全文获取类型
收费全文 | 531篇 |
免费 | 10篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 10篇 |
环保管理 | 92篇 |
综合类 | 67篇 |
基础理论 | 132篇 |
环境理论 | 12篇 |
污染及防治 | 142篇 |
评价与监测 | 39篇 |
社会与环境 | 39篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 22篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 44篇 |
2012年 | 29篇 |
2011年 | 45篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 34篇 |
2007年 | 27篇 |
2006年 | 35篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 29篇 |
2002年 | 18篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有549条查询结果,搜索用时 15 毫秒
501.
502.
M.?B.?M.?BrackeEmail author K.?H.?De?Greef H.?Hopster 《Journal of Agricultural and Environmental Ethics》2005,18(1):27-56
Continued concern for animal welfare may be alleviated when welfare would be monitored on farms. Monitoring can be characterized as an information system where various stakeholders periodically exchange relevant information. Stakeholders include producers, consumers, retailers, the government, scientists, and others. Valuating animal welfare in the animal-product market chain is regarded as a key challenge to further improve the welfare of farm animals and information on the welfare of animals must, therefore, be assessed objectively, for instance, through monitoring. Interviews with Dutch stakeholder representatives were conducted to identify their perceptions about the monitoring of animal welfare. Stakeholder perceptions were characterized in relation to the specific perspectives of each stakeholder. While producers tend to perceive welfare from a production point of view, consumers will use visual images derived from traditional farming and from the animals natural environments. Scientists perceptions of animal welfare are affected by the need to measure welfare with quantifiable parameters. Retailers and governments (policy makers) have views of welfare that are derived from their relationships with producers, consumers, non-governmental organizations (NGOs), and scientists. All interviewed stakeholder representatives stated that animal welfare is important. They varied in the extent to which they weighted economic considerations relative to concern for the animals welfare. Many stakeholders emphasized the importance of communication in making a monitoring system work. Overall, the perspectives for the development of a sustainable monitoring system that substantially improves farm animal welfare were assessed as being poor in the short term. However, a reliable system could be initiated under certain conditions, such as integrated chains and with influential and motivated stakeholders. A scheme is described with attention points for the development of sustainable monitoring systems for farm animal welfare in the long term. 相似文献
503.
/ Roxborough State Park in Colorado's Front Range was established in 1975 following a history of cattle and sheep ranching by private ownership. Survey work conducted from 1979 to 1995 resulted in the documentation of 93 species of butterflies. A variety of factors are responsible for the composition of the butterfly community: (1) overgrazing and its effect on the presence or absence of specific butterfly host plants; (2) habitat differences resulting from topographical and geological features; and (3) ecological and historical biogeography. This study provides data on community sampling adequacy, along with estimates of effort needed to monitor trends in abundance by using a community self-similarity curve and power analysis. An annual monitoring plan is proposed to assess trends in community composition. The plan includes collection of presence/absence and abundance data for select butterflies based on natural history information.KEY WORDS: Butterfly communities; Grazing; Inventory; Monitoring; Natural history 相似文献
504.
André Sceia Juan-Carlos Altamirano-Cabrera Laurent Drouet Thorsten F. Schulz Marc Vielle 《Environmental Modeling and Assessment》2012,17(3):193-207
The residential sector presents a great potential for greenhouse gases (GHG) mitigation. We perform an integrated assessment
of different mitigation policies for Switzerland focusing on the residential sector. We analyze the case of pure incentive
taxes and technical regulations. For our analysis, we have coupled a general equilibrium model with a Swiss residential energy
model. We find that a progressive GHG tax of more than 200 USD2000/tCO2 eq is necessary to reach a target of 50% reduction of GHG emissions in 2050. Finally, we also find that efficiency-based
technical regulations provide limited additional abatement incentives. 相似文献
505.
506.
