收费全文 | 12247篇 |
免费 | 742篇 |
国内免费 | 1806篇 |
林业 | 710篇 |
农学 | 1309篇 |
基础科学 | 1167篇 |
3103篇 | |
综合类 | 4686篇 |
农作物 | 1062篇 |
水产渔业 | 578篇 |
畜牧兽医 | 1144篇 |
园艺 | 363篇 |
植物保护 | 673篇 |
2024年 | 110篇 |
2023年 | 270篇 |
2022年 | 481篇 |
2021年 | 503篇 |
2020年 | 540篇 |
2019年 | 665篇 |
2018年 | 526篇 |
2017年 | 636篇 |
2016年 | 797篇 |
2015年 | 603篇 |
2014年 | 750篇 |
2013年 | 953篇 |
2012年 | 953篇 |
2011年 | 974篇 |
2010年 | 794篇 |
2009年 | 720篇 |
2008年 | 602篇 |
2007年 | 683篇 |
2006年 | 572篇 |
2005年 | 434篇 |
2004年 | 309篇 |
2003年 | 267篇 |
2002年 | 203篇 |
2001年 | 187篇 |
2000年 | 164篇 |
1999年 | 167篇 |
1998年 | 141篇 |
1997年 | 134篇 |
1996年 | 126篇 |
1995年 | 98篇 |
1994年 | 84篇 |
1993年 | 73篇 |
1992年 | 67篇 |
1991年 | 49篇 |
1990年 | 46篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1963年 | 2篇 |
1962年 | 6篇 |
2. The Cobb–Douglas production function was used to assess the changes of output elasticities as well as technical changes in broiler production, for 5-year sub-periods separately.
3. Technical indices of broiler production significantly improved between years 1994–2013: feed conversion ratio decreased from 2.50 kg/kg to 1.78 kg/kg, mortality rate from 8.8% to 4.0% and daily weight gain increased from 37.1 g/d to 58.7 g/d, respectively.
4. Before accession to the EU, there was a substantial increase of fixed capital connected with modernisation of buildings and equipment. In the period 1994–2013, inputs of fixed capital per kilogram of livestock increased by 72% and at the same time the input of labour decreased by 56%.
5. Technical changes in years 1994–1998 contributed to a rapid production increase at a rate of 4.6% annually and only by up to 0.7% annually during 2009–2013. The slowdown of production rate increase after 2009 was partially caused by decreasing the stocking density. 相似文献
2. Animal welfare and cage-free housing dominate future needs of the market. Nesting behaviour and minimal tendency to develop feather-pecking or cannibalism without beak treatment are key trait complexes. Stronger shells for longer production cycles without moulting have to be combined with better bones.
3. No single big gene effect can be expected to control the multifactorial problem of feather-pecking. Adjusting the shape of the beak, with a heritability of .10–.25, can contribute to reducing the risk of severe cannibalism.
4. For better skeletal integrity, the assessment of bone quality in pedigree birds housed in enriched cages is done by keel bone palpation or ultrasound measurement of the humerus. Both traits show similar heritabilities in the range of .15–.30 and can be included in a balanced selection approach for performance, quality and welfare traits.
5. The combination of performance testing and genome-wide DNA marker analysis is a promising tool to generate more progress for a balanced performance and behaviour profile. 相似文献