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   1864篇
  免费   139篇
  国内免费   53篇
林业   223篇
农学   61篇
基础科学   10篇
  82篇
综合类   834篇
农作物   26篇
水产渔业   352篇
畜牧兽医   390篇
园艺   42篇
植物保护   36篇
  2024年   6篇
  2023年   13篇
  2022年   28篇
  2021年   45篇
  2020年   48篇
  2019年   38篇
  2018年   36篇
  2017年   46篇
  2016年   65篇
  2015年   56篇
  2014年   81篇
  2013年   96篇
  2012年   119篇
  2011年   132篇
  2010年   139篇
  2009年   154篇
  2008年   143篇
  2007年   126篇
  2006年   115篇
  2005年   121篇
  2004年   79篇
  2003年   75篇
  2002年   52篇
  2001年   48篇
  2000年   26篇
  1999年   19篇
  1998年   14篇
  1997年   31篇
  1996年   21篇
  1995年   14篇
  1994年   12篇
  1993年   14篇
  1992年   13篇
  1991年   13篇
  1990年   4篇
  1989年   6篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1984年   2篇
  1980年   1篇
  1956年   1篇
排序方式: 共有2056条查询结果,搜索用时 31 毫秒
971.
猪乙型脑炎的诊断在实验室是简单方便的,但是在我国的广大农村由于受到器材、人员的限制,诊断比较困难.针对这种情况,提出了Dot-ELISA检测法、斑点金免疫渗滤法和SPA协同凝集等几种简单方便快捷的在农村有极大潜力的血清学诊断方法.  相似文献   
972.
本研究旨在探讨蜂王浆对雌性日本大耳兔初情期前的生长发育影响。将36只50日龄雌性日本大耳兔随机分为高剂量蜂王浆组(H-RJ)、低剂量蜂王浆组(L-RJ)以及对照组(C),每组12只。高、低剂量组分别按体质量0.2%和0.1%的量每天进行空腹灌胃蜂王浆,对照组灌胃体质量0.1%的生理盐水。每周同一时间空腹称重。40d后,所有兔子耳静脉取血后各组处死6只,摘取心脏、左侧卵巢和左侧子宫称重,并冷冻保存右侧卵巢和右侧子宫。采用放免法测定血清中雌二醇(E2)、促卵泡素(FSH)、促黄体素(LH)、孕激素(P4)、催乳素(PRL)和睾酮(T)的含量;用实时荧光定量PCR检测右侧卵巢中雌激素β受体(ERβ)mRNA和右侧子宫中雌激素α受体(ERα)mR-NA的表达。结果表明:灌胃蜂王浆12d后,对照组兔子没有换毛现象,低剂量和高剂量组分别有75%和67%的兔子换毛;蜂王浆对体质量和心脏、左侧子宫、左侧卵巢的脏器系数无显著影响(P>0.05)。试验组血液中E2浓度极显著高于对照组(P<0.01),而其它性激素无明显差异(P>0.05)。试验组ERα在子宫和ERβ在卵巢的表达量均低于对照组,对照组与高剂量组的差异极显著(P<0...  相似文献   
973.
The distribution, density and histochemical characteristics of mast cells in the lungs of the Japanese quail were investigated during the post-hatching period. In the period starting from the first to the 60th day post-hatching, based on proteoglycan content, three types of mast cells, which were alcian blue-positive, safranin O-positive and alcian blue/safranin O-positive, were found to exist in the lungs. The application of staining with berberine sulphate demonstrated that, similar to the distribution of safranin O-positive cells, the heparin-containing cells were located in the periphery of large blood vessels. The percentages of mast cells in different localization sites of the lungs were found to vary with age in the post-hatching period with toluidine blue staining. The lack of any statistically significant increase/decrease in the number of mast cells per unit area of the right and left lung lobes is partially in favour of the proposal that the mast cell number increases with the growth of the lung volume in the post-hatching period.  相似文献   
974.
The British Equine Veterinary Association (BEVA) was established in 1961 and launched the Equine Veterinary Journal (EVJ) in 1968. This review outlines some of the major advances in equine science and practice that have occurred in that time and the role played by the Journal in facilitating those developments.  相似文献   
975.
Dairy farm agricultural income should increase when sexed semen is used instead of unsexed semen. This study simulated three scenarios: using unsexed semen (N), using X sperm of Holstein and unsexed semen of Japanese Black (H), and using X sperm of Holstein and Y sperm of Japanese Black (HJ). Two management scenarios were considered: conventional management (CONV); and the use of Japanese Black semen with surplus cows to produce F1s where sufficient replacement female Holstein calves were obtained for maintenance (MAINT). In CONV, the agricultural incomes of H and HJ were 610 000–2 400 000 yen higher than that of N. The agricultural income increased when the difference in the prices between Holstein males and average F1 male/female calves was 34 000–50 000 yen, that between Holstein male and female calves was 80 000–110 000 yen, and that between F1 male and female calves was 50 000–90 000 yen. Therefore, the agricultural income can be increased by using sexed semen to select calves of a more valued breed and sex.  相似文献   
976.
