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   344篇
  免费   25篇
林业   12篇
农学   13篇
基础科学   7篇
  100篇
综合类   7篇
农作物   78篇
水产渔业   57篇
畜牧兽医   53篇
园艺   8篇
植物保护   34篇
  2023年   4篇
  2022年   13篇
  2021年   11篇
  2020年   14篇
  2019年   24篇
  2018年   26篇
  2017年   46篇
  2016年   36篇
  2015年   15篇
  2014年   20篇
  2013年   36篇
  2012年   21篇
  2011年   35篇
  2010年   21篇
  2009年   2篇
  2008年   18篇
  2007年   11篇
  2006年   10篇
  2005年   2篇
  2004年   3篇
  1995年   1篇
排序方式: 共有369条查询结果,搜索用时 15 毫秒
111.

Background

The aim of this study was to understand any association between differentiated thyroid carcinoma (DTC) and Ile3434Thr XRCC7 gene polymorphism (GenBank accession number: rs7830743). DTC is the most prevalent thyroid neoplasm, which includes papillary and follicular cell carcinoma. XRCC7 gene encodes a protein that functions in non-homologous end joining DNA repair pathway. Non-synonymous polymorphisms in this gene may alter DNA repair capacity of the cell and change the risk of developing cancers.

Methods

DTC patients (n = 173) and cancer free individuals (n = 204) were enrolled in a case-control study. The Ile3434Thr polymorphic alleles were discriminated by using amplification refractory mutation system-PCR method. The frequencies of this single nucleotide polymorphism in case and control groups were compared. Also, risk ratio for developing DTC in dichotomized genotypes was estimated by multivariate logistic regression analysis.

Results

Dichotomized genotypes into those with and without the 3434Thr allele showed that this allele was associated with DTC (OR [odd ratio]: 1.89, 95% confidence interval (CI) = 1.29-2.79, P<0.001). Also, TC genotype was significantly associated with increased risk of DTC (OR: 2.42, 95% CI = 1.55-3.81, P = 0.0001) in individuals carrying this genotype.

