全文获取类型
收费全文 | 172篇 |
免费 | 12篇 |
专业分类
林业 | 1篇 |
11篇 | |
综合类 | 19篇 |
农作物 | 1篇 |
水产渔业 | 8篇 |
畜牧兽医 | 137篇 |
园艺 | 2篇 |
植物保护 | 5篇 |
出版年
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1995年 | 3篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1972年 | 3篇 |
1969年 | 2篇 |
1943年 | 2篇 |
1942年 | 2篇 |
1941年 | 1篇 |
1936年 | 2篇 |
1935年 | 3篇 |
1932年 | 2篇 |
1931年 | 1篇 |
1930年 | 2篇 |
1929年 | 2篇 |
1928年 | 1篇 |
1927年 | 4篇 |
1926年 | 1篇 |
1911年 | 3篇 |
1910年 | 1篇 |
1893年 | 1篇 |
排序方式: 共有184条查询结果,搜索用时 46 毫秒
51.
52.
Gunn R 《Science (New York, N.Y.)》1966,151(3711):686-687
Hail and graupel falling through rain collect water that selectively dribbles upward from the upper surface of a hailstone. When the hailstones are polarized by nearly vertical electrostatic field these vertically discharged water drops carry away free charge of the same sign as that induced on the upper surfaces. The hail thereby accumulates an equilibrium charge of opposite sign, corresponding to the charges induced on the bottom surfaces. The equilibrium charges are large enough to be important in thunderstorms. 相似文献
53.
54.
55.
56.
Many economically important cattle diseases spread between herds through livestock movements. Traditionally, most transmission models have assumed that all purchased cattle carry the same risk of generating outbreaks in the destination herd. Using data on bovine viral diarrhoea virus (BVDV) in Scotland as a case example, this study provides empirical and theoretical evidence that the risk of disease transmission varies substantially based on the animal and herd demographic characteristics at the time of purchase. Multivariable logistic regression analysis revealed that purchasing pregnant heifers and open cows sold with a calf at foot were associated with an increased risk of beef herds being seropositive for BVDV. Based on the results from a dynamic within-herd simulation model, these findings may be partly explained by the age-related probability of animals being persistently infected with BVDV as well as the herd demographic structure at the time of animal introductions. There was also evidence that an epidemiologically important network statistic, “betweenness centrality” (a measure frequently associated with the potential for herds to acquire and transmit disease), was significantly higher for herds that supplied these particular types of replacement beef cattle. The trends for dairy herds were not as clear, although there was some evidence that open heifers and open lactating cows were associated with an increased risk of BVDV. Overall, these findings have important implications for developing simulation models that more accurately reflect the industry-level transmission dynamics of infectious cattle diseases. 相似文献
57.
Chemical conditions at lake charr (Salvelinus namaycush) spawning sites were monitored during snowmelt in low alkalinity lakes in Ontario, Canada. Embryos within the interstitial water of the spawning substrate were exposed to abrupt and potentially toxic levels of H+ and inorganic Al as acidic runoff water inundated the shallow nearshore sites. Early runoff events, those that occurred while the lake ice was still snow-covered and under-ice water temperatures were <2°C, appeared to be most threatening, because of deep penetration of the runoff water. These highly site-specific events exhibit wide temporal and spatial variability. 相似文献
58.
TH Morris SW Paine PW Zahra EC Li SA Colgan SL Karamatic 《Australian veterinary journal》2020,98(12):578-585
Animals used in sport should be treated as required to ensure animal welfare but any such use of medication should also be controlled to ensure integrity. Pharmacokinetic studies on groups of six greyhounds were performed to measure plasma and urine levels of carprofen and firocoxib to inform medication control advice. Using the standard methodology for medication control the Irrelevant Plasma Concentration was determined as 20 and 2 ng/mL for carprofen and firocoxib, respectively. The Irrelevant Urine Concentration was also determined as 0.3 and 2 ng/mL for carprofen and firocoxib, respectively. These Irrelevant Plasma and Urine Concentrations will allow laboratory Screening Limits, Detection Times and Withdrawal Time advice to be determined and publicised by regulators of greyhound racing. The Screening Limits will also inform Recommended Limits of Detection if meat-containing residues of these medications are fed to greyhounds. 相似文献
59.
Silje Kristoffersen Torbjørn Tobiassen Margrethe Esaiassen Gunn Berit Olsson Lars A Godvik Magnus A Seppola & Ragnar L Olsen 《Aquaculture Research》2006,37(15):1556-1564
Aquaculture is promising in increasing the amount of fresh Atlantic cod available all year around. The aim of this study was to investigate the effects of pre‐rigour filleting on fillet quality of wild and farmed cod. Pre‐rigour filleting resulted in significantly less fillet gaping than in fillets produced post rigour. The pre‐rigour fillets were, however, 12–13% shorter post rigour. In spite of the significantly lower water content of the muscle 6 days post mortem, a significantly higher liquid loss was seen in the pre‐rigour group. Differences in gaping score and muscle pH were dependent on whether the fish were wild or fed. Fillet gaping increased with storage time and was particularly pronounced for well‐fed cod. Fed cod had a significantly higher hydroxyproline (Hyp) content and significantly lower amount of glycosaminoglycans (GAGs) than wild cod. The ratio between GAGs and Hyp was thus significantly lower in fed cod. A connection between connective tissue components and fillet gaping may exist. However, further investigations are required. 相似文献
60.
Evaluation of a fibrillin 2 gene haplotype associated with hip dysplasia and incipient osteoarthritis in dogs 总被引:1,自引:0,他引:1