全文获取类型
收费全文 | 179篇 |
免费 | 17篇 |
专业分类
林业 | 27篇 |
农学 | 8篇 |
基础科学 | 1篇 |
37篇 | |
综合类 | 22篇 |
农作物 | 8篇 |
水产渔业 | 9篇 |
畜牧兽医 | 52篇 |
园艺 | 9篇 |
植物保护 | 23篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 5篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 2篇 |
2012年 | 16篇 |
2011年 | 12篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 15篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 218 毫秒
111.
112.
Influence of stand,site and meteorological variables on the maximum leaf area index of beech,oak and Scots pine 总被引:1,自引:0,他引:1
Raphael Bequet Vincent Kint Matteo Campioli Dries Vansteenkiste Bart Muys Reinhart Ceulemans 《European Journal of Forest Research》2012,131(2):283-295
Different multiple linear regression models of maximum leaf area index (LAImax) based on stand characteristics, site quality, meteorological variables and their combinations were constructed and cross-validated
for three economically important tree species in Flanders, Belgium: European beech (Fagus sylvatica L.), Pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.). The models were successfully tested on similar datasets of experimental sites across Europe. For each species, ten homogeneous
and mature stands were selected, covering the species’ entire stand productivity range based on an a priori site index classification.
LAImax was derived from measurements of leaf area index (LAI) made by means of hemispherical digital photography over the whole
growing season (mid-April till end October 2008). Species-specific models of LAImax for beech and oak were mostly driven by management practice affecting stand characteristics and tree growth. Tree density
and dominant height were main predictors for beech, while stand age and tree-ring growth were important in the oak models.
Scots pine models were more affected by site quality and meteorological variables. The beech meteorological model showed very
good agreement with LAI at several European sites. Scots pine’s stand model predicted well LAI across Europe. Since the species-specific
models did not share common predictors, generic models of LAImax were developed for the 30 studied sites. Dominant height was found to be the best predictor in those generic models. As expected,
they showed a lower predictive performance than species-specific ones. 相似文献
113.
114.
Climate Change Vulnerability Assessment (VA) tools for forest ecosystems and forest-dependent communities are important for making decisions and understanding the impact of climate change on both social and natural systems. However, the tools are poorly coordinated, making it difficult for policymakers to carry out VAs properly. The aim of this study was to analyze VA literature worldwide to find representative case studies in terms of methods and tools applied and which have been successful in performing VAs on forests and forest-dependent communities. All successful VA studies analyzed had common characteristics such as significant funding, data availability and technical capacity. An additional characteristic was the development of an integrated approach that considered the vulnerability of both ecosystems and communities by combining qualitative and quantitative methods. Community members and relevant stakeholders were significantly involved in a participatory process that concluded with the identification of adaptation measures. The case studies also revealed how policymakers need to choose suitable methods and tools to undertake efficient assessment of vulnerabilities. They need to consider several aspects of the VA process such as subject matter, availability of resources, time and scale. 相似文献
115.
Buscaroli Enrico Sciubba Luigi Falsone Gloria Cavani Luciano Brecchia Matteo Argese Emanuele Marzadori Claudio Pourrut Bertrand Braschi Ilaria 《Journal of Soils and Sediments》2019,19(7):3098-3107
Journal of Soils and Sediments - Canal dredging and shaping produce considerable amounts of sediments whose reuse on- and off-site depends on their pollution level. This study explores the... 相似文献
116.
Martini Mina Altomonte Iolanda Sommer Matteo Federico Gili Claudia Biancani Barbara Licitra Rosario Salari Federica 《Veterinary research communications》2022,46(2):577-583
Veterinary Research Communications - Research data on milk composition in cetaceans are scattered and fragmentary. This paper analyses the gross and mineral composition, the fatty acids profile and... 相似文献
117.
118.
119.
Garbarino Matteo Morresi Donato Urbinati Carlo Malandra Francesco Motta Renzo Sibona Emanuele Marco Vitali Alessandro Weisberg Peter J. 《Landscape Ecology》2020,35(12):2679-2694
Landscape Ecology - Land use legacies of human activities and recent post-abandonment forest expansion have extensively modified numerous forest landscapes throughout the European mountain ranges.... 相似文献
120.
提出了一种基于方格网法测算树冠体积的方法。研究利用免棱镜全站仪获取树冠点云数据,建立树冠表面特征点的坐标方格网,根据方格网法计算土方量的原理来求算树冠体积,通过传统经典模型人工方法、三维激光量测法与本文算法,分别计算实验区域研究对象的体积,将结果进行对比分析,本研究提出的算法平均相对误差为4.13%,平均准确度为95.97%,且在置信度0.05下树冠体积的计算值与实测值之间的差异性为不显著,结果完全满足计算精度,其计算耗时只有传统人工量测法的1/3,成本为三维激光扫描的2%,降低了成本且提高了效率。 相似文献