首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  免费   1篇
林业   1篇
农学   3篇
  2篇
农作物   1篇
畜牧兽医   12篇
植物保护   2篇
  2023年   1篇
  2021年   1篇
  2019年   1篇
  2015年   1篇
  2014年   1篇
  2013年   1篇
  2011年   2篇
  2008年   1篇
  2007年   1篇
  2006年   2篇
  2005年   3篇
  2004年   2篇
  2001年   1篇
  1999年   1篇
  1997年   1篇
  1992年   1篇
排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
Approaches are needed to broaden the genetic base and improve earliness and yield potential of large-seeded beans under sustainable cropping systems. The objective of this research was to develop adapted dwarf bean populations having a commercial seed quality and yield suitable for the production in the South of Europe. The original base populations were produced from crosses between genotypes within each Mesoamerica, Nueva Granada and Peru races, and between Peru and Nueva Granada, and Mesoamerica and Nueva Granada races. Visual mass selection for plant performance was practised in the F2 and F3 generations. In the F4 and F5, single plants were harvested under two cropping systems (sole cropping and intercropping with maize). From F4, selection was based on precocity, combined with seed yield and seed commercial type. The F4:7 selected lines from each original population were compared with their parents and five checks at four environments and two cropping systems. Differences among environments, populations, parents and checks were observed for all traits. Under intercropping with maize, there was a 50% reduction in seed yield. Yield of parents and checks belonging to Andean South American races, intraracial (Nueva Granada × Nueva Granada) and interracial (Nueva Granada × Peru) populations, was higher than that of those of Middle American origin. Intraracial crosses within large-seeded Andean South American (Peru race) and Middle American gene pools (Mesoamerica race) did not produce lines yielding more than the highest yielding parent. Only two large-seeded lines selected from crosses between small- and large-seeded gene pools out-yielded the best parent and check cultivar.  相似文献   
2.
Scrapie is a prion disease characterised by the accumulation of the pathological associated form of cellular prion protein (PrP(SC)) in the central nervous system. Susceptibility to scrapie is associated with polymorphism in the ovine prion protein (PrP) gene. The European Union has implemented scrapie control programs, relying on selective breeding for scrapie resistance; the use of ARR-carrier and the exclusion of VRQ-carrier were recommended. In this study, 4323 individuals from Rasa Aragonesa Sheep breed were genotyped for the PrP gene and the individual estimated breeding values (EBV) for prolificity were calculated. Most represented PrP alleles do not work against prolificity. Only a significant association between VRQ/VRQ genotype and a lower EBV was observed (p = 0.027, eta2 = 0.002). Therefore, avoiding reproduction of VRQ/VRQ individuals would not cause negative effect regarding prolificity.  相似文献   
3.
Several ethyl 2,3-dihydro-3-oxoisothiazolo[5,4-b]pyridine-2-alkanoate derivatives were synthesized as herbicides. Only 5-methyl derivatives inhibited both hypocotyl and root growth in the lettuce (Lactuca sativa L.) seedling test at 100 mg litre-1. Only ethyl propionate and valerate derivatives showed significant inhibition at 0·1 mg litre-1, whereas ethyl acetate or butyrate derivatives were inactive. Contrary to unoxidized derivatives, the inhibitory effect of 1-oxide and 1,1-dioxide derivatives was strongly dependent on concentration; ethyl 2,3-dihydro-5-methyl-3-oxoisothiazolo[5,4-b]pyridine-2-propionate 1,1-dioxide inhibited 100% of germination at 100 mg litre-1 and 45% of lettuce seedling growth at 0·1 mg litre-1. Quantitative structure–inhibition of growth relationship analysis carried out by adaptive least-squares (ALS) method gave a good correlation with small and hydrophobic 5-substituents as well as with odd carbon-chain ethyl alkanoates in position 2. Active compounds did not show auxin-like activity from 0·1 to 100 mg litre-1. © 1997 SCI.  相似文献   
4.
5.
6.
A 6-year-old, sterile, Blanca Celtibérica breed adult doe was referred to our faculty. The doe had external female genitalia, a short anogenital distance, and normally shaped udders. Masculinization signs in the head shape and male behavior were also noted at the time of referral. Genetic analysis demonstrated normal 2n = 60 XX karyotype and an absence of the sex-determining region Y (SRY). The animal was homozygous for a DNA deletion responsible for the Polled Intersex Syndrome (PIS). A uterus and 2 uterine horns were present at the postmortem examination. Gartner's ducts and degenerated Wolffian derivatives persisted. There were 2 intra-abdominal testicle-like structures, one of which consisted of epididymal and deferent ducts. An advanced Leydig cell tumor, resulting in almost total destruction of the intratesticular structures, was also observed. Leydig cell tumors usually produce testosterone. Thus, these histologic findings are compatible with the evident virilization.  相似文献   
7.
Wild populations of common bean pertainingto the Andean gene pool are distributedfrom southern Peru to northern Argentina.The objectives of this study were todetermine the genetic structure of Andeanlandraces from northern Argentina, as oneof the potential domestication sites of theAndean domesticated gene pool, and toestablish a correspondence between Andeanprimitive landraces and wild populationsthat might have served as the source ofdomesticated bean. Forty-four landraces and21 wild populations representing thediversity of common bean in northernArgentina were included in this study. Results indicated that Andean gene pool inArgentina has a large genetic base on thebasis of morphological and adaptivevariability and biochemical analysis. Theexistence of introgressed populations withsympatric wild forms was evidenced.  相似文献   
8.
9.

BACKGROUND

Birds have been shown to reduce pest effects on various ecosystem types. This study aimed to synthesize the effect of birds on pest abundance, product damage and yield in agricultural and forest systems in different environments. Our hypothesis is that birds are effective pest regulators that contribute to a reduction in pest abundance, enhancement of yield quality and quantity and economic profit, and that pest regulation may depend on moderators such as the type of ecosystem, climate, pest, and indicator (ecological or economic).

RESULTS

We performed a systematic literature review of experimental and observational studies related to biological control in the presence and absence of regulatory birds. We retained 449 observations from 104 primary studies that were evaluated through qualitative and quantitative analyses. Of the 79 studies with known effects of birds on pest regulation, nearly half of the 334 observations showed positive effects (49%), 46% showed neutral effects, and very few (5%) showed negative effects. Overall effect sizes were positive (mean Hedges’ d = 0.38 ± 0.06). A multiple model selection retained only ecosystem and indicator types as significant moderators.

CONCLUSION

Our results support our hypothesis that there is a positive effect of avian control of pests for each analyzed moderator and this effect was significant for both ecological and economic indicators. Avian regulation of pests is a potential effective approach for environmentally friendly pest management that can reduce pesticide use regardless of the context of implementation. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   
10.
In this work, we studied retrospectively the influence of several factors on semen quality of the Spanish Purebred (SPB) stallion. Among these factors, we considered stallion age, season, and interval between two consecutive collections. The semen was collected from 11 SPB stallions (634 ejaculates). Semen quality was evaluated based on volume, concentration, and motility of the ejaculates. Results showed that the semen collected in autumn and winter was more concentrated in comparison with that collected in spring and summer, when the volume of ejaculate was the highest. Those ejaculates collected from younger stallions were characterized by having the smallest volume and the highest sperm concentration. When incorporating an SPB stallion into a program of artificial insemination, it is important to take into account all of these factors to achieve the maximum reproductive potential of the animal.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号