Conclusion

Allele 3434Thr in XRCC7 gene might be associated with differentiated thyroid cancer risk. Further studies with larger samples are needed to verify these initial findings. Key Words: DNA repair enzymes, Thyroid neoplasms, Genetic polymorphism  相似文献   
112.
This study investigated the effects of foliar application of normal and nano-sized zinc oxide on the response of sunflower cultivars to salinity. Treatments included five cultivars (‘Alstar’, ‘Olsion’, ‘Yourflor’, ‘Hysun36’ and ‘Hysun33’), two salinity levels [0 and 100 mM sodium chloride (NaCl)], and three levels of fertilizer application. Fertilizer treatments were the foliar application of normal and nano-sized zinc oxide (ZnO). Foliar application of ZnO in either forms increased leaf area, shoot dry weight, net carbon dioxide (CO2) assimilation rate (A), sub-stomatal CO2 concentration (Ci), chlorophyll content, Fv/Fm, and Zn content and decreased Na content in leaves. The extent of increase in chlorophyll content, Fv/Fm and shoot weight was greater as nano-sized ZnO was applied to the normal form. The results show that the nano-sized particles of ZnO compared to normal form has greater effect on biomass production of sunflower plants.  相似文献   
113.
The effect of soil applied zinc (Zn) sulfate and seed priming with Zn-glutamine [Zn(Gln)2], Zn-glycine [Zn(Gly)2], Zn-arginine [Zn(Arg)2], and Zn-histidine [Zn(His)2] on yield and grain nutritional quality of two bread (Triticum aestivum L. cvs. Back Cross and Kavir) and a durum wheat genotype (Triticum durum L. cv. Durum) was investigated. Seed priming with [Zn(Gly)2] and [Zn(Gln)2] increased grain yield of wheat over soil applied Zn-sulfate treatment by 46 and 14%, respectively. Seed priming with [Zn(Gln)2], [Zn(Arg)2], and [Zn(His)2] significantly increased grain protein content of wheat in comparison with control treatment. Seed priming with [Zn(Arg)2] and [Zn(His)2] resulted in higher Zn and Fe accumulation in wheat grain as compared with the other Zn treatments. Priming seeds with [Zn(Arg)2] reduced phytic acid to Zn molar ratio of wheat grain. Seed priming with [Zn(Arg)2] and [Zn(His)2] might be used as an alternative approach for soil application of Zn-sulfate to overcome Zn deficiency in calcareous soils.  相似文献   
114.
Soil salinity and arbuscular mycorrhizal fungi (AMF) influence the soil hydrophobicity. An experiment was performed to determine the effects of soil salinity and AMF species on soil water repellency (SWR) under wheat (Triticum aestivum L.) crop. Six AMF treatments, including four exotic species (Rhizophagus irregularis, Funneliformis mosseae and Claroideoglomus claroideum, a mix of three species), one mix native AMF species treatment and an AMF-free soil in combination with four salinity levels (1, 5, 10, and 15 dS m?1) were used. The soil repellency index (RI) increased with salinity increment ranging from 2.4 to 10.5. The mix of three exotic and native AMF treatments enhanced the RI significantly compared to AMF-free soil in all salinity levels with one exception for native treatment at 1 dS m?1. Among individual AMF species, the C. claroideum treatment at 10 dS m?1 increased the RI by 67% compared to AMF-free soil. The native AMF treatment was more efficient in root colonization, glomalin production and SWR development at 10 and 15 dS m?1, compared to exotic species. In addition to the net positive effect of salinity on SWR, the AMF influences on the RI were greatly dependent on salinity levels.  相似文献   
115.
Due to the variations in opacity and brightness of peroxide bleached pulp at Mazandaran Wood and Paper Industries Company (MWPI), empirical models were developed to predict chemimechanical pulp (CMP) brightness and opacity from peroxide bleaching conditions and to drive the optimum operating conditions. To overcome the inconsistency problem, a multi-variate regression analysis method was used for model building. The models were then validated using a new data set from the bleach plant at MWPI, assessing the models’ predictive ability and performance. The results show that there is a relationship between bleaching variables and such dependent variables as pulp brightness and opacity. In addition to the hydrogen peroxide charge and pulp initial brightness, the initial opacity had a significant reverse effect on the final CMP brightness. It was also found that the concentration of total Na+ in the CMP tower was the most important variable affecting the final pulp opacity. The validation results demonstrated that these models can be employed as useful tools for process optimization purposes.  相似文献   
116.
In the present study, 100 bacterial strains were isolated from the soil and tested for siderophore producing ability. Among siderophore producing bacteria, three superior isolates with the highest level of siderophore (F13, F58 and F66) selected for further study. Production of lecithinase, arginine dehydrolase, catalase, oxidase, hydrogen cyanide, indole acetic acid, solubilization of phosphate, gelatin hydrolysis, oxidative/fermentative, motility and gram staining by these strains was evaluated. In greenhouse experiment, the ability of selected isolates in solubilizing insoluble iron-containing compounds was examined at three moisture levels (0.45–0.6, 0.6–0.7 and 0.7–0.85 field capacity). Results showed that isolates F13 and F66 have greatest effects on chlorophyll amount and shoot dry weight compared to isolate F58. On average, iron concentration of sunflower in the presence of bacteria was 2.85-fold more than control, while it was 1.88-fold for roots. In addition, bacterial treatments enhanced resistance to water stress in sunflower. Based on biochemical tests and by comparison of 16S rRNA sequences, the F13, F58 and F66 isolates were closely related to Pseudomonas spp., Enterobacter spp. and Bacillus Sporothernodurans, respectively.  相似文献   
