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   83篇
  免费   8篇
林业   9篇
农学   4篇
  11篇
综合类   1篇
农作物   22篇
水产渔业   20篇
畜牧兽医   7篇
园艺   1篇
植物保护   16篇
  2023年   2篇
  2022年   1篇
  2021年   7篇
  2020年   3篇
  2019年   10篇
  2018年   8篇
  2017年   7篇
  2016年   3篇
  2015年   4篇
  2014年   3篇
  2013年   11篇
  2012年   5篇
  2011年   2篇
  2010年   4篇
  2009年   2篇
  2008年   5篇
  2007年   3篇
  2006年   5篇
  2004年   1篇
  1997年   1篇
  1992年   1篇
  1984年   2篇
  1983年   1篇
排序方式: 共有91条查询结果,搜索用时 15 毫秒
71.
Endohyphal organisms of endophytic fungi can induce, or promote, beneficial effects of their respective host fungi to the host plant that harbours them. The Cupressaceae plant family (Coniferales) hosts highly bioactive endophytic fungi. Here, we show that a fraction of such endophytic fungi harbours bioactive endohyphal bacteria with a non‐obligatory symbiotic lifestyle. Indeed, 5 of 16 (31.25%) endophytic fungi of Cupressus sempervirens harboured endofungal bacterial strains of Bacillaceae (G+, Bacilli) and Sphingomonadaceae (G?, α‐Proteobacteria), that is Bacillus pumilus (from the fungi Leptosphaeria CSE211 and Pyrenochaeta CSE134), Bacillus subtilis (from the fungi Leptosphaeria CSE212 and Ascorhizoctonia CSE148) and Sphingomonas paucimobilis (from the fungus Ascorhizoctonia CSE195). Notably, each endophytic fungal species contained only one endofungal bacterial species that was stably maintained in symbiosis over several rounds of subculturing. Moreover, we investigated whether cypress endofungal bacteria (CEB) could benefit their host fungus competing with other fungi and bacteria or the host plant against the invading microorganisms. In vitro assays indicated that CEB possessed antagonistic activity against cypress endophytic and pathogenic microbiome. Also, CEB metabolites and volatile compounds (VOCs) exhibited antifungal and antibacterial activity against the target microbiome. Bioactivity of CEB was less than that of the endophytic microbiome of Cupressaceae, on which we reported earlier. In conclusion, our work is the first to document endohyphal bacteria of fungal endophytes of C. sempervirens and the bioactivity of such endohyphal symbionts. These findings implicate a complicated interrelationship among host plant, endophytic microbiome and endofungal bacteria, which might be of high importance for evolutionary, as well as environmental and agricultural studies. Eventually, endohyphal bacteria may be introduced as a novel source for lead molecule discovery.  相似文献   
72.
The effect of strand spacing and twist multiplier on strength of Siro-spun yarns with reference to the yarn structural parameters was investigated. Of the various structural parameters for staple yarns, fiber migration has a crucial influence on the yarn strength, which in turn to a considerable extent is influenced by the strand spacing and twist multiplier. Achieving the objectives of this research, the yarns were produced from lyocell fibers at five strand spacings and four different twist multipliers. Tracer fiber technique combined with image analysis were utilized to study the yarn migration parameters. Afterwards, the yarns were subjected to uniaxial loading by a CRE tensile tester. The measured results are presented in forms of diagrams and tables. The findings reveal that, as strand spacing is increased, yarn tenacity increases up to strand spacing of 8 mm beyond which it reduces. Analysis of the results indicates that the higher tenacity values at the strand spacing of 8 mm can be attributed to the higher mean fiber position, higher migration factor, higher proportion of broken fibers and lower hairiness.  相似文献   
73.
We observed robust coupling between the high- and low-frequency bands of ongoing electrical activity in the human brain. In particular, the phase of the low-frequency theta (4 to 8 hertz) rhythm modulates power in the high gamma (80 to 150 hertz) band of the electrocorticogram, with stronger modulation occurring at higher theta amplitudes. Furthermore, different behavioral tasks evoke distinct patterns of theta/high gamma coupling across the cortex. The results indicate that transient coupling between low- and high-frequency brain rhythms coordinates activity in distributed cortical areas, providing a mechanism for effective communication during cognitive processing in humans.  相似文献   
74.
