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   130篇
  免费   19篇
  国内免费   4篇
林业   6篇
农学   9篇
基础科学   1篇
  11篇
综合类   27篇
农作物   5篇
水产渔业   46篇
畜牧兽医   33篇
园艺   2篇
植物保护   13篇
  2024年   1篇
  2023年   2篇
  2021年   3篇
  2020年   8篇
  2019年   9篇
  2018年   4篇
  2017年   9篇
  2016年   7篇
  2015年   12篇
  2014年   6篇
  2013年   7篇
  2012年   7篇
  2011年   9篇
  2010年   9篇
  2009年   4篇
  2008年   10篇
  2007年   7篇
  2006年   5篇
  2005年   5篇
  2004年   3篇
  2003年   3篇
  2002年   4篇
  2001年   2篇
  2000年   5篇
  1999年   2篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1988年   2篇
  1987年   2篇
  1956年   1篇
排序方式: 共有153条查询结果,搜索用时 15 毫秒
81.
与渔业生产数据时空匹配的长时间序列三维实时海洋环境 数据的缺乏,一直是制约渔业海洋学深入研究的重要因素之一。本文基于数据同化的思想,采用梯度依赖最优插值方法,以黑潮-亲潮交汇区柔鱼渔场为例,利用 Argo观测数据,进行了渔获点上温盐垂直结构的反演 实验,在理论检验、与实测数据对比验证该方法有效性的基础上,初步探讨了渔场区的温盐特征及其与柔鱼渔获量的关系。结果表明,通过梯度依赖方法构建的温度均方根误差小于1℃,盐度小于0.4;与淞航号实测数据的温、盐绝对误差分别在0.25℃和0.27以内。2018年8月和10月的统计分析表明,柔鱼在5m深度的适宜温度分别为16℃和14℃,50m约为9~ 12℃ ,并且柔鱼趋于在低盐海域活动;各水层温度与渔获量均大致呈曲率不同的指数函数关系,且渔获点存在明显跃层,跃层强度变化越大,渔获量随机性也越大,渔获量跃层强度在0.4℃/m左右时渔获量相对稳定。这些结果进一步验证了该方法在构建环境垂直结构方面的可行性,其可为渔场环境的深入研究提供必要的技术手段。  相似文献   
82.
将PRRSV Hn-1/06株阳性血清(中和效价为1∶2)做2~8倍倍比稀释后,分别与等体积含100TCID50/100μL的PRRSV Hn-1/06株病毒液混合,制备感染性免疫复合物。取纯化的猪IgG和兔抗猪IgG制备非感染性免疫复合物。用鼠抗FcγRⅡB阳性血清封闭猪肺泡巨噬细胞(PAM细胞)表面的FcγRⅡB,然后分别将感染性免疫复合物和非感染性免疫复合物与PRRSV的混合物感染封闭后的PAM细胞,培养48h后收获样品,采用荧光定量RT-PCR检测收获样品中PRRSV的含量。结果表明,选择性封闭PAM细胞的FcγRⅡB能增强PRRSV的抗体依赖性增强作用。  相似文献   
83.
家蚕悬浮培养细胞系的建立及悬浮培养   总被引:7,自引:1,他引:7  
通过对家蚕细胞系BmN进行多轮选育 ,选拔出具有较好悬浮性能的细胞株 ,命名为BmN ZJ S ;并在自制转瓶系统中对其进行悬浮培养。实验表明 ,家蚕细胞BmN ZJ S在悬浮培养条件下的细胞扩增倍数为 2 9,最高细胞密度为 4 3 5× 1 0 5个 /mL(细胞活性大于 98%) ,对数生长期延长 2 4h,接近或优于贴壁培养条件下的相应值。  相似文献   
84.
通过电镜直接观察从吉林省、辽宁省部分地区收集到的猪无名高热综合征病料,发现主要为猪繁殖与呼吸综合征病毒、副粘病毒、猪瘟病毒;将从吉林省的无名高热综合征病料中分离到的副粘病毒、病料原液以及由病料制得的自家灭活疫苗分别接种到血清检测无名高热综合征主要病原抗体阴性的健康仔猪,同时设立阴性对照,对临床感染的仔猪进行了病理变化、病毒分离、细菌检测等方面的鉴定分析,对无名高热综合征病原的致病特点、发病规律和灭活疫苗使用中出现的抗体依赖性增强作用(ADE)进行了探讨研究。结果表明:初步认定两省部分地区无名高热综合征的主要病原体为PRRSV,由病料所制得灭活疫苗在活体中具有抗体依赖性增强现象。  相似文献   
85.
Bamaxiang pig is from Guangxi province in China, characterized by its small body size and two‐end black coat colour. It is an important indigenous breed for local pork market and excellent animal model for biomedical research. In this study, we performed genomewide association studies (GWAS) on 43 growth and carcass traits in 315 purebred Bamaxiang pigs based on a 1.4 million SNP array. We observed considerable phenotypic variability in the growth and carcass traits in the Bamaxiang pigs. The corresponding SNP based heritability varied greatly across the 43 traits and ranged from 9.0% to 88%. Through a conditional GWAS, we identified 53 significant associations for 35 traits at p value threshold of 10?6. Among which, 26 associations on chromosome 3, 7, 14 and X passed a genomewide significance threshold of 5 × 10?8. The most remarkable loci were at around 30.6 Mb on chromosome 7, which had growth stage‐dependent effects on body lengths and cannon circumferences and showed large effects on multiple carcass traits. We discussed HMGA1 NUDT3, EIF2AK1, TMEM132C and AFF2 that near the lead SNP of significant loci as plausible candidate genes for corresponding traits. We also showed that including phenotypic covariate in GWAS can help to reveal additional significant loci for the target traits. The results provide insight into the genetic architecture of growth and carcass traits in Bamaxiang pigs.  相似文献   
86.
