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   366篇
  免费   11篇
安全科学   19篇
废物处理   14篇
环保管理   78篇
综合类   29篇
基础理论   113篇
污染及防治   74篇
评价与监测   32篇
社会与环境   14篇
灾害及防治   4篇
  2023年   3篇
  2022年   2篇
  2021年   3篇
  2019年   3篇
  2018年   7篇
  2017年   6篇
  2016年   9篇
  2015年   12篇
  2014年   10篇
  2013年   35篇
  2012年   12篇
  2011年   16篇
  2010年   9篇
  2009年   14篇
  2008年   21篇
  2007年   13篇
  2006年   20篇
  2005年   15篇
  2004年   14篇
  2003年   14篇
  2002年   16篇
  2001年   11篇
  2000年   6篇
  1999年   3篇
  1998年   8篇
  1997年   5篇
  1996年   5篇
  1995年   12篇
  1994年   7篇
  1993年   9篇
  1992年   8篇
  1991年   1篇
  1990年   7篇
  1989年   2篇
  1987年   2篇
  1986年   6篇
  1985年   3篇
  1984年   5篇
  1983年   1篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1971年   1篇
  1970年   1篇
排序方式: 共有377条查询结果,搜索用时 562 毫秒
241.
Soils down slope of roads have been affected over decades by road salting in the UK uplands. Salt additions to fresh soil facilitate dispersal of organic matter so there is a potential risk of release of DON and DOC to nearby rivers where these run parallel to roads. Over time, however, salting enhances soil pH of naturally acid soils, and thus organic matter degradation through to CO2, thereby, lowering soil organic matter content. In addition any relatively labile organic matter may have already been dispersed. Thus, it is hypothesised that enhanced DOC mobilisation should only be a potential problem if soils not previously exposed to salt become heavily exposed in the future. This paper combines data from field observations and laboratory simulations to elucidate mechanisms controlling organic matter mobilisation processes to determine what controls spatial and temporal trends in DOC concentrations in soil solutions down slope of roads. Organic matter solubilisation is dependent on the degree of road salt exposure soils have had. The laboratory experiment provided evidence that there are two competing effects upon which solubilisation is dependent (a) pH suppression and (b) sodium dispersion. Other organic matter solubility models, if correct, link quite well with the authors "when it's gone, it's gone" hypothesis.  相似文献   
242.
This study identifies and quantifies the spatial variations of metal contamination in water, sediment and biota: the common cockle (Cerastoderma edule) and the Mermaid’s glove sponge (Haliclona oculata), within a heavily anthropogenically impacted semi-enclosed estuarine–coastal area with a low ability to disperse and flush contaminants (Poole Harbour, UK). The results showed that metal contamination was detected in all environmental compartments. Water was polluted with As, and Hg sediment metals were mostly within “the possible effect range” in which adverse effects occasionally occurs. Cockles had considerable concentrations of Ni, Ag and Hg in areas close to pollution sources, and sponges accumulate Cu and Zn with very high magnitude. A systematic monitoring approach that includes biological monitoring techniques, which covers all embayments, is needed, and an integrated management of the semi-enclosed coastal zones should be based on the overall hydrological characteristics of these sensitive areas and their ability to self‐restore which is different than open coastal zones.  相似文献   
243.
244.
Lougheed VL  Butler MG  McEwen DC  Hobbie JE 《Ambio》2011,40(6):589-599
The arctic tundra ponds at the International Biological Program (IBP) site in Barrow, AK, were studied extensively in the 1970s; however, very little aquatic research has been conducted there for over three decades. Due to the rapid climate changes already occurring in northern Alaska, identifying any changes in the ponds’ structure and function over the past 30–40 years can help identify any potential climate-related impacts. Current research on the IBP ponds has revealed significant changes in the physical, chemical, and biological characteristics of these ponds over time. These changes include increased water temperatures, increased water column nutrient concentrations, the presence of at least one new chironomid species, and increased macrophyte cover. However, we have also observed significant annual variation in many measured variables and caution that this variation must be taken into account when attempting to make statements about longer-term change. The Barrow IBP tundra ponds represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure and function. Continued monitoring and protection of these invaluable sites is required to help understand the implications of climate change on freshwater ecosystems in the Arctic.  相似文献   
245.
