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   1082篇
  免费   16篇
  国内免费   21篇
安全科学   34篇
废物处理   39篇
环保管理   238篇
综合类   131篇
基础理论   208篇
环境理论   2篇
污染及防治   364篇
评价与监测   66篇
社会与环境   33篇
灾害及防治   4篇
  2023年   8篇
  2022年   14篇
  2021年   20篇
  2020年   5篇
  2019年   15篇
  2018年   20篇
  2017年   27篇
  2016年   28篇
  2015年   20篇
  2014年   31篇
  2013年   177篇
  2012年   45篇
  2011年   45篇
  2010年   48篇
  2009年   59篇
  2008年   46篇
  2007年   56篇
  2006年   69篇
  2005年   38篇
  2004年   31篇
  2003年   32篇
  2002年   35篇
  2001年   6篇
  2000年   15篇
  1999年   8篇
  1998年   4篇
  1997年   16篇
  1996年   6篇
  1995年   13篇
  1994年   14篇
  1993年   11篇
  1992年   11篇
  1991年   8篇
  1990年   10篇
  1989年   6篇
  1988年   4篇
  1987年   7篇
  1986年   7篇
  1985年   4篇
  1984年   5篇
  1983年   10篇
  1982年   10篇
  1981年   14篇
  1980年   4篇
  1979年   4篇
  1978年   5篇
  1977年   7篇
  1976年   5篇
  1972年   7篇
  1967年   4篇
排序方式: 共有1119条查询结果,搜索用时 93 毫秒
841.
Given the potent carcinogenic effects of most N-nitroso compounds, the reductive transformation of the common explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to a group of N-nitroso derivatives, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) in the environment have caused concerns among the general public. Questions are arising about whether the same transformations also occur in mammals, and if true, to what extent. This study investigated the N-nitroso derivatives production in the deer mouse GI tract following RDX administration. Findings verified that such transformations do occur in the mammalian GI tract at notable levels: the average MNX concentrations in deer mice stomach were 85 microg/kg and 1318 microg/kg for exposure to 10mg/kg and 100mg/kg diet, respectively. DNX in stomach were 217 microg/kg for the 10mg/kg dose group and 498 microg/kg for the 100mg/kg dose group. Changes in other toxic endpoints including body weight gain, food consumption, organ weight, and behavior were also reported.  相似文献   
842.
Bioavailability and degradation of phenanthrene in compost amended soils   总被引:1,自引:0,他引:1  
Bioavailability in soil of organic xenobiotics such as phenanthrene is limited by mechanisms of diffusion of the xenobiotics within soil micropores and organic matter. The agricultural utilization of compost may reduce the risk connected to organic xenobiotic contamination by means of: (i) a reduction of the bioavailable fraction through an increased adsorption and (ii) an enhanced degradation of the remaining bioavailable fraction through an inoculum of degrading microorganisms. Aim of this work is to test this hypothesis by assessing the effects of compost amendment on the bioavailability and degradation of phenanthrene in soil. Experiments were carried out in both sterilized and non-sterilized conditions, and chemical and microbiological analyses were carried out in order to determine the extent of degradation and bioavailability and to monitor the evolution of the soil micro flora in time. Bioavailability was assessed in sterilized microcosms, in order to assess the physical effects of compost on aging processes without the influence of microbial degradation. Results showed that bioavailability is significantly reduced in soils amended with compost, although no differences were found at the 2 doses of compost studied. In non-sterilized soils the amount of phenanthrene degraded was always higher in the amended soils than in the non-amended one. Microbiological analyses confirmed the presence of a higher number of phenanthrene degraders in the amended soils and in samples of compost alone. These results suggest that compost induces the degradation in soils of easily degradable compounds such as phenanthrene, when the proper bacteria are in the compost; more resistant xenobiotics may instead be trapped by the compost organic matter, thus becoming less available.  相似文献   
843.
