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   227篇
  免费   3篇
  国内免费   2篇
林业   10篇
农学   5篇
基础科学   7篇
  9篇
综合类   79篇
农作物   2篇
水产渔业   1篇
畜牧兽医   112篇
园艺   3篇
植物保护   4篇
  2022年   2篇
  2018年   2篇
  2016年   3篇
  2015年   2篇
  2014年   4篇
  2012年   11篇
  2011年   13篇
  2010年   6篇
  2009年   8篇
  2008年   17篇
  2007年   4篇
  2006年   17篇
  2005年   10篇
  2004年   12篇
  2003年   11篇
  2002年   6篇
  2001年   8篇
  2000年   9篇
  1999年   8篇
  1998年   5篇
  1997年   2篇
  1995年   4篇
  1994年   5篇
  1993年   3篇
  1990年   5篇
  1989年   4篇
  1986年   2篇
  1979年   3篇
  1974年   3篇
  1971年   1篇
  1970年   2篇
  1969年   1篇
  1966年   1篇
  1960年   1篇
  1958年   2篇
  1957年   3篇
  1956年   3篇
  1955年   1篇
  1954年   2篇
  1948年   1篇
  1947年   1篇
  1942年   1篇
  1941年   2篇
  1939年   2篇
  1937年   1篇
  1936年   1篇
  1935年   2篇
  1932年   1篇
  1931年   1篇
  1893年   1篇
排序方式: 共有232条查询结果,搜索用时 15 毫秒
1.
企业和人一样,也会生病。企业诊断就是给企业看病。  相似文献   
2.
编者按1997年将是农电企业计算机应用向纵深发展的一年。在全国各行各业联网大潮的推动下,农电企业今后一段时期的主要技术课题将是建设计算机网络,实现企业信息共享,使生产管理工作步入现代化的轨道。针对当前农电企业计算机应用水平落后、人才债乏、经济条件有限等问题,本栏将有针对性地向全国读者介绍适合我国国情及农网特点的、具有一定代表意义的县(市)局建设、管理、使用计算机网络以及开发计算机网络应用软件的成功经验和典型示例。本期介绍的是黑龙江省尚志市电业局借助高校人才、技术优势开发的企业MIS系统。目前,该系统…  相似文献   
3.
In this investigation, natural infection with Mycoplasma hyosynoviae was followed in groups of individual pigs in three different herds with regard to occurrence of tonsillar carrier state, clinical arthritis and development of antibodies in serum and in synovial fluid. Antibodies were detected by a polyclonal enzyme-linked immunosorbent assay (ELISA) developed for experimental use. The infection with M. hyosynoviae progressed very differently in the three herds investigated. In one herd, the infection was apparently limited to adult pigs. In a second herd, all pigs became tonsillar carriers of M. hyosynoviae, but no mycoplasma-related arthritis nor any serological response was demonstrated within the growing-finishing period. In the third herd investigated, tonsillar infection was detected in all pigs, clinical cases of M. hyosynoviae arthritis followed and a moderate serological response was observed in some, but not all, pigs. In all three herds, M. hyosynoviae infection was carried in the tonsils of the adult pigs, but it was only occasionally transmitted from sows to piglets. Maternal antibodies were transferred to the piglets and persisted for approximately 8-12 weeks. After weaning, some pigs became infected before 20 weeks of age, while others did not. In the majority of cases, the tonsillar infection was established from 11 weeks of age or older. A latent tonsillar infection was present for a period of several weeks within the group of investigated pigs before cases of generalized infection and arthritis were seen. In some cases, generalization of M. hyosynoviae infection in the blood and in joints was observed in spite of the detection of an active serological response a few weeks earlier. The present work suggests that generalization of the infection and development of arthritis may depend on age, immunity, virulence factors and/or infection pressure; in some herds maybe combined with certain triggering mechanisms such as stress and lowered general resistance.  相似文献   
4.
