全文获取类型
收费全文 | 57篇 |
免费 | 2篇 |
专业分类
农学 | 9篇 |
基础科学 | 1篇 |
25篇 | |
综合类 | 7篇 |
农作物 | 2篇 |
水产渔业 | 2篇 |
畜牧兽医 | 10篇 |
园艺 | 3篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2018年 | 1篇 |
2015年 | 2篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有59条查询结果,搜索用时 0 毫秒
41.
Can cultivars from participatory plant breeding improve seed provision to small-scale farmers? 总被引:1,自引:0,他引:1
Seed provision for small-scale farmers deals with multiple constraints. These include, on the supply side, high seed production
costs and poor adaptedness of the cultivars, and on the demand side, anticyclical demand and low and variable sales. Approaches
to improve seed provision to this sector of farmers have so far not been very successful. This paper discusses how well-adapted
cultivars developed through participatory plant breeding (PPB) initiatives create new opportunities for production and distribution
of quality seed. It reviews supply and demand-side issues, based on research and experiences with seed production. Given better
adaptation of PPB-cultivars, the diffusion of seed of PPB initiatives should not be a major bottleneck. But constraints in
the provision of quality seed from cultivars that are commonly used remain and need to be addressed. Major points of attention
are cost-effective seed production and distribution, high information linked transaction costs, and appropriate seed production
technology. Research on these issues is needed to understand farmers’ seed demand. At the same time, these issues need to
be taken into account in new seed production initiatives that apply integrated approaches. Long term commitment by farmers
to produce, distribute and use seeds is a condition. Even if seed production is not economically sustainable at household
or organization level, farmer-based seed systems generate benefits to society as a whole that justify long term public investment
to maintain them. 相似文献
42.
Multiple endopeptidases as biochemical marker for resistance of winter wheat to Pseudocercosporella herpotnchoides (Fron) Deighton. Electrophoretic patterns of primary leaf endopeptidases in breeding material derived from crosses between different winter wheat genotypes and amphidiploids (Triticum turgidum×Aegilops ventricosa) were compared with those of cultivars susceptible to Pseudocercosporella herpotrichoides. The results indicate that the multiple endopeptidase EP-1 coded by Wheat chromosome 7 D is absent in the international known lines ‘VPM 1’ and ‘Roazon’ and in all 24 winter wheat selections with increased resistance to P. herpotrichoides. A close relationship between the absence of EP-1 and the introduction of Aegilops ventricosa resistance is assumed. The use of this biochemical marker in wheat breeding is proposed. 相似文献
43.
Elaine McElhinny Eduardo Peralta Nelson Mazón Daniel L. Danial Graham Thiele Pim Lindhout 《Euphytica》2007,153(3):373-384
Summary Field trials were carried out in Ecuador with two indigenous communities, Ninín Cachipata and La Esperanza, to determine farmers’
preferences for quinoa (Chenopodium quinoa Willd.) cultivars and to improve PPB processes. More women than men participated, reflecting that quinoa, a primarily subsistence
crop, is mainly managed by women. Farmers’ field selection criteria for quinoa in the field were mostly based on yield, earliness
and plant colour; however only breeders’ measurements of yield and panicle height significantly correlated to farmer selection
scores. Older women gave higher scores than younger women or men, apparently due to a concept of no cultivar being without
value. Working in same gender pairs improved evaluation richness. INIAP technicians were more discriminating in their evaluations
than farmers. They also used additional selection criteria of disease resistance and uniformity. At seed selection, farmers
from Ninín Cachipata, where food security is not assured, chose lines based on yield, while farmers from La Esperanza, where
resources are less limiting, also considered seed size, colour, saponin content and marketability. Field characteristics were
not taken into consideration at seed selection, signifying that farmers are less interested in those characteristics, or that
it was difficult for them to correlate field data when presented in tabular form with seed characteristics. Future trials
with small farmers should have fewer lines or replications to avoid farmer fatigue during evaluation. Farmers who grow primarily
for subsistence in semi-arid environments have more interest in growing quinoa, and more to gain from having improved cultivars;
therefore future participatory efforts should focus on them. 相似文献
44.
