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11.
Human development of freshwater ecosystems has lead to drastic changes in freshwater fish faunas, including the loss of many native species and the gain of non-natives. Typically conservation ecologists view these two opposing forces as contributing to biological homogenization, and consider homogenization as one of the principle negative consequences of urbanization. However, homogenization is only one outcome out of many that can result from the loss and gain of species. In particular, it is possible for invasions and extinctions to lead to differentiation; a process whereby two (or more) regions become less similar to one another through time. Using the freshwater fishes of California, we show that urbanization is highly positively correlated to both the endangerment of native fish and the invasion of non-native fish within watersheds. Despite this, the fish faunas of California’s watersheds have differentiated from one another through time. Furthermore, the degree of differentiation is positively correlated with measures of urbanization, which is contrary to expectation. We suggest that this result reflects: (1) the haphazard manner in which non-native fishes have been introduced into California watersheds, (2) the difficulty that both native and non-native fishes have in expanding their geographical ranges, and (3) the continued presence of vestiges of formerly distinct regional faunas. This pattern of differentiation among watersheds is likely a matter of scale, as previous work on freshwater fishes has demonstrated homogenization at both larger and smaller spatial scales. In addition the observed pattern is probably a short-term (temporal) phenomena and will disappear with continued invasion and extinction. We suggest that similar patterns may occur for other taxa that have limited natural dispersal abilities and that are idiosyncratically released as non-natives via human activities (e.g. herptiles). 相似文献
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L. Miranda-Aragón E.J. Trevi o-Garza J. Jiménez-Pérez O.A. Aguirre-Calderón M.A. González-Tagle M. Pompa-García C.A. Aguirre-Salado 《林业研究》2012,23(3):345-354
Determining underlying factors that foster deforestation and delineating forest areas by levels of susceptibility are of the main challenges when defining policies for forest management and planning at regional scale. The susceptibility to deforestation of remaining forest ecosystems (shrubland, temperate forest and rainforest) was conducted in the state of San Luis Potosi, located in north central Mexico. Spatial analysis techniques were used to detect the deforested areas in the study area during 1993-2007. Logistic regression was used to relate explanatory variables (such as social, investment, forest production, biophysical and proximity factors) with susceptibility to deforestation to construct predictive models with two focuses: general and by biogeographical zone.In all models, deforestation has positive correlation with distance to rainfed agriculture, and negative correlation with slope, distance to roads and distance to towns. Other variables were significant in some cases, but in others they had dual relationships, which varied in each biogeographical zone. The results show that the remaining rainforest of Huastecaregion is highly susceptible to deforestation. Both approaches show that more than 70% of the current rainforest area has high and very high levels of susceptibility to deforestation. The values represent a serious concern with global warming whether tree carbon is released to atmosphere. However, after some considerations, encouraging forest environmental services appears to be the best alternative to achieve sustainable forest management. 相似文献
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《African Zoology》2013,48(2):302-303
Sociality confers many benefits to gregarious animals, but group-living does not come without associated costs. Social living can cause anxiety, which if prolonged can lead to stress. We investigate correlates of anxiety and stress among wild adult male olive baboons (Papio hamadryas anubis) in Gashaka-Gumti National Park, Nigeria, and present the first examination of these correlates for male baboons living in forested environments. We used rates of self-directed behaviours (SDB) to quantify anxiety, and faecal glucocorticoid (FGC) concentrations to quantify physiological stress. We first examined the relationship between SDB rates and FGC concentrations, and then examined each measure in relation to a range of variables previously linked to anxiety or stress. We found that SDB rates and FGC concentrations were not correlated with each other, nor were they related to any measure of grooming or receiving aggression. SDB rates were negatively correlated with time spent with an adult female as nearest neighbour, but were unrelated to time with another adult male as closest conspecific. FGC concentrations were unrelated to time with adult nearest neighbours of either sex. Our results add to the growing body of literature examining the psychological and physiological costs of social living among wild primates. 相似文献
