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   52篇
  免费   2篇
林业   4篇
农学   4篇
  7篇
综合类   5篇
农作物   4篇
畜牧兽医   16篇
园艺   1篇
植物保护   13篇
  2022年   1篇
  2021年   6篇
  2020年   2篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   4篇
  2014年   1篇
  2013年   4篇
  2012年   5篇
  2011年   3篇
  2009年   1篇
  2008年   3篇
  2007年   2篇
  2006年   7篇
  2005年   1篇
  2004年   1篇
  2003年   1篇
  2002年   4篇
  1999年   2篇
  1988年   1篇
排序方式: 共有54条查询结果,搜索用时 15 毫秒
41.
Lipopolysaccharides (LPS) are surface glycoconjugates embedded in the external leaflet of the outer membrane (OM) of the Gram-negative bacteria. They consist of three regions: lipid A, core oligosaccharide (OS), and O-specific polysaccharide or O-antigen. Lipid A is the glycolipid endotoxin domain that anchors the LPS molecule to the OM, and therefore, its chemical structure is crucial in the maintenance of membrane integrity in the Gram-negative bacteria. In this paper, we reported the characterization of the lipid A and OS structures from Pseudoalteromonas nigrifaciens Sq02-Rifr, which is a psychrotrophic Gram-negative bacterium isolated from the intestine of Seriola quinqueradiata. The immunomodulatory activity of both LPS and lipid A was also examined.  相似文献   
42.
Discussion of the role of non-timber forest products (NTFPs) in efforts to reconcile the objectives of forest conservation and rural development has often been hampered by limited understanding of the complexity of the factors that affect the contribution of NTFPs to local livelihoods. By drawing upon two case studies where NTFPs play an important role - the municipality of Lepaterique in Honduras and Palawan Island in the Philippines - this study emphasizes that an ideal extractive system should be based on a mix of products to enable sustainable harvesting throughout the year. The study also demonstrates that considerable attention needs to be paid to the socio-cultural heterogeneity of resource users, and to the value chain structure, access and control over resources and political transparency that affect the opportunities for local people to benefit from NTFP extraction.  相似文献   
43.
44.
Fusarium wilt of melon caused by Fusarium oxysporum f. sp. melonis is a destructive fungal disease in melon growing regions. Isolates of F. oxysporum obtained from six major melon producing provinces in Iran, from melons and other hosts, were characterized based on pathogenicity to melon, vegetative compatibility groups (VCGs) and nuclear ribosomal DNA intergenic spacer (IGS) sequencing. Thirty-four of 41 isolates from Iran in this study were identified as race 1,2 which belonged to either VCG 0134 or an unassigned VCG, which based on IGS sequencing grouped with the VCG 0135 tester isolate. The seven remaining isolates were identified as nonpathogenic to melon belonging to two undescribed VCGs. Based on sequence analyses of the IGS region of Iranian and foreign isolates, nine lineages were identified, each including one VCG. The separation of VCGs into distinct lineages based on IGS sequences is mostly consistent with Repetitive extragenic palindromic PCR (Rep-PCR) results. Exceptions are VCGs 0130 and 0131, which could be differentiated with IGS sequences, but not with Rep-PCR. Different races from the USA, France and Iran associated with VCG 0134 grouped into one IGS lineage but could be differentiated with Rep-PCR, suggesting that this VCG is more diverse than previously thought. Given the long history of melon cultivation in Iran and the Rep-PCR diversity of isolates belonging to this VCG, it could be speculated that VCG 0134 perhaps evolved in Iran.  相似文献   
45.
