全文获取类型
收费全文 | 247篇 |
免费 | 5篇 |
专业分类
林业 | 28篇 |
农学 | 10篇 |
基础科学 | 11篇 |
104篇 | |
综合类 | 9篇 |
农作物 | 7篇 |
水产渔业 | 1篇 |
畜牧兽医 | 68篇 |
园艺 | 2篇 |
植物保护 | 12篇 |
出版年
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 5篇 |
2011年 | 15篇 |
2010年 | 3篇 |
2009年 | 21篇 |
2008年 | 30篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 6篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有252条查询结果,搜索用时 0 毫秒
51.
A. Nurfeta A. Tolera L. O. Eik F. Sundstøl 《Journal of animal physiology and animal nutrition》2009,93(1):94-104
Feed intake, in vivo nutrient digestibility and nitrogen utilization were evaluated in male sheep fed different fractions (leaf, pseudostem, corm, whole plant) of enset, untreated or 2% urea‐ and 3% calcium oxide‐ (CaO or lime) treated wheat straw and Desmodium intortum hay as sole diets. All feeds, except D. intortum hay and enset leaf had low crude protein (CP) content. Non‐fiber carbohydrate contents were higher in enset fractions, especially in pseudostem and corm relative to other feeds. Enset leaf and pseudostem had high calcium, phosphorus and manganese contents. Corm, whole enset and D. intortum hay were rich sources of zinc. Daily dry matter and CP intakes were higher (p < 0.05) in sheep fed D. intortum hay (830 and 133 g, respectively) than those fed pseudostem (92 and 7.8 g, respectively). Organic matter digestibilities were highest for corm (0.780) and whole enset (0.776) and lowest for D. intortum hay (0.534) and untreated wheat straw (0.522). The CP digestibility ranged from 0.636 in D. intortum hay to 0.408 in corm. Nitrogen (N) balance was highest (p < 0.05) in D. intortum hay (10.4 g/day) and lowest in corm (?1.3 g/day). Enset leaf could be a useful protein supplement whereas the pseudostem and corm could be good sources of energy. 相似文献
52.
Esayas Mendesil Chemeda Abdeta Abush Tesfaye Zekarias Shumeta Habte Jifar 《Crop Protection》2007,26(12):1817-1825
Surveys were undertaken in six districts of southwestern Ethiopia from July to October 2003 to investigate farmers’ perceptions and management practices of insect pests on traditionally stored sorghum. The survey involved 138 randomly selected farmers who were interviewed using a semi-structured questionnaire. Storage insect pests were perceived as the major insect pests of sorghum. The majority of the farmers estimated sorghum yield losses of up to 50% due to insect damage during storage. High temperature and lack of storage hygiene were cited as the major factors resulting in insect infestation of stored sorghum. Infestations of stored sorghum insect pests were common on different forms of sorghum, which stored in various types of farm storage. Farmers classified sorghum varieties according to the level of resistance to stored sorghum insect pests. Only about 32% of the farmers had access to chemical insecticides for the control of stored sorghum insect pests, while the majority of them used cultural practices and locally available plant materials as storage protectants. 相似文献
53.
Muluneh Tamiru Heiko C. Becker Brigitte L. Maass 《Genetic Resources and Crop Evolution》2008,55(1):115-131
Yam (Dioscorea spp.) is widely grown in many parts of Ethiopia and plays a vital role in local subsistence. Nevertheless, its diversity
has not been studied in detail. A survey covering 339 farm households and eight districts was conducted in the major yam growing
regions of Southern Ethiopia to investigate the diversity and distribution of yam landraces using structured and semi-structured
questionnaires. A total of 37 named landraces were recorded, with a range from one to six (mean 2.9) on individual farms.
Farmers’ decisions regarding the number and type of landraces maintained was influenced by tolerance of the landraces to drought,
their maturity time and market demand. Most landraces had limited abundance and distribution, and only a few dominant landraces
were widely grown. There was also variation amongst districts with respect to diversity, distribution and abundance of the
landraces found. In the majority of the localities surveyed, farmers reported a decreasing trend in the number of landraces
maintained on individual farms and in the overall yam production. Besides, in those limited areas where yam production is
expanding, farmers are increasingly relying on a few selected landraces that mature early. Findings of this study suggest
that local farmers in Wolayita and Gamo-Gofa zones maintain considerable yam diversity that remains to be further explored
for sustainable utilization and conservation of the available genetic resources. 相似文献
54.
