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1.
Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small‐scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta‐analysis of the outcomes of plant–herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between‐taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore–plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed‐nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed‐nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore–plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant–herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top‐down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats that contain aquatic plants.  相似文献   
2.
Habitat destruction is driving biodiversity loss in remaining ecosystems, and ecosystem functioning and services often directly depend on biodiversity. Thus, biodiversity loss is likely creating an ecosystem service debt: a gradual loss of biodiversity‐dependent benefits that people obtain from remaining fragments of natural ecosystems. Here, we develop an approach for quantifying ecosystem service debts, and illustrate its use to estimate how one anthropogenic driver, habitat destruction, could indirectly diminish one ecosystem service, carbon storage, by creating an extinction debt. We estimate that c. 2–21 Pg C could be gradually emitted globally in remaining ecosystem fragments because of plant species loss caused by nearby habitat destruction. The wide range for this estimate reflects substantial uncertainties in how many plant species will be lost, how much species loss will impact ecosystem functioning and whether plant species loss will decrease soil carbon. Our exploratory analysis suggests that biodiversity‐dependent ecosystem service debts can be globally substantial, even when locally small, if they occur diffusely across vast areas of remaining ecosystems. There is substantial value in conserving not only the quantity (area), but also the quality (biodiversity) of natural ecosystems for the sustainable provision of ecosystem services.  相似文献   
3.
Biodiversity‐ecosystem functioning experiments have established that species richness and composition are both important determinants of ecosystem function in an experimental context. Determining whether this result holds for real‐world ecosystem services has remained elusive, however, largely due to the lack of analytical methods appropriate for large‐scale, associational data. Here, we use a novel analytical approach, the Price equation, to partition the contribution to ecosystem services made by species richness, composition and abundance in four large‐scale data sets on crop pollination by native bees. We found that abundance fluctuations of dominant species drove ecosystem service delivery, whereas richness changes were relatively unimportant because they primarily involved rare species that contributed little to function. Thus, the mechanism behind our results was the skewed species‐abundance distribution. Our finding that a few common species, not species richness, drive ecosystem service delivery could have broad generality given the ubiquity of skewed species‐abundance distributions in nature.  相似文献   
4.
初小静  韩广轩 《生态学杂志》2015,26(10):2978-2990
湿地由于具有较高的初级生产力以及较低的有机质降解速率而成为缓解全球变暖的潜在有效碳汇.虽然近年来中国湿地生态系统CO2交换过程及其影响机制研究取得了一系列进展,但尚缺乏对数据进行系统性整合分析.基于29篇文献的数据,对中国21个典型湿地植被净生态系统CO2交换(NEE)、生态系统呼吸(Reco)、总初级生产力(GPP)、NEE的光响应参数以及Reco的温度响应参数进行整合分析,并探讨了这些指标对温度与降雨的响应.结果表明: 年尺度上,气温和降雨量对NEE(R2=50%,R2=57% )、GPP(R2=60%,R2=50%)和Reco(R2=44%,R2=50%)均有显著影响(P<0.05).生长季尺度上,NEE (R2=50%)、GPP (R2=36%)和Reco(R2=19%)与气温呈显著相关(P<0.05);同时NEE(R2=33%)和GPP(R2=25%)也与降雨量呈显著相关(P<0.05),但Reco与降雨量的相关关系不显著(P>0.05).生长季降雨量与最大光合速率(Amax)之间呈显著相关 (P<0.01),但与表观量子产率(α)、白天生态系统呼吸速率(Reco,day)无显著相关(P>0.05).生长季气温对α、Amax和Reco, day均无显著影响(P>0.05).生态系统基础呼吸速率(Rref)与降雨量无显著相关(P>0.05),但是生态系统呼吸的温度敏感系数(Q10)与降雨量呈显著的线性负相关(P<0.05),同时气温对Q10(R2=0.35)、Rref(R2=0.46)均产生显著影响(P<0.05).  相似文献   
5.