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随着时代的变迁和世界局势的发展,创新创业逐渐成为了当前的发展新势态和经济发展新引擎。在此背景下,饲料行业需要与时俱进,深入实施创新,驱动发展,促进企业结构调整,优化产能和经营,以实现可持续发展的目的。本文紧密结合“双创”的深刻涵义,就饲料企业经营主体的经营现状及面临的问题展开分析,对企业的多维经营进行探索与研究,提出了一系列具体的对策与思路。 相似文献
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Susan O. Sande Robin M. Crewe Suresh K. Raina Susan W. Nicolson Ian Gordon 《Biological conservation》2009,142(11):2703-2709
Although tropical forest conservation is a top priority for human and environmental health, deforestation persists, mainly because of food and economic needs. No community will totally give up economic activities for the sake of ecological integrity, unless it is given alternative economic activities from which to draw its livelihood. Beekeeping in the forest buffer zone instead of traditional destructive honey-harvesting from forest trees is one such option at Arabuko Sokoke Forest (ASF) in Kenya. ASF is a dry coastal forest which is home to endangered and threatened fauna and is a hotspot considered a priority for conservation. In order to find out whether honey quantity and quality differed with distance from the forest, we studied honey yield per harvest (kg) and obtained samples from hives placed at varying distances from ASF in two successive years. Honey yield increased with proximity to the forest. Indeed the yield almost doubled in hives placed less than 1 km from the forest compared to those placed more than 3 km from the forest. All the honey samples met internationally required quality standards, although sugar levels were at the lower limit. This study demonstrates that the conservation of tropical forest ecosystems can have real local economic benefits. The documentation of the services provided by nearby natural areas should help make conservation of these areas a priority, even for the local communities. 相似文献
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Colonisation of native and exotic conifers by indigenous bark beetles (Coleoptera: Scolytinae) in France 总被引:1,自引:0,他引:1
Coralie Bertheau Aurlien Salle Jean-Pierre Rossi Stphanie Bankhead-dronnet Xavier Pineau Graldine Roux-morabito Franois Lieutier 《Forest Ecology and Management》2009,258(7):1619-1628
Planting exotic conifers offers indigenous forest insects an opportunity to extend their host range and eventually to become significant pests. Knowing the ecological and evolutionary modalities driving the colonisation of exotic tree species by indigenous insects is thus of primary importance. We compared the bark beetle communities (Coleoptera: Curculionidae, Scolytinae) associated with both native and introduced conifers in France. The aim of our study was to estimate the influence of both host- and insect-related factors on the beetles’ likelihood to shift onto new hosts. We considered the influence of host origin (i.e. native vs. exotic), host tree species identity, tree bark thickness and tree taxonomic proximity, as well as insects’ host specificity. A field inventory using trap trees was carried out in two regions in France (Limousin and Jura) during two consecutive years (2006 and 2007) on three European native conifer species [Norway spruce (Picea abies); Scots pine (Pinus sylvestris) and European Silver-fir (Abies alba)] and five North American [Sitka spruce (Picea sitchensis); Eastern white pine (Pinus strobus); Grand fir (Abies grandis); Douglas fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata)]. A total of 18 indigenous and 2 exotic bark beetle species were collected. All exotic conifer species were colonised by indigenous bark beetle species and no significant difference was observed of the cumulated species richness of the latter between native and exotic tree species (13 vs. 14, P < 0.05). The ability of indigenous bark beetles to shift onto exotic conifers appeared to strongly depend on host species (significantly structuring bark beetle assemblages), the presence of phylogenetically related native conifer species and that of similar resources, in combination with insect host specificity. Host tree species status (native or exotic) also seemed to be involved, but its effect did not seem as essential as that of the previous factors. These findings are discussed in terms of adaptation, plasticity and practical aspects of forest management. 相似文献
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用灰色多维综合隶属度评估方法对参加2011年国家黄淮海夏大豆区域试验德州试验点l5个大豆新品种(系)的11个性状进行综合评价分析,结果表明:中黄46(品系)、中黄45(品系)、冀09B2(品系)为优良品系,晋遗55(品系)、冀09B5(品系)、冀豆12(CK)、鲁97013-1(品系)、中作06-875(品系)、中作J8023(品系)、中作05-6171(品系)为较好品系,晋豆40(品系)、K06-47(品系)、邯6192(品系)、中作07-22(品系)表现一般,晋大78(品系)表现较差。评价结果与品种实际性状表现吻合,说明采用此方法能比较客观、科学、合理地综合评价新品种(系)。 相似文献
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