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   116篇
  免费   10篇
林业   2篇
综合类   23篇
畜牧兽医   100篇
植物保护   1篇
  2023年   1篇
  2018年   1篇
  2017年   4篇
  2016年   3篇
  2015年   2篇
  2014年   1篇
  2013年   4篇
  2012年   5篇
  2010年   1篇
  2009年   4篇
  2008年   7篇
  2007年   3篇
  2006年   3篇
  2005年   2篇
  2004年   3篇
  2003年   4篇
  2002年   3篇
  2001年   1篇
  2000年   4篇
  1999年   6篇
  1998年   6篇
  1997年   2篇
  1996年   4篇
  1995年   2篇
  1993年   2篇
  1992年   5篇
  1991年   4篇
  1990年   8篇
  1989年   9篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1980年   2篇
  1979年   3篇
  1978年   8篇
  1977年   4篇
  1976年   1篇
排序方式: 共有126条查询结果,搜索用时 0 毫秒
121.
Crustal temperatures within collisional orogens are anomalously high compared with temperatures at comparable depths in stable continents, which is evidence of thermal processes that are fundamental to orogenesis. These temperatures can be explained by the redistribution of crust enriched in heat-producing elements through the accretion of crust from the down-going plate to the upper plate and surface erosion. With the use of geologically reasonable rates, the model results predict high temperatures (over 600°C) and inverted upper-plate geotherms (about 100°C over 20 kilometers) at shallow depths (20 to 40 kilometers) by 25 to 35 million years after collision. This study emphasizes the interdependence of deformational, surficial, and thermal processes.  相似文献   
122.
Influenza B virus is a human pathogen whose origin and possible reservoir in nature are not known. An influenza B virus was isolated from a naturally infected harbor seal (Phoca vitulina) and was found to be infectious to seal kidney cells in vitro. Sequence analyses and serology indicated that influenza virus B/Seal/Netherlands/1/99 is closely related to strains that circulated in humans 4 to 5 years earlier. Retrospective analyses of sera collected from 971 seals showed a prevalence of antibodies to influenza B virus in 2% of the animals after 1995 and in none before 1995. This animal reservoir, harboring influenza B viruses that have circulated in the past, may pose a direct threat to humans.  相似文献   
123.
Global patterns of influenza a virus in wild birds   总被引:1,自引:0,他引:1  
The outbreak of highly pathogenic avian influenza of the H5N1 subtype in Asia, which has subsequently spread to Russia, the Middle East, Europe, and Africa, has put increased focus on the role of wild birds in the persistence of influenza viruses. The ecology, epidemiology, genetics, and evolution of pathogens cannot be fully understood without taking into account the ecology of their hosts. Here, we review our current knowledge on global patterns of influenza virus infections in wild birds, discuss these patterns in the context of host ecology and in particular birds' behavior, and identify some important gaps in our current knowledge.  相似文献   
124.
Fixed‐time post‐cervical artificial insemination (FTAI) drastically reduces labour requirements and increases the use of boars with higher genetic merit. This study evaluated the efficiency of eCG administration combined with/without the GnRH agonist buserelin for the induction and synchronization of ovulation in weaned sows submitted to FTAI. The sows were allocated into three groups. In the control group, the first artificial insemination was performed at the onset of oestrus and repeated every 24 hr. In the eCG+GnRH group, sows received 600 IU eCG at weaning and buserelin (10 μg) after 86–89 hr of eCG, and in the GnRH group, sows received only buserelin after 86–89 hr of weaning. The hormone‐treated sows received a single FTAI after 30–33 hr of buserelin application. All the sows were inseminated with homospermic doses (1.5 × 109 sperm cells/50 ml). The interval between weaning and ovulation was shorter (p < .05) in the eCG+GnRH (133.3 hr) and GnRH (135.9 hr) groups than the control (141.5 hr) group. In the eCG+GnRH group, the sows ovulated earlier (p < .05) than those in the GnRH group (44.5 vs. 48.2 hr after buserelin administration). The reproductive performance of GnRH sows was not compromised when only sows exhibiting oestrus at the time of insemination were considered, but lower farrowing rate and smaller litter size were observed in eCG+GnRH sows. The reproductive performance of eCG+GnRH sows was primarily compromised because the insemination was performed outside the optimal time relative to ovulation; therefore, it is advisable to inseminate them before 116–122 hr after weaning.  相似文献   
125.
Serum samples from 102 veterinarians and 191 pig farmers from the southern part of the Netherlands were investigated for antibodies against Brucella abortus, Leptospira spp, Streptococcus suis serotype II, Hantavirus (HV), and lymphocytic choriomeningitis virus (LCMV). All samples were collected in 1993 and stored until this study was performed. The prevalence of antibodies against B.abortus in veterinarians (4.5%) was significantly higher (P = 0.01) than in pig farmers (0%). None of the veterinarians (0%) and only one pig farmer (0.5%) had antibodies against Leptospira spp. Furthermore, significantly (P = 0.015) more veterinarians (6%) than pig farmers (1%) had antibody titres against muramidase-released protein (MRP),a protein of pathogenic S. suis serotype II strains. None of the veterinarians and a total of 3 (1.6%) pig farmers had antibody titres against HV. The prevalence of antibodies against LCMV tended to be higher in pig farmers (2.6%) than in veterinarians (0%) (P = 0.10). It can be concluded that the prevalence of antibodies against the investigated zoonotic agents in veterinarians and pig farmers is low.  相似文献   
126.
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