全文获取类型
收费全文 | 79047篇 |
免费 | 4295篇 |
国内免费 | 93篇 |
专业分类
林业 | 3199篇 |
农学 | 2046篇 |
基础科学 | 462篇 |
8582篇 | |
综合类 | 15416篇 |
农作物 | 3133篇 |
水产渔业 | 3436篇 |
畜牧兽医 | 41860篇 |
园艺 | 853篇 |
植物保护 | 4448篇 |
出版年
2019年 | 726篇 |
2018年 | 1099篇 |
2017年 | 1221篇 |
2016年 | 1057篇 |
2015年 | 908篇 |
2014年 | 1204篇 |
2013年 | 2625篇 |
2012年 | 2142篇 |
2011年 | 2598篇 |
2010年 | 1629篇 |
2009年 | 1740篇 |
2008年 | 2608篇 |
2007年 | 2426篇 |
2006年 | 2299篇 |
2005年 | 2142篇 |
2004年 | 2080篇 |
2003年 | 2145篇 |
2002年 | 1928篇 |
2001年 | 2386篇 |
2000年 | 2439篇 |
1999年 | 1868篇 |
1998年 | 719篇 |
1997年 | 711篇 |
1996年 | 713篇 |
1995年 | 806篇 |
1993年 | 741篇 |
1992年 | 1554篇 |
1991年 | 1754篇 |
1990年 | 1637篇 |
1989年 | 1647篇 |
1988年 | 1473篇 |
1987年 | 1537篇 |
1986年 | 1597篇 |
1985年 | 1547篇 |
1984年 | 1185篇 |
1983年 | 1058篇 |
1982年 | 704篇 |
1979年 | 1152篇 |
1978年 | 895篇 |
1977年 | 756篇 |
1975年 | 774篇 |
1974年 | 1025篇 |
1973年 | 1025篇 |
1972年 | 1045篇 |
1971年 | 994篇 |
1970年 | 988篇 |
1969年 | 903篇 |
1968年 | 811篇 |
1967年 | 799篇 |
1966年 | 732篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
Wilson EO 《Science (New York, N.Y.)》1985,228(4707):1489-1495
Studies on the social insects (ants, bees, wasps, and termites) have focused increasingly on sociogenesis, the process by which colony members undergo changes in caste, behavior, and physical location incident to colonial development. Caste is determined in individuals largely by environmental cues that trigger a sequence of progressive physiological restrictions. Individual determination, which is socially mediated, yields an age-size frequency distribution of the worker population that enhances survival and reproduction of the colony as a whole, typically at the expense of individuals. This "adaptive demography" varies in a predictable manner according to the species and size of the colony. The demography is richly augmented by behavioral pacemaking on the part of certain castes and programmed changes in the physical position of colony members according to age and size. Much of what has been observed in these three colony-level traits (adaptive demography, pacemaking, and positional effects) can be interpreted as the product of ritualization of dominance and other forms of selfish behavior that is still found in the more primitive insect societies. Some of the processes can also be usefully compared with morphogenesis at the levels of cells and tissues. 相似文献
162.
163.
164.
165.
Marshall E 《Science (New York, N.Y.)》1985,229(4718):1070
166.
167.
168.
169.
Pemphigus foliaceus of the footpads in three dogs 总被引:1,自引:0,他引:1
P J Ihrke A A Stannard A A Ardans C E Griffin A J Kallet 《Journal of the American Veterinary Medical Association》1985,186(1):67-69
Severe hyperkeratinization and villous hypertrophy of the footpads were seen in 3 middle-aged dogs. Peeling, fissuring, swelling, and ulcerations were noted on the margins of severely affected pads. Pain was evident in palpation and ambulation. Lesions were compatible with the traditional diagnosis of "hard pad disease". Histopathologic findings were diagnostic for canine pemphigus foliaceus in all 3 dogs, and direct immunofluorescence in an intercellular pattern was seen in both dogs that were tested. All 3 dogs responded to immunosuppressive dosages of corticosteroids. 相似文献
170.
The modern role of meat inspection and food hygiene 总被引:2,自引:2,他引:0
Feltmate TE 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(1):29-32,33