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   162篇
  免费   6篇
林业   15篇
农学   18篇
基础科学   3篇
  24篇
综合类   11篇
农作物   15篇
水产渔业   12篇
畜牧兽医   58篇
园艺   2篇
植物保护   10篇
  2023年   1篇
  2022年   1篇
  2021年   3篇
  2020年   8篇
  2019年   2篇
  2018年   5篇
  2017年   7篇
  2016年   5篇
  2015年   4篇
  2014年   4篇
  2013年   12篇
  2012年   14篇
  2011年   11篇
  2010年   4篇
  2009年   6篇
  2008年   7篇
  2007年   6篇
  2006年   6篇
  2005年   8篇
  2003年   6篇
  2002年   2篇
  2001年   3篇
  2000年   3篇
  1999年   1篇
  1998年   2篇
  1995年   1篇
  1994年   1篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   7篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
  1979年   2篇
  1971年   1篇
  1970年   2篇
  1969年   1篇
  1968年   1篇
  1967年   3篇
  1966年   2篇
  1965年   3篇
排序方式: 共有168条查询结果,搜索用时 156 毫秒
61.
An experiment was conducted to determine the performance, antioxidation activity, and bone mineral content in Vanaraja chickens fed diet supplemented with organic trace minerals (oTM) at reduced levels. A total of 360 day-old chicks were selected and distributed randomly into 60 battery brooder pens. A maize–soybean meal-based control diet was supplemented with inorganic trace minerals (iTM), i.e., Mn, Zn, Fe, and Cu at 50, 45, 40, and 7.5 mg/kg, respectively, and varying concentration of oTM, i.e., Zn, Mn, Cu, Fe, I, Se, and Cr at 45, 50, 7.5, 40, 2, 0.30, and 0.25 mg/kg (diet II); 33.75, 37.50, 5.63, 30.0, 1.50, 0.23, and 0.19 mg/kg (diet III); 22.5, 25.0, 3.75, 20.0, 1.0, 0.15, and 0.13 mg/kg (diet IV); 18.0, 20.0, 3.0, 16.0, 0.80, 0.12, and 0.10 mg/kg (diet V); and 13.5, 15.0, 2.25, 12.0, 0.60, 0.09, and 0.08 mg/kg (diet VI), respectively. Each diet was allotted randomly to ten replicates and fed ad libitum from 1 to 42 days of age. The body weight at 14, 28, and 42 days was not affected by reducing the supplementation of oTM concentration in the diets. Similarly, feed intake at 14 days of age was not affected but reduced significantly (P?<?0.05) in the group fed diet IV (50 % oTM) compared to that in the other groups. The higher feed conversion ratio and increased concentration of Ca, P, and trace minerals in tibia were evident in the group fed oTM-supplemented diets compared to the diet containing iTM. Activities of glutathione peroxidase and ferric reducing ability in plasma did not differ in the groups fed on lower concentration of oTM compared to those fed on diet I (control diet). Therefore, it is concluded that the dietary supplementation of trace minerals can be reduced greatly when supplemented as organic form without affecting growth and antioxidant status in Vanaraja chickens.  相似文献   
62.
Ullucus tuberosus (common name ‘ulluco’) is a popular tuber crop of Andean highlands. Until now attention has been focused on ulluco from Bolivia, Peru and Ecuador, but little is known about its diversity in Colombia. Thirty-six accessions of cultivated ulluco preserved in the Gene Bank of the Universidad Nacional de Colombia were studied to assess the genetic diversity and spatial genetic structure of Colombian ulluco. We used morphological characters, molecular markers (total proteins, isozymes and RAPDs) and ploidy level. High morphological variability, especially for tuber shape and colour characters, was found. Eight accessions from north-east Colombian Andes showed some typical character-states of wild ulluco, suggesting that they could be partially domesticated forms. Genetic analysis using RAPD markers indicated that these accessions were very similar to other cultivated ullucos belonging to the same region. The regional structure observed in isozyme and RAPD dendrograms was confirmed by AMOVA results (52.6% among-region variation) and the spatial correlogram, showing the presence of two gene pools of ulluco in Colombia. Our results and the accumulated data suggest that ulluco was introduced to Colombia at least two times. Initially, semi-domesticated forms would have come from the central Andes to north-east Colombian Andes, where the native inhabitants would have completed the domestication process. Again, fully domesticated ullucos might have been introduced to south-west Colombian Andes.  相似文献   
63.
