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   572篇
  免费   11篇
  国内免费   8篇
安全科学   30篇
废物处理   26篇
环保管理   106篇
综合类   90篇
基础理论   134篇
污染及防治   132篇
评价与监测   50篇
社会与环境   16篇
灾害及防治   7篇
  2023年   5篇
  2022年   4篇
  2021年   12篇
  2020年   5篇
  2019年   8篇
  2018年   17篇
  2017年   17篇
  2016年   29篇
  2015年   18篇
  2014年   19篇
  2013年   45篇
  2012年   27篇
  2011年   36篇
  2010年   28篇
  2009年   28篇
  2008年   37篇
  2007年   32篇
  2006年   25篇
  2005年   32篇
  2004年   19篇
  2003年   21篇
  2002年   22篇
  2001年   11篇
  2000年   11篇
  1999年   10篇
  1998年   2篇
  1997年   6篇
  1996年   4篇
  1995年   8篇
  1994年   2篇
  1993年   4篇
  1992年   8篇
  1991年   3篇
  1990年   6篇
  1989年   5篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1983年   3篇
  1982年   1篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1974年   2篇
  1973年   2篇
  1969年   1篇
排序方式: 共有591条查询结果,搜索用时 11 毫秒
121.
Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers.  相似文献   
122.
Organochlorine pesticides were widely used in the past in Sumas Prairie, British Columbia, Canada. In the 1990s, the hatching success of amphibians from agricultural sites was significantly depressed in the Sumas Prairie compared to reference sites. Therefore, in this study, organochlorine pesticides and polychlorinated biphenyls (PCBs) were measured in eggs of red-legged frogs (Rana aurora) and northwestern salamanders (Ambystoma gracile) from the Sumas Prairie. Egg masses were sampled from three agricultural sites that were exposed to agricultural runoff, and three reference sites that had lower agricultural runoff exposures. Not only was there little difference in contamination between agricultural and reference sites, but the levels of pesticides and PCBs found were lower than the concentrations reported to cause developmental or behavioural problems in amphibians.  相似文献   
123.
The green turtle ( Chelonia mydas ) population that nests at Tortuguero, Costa Rica, is the largest in the Atlantic by at least an order of magnitude. Surveys to monitor the nesting activity on the northern 18 km of the 36-km beach were initiated in 1971 and extended to the entire beach in 1986. From the survey data, we estimated the total number of nesting emergences on the northern 18 km for each year from 1971 through 1996. Evaluation of the trend in nesting emergences indicated a relatively consistent increase from 1971 to the mid-1980s, constant or perhaps decreasing nesting during the late 1980s, and then resumption of an upward trend in the 1990s. Evaluation of trends in sea turtle nesting populations requires many years of data because of the large degree of annual variation in nesting numbers. The trends reported in this study must be evaluated with caution for several reasons. First, if the mean number of nests deposited by each female each year (clutch frequency) varies significantly among years, changes in the number of nesting emergences among years could reflect changes in the number of nesting females, clutch frequency, or both. Second, we only assessed the trend in one segment of the population (mature females), which may or may not represent the trend of the entire green turtle population and which, because of late maturity, may not reflect changes in juvenile mortality for many years. Third, survey frequency, and thus confidence in annual estimates, varied among years. The upward population trend must be assessed from the perspective of the catastrophic decline that the Caribbean green turtle populations have experienced since the arrival of Europeans. If careful management is continued in Costa Rica and adopted throughout the region, the collapse of the Caribbean green turtle populations—which seemed imminent in the 1950s—can be avoided.  相似文献   
124.
As climate change adaptation planning moves beyond short term National Adaptation Programmes of Action (NAPA) to longer-term approaches, it is instructive to review the NAPA process and examine how well it was linked to national development planning. This paper reviews 41 NAPAs submitted by Least Developed Countries (LDCs) to the United Nations Framework Convention on Climate Change (UNFCCC), to assess the NAPA process in terms of NAPAs integration with countries’ national development strategies. The review outlines the actors involved in developing NAPAs and identifies the range of interventions included in countries’ priority adaptation actions. The paper uses the example of population as an issue related to both climate change and national development to assess how it is addressed as part of LDCs’ adaptation and national development agendas. The analysis shows that although countries recognize population pressure as an issue related to the ability to cope with climate change and as a factor hindering progress in meeting development goals, it is not well incorporated into either adaptation planning or in national development strategies. Among the 41 NAPAs, 37 link high and rapid population growth to climate change. Moreover, six NAPAs clearly state that slowing population growth or investments in reproductive health/family planning (RH/FP) should be considered among the country’s priority adaptation actions. Furthermore, two NAPAs actually propose a project with components of RH/FP among their priority adaptation interventions, although none of them has yet been funded. The paper points to structural issues that hamper better alignment between climate change adaptation and national development planning and offers recommendations for longer-term adaptation strategies that better meet the development needs of countries.  相似文献   
125.
