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   98篇
  免费   5篇
林业   1篇
农学   15篇
  15篇
农作物   9篇
水产渔业   33篇
畜牧兽医   18篇
园艺   4篇
植物保护   8篇
  2022年   4篇
  2021年   4篇
  2020年   6篇
  2019年   6篇
  2018年   9篇
  2017年   5篇
  2016年   9篇
  2015年   2篇
  2014年   15篇
  2013年   14篇
  2012年   8篇
  2011年   4篇
  2010年   2篇
  2009年   4篇
  2008年   4篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2003年   2篇
  1999年   1篇
排序方式: 共有103条查询结果,搜索用时 15 毫秒
1.
The centre of origin of the globally distributed wheat pathogen Parastagonospora nodorum has remained uncertain because only a small number of isolates from the Fertile Crescent were included in earlier population genetic and phylogeographic studies. We isolated and genetically analysed 193 P. nodorum strains from three naturally infected wheat fields distributed across Iran using 11 neutral microsatellite loci. Compared to previous studies that included populations from North America, Europe, Africa, Australia, and China, the populations from Iran had the highest genetic diversity globally and also exhibited greater population structure over smaller spatial scales, patterns typically associated with the centre of origin of a species. Genes encoding the necrotrophic effectors SnToxA, SnTox1, and SnTox3 were found at a high frequency in the Iranian population. By sequencing 96 randomly chosen Iranian strains, we detected new alleles for all three effector genes. Analysis of allele diversity showed that all three effector genes had higher diversity in Iran than in any population included in previous studies, with Iran acting as a hub for the effector diversity that was found in other global populations. Taken together, these findings support the hypothesis that P. nodorum originated either within or nearby the Fertile Crescent with a genome that already encoded all three necrotrophic effectors during its emergence as a pathogen on wheat. Our findings also suggest that P. nodorum was the original source of the ToxA genes discovered in the wheat pathogens Phaeosphaeria avenaria f. sp. tritici 1, Pyrenophora tritici-repentis, and Bipolaris sorokiniana.  相似文献   
2.
3.
Artichoke (Cynara scolymus L.), an edible vegetable from the Mediterranean area, is a good source of natural antioxidants such as vitamin C, hydroxycinnamic acids, and flavones. The antioxidant activity of aqueous-organic extracts of artichoke were determined using three methods: (a) free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH(*)) scavenging, (b) ferric-reducing antioxidant power (FRAP), and (c) inhibition of copper(II)-catalyzed in vitro human low-density lipoprotein (LDL) oxidation. In addition, the present study was performed to investigate the ability of the edible portion of artichoke to alter in vivo antioxidative defense in male rats using selected biomarkers of antioxidant status. One gram (dry matter) had a DPPH(*) activity and a FRAP value in vitro equivalent to those of 29.2 and 62.6 mg of vitamin C and to those of 77.9 and 159 mg of vitamin E, respectively. Artichoke extracts showed good efficiency in the inhibition in vitro of LDL oxidation. Neither ferric-reducing ability nor 2,2'-azinobis(3-ethylbenzothiazolin-6-sulfonate) radical scavenging activity was modified in the plasma of the artichoke group with respect to the control group. Among different antioxidant enzymes measured (superoxide dismutase, gluthatione peroxidase, gluthatione reductase, and catalase) in erythrocytes, only gluthatione peroxidase activity was elevated in the artichoke group compared to the control group. 2-Aminoadipic semialdehyde, a protein oxidation biomarker, was decreased in plasma proteins and hemoglobin in the artichoke-fed group versus the control group. In conclusion, the in vitro protective activity of artichoke was confirmed in a rat model.  相似文献   
4.
The influence of stocking density (1, 2, 4, 6 and 8 kg m?2) was investigated on haematological parameters, growth and fin erosion of great sturgeon (Huso huso) juveniles for a period of 8 weeks. The mean weight of fish at the start of trial was 93.13±1.04 g. After 8 weeks of rearing, the mean weight was 362.4, 319.7, 267, 242.1 and 211.1 in densities 1–8 kg m?2 respectively. The results of this study showed that growth parameters, including condition factor, weight, weight gain, feed conversion ratio, specific growth rate and body weight increase, had a statistically significant difference among treatments (P<0.05). A significant difference (P<0.05) was observed in haematocrit, but the other haematological parameters, including red blood cells, white blood cells (WBC), haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration and differential WBC count, showed no significant effect with stocking density (P>0.05). At the end of the experiment, stocking density had no significant effect on plasma cortisol and glucose concentration. The fin length (dorsal, anal, ventral, pectoral and caudal) of fish was measured to calculate the fin index. According to this index, dorsal, anal, ventral and pectoral fins showed no significant difference among treatments (P>0.05), but the erosion of the caudal fin was significantly different between fish held on 6 and 8 kg m?2 (P<0.05). These results showed that rearing density has a major effect on the growth indices of H. huso. Unlike many other fish, great sturgeon exhibited lower stress responses to high stocking density. This indicates that they are more tolerable to rearing conditions in high stocking densities. With respect to the various effects that density causes on growth, fin erosion and physiological and haematological parameters, better understanding of these phenomena considering different levels of density could have a beneficial impact on many rearing steps of this species.  相似文献   
5.