Aquifer sediments collected via split-spoon sampling in two new groundwater wells in the 200-UP-1 operable unit at the Hanford Site were characterized and showed typical Ringold Unit E Formation properties dominated by gravel and sand. High iron-oxide content in Fe oxide/clay coatings caused the highest U(VI) adsorption as quantified by batch K(d) values, indicating iron oxides are the key solid adsorbent in the 200-UP-1 sediments that affect U(VI) fate and mobility. Even though U(VI) adsorption on the gravel-sized fraction of the sediments is considered to be negligible, careful characterization should be conducted to determine U(VI) adsorption on gravel, because of presence of Fe oxides coatings and diffusion-controlled adsorption into the gravel particles' interior surfaces. A linear adsorption isotherm was observed up to 10(-6) M (238 microg/L) of total U(VI) concentration in batch U(VI) adsorption tests with varying total U(VI) concentrations in spiked groundwater. U(VI) adsorption decreased with increasing concentrations of dissolved carbonate, because strong anionic aqueous uranium-carbonate complexes formed at high pH and high alkalinity conditions. Noticeable uranium desorption hysteresis was observed in a flow-through column experiment, suggesting that desorption K(d) values for aged uranium-contaminated sediments at the Hanford Site can be larger than adsorption K(d) values determined in short-term laboratory experiments and slow uranium release from contaminated sediments into the groundwater is expected.  相似文献   
844.
845.
加速老化的相关性与使用寿命预测   总被引:3,自引:0,他引:3  
重点论述了材料老化过程中环境因素对老化周期长短的影响以及造成的原因等。通过对人工加速老化及其加速老化和自然老化相关性的说明,进一步阐述了可降低这种相关性的诸多因素,以及这些因素对老化结果的影响程度,以便进一步研究确定人工加速老化方法的可行性,为材料老化的研究提供了较为具体,实际的方法和步骤,文中给出了如何遵照了ASTM D 632标准研究确定老化方法的流程图,需要考虑的因素等等,这对老化研究工作者提供了有效的捷径。  相似文献   
846.
The major forest nonpoint source control programs in the West are largely regulatory, either under forest practices acts (California, Idaho, New Mexico, Nevada, Oregon, and Washington) or a streamside management act (Montana). These programs and the specific rules they enforce continue to undergo intensive scrutiny. Still, the questions are the same for these regulatory programs as for states that base nonpoint source control on voluntary BMPs (Arizona, Colorado, Utah, Wyoming). Are the rules or BMPs being applied, and are they effective in reducing nonpoint source pollution to levels that protect beneficial uses of water? The level of debate about forestry in the West has resulted in detailed monitoring and research to answer these questions. In the past, state agencies have assumed levels of BMP compliance based on the percent of operations without enforcement actions. These estimates are being replaced by statistically valid and reproducible monitoring of forest practices rules and BMP compliance levels. BMP effectiveness is being assessed using both qualitative and quantitative methods. This can involve field assessments, process-based research, and control watershed studies. Some trend monitoring is also beginning. With the regional implementation rate for forestry BMPs at about 94% and rising, it is likely that effectiveness testing will continue to be a priority and consume the majority of assessment resources for this region.  相似文献   
847.
