全文获取类型
收费全文 | 277篇 |
免费 | 21篇 |
国内免费 | 14篇 |
专业分类
林业 | 20篇 |
农学 | 10篇 |
基础科学 | 2篇 |
18篇 | |
综合类 | 114篇 |
农作物 | 8篇 |
水产渔业 | 14篇 |
畜牧兽医 | 115篇 |
园艺 | 3篇 |
植物保护 | 8篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 13篇 |
2012年 | 18篇 |
2011年 | 18篇 |
2010年 | 19篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1954年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有312条查询结果,搜索用时 15 毫秒
1.
2.
3.
卵泡从原始卵泡发育为成熟卵泡,直至排卵、黄体发育等过程都受到精密的调控,产生大量的优势卵泡是绵羊产多羔及实现快速扩繁的关键因素。研究发现,相关信号通路和转录因子通过影响绵羊卵泡中卵母细胞、颗粒细胞的生长,进而调控卵泡的发育成熟,对这些信号通路进行深入了解,有助于探索卵泡发育的调控机制,早日实现绵羊高效繁育。Notch是卵泡发育过程中发挥重要作用的高度保守信号通路,PI3K/AKT/mTOR信号通路各成员都是广泛存在于细胞内的信号转导分子,在卵泡发育早期发挥了主要作用,还有间隙连接(gap junction,GJ)和跨带突触(transzonal projections,TZPs)等物理连接方式,在细胞间的交流通讯起到重要作用。作者详细介绍了Notch信号通路、PI3K/AKT/mTOR信号通路、间隙连接及跨带突触的结构功能在绵羊卵泡发育中的调控作用,为进一步探明绵羊卵泡发育的调控机制提供参考。 相似文献
4.
5.
Molecular and serologic characterization, pathogenicity, and protection studies with infectious bronchitis virus field isolates from California 总被引:6,自引:0,他引:6
In this study, we characterized three variant infectious bronchitis virus (IBV) strains isolated in 2003 and 2004 from broiler chickens in California and compared them to previously isolated California variant viruses and to common vaccine serotypes used in the United States. We conducted genetic, serologic, and pathogenicity studies on all three isolates, then tested different vaccines against one of the viruses. Genetically the three variant IBV strains, designated CA557/03, CA706/03, and CA1737/04, were not related to each other. GenBank BLAST database search and phylogenetic analysis of the hypervariable region of the S1 subunit of the spike gene to determine the most closely related viruses to the three variants showed the CA557/03 variant to be 81.8% similar to the CAV/CA56b/91 whereas the CA706/03 and CA1737/04 variant viruses were only distantly related to Dutch/D1466/81 (72.2%), a vaccine strain used in Europe, and Korea/K142/02 (72.7%), a Korean field isolate, respectively. Cross virus-neutralization testing showed that none of the 2003-04 California IBV variant viruses were serologically related to each other or to Ark, Conn, or Mass vaccine strains. In addition the CA1737/04 isolate was also tested against DE072 and found not to be serologically related. All three variant viruses were pathogenic in 1-wk-old broilers and vaccination with Mass/Conn followed by Holland/Conn provided 80% protection against the CA1737/04 virus. The 2003-04 California variant viruses were not compared with variants isolated in California during 1970s and 1980s because, to our knowledge, no genetic information is available and those viruses are no longer obtainable. This study shows that the CA557/03 virus was distantly related to the CAV-type viruses isolated in California in the early 1990s, but that none of the 2003-04 viruses were similar genetically or serologically to the CAL99-type viruses, indicating that new IBV variants continue to emerge and cause disease in commercial chickens in California. 相似文献
6.
A. M. PIRES M. F. MAGALHÃES L. MOREIRA DA COSTA M. J. ALVES & M. M. COELHO 《Fisheries Management and Ecology》2008,15(1):49-58
Abstract The effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment in Southwest Portugal were investigated. The fish community structure and habitat were surveyed at 10 sites pre- and post-flood. Overall species richness and rank abundances changed little after the flood, despite there being a consistent decline in the abundance of small cyprinids. Pre- and post-flood habitat correlates of abundance changed for at least some species, and variability in assemblage structure was associated with flood, depth and pH. These results indicate that extreme floods occurring early in the wet season may have little disruptive effects on the overall structure of native fish assemblages in Mediterranean streams, although may at least partially influence population dynamics for some species. Habitat quality and complexity are likely to play a role in mediating species responses to flooding. 相似文献
7.
8.
卫星降水产品在缺资料地区开展水文气象研究及径流模拟中发挥着至关重要的作用,然而卫星降水产品的精度可能会影响径流模拟效果。采用多种统计指标和VIC水文模型综合评估5种卫星降水产品(CMORPH-BLD、GSMaP_Gauge、CMFD、MSWEP和PERSIANN-CDR)在雅鲁藏布江流域的精度和拉萨河流域的水文模拟效果。结果表明:(1)CMORPH_BLD和GSMaP_Gauge在少雨季存在低估,CMFD在少雨季与观测值具有很好的一致性。MSWEP和PERSIANN-CDR在多雨季和少雨季存在高估。降水量方面,CMORPH-BLD和CMFD均较为接近观测值,其他降水产品存在不同程度的高估。(2)日尺度上,除CMFD外其他卫星降水数据与观测值具有较小的相关性(0.26~0.45),CMORPH-BLD和CMFD和观测值具有较好的一致性,CMFD和MSWEP探测小降水事件(0.1,0.5,1 mm/d)的能力优于GSMaP_Gauge。各卫星降水产品在探测强降水(2,5,10 mm/d)方面能力不足。日降水2 mm/d的降水阈值为各分类指数的变化点。(3)月尺度上,各降水产品与观测值具有很... 相似文献
9.
10.