全文获取类型
收费全文 | 310篇 |
免费 | 16篇 |
专业分类
林业 | 19篇 |
农学 | 3篇 |
26篇 | |
综合类 | 67篇 |
农作物 | 9篇 |
水产渔业 | 34篇 |
畜牧兽医 | 161篇 |
植物保护 | 7篇 |
出版年
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 17篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 14篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1975年 | 6篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1958年 | 1篇 |
1907年 | 4篇 |
1903年 | 1篇 |
1902年 | 1篇 |
排序方式: 共有326条查询结果,搜索用时 15 毫秒
91.
W. F. Megahan S. B. Monsen M. D. Wilson N. Lozano D. F. Haber G. D. Booth 《Land Degradation \u0026amp; Development》1992,3(1):55-65
Cost effectiveness of six alternative road embankment construction practices and 16 alternative fill-slope stabilization practices was evaluated as means for controlling erosion on forest roads built on granitic soils in Idaho (USA). A total of 63 bordered erosion plots 1-8 m wide by 4-6 m long, were used. Eroded material was collected in troughs at the bottom of each plot in the spring and fall. Measurements began in the fall of 1981 and continued until the fall of 1983. Costs were obtained by tabulating actual labor, equipment, and supplies used to install the treatments. Rainfall erosivity values accumulated for the snow-free periods between erosion measurements proved to be a statistically significant covariate for the analysis of treatment effects. There were no significant differences between the three embankment construction practices (sidecast, layer placed, and controlled compaction). But surface rolling did significantly increase erosion in all cases. Nine of the post-construction soil stabilization measures significantly reduced erosion, and one measure significantly increased erosion (P < 0-5). Stabilization measures that combined mulches with revegetation appeared to be more beneficial for erosion control than either mulches or revegetation alone. Rankings of the erosion control effectiveness of individual soil stabilization practices were different from the rankings of the cost effectiveness of the practices. Application of alternative treatments is discussed. 相似文献
93.
A.L. KilBride M. Mendl P. Statham S. Held M. Harris J.N. Marchant-Forde H. Booth L.E. Green 《Preventive veterinary medicine》2014
A prospective longitudinal study was carried out on 39 outdoor breeding pig farms in England in 2003 and 2004 to investigate the risks associated with mortality in liveborn preweaning piglets. Researchers visited each farm and completed a questionnaire with the farmer and made observations of the paddocks, huts and pigs. The farmer recorded the number of piglets born alive and stillborn, fostered on and off and the number of piglets that died before weaning for 20 litters born after the visit. Data were analysed from a cohort of 9424 liveborn piglets from 855 litters. Overall 1274 liveborn piglets (13.5%) died before weaning. A mixed effect binomial model was used to investigate the associations between preweaning mortality and farm and litter level factors, controlling for litter size and number of piglets stillborn and fostered. Increased risk of mortality was associated with fostering piglets over 24 h of age, organic certification or membership of an assurance scheme with higher welfare standards, farmer's perception that there was a problem with pest birds, use of medication to treat coccidiosis and presence of lame sows on the farm. Reduced mortality was associated with insulated farrowing huts and door flaps, women working on the farm and the farmer reporting a problem with foxes. 相似文献
94.
A 6-year-old mare was presented for acute abdominal pain unresponsive to analgesics. Exploratory laparotomy revealed entrapment of the small colon through a 12 cm rent in the mesocolon. The incarcerated small colon was manually reduced and the rent in the mesocolon was sutured closed. The mare made excellent postoperative recovery and was discharged from the hospital 4 days later. The cause of the rent, which was chronic in appearance, is unknown. 相似文献
95.
E. Bombardier R. K. Booth H. J. Green R. S. McKinley 《Fish physiology and biochemistry》2010,36(3):355-365
The adaptability/plasticity of the highly oxidative red muscle in Atlantic salmon was demonstrated during spawning migration.
