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   2290篇
  免费   89篇
  国内免费   386篇
林业   8篇
农学   35篇
基础科学   2篇
  19篇
综合类   582篇
农作物   4篇
水产渔业   180篇
畜牧兽医   1911篇
园艺   17篇
植物保护   7篇
  2024年   6篇
  2023年   20篇
  2022年   50篇
  2021年   70篇
  2020年   75篇
  2019年   90篇
  2018年   44篇
  2017年   55篇
  2016年   93篇
  2015年   88篇
  2014年   134篇
  2013年   103篇
  2012年   177篇
  2011年   192篇
  2010年   118篇
  2009年   141篇
  2008年   138篇
  2007年   203篇
  2006年   158篇
  2005年   132篇
  2004年   113篇
  2003年   80篇
  2002年   74篇
  2001年   76篇
  2000年   73篇
  1999年   37篇
  1998年   35篇
  1997年   39篇
  1996年   17篇
  1995年   27篇
  1994年   26篇
  1993年   14篇
  1992年   17篇
  1991年   11篇
  1990年   8篇
  1989年   10篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1983年   1篇
  1981年   1篇
  1979年   6篇
  1978年   1篇
  1976年   1篇
  1973年   1篇
  1956年   2篇
排序方式: 共有2765条查询结果,搜索用时 15 毫秒
961.
鹅新城疫新型疫苗研究进展   总被引:1,自引:0,他引:1  
结合新城疫病毒的保护性抗原,就近年鹅新城疫的DNA疫苗、基因工程亚单位疫苗、重组活载体疫苗、减毒活疫苗等新型疫苗的研究现状进行了综述,为鹅新城疫疫苗研制提供参考.  相似文献   
962.
为了用HPLC法同时测定复方防己口服液中粉防己碱和防己诺林碱的含量.采用Diamonsil C 18柱(5μm,4.6 mm×250 mm),以乙腈-0.2%磷酸水溶液-三乙胺(63∶37∶0.05)为流动相,流速为1.0 mL/min,检测波长282 nm的液相检测方法.结果表明,在此色谱条件下,粉防己碱和防己诺林碱的分离良好,分别在20.52 ~ 205.2μg/mL和17.84 ~ 178.4 μg/mL浓度范围内峰面积与浓度呈良好的线性关系.按外标法以峰面积计算进行测定,粉防已碱和防己诺林碱的平均回收率分别为98.15%和97.35%,RSD分别为1.39%和1.90%.表明该方法简便,快速,准确,适用于防已散中粉防己碱和防己诺林碱的含量测定.  相似文献   
963.
综述了近年来结核疫苗研发过程中宿主抗结核感染免疫机制的研究进展,介绍了结核疫苗研发策略及已进入临床前期的结核疫苗,同时列举了新的结核疫苗评价标准,以期为结核疫苗的进一步研究提供参考.  相似文献   
964.
新城疫病毒分子生物学研究进展   总被引:1,自引:0,他引:1  
新城疫(Newcastle Disease,ND)是由新城疫病毒(NDV)引起的一种急性、高度接触性禽类传染病,被世界动物卫生组织(OIE)定为法定必报传染病,我国也将其列为一类动物疫病,本文从新城疫病毒的形态及分子结构、致病力的分子基础、分子流行病学特征和基因工程疫苗等分子生物学相关研究进展进行了综述。  相似文献   
965.
猪传染性胃肠炎病毒(TGEV)可导致仔猪严重腹泻,死亡率极高,是危害养猪业的重要病毒。免疫接种是预防TGEV感染有效手段,TGEV疫苗开发对防治TGEV感染具有重要价值。制备纯净种毒是疫苗株基础。本试验通过细胞培养、病毒培养、间接免疫荧光、RT-PCR、理化试验、中和试验、纯净度检测等试验技术对TGEV自主致弱毒株HR/DN1进行系统特性,结果表明,该病毒理化特性和分子生物学特性均与TGEV相符,且该病毒具有繁殖滴度高、传代稳定、病毒纯净等特点,符合种毒制备基本条件,为开发TGEV疫苗提供基础。  相似文献   
966.
Abstract

AIMS: To modify and validate an existing swine erysipelas ELISA for use with poultry serum and to assess the safety of a swine erysipelas vaccine for use in New Zealand layer birds.

METHODS: An existing swine erysipelas ELISA was modified for use in domestic poultry and was validated using sera from birds injected with either 2 mL of a commercially available killed swine erysipelas vaccine (low-dose; n=12 birds), 4 mL of vaccine (high-dose; n=11 birds), or 2 mL saline (control; n=11 birds) on Day 0 and again on Day 21. Blood samples were collected on Days 0, 21, 42, and 63, and safety of the vaccine for use in layer birds was determined by assessing cloacal temperature and injection site reactions in birds at 0, 4, 24, 48, 72 and 96 h post-vaccination.