The goal of this work was to study long-term behavior of anaerobically digested and dewatered sludge (biosolids) in a lagoon under anaerobic and aerobic conditions to determine the stability of the final product as an indicator of its odor potential. Field lagoons were sampled to estimate spatial and temporal variations in the physical-chemical properties and biological stability characteristics such as volatile solids content, accumulated oxygen uptake, and soluble protein content and odorous compound assessment. The analyses of collected data suggest that the surface layer of the lagoon (depth of above 0.15 m) undergoes long-term aerobic oxidation resulting in a higher degree of stabilization in the final product. The subsurface layers (depth 0.15 m below the surface and deeper) are subjected to an anaerobic environment where the conditions favor the initial rapid organic matter degradation within approximately the first year, followed by slow degradation.  相似文献   
246.
Developing a globally responsive Science‐Practitioner‐Humanist model (Lefkowitz, 2008 ) means articulating professional values (supply) and meeting global demand. The United Nations' Millennium Development Goals (MDGs) seek to halve human poverty by 2015 and how organizations respond to this constitutes a formidable demand on Organizational Psychology. A key process for delivering more effective aid is the Paris Declaration on Aid Effectiveness, which seeks collaborative contributions from a plethora of Organizations, including business organizations and professions like ours. We argue that a thoughtful articulation of what Organizational Psychology uniquely stands for, and can offer, is therefore needed. It is proposed that a key mechanism for addressing this challenge is a Task Force, whose functions will include the coordination of institutions within psychology, and linking them to those in development. We describe such a task force and outline its core mission (Reichman, Frese, Schein, Carr, MacLachlan, & Landy, 2008 ). Organizational Psychology's response to poverty reduction should meet Lefkowitz's criteria for developing a more humanist model of science and practice as the MDGs are inherently humanist and values‐based. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
247.
We evaluated the use of the gas exchange rate as an ecologically relevant indicator of chemical stress in avian embryos/eggs. Northern bobwhite quail (Colinus virginianus) were exposed to octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) via feed containing nominal concentrations of 0, 12.5, 50.0, and 125.0 mg kg(-1). Metabolic rates (oxygen consumption) of developing quail eggs were then measured via respirometry to examine potential effects of HMX exposure. Metabolic rates were examined on 5, 9, and 21 d of incubation. Next, concentrations of HMX in embryos/eggs were determined by liquid chromatography-mass spectrometry. Mean (+/-SE) concentrations of HMX in eggs were 21.0+/-5.9, 1113+/-79.0, 3864+/-154.0, and 7426+/-301.1 ng g(-1) in control, low, medium and high dose groups, respectively. There were significant differences in oxygen consumption among the three embryo ages, however differences among the ages were not consistent among dose groups (age x dose group interaction p<0.0001). Oxygen consumption rates did not vary as a function of HMX in embryos (p=0.18). No evidence was observed for alterations of in ovo metabolic rates associated with HMX exposure.  相似文献   
248.
The measurement of volatile organic compound (VOC) emissions from building products and materials by manufacturers and testing laboratories, and the use of the test results for labeling programs, continue to expand. One issue that hinders wide acceptance for chamber product testing is the lack of a reference material to validate test chamber performance. To meet this need, the National Institute of Standards and Technology (NIST) and Virginia Tech (VT) have developed a prototype reference material that emits a single VOC similar to the emissions of a diffusion-controlled building product source with a dynamic emissions profile. The prototype material has undergone extensive testing at NIST and a pilot interlaboratory study (ILS) with four laboratories. The next development step is an evaluation of the prototype source in multiple-sized chambers of 14 laboratories in seven countries. Each laboratory was provided duplicate specimens and a test protocol. Study results identified significant issues related to the need to store the source at a subzero Celsius temperature until tested and possible inconsistencies in large chambers. For laboratories using a small chamber and meeting all the test method criteria, the results were very encouraging with relative standard deviations ranging from 5% to 10% across the laboratories.
