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   109篇
  免费   13篇
林业   1篇
基础科学   1篇
  6篇
综合类   18篇
水产渔业   10篇
畜牧兽医   79篇
园艺   2篇
植物保护   5篇
  2023年   2篇
  2021年   3篇
  2020年   1篇
  2019年   8篇
  2018年   4篇
  2017年   3篇
  2016年   3篇
  2015年   4篇
  2014年   2篇
  2013年   7篇
  2012年   2篇
  2011年   3篇
  2010年   1篇
  2009年   2篇
  2008年   1篇
  2007年   1篇
  2006年   2篇
  2005年   2篇
  2004年   1篇
  2003年   3篇
  2002年   2篇
  2001年   3篇
  2000年   1篇
  1999年   3篇
  1998年   7篇
  1997年   5篇
  1996年   2篇
  1994年   1篇
  1993年   6篇
  1992年   5篇
  1991年   5篇
  1990年   6篇
  1989年   5篇
  1988年   4篇
  1979年   1篇
  1969年   1篇
  1963年   1篇
  1945年   1篇
  1940年   1篇
  1919年   1篇
  1896年   4篇
  1895年   1篇
  1890年   1篇
排序方式: 共有122条查询结果,搜索用时 250 毫秒
51.
52.
Atrioventricular valve dysplasia in Dalmatians   总被引:1,自引:0,他引:1  
  相似文献   
53.
54.
55.
56.
The aim of this study was to produce cloned caprine embryos using either caprine bone marrow‐derived mesenchymal stem cells (MSCs) or ear fibroblast cells (EFCs) as donor karyoplasts. Caprine MSCs were isolated from male Boer goats of an average age of 1.5 years. To determine the pluripotency of MSCs, the cells were induced to differentiate into osteocytes, chondrocytes and adipocytes. Subsequently, MSCs were characterized through cell surface antigen profiles using specific markers, prior to their use as donor karyoplasts for nuclear transfer. No significant difference (p > 0.05) in fusion rates was observed between MSCs (87.7%) and EFCs (91.3%) used as donor karyoplasts. The cleavage rate of cloned embryos derived with MSCs (87.0%) was similar (p > 0.05) to those cloned using EFCs (84.4%). However, the in vitro development of MSCs‐derived cloned embryos (25.3%) to the blastocyst stage was significantly higher (p < 0.05) than those derived with EFCs (20.6%). In conclusion, MSCs could be reprogrammed by caprine oocytes, and production of cloned caprine embryos with MSCs improved their in vitro developmental competence, but not in their fusion and cleavage rate as compared to cloning using somatic cells such as EFCs.  相似文献   
57.
Objective   To determine the efficacy of monepantel, a developmental compound from the amino-acetonitrile derivative class of anthelmintics, against field infections of gastrointestinal nematodes in sheep.
Procedures   Comparisons of efficacy (using standard faecal worm egg count reduction tests) and safety (on the basis of visual observations) were made in a large-scale field study in Australia, between groups of sheep treated with either an oral solution of monepantel or a registered anthelmintic. The sheep were naturally infected with the major gastrointestinal nematode genera present in Australia.
Results   The post-treatment efficacy results for monepantel were: at 7 days (±1 day) efficacy was >98%; at 14 days (±1 day) it was generally close to or >99%; and at 21 days (±1 day) efficacy was consistently >99%. A high proportion of the targeted nematode populations were confirmed as being resistant to one or more of the currently available anthelmintic classes.
Conclusions   Monepantel when used under field conditions at a minimum dose rate of 2.5 mg/kg was highly effective against mixed-genus natural field infections of the major gastrointestinal nematode genera including Haemonchus , Teladorsagia ( Ostertagia ), Trichostrongylus , Nematodirus , Chabertia and Oesophagostomum . This result included efficacy against some populations resistant to the currently available broad-spectrum anthelmintics. Few Cooperia spp. were present to allow confirmation of efficacy against this genus. On no occasion after treatment did any commercial anthelmintic-treated groups have significantly lower faecal egg counts than the monepantel-treated groups. Monepantel was safe for the target animals and human operators when used in a field situation.  相似文献   
58.
59.
60.
Since 1994 the Barnacle Goose Management Scheme (BGMS) has integrated conservation and agricultural aims on the Scottish side of the Solway Firth. In the 4 years before the introduction of the BGMS, the density of barnacle geese (Branta leucopsis) on the Wildfowl & Wetlands Trust Reserve at Caerlaverock was four times higher than on the non-Reserve area. In the 6 years following establishment of the BGMS, the density of geese on non-Reserve fields rose so that the Reserve had twice the density of the non-Reserve area. No difference in density was found between fields in the Feeding Zone and Intermediate Zone of the BGMS. The density of barnacle geese around the study area appears to be at a maximum under current management regimes. The remaining geese from this increasing population are using other feeding areas. This may lead to further conservation-agriculture conflict in the future, but could be mitigated through expanding the range and quality of the BGMS, through increasing the dedicated reserve network, or through a combination of the two.  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