117.
Blackleg disease, caused by the hemibiotrophic fungal pathogen Leptosphaeria maculans, is one of the most devastating disease of Brassica species worldwide. To date, a total of 20 race-specific blackleg resistance (R) genes have been reported and all of those loci are located in either the A or B genomes of various Brassica species. The B. oleracea genome (CC) shares a high ancestral synteny with the A genome of B. rapa, suggesting the presence of qualitative (race specific) resistance to blackleg disease is also possible in B. oleracea germplasm. In the present study the C genome of Korean B. oleracea germplasm was screened for the presence of blackleg R genes. Thirty-two inbred cabbage lines with unknown resistance profiles, along with five control B. napus lines with well-characterised race-specific R genes, were assessed for cotyledon resistance against two L. maculans isolates with known and highly-contrasting avirulence gene (Avr) profiles. Two cabbage accessions were identified which produced a strong resistance when challenged with either isolate, demonstrating the presence of effective blackleg R genes in the cabbage C genome. Additionally, 16 microsatellite markers linked to seven different R genes of the B. napus A genome were converted into markers for their homologous regions on the B. oleracea C genome. These markers were used to screen all B. oleracea lines to assess if the novel C genome R genes were syntenous to known R gene-homologous regions of the A genome. The resistant cabbage lines offer C genome R genes for the protection of B. oleracea varieties against incursion of blackleg disease, as well as novel additional resistance sources for introgression into B. napus and B. carinata breeding material.  相似文献   
118.
Nutrient deficiency may be a reason for citrus decline in many countries. In the current investigation, soil and leaf samples of 63 Washington Navel orange orchards in arid lands of southern Iran (Darab region) were analyzed to study the nutritional status of orange orchards and to find relationships between soil properties and nutrients content of soils and orange leaves. The soils differed widely in clay content (3–37%), pH value (7.04–7.95), calcium carbonate equivalent (18–86%), and organic matter content (0.3–12%). These soils represented a wide range of plant nutrients concentration. Majority of the studied soils had sufficient concentrations of all nutrients (except Fe). Results indicated that pH, organic matter, clay, and calcium carbonate contents are the most important characteristics that control the soil nutrients availability. The mean contents of N, K, P, Fe, Mn, Zn, and Cu in leaves were 2.59, 0.84, and 0.14% and 66, 44, 17, and 12?mg?kg?1, respectively. Most orchards showed K, Fe, and Zn deficiencies. We found no relationships between nutrients content in leaf and soil (except for K, Mn, and Zn); and this indicated that soil analysis may not be a reliable method for most nutrient deficiency diagnosis.  相似文献   
119.
The effects of adding surface modified graphene nanoplatelets (GNPs) in various weight percentages (0, 0.1, 0.2, 0.3, 0.4, 0.5 with respect to matrix) on the high velocity impact response of basalt fibers/epoxy composites were evaluated. High speed mechanical stirrer and ultrasonic waves were used for the dispersion of GNPs in the epoxy matrix, and hand layup method was utilized for the fabrication of the composite samples. High velocity impact testing was performed using a conical projectile. The results demonstrated that the maximum improvement in the impact limit velocity and energy absorption occurred in the 0.3 wt.% GNPs nanocomposite, i.e., 11 and 23 %, respectively. Also, the electron microscopy studies revealed that the addition of GNPs contributed in improving the impact properties by influencing the matrix and thus enhancing the interfacial characteristics between the basalt fibers and the matrix.  相似文献   
120.
The effect of cattle manure and sulfur fertilizer on seed yield and oil composition of pumpkin (Cucurbita pepo var. Styriaca) under inoculated with Thiobacillus thiooxidans was investigated in a factorial study based on a randomized complete block design. Experimental factors consisted of cattle manure (M) (M0: 0, M1: 10; and M2: 20 t ha?1), sulfur (S) (S0: 0, S1: 250; and S2: 500 kg ha?1) and T. thiooxidans (B): inoculated (B1) and non-inoculated (B0). Results demonstrated that the application of T. thiooxidans, cattle manure, and S fertilizer decreased the soil pH. The largest number of seed per fruit (367), highest fruit yield (70.57 t ha?1), seed iron (Fe) content (16.26 mg 100 g?1), and seed yield (111 kg ha?1) was obtained when 20 t ha?1 manure was applied in combination with 500 kg ha?1 S inoculated with T. thiooxidans. In this condition, the content of S, Fe, phosphorus (P), and nitrogen (N) in plant shoots was increased by 44.8%, 22.58%, 33.89%, and 10.38%, respectively, compared to the control. Moreover, the highest content of seed protein was observed in 10 t ha?1 manure and 500 kg ha?1 S fertilizer inoculated with T. thiooxidans. When 250 kg ha?1 S fertilizer was applied, 20 t ha?1 manure decreased seed P content sharply. At the rate of 500 kg ha?1 S fertilizer, the highest content of seed P was obtained from 20 t ha?1 manure. Totally, 20 t ha?1 cattle manure, along with 500 kg ha?1 S fertilizer as well as T. thiooxidans inoculation, improved oil and seed yield of medicinal pumpkin.  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