This study was conducted to examine the effects of different forms and concentrations of ascorbic acid (vitamin C), and different enrichment times (24 and 48 h post ovulation) on egg, embryo and alevin ascorbate concentrations and survival of rainbow trout (enrichment was at the ova stage). In experiments 1 and 2, fertilized eggs were immersed in water containing ascorbate at 0 (control), 100, 1000 mg L?1 l ‐ascorbic acid (AA) and 2000 mg L?1 l ‐ascorbyl monophosphate (AP). In experiment 3, 0 (control), 500 and 1000 mg L?1 AA neutralized (N) with NaOH, 1000 mg L?1 AA non‐neutralized (NN), 1000 and 2000 mg L?1 AP immersions were used. The mean total ascorbic acid (TAA) and dehydroascorbic acid (DHA) concentrations were measured before fertilization, at 3 and 24 h after fertilization, at the eyed stage, and in hatched alevins. We observed significant differences in TAA concentration at different immersion levels at 3 and 24 h after fertilization. Survival decreased significantly depending on the level of vitamin C, pH of the solutions and immersion time. We suggest that when broodstock rainbow trout do not have enough vitamin C in their ovaries, immersion of eggs in 1000 mg L?1 of neutralized AA may be useful.  相似文献   
6.
European Journal of Plant Pathology - It is important to investigate the possibility of pathogen transmission between cultivated and uncultivated hosts due to the role of the latter in pathogen...  相似文献   
7.
Journal of Crop Science and Biotechnology - The analysis of genetic diversity in medicinal plant species can greatly facilitate germplasm conservation and selection for use in breeding schemes. The...  相似文献   
8.
Background: The aim of this study was to determine the prevalence of virulence-associated genes and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) analysis of Campylobacter spp. isolated from children with diarrhea in Iran. Methods: A total of 200 stool specimens were obtained from children under 5 years during July 2012 to July 2013. Detection of C. jejuni and C. coli was performed by standard biochemical and molecular methods. The presence of virulence-associated genes and genetic diversity of isolates was examined using PCR and ERIC-PCR analyses. Results: A total of 12 (6%) Campylobacter spp. were isolated from patients including 10 (4.5%) C. jejuni and 2 (1.5%) C.coli. The flaA, cadF and ciaB genes were present in 100% of isolates, while no plasmid of virB11 gene was present in their genome. The prevalence of invasion-associated marker was 100% among C. coli and was not detected in C. jejuni isolates. The distribution of both pldA and the genes associated with cytolethal distending toxin (CDT) was 58.3% in C. jejuni isolates. Seven distinct ERIC-PCR profiles were distinguished in three clusters using ERIC-PCR analysis. Genotyping analysis showed a relative correlation with geographic location of patients and virulence gene content of isolates. Conclusion: To our knowledge, this is the first molecular survey of Campylobacter spp. in Iran concerning genotyping and virulence gene content of both C. jejuni and C. coli. ERIC-PCR revealed appropriate discriminatory power for clustering C. jejuni isolates with identical virulence gene content. However, more studies are needed to clearly understand the pathogenesis properties of specific genotypes. Key Words: Campylobacter jejuni, Campylobacter coli, Ddiarrhea, Virulence factors  相似文献   
9.
Background:Among different roles of miRNAs in AD pathogenesis, hsa-miR-494-3p and hsa-miR-661 functions are poorly understood. Methods:To obtain the gene targets, gene networks, gene ontology, and enrichment analysis of the two miRNAs, some web servers were utilized. Furthermore, the expressions of these miRNAs were analyzed by qRT-PCR in 36 blood sera, including 18 Alzheimer’s patients and 18 healthy individuals. Results:The in silico analysis demonstrated the highlighted roles of metabolic and cellular response to stress pathways engaged in circulating hsa-miR-494-3p and hsa-miR-661 in AD. The qRT-PCR analysis showed that the downregulated expression level of hsa-miR-661 was statistically significant (p < 0.05). Also, the ROC curve of hsa-miR-661 displayed the significant AUC (p = 0.01). Conclusion:Based on our findings, the metabolic and cellular responses to stress pathways are closely connected to these two miRNAs functions. Besides, the qRT-PCR and Roc curve determined hsa-miR-661 could be as a biomarker for diagnosis or prognosis of AD patients. Key Words: Alzheimer’s disease, Serum, Circulating microRNAs  相似文献   
10.
Drought stress limits crop production in the world. Therefore, employing high-yielding cultivars tolerant to drought is an effective approach to reduce its detrimental effects. To identify drought-tolerant genotypes, 36 wheat genotypes were evaluated during the 2010–2011 and 2011–2012 growth seasons. A field experiment was conducted in a split-plot design with two irrigation treatments (100% field capacity (FC) until harvest and no irrigation after anthesis) as main plots in three replications and genotypes as subplots. Grain yield, its components and drought tolerance indices were measured. Results showed a significant reduction in yield and its components under drought conditions. Grain yield had significant positive correlations with stress tolerance index (STI), mean productivity (MP) index and geometric mean productivity (GMP), while it was negatively correlated with stress susceptibility index (SSI) and tolerance index (TOL) under stress condition. These results indicated that superior genotypes could be selected based on high values of STI, MP and GMP and low value of SSI. The results were validated by principal component analysis (PCA) as it showed genotypes with high PC1 and low PC2 were more desirable. Based on the results, genotypes number 8, 11, 17, 30, 34 and 35 were recognized as suitable for both conditions.  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