全文获取类型
收费全文 | 891篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
林业 | 25篇 |
农学 | 10篇 |
基础科学 | 8篇 |
105篇 | |
综合类 | 220篇 |
农作物 | 49篇 |
水产渔业 | 27篇 |
畜牧兽医 | 418篇 |
园艺 | 21篇 |
植物保护 | 52篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 41篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 46篇 |
2007年 | 23篇 |
2006年 | 35篇 |
2005年 | 37篇 |
2004年 | 38篇 |
2003年 | 35篇 |
2002年 | 51篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 18篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 14篇 |
1972年 | 7篇 |
1971年 | 9篇 |
1970年 | 8篇 |
1969年 | 9篇 |
1968年 | 6篇 |
1967年 | 8篇 |
1915年 | 7篇 |
排序方式: 共有935条查询结果,搜索用时 0 毫秒
1.
A.J.A. Vinten D.R. Lewis D.R. Fenlon K.A. Leach R. Howard I. Svoboda I. Ogden 《Soil Use and Management》2002,18(3):223-231
Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli . Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die-off rate was the same as or quicker than for total E. coli . This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 104 to 5.7 × 105 colony forming units per mL (c.f.u. mL–1 ) was applied to drained field plots. Field die-off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (103 to 104 c.f.u. mL–1 ). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 105 ) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL–1 for much of the sampling period after slurry application (1–3 months). 相似文献
2.
Abstract. Leaching losses of nitrate-nitrogen were measured from a set of eight hydrologically isolated plots on a clay loam soil over the period from September 1987 to February 1990. Variable drainflow recovery from the plots hampered accurate estimation of nitrate loading, but results suggest that, when inorganic nitrogen fertilizer is applied up to the recommended amount, there is little influence of the amount applied on the amount leached. We did, however, observe the following effects on nitrate leaching: leguminous green manure incorporated in autumn increased leaching of nitrate-nitrogen by 10–15 kg per hectare during the winter; autumn cultivation caused some increase in leaching compared with no cultivation in one year; some systematic variations in nitrate leaching occurred between years and between plots, but were unrelated to treatments.
From the results we conclude that green manuring does not provide sufficient nitrogen for organically grown crops on this soil but contributes significantly to nitrate leaching, and that growing spring cereals, with the land remaining in stubble as long as possible in autumn, may be the best strategy to minimize nitrate leaching. 相似文献
From the results we conclude that green manuring does not provide sufficient nitrogen for organically grown crops on this soil but contributes significantly to nitrate leaching, and that growing spring cereals, with the land remaining in stubble as long as possible in autumn, may be the best strategy to minimize nitrate leaching. 相似文献
3.
Howard A. Clonts Curtis M. Jolly Syed Abdulkadir L. Alsagoff 《Journal of the World Aquaculture Society》1989,20(4):268-276
The merits of integrated aquaculture farming (IAF) as a strategy for bolstering income for the rural poor have been recognized, but the economic efficiency and sustainability are yet to be determined. The effects of one species on another and the economic benefits, net of government support, have not been critically evaluated. The concept of a foodniche for alternative species in an aquatic environment has not been properly tested in an economic setting. Thus, this report reflects the results of applying the technique of mixed integer linear programming to determine the optimum combination of species within the context of a foodniche. The objective also included maximizing revenues, with minimal external input requirements, for a representative small Malaysian wet-rice farm. It was found that the foodniche concept permitted flexibility in stocking rates, and that farmers could actually stock species at the exact rate that was optimal for profit, instead of standard fixed rates. Also, government subsidies for pond construction were essential for IAF success. The net revenues from IAF were low without interest-free loans for pond construction. 相似文献
4.
DB ADAMS JJ LYNCH† BH ANDERSON LR FELL‡ GN HINCH§ RK MUNRO¶ 《Australian veterinary journal》1990,67(12):443-445
Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted. 相似文献
5.
6.
7.
8.
9.
10.
L. O. Howard 《Journal of pest science》1926,2(9):114-118
Ohne Zusammenfassung 相似文献