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   4047篇
  免费   70篇
  国内免费   36篇
安全科学   227篇
废物处理   129篇
环保管理   1054篇
综合类   382篇
基础理论   997篇
环境理论   8篇
污染及防治   893篇
评价与监测   272篇
社会与环境   151篇
灾害及防治   40篇
  2023年   16篇
  2022年   25篇
  2021年   35篇
  2020年   31篇
  2019年   43篇
  2018年   55篇
  2017年   76篇
  2016年   97篇
  2015年   84篇
  2014年   93篇
  2013年   482篇
  2012年   148篇
  2011年   208篇
  2010年   136篇
  2009年   153篇
  2008年   177篇
  2007年   221篇
  2006年   159篇
  2005年   140篇
  2004年   146篇
  2003年   143篇
  2002年   118篇
  2001年   77篇
  2000年   87篇
  1999年   59篇
  1998年   61篇
  1997年   52篇
  1996年   69篇
  1995年   64篇
  1994年   72篇
  1993年   59篇
  1992年   52篇
  1991年   45篇
  1990年   44篇
  1989年   36篇
  1988年   46篇
  1987年   39篇
  1986年   41篇
  1985年   35篇
  1984年   39篇
  1983年   42篇
  1982年   50篇
  1981年   53篇
  1980年   26篇
  1979年   33篇
  1978年   26篇
  1977年   35篇
  1976年   15篇
  1974年   11篇
  1972年   13篇
排序方式: 共有4153条查询结果,搜索用时 31 毫秒
981.
982.
According to the targets set for sustainability, integrating the principles of sustainable development into country policies and programs is one of the main goals for development projects. A major challenge in the development field is cross-sectoral integrated planning and achieving multi-stakeholder consensus for collaborative joint projects, especially when sustainability is a goal. This increases the complexity of the multi-stakeholder interaction in decision making and requires enhanced mechanisms for stakeholder participation, coordination, and commitment beyond narrow self-interest. A critical aspect in the decision making process is to enable stakeholders to not only interpret and make decisions based on expert judgments, but also to appropriately involve the relevant parties in the research and decision making process. Therefore, scientific analyses in multi-stakeholder contexts have to be more transparent, participatory, and stakeholder-based in order to provide useful information to assist responsible decision making.This paper presents an outline of a stakeholder-based life cycle assessment approach that can be used to support sustainable decision making in multi-stakeholder contexts. The framework is discussed and compared to other common methods used to support environmental decision making in development projects. We argue that the fundamental concept of life cycle thinking can be effectively used to incorporate stakeholders in the research and decision making process, which can lead to more comprehensive, yet achievable assessments in collaboration with stakeholders. Life cycle thinking is not just a way to examine environmental impacts of activities, but also a way to comprehend and visualize a broader set of upstream and downstream consequences of decisions in development planning and implementation. A life cycle framework including the mapping of stakeholder involvement at each activity in upstream and downstream stages would give stakeholders a holistic view that they otherwise may not have.  相似文献   
983.
To offset the detrimental effects of urbanization on groundwater recharge, stormwater managers are focusing on infiltrating much of the runoff from a site that was generated because of development. For this to be effective, tools are required to predict the potential for contamination resulting from this infiltration for many site conditions, because infiltration should be stressed in areas where the least potential for causing groundwater contamination exists. Factors that influence contamination potential include the pollutant concentration in the runoff directed to the infiltration device and the ability of the underlying soil to remove the pollutant. The groundwater contamination potential of some pollutants, even those with high concentrations and moderate-to-high mobilities, can be reduced with proper pretreatment before infiltration. This paper presents a methodology that can be used to evaluate infiltration as an management option and introduces two different levels of models that could be used to evaluate contamination potential.  相似文献   
984.
Increasing the share of renewable energy is of principal concern for the EU energy policy. A number of policies have been adopted, and, in part, been implemented by the EU member countries. An increasing share of renewable energy implies an increasing utilisation of biofuels in general and of forest-based biomass in particular. However, in the EU, the endowment and uses of forest-base biomass are diverse suggesting that an increasing trade would become necessary in order to cost effectively increase the utilisation of forest-based biomass. The purpose of this study is to, in the presence of EU energy policy, quantify and analyse possible trade levels for forest fuels in the EU. Particularly, the consequences on trade after implementing the White Paper and the RES-E Directive are analysed. Investigating the European trade in forest fuels is important for understanding how industry sectors in the EU will be affected by the policies. The results suggest that the implementation of the White Paper and the RES-E Directive will increase the trade in forest fuels, resulting in total trade increases of up to 67 percent. Furthermore, the national net trading levels are possible to derive. Depending on policy implementation the results differ – a country that was net importing given the White Paper implementation can instead be net exporting when applying the RES-E Directive. The fact that the policy implementations will increase the trade may mitigate potential industry problems to secure the needed inputs. On the other hand, the integration of countries increases the possibility for some industries to increase their production even more, possibly strengthening any input scarcity problems. It is therefore not possible to generally conclude if a more integrated European forest fuel market, and hence an increased European forest fuel trade, will mitigate industry problems to secure their needed inputs or not.  相似文献   
985.
986.
Water scarcity is a highly contested concept. The dominant narratives of water scarcity in policy debates have been criticised for prioritising purely quantitative metrics and eliding questions of inequality and power. While much scholarship on water scarcity examines contexts in the global South where potable water infrastructures do not reach most residents, this article examines conflict over commercial water extraction in a Northern setting where access to potable tap water is nearly universal, yet local water supplies are increasingly constrained. It addresses three main questions: (1) How are narratives or discourses of water scarcity mobilised by a range of actors in local conflicts over groundwater extraction for water bottling?; (2) To what extent do these discourses invoke biophysical versus socially produced scarcity, current versus future scarcity, and local versus regional or global scales of scarcity?; and (3) What are the implications of the findings for efforts by environmental advocates and communities to protect local water supplies? We explore these questions by analysing a local case study of conflict over groundwater extraction by the leading bottled water firm, Nestlé Waters, in southwestern Ontario, Canada. We find that the scarcity narratives deployed by local residents, activists, public officials, and bottling industry representatives illustrate the use of several forms of figurative conflation involving geographic and temporal scales of water scarcity, and economic and volumetric forms of scarcity. We argue that this conflation illuminates deeper issues of economic and social justice at the heart of the conflict, which transcend reductionist hydrological assessments of scarcity or abundance.  相似文献   
987.
Environmental and Ecological Statistics - Misidentification of animals is a common problem for many capture-recapture experiments. Considerably misleading inference may be obtained when traditional...  相似文献   
988.
Achieving ethically responsible decisions is crucial for the success of biodiversity conservation projects. We adapted the ethical matrix, decision tree, and Bateson's cube to assist in the ethical analysis of complex conservation scenarios by structuring these tools so that they can implement the different value dimensions (environmental, social, and animal welfare) involved in conservation ethics. We then applied them to a case study relative to the decision-making process regarding whether or not to continue collecting biomaterial on the oldest of the two remaining northern white rhinoceroses (Ceratotherium simum cottoni), a functionally extinct subspecies of the white rhinoceros. We used the ethical matrix to gather ethical pros and cons and as a starting point for a participatory approach to ethical decision-making. We used decision trees to compare the different options at stake on the basis of a set of ethical desiderata. We used Bateson's cube to establish a threshold of ethical acceptability and model the results of a simple survey. The application of these tools proved to be pivotal in structuring the decision-making process and in helping reach a shared, reasoned, and transparent decision on the best option from an ethical point of view among those available.  相似文献   
989.
Abstract