Rumen micro‐organisms are capable of producing microbial protein from ammonia and carbon skeleton, and non‐protein nitrogen (NPN) may be one of the sources of ammonia. Alternative source of NPN is the slow release of ammonia sources in which the product is the extrusion of starch with urea. This work aimed to determine the effects on nutrient intake, ingestive behaviour, digestibility, nitrogen balance, ruminal pH, rumen ammonia nitrogen, volatile fatty acids (VFA) and blood parameters with increased levels of extruded urea (50, 60, 70 and 80 g/100 kg of body weight [BW]) in beef cattle diet. Four rumen cannulated crossbred steers with initial mean weight of 336 ± 47 kg in a 4 × 4 Latin square design were distributed. Diets were formulated with 400:600 g/kg roughage:concentrate ratio on dry matter based and provided once per day, being used whole corn silage as roughage. There were no effects on nutrient intake (kg/day), ingestive behaviour, apparent digestibility, nitrogen balance, volatile fatty acid (VFA) and blood parameters in extruded urea treatment groups. Similar results were observed on time spent on feeding, rumination and idleness. There were positive linear effects (p = 0.022) on rumen pH in the time of 8 hr after feeding and also on plasma concentration of the extruded urea levels (p = 0.039); whereas a linear negative effect (p = 0.030) was observed on ammonia nitrogen for the collection time of 2 hr after feeding. Increased levels of extruded urea could maintain nutrient intake, digestibility, ingestive behaviour, rumen pH and blood parameters in normal conditions. In conclusion, we recommend the extruded urea use with values up to 80 g/100 kg BW in confined beef cattle that receive balanced diets with 140 g/kg of crude protein.  相似文献   
46.
At present, the sugarcane (Saccharum spp.) breeding programs from around the world have practiced early family selection, because in the early stages of breeding the evaluated characteristics have shown low heritability. This study aimed to select through restricted maximum likelihood/best linear unbiased prediction also known “mixed models” the best families among the 78 that comprise the RB05 sugarcane series, stage T1, of Programa de Melhoramento Genético da Cana-de-açúcar of the Rede Interuniversitária para o Desenvolvimento do Setor Sucroalcoleiro, Brazil. The experiments, conducted during 2007/2008 and 2008/2009 in Paranavaí, PR were implemented using an incomplete-block design with five replicates of each family. Each plot was composed of two planting rows of 5 m, spaced from each other by 1.40 m and spacing between plants was of 0.50 m, containing ten seedlings for planting row, resulting in a total of 20 individuals per replicate of each family. The characteristics evaluated were Brix (°Brix), ton of stalk per hectare (TCH) and ton of °Brix per hectare (TBH). The joint analysis obtained from these three traits in both harvests favored the selection of 35–41 families. The analysis also favored the selection of the best parents. The top five families for Brix were: F41M60, F02M77, F41M82, F61M38 and F62M35; to TCH were F66M30, F35M06, F78M45, F70M30 and F57M46 and for TBH the five elites families were F66M30, F35M06, F78M45, F70M30 and F01M39. The five best sugarcane parents for Brix were RB835486, SP91-1049, SP80-3280, RB72454 and RB925211; to TCH were IAC87-3396, RB941531, RB855511, RB915141 and RB957689, and for TBH the elite were IAC87-3396, RB855511, RB957689, RB941531 and RB855563. As each harvest season had different order of the best families, the joint analysis proved to be a primordial tool for plant breeders.  相似文献   
47.
Objective To evaluate the anti‐emetic properties of acepromazine in dogs receiving opioids as pre‐anesthetic medication. Study design Randomized prospective clinical study. Animals One hundred and sixteen dogs (ASA I or II), admitted for elective surgical procedures. The dogs were a mixed population of males and females, purebreds and mixed breeds, 0.25–13.4 years of age, weighing 1.8–57.7 kg. Methods A prospective clinical trial in which the dogs were randomly assigned to one of three groups. All groups received acepromazine (0.05 mg kg?1 intramuscularly (IM)). Group I received acepromazine 15 minutes prior to opioid administration. Group II received acepromazine in combination with the opioid. Group III received acepromazine 15 minutes after opioid administration. One of three different opioids was administered IM to each dog: morphine sulfate at 0.5 mg kg?1; hydromorphone hydrochloride at 0.1 mg kg?1; or oxymorphone hydrochloride at 0.075 mg kg?1. Results Dogs receiving acepromazine before the opioid (group I) had a significantly lower incidence of vomiting (18%) than dogs in groups II (45%) and III (55%). The degree of sedation was significantly lower in the dogs receiving the combination of acepromazine and the opioid (group II) than in dogs receiving the opioid as the first drug (group III). Conclusions and clinical relevance Acepromazine administered 15 minutes before the opioid lowers the incidence of vomiting induced by opioids.  相似文献   
48.