M. Bogale E.T. Steenkamp M.J. Wingfield B.D. Wingfield 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(3):369-378
Fusarium solani is a fungal pathogen that infects many different genera of plants. It represents one of the two Fusarium spp. commonly isolated from agricultural soils and plant tissues in Ethiopia. To determine the diversity of F. solani in Ethiopia, we studied 43 isolates using Amplified Fragment Length Polymorphism (AFLP) and nucleotide sequences of the Translation
Elongation Factor 1α (TEF-1α) and β-tubulin genes. TEF-1α sequences from GenBank, representing previously described species
and clades of the F. solani-Haematonectria haematococca complex, were also included for comparative purposes. Phylogenetic analyses of the TEF-1α data separated the isolates into
three groups corresponding with the three previously described clades (Clades 1–3) for this fungus. The Ethiopian isolates
aggregated into one group corresponding to Clade 3. TEF-1α, β-tubulin and AFLPs further separated the Ethiopian isolates into
a number of clusters and apparently novel phylogenetic lineages. Although the biological and ecological significance of these
lineages and clusters is unclear, our data show that the Ethiopian agricultural environment is rich in species and lineages
of the F. solani-H. haematococca complex. 相似文献
55.
Diversity and production of Ethiopian dry woodlands explained by climate- and soil-stress gradients 总被引:1,自引:0,他引:1
Dry woodlands cover about 14% of the total African land surface and represent about 25% of the natural vegetation. They are characterized by a seasonal climate, with a dry season of 4-7 months. Large parts of these ecosystems are degrading due to grazing, fire or exploitation by people. We studied species richness and productivity patterns of dry woodlands in Ethiopia. For such ecosystems, classic productivity and diversity hypotheses predict that species richness and productivity increase as the wet season length increases, and decrease when soil conditions create water stress. We inventoried and measured trees in 18 2-ha plots distributed in two sites, one higher altitude site with a shorter wet season than the lower altitude site. We found that the stand volume per hectare was lower in the site with a shorter wet season. Across all 18 plots we observed that stand volume decreased with soil water stress (estimated from texture and depth). This was in line with the prediction. The species richness was lower in the short-wet-season woodlands, but was unaffected by variation in soil conditions. This suggests that climate driven constraints (wet season length) set the limits to species richness, and not soil conditions. As far as we know, this study is one of the first studies that evaluated these productivity and diversity hypotheses for dry African woodlands. 相似文献
56.
Land degradation is the major economic and environmental threat in Ethiopia. Since the 1960s, the various traditional land management systems have undergone unprecedented changes. Within the context of farmers' awareness of land degradation and local responses to the problems, the objective of this study is to examine the resilience and stability of traditional land management knowledge in Southern Ethiopia. Data were collected using interviews, group discussions and field observations. Results of the study demonstrate that farmers have a wealth of experience in identifying the severity, dynamics and causes of soil erosion and soil fertility decline and grazing land deterioration. In response to these problems, farmers have developed a wide range of traditional land management practices, supported across the generations by the traditional law (benee woga) and norms. However, recent changes include reduction and abandonment of fallowing, modification of crop rotation and large‐scale reduction of manuring. The current practices used to fulfil livelihood requirements are the main driving forces that affect the resilience of the system. Thus, environmental and land use management planning should consider rehabilitating land not only based on traditional land management knowledge but also with regards to raising its agricultural productivity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
57.
Reservoir sedimentation is the most serious threat for water harvesting schemes and hydroelectric power dams in Ethiopia. Designing watershed conservation strategies and management is crucial to reduce the rate of sedimentation. Because different landscape types have varying potentials for enhancing erosion processes, site‐ and process‐specific conservation measures are needed to target an appropriate intervention to the most needed locations. In this study, a GIS‐based distributed soil erosion/deposition model was used to simulate the potential of land‐use and cover (LUC) changes and conservation measures for reducing water induced soil erosion and potential sediment yield for two catchments in northern Ethiopia. LUC change and conservation measures targeted gully and stream buffers, protection of steep slopes and protection of areas with soil loss greater than a given threshold. The results show that land management measures targeted at hot‐spot areas of erosion and gully formation could reduce potential annual sediment yield from catchments by approximately 60% compared with the current losses. The study demonstrates the potential of a GIS‐based LUC‐redesign approach as a tool for optimizing land‐use and management strategies to reduce run‐off and erosion rates in the highlands of northern Ethiopia. 相似文献
58.