Interleukin‐10 (IL‐10) is a multifunctional cytokine and plays an important role in diseases. In this study, IL‐10 gene was cloned and characterized from catla (Catla catla), which is a highly commercially important fish species in the Indian subcontinent. The result indicated that the full‐length catla IL‐10 (cIL‐10) gene had five exons and four introns with an open reading frame of 540 nucleotides encoding a polypeptide of 179 amino acids. A phylogenetic analysis of cIL‐10 gene sequence showed that cIL‐10 clustered with freshwater carps group as expected. Quantitative real‐time polymerase chain reaction analysis showed that cIL‐10 was expressed in gill, liver, kidney, intestine, skin and heart and its expression profile was up‐regulated in bacterial infection and LPS treatment. A close relationship of high cIL‐10 expression and low pro‐inflammatory cytokine IL‐1β expression was observed in the treated group of fish, which might reveal the role of cIL‐10 as an anti‐inflammatory cytokine. Mechanism of cIL‐10 induction was investigated by blocking nuclear factor (NF)‐κB ‐signalling with BAY 11‐7082 in catla kidney cell culture. Blocking NF‐κB suppressed IL‐10 induction by LPS, and thus it revealed that cIL‐10 was induced through NF‐κB signalling. These data could be helpful to understand the function of IL‐10 in fish in response to vaccinations, probiotics and various diseases.  相似文献   
64.
Pandanus tectorius Parkinson ( P. fascicularis Lam.) of the family Pandanaceae constitutes one of the major bioresources of Ganjam coast, Orissa; used mainly in small scale perfume industry for aromatic compound extracted from the male inflorescences. In order to establish genetic diversity, if any related to perfume yield, samples of P. tectorius representing male populations from seven locations representing populations I–VII along the coastline of Orissa, India, were analysed for somatic chromosome number, 4C genomic DNA content, randomly amplified polymorphic DNA (RAPD) as well as phytochemicals. The somatic chromosome number in all the populations I–VII was 2n = 60. The chromosomes were of minute size without showing any remarkable structural variation. Like wise the average 4C DNA content was 5.09 pg (≅4,912 Mbp) that showed no intra- or inter-population differences. Out of 54 decamer primers tested, a total of 1,260 amplicons were obtained from 34 primers accounting 43.49% polymorphism. Molecular phylogenetic analysis of the seven populations revealed two distinct branches, with populations II and III in one and the rest populations in the other branch of the phylogenetic tree. It was important to note that the unique populations II and III confined to the Ganjam coast of Orissa having RAPD markers: OPA 09–940 bp, OPA 09–705 bp, OPC 14–1,500 bp, OPC 14–700 bp, OPC 20–1,475 bp, OPC 20–1,350 bp, OPC 20–920 bp and OPC 20–700 bp, were distinguished form the rest of the populations. The aforesaid populations (II and III) are well known to produce aroma of high quality and yield, composed of primarily phenyl ethyl methyl ether (66.8–83%) and terpinen-4-ol (5–12%) along with a number of other phyto-chemical compounds that support the flourishing perfume industry and livelihood of the local people in the region. The findings underscored the possible role of local eco-geography in contributing to the micro-evolution of unique high perfume yielding genotypes of P. tectorius that represented populations II and III at Ganjam coast, which were genetically distinct from the rest of the populations revealed by RAPD analysis.  相似文献   
65.
66.
67.
Sorghum shoot fly (Atherigona soccata) is a serious pest that destabilizes the performance of sorghum cultivars and ultimately reduces sorghum production in many parts of the world. Identifying sorghum genotypes with stable resistance to shoot fly is important as it helps to reduce the cost of cultivation and stabilizes yields. In the present study, our objective was to identify stable shoot fly resistant genotypes among 385 recombinant inbred lines (RILs) of a cross between a susceptible parent and a resistant parent. We evaluated this set of RILs in eight environments over three years (2006-2008) for shoot fly resistance and component traits. Non-significant genotype-environment (G × E) linear component and significant pooled deviation for deadheart percentage indicated that the performance of genotypes was unpredictable over the environments. However, five lines had deadheart percentages much less than the population mean with regression coefficient (bi) values close to unity, and non-significant deviation from regression, indicating that they have stable shoot fly resistance and are well adapted to all the environments. Additive main effect and multiplicative interaction (AMMI) analysis partitioned main effects into genotype, environment and G × E interacts with all the components showing highly significant effects (p < 0.001). Environment had the greatest effect (69.2%) followed by G × E interactions (24.6%) and genotype (6.2%). Low heritability and high environmental influence for deadheart percentage suggested that shoot fly resistance is a highly complex character, emphasizing the need for marker assisted selection. We observed transgressive variation in the RIL population for all the traits indicating the contribution of alleles for resistance from both resistant and susceptible parents. Since the alleles for shoot fly resistance are contributed by both resistant and susceptible parents, efforts should be made to capture favourable alleles from resistant and susceptible genotypes.  相似文献   
68.