This study was conducted to understand variation patterns and establish the population structure in the wild rice species, Oryza officinalis, using accessions collected across the 11 regions/areas of endemism in Asia and Oceania and conserved ex situ in the International Rice Genebank at the International Rice Research Institute. Morphological and microsatellite data detected a tendency for latitudinal divergence in O. officinalis and divided the accessions into (1) Malesian and (2) South and East Asian populations. Cluster and ordination analyses of morphological characters revealed that accessions from Malesia (Regions 1–6), Vietnam (Region 7), and Central Thailand (Region 8) showed short (16.19 ± 3.70 cm) and slender (1.53 ± 2.06 cm) flag leaves that are erect to almost horizontal, short panicles (25.19 ± 3.02 cm) and mainly purple internodes; and (3) accessions from Northern Thailand and Myanmar (Region 9), India (Region 10) and China (Region 11) characterized by long (29.57 ± 4.94 cm) and broad (2.18 ± 3.33 cm) flag leaves that are horizontal to drooping, long panicles (35.26 ± 2.63 cm) and green internodes. With 79.3 % of the SSR markers being polymorphic, molecular analyses detected an average of 5.31 alleles per marker with a total of 154 alleles. Differentiation was evident among the regions with FST = 0.2173, although there is an apparent loss of heterozygosity across regions indicated by an over-all positive FIS. Based on the results, issues related to the management of O. officinalis, specifically filling gaps in the collection and the formulation of seed multiplication practices are addressed.  相似文献   
49.
Thermal analysis could rapidly and easily predict nutritional value of ruminant feeds. The hypothesis is that crambe meal (CM) has a quality similar to that of soybean meal (SM), and the objective of this study was to determine the nutritional characteristics of CM and compare them to those of SM. CM had greater concentrations of phytic acid (26.3 vs. 16.0 g/kg) and phenol compounds (615 vs. 393 mg gallic acid (GAE)/kg) than SM. In vitro dry matter (DM) digestibility was lower for CM than SM (752 vs. 975 g/kg DM). Cumulative in vitro gas production at 48 h of incubation (14.1 vs. 19.4 mL/100 mg substrate DM), and energy release (4.5 vs. 5.7 kJ/g substrate DM) were lower for CM than SM. CM had a higher concentration of low digestible fiber, hence degradability of DM was lower and the proportion of indigestible fraction was greater for CM than SM. High concentrations of indigestible compounds were likely responsible for lower gas production of CM compared to SM. These results suggest CM quality is lower than that of SM and that thermal analysis is a useful tool to precisely determine the nutritive value of oilseed residues.  相似文献   
50.
In the present work, we established and characterized a 3D functional polarized primary bovine oviduct epithelial cells (BOECs) culture on free-floating type I collagen hydrogels (rafts) at an air-liquid interface (ALI). Intercellular junctions, ultrastructural cellular morphology and the expression of the OVGP1 closely recapitulated those of the in vivo epithelium lining. These morphological and physiological epithelial cell features were maintained under standard DMEM/F12 with 10% foetal bovine serum culture medium for at least 28 days of ALI culture. The versatility of the BOECs raft cultures should allow testing of toxicity compounds, in vitro evaluation of physiological or pathological oviductal states, and the study of epithelial-mesenchymal interactions that are critical for the maintenance of oviductal homeostasis.  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