全文获取类型
收费全文 | 98篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
林业 | 3篇 |
农学 | 9篇 |
基础科学 | 12篇 |
6篇 | |
综合类 | 34篇 |
农作物 | 6篇 |
水产渔业 | 2篇 |
畜牧兽医 | 32篇 |
植物保护 | 2篇 |
出版年
2024年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有106条查询结果,搜索用时 15 毫秒
1.
2.
Wathes DC Cheng Z Bourne N Taylor VJ Coffey MP Brotherstone S 《Domestic animal endocrinology》2007,33(2):203-225
During the early postpartum period dairy cows mobilize fat and muscle to support lactation. This is associated with alterations in blood metabolite and hormone profiles which in turn influence milk yield and fertility. This study developed models to determine how metabolic traits, milk yield and body condition score were inter-related at different times in the periparturient period and to compare these relationships in primiparous (PP, n=188) and multiparous (MP, n=312) cows. Data from four previous studies which included information on blood metabolic parameters, parity, milk yield, body condition score and diet were collated into a single dataset. Coefficients of polynomial equations were calculated for each trait between -1 week pre-calving and week +7 postpartum using residual maximum likelihood modelling. The completed dataset was used in a multiple correlation model to determine how the best fit curves were related to each other over time. PP cows had higher concentrations of insulin-like growth factor-I and lower beta-hydroxybutyrate concentrations throughout, higher leptin concentrations pre-partum and both the peak in non-esterified fatty acids and the nadir in urea concentration occurred earlier after calving. These differences were associated with significantly lower milk production. Leptin concentrations fell at calving and were related to body condition score. Insulin was negatively correlated with yield in MP cows only. In MP cows the relationship between insulin-like growth factor-I and yield switched from negative to positive between weeks +4 and +7. Both beta-hydroxybutyrate and urea were positively related to yield in PP cows. In contrast, in MP cows beta-hydroxybutyrate was negatively correlated with yield and urea was strongly related to body condition score but not yield. These results suggest that there are differences in the control of tissue mobilization between PP and MP cows which may promote nutrient partitioning into growth as well as milk during the first lactation. 相似文献
3.
4.
Lucia T Corrêa MN Deschamps JC Bianchi I Donin MA Machado AC Meincke W Matheus JE 《Preventive veterinary medicine》2002,53(4):57-292
We evaluated stillbirth risk factors in two commercial swine farms of the Rio Grande do Sul State (south of Brazil). The study was conducted during 1 month in Farm A and during 2 months in Farm B, both during 1999. Data for all farrowings that occurred during the study period were recorded (101 for Farm A and 373 for Farm B), without interference in the farm management. In Farm A, 39% of all litters born during the period of interest had stillborn piglets and the stillborn risk for piglets was 12%. In Farm B, 25% of all litters had stillborn piglets whereas the stillborn risk was 2%. Variables considered as potential risk factors for stillbirths were: parity (1, 2–3, 4+); breed (purebred or crossbred); sow body-condition (normal or fat); use of oxytocin during parturition (yes or no); obstetric intervention through vaginal palpation (yes or no); farrowing duration (<4 or ≥4 h); mummified fetuses (yes or no); total litter size (<12 or ≥12 piglets); and litter birth weight (<11 or ≥11 kg). All stillborn piglets had their classification validated by necropsy. In multivariable logistic-regressions, the cases were the litters having at least one stillborn piglet. In Farm A, litters having at least 12 pigs and in which oxytocin was used during the parturition had 20.8-times-higher odds of stillborn occurrence. In Farm B, litters from sows having parity ≥4 had 2.2-times-higher odds of stillborn occurrence than litters from parity 2 to 3 females, litters having ≥12 pigs had 2.0-times-higher odds of a stillborn piglet than smaller litters and farrowings in which vaginal palpation was performed had 8.0-times-higher odds. Farrowing room management to minimize stillborn risk should target higher-parity females, large litters and optimization of practices of obstetric interventions. 相似文献
5.
