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21.
Andrzej Bobiec Haico van der Burgt Kim Meijer Casper Zuyderduyn Jos Haga Bastiaan Vlaanderen 《Forest Ecology and Management》2000,130(1-3)
The Bia
owie
a Primeval Forest, Poland, is the only forest area in temperate Europe where large tracts of natural forest communities have been conserved. The concept of silvatic mosaic [Oldeman, R.A.A., 1990. Forests: Elements of Silvology. Springer, Berlin] was applied in order to characterise the structure of stands representing oak–lime–hornbeam forest in both, the restricted area of Bia
owie
a National Park (BNP) and the commercial forests (CF), as well as to indicate a holistic approach towards protection and restoration of natural areas.Six developmental phases of stands were distinguished and defined: regeneration, young, pole, late pole, optimal, and terminal. Compositional and structural differences between the first five phases were also evaluated and visualised. Moreover, the considerable differences between analogous phases in BNP and CF were found. The uniform stand patches were mapped into two plots in BNP (25 ha each) and two in CF (25 and 20 ha), with a resolution of 10 m× 10 m pixels.The mosaic composition of natural communities indicates close-to-the equilibrium stage: the biostatic optimal phase occupies 33–40% of the area, while aggradational younger phases share nearly the same portion of the area as the senescent phase does. Although small, 0.01–0.04 ha eco-units dominate in BNP, there is a considerable portion of intermediate and large patches, indicating a complex character of factors responsible for the mosaic structure of natural stands in BNP. Both, composition and texture analyses indicate that the area of 25 ha is close to the minimum structure area specific for the communities studied.The comparison of natural and managed stands revealed large deficits of the optimal phase (only 19%) and a total absence of the terminal one in the managed area (20–35% in natural forest). Also the mosaic texture of CF plots was simplified because of standardisation of the management unit size. The modification of developmental phases, mosaic composition, and structure must lead to changes in the dynamics of the entire community. The present study demonstrates that the natural forest should be considered as a dynamic supersystem, covering a sufficient area to allow the developmental phases to perform in correct proportions. Because of differences in the durability of various phases, the natural cycle of forest development has an asynchronous and highly unpredictable character. Indeed, the applicability of multipurpose forestry rules as a tool of nature conservation has been questioned. An absolute ban on cutting in the remaining old-growth stands should be a basic rule for the restoration management. 相似文献
22.
Recent research in western North America suggests that open forage areas are a greater limiting factor to mule deer abundance than closed conifer forests. However, much of this work was conducted in ecosystems prone to fire and low snow depths compared to the limits of mule deer range such as the Columbia Mountains, British Columbia, where snow is deep and fires are rare. We used snow track surveys as a measure of habitat use and fecal nitrogen as an index of dietary quality to compare the relative value to mule deer of open deciduous canopies to closed coniferous canopies in a wet ecosystem with deep snow and few fires. Deciduous canopies contain higher levels of understory forage compared to dense coniferous canopies, which are better at intercepting snow. We also evaluated food habits across landscapes with contrasting forest canopies. Results corroborated previous work in that foraging areas such as deciduous stands were strongly selected by deer, despite deeper snow relative to closed coniferous stands. Deer consumed fewer understory shrubs in coniferous-dominated stands, suggesting lower nutritional intake in these stands. Finally, deer appeared to derive a nutritional benefit in landscapes that had a higher proportion of open deciduous canopies, as indexed by fecal nitrogen. However, not all open canopy stands were of equal value to deer – deciduous-dominated stands were selected, whereas clearcuts were avoided. Similarly, not all closed coniferous stands were equally selected: cedar–hemlock stands were avoided whereas Douglas-fir stands were selected and indeed contained the highest proportion of deer tracks. We suggest that winter foraging areas have been underrepresented in management policy in British Columbia, but that snow-interception cover provided by coniferous stands still plays a role in winter deer ecology in deep-snow ecosystems. 相似文献
23.
Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech? 总被引:3,自引:0,他引:3
Andreas Mlder Markus Bernhardt-Rmermann Wolfgang Schmidt 《Forest Ecology and Management》2008,256(3):272
Where natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation. 相似文献
24.
杜鹃花种子细小且发芽率低,为探索有效促进种子萌发的方法,选用杜鹃花主栽品种春鹃紫蝴蝶自交种子为材料,通过蒸馏水浸种、GA3浸种和无菌播种添加NAA、KT、ZT及GA3的处理方式,比较不同处理对杜鹃花自交种子萌发时间、发芽率等指标的影响。结果表明,蒸馏水浸种处理以24 h浸种的效果最佳,发芽率达43%;无菌播种结合2.0 mg·L-1 GA3+0.05 mg·L-1 NAA处理的效果最佳,发芽率达75%;GA3浸种以1 600 mg·L-1 GA3处理24 h的效果最佳,发芽率可达82%,是对照组的1.82倍。以GA3浸种法处理杜鹃花2个杂交组合的杂交种子,发现其各项发芽指标均优于对照,其中29号杂交种子的最适GA3处理为1 200 mg·L-1浸种24 h,发芽率达96%;59号杂交种子最适GA3处理为1 600 mg·L-1浸种24 h,发芽率可达95%,二者发芽率分别比对照提高20%和71%,萌发时间分别提早2和8 d。因此,适宜浓度尤其是高浓度GA3浸种处理能有效促进杜鹃花自交和杂交种子的萌发。 相似文献
25.
落叶栎林对森林火灾的影响分析 总被引:4,自引:1,他引:4
根据落叶栎林的特点,着重分析了落叶栎林与森林火灾的关系,结果表明,落叶栎林不仅存在着较强的潜在地表火,而且存在着潜在树冠火危险,是栎林火灾的最大隐患之一。同时还简要分析了栎类由于长期的自然适应而对森林火灾产生的抗火机制。 相似文献
26.
27.
Bryophyte species richness on boulders: relationship to area, habitat diversity and canopy tree species 总被引:1,自引:0,他引:1
Bryophytes growing on siliceous boulders (diameter 50-200 cm) were studied in two forests in east-central Sweden to investigate the influence of different canopy tree species on the bryophyte species richness. Granite boulders lying below crowns of Ulmus glabra (elm), Fraxinus excelsior (ash), Acer platanoides (maple), Quercus robur (oak), Betula pendula (birch), and Picea abies (Norway spruce) were studied in two mixed stands. Both boulder area and within-boulder habitat diversity were positively related to species richness. Boulders below the base-rich deciduous trees F. excelsior, U. glabra and A. platanoides held roughly twice as many species as those below P. abies, with Q. robur and B. pendula as intermediates. The rank order among trees was as expected from bark pH and litter decomposability in the literature. We also used sample plots to investigate species richness at a smaller scale. Within plots, intermediate levels of litter, inclination and exposed rock promoted species richness, and also the covering tree species had an effect. Individual plots were on average not more species-rich on large boulders than on small ones. This leads us to conclude that population extinctions on the plot-level, and re-colonisations from other parts of the boulder, are less important for species richness than within-boulder habitat diversity. Since species richness was lower under P. abies it is important to favour a diversity of tree species and to include base-rich deciduous trees in otherwise homogeneous Picea forests. 相似文献
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