In wheat, eyespot caused by PseudoCercosporella herpotrichoides, is one of the main foot‐rot diseases. Yield losses up to 40% occur in some years. Plant protection by fungicide application is possible, but a better way is through resistance breeding. Two resistance sources are currently used: Aegilops ventricosa and the old French variety ‘Cappelle Desprez’. A new source of resistance has been found in the accession AE120 of Ae. kotschyi from the Gatersleben gene bank with the genome constitution UUSvSv. This accession has been crossed and backcrossed twice to susceptible wheat varieties, and in each generation, plants with a relatively high level of resistance have been selected. From this material, lines have been developed and tested in F6 to F8. Finally, several lines could be classified as moderately resistant, such as the French variety ‘Cappelle Desprez’ after resistance determination during milk ripeness (DC75). No line reached the high resistance level achieved with Pch‐1 from Ae. ventricosa. The yield of these lines under infection conditions was higher compared with ‘Cappelle Desprez’. The line 6018‐96‐3 showed a high yield of 64.3 dt/ha compared with 59.6 dt/ha, on the average, in combination with the best expression of eyespot resistance in the adult growth stage over 3 years. 相似文献
45.
Nina Neykova Joy Obando Raimund Schneider Chris Shisanya Sören Thiele‐Bruhn Frank M. Thomas 《植物养料与土壤学杂志》2011,174(5):742-749
Intercropping is an important and widespread land‐management system in the tropics. At two agricultural sites in Central Kenya differing in elevation and soil type Haplic Nitisols (eutric) and Vitric Gleysols (eutric, epiclayic, endoclayic), we investigated the vertical root distributions using the trench wall profile method in single‐crop systems of maize (Zea mays L.) and in intercropping systems of maize and legumes (common bean, Phaseolus vulgaris L.; pigeon pea, Cajanus cajan [L.] Millsp.) to test for possible differences in the use of water and nutrient resources. The physico‐chemical soil properties of the sites were similar and imposed no restrictions to the vertical growth of the roots into soil depths of 1.4 m. The vertical distributions of the fine roots (?? 0.5–2 mm) and very fine roots (?? < 0.5 mm) were quantified by calculating the parameter β which was computed from the cumulative fraction (Y) of the root densities along the depth (d) of the soil profiles (Y = 1 – βd). We found no consistent differences between the single‐crop and the intercropping systems in the rooting depth down to 1.4 m. However, higher β values for fine roots of the intercropping systems were indicative of a more homogeneous vertical root distribution than in the single‐crop fields. In the intercropping fields, 50% of the total number of fine roots were distributed over the uppermost 36 cm of the soil, whereas in the single‐crop fields, 50% of the fine roots were concentrated in the uppermost 15–21 cm. Medium‐sized roots (?? > 2–5 mm) were detected in the intercropping fields only. The more homogeneous root distribution in the intercropping fields likely indicates a more efficient use of the limited resources nutrients and water. 相似文献
46.
47.
48.
Gesine Witt Carina Bartsch Gladys A. Liehr Rajko Thiele Michael S. McLachlan 《Journal of Soils and Sediments》2010,10(7):1388-1400
Purpose
The speciation of polycyclic aromatic hydrocarbons (PAHs) in sediment-porewater systems affects both the chemical fate and bioavailability of these compounds. PAHs may be dissolved or sorbed to sediment particles or dissolved organic carbon (DOC). Furthermore, soot carbon has been shown to control the sorption of PAHs onto particles in natural waters. The present study investigates the distribution of individual PAHs among these three phases by examining sediments from the western Baltic Sea, focusing on a highly contaminated former dumping area and evaluating the importance of soot-carbon partitioning. 相似文献49.
50.
The International Potato Center (CIP) and collaborating institutions implemented an intensive research programme over a period
of 25–30 years on the use of botanical seed of potato as an alternative way of growing a potato crop. The use of botanical
or ‘true’ potato seed (TPS) had many advantages over the use of seed tubers. Potentially, the use of TPS was especially attractive
for small-scale farmers in developing countries. The difference of using TPS as compared to using seed tubers meant in many
respects the development of a new crop–commodity chain, requiring research on breeding, seed production, agronomy and marketing
aspects. This research made it possible to produce potatoes from TPS at commercial scale: it removed a number of important
constraints in the uniformity and earliness of the TPS varieties and in seed physiology. Experimentation and adoption by farmers
in a wide range of countries showed that the technological advantages of using TPS were only translating in economical benefits
as compared to tuber seed when the last one was costly or not available. Since the economic performance of seed tubers is
likely to continue to fluctuate, TPS remains an interesting alternative. Study of the use of TPS in various countries could
contribute to better understanding of factors that promote or inhibit crop technology innovation. The article gives an overview
of the various areas of TPS research in CIP and presents information on the application of TPS technology in several developing
countries. 相似文献