Substrate concentrations and the enzymatic pathways of ATP production were examined in red muscle obtained from Atlantic salmon
at different sites along their migratory route in the Exploits River, Newfoundland, Canada. Individuals were chronologically
sampled from a seawater site, two sites upstream, and at spawning. The 20% decrease in salmon body weight during the later
stages of migration was accompanied by large decreases (mg dry weight−1) in both glycogen (P < 0.01) and total muscle lipid (P < 0.01). In contrast, water content and protein concentration (mg dry weight−1) of the red muscle increased by 25 and 34%, respectively, at spawning. Enzymes of the glycolytic pathways demonstrated a
significant (P < 0.001) decrease in maximal activity as migration proceeded whereas enzymes of the oxidative phosphorylation pathways, specifically
the citric acid cycle enzymes, exhibited an increase (P < 0.001) in maximal activity at spawning. The antioxidant enzyme superoxide dismutase also demonstrated an increase (P < 0.001) in maximal activity during the latter stages of migration. These adaptations imply that the red epaxial muscle of
Atlantic salmon has a more efficient means of oxidizing lipids, while minimizing free radical damage, during the later stages
of migration and spawning, thereby potentially increasing post spawning survival. 相似文献
96.
In studies to determine whether there were antigenic differences between strains (isolates) of Moraxella bovis, the sera from vaccinated calves were tested with isolates of M bovis while the calves were experiencing epizootics of infectious bovine keratoconjunctivitis (IBK). Before the epizootics of IBK, the calves were intramuscularly vaccinated with a formalin-killed autogenous M bovis bacterin. During the epizootics, the eyes were examined by cultural technique, and isolates which were obtained were categorized by catalase activity, source (diseased or nondiseased eyes), and reactivity with the various sera. The serum reactivity of the isolates was compared with that of the vaccinal strain. The vaccinal strain and 8 of the 1 5 selected isolates obtained during the 1974 epizootic were catalase negative. Seven of the 15 isolates from the 1974 epizootic and all of the selected isolates from the 1975 epizootic were catalase positive. A significantly higher (P less than 0.01) percentage of calf sera were serologically reactive with the vaccinal strain and other catalase-negative isolates (45.0%) than with catalase-positive isolates (34.8%). The results, although not definitive, suggest that there may be antigenic differences among strains of M bovis. These differences should be considered when cattle are vaccinated against IBK under natural conditions of exposure. 相似文献
97.
98.
Booth MJ van der Lugt JJ van Heerden A Picard JA 《Journal of the South African Veterinary Association》2001,72(2):99-104
Disseminated mycosis caused by Paecilomyces varioti in a female German shepherd dog presented with chronic forelimb lameness is described. Radiographs of the swollen carpal joint revealed geographic lysis of the radial epiphysis. Diagnosis was based on cytological demonstration of fungal hyphae and chlamydiospores, as well as fungal culture of fluid obtained by arthrocentesis. Temporary remission was characterised by markedly improved clinical signs and laboratory parameters, following treatment with ketoconazole. The dog was euthanased 9 months after the initial diagnosis, following the diagnosis of multifocal discospondylitis. This appears to be the longest described period of temporary remission obtained with treatment in dogs with paecilomycosis. Clinical, clinicopathological and necropsy findings of this disease in another German shepherd dog are briefly described. 相似文献
99.
100.
D. C. E. Wurr Jane R. Fellows M. C. Hogge D. M. Booth E. J. Allen 《Potato Research》1992,35(2):149-155
Summary The number of stems per seed tuber produced by 17 seed stocks of cv. Record was determined in glasshouse and field experiments
to assess the feasibility of predicting the number of stems produced in the field. Multiple regression analysis showed that
seed tuber weight alone gave the most satisfactory fit to stems produced in the field, which was not improved by adding terms
involving the number of stems produced in the glasshouse.
Quadratic relationships between the number of above-ground stems per tuber and tuber weight were most appropriate for each
stock, with the fitted curves for individual stocks differing only in the constant term. However, there were significant rank
correlation coefficients between the constant terms for relationships between field stems and tuber weight and glasshouse
stems and tuber weight, suggesting that in other cultivars and seed stocks a predictive glasshouse test might still be useful. 相似文献