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81.
82.
A key assumption in many homegarden studies is that homegardens are ecologically and socio-economically sustainable due to their species diversity. The precise relation between diversity and sustainability is still heavily debated, however. A basic question is how diversity in homegardens can best be characterized in view of the various dimensions of species diversity and their variation in time and space. This paper assesses different types of species diversity in the homegardens of Sidama region of southern Ethiopia. In a survey of crop species in 144 homegardens a total of 78 cultivated crop species (excluding trees) belonging to 10 functional groups were recorded; there were on average 16 crop species and 8 functional groups per farm. Within homegardens, plots differ in species composition and crop diversity. Four types of homegarden systems are distinguished differing in both type and area-share of dominant species, relative orientation at subsistence or cash production and overall crop diversity. The gradual replacement of enset by maize and of coffee by more financially attractive cash crops khat and pineapple causes a decrease in overall crop diversity. Our data demonstrate that it is incorrect to consider homegardens as generic systems with a uniform distribution of species diversity: important within and between homegarden variation exists. Ecological and socio-economic sustainability is not just related to species diversity per se, but rather to more specific features such as presence of keystone species and diversity in functional species groups. Socio-economic sustainability in terms of adjustment to socio-economic change implies dynamics in species diversity.  相似文献   
83.
A survey aimed at determining the status of ticks in cattle, sheep and goats in Bedelle district (Southwestern Ethiopia) was carried out from November 2007 to April 2008. Out of the total 330 animals examined, 314 (95.2%) were found to be infested (harbouring of at least a single tick). High rates of infestations were recorded across all three host species. Factors like month of collection, age and sex of host species did not show significant association with infestation rates. A total of 5,507 ticks belonging to three genera (i.e. Amblyomma, Boophilus and Rhipicephalus) were collected during the study period of which six species were identified. The species of ticks encountered comprise of Amblyomma cohaerens (44.1%), Amblyomma variegatum (13.8%), Amblyomma lepidum (1.2%), Boophilus decoloratus (24.9%), Rhipicephalus evertsi evertsi (14.3%) and Rhipicephalus lunulatus (1.7%). As about 86.7% (4,772) of the ticks were collected from cattle, it was recognised that this could be an evidence of host preference where cattle are serving as principal host while sheep and goats serve as alternative hosts. The role of ecological factors and little attention paid by livestock owners for treatment of animals against ticks are suggested to result in the abundance of ticks. Acaricide spraying should be strategically applied to control ticks. Better result could be achieved if an emphasis is being put on spraying cattle. Studies on tick-borne diseases, involvement of wildlife species as well as related factors are recommended as they may provide a valuable basis for designing and launching an all-round control programme in the country.  相似文献   
84.
Effects of arginine and protein on chicks' responses to dietary lysine   总被引:1,自引:0,他引:1  
1. A chick experiment was designed to test whether the proven effect of excess protein on the requirement for lysine was associated with the arginine content of the protein. 2. Protein contents of 180, 220, 260 and 300 g/kg diet were fed in combination with lysine concentrations of 38, 43, 48, 53 and 58 g/kg crude protein and arginine concentrations of 49.4 or 68.4 g/kg crude protein. 3. Growth rate and efficiency of food utilisation were not significantly affected by the arginine content of the protein. Significant responses to lysine were obtained at all protein contents. 4. Lysine required for maximum growth or maximum food efficiency increased in direct proportion to the protein content of the diet and was not affected by arginine content of the diet within the range of concentrations tested.  相似文献   
85.
86.
1. Chicks were fed from 4 to 18 d on 40 diets containing all combinations of 8 crude protein (CP) concentrations (from 160 to 300 g/kg) and 5 tryptophan concentrations (from 7.5 to 13.5 g tryptophan/kg CP). 2. At each protein concentration there were responses in growth rate and in efficiency of food utilisation to supplementation with tryptophan. Curves were fitted to estimate the maximum response at each protein concentration. 3. The amounts of tryptophan required (g/kg) for maximum growth and maximum food efficiency were each linear functions of dietary protein concentration. The chick's requirement for tryptophan can be expressed as 12 g/kg CP. 4. It is concluded that a fixed ratio of tryptophan to protein should be specified in practical diet formulation, rather than a minimum dietary concentration of tryptophan.  相似文献   
87.
