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   929篇
  免费   50篇
  国内免费   1篇
林业   96篇
农学   10篇
基础科学   2篇
  83篇
综合类   122篇
农作物   12篇
水产渔业   66篇
畜牧兽医   554篇
园艺   17篇
植物保护   18篇
  2021年   14篇
  2020年   13篇
  2019年   18篇
  2018年   19篇
  2017年   13篇
  2016年   12篇
  2015年   21篇
  2014年   20篇
  2013年   43篇
  2012年   43篇
  2011年   55篇
  2010年   22篇
  2009年   21篇
  2008年   39篇
  2007年   29篇
  2006年   40篇
  2005年   37篇
  2004年   33篇
  2003年   40篇
  2002年   33篇
  2001年   27篇
  2000年   21篇
  1999年   20篇
  1998年   19篇
  1997年   15篇
  1996年   11篇
  1995年   11篇
  1994年   8篇
  1993年   9篇
  1992年   13篇
  1991年   19篇
  1990年   13篇
  1989年   10篇
  1988年   19篇
  1987年   14篇
  1986年   9篇
  1985年   14篇
  1984年   9篇
  1983年   7篇
  1982年   9篇
  1981年   6篇
  1979年   7篇
  1973年   8篇
  1972年   9篇
  1970年   6篇
  1968年   7篇
  1966年   6篇
  1913年   6篇
  1910年   6篇
  1909年   6篇
排序方式: 共有980条查询结果,搜索用时 62 毫秒
1.
SUMMARY The proposal by the Zoological Parks Board of New South Wales to import 10 southern black rhinoceros (Diceros bicornis) from Zimbabwe as part of an international project for conservation of the species presented the Australian Quarantine and Inspection Service (AQIS) with a unique challenge. This importation is, at least in the modern era, the first importation of live herbivores from the African continent. Many of the serious animal diseases in the world are endemic in parts of Africa. Knowledge of which of these diseases infect wild species and may be transmitted from the wild species to domesticated species, is limited. This paper describes the strategies adopted by AQIS to facilitate the importation of rhinoceros while maintaining protection of Australian consumers, rural industries, domestic livestock and fauna against the entry and spread of unwanted pests and diseases.  相似文献   
2.
3.
4.
5.
6.
    
Ohne ZusammenfassungErst nachdem ich diese Arbeit zum Druck übergeben, kommt ein Aufsatz der neusten Nummer der Allg. Forst- und Jagdzeitung (1909 S. 297 ff.) zu meiner Kenntnis, in welchen Herr Forstrat Müller-Stuttgart dasselbe Thema behandelt. Ich freue mich feststellen zu können, daß der Herr Verfasser, der mehr Einblick in die Einzelheiten besitzt, von denselben Anschauungen in bezug auf Vorratsnutzungen usw. ausgeht, die auch in dieser Arbeit vertreten sind. Jener Artikel, der auf die Scheidung von laufender Rente und Grundkapital näher eingeht, zeigt aber auch, wie schwierig und weittragend der ganze Gegenstand ist und wie bitter not uns eine Einrichtungsanstalt tut, die uns zuverlässige Grundlagen schafft, ehe auf diesem Gebiet endgültig eingegriffen wird.  相似文献   
7.
8.
    
Ohne Zusammenfassung  相似文献   
9.
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   
10.
Improvements in sow productivity have raised questions regarding dietary vitamin D recommendations. The present study aimed to evaluate the effects of the housing system with access to sunlight exposure and supplementation of 25-hydroxicholecalciferol on performance and serum levels of 25(OH)D3 in sows during gestation and lactation. Sows were distributed in an experimental design with two housing systems: gestation crates or gestation free-range system with external area for sunlight exposure; and two diets: 0 or 50 μg of 25-hydroxicholecalciferol kg−1. The use of 25-hydroxicholecalciferol tended (P = 0.052) to improve total born and influenced (P = 0.046) on number of born alive. Litter weight at birth was also increased (P = 0.01) by 25-hydroxicholecalciferol supplementation; 25-hydroxicholecalciferol supplementation and housing system (free-range with sunlight exposure) tended to increase weaning weight (P = 0.07) and litter daily gain (P = 0.051) during lactation. Exposure to sunlight and 25-hydroxicholecalciferol supplementation increased 25(OH)D3 serum levels when compared with control treatment during gestation (136.95 vs. 113.92 ng mL−1; P = 0.035) and lactation (120.29 vs. 88.93 ng mL−1; P = 0.026). In conclusion, the association of 25-hydroxicholecalciferol supplementation with exposure to sunlight during gestation improved significantly 25(OH)D3 serum levels and consequently performance traits in gestation and lactation.  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