全文获取类型
收费全文 | 544篇 |
免费 | 27篇 |
专业分类
林业 | 10篇 |
农学 | 16篇 |
基础科学 | 2篇 |
50篇 | |
综合类 | 104篇 |
农作物 | 15篇 |
水产渔业 | 30篇 |
畜牧兽医 | 323篇 |
园艺 | 10篇 |
植物保护 | 11篇 |
出版年
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 71篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1979年 | 7篇 |
1977年 | 5篇 |
1974年 | 13篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 4篇 |
1970年 | 11篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1966年 | 6篇 |
1881年 | 4篇 |
排序方式: 共有571条查询结果,搜索用时 15 毫秒
1.
2.
Wallace G 《New Zealand veterinary journal》1986,34(11):197; discussion 197-197; discussion 198
3.
4.
5.
6.
The relationship between fine-scale spatial patterns of forage abundance and the feeding patterns of large ungulates is not well known. We compared these patterns for areas grazed in winter by elk and bison in a sagebrush-grassland landscape in northern Yellowstone National Park. At a fine scale, the spatial distribution of mapped feeding stations in 30 m × 30 m sites was found to be random where there were no large patches devoid of vegetation. In areas similar to the mapped sites, the underlying spatial distribution pattern of biomass was also determined to be random. At a broad scale, forage biomass differed among communities across the northern range but forage quality did not. These results suggest that ungulates are feeding randomly within forage patches (fine scale) but may select feeding sites based upon forage abundance at broader, landscape scales. Contrary to what has been suggested in other systems, ungulates were not overmatching at finer scales. 相似文献
7.
Cellular immune responses of peripheral blood lymphocytes to canine distemper virus and measles virus were determined in vaccinated or infected gnotobiotic dogs, using the technique of syncytia inhibition. Cross-reactivity between viruses was detected in both groups of dogs. Peak responses in vaccinated dogs occurred 11 days after vaccination and declined to base-line levels by 3 weeks, whereas responses in infected dogs were present 30 days after inoculation. Fractionation experiments with peripheral blood lymphocytes indicated that synctia inhibition is probably mediated by T lymphocytes. 相似文献
8.
9.
Mandy L. Wallace Janet A. Grimes Daniel J. Duffy Cameron Kindra Melissa MacIver Samantha Lin Valery F. Scharf Chad W. Schmiedt 《The Canadian veterinary journal. La revue veterinaire canadienne》2021,62(6):617
A possible association between the development of nontraumatic, acquired inguinal hernias (NAIH) and perineal hernias (PH) has been postulated in adult dogs. The objective of this study was to evaluate the frequency of concurrent diagnosis of PH in dogs presented with NAIH and determine potential risk factors for concurrent PH and NAIH. Medical records of adult male dogs presented for NAIH to 4 hospitals between 2007 and 2017 were retrospectively reviewed. Twenty-one dogs with NAIH were included, 8 of which had concurrent PH. There were no significant differences between dogs with and without PH; however, among dogs with both conditions, intact dogs (8.1 ± 1.4 years) were younger than neutered dogs (11.7 ± 1.0 years; P = 0.007). Thirty-eight percent of male dogs presenting for NAIH had concurrent PH, indicating that these conditions commonly occur together. Dogs presenting for NAIH should be carefully evaluated for concurrent PH before surgical intervention. 相似文献
10.
A series of asymmetrical thio-bis-N-methylcarbamate derivatives were synthesised by combining 3,4-methylenedioxyphenyl N-methylcarbamate with different N-methylcarbamates. Some of these derivatives combined good insecticidal activity against the housefly with reduced acute oral toxicity to mice. The thio-bis-N-methylcarbamates obtained exhibited a lower anti-cholinesterase activity than the more toxic of the two carbamate moieties contained in each combination. The weak synergism of piperonyl butoxide on the insecticidal activity of the derivatives suggests the possibility of a self synergism phenomenon caused by the 3,4-methylenedioxyphenyl group. 相似文献