This paper presents a detailed geomorphological overview of the landforms and processes characterizing the Dessie basin, a small graben located on the western Afar Margin (Ethiopia), which is a physiographic province characterized by small, closed basins and mountain ranges produced by regional extension. Large-scale geomorphological survey and mapping of the basin allowed to point out the noteworthy morphodynamic role of the present-day slope processes, including numerous landslides of different typology and size. These processes heavily interact with the built-up area of Dessie town, one of the most important cities of Ethiopia with ca. 200,000 inhabitants, which occupies a large part of the basin floor. The potential incidence of landslides of different typology in the basin and their possible impact on the urban settlement are put in relation with the distribution of the different landform units which make up the basin surface. 相似文献
59.
Achenef M. Markos T. Feseha G. Hibret A. Tembely S. 《Tropical animal health and production》1999,31(1):15-24
An investigation was carried out at Debre Berhan, Ethiopia, between 1996 and 1997, into the epidemiology of coenurosis in Menz and Horro breeds of sheep. A total of 37 heads from clinically sick and 183 heads from apparently healthy sheep were examined post mortem for the presence of the cystic larvae of Taenia multiceps, of which 37 and 5 heads, respectively, contained 1 to 8 coenurus cysts (diameter 0.8 to 6.5 cm). The bladder worms were located in the cerebral hemisphere in 96% of the cases (43% and 57% for left and right, respectively), 4% being in the cerebellum. Prediction of cyst locations based on the direction of circling and head deviation had a 62% success rate. A retrospective study generated from the health record book at the ILRI Debre Berhan Station in 1992–1996 (199 Horro and 174 Menz) revealed that the incidence of coenurosis ranged from 2.3% to 4.5%. There was no significant breed difference in the incidence. The age of the affected sheep ranged from 4 to 96 months, with a mean of 19.3 months, and 72% of the cases were within the range of 6 to 24 months. In a complementary survey on necropsied stray dogs, 8 out of 17 were positive for Taenia spp. Both studies confirm the endemicity of coenurosis at the ILRI Debre Berhan Research Station. Appropriate strategies for the control of coenurosis are suggested. 相似文献
60.
Endalkachew?Wolde-meskelEmail author Trygve?Berg N.?Kent Peters ?sa?Frosteg?rd 《Biology and Fertility of Soils》2004,40(1):55-66
The nodulation of provenances of Acacia seyal, Acacia tortilis and Faidherbia albida, and other indigenous multipurpose tree species were tested in 14 different soil samples collected from diverse agro-ecological zones in southern Ethiopia. Associated rhizobia were isolated from these and from excavated nodules of field standing mature trees, and phenotypically characterized. Indigenous rhizobia capable of eliciting nodules on at least one or more of the woody legume species tested were present in most of the soils. Tree species were markedly different in nodulation in the different site soils. Sesbania sesban and Acacia abyssinica showed higher nodulation ability across the different sites indicating widespread occurrence of compatible rhizobia in the soils. The nodulation patterns of the different provenances of Acacia spp. suggested the existence of intraspecific provenance variations in rhizobial affinity which can be exploited to improve N fixation through tree selection. Altogether, 241 isolates were recovered from the root nodules of trap host species and from excavated nodules. Isolates were differentiated by growth rate and colony morphology and there were very fast-, fast-, slow-, and very slow-growing rhizobia. The bulk of them (68.5%) were fast-growing acid-producing rhizobia while 25.3% were slow-growing alkali-producing types. Fast-growing alkali-producing (2.9%) and slow-growing acid-producing strains (3.3%) were isolated from trap host species and excavated nodules, respectively. All isolates fell into four colony types: watery translucent, white translucent, dull glistering and milky (curdled) type. The diversity of indigenous rhizobia in growth rate and colony morphology suggested that the collection probably includes several rhizobial genera. 相似文献