126.
Protecting our water resources in terms of quality and quantity is considered one of the big challenges of the twenty-first century, which requires global and multidisciplinary solutions. A specific threat to water resources, in particular, is the increased occurrence and frequency of flood events due to climate change which has significant environmental and socioeconomic impacts. In addition to climate change, flooding (or subsequent erosion and run-off) may be exacerbated by, or result from, land use activities, obstruction of waterways, or urbanization of floodplains, as well as mining and other anthropogenic activities that alter natural flow regimes. Climate change and other anthropogenic induced flood events threaten the quantity of water as well as the quality of ecosystems and associated aquatic life. The quality of water can be significantly reduced through the unintentional distribution of pollutants, damage of infrastructure, and distribution of sediments and suspended materials during flood events. To understand and predict how flood events and associated distribution of pollutants may impact ecosystem and human health, as well as infrastructure, large-scale interdisciplinary collaborative efforts are required, which involve ecotoxicologists, hydrologists, chemists, geoscientists, water engineers, and socioeconomists. The research network “project house water” consists of a number of experts from a wide range of disciplines and was established to improve our current understanding of flood events and associated societal and environmental impacts. The concept of project house and similar seed fund and boost fund projects was established by the RWTH Aachen University within the framework of the German excellence initiative with support of the German research foundation (DFG) to promote and fund interdisciplinary research projects and provide a platform for scientists to collaborate on innovative, challenging research. Project house water consists of six proof-of-concept studies in very diverse and interdisciplinary areas of research (ecotoxicology, water, and chemical process engineering, geography, sociology, economy). The goal is to promote and foster high-quality research in the areas of water research and flood-risk assessments that combine and build off-laboratory experiments with modeling, monitoring, and surveys, as well as the use of applied methods and techniques across a variety of disciplines.  相似文献   
127.
本研究运用满月时收获非木材林产品的当地实践如识,来证明控制叶片分解速率的化学物质随月亮周期而波动,并且这种现象可能已发展为一种植物一食草动物之间的相互关系.当地知识认为,满月期收获的叶片更为耐用.满月期收获的棕榈叶片具有较高的总碳量、半纤维素和碳化合物、而钙的浓度则较低.这些化学上的变化使棕榈叶在满月收获时对食草动物不太敏感且更为耐用.本研究提出了热带植物减少食叶功物食用及影响衰老叶片的分解速度和耐用性(尤其在满月期)的作用机制.本研究认为森林经营中有必要利用天然的生命周期,并为当地人的收获实践提供了科学依据.  相似文献   
128.
Between 1986 and 2009 nine submersible and remote-operated vehicle expeditions were carried out to study the population biology of the coelacanth Latimeria chalumnae in the Comoro Islands, located in the western Indian Ocean. Latimeria live in large overlapping home ranges that can be occupied for as long as 21 years. Most individuals are confined to relatively small home ranges, resting in the same caves during the day. One hundred and forty five coelacanths are individually known, and we estimate the total population size of Grande Comore as approximately 300–400 adult individuals. The local population inhabiting a census area along an 8-km section of coastline remained stable for at least 18 years. Using LASER-assisted observations, we recorded length frequencies between 100 and 200 cm total length and did not encounter smaller-bodied individuals (<100 cm total length). It appears that coelacanth recruitment in the observation areas occur mainly by immigrating adults. We estimate that the mean numbers of deaths and newcomers are 3–4 individuals per year, suggesting that longevity may exceed 100 years. The domestic fishery represents a threat to the long-term survival of coelacanths in the study area. Recent changes in the local fishery include a decrease in the abundance of the un-motorized canoes associated with exploitation of coelacanths and an increase in motorized canoes. Exploitation rates have fallen in recent years, and by 2000, had fallen to lowest ever reported. Finally, future fishery developments are discussed.  相似文献   
129.
Strategies are needed to increase the sustainability of phosphorus (P) fertiliser management in agriculture. This paper reports on the potential of pyrolysis treatment to recycle P from renewable materials previously regarded as wastes. The study used K-edge X-ray absorption near-edge structure (XANES) spectroscopy to examine chemical forms of P in the waste feedstock materials and corresponding biochars (pyrolysis at 480–500 °C) of four ligno-cellulosic, plant-based residues and five relatively P-rich livestock and water-treatment by-products, to acquire information on changes in potential P fertiliser value. Pyrolysis enriched P in the biochars by factors of 1.3–4.3, thus offering wide-ranging P fertiliser potential. XANES spectroscopy revealed hydroxyapatite (HAP) as one of the dominant chemical P compounds in the feedstocks, ranging from 14% (rice husks) to 98% (animal bone) of total P. For most materials, pyrolysis increased the proportion of HAP, and pyrophosphates were generated in several cases. These alterations possibly lead to diversity in the P solubility characteristics of the biochars if used as soil amendments; this is an important property of environmentally sound P fertilisers.  相似文献   
130.
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