Climate extremes, such as drought, may have immediate and potentially prolonged effects on carbon cycling. Grasslands store approximately one‐third of all terrestrial carbon and may become carbon sources during droughts. However, the magnitude and duration of drought‐induced disruptions to the carbon cycle, as well as the mechanisms responsible, remain poorly understood. Over the next century, global climate models predict an increase in two types of drought: chronic but subtle ‘press‐droughts’, and shorter term but extreme ‘pulse‐droughts’. Much of our current understanding of the ecological impacts of drought comes from experimental rainfall manipulations. These studies have been highly valuable, but are often short term and rarely quantify carbon feedbacks. To address this knowledge gap, we used the Community Land Model 4.0 to examine the individual and interactive effects of pulse‐ and press‐droughts on carbon cycling in a mesic grassland of the US Great Plains. A series of modeling experiments were imposed by varying drought magnitude (precipitation amount) and interannual pattern (press‐ vs. pulse‐droughts) to examine the effects on carbon storage and cycling at annual to century timescales. We present three main findings. First, a single‐year pulse‐drought had immediate and prolonged effects on carbon storage due to differential sensitivities of ecosystem respiration and gross primary production. Second, short‐term pulse‐droughts caused greater carbon loss than chronic press‐droughts when total precipitation reductions over a 20‐year period were equivalent. Third, combining pulse‐ and press‐droughts had intermediate effects on carbon loss compared to the independent drought types, except at high drought levels. Overall, these results suggest that interannual drought pattern may be as important for carbon dynamics as drought magnitude and that extreme droughts may have long‐lasting carbon feedbacks in grassland ecosystems.  相似文献   
6.
北京城市绿地表层土壤碳氮分布特征   总被引:12,自引:4,他引:8  
罗上华  毛齐正  马克明  邬建国 《生态学报》2014,34(20):6011-6019
在北京中心城区及周边郊区(覆盖六环路范围),采集不同类型绿地表层(0—20cm)土壤样品490份,测定了土壤有机碳、无机碳、全碳和全氮含量,探讨了城市土壤碳氮分布特征。结果表明:城市不同类型绿地土壤中碳含量差异明显,行道树土壤的有机碳、无机碳和全碳含量均显著高于其他类型绿地,而其它类型土壤有机碳含量差异不显著;居住绿地、道路绿地、单位绿地和公园绿地土壤无机碳含量显著高于生产绿地、防护绿地;城市土壤有机碳、无机碳和全碳含量与距离城市中心距离呈显著的负相关关系;与郊区土壤相比,城区绿地土壤有机碳、无机碳含量有富集的趋势,且无机碳增加更加明显;与郊区农业土壤相比,城市绿地土壤中有机碳有明显地增加趋势,说明北京的城市化在一定程度上有利于土壤碳库的累积。不同类型绿地土壤全氮含量差异不显著,城郊之间全氮含量也无显著差异,土壤全氮质量分数和碳氮比有逐渐减小的趋势,城市化对土壤氮的影响需要进一步研究。  相似文献   
7.
辽宁省菜田生态系统组分优势值与系统优势度分析   总被引:2,自引:1,他引:1  
辽宁省菜田生态系统组分优势值与系统优势度分析周宝利,葛晓光李宁义(沈阳农业大学园艺系,110161)(沈阳市城建中专,110013)AnalysisonSuperiorityValueandDominanceDegreeofVariousCompon...  相似文献   
8.
9.
Prospective life cycle assessment (LCA) needs to deal with the large epistemological uncertainty about the future to support more robust future environmental impact assessments of technologies. This study proposes a novel approach that systematically changes the background processes in a prospective LCA based on scenarios of an integrated assessment model (IAM), the IMAGE model. Consistent worldwide scenarios from IMAGE are evaluated in the life cycle inventory using ecoinvent v3.3. To test the approach, only the electricity sector was changed in a prospective LCA of an internal combustion engine vehicle (ICEV) and an electric vehicle (EV) using six baseline and mitigation climate scenarios until 2050. This case study shows that changes in the electricity background can be very important for the environmental impacts of EV. Also, the approach demonstrates that the relative environmental performance of EV and ICEV over time is more complex and multifaceted than previously assumed. Uncertainty due to future developments manifests in different impacts depending on the product (EV or ICEV), the impact category, and the scenario and year considered. More robust prospective LCAs can be achieved, particularly for emerging technologies, by expanding this approach to other economic sectors beyond electricity background changes and mobility applications as well as by including uncertainty and changes in foreground parameters. A more systematic and structured composition of future inventory databases driven by IAM scenarios helps to acknowledge epistemological uncertainty and to increase the temporal consistency of foreground and background systems in LCAs of emerging technologies.  相似文献   
10.
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