全文获取类型
收费全文 | 108篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
林业 | 2篇 |
农学 | 1篇 |
基础科学 | 1篇 |
16篇 | |
综合类 | 12篇 |
农作物 | 4篇 |
水产渔业 | 5篇 |
畜牧兽医 | 72篇 |
园艺 | 1篇 |
植物保护 | 6篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2011年 | 1篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有120条查询结果,搜索用时 15 毫秒
81.
82.
83.
The basking shark Cetorhinus maximus is listed as Vulnerable (A1a,d, + 2d) worldwide, and Endangered (EN A1a,d) in the north-east Atlantic in the IUCN Red List. However, protection for this species is limited in European waters and varies spatially. Without information on the amount of time individuals spend in different areas, any potential risks to population levels from incidental capture, possible future exploitation and climate change will be difficult to assess. To quantify the annual space-use patterns within political-economic zones in the north-east Atlantic we used geolocation data from seven transmitter-tagged basking sharks tracked for 964 days (16,754 km). Basking sharks tagged within the UK protection zone off south-west England and north-west Scotland spent subsequently only about 22% (range, 2.4-47.7%) of time at liberty within this zone, and a further 30% in the UK fishing zone. Although only about 6% of time was spent in the territorial waters of Ireland and France, basking sharks remained in UK, Irish and French fishing and EEZ zones for over 71% of track time (range, 51.4-89.2%). Sharks did not occupy International waters away from the European shelf at any time. These results indicate basking sharks move between different economic zones and were not afforded statutory protection for the major part of the time (78%) they spent within preferred habitat on the European shelf. This demonstrates the limited capacity of the British protection zone for encompassing the greater part of shark space utilisation. Tracked basking sharks regularly crossed national zone boundaries suggesting that conservation measures for this species need to be framed on a European, rather than national, basis. This study highlights the need for better information about the movements and habitat use by marine animals if conservation strategies are to be truly effective. 相似文献
84.
C. Gaedke M. Witt M. Koene D. Berens von Rautenfeld P. Stadler 《Equine Veterinary Education》2013,25(10):517-523
The horse frequently shows idiopathic primary lymphoedema or secondary lymphoedema following trauma or infection to its limbs. Lymphoedema develops if the balance between the amount of lymphatic fluid and capacity of lymphatic transport is disturbed. Scintigraphy appears to be the only in vivo technique to evaluate lymphatic transport capacity. The aim of this study was to develop an evaluation technique to determine the lymph flow in the hindlimb of the horse. This technique might show potential to extend the possibilities for investigating disorders of the lymphatic system in equine extremities. 相似文献
85.
Abstract Whereas cultivation had a detrimental effect on the production of Eragrostis curvula established in broadcast stands, both manuring and mulching had beneficial effects. This effect may be ascribed largely to better moisture conditions achieved with mulching although, at high rates of manuring, additional benefits could also be ascribed to the circulation of nutrients. The cost effectiveness of manuring is, however, doubtful. Although manuring improves the response to inorganic fertilization it will not reduce the need for such fertilization. The application of manure at 20 t ha‐1 on large areas would be preferable to 40 t ha‐1 on smaller areas, but this can only be recommended where costs are debited to feedlot waste product disposal. 相似文献
86.
87.
Susanne Frank Christine Fürst Anke Witt Lars Koschke Franz Makeschin 《Landscape Ecology》2014,29(8):1377-1391
In this article we demonstrate how to integrate the ecosystem services concept into regional planning using the example of a case study in Saxony, Germany. We analysed how the reduction of water erosion as a regulating service impacts six other ecosystem services. Ecological integrity, provisioning services (provision of food and fibre, provision of biomass), regulating services (soil erosion protection, drought-risk regulation, flood regulation), and the cultural service landscape aesthetics are taken into account. Using a decision support software, we found that the greening of preferential discharge paths can reduce water erosion by 2–7 %. The introduction of hedgerows and the change in the soil management system from tillage to no-till practices revealed a reduction in the total soil loss by 33 and 89 %, respectively. A combination of the three erosion control measures—greening, hedgerows, and no-till management—reduced the soil loss most efficiently by 92 %. We found synergies between the measures for reducing erosion and the provision of ecological integrity, of regulating and cultural ecosystem services. In contrast, the impact on provisioning services was slightly negative. For the land use planning in the case study region we recommend therefore a combination of greening, hedges, and management change. We found that the applied integrated ecosystem services assessment approach, in combination with stakeholder involvement in the scenario development, helped communicating cross-sectoral effects of different management strategies in a comprehensive way and therefore supports regional planning. 相似文献
88.
89.
Dynamics of soil microbial biomass and nitrogen availability in a flooded rice soil amended with different C and N sources 总被引:4,自引:0,他引:4
A greenhouse experiment was conducted to compare effects of different C and N sources applied to a flooded soil on soil microbial
biomass (SMB) C and N, extractable soil organic N (NORG), and NH4
+-N in relation to plant N accumulation of rice (Oryza sativa L.). In addition to a control without inputs (CON), four treatments were imposed receiving: prilled urea (PU), rice straw
(RS), RS and PU (RS+PU), or Sesbania rostrata as green manure (SES). Treatments were arranged according to a completely randomized design with four replicates and further
consisted of pots with and without transplanted rice. While plant effects on the SMB were relatively small, the application
of organic N sources resulted in a rapid increase in SMB until 10 days after transplanting (DAT) followed by a gradual decline
until 73 DAT. Plant N accumulation data in these treatments clearly indicated that the SMB underwent a transition from a sink
to a source of plant-available soil N during the period of crop growth. Seasonal variation of the SMB was small in treatments
without amendment of organic material (CON, PU) presumably due to a lack of available C as energy source. Extractable NORG was significantly affected by soil planting status and organic N source amendment, but represented only a small N pool with
little temporal variation despite an assumed rapid turnover. Among the three treatments receiving the same amount of N from
different sources, the recovery efficiency of applied N was 58% for PU and 28% for both RS+PU and SES treatments at 73 DAT.
The N uptake of rice, however, was not driven by N availability alone, as most evident in the RS+PU treatment. We assume that
root physiological functions were impeded after application of organic N sources.
Received: 1 June 1999 相似文献
90.