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   71篇
  免费   2篇
林业   6篇
农学   9篇
  15篇
综合类   3篇
农作物   11篇
水产渔业   7篇
畜牧兽医   14篇
园艺   2篇
植物保护   6篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2020年   5篇
  2019年   6篇
  2018年   3篇
  2017年   5篇
  2016年   6篇
  2015年   2篇
  2014年   5篇
  2013年   8篇
  2012年   4篇
  2011年   4篇
  2010年   4篇
  2009年   4篇
  2008年   4篇
  2007年   5篇
  2006年   1篇
  1999年   1篇
  1997年   1篇
  1975年   1篇
排序方式: 共有73条查询结果,搜索用时 17 毫秒
21.
To study the effects of different levels of drought stress on root yield and some morpho-physiological traits of sugar beet genotypes, a study was conducted in the research farm of Islamic Azad University of Birjand, Iran in 2013 as strip-split plot experiments based on randomized complete block design. Different levels of drought stress were considered as vertical factor in three levels including normal irrigation, moderate stress, and severe stress. Horizontal factor was assigned to five varieties of sugar beet. Drought stress had a significant effect on root dry weight, total dry weight, root yield, and leaf temperature at 1% probability level and on leaf dry weight, crown dry weight, and harvest index at 5% probability level. Drought stress had an adverse effect on root yield of investigated genotypes of sugar beet. Under normal conditions, the mean of root yield was higher than middle and severe drought stress. Different investigated genotypes of sugar beet responded to drought stress based on their yield potential. The highest positive correlation of root yield was observed with root dry weight (r=0.977**). Stepwise regression analysis and path coefficient analysis showed that root dry weight and petiole dry weight are the most important traits that can affect root yield of sugar beet under drought stress and can used as selection criteria in investigated cultivars of sugar beet. Finally, 7221 genotypes can be considered as tolerant genotypes in the next studies. In comparison, Jolgeh cultivar (as susceptible control) yielded well in areas with normal irrigation, but under moderate and severely stresses its root yield was reduced.  相似文献   
22.
23.
Accurate estimation of reference evapotranspiration (ETo) is essential for water resources management and irrigation systems scheduling, especially in arid and semiarid regions such as Iran. In the present research, constant coefficients of Hargreaves–Samani (CH–S) and Priestley–Taylor (CP–T) equations were locally calibrated to estimate the ETo based on the FAO–Penmen–Monteith (PM) method as standard method. For this purpose, meteorological data of eight synoptic stations located in the northwest of Iran were used during the period of 1997–2008. The outcomes showed that the values of CH–S and CP–T were 0.0026 (instead of 0.0023) and 1.68 (instead of 1.26), respectively. Also, at stations with high wind speed, the values of calibrated coefficients of CH–S and CP–T were maximum. Then, the estimated ETo values using adjusted CH–S and CP–T coefficients were compared to the obtained actual ETo values by PM method using root mean square error and mean bias error indices. The results indicated that the new calibrated H–S and P–T equations have good agreement with the PM method for estimation of the ETo. Moreover, the equation of Ravazzani et al. was calibrated in the studied region. It was concluded that in general, the mentioned equation was shown better performance than original H–S equation.  相似文献   
24.
Evaluation of genotype × environment interaction (GEI) is an important component of the variety selection process in multi-environment trials. The objectives of this study were first to analyze GEI on seed yield of 18 spine safflower genotypes grown for three consecutive seasons (2008–2011) at three locations, representative of rainfed winter safflower growing areas of Iran, by the additive main effects and multiplicative interaction (AMMI) model, and second to compare AMMI-derived stability statistics with several stability different methods, and two stability analysis approaches the yield-stability (Ysi) and the GGE (genotype + genotype × environment) biplot that are widely used to identify high-yielding and stable genotypes. The results of the AMMI analysis showed that main effects due to genotype, environment, and GEI as well as first six interaction principle component axes (IPCA1 to 6) were significant (P < 0.01). According to most stability statistics of AMMI analyses, genotypes G5 and G14 were the most stable genotypes across environments. According to the adjusted stability variance (s2), the high-yielding genotype, G2, was unstable due to the heterogeneity caused by environmental index. Based on the definition of stable genotypes by regression method (b = 1, S d 2  = 0), genotypes G11, G9, G14, G3, G12 and G13 had average stability for seed yield. Stability parameters of Tai indicated that genotype G5 had specific adaptability to unfavorable environments. The GGE biplot and the Ysi statistic gave similar results in identifying genotype G2 (PI-209295) as the best one to release for rainfed conditions of Iran. The factor analysis was used for grouping all stability parameters. The first factor separated static and dynamic concepts of stability, in which the Ysi and GGED (i.e., the distance from the markers of individual genotypes to the ideal genotype) parameters had a dynamic concept of stability, and the other remaining parameters had static concept of stability.  相似文献   
25.
