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   11323篇
  免费   79篇
  国内免费   83篇
安全科学   283篇
废物处理   500篇
环保管理   1430篇
综合类   2459篇
基础理论   2556篇
环境理论   5篇
污染及防治   2951篇
评价与监测   684篇
社会与环境   562篇
灾害及防治   55篇
  2022年   91篇
  2021年   96篇
  2019年   69篇
  2018年   149篇
  2017年   130篇
  2016年   222篇
  2015年   172篇
  2014年   243篇
  2013年   820篇
  2012年   304篇
  2011年   427篇
  2010年   337篇
  2009年   395篇
  2008年   428篇
  2007年   491篇
  2006年   430篇
  2005年   352篇
  2004年   367篇
  2003年   373篇
  2002年   332篇
  2001年   428篇
  2000年   312篇
  1999年   205篇
  1998年   115篇
  1997年   123篇
  1996年   108篇
  1995年   154篇
  1994年   148篇
  1993年   123篇
  1992年   130篇
  1991年   149篇
  1990年   119篇
  1989年   127篇
  1988年   132篇
  1987年   114篇
  1986年   83篇
  1985年   99篇
  1984年   124篇
  1983年   125篇
  1982年   123篇
  1981年   97篇
  1980年   93篇
  1979年   106篇
  1978年   89篇
  1977年   84篇
  1976年   78篇
  1975年   90篇
  1974年   101篇
  1972年   69篇
  1965年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
761.
762.
763.
764.
Historically, Turkey has adopted a reactive approach to natural hazards which resulted in significant losses. However, following the 1999 Kocaeli Earthquake, a more proactive approach has been adopted. This study aims to explore the way this new approach operates on the ground. A multinational and multidisciplinary team conducted a field investigation following the 2011 Van Earthquake to identify lessons to inform healthcare emergency planning in Turkey and elsewhere. The team interviewed selected stakeholders including, healthcare emergency responders, search and rescue services, ambulance services, and health authority representatives, in addition to conducting a focus group. Data were analysed according to an open coding process and SWOT (strength, weakness, opportunity, and threat) analysis. The findings suggest that the approach succeeded in developing a single vision by consolidating official efforts in a more structured way, mobilising many governmental and non-governmental organisations, securing significant amounts of resources including physical and human, and increasing the resilience and flexibility of infrastructure to expand its capacity. However, more attention is required to the development of stronger management procedures and acquisition of further resources.  相似文献   
765.
Current approaches to modelling the fate of persistent organic pollutants (POPs) in the environment have evolved in response to four dominant characteristics of these substances; namely: (1) the presence of POPs in virtually all environmental phases and the ease with which they move from one to the other requires multi-compartmental modelling. Describing transport across phase boundaries becomes as, or even more, important as quantifying transport within the phases; (2) POPs may persist in the environment for many decades. For chemicals that 'have time', concepts such as equilibrium partitioning and steady-state become more important than for short-lived substances whose fate is more controlled by the rates of transformation; (3) measuring POPs is difficult and expensive and observed concentrations of POPs are not available in high spatial or temporal resolution. Consequently, high resolution tends not to be a high priority in POP models; and (4) detrimental effects of POPs often manifest themselves in top predators, which has led to a focus on modelling biotic uptake and transfer within food chains. The task of building a POPs model is viewed as combining the four 'building blocks' of partitioning, transport, transformation and source data with the help of the law of the conservation of mass. Process models, evaluative models, models of real local, regional and global fate, as well as biological uptake models are presented and references to numerous examples are provided. An attempt is made to forecast future directions in the field of POPs modelling. It is expected that modelling techniques that do not rely on quantitative emission estimates as well as approaches that take into account spatial, temporal and climatic variability as well as parameter uncertainty will increase in importance. Finally, the relationship between modelling POPs and models of other pollutant issues is addressed, as are potential interactions between POPs and pollutant issues such as eutrophication, acidification and global climate change.  相似文献   
766.
