首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   16429篇
  免费   4篇
林业   3624篇
农学   1295篇
基础科学   137篇
  2732篇
综合类   708篇
农作物   2097篇
水产渔业   1789篇
畜牧兽医   1079篇
园艺   1110篇
植物保护   1862篇
  2022年   2篇
  2021年   2篇
  2019年   1篇
  2018年   2744篇
  2017年   2702篇
  2016年   1183篇
  2015年   72篇
  2014年   16篇
  2013年   11篇
  2012年   793篇
  2011年   2122篇
  2010年   2102篇
  2009年   1257篇
  2008年   1313篇
  2007年   1575篇
  2006年   31篇
  2005年   96篇
  2004年   103篇
  2003年   152篇
  2002年   59篇
  2001年   5篇
  2000年   40篇
  1999年   1篇
  1998年   1篇
  1995年   1篇
  1993年   12篇
  1992年   7篇
  1990年   1篇
  1989年   6篇
  1988年   11篇
  1987年   1篇
  1977年   4篇
  1972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 430 毫秒
771.

Introduction   

Forest fuel management in the context of fire prevention generally induces heterogeneous spatial patterns of vegetation. However, the impact of the canopy structure on both wind flows and fire behavior is not well understood.  相似文献   
772.
773.

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   
774.

• Introduction   

Millions of hectares of Quercus ilex forests dominate disturbed landscapes in the western part of the Mediterranean basin. Although these forests are very widespread, little is known about the composition and structure of their associated ectomycorrhizal fungal communities.  相似文献   
775.

• Introduction   

Multi-varietal forestry (MVF) is the deployment of tested tree varieties in plantation forestry. Computer simulation using POPSIM Simulator identified optimal combination of numbers of families, varieties per family and ramets per variety (nf, nc and nr, respectively) yielding the largest genetic gain for a specific status number (NS) in a varietal test (VT) intended for MVF of conifers.  相似文献   
776.

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   
777.
778.

• Introduction   

Various processes contribute to shaping the local assemblage of species in hyperdiverse tropical forest. The relative contribution of environmental factors and dispersal limitation in determining the spatial distribution of saplings at local scale is unclear.  相似文献   
779.

• 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   
780.

• Introduction   

Stem taper equations have been widely used for volume estimation to varied top diameter limits or for biomass calculations. However, their main drawback is that specific calibration is often necessary for each species or clone, and accounting for genetic and environmental effects is often a challenge.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号