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   220篇
  免费   15篇
  国内免费   20篇
安全科学   8篇
废物处理   7篇
环保管理   56篇
综合类   35篇
基础理论   76篇
环境理论   1篇
污染及防治   42篇
评价与监测   12篇
社会与环境   15篇
灾害及防治   3篇
  2023年   7篇
  2022年   9篇
  2021年   10篇
  2020年   2篇
  2019年   6篇
  2018年   13篇
  2017年   15篇
  2016年   17篇
  2015年   18篇
  2014年   10篇
  2013年   18篇
  2012年   17篇
  2011年   15篇
  2010年   16篇
  2009年   7篇
  2008年   16篇
  2007年   18篇
  2006年   12篇
  2005年   3篇
  2004年   1篇
  2003年   2篇
  2002年   6篇
  2001年   4篇
  1999年   2篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   3篇
  1984年   1篇
排序方式: 共有255条查询结果,搜索用时 46 毫秒
211.
There has been widespread interest in using compost to improve the hydrologic functions of degraded soils at construction sites for reducing runoff and increasing infiltration. The objective of this study was to determine the effects of compost amendment rate on saturated hydraulic conductivity (Ks) and water retention in order to identify target compost rates for enhancing soil hydrologic functions. Samples were prepared with three soil textures (sandy loam, silt loam, and sandy clay loam), amended with compost at 0%, 10%, 20%, 30%, 40%, and 50%. All soils were tested at a porosity of 0.5 m3/m3, and the sandy loam was further tested at high (0.55 m3/m3) and low (0.4 m3/m3) porosities. The Ks and water retention data were then used to model infiltration with HYDRUS-1D. With increasing compost amendment rate, Ks and water retention of the mixtures generally increased at the medium porosity level, with more compost needed in heavier soils. As porosity decreased in the sandy loam soil, the amount of compost needed to improve Ks rose from 20% to 50%. Water distribution in pore fractions (gravitational, plant-available, and unavailable water) depended on texture, with only the highest compost rates increasing plant-available water in one soil. Results suggest soil texture should be taken into consideration when choosing a compost rate in order to achieve soil improvement goals. Hydrologic benefits may be limited even at a high rate of compost amendment if soil is compacted.  相似文献   
212.
This study examines the effectiveness of remediating a well-recognized case of heavy metal pollution at Foundry Cove (FC), Hudson River, New York. This tidal freshwater marsh was polluted with battery-factory wastes (1953-1979) and dredged in 1994-1995. Eight years after remediation, dissolved and particulate metals (Cd, Co, Cu, Pb, Ni, and Ag) were found to be lower than levels in the lower Hudson near New York City. Levels of metals (Co, Ni, Cd) on suspended particles were comparatively high. Concentrations of surface sediment Cd throughout the marsh system remain high, but have decreased both in the dredged and undredged areas: Cd was 2.4-230mg/kg dw of sediment in 2005 vs. 109-1500mg/kg in the same area in 1983. The rate of tidal export of Cd from FC has decreased by >300-fold, suggesting that dredging successfully stemmed a major source of Cd to the Hudson River.  相似文献   
213.
214.
Understanding why people make the decisions they do remains a fundamental challenge facing conservation science. Ecosystem service (ES) (a benefit people derive from an ecosystem) approaches to conservation reflect efforts to anticipate people's preferences and influence their environmental behavior. Yet, the design of ES approaches seldom includes psychological theories of human behavior. We sought to alleviate this omission by applying a psychological theory of human values to a cross‐cultural ES assessment. We used interviews and focus groups with fish workers from 28 coral reef fishing communities in 4 countries to qualitatively identify the motivations (i.e., human values) underlying preferences for ES; quantitatively evaluate resource user ES priorities; and identify common patterns among ES motivations and ES priorities (i.e., trade‐offs and synergies). Three key findings are evident that align with human values theory. First, motivations underlying preferences for individual ESs reflected multiple human values within the same value domain (e.g., self‐enhancement). Second, when averaged at community or country scales, the order of ES priorities was consistent. However, the order belied significant variation that existed among individuals. Third, in line with human values theory, ESs related to one another in a consistent pattern; certain service pairs reflected trade‐off relationships (e.g., supporting and provisioning), whereas other service pairs reflected synergistic relationships (e.g., supporting and regulating). Together, these findings help improve understanding of when and why convergence and trade‐offs in people's preferences for ESs occur, and this knowledge can inform the development of suitable conservation actions.  相似文献   
