全文获取类型
收费全文 | 204篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
林业 | 37篇 |
农学 | 13篇 |
33篇 | |
综合类 | 44篇 |
农作物 | 12篇 |
水产渔业 | 15篇 |
畜牧兽医 | 22篇 |
园艺 | 23篇 |
植物保护 | 23篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 17篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 13篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
排序方式: 共有222条查询结果,搜索用时 15 毫秒
181.
- 1. The provision of Canadian and US hard, enforceable, law to authorize rapid response management of nonindigenous aquatic species originating from aquaculture, live fish sales, bait fish, and the pet trade was analysed at the provincial/state levels of government for the Atlantic, Laurentian Great Lakes, and Pacific regions of North America.
- 2. No federal legal capacity for rapid response management exists in either country. US state legislation is generally better developed than Canadian provincial laws to manage the exotic fish trade. However, much discrepancy exists among provincial and state law regarding provisions to restrict or prohibit potentially harmful species. Aquaculture and baitfish use is generally better regulated than live fish markets and the pet fish trade in both countries. Only the state of Maine has laws authorizing rapid‐response management to control escaped exotic fish.
- 3. Most species of nonindigenous fish arise from the aquarium, pet, and baitfish trades, and development of improved legislation containing provisions for rapid response management of escapees is warranted in all states and provinces.
- 4. It is recommended that Canada amends the Fisheries Act to create the appropriate enabling legislation to monitor, assess risk, and deploy rapid response management of nonindigenous aquatic species, including fish that enter federal fresh and sea waters. Two recently‐introduced US Bills, S. 725 and H.R. 1350, with their explicit measures for early detection and fast action response, could, if passed into law, create provisions to control introduced nuisance species throughout North American waters. They would also create precedents for states and provinces that have most jurisdiction over aquaculture and trade in exotic fish to amend and align their laws in a complementary manner.
182.
183.
Integrating socio‐economic and biophysical models: revision of a land‐use allocation model
下载免费PDF全文
![点击此处可从《Soil Use and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Y. Du T. Liu T. Huffman B. McConkey S. Toure F. Feng M. Green J. Liu H. Liu 《Soil Use and Management》2015,31(3):417-420
Integration of large‐area, economically driven macro‐models and small‐area, biophysically based models in the Canadian agricultural sector was described recently in the development of a land‐use allocation model (LUAM). We have since developed and integrated an improved methodology for allocating crop area changes generated for large areas by the Canadian Regional Agricultural Model (CRAM) to much smaller Soil Landscapes of Canada (SLC) polygons. Validation of outputs showed considerable improvement. The new coefficients of determination (R2) between simulated and actual data, with previous values in brackets, were 0.69 for fodder corn (0.54), 0.88 for wheat (0.62), 0.77 for hay (0.26), 0.54 for alfalfa (not previously reported), 0.88 for soya bean (0.26) and 0.86 for grain corn (0.22). The best result was obtained for soya bean, with a normalized root mean square error (NRMSE) of 0.31%, and the poorest for alfalfa, with NRMSE = 17.34%. 相似文献
184.
森林认证已成为改善森林管理的一种重要的治理机制。文章介绍了加拿大森林认证的现状,分析了加拿大推进森林认证的措施,并借鉴加拿大推进森林认证的经验,提出我国推进森林认证的对策。 相似文献
185.
186.
187.
加拿大森林资源丰富,长期以来坚持以森林可持续利用的理论指导森林经营,重视林业科学技术,坚持林业科研与生产紧密结合。借鉴其经验,建议加快毕节试验区森林分类经营,加大天然林资源保护和退耕还林工程力度,发展优质高效的速生丰产用材林。 相似文献
188.
Shahrokh Khanizadeh 《Euphytica》1994,77(1-2):45-49
Summary Canada imports more than 21,000 tonnes of strawberries annually, of which approximately 5,000–6,000 tonnes are frozen berries
used for processing at a cost of more than $ 10 million. These could be replaced by Canadian grown fruit if improved cultivars,
and suitable for mechanical harvesting, processing and fresh market adapted to canadian climatic conditions would be available.
For many years producers in Quebec have grown the cultivar ‘Redcoat’ (Sparkle × Valentine) released in 1957 by Agriculture
Canada, Ottawa. Redcoat is now rapidly being replaced by ‘Kent’, (`K68-58 × Raritan’) released in 1981 by Agriculture Canada,
Kentville. Despite Quebec's preeminant position in Canada as a strawberry producing region, no strawberry cultivars have ever
been bred specific for Quebec conditions. In 1982 a breeding program was initiated at Agriculture Canada St-Jean. This program
was terminated in 1986 without any material having been tested sufficiently for release. In 1987 a joint project between McGill
University and Agriculture Canada initiated to continue the breeding program and develop cultivars particularly suitable for
mechanical harvesting and processing, resistant to disease and adapted to local conditions.
Agriculture Canada, St-Jean-sur-Richelieu, Contribution No. 335/93.12.02R 相似文献
189.
190.
为探索冀东冷棚三种三收高效栽培模式,引进番茄保粉1号、1857、西芹文图拉新品种,与当地传统品种番茄L402、L400、芹菜玻璃脆对比.结果表明:新品种具有优良的商品品质和价格优势.改进当地普通大冷棚,设计出结构合理、投资少、效益高的无立柱、无后墙型加苫冷棚,生产出的番茄、芹菜春提前,秋延后,补充市场淡季,延长蔬菜供应期.三种三收模式单棚产值(400 m2)达11 156.30元,比普通大冷棚两种两收模式单棚总产值增加4 245.90元,此模式具有产量高、品质优、效益高、推广前景广阔等特点. 相似文献