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21.
海南东寨港主要红树植物树高与胸径相关关系 总被引:1,自引:0,他引:1
采用相邻网格法在海南东寨港红树林保护区六个不同红树林群落中共布设六块有代表性的样地,测得454株海莲、129株无瓣海桑、112株海桑、198株秋茄树高与胸径,利用SAS9.0研究了树高(y)与胸径(x1)之间的相关关系。选出了适用于海莲树高预测的最佳回归方程为y=1.40334 0.49758x1 0.00399x12,适用于无瓣海桑、海桑树高预测的最佳回归方程分别为y/1=0.01732 1.10089/x1、y/1=0.01664 1.24603/x1,适用于秋茄树高预测的最佳回归方程为y=1.8165 x1 0.5230和lny=0.54906 0.54559lnx1。回归方程均达到极显著水平(P<0.01),其估计精度较高,均在93%以上,所建方程可用于计算各红树植物树高及其林分平均高。 相似文献
22.
An annual individual tree survival and growth model was developed for pure even-aged stands of maritime pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering thinning effects. The model is distance-independent and is based on a function for diameter growth, a function for height growth and a survival function. Two approaches are compared for modeling annual tree growth. The first approach directly estimates a future diameter or height using well-known growth functions formulated in difference form. The second approach estimates diameter or height using a function in differential form estimating the increment over a year period. In both approaches, the function parameters were related to tree and stand variables reflecting the competition status of the tree as well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling approaches. An iterative method was used to continuously update tree and stand attributes using a cut-off to convert the survival probability for a living or a dead tree. The individual tree diameter growth model and the survival probability model were fitted simultaneously using seemingly unrelated regression (SUR). Parameters of the height function were obtained separately as the number of observations for height was much lower than the number of observations for diameter, which may affect the statistical inference and the estimation of contemporaneous cross-equation error correlation inherent to the system of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the height growth functions. Additional statistics based in the log likelihood function and also in the survival probability were computed to evaluate the survival function. The second modeling approach, which integrates components of growth expansion and decline, performed slightly better than the first approach. A variable accounting for the thinning response that was tested proved to be significant for predicting diameter growth, even if the model already included competition-related explanatory variables, namely the basal area of trees larger than the subject tree. However, this thinning response factor was not significant for predicting height growth. 相似文献
23.
Thirty lichen and 25 bryophyte species have been recorded from the buttresses of Eucalyptus obliqua, the dominant tree in wet sclerophyll forest at the Warra Long-Term Ecological Research Site in southern Tasmania. The flora, characterised by four major associations, is very distinctive, containing a relatively high number of eucalypt specialists, particularly among the lichens. A general trend towards increasing species richness with increasing tree diameter is apparent and is attributed mainly to increasing habitat diversity on the buttresses. The increase in species occurs without the loss of pioneers; thus succession involves addition rather than replacement of species. The relationships between epiphytes, tree age and forest age are complicated by the periodic occurrence of fires in the forest. Nevertheless, potential oldgrowth indicators are identified and the possible effects of current silvicultural practices on the conservation of the species are discussed. 相似文献
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基于超声测距的定高树径测量仪的研究 总被引:2,自引:0,他引:2
为了便于对树木直径生长特征的分析,介绍了一种可代替测径围尺的专用于测量树木直径的测量仪。仪器采用超声波测距技术、条码识别技术及光电技术,可实现单株立木测量高度的确定和直径信息的识别,以及测量数据的自动读取和记录,提高了统计效率,方便了对数据的查询与分析。通过实验验证,仪器与围尺测量的相对误差在±1%以内,达到了预期设计指标。 相似文献
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R. Snchez-Andrs S. Snchez-Carrillo M. Benítez A. Snchez-Lpez 《Soil & Tillage Research》2006,90(1-2):50-62
This study describes the changes in height and diameter in Quercus ilex trees grown on agricultural land in a semi-arid Mediterranean climate, in response to different soil management practices: mechanical weeding (MW), chemical weeding (CHW) and no treatment (NT); and compares trees grown from 1-year-old saplings and from acorns. After 6 years, trees that had been mechanically weeded were largest; for trees grown from saplings the average height was 120 cm and diameter was 3.83 cm, for trees grown from acorns average height was 100 cm and diameter was 2.56 cm. Soil organic matter increased in all managed plots while phosphorus, nitrate, and water content oscillated between years. The no treatment plot had the highest values for nitrate and organic matter while the chemical weeding plot had the highest level of phosphorus. Annual mean on C/N ratios were higher in the mechanical weeding (12.6 ± 3.3) followed by the chemical weeding (12.0 ± 1.6). Also mechanical weeding treatment showed the lowest soil water content throughout the study. An old tillage-induced compaction zone appeared in all plots at a depth of 12.5–17.5 cm with mechanical weeding causing the greatest compaction. However, no relationships were found with tree heights, neither with spatial compaction zoning. All trees showed the same growth pattern, whether raised from saplings or acorns and irrespective of soil management system. The height and diameter of trees were linked to the sum of height and diameter ratios from previous years. Our study shows that soil management does influence tree growth rate. Mechanical weeding should be considered for afforestation of agricultural lands with Q. ilex in semiarid Mediterranean lands. 相似文献
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29.
采用层次分析法建立了高尔夫球场园林植物景观的评价系统。结果表明:深圳地区高尔夫球场植物群落树木的平均胸径与植物景观之间存在函数关系A=aD2+bD+c。当植物群落的平均胸径大约为22cm时,其景观的评价值最高,为91分。 相似文献
30.
《Scandinavian Journal of Forest Research》2012,27(4):369-376
Remote sensing techniques have proven successful for producing stem maps of forests in leaf-on condition from high-resolution imagery. This paper demonstrates how a mathematical model for the surface of a stem can be used to estimate the breast-height diameter of individual trees from aerial photographs to give information on basal area. The diameters are estimated by likelihood estimation from images of a forest in leaf-off condition where the stems and their shadows are visible. Applied to a homogeneous and monospecific oak ( Quercus robur L.) stand under standard silvicultural treatment in Denmark, the estimation was successful for 56 out of 60 trees. The root mean squared error on the diameter was 4.2 and 3.2 cm using three and five images, respectively. The key conclusion is that it is feasible to infer fairly accurate information about the diameters and three-dimensional positions of stems from aerial photographs. 相似文献