In the meat industry, correct labeling of beef origins or breed is required to assure quality and safety. This paper describes the development of discrimination markers between Japanese domestic and imported beef from the United States (US) and Australia (AUS) based on a bovine 50K single nucleotide polymorphism (SNP) array using a total of 110 samples: Japanese Black (n = 50), Japanese Holstein (n = 50) and US cattle (n = 10). Genotyping information revealed 1081 SNPs as candidate markers that were polymorphic only in US cattle. The genotyping results by PCR – restriction length polymorphism in Japanese Black (n = 300) and Holstein cattle (n = 146) revealed that 11 SNPs had alleles specific to US cattle. Their allelic frequencies in US cattle (n = 108) ranged from 0.097 to 0.250 with an average of 0.178 and the combined identification probability of US cattle was 0.987. In addition, we also verified the applicability of these US‐specific markers to AUS cattle. Their allelic frequencies in AUS cattle (n = 280) ranged from 0.063 to 0.224 with an average of 0.137 and the combined identification probability of AUS cattle was 0.963. In conclusion, a set of these markers could be useful for discriminating between Japanese domestic and imported beef and would contribute to identify origins and prevent falsified labeling of beef.  相似文献   
977.
The objective was to evaluate the sensory categorisation of beef by Japanese consumers, based on Meat Standards Australia methodology. Various cuts of beef, with a wide range of quality (from Australian and Japanese cattle) and three cooking methods (grill, yakiniku, shabu shabu), were evaluated by 1620 Japanese consumers in Tokyo and Osaka. Consumers rated each sample for four sensory attributes (tenderness, juiciness, flavor and overall satisfaction), then selected one of four grades (unsatisfactory/2‐star, good everyday/3‐star, better than everyday/4‐star, and premium quality/5‐star), based on the quality of the beef within each cooking method. Meat quality scores, denoted as MQ4 scores (weighted combination of the four sensory attributes) were calculated from the Japanese consumer test results, to describe the Japanese consumer rating of beef. The distribution of the Japanese consumer MQ4 scores showed a clear distinction between grades, with the majority of scores being included within the boundaries of each grade. The MQ4 score allocated approximately 64% of the samples to their correct consumer grades. The MQ4 score showed potential to be used as a tool in developing and monitoring a consumer‐focused grading system that is able to predict Japanese consumer satisfaction of individual beef cuts prepared by different cooking methods.  相似文献   
978.
5种脑炎人兽共患病病毒多重RT-PCR检测方法的建立   总被引:3,自引:0,他引:3  
为建立同时检测流行性乙型脑炎病毒(JEV)、森林脑炎病毒(TBEV)、东方马脑炎病毒(EEEV)、西方马脑炎病毒(WEEV)和基孔肯雅病毒(CHIKV)5种人兽共患脑炎病病毒的多重RT-PCR方法,本研究根据GenBank登录的相关病毒基因序列设计特异引物,通过优化引物组合及PCR反应条件,建立可同时检测5种病毒的方法,扩增片段长度分别为411 bp(JEV)、945 bp(TBEV)、193 bp(EEEV)、545 bp(WEEV)和769 bp(CHIKV);该方法具有良好的特异性,对病毒核酸最低检测拷贝数分别为7.1×103、3.6×103、2.2×103、5.6×103和5.1×103.该方法具有特异性强、灵敏度高、操作简便等优点,为以上5种人兽共患脑炎病病毒提供快速检测手段.  相似文献   
979.
为深入探索日本脑炎病毒(Japanese encephalitis virus,JEV)WHe株的致病机理,并为新型疫苗研发提供技术支持,采用长链RT-PCR技术对其基因组全长cDNA进行了扩增鉴定,并对含复杂二级结构的3′末端和5′末端非编码区扩增片段进行了测序分析。扩增结果表明,扩增出的JEV WHe株基因组全长cDNA分子近11 kb大小;非编码区测序分析表明,扩增产物为WHe株所特有。提示长链RT-PCR法可用于JEV WHe株基因组全长cD-NA的扩增。  相似文献   
980.
中国茶多酚类文献研究   总被引:1,自引:1,他引:1       下载免费PDF全文
从全国七千多种期刊中搜集到茶多酚类的专题文献960篇.统计结果表明:13年来这类文献数量呈台阶式上升趋势,年平均递增率15%;共有第一署名作者544人,署名机构585个;有333种期刊载有茶多酚类文献,以医学、农业、食品、化工化学类期刊为主;文献的主要专业结构为:医卫类478篇,食品饲料类159篇,农业类122篇.文章还对茶多酚类文献的发展规律,作者、机构及载文期刊的构成和分布规律,文献所涉及专业及其主题等进行了统计和讨论.  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