全文获取类型
收费全文 | 104016篇 |
免费 | 3797篇 |
国内免费 | 43篇 |
专业分类
林业 | 4274篇 |
农学 | 3286篇 |
基础科学 | 637篇 |
13319篇 | |
综合类 | 16611篇 |
农作物 | 4260篇 |
水产渔业 | 5670篇 |
畜牧兽医 | 51480篇 |
园艺 | 1342篇 |
植物保护 | 6977篇 |
出版年
2021年 | 852篇 |
2020年 | 986篇 |
2019年 | 1069篇 |
2018年 | 1766篇 |
2017年 | 1983篇 |
2016年 | 1911篇 |
2015年 | 1621篇 |
2014年 | 1920篇 |
2013年 | 4280篇 |
2012年 | 3502篇 |
2011年 | 3924篇 |
2010年 | 2514篇 |
2009年 | 2395篇 |
2008年 | 3661篇 |
2007年 | 3524篇 |
2006年 | 3251篇 |
2005年 | 3078篇 |
2004年 | 2875篇 |
2003年 | 2889篇 |
2002年 | 2665篇 |
2001年 | 3188篇 |
2000年 | 3073篇 |
1999年 | 2488篇 |
1998年 | 1041篇 |
1997年 | 947篇 |
1996年 | 844篇 |
1995年 | 991篇 |
1994年 | 894篇 |
1993年 | 891篇 |
1992年 | 1957篇 |
1991年 | 1931篇 |
1990年 | 1876篇 |
1989年 | 1953篇 |
1988年 | 1700篇 |
1987年 | 1809篇 |
1986年 | 1860篇 |
1985年 | 1780篇 |
1984年 | 1407篇 |
1983年 | 1257篇 |
1982年 | 889篇 |
1979年 | 1223篇 |
1978年 | 1005篇 |
1977年 | 878篇 |
1975年 | 859篇 |
1974年 | 1110篇 |
1973年 | 1138篇 |
1972年 | 1100篇 |
1971年 | 1046篇 |
1970年 | 912篇 |
1969年 | 852篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
G K Ogilvie C S Brunkow G B Daniel W M Haschek 《Journal of the American Veterinary Medical Association》1989,194(6):793-796
Malignant lymphoma involving bone and heart was diagnosed in a 4-year-old Whippet, using radiography, histologic examination, nuclear scintigraphy of the skeleton and heart, and cardiac ultrasonography. 相似文献
102.
Chiang HC 《Science (New York, N.Y.)》1976,192(4240):675-677
103.
E. C. Roumen 《Euphytica》1992,64(3):173-182
Summary Neck nodes of eight rice genotypes were inoculated with a virulent isolate of the blast pathogen at four slightly different, increasingly older stages of panicle development shortly after flowering. Resistance to infection as well as resistance to growth of the pathogen after infection was assessed. Significant differences between genotypes were found for both components of resistance. Resistance to growth of the pathogen sharply increased with aging of the neck node as was indicated by a large reduction of the length of the lesions on the culm, but resistance to infection did not change much. The lesion length was closely related to yield loss. A small delay in time of infection can lead to a large decrease in yield reduction. Meaningful comparison of partial resistance to neck blast between genotypes therefore requires infection at an identical stage of panicle development. In the field, where panicles are in different stages of development, selection of genotypes that do show the symptoms of neck blast together with relatively little yield loss in infected panicles is recommended. 相似文献
104.
In a survey of fungi causing seedling diseases of sugar beet using a soil bioassay, Aphanomyces cochlioides and Pythium spp. were found to occur in 39% and 31%, respectively, of 341 sugar-beet fields selected in a stratified random sample in England, The frequency of A. cochlioides-infested soils varied widely in the different sugar-beet growing areas of the country. Soil pH was the single factor most strongly associated with the distribution of the pathogen, but regression models applied to combinations of factors indicated that soil texture and the interval between sugar-beet crops were also relevant to its frequency. It was detected less often in soils of high pH (≥ 75). heavy texture and where the interval between sugar-beet crops exceeded 5 years. No significant associations were found between the proportion of soils with Pythium spp. and soil or cropping factors. 相似文献
105.
106.
107.
108.
109.
110.