Pyrethroids are widely used insecticides in both agricultural and urban environments, and their potential movement to surface streams and toxicity to susceptible aquatic species is an emerging concern. Natural surface waters usually contain low levels of dissolved organic matter (DOM). Limited data have shown that DOM preparations can significantly alter the bioavailability and toxicity effects of pyrethroids. However, the importance of these effects in natural waters has not been investigated. In this study we measured uptake and acute toxicity of permethrin and cyfluthrin by Daphnia species in 15 surface water samples. Low levels of DOM (3-20 mg L(-1)) inhibited cyfluthrin uptake by Daphnia magna and acute toxicity to Ceriodaphnia dubia in most samples. For permethrin, the effects of DOM on bioavailability and toxicity were generally not significant. The effects of DOM on bioavailability of cyfluthrin could not be explained from the DOC concentration alone, suggesting that properties of DOM were also important in regulating bioavailability. Regression of K DOC with selected DOM properties revealed significant dependence of K DOC on the carboxylic acid content of DOM. Moreover, concentrations sensed by solid-phase microextraction (SPME) fibers were well correlated with the observed changes in bioaccumulation by D. magna and acute toxicity to C. dubia. Therefore, selective sampling methods such as SPME may be used for measuring the bioavailable concentrations of pyrethroids in waters with naturally occurring DOM levels and predicting the actual toxicity effects.  相似文献   
767.
The importance of wild edible herbaceous species to resource poor households in most rural economies within savannas has been little studied. This is because most of the herbs grow in impoverished species communities and lands, often referred to as 'marginal lands'. The aim of this paper is to conceptualize how the economics of wild edible herbs to households can be used to add value to total livelihoods and conservation within traditional communal areas of South Africa. Analysis of the economics of the consumption of wild edible herbs in Thorndale (Bushbuckridge district) of the Limpopo province is presented. The majority of households consumed wild edible herbs, averaging 15.4 kg dried weight per household per year and valued at $167 per household. The herbs were mostly harvested from uncultivated areas of farms, and rangelands. There was little correlation between household characteristics and the dependence on wild herbs for food. The local people noted a decline in the availability of the species, although not much is known about attempts to cultivate them. The only reasons attributed to the decline were nutrient poor soils and insufficient rains. With this background, developing a local strategy to sustain the species through cultivation by households was found to be feasible. A multiple-use system for the herbs, their improvement and value addition towards commercialization and increased household usage may result in wider acceptance and subsequent cultivation. Species diversity will be enhanced whilst conserving the land on which they grow. This multiple use system may include species roles in soil and water conservation.  相似文献   
768.
769.
Atmospheric xenon radioactive isotope monitoring   总被引:2,自引:0,他引:2  
The Comprehensive Nuclear Test Ban Treaty (CTBT) organisation is implementing a world-wide monitoring network in order to check that the State Signatories comply with the treaty. One of the monitoring facilities consists of an atmospheric noble gas monitoring equipment. According to the requirements annexed in the treaty, the French Atomic Energy Commission (CEA) developed a device, called SPALAX, which automatically extracts xenon from ambient air and makes in situ measurements of the activities of four xenon radioisotopes (131mXe, 133mXe, 133Xe, 135Xe). The originality of this device is noticeable essentially in the gas sample processing method: thanks to the coupling of a gas permeator and of a noble gas specific adsorbent, it can selectively extract and concentrate xenon to more than 3 x 10 E6. This process is carried out continuously without cryogenic cooling, without any regeneration time. The detection of the xenon radioactive isotopes is done automatically by high spectral resolution gamma spectrometry, a robust technology well-suited for on-field instrumentation. In the year 2000, a prototype was involved in an international evaluation exercise directed by the CTBT organisation (CTBTO). This exercise demonstrated that the SPALAX equipment perfectly met the requirements of the CTBTO for such systems. On the basis of the continuous 24-h resolution record of the atmospheric xenon radioactive isotopes concentrations, the SPALAX system also demonstrated that ambient levels of 133Xe can fluctuate quickly from less than the detection limit to over 40 x 10(-3) Bq m(-3). In order to build an industrial version of this equipment, the CEA entered into a partnership with a French engineering company (S.F.I., Marseille, France), which is now able to produce an industrial version of SPALAX, i.e. more compact and more efficient than the prototypes. The 133Xe minimum detectable concentration is 0.15 x 10(-3) Bq m(-3) air per 24 h sampling cycle.  相似文献   
770.
In the context of the desire to steer urban transformation towards sustainability transition, the development of proposals for alternative futures assists policy-makers and practitioners in focusing on impact by organising the various drivers, particularly spatial ones that cause an interactive urban system to transit. This paper presents the methodology that has been developed by the Chair for Urban Development, Munich University of Technology (TUM) as it was working within an inter-disciplinary research team on a project commissioned by the municipality of Nuremberg. The objective of this project was to develop ideas for regenerating the formerly industrial area of Nuremberg West (NW) under the guiding theme of sustainable urban development. This methodology focuses on the development of proposals of positive and possible transformations of NW in the year 2050 based on the analysis of economy, housing and space at various scales and a systematic assessment of trends. These alternative futures became framing and guiding narratives to internalise and anchor the debate in-between the various disciplines involved in this project.  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