油松毛虫卵(块),越冬幼虫,5龄幼虫和蛹种群扩散型指数的刀切估计方法 总被引:1,自引:0,他引:1
张连翔 《内蒙古林学院学报》1997,19(2):32-37
刀切法是一种非参数估计方法,本文就油松毛虫卵(块)、越冬幼虫、5龄幼和蛹种群扩散型指数的刀切估计方法进行了研究。结果表明,与传统方法相比,刀切法能够给出种群扩散型指数的置信区间,弥补了某些指数在统计学上的本质不足,有利于准确、合理地应用扩散型指数测定生物种群的空间格局和聚集强度的比较。虚拟值的正态性间接证明了将刀切法应用于估计种群扩散型指数是适用的。刀切法应该成为生态学者手术一种有用的工具。但要注 相似文献
6.
针对现行检测站的台架试验检测无法真实地反映其制动性能,而道路试验的随机性大、重复性较差等问题.在理论分析的基础上建立ABS汽车的制动性能检测结果的区间函数,结合高速道路试验,对其结果进行评价.结果表明:该方法能大大地减少道路试验的随机性.并能可靠地对ABS汽车的制动性能进行评价. 相似文献
7.
[目的]为提高芜湖地区荷斯坦牛的受胎率提供参考依据.[方法]基于奶牛场多年生产记录,研究不同季节、胎次与年单产水平对芜湖地区中国荷斯坦奶牛受胎率的影响.[结果]气温对奶牛受胎率有显著影响(P<0.05),而湿度对奶牛受胎率的影响不显著(P>0.05).胎次和年单产水平对奶牛受胎率有极显著影响(P<0.01).夏季由于热应激,奶牛的受胎率会明显低于其他季节,秋季的奶牛受胎率最高.胎次越高的奶牛受胎率越低,青年奶牛的受胎率最高;年单产水平越高,奶牛的受胎率越低.[结论]不同季节、胎次与年单产水平对奶牛的受胎率都有影响. 相似文献
8.
从多价原子辐射跃迁所必须满足的宇称守恒,即从拉波特定则出发,详细讨论了选择定则ΔL=0跃迁禁戒和可能的情形,从而揭示出相关的物理本质。 相似文献
9.
《中国畜牧杂志》2019,(2)
为探究胎次对母猪产弱仔、死胎的影响,实验对广西某猪场2015年12月——2017年11月的8 028窝大白母猪的胎次和产弱仔数、死胎数进行统计分析。结果表明:不同胎次母猪产弱仔数和死胎数具有极显著差异(P<0.01),其中第1胎次母猪弱仔数显著高于其他胎次母猪(P<0.05),且弱仔数均值呈逐渐下降趋势;第5胎次母猪的死胎数显著低于其他胎次(P<0.05),且死胎数均值近似呈先下降后上升的趋势;对产弱仔数和死胎数占总产仔数的比例进行分析进一步证明了上述结果。综上,第2~6胎次母猪产弱仔数和死胎数都相对较少,产仔性能最好,规模化猪场可以考虑淘汰7胎以上的母猪;对第1胎次的母猪建设P1场(第1胎次母猪场),制定更为严格的"驯化"和饲养工作。 相似文献
10.
通过研究不同胎次、产犊季节和犊牛初生重、犊牛性别、产犊方式等因素对荷斯坦牛难产程度的影响,旨在降低难产率,帮助牛场制定合理有效的繁殖管理措施。试验收集上海金山奶牛场2018年1~12月产犊难易记录共2 812条,采用GLM模型对影响奶牛难产程度的因素进行分析。结果表明,胎次、产犊季节、犊牛初生重、犊牛性别、产犊方式对难产程度有显著影响(P<0.05),且第二胎奶牛自然分娩比例最高;春季和夏季产犊低难产度所占比例较大;随着犊牛初生重的增加,难产程度逐渐增大;生公犊难产程度越大;双胎生产方式难产度增大。 相似文献