首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2901篇
  免费   170篇
  国内免费   84篇
安全科学   448篇
废物处理   34篇
环保管理   1036篇
综合类   613篇
基础理论   362篇
环境理论   44篇
污染及防治   141篇
评价与监测   87篇
社会与环境   261篇
灾害及防治   129篇
  2024年   7篇
  2023年   51篇
  2022年   34篇
  2021年   98篇
  2020年   109篇
  2019年   114篇
  2018年   90篇
  2017年   177篇
  2016年   152篇
  2015年   131篇
  2014年   108篇
  2013年   188篇
  2012年   126篇
  2011年   188篇
  2010年   75篇
  2009年   169篇
  2008年   147篇
  2007年   122篇
  2006年   108篇
  2005年   110篇
  2004年   87篇
  2003年   84篇
  2002年   87篇
  2001年   71篇
  2000年   70篇
  1999年   64篇
  1998年   43篇
  1997年   38篇
  1996年   37篇
  1995年   41篇
  1994年   24篇
  1993年   33篇
  1992年   20篇
  1991年   10篇
  1990年   17篇
  1989年   12篇
  1988年   8篇
  1987年   12篇
  1986年   12篇
  1985年   19篇
  1984年   9篇
  1983年   10篇
  1982年   6篇
  1981年   12篇
  1980年   3篇
  1979年   4篇
  1978年   4篇
  1977年   5篇
  1972年   2篇
  1971年   3篇
排序方式: 共有3155条查询结果,搜索用时 93 毫秒
901.
Abstract: As nearly all of Texas’ rural lands are privately owned, landowner associations for the management of white‐tailed deer and ground‐water have become increasingly popular. Deer are a common‐pool resource with transboundary characteristics, requiring landowner cooperation for effective management. Ground‐water reserves are economically important to landowners, but are governed by the “rule of capture” whereby property rights are not defined. One ground‐water association and four wildlife management associations (WMAs) were surveyed to characterize their member demographics, land use priorities, attitudes, and social capital. Members of the ground‐water cooperative were part of a much larger, more heterogeneous, and more recently formed group than members of WMAs. They also placed greater importance on utilitarian aspects of their properties, as opposed to land stewardship for conservation as practiced by members of WMAs. If ground‐water association members could be more locally organized with more frequent meetings, social capital and information sharing may be enhanced and lead to land stewardship practices for improved hydrologic functions and sustained ground‐water supply. This, coupled with pumping rules assigned by the local ground‐water district, could yield an effective strategy that is ecologically and hydrologicaly sound, and that allows rural provision of water supply to urban consumers.  相似文献   
902.
Abstract: Spatio‐temporal linkages between hydrologic and ecologic dimensions of watersheds play a critical role in conservation policies. Habitat potential is influenced by variation along longitudinal and lateral gradients and land use disturbance. An assessment of these influences provides critical information for protecting watershed ecosystems and in making spatially explicit, conservation decisions. We use an ecohydrologic approach that focuses on interface between hydrological and ecological processes. This study focuses on changes in watershed habitat potentials along lateral (riparian), and longitudinal (stream order) dimensions and disturbance (land use). The habitat potentials were evaluated for amphibians, reptiles, mammals, and birds in the Westfield River Watershed of Massachusetts using geographic information systems and multivariate analysis. We use a polynomial model to study nonlinear effects using robust regression. Various spatial policies were modeled and evaluated for influence on species diversity. All habitat potentials showed a strong influence along spatial dimensions and disturbance. The habitat potential for all vertebrate groups studied decreased as the distance from the riparian zone increased. Headwaters and lower order subwatersheds had higher levels of species diversity compared to higher order subwatersheds. It was observed that locations with the least disturbance also had higher habitat potential. The study identifies three policy criteria that could be used to identify critical areas within a watershed to conserve habitat suitable for various species through management and restoration activities. A spatially variable policy that is based on stream order, riparian distance, and land use can be used to maximize watershed ecological benefits. Wider riparian zones with variable widths, protection of headwaters and lower order subwatersheds, and minimizing disturbance in riparian and headwater areas can be used in watershed policy. These management objectives could be achieved using targeted economic incentives, best management practices, zoning laws, and educational programs using a watershed perspective.  相似文献   
903.
The regulatory structures underlying United States and European Union policies regarding genetically modified (GM) food and crops are fundamentally different. The US regulates GM foods and crops as end products, applying roughly the same regulatory framework that it does to non GM foods or crops. The EU, on the other hand, regulates products of agricultural biotechnology as the result of a specific production process. Accordingly, it has developed a network of rules that regulate GM foods and crops specifically. As a result, US regulation of GM foods and crops is relatively permissive, whereas EU regulation is relatively restrictive. Why are genetically modified food policies in the United States and the European Union so strikingly different? In the light of the recent World Trade Organization dispute on agricultural biotechnology, it may seem that economic interests are the driving force behind policies. While they are certainly part of the picture, the issue is far more complex. This paper argues that three different elements help explain differences between US and EU GM food policies. First, an investigation of US and European policies of the 1970s and 1980s on recombinant DNA research and of events leading up to early GM food and crop regulation allows a deeper understanding of current policy. Second, scrutinizing underlying values and norms can uncover the beliefs that condition current GM food and crop policy. Third, an analysis of involved actors’ views and levels of success in influencing policy is essential to understanding US and EU policies.  相似文献   
904.