Abstract

In order to evaluate the effect of different fertilizers’ sources on micronutrients’ content and sugar quality of sugar beet, three fertilizers’ sources include spent mushroom compost (SMC) (29 t/ha), sheep manure (23 t/ha), chemical fertilizer including zinc sulfate (10?kg/ha), copper sulfate (10?kg/ha), iron sulfate (30?kg/ha), manganese sulfate (15?kg/ha) and no fertilizer (control) were conducted in a randomized complete block design with three replications at Research Farm of Shahrekord University in 2013. The results showed that micronutrients’ content in the root, α-amino-N sucrose percentage and sucrose yield were significantly affected by fertilizer treatments. The highest elements’ content of Fe (90.39?mg/kg), Zn (39.15?mg/kg), and Cu (18.1?mg/kg) in sugar beet root belonged to SMC treatment. Besides, SMC caused less α-amino-N accumulation in sugar beet compared with sheep manure (1.05 MEq/g). Sucrose percentage was higher in SMC treatment than the sheep manure. Likewise, sucrose percentage revealed a significant positive correlation with micronutrients of zinc, copper, and manganese in sugar beet root. Therefore, it could be concluded that using SMC increases micronutrients’ content in the root and at the same time, plays an important role in sugar quality improvement of sugar beet.  相似文献   
75.
Two pea (Pisum sativum L.) cultivars were compared: cv Lincoln and cv Douce de Provence. Seedlings grown for 14 d on standard medium were challenged for 21 d with salt using a split-root system. This protocol allowed salt-treated plants to absorb nutrients through a part of their root system maintained in control medium (C), the other part of the root system being placed in medium added with 75 mM NaCl (S). Full salt treatment (S/S) resulted in severe but non-lethal growth inhibition, high concentration of Na+ and Cl in leaves, and decrease in leaf K+ and chlorophyll contents. The two latter effects were more pronounced in Lincoln than in D. Provence. Growth inhibition was partially (Lincoln) or totally (D. Provence) alleviated in S/C configuration, and K+ content was less diminished than in full salt treatment. S/C treatment mitigated Na+ and Cl accumulation in Lincoln, but not in D. Provence. Thus, in the latter cultivar, growth inhibition by salt in S/S condition likely did not result from excessive Na+ and Cl accumulation in leaves. Increased electrolyte leakage from leaf tissues evidenced damages to leaf cell plasma membrane of both cultivars in S/S condition. However, damages to chloroplasts, as inferred from chlorophyll loss, were much pronounced in Lincoln than in D. Provence. Antioxidant enzymic activities in leaves were measured as proxies for oxidative stress. Catalase activity was stimulated by S/S treatment in both cultivars, but superoxide dismutase (Fe and Cu/Zn isoforms) and gaiacol peroxidase activities were augmented only in Lincoln. The absence of superoxide dismutase activity stimulation by salt in D. Provence could signify either that constitutive activity was sufficient to ensure protection against oxidative stress, or that intrinsic salt tolerance of this cultivar mitigated cellular oxidative stress. Thus, intraspecific variability for salt response exists between pea cultivars presenting similar growth sensitivity to salt.  相似文献   
76.
Drought is a problem of the expanding universe which seriously influences crop production and quality. Approximately one-third of the cultivated area of the world suffers from constantly inadequate supplies of water. The present study aimed to determine the effects of drought and rewatering on activities of antioxidant enzymes, chlorophyll, proline, and relative water contents (RWC). In this experiment, six maize hybrids (Sc260, Sc370, Sc500, Sc647, Sc700, and Sc704) were examined in a pot study during the maize-growing season of 2011. Results indicated that the growth of hybrids was retarded under drought stress conditions and regained growth speed during rewatering. RWC, chlorophyll, and carotenoid contents were markedly decreased by the water deficit and reached normal values during rewatering in Sc647, Sc704, and Sc700. Our findings also indicated significantly higher activity levels of peroxidase and catalase and proline content in water-stressed plants than in well-watered plants, which decreased when the plants were rewatered, showing an inverse relationship to gluthatione reductase activity. According to the results, the better upregulation of the protective mechanism in Sc704 and Sc647 probably induced higher drought resistance. We concluded that antioxidant enzyme activity could provide a useful tool for depicting drought tolerance in maize hybrids in arid and semiarid regions.  相似文献   
77.
