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Vegetation structure constrains primary production response to water availability in the Patagonian steppe 总被引:3,自引:0,他引:3
Grassland aboveground net primary production (ANPP) increases linearly with precipitation in space and time, but temporal models relating time series of ANPP and annual precipitation for single sites show lower slopes and regression coefficients than are shown by spatial models. The analysis of several ANPP time series showed lags in the ecosystem response to increased water availability, which may explain the difference between spatial and temporal models. The lags may result from constraints that ecosystems experience after drought. Our objective was to explore the structural constraints of the ANPP response to rainfall variability in a semiarid ecosystem, the Patagonian steppe, in southern Argentina. We designed a 3-yr rainfall manipulation experiment where we decreased water input with rainout shelters during two consecutive years, which included three levels of rainfall interception (30%, 55%, and 80%) and a control. In the third year, we irrigated one-half of the plots of each rainfall-interception treatment. We evaluated the immediate effects of drought on current-year ANPP and the effects of previous-year drought on vegetation recovery after water supplementation. ANPP (g x m(-2) x yr(-1)) was linearly related to annual precipitation input (APPT; mm/yr) along the experimental precipitation gradient (ANPP = 0.13 x APPT + 58.3; r2 = 0.34, P < 0.01), and this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density (D; no. individuals/mm2) was related to the precipitation received during the drought period (D = 0.11 x APPT + 18; r2 = 0.39, P < 0.05). The recovery of plants after irrigation was lower for those plots that had experienced experimental drought the previous years relative to controls, and the lags were proportional to the intensity of drought. Therefore, our results suggest that the density of plants may constrain the recovery of vegetation after drought, and these constraints may determine lags that limit the capacity of the ecosystem to take advantage of wet years after dry years. 相似文献
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Edmilson F. de Oliveira-Filho Kennya G. S. Lopes Deivson S. Cunha Virginia S. Silva Clara N. Barbosa Daniel F. Brandespim José Wilton Pinheiro Junior Giovani R. Bertani Laura H. V. G. Gil 《Food and environmental virology》2017,9(3):256-259
Anti-HEV antibodies were detected in animals from abattoir and in farms from northeast Brazil. Our results suggest that HEV is highly disseminated in the swine population and might present a great risk to animal handlers and for consumption of raw or undercooked meat and meat products in northeast Brazil. 相似文献
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Umberto Arena Lucio Zaccariello Maria Laura Mastellone 《Waste management (New York, N.Y.)》2010,30(7):1212-1219
Five alternative waste-derived fuels obtained from municipal solid waste and different post-consumer packaging were fed in a pilot-scale bubbling fluidized bed gasifier, having a maximum feeding capacity of 100 kg/h. The experimental runs utilized beds of natural olivine, quartz sand or dolomite, fluidized by air, and were carried out under various values of equivalence ratio. The process resulted technically feasible with all the materials tested. The olivine, a neo-silicate of Fe and Mg with an olive-green colour, has proven to be a good candidate to act as a bed catalyst for tar removal during gasification of polyolefin plastic wastes. Thanks to its catalytic activity it is possible to obtain very high fractions of hydrogen in the syngas (between 20% and 30%), even using air as the gasifying agent, i.e. in the most favourable economical conditions and with the simplest plant and reactor configuration. The catalytic activity of olivine was instead reduced or completely inhibited when waste-derived fuels from municipal solid wastes and aggregates of different post-consumer plastic packagings were fed. Anyhow, these materials have given acceptable performance, yielding a syngas of sufficient quality for energy applications after an adequate downstream cleaning. 相似文献
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ABSTRACTSustainability has emerged as a central concept for discussing the current state of the human-environment system and planning for its future. To delve into the depths of sustainability means to talk about ecology, economy, and equity as fundamentally interconnected. However, each continues to be colonised by normative epistemologies of ecological sciences, neoclassical economics, and development, suggesting that with enough science and development, a more equitable sustainability is achievable. In our analysis, place emerges as an alternative epistemology through which to analyze sustainability. Place exists at multiple spatial and temporal scales, understood through direct observation of boundaries, processes and patterns, phenomenologically through individual experience, and as a complex hybrid: always emerging through interactions among individuals and institutions. Despite the ubiquity of place in the socio-ecological literature, the complexity of place in relation to sustainability is under-theorised, and in as much as sustainability happens or does not happen in real places rather than in policies and models, a place-based sustainability framework is necessary to move forward. To address this gap, we developed the emplacement framework, consisting of four domains: displacement, misplacement, replacement, and emplacement. Each domain is dynamic, constructing place as praxis, and reframing sustainability as a site of collective inquiry and choices. Our goal is to facilitate the active and on-going practices of place-based research and engagement among scholars, activists, and other community members by providing a structure for transdisciplinary dialogue and the application of transdisciplinary research to enable better decision-making. 相似文献
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Laura M. Graves 《组织行为杂志》1993,14(4):349-370
In response to recent suggestions that employment interview researchers adopt an idiographic approach focusing on differences in effectiveness across interviewers, this article proposes a model of sources of individual differences in interviewer effectiveness. The model is used as a framework for evaluating existing research. This review of the literature reveals individual differences across interviewers in a number of areas, but indicates that research has failed to examine adequately the possible sources of individual differences and their links to effectiveness. Suggestions for future research are offered. 相似文献