A study was conducted to determine the prevalence of mastitis, identify the major bacterial pathogens and test the antimicrobial resistance of milk bacterial isolates in smallholder dairy farms in Selalle area, Ethiopia. A total of 109 smallholder dairy farms comprising 500 crossbred lactating cows were included. The prevalence of clinical mastitis at herd, cow and quarter level was 8.3% (n = 9), 1.8% (n = 9) and 0.51% (n = 10), respectively, while that of sub-clinical mastitis was 54.7%, 22.3% and 10.1%, respectively. The univariate logistic regression showed that among the risk factors considered, presence of teat lesion, stage of lactation and parity number had significant effect on the prevalence of sub-clinical mastitis. However, after multivariate analysis, only presence of teat lesion and stage of lactation had significant effect. The common isolates from the clinical mastitic quarters were St. agalactiae (30%, n = 3) and St. dysgalactiae (30%, n = 3), while from sub-clinical cases were S. aureus (42.6%, n = 83), S. epidermidis (22.1%, n = 43), St. agalactiae (12.8%, n = 25) and St. uberis (10.3%, n = 20). Staphylococcus intermedius and Streptococcus dysgalactiae were the species, which showed high level of susceptibility for most of the antimicrobials tested, while the remaining had varying levels of resistance for almost all the antimicrobials used. Among the antimicrobials employed, erythromycin and sulphonamide showed the lowest proportion of resistant isolates. Considering the possible significant economic losses that could be incurred by both clinical and sub-clinical mastitis, attention should be paid for further detailed investigations including the economic losses and benefits of interventions in the study area.  相似文献   
88.
Broodstock evaluations are often measured by variables such as spawning success, fecundity, fertilization and hatching rates, usually expressed as percentage values. Outcomes are generally analysed as continuous random variables, assuming that they follow a normal distribution. Ordinary linear regression models (e.g. analysis of variance) as well as χ2 analysis are typically applied. However, these models may not be the most appropriate as a number of test criteria may not be met. For example, spawning success outcomes are inherently discrete and non‐negative data and hence their distribution is not likely to be normal. As these models may not be the most appropriate, a case study using logit analysis as an alternative method for the evaluation of this type of data is presented by considering the response as binary data (spawned versus did not spawn). An exact version of logit analysis was performed due to the sparseness of the data. The results demonstrate that appropriate statistical models provide better insight into the cause–effect relationships that exist between control variables and the dependent variable (likelihood of spawning in this case). As would be expected, each strain of fish responded somewhat differently to the test variables. Changing the protein level of the diet from 32% to 42% or increasing the feeding frequency from three to six times per week either did not influence spawning or negatively affected spawning respectively. Additionally, older fish performed better than younger fish and the early spawning period was better than the later spawning period, regardless of strain. These responses, however, were only detected using logit analysis, which is a more sensitive test and would thus be recommended for this type of data.  相似文献   
89.
Stagnant early growth and mortality are the major impediments for sheep production in southern Ethiopia. We evaluated the effects of non-genetic factors on early growth performance of lambs in Halaba district with 467 lambs owned by 60 households. Body weights (kilograms) of lambs at birth, 30, 60, 90, 120, and 150 days were 2.30 ± 0.03, 4.45 ± 0.11, 6.94 ± 0.13, 10.4 ± 0.19, 13.3 ± 0.19, and 15.7 ± 0.20, respectively. The average daily gain (ADG; gram) from birth to 30, 60, 90, 120, and 150 days were 71.18 ± 8.18, 77.18 ± 2.19, 89.20 ± 1.98, 91.18 ± 1.51, and 90.68 ± 1.27, respectively. Season effect was significant (p < 0.05) for weight at birth, 30, and 120 days. Similarly, season of birth influenced (p < 0.05) ADG (gram) at all ages except from birth to 60 days. Single-born lambs were heavier over multiple births (p < 0.01), 90 (p < 0.001) and 120 days (p < 0.05) and higher (p < 0.001) ADG from birth to 90 days. There were significant interaction effects of parity by sex at birth (p < 0.01) and parity by type of birth (p < 0.001) and 90 days (p < 0.01). From the non-genetic factors estimated in this study, season and type of birth, and their interaction had a more profound effect at early growth of lambs, and they need to be considered in the improvement plan of sheep under Halaba arid to semi-arid environments. Efforts geared towards planned breeding, improved nutrition, and health would assist farmers to exploit these indigenous and adaptable sheep resources efficiently.  相似文献   
90.
Twenty elite early-maturing (75-90 days) tropical maize varieties grown in three diverse agroecologies in West Africa were evaluated to identify varieties with high kernel-Fe and -Zn and bioavailable Fe levels. Bioavailable iron was assessed using an in vitro digestion/Caco-2 cell model. Significant (P < 0.001) varietal differences were observed in mean kernel-Fe and -Zn levels. The ranges were 15.5-19.1 mg kg(-)(1) for Fe and 16.5-20.5 mg kg(-)(1) for Zn. Genetic component accounted for 34% of the total variation in kernel-Zn and for 11% of the variation in kernel-Fe levels. Mean bioavailable Fe in varieties ranged between 4% below and 49% above the reference control variety. A significant negative relationship was detected between kernel-P concentration and bioavailable Fe (R = -0.36; P < 0.004; n = 60). Two varieties, ACR90POOL16-DT and ACR86TZESR-W, were identified as the most promising for further evaluation to determine their efficacy as improved sources of iron in target populations.  相似文献   
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