A microbiological study of the mycoplasma flora in the respiratory tracts of cattle and goats in selected regions of Tanzania is described. In the examination of cattle, mycoplasmas were isolated from 60 (17.8%) of the 338 examined lung samples, 8 (47.1%) of the 17 lymph nodes, 4 (13.3%) of the 30 pleural fluid samples and 4 (3.9%) of the 103 nasal swabs examined. All the isolates were identified as Mycoplasma mycoides subsp. mycoides, Small Colony type except for one isolate from pleural fluid which was identified as Mycoplasma arginini. M. mycoides subsp. mycoides, Small Colony type was isolated from samples originating from Dodoma, Iringa, Mbeya, Morogoro and Shinyanga regions where outbreaks of contagious bovine pleuropneumonia had been reported. In the examination of goats, mycoplasmas were isolated from 54 (34.0%) of the 159 examined lung samples, 41 (18.1%) of the 226 nasal swabs and 4 (40.0%) of the 10 pleural fluid samples. The species demonstrated were Mycoplasma capricolum subsp. capripneumoniae, M. mycoides subsp. mycoides, Small Colony type Mycoplasma ovipneumoniae and M. Capricolum subsp. arginini. The isolation of M. capripneumoniae in the Coast and Morogoro regions confirmed the presence of contagious caprine pleuropneumonia in the regions.  相似文献   
5.
A study on the prevalence of mycoplasmas in pneumonic bovine lungs was performed on material submitted for diagnostic purposes at the Danish Veterinary Laboratory, Copenhagen. Among the 50 examined cases 43 (86.0%) were found to be infected with mycoplasmas. The predominant mycoplasmas were Ureaplasma spp. (72.0%), M. dispar (48.0%) and M. bovis (24.0%). Other mycoplasmas were M. bovirhinis (20.0%) and M. bovigenitalium (6.0%). Among the infected lungs multiple species infections were predominant (76.7%) over single species infections (23.3%) with M. dispar-Ureaplasma (25.6%), M. bovis-Ureaplasma (18.6%) and M. dispar-M. bovirhinis-Ureaplasma (11.6%) infections being the most frequently encountered combinations. There appears to be an increasing prevalence of M. bovis (24.0%) as compared to earlier reports (0.6-2.0%), thus calling for special attention upon this mycoplasma. Pulsed field gel electrophoresis (PFGE) analysis of 11 field isolates of M. bovis from 9 different farms revealed different profiles except for 2 isolates which were recovered from the same farm. Because mycoplasmas belonging to the 'M. mycoides cluster' were not encountered during this study; it appears that the Danish cattle population is still free from this group of mycoplasma in spite of their presence in some other European countries.  相似文献   
6.
地瓜在正常情况下不会引起猪中毒,但是由于贮藏、加工不当引起发芽、变质就会引起中毒,极易引起中毒。2013年3月16日某猪饲养户,饲养了12头猪,在中午吃完地瓜后10多min开始有个别猪出现呼吸困难,多尿,可视黏膜发绀,体温37.5-39℃,耳尖、四肢末端发凉,呕吐、腹泻等,经现场检查食物和临床表现确认是猪食地瓜引起的中毒。该农民就是为了提高地瓜的价值,将地瓜贮藏起来,过冬后卖个好价钱,但在贮藏过程中出现了变质地瓜,为了降低饲养成本,把没有处理好的变质地瓜用来喂猪,结果出现中毒现象。  相似文献   
7.
通过显微镜检查对来源于全国各地的37种出口观赏鸟进行了血液原虫调查。共检查血样1144份,结果为:血液原虫的检出率为2.1%,主要是血变原虫和/或疟原虫。感染季节以秋冬两季为主,易感鸟品种主要是白腰文鸟、红喉歌鸲、蓝歌鸲、暗绿绣眼鸟、豆冠、白燕、情侣鹦鹉。  相似文献   
8.
2001年月11月-2002年12月间,用血凝抑制试验(HI)对28种出口观赏鸟的600份血清进行了NDV血清抗体监测。结果:阳性抗体1:2滴度的检出率为69.8%、1:4的为15.3%、1:8(含1:8以上)的为4.8%;冬春两季的检出率比夏秋两季高。被检雀形目的10个科28种观赏鸟中全部检出不同程度的NDV血清阳性抗体,抗体滴度在1:4以上的有9个科,分别是雀科、梅花雀科、绣眼科、鸫亚科、鹎科、巫鸟科、书眉画科和百灵科,其中以梅花雀科和百灵科的检出率最高。  相似文献   
9.
酯化反应催化剂的研究进展   总被引:15,自引:0,他引:15  
笔者综述了各类酯化反应催化剂的优缺点。介绍了HZSM-5分子筛和固体超强酸催化剂的制备方法;指出了新型催化剂用于工业生产需要解决的问题。  相似文献   
10.
本文论述了温度应力、温度荷载的取值,并根据实际情况提出了结构设计和施工时裂缝控制的构造措施。  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