枸杞多糖-4a改善糖尿病大鼠胰岛素抵抗作用的研究   总被引:1,自引:0,他引:1  
试验旨在研究枸杞多糖亚级分(LBP-4a)改善非胰岛素依赖型糖尿病(NIDDM)大鼠胰岛素抵抗(IR)的作用及其机制。试验采用水提醇沉法从宁夏枸杞中提取出枸杞多糖,并对其进行分离、纯化得主要活性成分LBP-4a。采用高糖高脂饮食结合小剂量腹腔注射链脲佐菌素(STZ)建立NIDDM大鼠模型,并将其分为模型对照组、LBP-4a低、高剂量组和罗格列酮治疗组,同时设立正常对照组。给药8周后检测相关指标。采用单细胞凝胶电泳技术对LBP-4a降糖、改善IR的作用机理进行了较为深入系统的探讨。结果表明,LBP-4a不仅对NIDDM大鼠具有降脂和增加抗氧化性的功能,还具有修复DNA损伤的作用。因此,LBP-4a作为一种可食的添加物能改善NIDDM大鼠的IR,进而预防NIDDM并发症及癌变的发生。  相似文献   
87.
For molecular biological detection of Mycobacterium avium subsp. paratuberculosis (MAP), PCR methods with primers targeting different regions specific for MAP are used worldwide. However, some uncertainties exist concerning the specificity of certain target regions and the sensitivity. To identify the methods which are best suited for diagnostics, 8 single-round and 5 nested PCR systems including 12 different primer pairs based on IS900 (9 x), ISMav2 (1x), f57 (1x), and locus 255 (1x) sequences were compared regarding their analytical sensitivity and specificity under similar PCR conditions. Reference strains and field isolates of 17 Mycobacterium species and subspecies, 16 different non-mycobacterial bovine pathogens and commensals were included in this study. Single-round PCR resulted in a detection limit of 100 fg to 1 pg, and nested PCR in 10 fg or below. Depending on the specific primer sequences targeting IS900, false positive results occurred with one of the five single-round and two of the four nested PCR systems. This also applied to the single-round PCR based on ISMav2 and the nested PCR based on f57. A high number of non-specific products were primarily detected for the single-round PCR assay based on ISMav2, but also for a single-round PCR targeting the IS900 and the locus 255. In conclusion, stringent selection of IS900-specific primers ensures that IS900 remains a favourite target sequence for amplification of MAP specific loci. The studied PCR systems based on f57, and locus 255 can also be recommended. Revision of ISMav2 primers is necessary. Single-round PCR systems are very reliable. Nested PCR assays were occasionally disturbed by contaminations, thus bearing a risk for routine diagnostics.  相似文献   
88.
We examined mortality patterns of two conifer species in relation to tree abundance and species composition in a declining spruce-fir forest in Akan National park, Hokkaido, northern Japan. The data taken from eleven 58 m × 58 m square study plots showed that percentage basal area (BA) of dead trees of canopy trees during the last decade was 49% forPicea jezoensis (Sieb. et Zucc.) Carr and 30% forAbies sachalinensis (Fr. Schm.) Masters. InP. jezoensis, percentage basal area (BA) of dead trees was positively related to both BA of its own species and proportion of it to BA of all species, whereas it was not significantly related to both of these variables inA. sachalinensis. Multiple logistic regression with dbh as a confounding factor also indicated that, inP. jezoensis, the proportion of dead stems was positively affected by the stem density of conspecific trees, whereas it was negatively affected by the stem density of the other species in each study plot. However, inA. sachalinensis, the proportion of dead stems was significantly related to neither of these factors. The different mortality pattern between two conifer species suggests that the spruce bark beetle,Ips typographus (L.), which is a serious pest of spruce, may have caused theP. jezoensis decline. Instead of wind-throw or thinning that usually initiate this bark beetle attack, some unknown factors seemed to predispose the trees to insect attack. These unknown factors may also explain the high mortality ofA. sachalinensis in this forest. This research was supported by FFPRI Project, Ministry of Agriculture, Forestry and Fishery.  相似文献   
89.
A preinoculative foliar application of 5 mM BABA significantly inhibited the colonization of Alternaria brassicae on leaves of Brassica carinata susceptible cultivar car6. BABA treatment led to transient but significant increase in H2O2 level during early stages of pathogen colonization. A significant increase in superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol dependent peroxidase (GDP) contributed to inhibition of the oxidative stress in BABA treated plants in response to pathogen infection. In conclusion BABA treatment led to proper balance of oxidant & antioxidants suitable for expression of resistance resulting in curtail of pathogen ingress during early stages of colonization.  相似文献   
90.
特用竹种——酒竹的引种繁育初报   总被引:2,自引:1,他引:2  
酒竹,以其可以伤流形式分泌出含酒精的天然营养液而闻名于世,但目前,世界上对酒竹研究、开发和利用尚处于初始阶段。本文对酒竹这一重要经济竹种的引种和初期的扦插、培育、密度限制等工作做了详细的报告,为收集种质和培育特种竹种提供了基础资料。  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