Conservation of migratory species exhibiting wide-ranging and multidimensional behaviors is challenged by management efforts that only utilize horizontal movements or produce static spatial–temporal products. For the deep-diving, critically endangered eastern Pacific leatherback turtle, tools that predict where turtles have high risks of fisheries interactions are urgently needed to prevent further population decline. We incorporated horizontal–vertical movement model results with spatial–temporal kernel density estimates and threat data (gear-specific fishing) to develop monthly maps of spatial risk. Specifically, we applied multistate hidden Markov models to a biotelemetry data set (n = 28 leatherback tracks, 2004–2007). Tracks with dive information were used to characterize turtle behavior as belonging to 1 of 3 states (transiting, residential with mixed diving, and residential with deep diving). Recent fishing effort data from Global Fishing Watch were integrated with predicted behaviors and monthly space-use estimates to create maps of relative risk of turtle–fisheries interactions. Drifting (pelagic) longline fishing gear had the highest average monthly fishing effort in the study region, and risk indices showed this gear to also have the greatest potential for high-risk interactions with turtles in a residential, deep-diving behavioral state. Monthly relative risk surfaces for all gears and behaviors were added to South Pacific TurtleWatch (SPTW) ( https://www.upwell.org/sptw ), a dynamic management tool for this leatherback population. These modifications will refine SPTW's capability to provide important predictions of potential high-risk bycatch areas for turtles undertaking specific behaviors. Our results demonstrate how multidimensional movement data, spatial–temporal density estimates, and threat data can be used to create a unique conservation tool. These methods serve as a framework for incorporating behavior into similar tools for other aquatic, aerial, and terrestrial taxa with multidimensional movement behaviors.  相似文献   
848.
When a pollution incident occurs, there can be impact liability and/or remediation liability on the polluter. The impact liability pays for the loss of life and property due to pollution. The remediation liability is to pay for remediating the environment in accordance with applicable laws and regulations. If there is only one polluter in a pollution incident, the entire liability can be placed on the sole polluter. However, liability allocation becomes complex when there are multiple polluters. To allocate the fractional remediation liability among multiple polluters, it is important to identify the factors that determine the cost of remediation so that a just distribution of liability can be made based on the contribution of each polluting party to the factors identified. Along with factors such as “quantity of the chemical released by the polluter,” “distribution of the chemical in the environmental medium,” “persistence of the chemical in the environmental medium,” and so forth, the ease with which the chemical pollutant can be separated from the contaminated medium, which we name as “remediability,” is important in deciding the remediation liability. The “remediability” of a chemical is critical in selecting the remediation technologies to be adopted and, consequently, in deciding the cost of remediation. Determination of a remediability score (RS) for each “chemical–environment medium” pair will help in quantifying the ease with which the site can be remediated. The score is envisaged on a 0–100 scale. The higher the score, the more difficult it is to remediate the chemical in the environmental medium under consideration. The score is estimated based on a set of predetermined factors that are characteristic to the technologies available for remediation. The factors are then subjected to a Delphi process to arrive at the weights. The overall RS is determined by determining the weighted impact of the identified factors after the normalization of the magnitudes of factors.  相似文献   
849.
Sickness behaviors constitute an array of symptoms exhibited by an animal during the course of an infection, including reduced activity, reduced food and water intake, and reduced social interactions. It is hypothesized that these symptoms enable reallocation of finite energy resources to fight infection. In this way, by focusing energy on healing, available resources are being removed from other activities, potentially reducing adaptive opportunities, such as mating. Hence, to achieve increased reproductive success, animals might be able to adjust the expression of sickness behaviors to their environmental circumstances. While abiotic conditions such as temperature and season can modulate sickness behaviors, no studies in passerines have linked modulation of sickness behaviors to social settings. Here, it is demonstrated that social surroundings affect the extent to which animals exhibit symptoms of sickness. After an immune challenge, zebra finches kept in isolation markedly reduced activity, but those kept in a colony setting did not. The same trend is verified when looking at the time they spent resting. Additionally, a proinflammatory cytokine (interleukin-6) was quantified in plasma samples and all animals that had been immune challenged showed increased levels of this marker, showing that the physiological response was similar. Hence, birds in a social context were able to overcome the behavioral, but not physiological, symptoms usually associated with an inflammatory response. These findings suggest a trade-off between allowing the body to respond to an infection and taking advantage of being in a social situation.  相似文献   
850.
For elaboration of strategy and spatial planning of sustainable coastal regions development it??s very important to know a real potential of development of the region. As parameter, which is comprehensively characterized marine economic, political and military power of the coastal region, it is possible to use the marine economy potential with comprehensive estimations of socio-economic, political, environment and military profits (damages) from coastal planning decisions. Some results, including the European and Russian coastal regions are presented.  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