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   483篇
  免费   18篇
  国内免费   12篇
安全科学   15篇
废物处理   8篇
环保管理   99篇
综合类   78篇
基础理论   119篇
环境理论   1篇
污染及防治   125篇
评价与监测   28篇
社会与环境   35篇
灾害及防治   5篇
  2024年   1篇
  2023年   3篇
  2022年   13篇
  2021年   13篇
  2020年   7篇
  2019年   8篇
  2018年   22篇
  2017年   23篇
  2016年   29篇
  2015年   24篇
  2014年   22篇
  2013年   45篇
  2012年   30篇
  2011年   47篇
  2010年   20篇
  2009年   20篇
  2008年   27篇
  2007年   19篇
  2006年   17篇
  2005年   13篇
  2004年   13篇
  2003年   13篇
  2002年   19篇
  2001年   12篇
  2000年   4篇
  1999年   5篇
  1998年   3篇
  1996年   2篇
  1995年   7篇
  1994年   2篇
  1993年   3篇
  1992年   2篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1966年   1篇
  1963年   2篇
  1942年   1篇
排序方式: 共有513条查询结果,搜索用时 15 毫秒
111.
To determine the origin of juvenile loggerhead turtles (Caretta caretta) that occupy the Charleston Harbor Entrance Channel at Charleston, South Carolina, USA, mitochondrial DNA restriction-fragment length polymorphisms from this feeding population were compared to haplotypes from candidate nesting populations. Previous studies have defined two major nesting populations in the southeastern USA, one corresponding to Florida and the other to Georgia/South Carolina. These nesting populations are distinguished by both unique haplotypes and frequency distributions of common haplotypes. The frequency distribution of haplotypes in the juvenile feeding-ground population was significantly different from both nesting populations, implying that the feeding aggregate is drawn from two or more nesting populations. Assuming that these turtles are derived exclusively from rookeries in the southeastern USA, a maximum likelihood estimator indicates that approximately half are from the Florida rookery and half are from the northern (Georgia/South Carolina) rookery complex. Because 91% of nesting in the southeastern USA occurs in Florida rookeries and 8% in the northern complex, the 50:50 ratio indicates that juvenile turtles from Georgia and South Carolina tend to feed preferentially near their respective rookery locations. Human encroachment on this feeding habitat may pose an especially high risk to the smaller Georgia/South Carolina rookeries.  相似文献   
112.
Marine fisheries in coastal ecosystems in many areas of the world have historically removed large-bodied individuals, potentially impairing ecosystem functioning and the long-term sustainability of fish populations. Reporting on size-based indicators that link to food-web structure can contribute to ecosystem-based management, but the application of these indicators over large (cross-ecosystem) geographical scales has been limited to either fisheries-dependent catch data or diver-based methods restricted to shallow waters (<20 m) that can misrepresent the abundance of large-bodied fished species. We obtained data on the body-size structure of 82 recreationally or commercially targeted marine demersal teleosts from 2904 deployments of baited remote underwater stereo-video (stereo-BRUV). Sampling was at up to 50 m depth and covered approximately 10,000 km of the continental shelf of Australia. Seascape relief, water depth, and human gravity (i.e., a proxy of human impacts) were the strongest predictors of the probability of occurrence of large fishes and the abundance of fishes above the minimum legal size of capture. No-take marine reserves had a positive effect on the abundance of fishes above legal size, although the effect varied across species groups. In contrast, sublegal fishes were best predicted by gradients in sea surface temperature (mean and variance). In areas of low human impact, large fishes were about three times more likely to be encountered and fishes of legal size were approximately five times more abundant. For conspicuous species groups with contrasting habitat, environmental, and biogeographic affinities, abundance of legal-size fishes typically declined as human impact increased. Our large-scale quantitative analyses highlight the combined importance of seascape complexity, regions with low human footprint, and no-take marine reserves in protecting large-bodied fishes across a broad range of species and ecosystem configurations.  相似文献   
113.
Honey-bees, Apis, are an important model system for investigating the evolution and maintenance of worker sterility. The queen is the main reproductive in a colony. Workers cannot mate, but they can lay unfertilized eggs, which develop into males if reared. Worker reproduction, while common in queenless colonies, is rare in queenright colonies, despite the fact that workers are more related to their own sons than to those of the queen. Evidence that worker sterility is enforced by 'worker policing' is reviewed and worker policing is shown to be widespread in Apis. We then discuss a rare behavioural syndrome, 'anarchy', in which substantial worker production of males occurs in queenright colonies. The level of worker reproduction in these anarchic colonies is far greater than in a normal queenright honey-bee colony. Anarchy is a counterstrategy against worker policing and an example of a 'cheating' strategy invading a cooperative system.  相似文献   
114.
India’s continued development depends on the availability of adequate water. This paper applies a data-driven approach to estimate the intra-annual dynamics of water stress across the central Indian Highlands over the period 2002–2012. We investigate the spatial distribution of water demanding sectors including industry, domestic, irrigation, livestock and thermal power generation. We also examine the vulnerability of urban centers within the study area to water stress. We find that 74 % of the area of the central Indian Highlands experienced water stress (defined as demand exceeding supply) for 4 or more months out of the year. The rabi (winter) season irrigation drives the intra-annual water stress across the landscape. The Godavari basin experiences the most surface water stress while the Ganga and Narmada basins experience water stress due to groundwater deficits as a result of rabi irrigation. All urban centers experience water stress at some time during a year. Urban centers in the Godavari basin are considerably water stressed, for example, Achalpur, Nagpur and Chandrapur experience water stress 8 months out of the year. Irrigation dominates water use accounting for 95 % of the total water demand, with substantial increases in irrigated land over the last decade. Managing land use to promote hydrologic functions will become increasingly important as water stress increases.  相似文献   
115.