RESULTS: The ELISA that was developed had a diagnostic sensitivity and specificity of 93% and 98%, respectively, after being optimised for a positive cut-off at an optical density (OD) ≥1.50 read at 450-nm wavelength. OD readings were higher on Days 21, 42, and 63 than Day 0 in both the low-dose and high-dose groups (p<0.05), and differed amongst the three groups on Days 21, 42, and 63 (p<0.05), suggesting that vaccination using either dose induced detectable levels of antibody, even after a single dose. In addition, the high-dose protocol induced higher levels of antibody production than the low-dose protocol. No local or systemic reactions to the vaccine were observed and cloacal temperatures remained in the normal biological range after vaccination.

CONCLUSIONS: The ELISA that was developed had satisfactory diagnostic performance characteristics and the vaccine appeared to be safe for use in layer birds. However, the study design did not permit an assessment of the vaccine's efficacy to protect birds from clinical erysipelas.

CLINICAL RELEVANCE: A diagnostic ELISA has been developed for determining the exposure of layer birds to E. rhusiopathiae. The test will be useful for monitoring flock-level erysipelas, response to vaccination, and in epidemiological studies designed to identify risk factors for exposure to the disease.  相似文献   
967.
Chronic non-progressive pneumonia (CNP) is a common disease which affects lambs in New Zealand during late summer and autumn. Mycoplasma ovipneumoniae can be recovered from a high proportion of lesions but it is also present in some normal lungs. Bacteria, especially Pasteurella haemolytica, can also be recovered from more than half the lungs of affected animals.

Isolates of M. ovipneumoniae are genetically heterogeneous, as demonstrated by examination of their DNA or total cellular proteins, and are serologically heterogeneous as shown by metabolic inhibition tests. The number of strains present in New Zealand is large and several distinguishable strains can be recovered from each affected lung. Mycoplasma ovipneumoniae has pathogenic potential as indicated by its ability to produce hydrogen peroxide, cause ciliostasis and by its possession of a capsule.

Chronic non-progressive pneumonia can be transmitted consistently to over 50% of lambs by inoculation of pooled pneumonic lung homogenate and transmission can be suppressed by broad spectrum antibiotics. In contrast, penicillin does not prevent the development of lesions but diminishes their severity. Pooled lung homogenate treated with digitonin, which inactivates mycoplasmas, has failed to transmit CNP. Pure cultures of M. ovipneumoniae produce only mild lesions in some animals, whereas inoculation with pooled lung homogenate (from which no viruses were isolated) containing mixed strains of M. ovipneumoniae and free from bacteria, is more effective in producing lesions.

Research work to date suggests that CNP may be initiated by colonisation of the lung by M. ovipneumoniae which causes ciliostasis and elicits an exudate allowing colonisation of the lungs by bacteria especially P. haemolytica and by other strains of M. ovipneumoniae. The immune response to the initial strain of M. ovipneumoniae may inhibit its replication but would be less effective in inhibiting heterologous strains of the organism allowing their sequential replication. Eventually production of a broad immune response to M. ovipneumoniae would lead to its elimination which in turn would facilitate the elimination of other microorganisms and the resolution of lesions. As natural immunity to CNP occurs within the first year, it may be possible to develop an effective and useful vaccine. Such a vaccine may need to include multiple strains of M. ovipneumoniae.  相似文献   
968.
马俊  吴祖河  唐劲天 《安徽农业科学》2013,41(10):4262-4263,4294
宁夏枸杞的转基因研究发展已有20多年,文中通过文献整理,对其方法和应用进行了分析总结。目前,转基因枸杞的系统研究只限于中国,应用领域包括抗性研究和植物疫苗制备。文中主要对以上不同应用的研究方法和发展现状进行了综述,提出转基因枸杞应用的广阔前景和需要解决的问题,为学习研究植物工程在中药领域的应用奠定基础。  相似文献   
969.
综述了影响细菌活疫苗真空冷冻干燥的主要因素,以期为细菌活疫苗的工艺开发提供参考。  相似文献   
970.
王蕾  宿烽 《安徽农业科学》2013,(7):2870-2871,2880
文中概述了近几年来番茄基因工程方面的研究进展。其中番茄基因组精细序列分析的完成是这一领域得以快速发展的基础。在育种方面,利用转基因技术生产出了具有各种抗性的番茄植株,获得了具有优良品质的新品种。同时,基因工程手段拓展了番茄在医学上的应用。目前研究人员已利用番茄生产药用蛋白、抗体、口服疫苗、病毒转基因番茄疫苗,并且对番茄红素的研究有望推动对癌症基因疗法的研究。总之,利用基因工程手段,有望使番茄成为集治疗、营养和免疫于一身的新型蔬菜。  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