全文获取类型
收费全文 | 235篇 |
免费 | 4篇 |
专业分类
林业 | 13篇 |
农学 | 3篇 |
基础科学 | 1篇 |
42篇 | |
综合类 | 18篇 |
农作物 | 36篇 |
水产渔业 | 18篇 |
畜牧兽医 | 99篇 |
园艺 | 3篇 |
植物保护 | 6篇 |
出版年
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 5篇 |
2011年 | 16篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 3篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1932年 | 1篇 |
1931年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 15 毫秒
61.
Rubber topped slatted floor gives more lying comfort to intensive fed fattening bulls, reduces risks of integument lesions as well as increases their locomotion comfort. On the other side there are more fissured alterations and defects in the sole and heel horn due to lack of sufficient wear away which often made the bearing surface to be overgrown. Overgrown claws are also seen on solid slatted floors, but these horn parts were normally grated down in short time that frequently goes along with abrasions of the claw peak and the wall horn as well. The current experiences of our study show favour to the use of a floor that combines hard and soft qualities. Weak claw performance and health has a link to a bad state of cleanness of the pens and the animals as well and must be assessed with regard to permanent wetness on the grounds. Animals out of greater pens are less dirty because the solid floor becomes sooner dry than in cases with higher crowding degrees of animals. More space per animal and higher comfort gives chance for higher daily weight gain. The recordings and evaluations of this project are still in progress. 相似文献
62.
63.
前面的话:美国曼宁顿,创建于1915年的专业地板制造商,历经4代人的营运和创新,发展为拥有众多专利技术和设计大奖的国际化专业地面材料生产商。如今美国曼宁顿总部位于美国新泽西州的赛伦市,并在全美设立8个制造基地。他们通过了解客户的需求、与专业设计人士的密切合作,不断创新,制造出一系列高品质住宅及商用地板为全球许多知名工程提供了全面的地板解决方案。他们屡获美国最佳地板制造商奖和众多设计突出贡献奖。 相似文献
64.
65.
A. R. Mosley S. R. James K. A. Rykbost D. C. Hane C. E. Stanger C. C. Shock J. J. Pavek D. L. Corsini J. C. Miller S. L. Love R. E. Thornton D. G. Holm R. E. Voss 《American Journal of Potato Research》2000,77(3):161-165
Century Russet, a high-yielding, late-maturing variety suitable for fresh tablestock use, was jointly released in 1995 by Agricultural Experiment Stations in Oregon, Idaho, Washington, Colorado, California, and Texas and the USDA Agricultural Research Service. Extremely high yields have been observed for Century Russet in variety trials conducted in Oregon and throughout the western United States under a wide range of soil and climatic conditions. Century Russet produced 40 percent higher marketable yields than Russet Burbank and 67 percent higher marketable yields than Russet Norkotah in 11 regional trials conducted over a three-year period in sevenwestern states. Uniform tuber shape, high yields of count carton sizes, and attractive tuber appearance make Century Russet well suited for the fresh market industry. It is not recommended for chipping or processing into frozen products because of low solids and dark fry color. Century Russet is highly resistant toVerticillium wilt and consistently develops less hollow heart, brown center, and other internal defects than Russet Burbank. It requires more time between vine kill and harvest than Russet Burbank for adequate tuber maturity and skin set. Bruised Century Russet tubers are susceptible to early blight andFusarium infection. 相似文献
66.
67.
Anna Radtke David Toe Frederic Berger Stefan Zerbe Franck Bourrier 《Annals of Forest Science》2014,71(4):485-494
? Context
One eighth of Europe’s forests are still managed as coppice. In some European countries, more than half of the forest exhibits coppice structures from the past or present coppice management. Many of these forests grow in the broadleaf zone of mountainous regions, often on steep slopes. Here, they play an important role in rockfall protection. However, it remains unclear how coppice forests should be structured for optimal rockfall protection or how the protection effect changes during the aging of the coppice.? Aim
A few studies have applied rock trajectory analyses, but so far, no process-based model has been used to quantify the protective effect of differently structured coppice forests. The present study compared 40 coppice patches from two chronosequences in South Tyrol, North Italy, regarding their protective effect against rocks of two sizes using the rockfall simulation model Rockyfor3D.? Results
The results indicate that coppice stands older than 30 years better protect against rockfall than medium-aged and young stands, although the old ones have lower stem densities. Surprisingly, a random stem distribution had a better protective effect than the clumped stem distribution typical for coppice stands.? Conclusion
Implications for future management are discussed in detail, including the relevance of standards in coppice forests. 相似文献68.
Heike Kawaletz Inga Mölder Peter Annighöfer André Terwei Stefan Zerbe Christian Ammer 《Annals of Forest Science》2014,71(3):337-347
Context
Identifying the traits of exotic species may explain their invasiveness and help control the negative impacts of these species on native ecosystems. In this study, we investigated root competition as an important driver for the competitiveness of two exotic tree species in the seedling stage.Aims
In a pot experiment, carried out in Central Europe, we studied the effect of root competition of two exotic tree species (Prunus serotina Ehrh. and Robinia pseudoacacia L.) on biomass allocation of two native ones (Quercus robur L. and Carpinus betulus L.).Methods
Seedlings of these species were exposed to intra- and interspecific mixtures with and without the effect of root competition. For this, belowground plastic partitions were installed in the pots.Results
Competition intensity in the pots increased over time, irrespective of mixture type. However, this increase was much higher for the native species if mixed with the exotic species compared to monocultures or inter-native mixtures. In addition to ontogeny, competition affected biomass allocation patterns. Under root competition by the exotic species, the native species preferentially allocated their biomass to the roots. A higher allocation to the roots was mainly achieved at the expense of leaf and branch biomass.Conclusion
Root competition of P. serotina and R. pseudoacacia may be a reason for the lack of Q. robur and C. betulus in the seedling stage in natural environments where all four species occur. 相似文献69.
Background
It has not yet been shown that ossification of ungular cartilages (OUC) is a pathological condition. Beside heredity, factors such as sex, age, repeated concussion, local trauma, hoof and body size have been suggested as contributing factors for OUC development. By comparing radiographs of front hooves from cold-blooded trotters with different age we wanted to evaluate when development of OUC in cold-blooded trotters occurs and if and when it stabilizes in relation to age and workload. Diagnosis and grading of OUC were based on radiological field examinations of 649 Swedish and Norwegian cold-blooded trotters’ front hooves. A hundred and forty-seven of the horses were re-examined 3-13 years (mean age 9, median 8 years) after the first occasion. All radiographs were evaluated blind, using two different grading systems for OUC. Work load, in form of number of races completed, and body size score were collected from official data. Four statistical ordinal regression models were used, compared and evaluated.Results
We identified a breakpoint at 2.8 ± 0.38 years of age when ossification ends and proposed a simpler grading system with more consistent results. There was no significant correlation between body size and grade of OUC. Comparison of different statistical methods for evaluation of ordinal data revealed a piecewise linear regression model as most suitable.Conclusions
Individuals with OUC developed this condition during the stage of life when their hooves develop in size. Results from this study can assist equine practitioners when examining and for understanding this condition in their clinical work and is also beneficial for the Scandinavian equine industry when devising breeding programs. 相似文献70.