BACKGROUND: Knowing that adenoviral vectors could initiate innate immunity, the ability of E1-deleted recombinant adenovirus (Ad-E1Delta) in induction of B7.1 and IL-2 molecules was studied. METHODS: The expression of green fluorescent protein in C1498 cells following transfection of these cells with adenovirus green fluorescent protein vector confirmed the ability of adenovirus vectors in infecting the cells and inducing the expression of the gene of interest. The expression of B7.1 molecule on the surface of the cells was assayed upon infection with Ad-E1Delta vector. Adenovirus-IL-2/B7.1 vector capable of inducing IL-2 and B7.1 expression in the cells was used as the positive control vector. RESULTS: According to the FACS results, about 4.17% of normal cells expressed B7.1 on their surface, while this level was increased in Ad-E1Delta transduced cells up to 14.43%. These results demonstrate that Ad-E1Delta vector considerably (about 3 folds) increases the expression of B7.1 on the cells. No detectable IL-2 was secreted into the medium of non-transduced and Ad-E1Delta transduced cells. CONCLUSION: Data indicate that the infection of C1498 cells with recombinant adenoviruses stimulates expression of B7.1 on the cell surface rather than secretion of IL-2 into the medium.  相似文献   
26.
Fumigant activity of essential oil vapors distilled from Carum copticum C. B. Clarke and Vitex pseudo-negundo Hand I. MZT. was tested against eggs, larvae and adults of Callosobruchus maculatus (F.). Fumigant toxicity was assessed at 27 ± 1°C and 60 ± 5% RH, in dark condition. The influence of different concentrations of the essential oil vapors on egg hatchability, larval and adult mortality was significant. Data probit analysis showed that lethal concentration of the essential oil to kill 50% of the population (LC50) for egg, larvae and adult were found to be 1.01, 2.50 and 0.90 μl/l air of C. copticum oil, followed by 2.20, 8.42 and 9.39 μl/l air essential oil of V. pseudo-negundo, respectively. Between these essential oils, C. copticum was almost more toxic than V. pseudo-negundo on all growth stages of C. maculatus. The present study suggests that essential oils from these medicinal plants may be potential grain protectants as botanical alternative fumigants and could be used in the management of various life stages of C. maculatus.  相似文献   
27.
Partitioning of the genotypes by environment interaction (GEI) is important in order to determine the nature of the GEI. The objectives of this study were to assess the presence and nature of GEI for nine agronomic traits of rapeseed cultivars, and to identify cultivars with favorable levels of stable oil production. Nine rapeseed cultivars, including seven open pollinated and two hybrids, Hyola308 and Hyola401, were grown in ten environments under rain-fed warm areas of Iran. The GEI was significant for all traits and was partitioned into components representing heterogeneity due to environmental index and the remainder of the GEI. Among the all traits with a highly significant heterogeneity, the largest amount of heterogeneity removed from the GEI was for seeds per pod and seed weight. We found GEIs for both oil content and seed yield were largely influenced by differences in correlations among pairs of cultivars (86.8 and 71.4% of the GEI sum of squares, respectively), suggesting that crossover GEIs (i.e., change in genotype rankings among environments) are present. The mean correlation of each cultivar with all other cultivars ([`(r)]ii \bar{r}_{{ii^{\prime}}} ) ranged from 0.53 to 0.83 for oil content and 0.86 to 0.96 for seed yield. A comparison was done of the significance of Sh-σi2 (stability variance derived from total GEI) and Sh-Si2 (adjusted stability variance derived from residual GEI) assignable to each genotype for oil content and seed and oil yield. Based on Sh-σi2, three cultivars were unstable for oil content, whereas six cultivars were unstable for seed and oil yield. The removal of heterogeneity revealed that one unstable cultivar for oil content and three unstable cultivars for oil yield were judged to be stable. All cultivars with [`(r)]ii \bar{r}_{{ii^{\prime } }}  ≤ 0.63 were labeled unstable for oil content, whereas all with [`(r)]ii \bar{r}_{{ii^{\prime } }}  ≤ 0.94 were considered unstable for seed yield. The relationships between [`(r)]ii \bar{r}_{{ii^{\prime } }} and Sh-σi2 were significant (P < 0.01) for oil content and seed yield. The results of rank correlation coefficients showed significant positive correlations of Yield-Stability statistic (YSi) with oil content and oil yield. Cultivars such as Option500 and Hyola401 were identified as having stable, high levels to seed yield and oil content.  相似文献   
28.
29.
High levels of guanidinoacetate acid (GAA) deteriorate growth response in broiler chickens. We propose using coenzyme Q10, an antioxidant, and taurine (TAU), a methyl donor, to cope with the situation when high level of GAA included in diet. GAA was supplemented at 0 (control), 0.75, 1.5 and 2.25 g/kg in isoenergetic and isonitrogenous diets and fed to broilers (Cobb 500) from 1 to 40 days post‐hatch. Three additional diets were prepared by adding CoQ10 (40 mg/kg), TAU (40 mg/kg) or their combination (both CoQ10 and TAU at 40 mg/kg) to the 2.25 g/kg GAA group. The experimental design used was a completely randomized design. While weight gain (p = 0.038) and feed conversion ratio (p = 0.024) improved when GAA added at 1.5 g/kg, higher supplementation (2.25 g/kg) deteriorated these responses. These responses, however, were significantly restored by using CoQ10, TAU or their combination. Abdominal fat deposition was significantly decreased when TAU added to broiler diets by virtue of upregulating peroxisome proliferator‐activated receptor alpha. Supplementing broiler diets with CoQ10 and TAU or their combination significantly decrease ascites mortality. In conclusion, CoQ10 and TAU have shown beneficial effects when high level of GAA included in broiler diets.  相似文献   
30.
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