全文获取类型
收费全文 | 146753篇 |
免费 | 8329篇 |
国内免费 | 1422篇 |
专业分类
林业 | 6897篇 |
农学 | 6564篇 |
基础科学 | 1947篇 |
19391篇 | |
综合类 | 22151篇 |
农作物 | 5615篇 |
水产渔业 | 7444篇 |
畜牧兽医 | 74411篇 |
园艺 | 2188篇 |
植物保护 | 9896篇 |
出版年
2021年 | 1465篇 |
2020年 | 1555篇 |
2019年 | 1786篇 |
2018年 | 2517篇 |
2017年 | 2882篇 |
2016年 | 2668篇 |
2015年 | 2511篇 |
2014年 | 2950篇 |
2013年 | 6305篇 |
2012年 | 5088篇 |
2011年 | 5921篇 |
2010年 | 4167篇 |
2009年 | 4212篇 |
2008年 | 5774篇 |
2007年 | 5621篇 |
2006年 | 5247篇 |
2005年 | 4881篇 |
2004年 | 4373篇 |
2003年 | 4412篇 |
2002年 | 4000篇 |
2001年 | 4964篇 |
2000年 | 4909篇 |
1999年 | 4042篇 |
1998年 | 1729篇 |
1997年 | 1710篇 |
1996年 | 1552篇 |
1995年 | 1816篇 |
1994年 | 1526篇 |
1993年 | 1509篇 |
1992年 | 2894篇 |
1991年 | 3004篇 |
1990年 | 2957篇 |
1989年 | 2975篇 |
1988年 | 2676篇 |
1987年 | 2631篇 |
1986年 | 2562篇 |
1985年 | 2409篇 |
1984年 | 1964篇 |
1983年 | 1723篇 |
1982年 | 1162篇 |
1979年 | 1650篇 |
1978年 | 1284篇 |
1977年 | 1135篇 |
1975年 | 1164篇 |
1974年 | 1357篇 |
1973年 | 1448篇 |
1972年 | 1378篇 |
1971年 | 1195篇 |
1970年 | 1247篇 |
1969年 | 1146篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Bernardo TM 《Journal of veterinary medical education》2006,33(4):533-538
Food systems educators face a double challenge: (1) the inherent change in scope and perspective from raising animals to producing safe food in an environmentally conscientious manner; and (2) the unprecedented demand for higher education, both nationally and internationally. In the modern world, small numbers of producers are capable of feeding a growing population. As demographics have shifted from rural to urban areas, more global livelihoods are derived from manufacturing and services than from agriculture. Education, as one of those services, is accounting for an increasing percentage of world trade, through the physical translocation of students and, more recently, through online education. Within the veterinary realm, colleges outside the United States seek accreditation to better compete for students, and there is increasing pressure from private schools. Today's food systems require a high level of veterinary expertise, with specialization in a particular production system as well as the ability to contribute as part of a larger team that can address economic, bio-security, biological-waste, animal-welfare, food-safety, and public-health concerns. The need for different expertise from food systems specialists (indeed, shortages of all types of veterinary specialists), combined with global competition in education, is a call to action for the veterinary profession. This is an opportunity to revisit and reorganize the delivery of veterinary education, making use of new collaborative technologies for greater efficiency and effectiveness. 相似文献
972.
973.
974.
975.
976.
S M Stover W J Hornof G L Richardson D M Meagher 《Journal of the American Veterinary Medical Association》1986,188(6):624-628
History, physical examination, and bone scintigraphy were used to diagnose central and/or third tarsal bone trauma in 3 acutely lame horses. In all 3 cases, the results of initial radiographic examination were negative. Bone scintigraphy revealed focal, intense radioisotope uptake at the level of the distal tarsal bones in the 3 horses. Radiographs obtained 4 weeks after injury in one horse demonstrated a slab fracture of the central tarsal bone. Conservative management of the tarsal bone disease resulted in acceptable return to function in all 3 horses. 相似文献
977.
Hamid ME Alla KM Ahmed SS El Shiekh AE Ibrahim KE 《Journal of the South African Veterinary Association》2006,77(2):90-91
We describe a rare case of a concurrent demodectic and sarcoptic mange in a 2-year-old heifer in Khartoum, Sudan. The lesions were massive lumps of granulomatous tumour-like dermatitis with thick, nodular folds mainly covering the head, neck and shoulders. Histopathological examination of the lesions revealed the presence of both Demodex bovis and Sarcoptes scabiei. The animal died regardless of the anti-parasitic treatment it received. 相似文献
978.
Olivier PA Dippenaar SM Khalil LF Mokgalong NM 《The Onderstepoort journal of veterinary research》2000,67(2):135-140
The phylogeny of the genus Udonella has been disputed for quite some time, but recent phylogenetic analysis of molecular data confirms that the genus is a monopisthocotylean monogenean. Specimens of Udonella myliobati parasitizing the copepod Lepeophtheirus natalensis, an ectoparasite of the spotted ragged-tooth shark, (Carcharias taurus), were collected and studied. A total of 771 monogenean specimens were recovered from 54 infected copepods examined, with a mean intensity of 14,3 worms per copepod. Most of the monogeneans were found attached to the dorsal surface of the lateral and frontal marginal membranes of the copepod carapace. Eggs, with filaments and adhesive discs, were found ventrally on the host, mainly attached to the maxillae and maxillipeds, in clusters of 12-14. Observations on the morphology, distribution and behaviour of this monogenean are presented with the aid of light and scanning electron microscopy. 相似文献
979.
Guangjun Guo Jianchang Gao Xiaoxuan Wang Yanmei Guo J.C. Snyder Yongchen Du 《Breeding Science》2013,63(3):239-245
An accurate and simple evaluation method is crucial for identifying whitefly resistance in tomato breeding. We developed an in vitro method for evaluating resistance of tomato leaves and tested this on wild and cultivated tomato varieties. We found that young leaves observed for whitefly oviposition after 8 hours provided appropriate comparative conditions. This method effectively distinguished resistance among tomato cultivars and wild species and also demonstrated significant difference in oviposition rates among leaf positions on susceptible cultivars. The in vitro test was as precise as in vivo test using intact plants and had advantages over in vivo test, and can be used for evaluating resistance in large populations. 相似文献
980.
GA1-2菌株的分离鉴定及其对香蕉尖孢镰刀菌的抑菌效果 总被引:2,自引:0,他引:2
为了从土壤中分离筛选对香蕉尖孢镰刀菌具有良好拮抗作用的放线菌,采用平板稀释涂布法从四川省会理县干热河谷小麦根际土壤中进行放线菌分离,并采用平板对峙法和孢子萌发法进行筛选,通过形态特征、培养特征、生理生化特征以及16S r DNA序列分析对筛选菌株进行鉴定。结果表明,从四川省会理县干热河谷小麦根际土壤筛选获得一株对香蕉尖孢镰刀菌4号生理小种Fusarium oxysporum f.sp.cubense race 4(FOC4)菌丝和孢子萌发都有很强抑制作用的菌株GA1-2,对FOC4菌丝和孢子萌发抑制率分别为36.34%和94.81%。菌株GA1-2与薰衣草灰链轮丝菌Streptoverticillium lavenduligriseum的亲缘关系最近,相似率达99.85%,且其形态特征、培养特征、生理生化特征也与薰衣草灰链轮丝菌基本相符,因此将菌株GA1-2初步鉴定为薰衣草灰链轮丝菌。 相似文献