全文获取类型
收费全文 | 16527篇 |
免费 | 11篇 |
专业分类
林业 | 3629篇 |
农学 | 1299篇 |
基础科学 | 138篇 |
2771篇 | |
综合类 | 715篇 |
农作物 | 2100篇 |
水产渔业 | 1794篇 |
畜牧兽医 | 1106篇 |
园艺 | 1114篇 |
植物保护 | 1872篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 2747篇 |
2017年 | 2706篇 |
2016年 | 1185篇 |
2015年 | 67篇 |
2014年 | 17篇 |
2013年 | 15篇 |
2012年 | 799篇 |
2011年 | 2133篇 |
2010年 | 2108篇 |
2009年 | 1260篇 |
2008年 | 1321篇 |
2007年 | 1586篇 |
2006年 | 35篇 |
2005年 | 102篇 |
2004年 | 105篇 |
2003年 | 156篇 |
2002年 | 62篇 |
2001年 | 4篇 |
2000年 | 41篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 1篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Celia Herrero de Aza María Belén Turrión Valentín Pando Felipe Bravo 《Annals of Forest Science》2011,68(6):1067-1076
• Context
Understanding biological processes in forests is necessary to orientate ecosystem management towards potential C sequestration. To achieve this, information is required about changes in forest biomass C pools, including the stem components (bark, sapwood and heartwood). 相似文献992.
993.
Victoria González-Rodríguez Rafael Villar Raquel Casado Elena Suárez-Bonnet José Luis Quero Rafael M. Navarro-Cerrillo 《Annals of Forest Science》2011,68(7):1217-1232
Introduction
The great spatial and temporal heterogeneity of Mediterranean ecosystems can influence establishment success in woody species, whose natural regeneration occurs to a very small extent. In this work, the effect of the spatial pattern of environmental variables (light availability, soil moisture and herbaceous production) on seedling emergence, growth, survival and establishment success was examined by using a spatially explicit approach. 相似文献994.
Katri Luostarinen 《Annals of Forest Science》2011,68(5):985-992
Introduction
As the major resources of Siberian larch planted in Finland will be at a harvestable age in the near future, knowledge concerning wood and fibre properties of cultivated larches is needed. The properties affect both the character of pulp and paper, as well as properties important in the structural usage. 相似文献995.
Adrian Patrut Karl F. von Reden Robert Van Pelt Diana H. Mayne Daniel A. Lowy Dragos Margineanu 《Annals of Forest Science》2011,68(5):993-1003
• Introduction
For large trees without a continuous sequence of growth rings in their trunk, such as the African baobab (Adansonia digitata L.), the only accurate method for age determination is radiocarbon dating. As of today, this method was limited to dating samples collected from the remains of dead specimens. 相似文献996.
Mikko Vehmas Petteri Packalén Matti Maltamo Kalle Eerikäinen 《Annals of Forest Science》2011,68(4):825-835
• Introduction
Canopy gap dynamics in old-growth boreal forests is a result of tree mortality caused by insects, diseases, or meteorological phenomena. Canopy gaps improve the possibilities of natural regeneration, and concentrations of decomposed deadwood are often found in these natural openings, which provide specific habitats for many deadwood-dependent species and organisms. 相似文献997.
Objective
Knowledge of mechanisms determining plant persistence in range edges is essential because peripheral populations face increasing risk and they often maintain unique genotypes. 相似文献998.
Estimating balanced structure areas in multi-species forests on the Sierra Madre Occidental,Mexico 总被引:1,自引:0,他引:1
Christian Wehenkel José Javier Corral-Rivas José Ciro Hernández-Díaz Klaus von Gadow 《Annals of Forest Science》2011,68(2):385-394
• Introduction
This study presents a method for estimating the minimum area which exhibits a balanced diameter distribution, and the corresponding number of trees, for different tree species and forest types in the Santiago Papasquiaro region in the State of Durango, Mexico. The balanced structure area is defined as the minimum contiguous area that is required for sustainable management of a multi-sized selection forest. A multi-sized forest represents a balanced structure unit if the relationship between harvest and growth can be maintained, using a defined target diameter distribution and disregarding major natural disturbances. The study is based on 17,577 sample plots in uneven-aged forests, which are selectively harvested by local communities. 相似文献999.
Nitrogen-fixing activity in decomposing litter of three tree species at a watershed in eastern Japan
Takashi Yamanaka Keizo Hirai Shuhei Aizawa Shuichiro Yoshinaga Masamichi Takahashi 《Journal of Forest Research》2011,16(1):1-7
Nitrogen fixation during litter decomposition was studied for 34 months using litterbags containing newly fallen litter of
coniferous species Cryptomeria japonica and Pinus densiflora and that of deciduous species Quercus serrata. Litterbags were set in contact with the forest floor in a deciduous broad-leaved forest near the top of a slope and in a
C. japonica stand at the middle of the slope at a watershed in eastern Japan. Nitrogen-fixing activity, estimated by acetylene reduction
after 16 and 19 months of incubation, was 62.65–3.86 nmoles C2H4 h−1 g−1 DW in Cryptomeria litter, but only 1.07–0.09 in Pinus and 0.72–0.04 in Quercus. The rate of N increase in decomposing litter was highest in Cryptomeria. Fungal biomass in decomposing litter, estimated by ergosterol content, increased during the initial 16 months of incubation
in Cryptomeria and Quercus, and during the initial 19 months of incubation in Pinus. The litter decomposition rate was highest in Cryptomeria among the three species, due to increased N content and fungal biomass in Cryptomeria litter. Thus, N increase in decomposing Cryptomeria litter affects the subsequent N dynamics and decomposition pattern. 相似文献
1000.