ABSTRACT: Vertical attenuation of photosynthetically active radiation (PAR) in clear waters of central Florida theoretically can vary almost 50 percent during a sunny summer day as a result of changing solar elevation. We used a simple formula to partially adjust the attenuation coefficient in Tampa Bay and Charlotte Harbor for changing solar elevation of the direct beam and then used multiple regression analysis to estimate the relative contribution of different water properties or constituents to the adjusted attenuation coefficient, kadj. Color, on an average, was responsible for 18 percent of kadj, chlorophyll a for 21 percent, nonchiorophyll suspended matter for 55 percent, and seawater for the remaining 6 percent. In both estuaries, kadj increased with decreasing salinity as a result of freshwater runoff adding color, suspended matter, and nutrients. Nutrients affected attenuation by stimulating phytoplankton growth and increasing concentrations of chlorophyll a. Reduced nutrient loading to upper Tampa Bay (Hilisborough Bay) in the early to mid-1980's appears to have decreased concentrations of chlorophyll a, increased water clarity, and increased seagrass recolonization. Assuming other attenuating substances remained unchanged, the decrease in the average concentration of chlorophyll a from 30 to 15 μg L?1 would correspond to an increase in the depth of light penetration necessary for seagrass survival (>10 percent incident light) from 1.0 to 1.5 m, which, on a relatively flat sea bed (slope of 2 m/km), would increase the area potentially available for seagram recolonization by 0.25 km2/km of shoreline.  相似文献   
116.
In this paper, the response mechanism of activated sludge exposed to low-dose ozone at less than 20 mg O3 g−1 total suspended solids (TSS) was studied by analyzing the changes in sludge activity and the evolution of C, N, P and metals from sludge following ozonation. The intracellular ATP concentration was not affected at less than 5 mg O3 g−1 TSS and thereafter decreased rapidly to around 60% when the ozone dose increased to 20 mg O3 g−1 TSS. Similarly, the efficiency of sludge solubilization initially changed a little and then increased rapidly to around 30% at an ozone dose of 20 mg O3 g−1 TSS. However, the activities of superoxide dismutase and protease decreased immediately upon exposure to ozone. These findings indicate that ozone firstly destroys the floc, leading to the disruption of the compact aggregates, which does not affect cells viability but induces a decrease in enzyme activities. Ozone then attacks the bacterial cells of the sludge, causing a decrease in cells viability. During ozonation, the content of carbon, nitrogen and phosphorus in the sludge matrix decreased, while the content of these elements in the micro-solids and supernatant gradually increased. Most of the released metals from the sludge matrix were found in the micro-solids.  相似文献   
117.
Environmental Science and Pollution Research - Due to various environmental degradation and natural resource depletion around the world, researchers’ and policymakers’ attention has...  相似文献   
118.
To better understand the fate of metals in the environment, numerous parameters must be studied, such as the soil properties and the different sources of contamination for the organisms. Among bioindicators of soil quality, the garden snail (Cantareus aspersus) integrates multiple sources (e.g. soil, plant) and routes (e.g. digestive, cutaneous) of contamination. However, the contribution of each source on metal bioavailability and how soil properties influence these contributions have never been studied when considering the dynamic process of bioavailability. Using accumulation kinetics, this study showed that the main assimilation source of Cd was lettuce (68 %), whereas the main source of Pb was the soil (90 %). The plant contribution increased in response to a 2-unit soil pH decrease. Unexpectedly, an increase in the soil contribution to metal assimilation accompanied an increase in the organic matter (OM) content of the soil. For both metals, no significant excretion and influence of source on excretion have been modelled either during exposure or depuration. This study highlights how the contribution of different sources to metal bioavailability changes based on changes in soil parameters, such as pH and OM, and the complexity of the processes that modulate metal bioavailability.  相似文献   
119.
120.
This article explores the drivers, benefits, and challenges facing climate change adaptation in the Maldives. It specifically investigates the ??Integrating Climate Change Risks into Resilient Island Planning in the Maldives?? Program, or ICCR, a four-year $9.3 million adaptation project being funded by the Least Developed Countries Fund, Maldivian Government and the United Nations Development Program, and nationally executed by the Ministry of Housing, Transport and Environment of the Maldivian Government. The article asks: what is the perception of coastal adaptation in the Maldives, and what are the potential contributions from the ICCR project? To answer this question, the article summarizes eight primary sectors vulnerable to climate change in the Maldives: human settlements, critical infrastructure, tourism, fisheries, health systems, water, food security, and coral reef biodiversity. It then describes the genesis and background behind the ICCR, which addresses many of these vulnerabilities by demonstrating coastal protection measures. Benefits to the ICCR include improving physical resilience by deploying ??soft?? infrastructure, institutional resilience by training policymakers and enhancing good governance, and community resilience by strengthening community assets and awareness. Challenges include ensuring that adaptation efforts are enough to truly respond to climate vulnerability, lack of coordination, and short-term thinking among business and community leaders.  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