全文获取类型
收费全文 | 448篇 |
免费 | 19篇 |
专业分类
林业 | 42篇 |
农学 | 7篇 |
基础科学 | 1篇 |
54篇 | |
综合类 | 85篇 |
农作物 | 18篇 |
水产渔业 | 35篇 |
畜牧兽医 | 188篇 |
园艺 | 7篇 |
植物保护 | 30篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 9篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 18篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1994年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1974年 | 3篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 6篇 |
1963年 | 3篇 |
1927年 | 3篇 |
排序方式: 共有467条查询结果,搜索用时 613 毫秒
51.
52.
New challenges in pest science 总被引:1,自引:1,他引:0
Jürgen Gross 《Journal of pest science》2006,79(1):1-2
53.
Movement rules for herbivores in spatially heterogeneous environments: responses to small scale pattern 总被引:4,自引:0,他引:4
John E. Gross Colleen Zank N. Thompson Hobbs Donald E. Spalinger 《Landscape Ecology》1995,10(4):209-217
Foraging herbivores respond to the spatial pattern of resources at a variety of scales. At small scales of space and time, existing models capture the essence of the feeding process and successfully predict intake rates. Models that operate over larger scales have not exhibited a similar success, in part because we have a limited understanding of the rules used by animals to make decisions in spatially complex environments, or of the consequences of departing from these rules. To evaluate the rules that large herbivores use when navigating between forages, we examined movements of bighorn sheep foraging on apparent prey (alfalfa plants) in hand-constructed patches of plants. Observations of movements and path lengths were compared to simulations that used a variety of different rules-of-thumb to determine a search path. Rules used in simulations ranged from a random walk with various detection distances, to more complicated rules that solved a variant of the travelling salesman problem. Simulations of a random walk yielded movement lengths that exceeded observations by a factor of 3 for long detection distances, and by 30-fold for short detection distances. Observed move distances were most closely approximated by simulations based on a nearest-neighbor ruleover 75 % of all moves by bighorn sheep were to the closest available plant. Movement rules based on random walks are clearly inappropriate for many herbivores that typically consume visually apparent plants, and we suggest the use of a nearest-neighbor rule for modelling foraging by large herbivores. 相似文献
54.
The number of lymphocytes in chicken blood samples decreased and the number of heterophils increased in response to stressors and to increasing levels of corticosterone in the chicken feed. The ratio of heterophils to lymphocytes was less variable than the number of heterophil or lymphocyte cells, and the range of values for this ratio was greater than the range of values for heterophils and lymphocytes among control and experimental groups. The heterophil/lymphocyte ratio appears to be a more reliable indicator of levels of corticosterone in the feed and to social stress than were the plasma corticosteroid levels. 相似文献
55.
A K Athnasios E J Healy A F Gross G J Templeman 《Journal of the Association of Official Analytical Chemists》1986,69(1):65-67
A capillary gas chromatographic (CGC) method is described for the determination of cis,cis-methylene interrupted polyunsaturated fatty acids (cis-PUFA) in fats and oils. The sample is saponified and the liberated fatty acids are esterified to the corresponding methyl esters. The latter are analyzed by CGC using a 60 M. SP2340 capillary column. Area percent values for 9,12-cis,cis-C18:2 and 9,12,15-cis,cis,cis-C18:3 fatty acid methyl esters are summed to give the total cis-PUFA content. Gas chromatographic results agreed well with those obtained by an enzymatic lipoxygenase method at the 31-48% cis-PUFA levels with a correlation coefficient of 0.98. The method has a precision (relative standard deviation) of 0.33% at a 44.4% cis-PUFA level in margarine oil. 相似文献
56.
W B Gross 《Avian diseases》1979,23(4):1031-1036
57.
T L Gross K W Kwochka G A Kunkle 《Journal of the American Veterinary Medical Association》1986,189(10):1322-1325
Eighteen cats with miliary dermatitis were evaluated, using skin testing and histology. Sixteen cats had allergic skin disease (14 cats had positive skin-test reactions to flea antigen [two of which were also atopic], one was atopic only, and one was allergic to beef). In the two remaining cats, the cause of miliary dermatitis was not identified. Histologically, 17 of the cats had superficial eosinophilic dermatitis and epidermal spongiosis, crusting, and ulceration, which were compatible with an allergic cause. Four of these cats had concurrent eosinophilic plaques, which histologically resembled miliary lesions. This overlap of plaques with miliary lesions indicated that when plaques and miliary dermatitis are found concurrently, both lesions may be caused by the same allergens. 相似文献
58.
Chickens were infected with an avian adenovirus group II isolate previously obtained from chickens exhibiting splenomegaly in commercial broiler flocks. The isolate was inoculated orally in 6-week-old experimental chickens, which were euthanatized and necropsied 6 days postinoculation. The primary gross lesions found were splenomegaly and splenic mottling. Numerous tissues from 12 chickens were taken for histologic evaluation. Histologic lesions included splenic reticuloendothelial cell hyperplasia with intranuclear inclusions. Lymphocytic degeneration was seen in the lungs of most chickens examined. Lung hemorrhage and edema with endothelial disruption and congestion of pulmonary arterioles were found less frequently. The splenic lesions in the chickens were similar to those seen in turkeys naturally infected with hemorrhagic enteritis, and the lung lesions resembled those seen in pheasants naturally infected with marble spleen disease. 相似文献
59.
60.