The aim of the study is the estimation of decay rates for coarse woody debris in large forest regions. These rates, together with estimations of the amount of deadwood, can be used to calculate the release of carbon from that pool into the atmosphere. The model can be used for predictions of decomposition rate constants in a wide range of forest areas (e.g. in process based ecological models, reporting of GHG-emissions), as only easily available predictor variables were used in the regression.Based on an intensive literature research a meta-analysis on influencing factors controlling the constant decay rate of coarse woody debris was set up. The included studies differed significantly in the survey methods as well as in the geographical origin. 39 studies were collected, 30 appeared in North America and nine in Europe. Based on these studies 291 observations of the remaining fraction of coarse woody debris were collected.To quantify the effects that influence the decomposition rates a nonlinear mixed effects model was constructed. Only physiologically interpretable variables were included. With this approach it was possible to determine influencing effects from mean temperature in July, annual rainfall (as quadratic term), diameter of woody material and grouping into hardwoods or conifers and mass- or density loss were significant variables. The mixed effects model also allowed an estimation of the species-specific effects on the decomposition process. These random effects are given for 42 tree species. The degrees of freedom were used efficiently. The model explains 79.6% of the variance and is superior to a comparable multiple regression model. 相似文献
507.
508.
Jan Deprest Marc Van Ranst Lore Lannoo Emma Bredaki Greg Ryan Anna David Jute Richter Tim Van Mieghem 《黑龙江环境通报》2020,40(13):1755-1758
Even though the global COVID-19 pandemic may affect how medical care is delivered in general, most countries try to maintain steady access for women to routine pregnancy care, including fetal anomaly screening. This means that, also during this pandemic, fetal anomalies will be detected, and that discussions regarding invasive genetic testing and possibly fetal therapy will need to take place. For patients, concerns about Severe Acute Respiratory Syndrome-Corona Virus 2 will add to the anxiety caused by the diagnosis of a serious fetal anomaly. Yet, also for fetal medicine teams the situation gets more complex as they must weigh up the risks and benefits to the fetus as well as the mother, while managing a changing evidence base and logistic challenges in their healthcare system. 相似文献
509.
510.
Anthony Galea Manel Grifoll Federico Roman Marc Mestres Vincenzo Armenio Agustin Sanchez-Arcilla Louis Zammit Mangion 《Environmental Fluid Mechanics》2014,14(6):1405-1425
In the present paper, we use numerical simulation to investigate currents, mixing and water renewal in Barcelona harbour under typical conditions of wind forcing for the winter season. This site is of particular importance due to the interplay between touristic and commercial activities, requiring detailed and high-definition studies of water quality within the harbour. We use Large Eddy Simulation (LES) which directly resolves the anisotropic and energetic large scales of motion and parametrizes the small, dissipative, ones. Small-scale turbulence is modelled by the anisotropic Smagorinsky model (ASM) to be employed in presence of large cell anisotropy. The complexity of the harbour is modelled using a combination of curvilinear, structured, non-staggered grid and the immersed boundary method. Boundary conditions for wind and currents at the inlets of the port are obtained from in-situ measurements. Analysis of the numerical results is carried out based on both instantaneous and time-averaged velocity fields. First- and second-order statistics, such as turbulent kinetic energy and horizontal and vertical eddy viscosities, are calculated and their spatial distribution is discussed. The study shows the presence of intense current in the narrow and elongated part of the harbour together with sub-surface along-shore elongated rolling structures (with a time scale of a few hours), and they contribute to the vertical water mixing. Time-averaged velocity field reveals intense upwelling and downwelling zones along the walls of the harbour. The analysis of second-order statistics shows strong inhomogeneity of turbulent kinetic energy and horizontal and vertical eddy viscosities in the horizontal plane, with larger values in the regions characterized by stronger currents. The water renewal within the port is quantified for particular sub-domain regions, showing that the complexity of the harbour is such that certain in-harbour basins have a water renewal of over five days, including the yacht marina area. The LES solution compares favourably with available current-meter data. The LES solution is also compared with a RANS solution obtained in literature for the same site under the same forcing conditions, the comparison demonstrating a large sensitivity of properties to model resolution and frictional parametrization. 相似文献