全文获取类型
收费全文 | 85篇 |
免费 | 5篇 |
国内免费 | 9篇 |
专业分类
林业 | 30篇 |
农学 | 7篇 |
基础科学 | 2篇 |
19篇 | |
综合类 | 21篇 |
农作物 | 11篇 |
水产渔业 | 1篇 |
畜牧兽医 | 5篇 |
植物保护 | 3篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 1篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
1993年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 765 毫秒
1.
2.
Anna Lena Mueller Christian A. Berger Siegfried Schittenhelm Burkhard Stever-Schoo Jens Dauber 《Journal of Agronomy and Crop Science》2020,206(5):529-537
The perennial cup plant (Silphium perfoliatum L.) is considered as an alternative feedstock to maize for biogas plants. Due to its ecological advantages of an extensive management and function as food resource for pollinators, it can be grown in Ecological Focus Areas (EFAs) since 2018. However, studies at the Julius Kühn-Institute in Braunschweig (Germany) showed that the assumed advantage of the cup plant of a high drought tolerance could not be confirmed regarding aspects of crop production and yield. We complemented this experiment by assessing how different soil moisture conditions affect the production of floral resources and insect visitation. In 2014, we sampled three irrigated and three rainfed plots of the cup plant. We quantified the nectar volume and sugar mass per inflorescence, the number of inflorescences per plant and calculated the total nectar sugar production. We further counted insect visitation on the inflorescences. Due to reduced numbers of inflorescences per plant and an earlier harvest, the estimated nectar sugar production was 58 kg/ha regarding irrigated and 20 kg/ha regarding rainfed plots. Honeybee visitation per inflorescence was about twice as high in the irrigated plots. Furthermore, the early harvest is a disadvantage for wild pollinators with a late activity period. 相似文献
3.
4.
现有生物质能转换利用技术综合评价 总被引:1,自引:0,他引:1
本文介绍了生物质能转换利用的方法,对现有生物质能转换技术进行了比较,运用层次分析法从技术先进性、经济可行性和环境安全性三个方面对现有生物质能转换利用技术进行了综合评价,提出了生物质能转换利用技术的优先发展顺序和发展方向,为我国生物质能转换利用技术的发展和应用提供参考依据. 相似文献
5.
6.
林木生物质能源开发和利用 总被引:13,自引:0,他引:13
林木生物质能源作为生物质能源的一个重要分支,清洁性和可循环再生利用等特点使其在新世纪具有广阔发展前景。本文结合国外做法介绍了我国木质能源开发和利用现状,阐述了林木质能源开发和利用方式,并对发展前景和对策作了初步探讨。 相似文献
7.
木材科学与技术研究新进展 总被引:1,自引:0,他引:1
吴义强 《中南林业科技大学学报(自然科学版)》2021,(1)
木材作为世界四大基础材料中(钢铁、水泥、塑料、木材)唯一的可再生资源,广泛应用于家具、建筑、能源、新材料等领域,与人们的生活息息相关,已成为国民经济重要支柱产业。从木材微观分子生物学到宏观木结构,再到新型木质纳米材料进行全面阐释,对于木材科学与技术领域的基础理论研究和重大核心技术突破具有重要指导意义。木材科学与技术已发展为综合性的交叉学科,资源、环境和科学技术的发展,使得木材科学与技术领域的基础理论研究和关键技术取得了一系列的重大突破。笔者从微观的细胞分子层面到宏观的木结构和木建筑,从木材构造与材性、木材水分及干燥、木材保护与改良、木材重组与复合、木制品与木结构、木材解离与组装、木材解构及转化等方面,概述了木材科学与技术的经典理论,重点总结分析了近二十年来木材科学与技术领域取得的系列新进展,概括木材及其衍生材料在新型先进纳米复合材料领域的应用,并展望了木材科学与技术领域未来的研究热点和发展方向,以期为我国林产工业,特别是木材加工产业的科技进步和产业结构调整与升级提供理论和技术支撑。 相似文献
8.
Biogas production from grassland biomass harvested during landscape management may help to maintain species‐rich grassland biotopes, but extensive management and late harvests often result in low‐quality biomass. Biogas production from the vegetation of Alopecuretum pratensis, Molinietum caeruleae and Caricetum gracilis, three typical grassland biotopes in north German nature reserves, was investigated in relation to harvest date. In addition, the A. pratensis vegetation was investigated for ensiling and the application of bacterial silage additives. Results indicate that biogas production might be a reasonable utilization pathway for grassland biomass from landscape management if the first cut occurs up to late summer. Methane yields of grassland biomass decreased substantially with later harvest, from up to 309 lN kg?1 organic dry matter (ODM) in May to below 60 lN kg?1 ODM in February, in correlation with increasing crude fibre contents. Caricetum gracilis vegetation was the least suitable feedstock for biogas production. It showed a rapid decline in methane yields with later harvest and 25% lower methane yields compared with other types of grassland vegetation. Application of silage additives is recommended for adequate preservation of grassland biomass from landscape management by ensiling. Addition of homofermentative lactic acid bacteria improved acidification during ensiling if sufficient fermentable sugar was available. The use of inoculant and molasses enhanced methane yields by 3–55%. Additional carbohydrate source is necessary to ensure proper ensilage when grasses are harvested after late autumn. 相似文献
9.
Changes in livestock production systems have led to land‐use changes and abandonment, especially of semi‐natural grassland in agriculturally less favoured regions. The generation of energy from biomass of extensive, high‐diversity grasslands can be an alternative to their abandonment, and anaerobic digestion is one possible method for converting grassland biomass into energy. However, little is known about the effects of species richness (SR) and functional groups on chemical constituents relevant for anaerobic digestion and the resulting energy potential. In this study, changes in the herbage chemical constituents that are relevant for forage quality were studied along a well‐defined diversity gradient (one to sixty species) and across different combinations of functional groups (legumes, small herbs, tall herbs and grasses). Substrate‐specific methane yield (CH4 sub) was estimated through the concentrations of forage‐quality parameters such as crude fibre (CF), crude protein (CP), crude lipid, nitrogen‐free extract and their documented digestibility values, as well as the respective methane yields. Results show that with increasing SR, the CF increased and CP decreased, even though these effects could not be fully disentangled from the presence of grasses. These trends led to a negative effect of SR on CH4 sub, while the area‐specific methane yield (CH4 area = CH4 sub × biomass yield) increased due to a strong increase in biomass with increasing SR. The CH4 sub was increased when legumes were present, and it declined with the presence of grasses. Generally, CH4 sub and CH4 area varied between functional‐group monocultures and all functional‐group mixtures. 相似文献
10.
Heljä-Sisko Helmisaari Lilli Kaarakka Bengt A. Olsson 《Scandinavian Journal of Forest Research》2014,29(4):312-322
The review gives an overview of the increased utilization of forest biomass for energy. The emphasis is on Nordic countries, especially on Sweden and Finland with large biomass potentials and a high share of renewable energy in gross final energy consumption. The utilization and potential of forest chip sources such as logging residues, small-size tree stems and stumps that are normally not harvested in conventional harvesting are described. Environmental potential and impacts that may reduce the utilization of forest biomass are discussed based on recent publications. Finally, the review summarizes the future developments based on their relationship to policies, certifications and guidelines and forest owners' decisions. 相似文献