Objective: In order to introduce automated vehicles on public roads, it is necessary to ensure that these vehicles are safe to operate in traffic. One challenge is to prove that all physically possible variations of situations can be handled safely within the operational design domain of the vehicle. A promising approach to handling the set of possible situations is to identify a manageable number of logical scenarios, which provide an abstraction for object properties and behavior within the situations. These can then be transferred into concrete scenarios defining all parameters necessary to reproduce the situation in different test environments.

Methods: This article proposes a framework for defining safety-relevant scenarios based on the potential collision between the subject vehicle and a challenging object, which forces the subject vehicle to depart from its planned course of action to avoid a collision. This allows defining only safety-relevant scenarios, which can directly be related to accident classification. The first criterion for defining a scenario is the area of the subject vehicle with which the object would collide. As a second criterion, 8 different positions around the subject vehicle are considered. To account for other relevant objects in the scenario, factors that influence the challenge for the subject vehicle can be added to the scenario. These are grouped as action constraints, dynamic occlusions, and causal chains.

Results: By applying the proposed systematics, a catalog of base scenarios for a vehicle traveling on controlled-access highways has been generated, which can directly be linked to parameters in accident classification. The catalog serves as a basis for scenario classification within the PEGASUS project.

Conclusions: Defining a limited number of safety-relevant scenarios helps to realize a systematic safety assurance process for automated vehicles. Scenarios are defined based on the point of the potential collision of a challenging object with the subject vehicle and its initial position. This approach allows defining scenarios for different environments and different driving states of the subject vehicle using the same mechanisms. A next step is the generation of logical scenarios for other driving states of the subject vehicle and for other traffic environments.  相似文献   
990.
Signals used in female choice should honestly advertise the benefits that males can provide, with direct benefits often argued as being more important than indirect benefits. However, the nature of direct benefits in species without paternal care or nuptial gifts is poorly understood. Previous studies on lizards suggest that females decide where to settle and assumedly who to mate with based on information contained in scent marks from territorial males. Access to high-quality thermal resources is crucial for female reproductive success. Females may therefore be able to detect and exploit thermal-induced variation in the chemical composition of male scent marks when assessing the quality of his territory. We show that the amount of time male wall lizards (Podarcis muralis) are allowed to bask significantly alters the chemical composition of their femoral secretions used in scent marking. The direction of the change is consistent with adaptive plasticity to maintain signalling efficacy under warm conditions that increase evaporation of femoral secretions. The compounds affected by basking experience included those previously associated with male quality or shown to mediate male–male competition in lizards. However, whilst female lizards could discriminate between scent marks of males that had experienced different basking conditions, they did not preferentially associate with the scent from males from high-quality thermal conditions. These results highlight the potential importance of a previously neglected environmental effect on chemical signalling. We suggest thermal effects may have significant consequences for scent-mark composition in variable environments, with potential repercussions on olfactory communication in lizards.  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