Poor survival of winter cereals due to winter conditions in Ontario can necessitate destruction of the stand in the spring to allow the subsequent seeding of an alternative crop. Winter cereals were seeded in the autumn of 2004 and 2005 at the Huron Research Station and at the University of Guelph Ridgetown Campus in Ontario to evaluate two formulations of glyphosate [potassium (K) vs diammonium (DA) salt] at different doses (225, 450, 675, 900, or 1350 g a.e. ha−1) for the burn-off of soft white winter wheat (SWW), soft red winter wheat (SRW), hard red winter wheat (HRW) and autumn rye (AR) in either late April or early May. There was no difference between the glyphosate formulations for the control of winter cereals at 1, 2, 3, and 4 weeks after treatment (WAT). There was generally improved control with glyphosate applications made in early May compared to late April however results were not always statistically significant. Generally, control of winter cereals increased as the glyphosate dose was increased from 225 to 1350 g a.e. ha−1. The minimum dose of glyphosate required for providing 90% or greater control of SWW, SRW, HRW, and AR was 675 g a.e. ha−1 at 4 WAT. Glyphosate applied at 675 g a.e. ha−1 caused a 98, 97, 98, and 99% reduction in shoot dry weight of SWW, SRW, HRW, and AR, respectively. Based on this study glyphosate (K or DA) applied in late April or early May can be used at doses as low as 675 g a.e. ha−1 to adequately control SWW, SRW, HRW, and AR in the spring.  相似文献   
78.
The purpose of this research was to evaluate the combining ability of six local Iranian and one imported cantaloupe cultivar. Heritability of traits was estimated using a half‐diallel mating design. Seven parents and their crosses were evaluated in 2013 and 2014. The greatest general combining ability (GCA) for yield and fruit number was for “Rish‐baba” (0.53 kg/plant and 0.3, respectively). The cultivar “Ananasi” had the highest GCA for fruit weight and soluble solids content (SSC) (0.088 kg and 1.4, respectively). “Ananasi” presented the highest GCA values for fruit firmness, chlorophyll a and b and carotenoid content, as well as the highest total chlorophyll content. The cross Garmak × Rish‐baba showed the highest specific combining ability (SCA) for yield with heterosis value of 99%. High heritability estimates for SSC (0.52), flesh thickness (0.61) and concentration of chlorophyll a (0.7) were obtained. Although there were significant SCAs for yield, the parents are suggested to be improved prior to hybrid development. The parent “Ananasi” appears to be a suitable donor in breeding programmes.  相似文献   
79.
Replacement of olive pomace (OP) with wheat flour in diet was studied in diet of yearling Siberian sturgeon (Acipenser baerii). Fish (165 ± 6.8 g) were randomly allocated to 15 fibreglass tanks (15 fish/tank, in triplicate). Fish were assigned to one of five dietary treatments at 19.1 ± 1.5°C for 8 weeks: control diet (crude protein and crude lipid at 514.6 and 188 g/kg, respectively) and four experimental diets with 20, 50, 75 and 100 g/kg OP to replace wheat flour in the experimental diets. No significant difference was observed in the final weight, feed conversion ratio, specific growth rate, hepatosomatic index, viscera‐somatic index and survival rate among the treatments (p > 0.05). No change was seen in digestibility of protein and lipid in diets containing 20 g/kg and 50 g/kg OP compared to control group, while these values decreased with increasing in OP above 50 g/kg. Digestibility of dry matter and gross energy among the treatments demonstrated no significant difference (p > 0.05). Polyunsaturated fatty acids, especially C22:6n3 (DHA), in the muscle of the fish fed 75 g/kg and 100 g/kg OP in diets were significantly higher than control group (p < 0.05). These data show that OP could be recommended as a substitute for wheat flour in diet of S. sturgeon but its utilization for other species warranted future works.  相似文献   
80.
Background:Pertussis is a current contagious bacterial disease caused by Bp. Given the prevalence of pertussis, development of new vaccines is important. This study was attempted to evaluate the expression of main virulence factors (PTX, PRN, and FHA) from Bp predominant strains and also compare the expression of these factors in the OMVs obtained from predominant circulating Bp isolate. Methods:The physicochemical features of the prepared OMVs were analyzed by electron microscopy and SDS-PAGE. The presence of the mentioned virulence factors was confirmed by Western blotting. BALB/c mice (n = 21) immunized with characterized OMVs were challenged intranasally with sublethal doses of Bp, to examine their protective capacity. Results:Electron microscopic examination of the OMVs indicated vesicles within the range of 40 to 200 nm. SDS-PAGE and Western blotting demonstrated the expression of all three main protective immunogens (PTX, PRN, and FHA), prevalent in the predominant, challenge, and vaccine strains, and OMVs of the predominant IR37 strain and BP134 vaccine strain. Significant differences were observed in lung bacterial counts between the immunized mice with OMV (30 CFU/lung) compared to the negative control group ((6 104 CFU/lung; p < 0.001). In mice immunized with OMVs (3 µg), the number of lungs recovered colonies after five days dropped at least five orders of magnitude compared to the control group. Conclusion:OMVs obtained from circulating isolates with the predominant profile may constitute a highly promising vaccine quality. They also can be proposed as a potential basic material for the development of new pertussis vaccine candidate. Key Words: Bordetella pertussis, Vaccines, Virulence factors  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