grassland management, economics and business management. Bovine practitioners should be able to advise in many different areas and subjects--that is the challenge to our profession. Veterinary education with regards to cattle health management should start with individual animal clinical work, which constitutes the basis of herd health advisory programmes. The bovine practitioner should then look beyond that and regard the herd as the unit. Each diseased cow or group of cows should be detected early enough to avoid financial losses or such losses should be prevented altogether by detecting and managing risk factors contributing to disease occurrence. Herd health and production management programmes represent the first level to optimise dairy farm performance. Expansions to that should further be considered, comprising both animal health and welfare issues, as well as food safety and public health issues. The latter could be addressed by quality risk management programmes following the HACCP-principles. Cattle veterinarians should follow recent developments and invest in new skills and knowledge in order to maintain their usefulness to the modern dairy farmer. Finally we are convinced that the cattle practitioner should evolve into this direction, otherwise the veterinarian as we know him will miss the train in the next years. 相似文献
63.
Wagner M Melzner D Bagò Z Winter P Egerbacher M Schilcher F Zangana A Schoder D 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2005,52(6):278-283
We report the results of clinical and microbiological investigations on Listeria monocytogenes infections in a flock of 55 sheep and describe the implications for the safety of the raw milk and raw-milk cheeses produced in the on-farm dairy. The outbreak was caused by feeding grass silage, which was contaminated with 5 log10 CFU L. monocytogenes/g. Clinically, although having been fed from the same batch of silage, abortive (nine ewes), encephalitic (one ewe) and septicaemic (four ewes) forms of listeriosis were observed during the outbreak phase. As the starting point of feeding the contaminated silage was known we could calculate an incubation period of 18+/-2 and 26 days for the abortive and the encephalitic form of listeriosis, respectively. Pathologically, the septicaemic cases suffered from Listeria accumulation at comparable numbers in visceral organs but not in the brain. Only a single ewe developed central nervous symptoms and a rhomb-encephalitis was immunohistologically confirmed. In this case the infection proceeded from the nasal mucosa into the brain, with no infections of the liver, spleen and other visceral organs. Sampling of the cheese production chain, the farm environment and the persons living at the farm revealed the exposure of a farm-worker to an isolate genetically indistinguishable from the outbreak clone, obviously through the consumption of faecally contaminated bovine raw milk. The cheese under processing was free of Listeria because, as a result of intensive consultations, the farmer ensured a proper acidification of the cheese. The epidemiological findings suggest that food safety matters should be assessed in any case where infection of food-producing animals with potential human pathogens is observed. 相似文献
64.
65.
ABSTRACT: The control of highly infectious diseases of livestock such as classical swine fever, foot-and-mouth disease, and avian influenza is fraught with ethical, economic, and public health dilemmas. Attempts to control outbreaks of these pathogens rely on massive culling of infected farms, and farms deemed to be at risk of infection. Conventional approaches usually involve the preventive culling of all farms within a certain radius of an infected farm. Here we propose a novel culling strategy that is based on the idea that farms that have the highest expected number of secondary infections should be culled first. We show that, in comparison with conventional approaches (ring culling), our new method of risk based culling can reduce the total number of farms that need to be culled, the number of culled infected farms (and thus the expected number of human infections in case of a zoonosis), and the duration of the epidemic. Our novel risk based culling strategy requires three pieces of information, viz. the location of all farms in the area at risk, the moments when infected farms are detected, and an estimate of the distance-dependent probability of transmission. 相似文献
66.
67.
引言美洲幼虫腐臭病(AFB)是一种蜜蜂幼虫病,可造成蜂蜜生产、蜂数和蜂群的重大损失。此病系幼虫芽孢杆菌(Bacilluas larvae)引起,可由受该菌孢子污染的蜂具在箱、群之间传播。用γ射线照射受污染的蜂具,可杀死上面的孢子,对养蜂业极为有益。为此,本文特谈谈这种技术。 相似文献
68.
69.
哺乳动物的性别决定在哺乳类,Y 染色体决定雄性性别,处显性状态。在基因型上,Y 缺如的(XO,XX,XXX)发育为雌性,不管有多少 X 染色体,只要有 Y(XY,XXY,XXXY,XXXXY)染色体存在就发育为雄性。明显的例外是罕见的(1/20 000)XX 男性和更罕见的(1/100 000) 相似文献
70.
Hassan M.Naif 《国外兽医学(畜禽传染病)》1991,11(4):31-33,7
牛白血病病毒(BLV)是地方流行型牛白血病的病原体,通常用AGID,ELISA试验检测病毒抗体,现用聚合酶链式反应(PCR)检测BLV,可从感染宿主检测到100ng前病毒DNA,使本试验的敏感性提高了两个对数组数,而且无论是在淋巴细胞还是在肿瘤细胞,以及各个感染时期都可检出前病毒DNA。 相似文献