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   8207篇
  免费   386篇
  国内免费   307篇
安全科学   549篇
废物处理   78篇
环保管理   1622篇
综合类   3359篇
基础理论   555篇
环境理论   19篇
污染及防治   458篇
评价与监测   1890篇
社会与环境   248篇
灾害及防治   122篇
  2024年   16篇
  2023年   88篇
  2022年   145篇
  2021年   153篇
  2020年   281篇
  2019年   148篇
  2018年   138篇
  2017年   220篇
  2016年   280篇
  2015年   284篇
  2014年   389篇
  2013年   491篇
  2012年   433篇
  2011年   592篇
  2010年   355篇
  2009年   481篇
  2008年   359篇
  2007年   424篇
  2006年   419篇
  2005年   303篇
  2004年   270篇
  2003年   387篇
  2002年   286篇
  2001年   285篇
  2000年   291篇
  1999年   242篇
  1998年   197篇
  1997年   212篇
  1996年   139篇
  1995年   96篇
  1994年   105篇
  1993年   96篇
  1992年   61篇
  1991年   44篇
  1990年   26篇
  1989年   26篇
  1988年   16篇
  1987年   13篇
  1986年   20篇
  1985年   17篇
  1984年   16篇
  1983年   6篇
  1982年   9篇
  1981年   7篇
  1980年   10篇
  1979年   3篇
  1978年   13篇
  1977年   6篇
  1974年   1篇
  1973年   1篇
排序方式: 共有8900条查询结果,搜索用时 15 毫秒
1.
The rapidly changing climate is posing growing threats for all species, but particularly for those already considered threatened. We reviewed 100 recovery plans for Australian terrestrial threatened species (50 fauna and 50 flora plans) written from 1997 to 2017. We recorded the number of plans that acknowledged climate change as a threat and of these how many proposed specific actions to ameliorate the threat. We classified these actions along a continuum from passive or incremental to active or interventionist. Overall, just under 60% of the sampled recovery plans listed climate change as a current or potential threat to the threatened taxa, and the likelihood of this acknowledgment increased over time. A far smaller proportion of the plans, however, identified specific actions associated with ameliorating climate risk (22%) and even fewer (9%) recommended any interventionist action in response to a climate-change-associated threat. Our results point to a disconnect between the knowledge generated on climate-change-related risk and potential adaptation strategies and the extent to which this knowledge has been incorporated into an important instrument of conservation action.  相似文献   
2.
We report a case of in utero paracentesis of ascites in a fetus with meconium peritonitis due to volvulus at 34 weeks which resulted in the correction of an abnormal fetal heart rate pattern and enabled vaginal delivery by preventing abdominal dystocia. The intrauterine intervention also helped to establish the diagnosis and potentially reduced the respiratory compromise after birth. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
3.
Cultural heritage is being addressed by a number of charters and conventions and it is clear that its consideration within decision-making processes is progressively becoming a real challenge, both for developers and public authorities. Against this background, this paper reviews the environmental assessment framework developed by the European Community, as this should increasingly influence decision making about cultural heritage in an urban setting. The legislative framework for access to environmental information is also reviewed because of its relevance to the decision-making process.The Directives on Environmental Impact Assessment and Strategic Environmental Assessment both require a consideration of cultural heritage in decision making. This requirement can go some way to addressing the paradox in the European Community's position whereby the community wishes to conserve and enhance its own cultural identity whilst, at the same time, cultural heritage is usually defined at a local level. The present paper suggests that, given their flexibility, the two European Community directives on environmental assessment constitute a promising opportunity to address this seeming paradox, but that there is a significant gap between legal obligations and the methodological tools to meet them.  相似文献   
4.
This article reviews the application of environmental impact assessment (EIA) procedures and practices to three watershed modification projects situaled in western Canada. These ventures were justified for accelerating regional economic development, and cover the period during which public concerns for protecting the environment rapidly made their way into the national political agenda. An historical account and analysis of the situation, therefore, seems desirable in order to understand the development of EIA processes, practices, and methodologies since the start of construction of the first project in 1961. This study concludes that there has been good progress in predicting and evaluating environmental and related social impacts of watershed modification proposals. However, a number of obstacles need to be overcome before EIA can firmly establish itself as an effective planning tool. These difficulties include jurisdictional confusions and conflicts, division of authority and responsibility in designing and implementing appropriate mitigative and monitoring measures, lack of tested EIA methodologies, and limited availability of qualified human resources. A number of conclusions and suggestions are offered so that future watershed modification proposals may be planned and implemented in a more environmentally sustainable fashion. These include: (1) EIA processes must be completed before irrevocable decisions are made. (2) Any major intrusion into a watershed is likely to impact on some major components of the ecosystem(s). (3) Mitigation costs must form part of the benefit-cost analysis of any project proposal. (4) Interjurisdictional cooperation is imperative where watersheds cross political boundaries. (5) The EIA process is a public process, hence public concerns must be dealt with fairly. (6) The role of science in the EIA process must be at arms length from project proponents and regulators, and allowed to function in the interest of the protection of the environment and public health and safety. The views expressed here are the authors’ own and do not necessarily reflect those of FEARO and/or other government agencies and officials involved in the review of these projects.  相似文献   
5.
This paper provides an introduction to some of the fundamental principles and approaches in environmental economics which are of significance to achieving an integrated sustainability science. The concept of a circular economy, introduced by the late David Pearce in 1990, addresses the interlinkages of the four economic functions of the environment. The environment not only provides amenity values, in addition to being a resource base and a sink for economic activities, it is also a fundamental life-support system. Environmental economists have suggested that, taking these four functions as an analytical starting point, unpriced or underpriced services should be internalised in the economy. In Europe significant advances have been achieved in the pricing of externalities by means of truly interdisciplinary analysis which accounts in detail for the environmental consequences. The monetary estimates reached as a result of such interdisciplinary research are gradually being applied to the economic analysis of environmental policy priorities. Although such figures provide only a partial and incomplete picture of the environmental costs at stake, they support and inform the analysis of the virtues of a circular economy for individual resources as well as for sustainability as a future trajectory.  相似文献   
6.