215.
Retraction: Olujobi, O.J., & Olusola-Olujobi, T. (2020). Comparative appraisals of legal and institutional framework governing gas flaring in Nigeria's upstream petroleum sector: How satisfactory?. Environmental Quality Management, https://doi.org/10.1002/tqem.21680 The above article from Environmental Quality Management published online on 3 July 2020 in Wiley Online Library ( wileyonlinelibrary.com ) in Early View has been retracted by agreement between the journal Editor in Chief, Jega Jegatheesan and Wiley Periodicals, LLC. The retraction has been agreed due to unattributed overlap with a previously published article from the same group of authors.  相似文献   
216.
Sulfonylurea herbicides are widely used on a wide range of crops to control weeds. Chevalier® OnePass herbicide is a sulfonylurea herbicide intensively used on cereal crops in Algeria. No information is yet available about the biodegradation of this herbicide or about its effect on the bacterial community of the soil. In this study, we collected an untreated soil sample, and another sample was collected 1 month after treatment with the herbicide. Using a high-resolution melting DNA technique, we have shown that treatment with Chevalier® OnePass herbicide only slightly changed the composition of the whole bacterial community. Two hundred fifty-nine macroscopically different clones were isolated from the untreated and treated soil under both aerobic and microaerobic conditions. The strains were identified by sequencing a conserved fragment of the 16S rRNA gene. The phylogenetic trees constructed using the sequencing results confirmed that the bacterial populations were similar in the two soil samples. Species belonging to the Lysinibacillus, Bacillus, Pseudomonas, and Paenibacillus genera were the most abundant species found. Surprisingly, we found that among ten strains isolated from the treated soil, only six were resistant to the herbicide. Furthermore, bacterial overlay experiments showed that only one resistant strain (related to Stenotrophomonas maltophilia) allowed all the sensitive strains tested to grow in the presence of the herbicide. The other resistant strains allowed only certain sensitive strains to grow. On the basis of these results, we propose that there must be several biodegradation pathways for this sulfonylurea herbicide.  相似文献   
217.
We systematically reviewed the literature on the tragedy of the commons and common‐property resources. We segregated studies by legal management regimes (de jure regimes) and management that develops in practice (de facto regimes) to understand how the structure of regime formation affects the outcome of community management on sustainability of resource use. De facto regimes, developed within the community, are more likely to have positive impacts on the resource. However, de facto regimes are fragile and not resilient in the face of increased population pressure and unregulated markets, and de facto management regimes are less successful where physical exclusion of external agents from resources is more difficult. Yet, formalization or imposition of de jure management regimes can have complicated impacts on sustainability. The imposition of de jure regimes usually has a negative outcome when existing de facto regimes operate at larger scales than the imposed de jure regime. In contrast, de jure regimes have largely positive impacts when the de facto regimes operate at scales smaller than the overlying de jure regimes. Formalization may also be counterproductive because of elite capture and the resulting de facto privatization (that allows elites to effectively exclude others) or de facto open access (where the disenfranchised may resort to theft and elites cannot effectively exclude them). This underscores that although the global movement to formalize community‐management regimes may address some forms of inequity and may produce better outcomes, it does not ensure resource sustainability and may lead to greater marginalization of users. Comparison of governance systems that differentiate between initiatives that legitimize existing de facto regimes and systems that create new de facto regimes, investigations of new top‐down de jure regimes, and studies that further examine different approaches to changing de jure regimes to de facto regimes are avenues for further inquiry.  相似文献   
218.