The traditional vision of the role science should play in policy making is of a two stage process of scientists first finding out the facts, and then policy makers making a decision about what to do about them. We argue that this two stage process is a fiction and that a distinction must be drawn between pure science and science in the service of public policy. When science is transferred into the policy realm, its claims to truth get undermined because we must abandon the open-ended nature of scientific inquiry. When we move from the sphere of science to the sphere of policy, we pick an arbitrary point in the open-ended scientific process, and ask our experts to give us the answer. The choice of the endpoint, however, must always be arbitrary and determined by non-scientific factors. Thus, the two stages in the model of first finding the facts, and then making a decision about what to do, cannot be clearly separated. The second stage clearly affects the first. This conclusion will have implications about existing scientific policy institutions. For example, we advocate that the environmental assessment process be radically overhauled, or perhaps even let go. It will be our position that ultimately a better model for the involvement of scientists in public policy debates is that of being participants in particular interest groups (“hired guns”), rather than as supposedly unbiased consultants to decision-makers.  相似文献   
905.
In recent years, Turkey has experienced rapid economic and population growth coupled with both an equally rapid increase in energy consumption and a vast disparity in welfare between socioeconomic groups and regions. In turn, these pressures have accelerated the destruction of productive, assimilative, and regenerative capacities of the ecosystems, which are essential for the well-being of the people and the economy. This paper describes the structure and function of major ecosystem types in Turkey and discusses the underlying causes of environmental degradation in the framework of economy, energy, environment, and ethics. From a national perspective, this paper suggests three sustainability-based policies necessary for Turkey's long-term interests that balance economic, environmental, and energy goals: (1) decoupling economic growth from energy consumption growth through the development of energy-efficient and renewable energy technologies; (2) linking economic efficiency and distributive justice of wealth and power through distributive and participatory public policies; and (3) integrating the economic and ecological systems through the internalization of externalities and ecosystem rehabilitation.  相似文献   
906.
A minimal dynamical systems model that couples agricultural activity, native vegetation, and hydrological processes is developed to explore policy options regarding regional-scale soil and water salinization in southeastern Australia. The analysis suggests that although considerable revegetation is required to restore catchment water balance, the current value of water in uses other than agriculture is too low for revegetation to be economically viable. In contrast, groundwater pumping generates significant short-term gains by preventing soil salinization but is not a viable long-term solution. Thus, effective salinity management policy must include mechanisms to increase the value of water in uses other than irrigated agriculture to achieve sufficient long-term revegetation. These results are robust over a wide range of parameter values and thus provide a basis for policy action in the face of uncertainty about groundwater flow characteristics.  相似文献   
907.
Preventing the introduction of nonindigenous species (NIS) is the most efficient way to avoid the costs and impacts of biological invasions. The transport of fouling species on ship hulls is an important vector for the introduction of marine NIS. We use quantitative risk screening techniques to develop a predictive tool of the abundance and variety of organisms being transported by ocean-going yachts. We developed and calibrated an ordinal rank scale of the abundance of fouling assemblages on the hulls of international yacht hulls arriving in New Zealand. Fouling ranks were allocated to 783 international yachts that arrived in New Zealand between 2002 and 2004. Classification tree analysis was used to identify relationships between the fouling ranks and predictor variables that described the maintenance and travel history of the yachts. The fouling ranks provided reliable indications of the actual abundance and variety of fouling assemblages on the yachts and identified most (60%) yachts that had fouling on their hulls. However, classification tree models explained comparatively little of the variation in the distribution of fouling ranks (22.1%), had high misclassification rates (∼43%), and low predictive power. In agreement with other studies, the best model selected the age of the toxic antifouling paint on yacht hulls as the principal risk factor for hull fouling. Our study shows that the transport probability of fouling organisms is the result of a complex suite of interacting factors and that large sample sizes will be needed for calibration of robust risk models.  相似文献   
908.
在安全管理越来越得到重视的今天,安全责任追究力度越来越大,政府和官员对安全管理更多倾向于采取自我保护式的高压和严惩。这种管理模式在各方利益主体的博弈下,使得安全管理的目标与结果产生变异,甚至会产生不愿看到的结果。事实上安全管理制度运行的成本是巨大的,单靠严惩是不能解决问题的。本文运用博弈理论、新制度经济学、信息经济学、机制设计理论等经济学方法,对安全管理的运行机制进行分析,认为安全管理必须理性预防,堵疏结合,通过设计符合客观规律的安全管理运行机制,方能确保安全生产。  相似文献   
909.
污水处理行业的技术经济特性决定了污水处理行业政府规制的必要性.明确的规制目标是建立污水处理行业政府规制体制的基本前提.在详细分析了污水行业技术经济特性的基础上,提出了当前污水处理行业政府规制目标,并结合当前污水处理行业政府规制现状,做了相关政策的分析研究,为政府监管规制建设做了有益的探索.  相似文献   
910.
The many well-publicized food scandals in recent years have resulted in a general state of vulnerable trust. As a result, building consumer trust has become an important goal in agri-food policy. In their efforts to protect trust in the agricultural and food sector, governments and industries have tended to consider the problem of trust as merely a matter of informing consumers on risks. In this article, we argue that the food sector better addresses the problem of trust from the perspective of the trustworthiness of the food sector itself. This broad idea for changing the focus of trust is the assumption that if you want to be trusted, you should be trustworthy. To provide a clear understanding of what being trustworthy means within the food sector, we elaborate on both the concept of trust and of responsibility. In this way we show that policy focused on enhancing transparency and providing information to consumers is crucial, but not sufficient for dealing with the problem of consumer trust in the current agri-food context.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号