Increasing crop productivity is one of the prime goals of crop breeding research. Rice grain yield is a complex quantitative trait governed by polygenes. Although several QTLs governing grain yield traits have been reported and limited attempts have been made to map QTLs for grain yield parameters in Basmati rice. A population from the cross Sonasal and Pusa Basmati 1121 comprising 352 RILs was generated through the single seed descent method. A total of 12 QTLs governing yield and yield-related traits were mapped on six chromosomes, namely, 1, 2, 3, 7, 8 and 9, of which five QTLs were novel. We identified a novel and robust epistatic QTL (qPH1.1 and qPL1.1) governing plant height and panicle length, flanked by the markers RM5336-RM1 on chromosome 1. The gene encoding brassinosteroid insensitive 1-associated receptor kinase 1 precursor is the putative candidate gene underlying this epistatic QTL. Another novel QTL, qNT3.1, governing tiller number was bracketed to a region of .77 Mb between the markers RM15247 and RM15281 on chromosome 3. Of the 57 annotated gene models, Os03g0437600 encoding alpha/beta-fold hydrolase, a homologous to AtKai2 is a putative candidate gene underlying the novel QTL qNT3.1. The other QTLs such as qDFF1.1 governing days to 50% flowering co-localizes with the gene Ghd7, QTL for plant height qPH1.2 co-localizes with the gene sd1, the QTLs for panicle length co-localizes with FUWA and DEP2, the QTL for tiller number co-localizes with OsRLCK57 and QTLs for thousand-grain weight co-localize with the major gene GS3. The QTLs identified in the current study can be effectively used in marker-assisted selection for developing Basmati rice varieties with a higher yield.  相似文献   
69.
ABSTRACT We investigated developmental changes in the primary mycelium of Crinipellis perniciosa upon its interaction with immature and mature leaves of Theobroma cacao. On nutritive medium, the primary mycelium grew significantly slower in the presence of host tissue than without host tissue. In the absence of the cacao leaves, incomplete phase transition occurred after 5 days, wherein older hyphae progressed to the dikaryotic state and growing tips remained monokaryotic. Phase transition occurred between 3 and 5 days on mature leaves, 10 and 12 days on meristematic leaves, and required 2 weeks on T. cacao callus tissue. The biotrophic mycelia were able to invade immature and mature cacao leaves without open wounds or stomata. Club-shaped hyphal tips and the formation of adhesive structures were induced by cuticle extracts and suggest host recognition. The initial cuticular disintegration at the site of penetration was followed by blister formation and complete digestion of leaves by the primary mycelium. The data suggest specific interactions between host and pathogen that control the onset of the necrotrophic phase of the fungus. The data further indicate that primary mycelium rather than spores can be used to study C. perniciosa pathogenicity.  相似文献   
70.
CD8+ cytotoxic T lymphocytes (CTLs) play a critical role in the defense against viral infections. In general, CD8+ CTLs recognize antigenic peptides in the context of the major histocompatibility complex (MHC) class I molecule. The MHC class I molecules are expressed on almost all the nucleated cells in the body. The trimolecular complex consisting of the class I heavy chain, beta2-microglobulin and the peptide are generated by the MHC class I antigen presentation pathway. This pathway is designed to sample the intracellular milieu and present the information to the CTLs trafficking the area. This rigorous sampling of intracellular environment enables the CTLs to quickly identify and eliminate the cells that synthesize non-self proteins as a result of a viral infection. Many viruses, including several viruses of veterinary importance, have evolved astounding strategies to interfere with the MHC class I antigen presentation pathway, as a means of evading the CTL response of the host. This review focuses on the diverse mechanisms of viral evasion of the MHC class I antigen presentation pathway with particular emphasis on viruses of veterinary importance.  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