Transportation of poultry litter out of nutrient limited watersheds such as the Illinois River basin (eastern Oklahoma) is a logical solution for minimizing phosphorus (P) losses from soils to surface waters. Transportation costs are basedon mass of load and distance transported. This study investigated an alternative litter storage technique designed to promote carbon (C) degradation, thereby concentrating nutrients for the purpose of decreasing transportation costs through decreased mass. Poultry litter was stored in 0.90-Mg conical piles under semipermeable tarps and adjusted to 40% moisture content, tested with and without addition of alum (aluminum sulfate). additional study was conducted using 3.6-Mg piles under the same conditions, except tested with and without use of aeration pipes. Samples were analyzed before and after (8 wk) storage. Litter mass degradation (i.e., loss in mass due to organic matter decomposition) was estimated on the basis of changes in litter total P contents. Additional characterization included pH, total nutrients, moisture content, total C, and degree of humification. Litter storage significantly decreased litter mass (16 to 27%), concentrated nutrients such as P and potassium (K) and increased proportion of fulvic and humic acids. The addition of aeration pipes increased mass degradationrelative to piles without aeration pipes. Nitrogen volatilization losses were minimized with alum additions. Increases in P and K concentrations resulted in greater monetary value per unit mass compared with fresh litter. Such increases translate to increased litter shipping distance and cost savings of $17.2 million over 25 yr for litter movement out of eastern Oklahoma.  相似文献   
219.
Suspended solids either as total suspended solids (TSS) or suspended sediment concentration (SSC) is an integral particulate water quality parameter that is important in assessing particle-bound contaminants. At present, nearly all stormwater runoff quality monitoring is performed with automatic samplers in which the sampling intake is typically installed at the bottom of a storm sewer or channel. This method of sampling often results in a less accurate measurement of suspended sediment and associated pollutants due to the vertical variation in particle concentration caused by particle settling. In this study, the inaccuracies associated with sampling by conventional intakes for automatic samplers have been verified by testing with known suspended sediment concentrations and known particle sizes ranging from approximately 20 μm to 355 μm under various flow rates. Experimental results show that, for samples collected at a typical automatic sampler intake position, the ratio of sampled to feed suspended sediment concentration is up to 6600% without an intake strainer and up to 300% with a strainer. When the sampling intake is modified with multiple sampling tubes and fitted with a wing to provide lift (winged arm sampler intake), the accuracy of sampling improves substantially. With this modification, the differences between sampled and feed suspended sediment concentration were more consistent and the sampled to feed concentration ratio was accurate to within 10% for particle sizes up to 250 μm.  相似文献   
220.

Background & Aim

Reproductive carrier screening seeks to identify couples at a high risk of having offspring affected by autosomal recessive and X-linked (XL) conditions. The aim of this paper is to provide a comprehensive overview of existing carrier screening panels by examining their gene content and characteristics, identifying the most common genes/conditions included in these panels, and analyzing their listed prices.

Methods

A comprehensive evaluation of existing carrier screening panels was conducted by searching for web-based content, reviewing information brochures, and establishing direct contact with the providers via email or phone.

Results

Twenty-two panels and their providers were identified with a cumulative total of 2205 unique genes. The number of genes included in these panels varied from 44 to 2054. Only 15 genes (0.7%) were included in all the panels. The carrier frequency of these 15 common genes and their associated conditions varied greatly, but the conditions associated with the genes are “severe”. The price of these 22 panels ranged from $349 to $4320 per couple (USD in 2023). The correlation between the listed price and the number of selected genes among these panels was small and not statistically significant (r = 0.1023, p = 0.6959).

Conclusion

Considerable discrepancies exist among carrier screening panels. Ongoing research and monitoring are necessary to capture the dynamic nature of the carrier screening landscape, providing up-to-date information for clinical practice and informed decision-making.  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