Implications: Currently, the chamber performance of laboratories conducting product VOC emissions testing is assessed through interlaboratory studies (ILS) using a source with an unknown emission rate. As a result, laboratory proficiency can only be based on the mean and standard deviation of emission rates measured by the participating ILS laboratories. A reference material with a known emission rate has the potential to provide an independent assessment of laboratory performance as well as improve the quality of interlaboratory studies. Several international laboratories with different chamber testing systems demonstrated the ability to measure the emission rate of such a reference material within an acceptable measurement uncertainty.  相似文献   
249.
Earlier studies by the authors on English soils under grassland strongly supported their hypothesis that soil/plant systems have naturally evolved to conserve nitrogen (N) by having a close match between the dynamics of mineral-N production in soils and the dynamics of plant N requirements. Thus, maximum mineral-N production in soils occurred in spring when plant N requirements were greatest and were very low in mid to late summer. Low temperature and a high C:N ratio of senescing material helped to conserve N in winter, but mobile N was associated with pollution inputs. We test the hypothesis that under the much more arid conditions of Pakistan, soil/plant systems naturally have evolved to conserve mineral-N, especially over the very dry and cooler months between October and February. When soils from a grassland site were incubated at ambient temperatures after removal of plant roots and exclusion of atmospheric N inputs, there was consistent evidence of immobilization of nitrate and immobilization and possibly volatilization of ammonia/ammonium. In the wetter months of July and August, the soil at 0–10 cm depth showed no evidence of significant ammonium-N production in July and only small ammonium production at 10–20 cm depth in August, but was associated with significant nitrate-N immobilization in August. Nitrate leaching only appeared likely towards the end of the rainy season in September. The results strongly suggest that, under grass, the retention of atmospheric N inputs over the long dry periods is regulating the pools of available N in the soils, rather than the N produced by mineralization of soil organic matter.  相似文献   
250.
In a rapidly changing climate, conservation practitioners could better use geodiversity in a broad range of conservation decisions. We explored selected avenues through which this integration might improve decision making and organized them within the adaptive management cycle of assessment, planning, implementation, and monitoring. Geodiversity is seldom referenced in predominant environmental law and policy. With most natural resource agencies mandated to conserve certain categories of species, agency personnel are challenged to find ways to practically implement new directives aimed at coping with climate change while retaining their species‐centered mandate. Ecoregions and ecological classifications provide clear mechanisms to consider geodiversity in plans or decisions, the inclusion of which will help foster the resilience of conservation to climate change. Methods for biodiversity assessment, such as gap analysis, climate change vulnerability analysis, and ecological process modeling, can readily accommodate inclusion of a geophysical component. We adapted others’ approaches for characterizing landscapes along a continuum of climate change vulnerability for the biota they support from resistant, to resilient, to susceptible, and to sensitive and then summarized options for integrating geodiversity into planning in each landscape type. In landscapes that are relatively resistant to climate change, options exist to fully represent geodiversity while ensuring that dynamic ecological processes can change over time. In more susceptible landscapes, strategies aiming to maintain or restore ecosystem resilience and connectivity are paramount. Implementing actions on the ground requires understanding of geophysical constraints on species and an increasingly nimble approach to establishing management and restoration goals. Because decisions that are implemented today will be revisited and amended into the future, increasingly sophisticated forms of monitoring and adaptation will be required to ensure that conservation efforts fully consider the value of geodiversity for supporting biodiversity in the face of a changing climate.  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