/ Why are some environmental risks distributed disproportionately in the neighborhoods of the minorities and the poor? A hypothesis was proposed in a recent study that market dynamics contributed to the current environmental inequity. That is, locally unwanted land uses (LULUs) make the host communities home to more poor people and people of color. This hypothesis was allegedly supported by a Houston case study, whereby its author analyzed the postsiting changes of the socioeconomic characteristics of the neighborhoods surrounding solid waste facilities. I argue that such an analysis of postsiting changes alone is insufficient to test the causation hypothesis. Instead, I propose a conceptual framework for analysis of environmental equity dynamics and causation. I suggest that the presiting neighborhood dynamics and the characteristics of control neighborhoods be analyzed as the first test for the causation hypothesis. Furthermore, I present theories of neighborhood change and then examine alternative hypotheses that these theories offer for explaining neighborhood changes and for the roles of LULUs in neighborhood changes. These alternative hypotheses should be examined when analyzing the relationship between LULUs and neighborhood changes in a metropolitan area. Using this framework of analysis, I revisited the Houston case. First, I found no evidence that provided support for the hypothesis that the presence of LULUs made the neighborhoods home to more blacks and poor people, contrary to the conclusion made by the previous study. Second, I examined alternative hypotheses for explaining neighborhood changes-invasion-succession, other push forces, and neighborhood life-cycle; the former two might offer better explanation.KEY WORDS: Environmental equity and justice; Locally unwanted lane uses; Siting; Market dynamics; Invasion-succession; Neighborhood changes  相似文献   
7.
Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials, and thus, the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag+ ratios. Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays, and shifts to both Ag particles and released Ag+ in 48 hr bioassays. Herein, as a continued study, the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically. The cytotoxicity and mechanisms of nano-Ag colloids are dynamic throughout exposure and are derived from both Ag ions and particles. Ag accumulation by E. coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure, and thereafter mainly from intracellular Ag ions. Fe3+ accelerates the oxidative dissolution of nano-Ag colloids, which results in decreasing amounts of Ag particles and particle-related toxicity. Na+ stabilizes nano-Ag colloids, thereby decreasing the bioavailability of Ag particles and particle-related toxicity. Humic acid (HA) binds Ag+ to form Ag+-HA, decreasing ion-related toxicity and binding to the E. coli surface, decreasing particle-related toxicity. HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na+ or Fe3+. The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors, and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.  相似文献   
8.
人工智能技术对长江流域水污染治理的思考   总被引:1,自引:0,他引:1       下载免费PDF全文
随着经济的快速发展和城市化进程的不断加速,促使水污染严重的长江流域需从污染物去除过程的建模与优化、污水处理过程的优化控制、水污染监测系统的构建开展水污染治理研究.传统的水污染处理技术存在污染物去除效率预测精度较低、污水优化控制成本较高、水污染监测滞后效应严重的问题.人工智能技术能够有效克服上述问题,因此通过梳理国内外学者利用人工智能技术在污水污染物去除过程的建模与优化、污水处理过程的优化控制及水污染监测系统的构建等方面的研究成果,为全面加强长江流域水污染治理能力提供科学可靠的技术指导.结果表明:①利用人工神经网络技术(径向基神经网络、多层前馈网络-人工神经网络、多层感知器神经网络)对污水污染物去除过程进行建模与优化,为精确预测长江流域重金属(Cr、Cu)、营养盐(TN、TP)、持久性有机污染物〔PBDEs(多溴二苯醚)、HCH(六氯环己烷)〕的去除率提供重要参考价值.②采用污水处理的自动控制技术与人工智能技术(递归神经网络、支持向量机、模糊神经网络等)构建污水智能控制系统,为长江流域实现高效节能的污水优化控制提供重要的技术指导.③利用在线监测仪器和人工智能技术(小波神经网络、多元线性回归-人工神经网络、叠层去噪自动编码器等)建立水污染智能监测系统,为解决长江流域水污染监测响应滞后问题提供有力的技术支持.因此,人工智能技术对长江流域提高污水污染物去除率,降低污水优化控制成本,提升水污染监测时效性具有重要的推广价值.   相似文献   
9.
针对海洋平台全浸区的腐蚀情况,着重介绍了阴极保护及其原理、种类及特点,监测系统的组成及设计,探讨阴极保护及监测系统对海洋平台水下防腐的应用意义。  相似文献   
10.
以海洋环境中一个非常重要的局部腐蚀形式——低水位加速腐蚀(ALWC)为对象,自其检测、发生原因、防护三个方面就国内外的文献报告进行综述分析。在检测方面,首先介绍了常用的宏观观察这一被动形式,并突出其特征,然后介绍了利用海水中可溶性无机氮含量作为ALWC发生概率预测这一主动形式,分析其优势与不足。在发生原因方面,在对将ALWC认定为一种典型的微生物腐蚀(MIC)形式的认知过程进行介绍之后,重点分析了微生物对ALWC作用机制不清晰的原因,并建议在后续研究中突出动态演变过程,结合高通量测序等分子生物学技术,确定在不同的阶段影响ALWC的关键微生物,且进一步在大气-海水体系下研究典型菌株及其协同作用的影响,提出微生物对ALWC的作用机制。在防护方面,根据新建和已建钢结构设施分别对传统和针对ALWC所具有的MIC与局部腐蚀特性的新型高效防护方法进行了介绍,并分析了防护方法的优缺点。  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