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   1836篇
  免费   9篇
  国内免费   3篇
安全科学   35篇
废物处理   58篇
环保管理   104篇
综合类   648篇
基础理论   311篇
环境理论   7篇
污染及防治   529篇
评价与监测   84篇
社会与环境   70篇
灾害及防治   2篇
  2021年   15篇
  2020年   13篇
  2019年   15篇
  2018年   31篇
  2017年   38篇
  2016年   37篇
  2015年   34篇
  2014年   44篇
  2013年   93篇
  2012年   38篇
  2011年   73篇
  2010年   51篇
  2009年   58篇
  2008年   86篇
  2007年   82篇
  2006年   67篇
  2005年   65篇
  2004年   39篇
  2003年   45篇
  2002年   45篇
  2001年   56篇
  2000年   38篇
  1999年   27篇
  1998年   17篇
  1997年   18篇
  1996年   17篇
  1995年   18篇
  1994年   30篇
  1993年   13篇
  1991年   15篇
  1989年   12篇
  1984年   14篇
  1981年   16篇
  1975年   12篇
  1974年   12篇
  1969年   14篇
  1968年   13篇
  1967年   15篇
  1966年   23篇
  1965年   29篇
  1964年   16篇
  1963年   25篇
  1962年   22篇
  1961年   30篇
  1960年   20篇
  1959年   21篇
  1958年   13篇
  1957年   24篇
  1956年   16篇
  1955年   16篇
排序方式: 共有1848条查询结果,搜索用时 359 毫秒
751.
Population growth and social/technological developments have resulted in the buildup of carbon dioxide (CO2) in the atmosphere and oceans to the extent that we now see changes in the earth’s climate and ocean chemistry. Ocean acidification is one consequence of these changes, and it is known with certainty that it will continue to increase as we emit more CO2 into the atmosphere. Ocean acidification is a global issue likely to impact marine organisms, food webs and ecosystems and to be most severely experienced by the people who depend on the goods and services the ocean provides at regional and local levels. However, research is in its infancy and the available data on biological impacts are complex (e.g., species-specific response). Educating future generations on the certainties and uncertainties of the emerging science of ocean acidification and its complex consequences for marine species and ecosystems can provide insights that will help assessing the need to mitigate and/or adapt to future global change. This article aims to present different educational approaches, the different material available and highlight the future challenges of ocean acidification education for both educators and marine biologists.  相似文献   
752.
Levels of polybrominated diphenyl ether (PBDE) flame retardants have been increasing in humans and the environment for the past few decades. Human levels are markedly higher in the US than Europe. Although food appears to be a significant route of intake, food PBDE levels are not substantially higher in the US than Europe. House and office dust appear to be major routes of exposure with air believed to usually provide a lesser route of intake. Because there are very few measurements of airborne PBDE that have been performed in relevant microenvironments in the US, increased efforts to assess airborne PBDE in the US as sources of exposure are needed. This study reports, for the first time from a Southwestern US city in Texas, the results of measurements of airborne PBDE in multiple locations, two outdoor and six indoor (residential and office) from active air sampling with collection of a combination of both vapor- and particulate-phase PBDE. Higher PBDE levels were measured in indoor than outdoor air, which confirms previous findings. Of 11 measured congeners including BDE 209, total PBDE levels in two outdoor air samples were 112 and 125 pg m?3 and the indoor air levels ranged from 175 to 1232 pg m?3 with a median of 572 pg m?3. These findings suggest that sources of air contamination with PBDE may be similar in Texas as elsewhere in North America. However, more sampling is required to (1) better determine if this is the case and (2) attempt to characterize potential sources of PBDE contamination in both indoor and outdoor air by analysis of congener patterns.  相似文献   
753.
Partitioning of native or anthropogenic heavy metals in solid and solution phases of soil is a result of network of several physico‐chemical reactions. The attainment of equilibrium between two phases is also regulated by biochemical processes. For practical purposes, the bioavailability of metal present in soil is predominantly regulated by the soil solution phase which is in dynamic equilibrium with the solid phase. The results of a model laboratory and greenhouse growth experiments have been used to investigate the effect of Cd‐ion concentrations (either in soil solution or in nutrient solution) on the growth and activities of microorganisms. The soil solution has been simulated by preparing a suspension of soil with 0.1 M NaNO3 (1: 2.5) equilibrated for two hours. Important conclusions are as follows:

Increase in Cd‐ion concentration in soil solution or in nutrient solution induces corresponding adverse effect on the growth and activities of microorganisms. Thus, it seems that Cd‐ion concentration is a more sensitive indicator for assessing the effect of metal pollution upon the growth and activities of soil microorganisms in comparison to total Cd contents.

During active microbial growth phase, a large part of the organically bound Cd was released in the soil solution which is largely bioavailable. This process is termed as mobilisation. There was momentary increase of Cd‐ion concentration in soil solution which intoxicated the growing organisms. After this stage, the Cd ions from the solution phase were removed by the newly formed solid phase (nonviable biomass) and were transformed in non‐available form. This process is termed as immobilisation.

The consequences and importance of these results for practical agriculture and in deciding the limits or guidelines on the maximum tolerable metal load in soils are discussed.  相似文献   
754.
To check the effect of possible deposition of organic contaminants in northern regions of the Earth due to atmospheric transport snow samples were collected in early March in 6 places in Russia and 4 in Finland including arctic territories. GC‐MS was used as an analytical tool to identify and quantify individual organic compounds belonging to the various classes. As a result more than 250 compounds were detected. The possible presence of more than 100 other priority pollutants from the US EPA list was also screened.  相似文献   
755.
Intake of many persistent organic pollutants (POPs) including dioxins, dibenzofurans and PCBs is almost exclusively from gastrointestinal ingestion of animal fats in the diet. With polybrominated diphenyl ether (PBDE) brominated flame retardants (BFRs), no consensus exists at present as to the extent of intake from food, from indoor dust or other routes of intake. Vegans, or pure vegetarians, were previously found to have low body burden of dioxins and dibenzofurans in blood. Data reported here for the first time show a trend towards lower PBDE levels with longer time periods without ingestion of food of animal origin in 8 adult residents of the United States. A stronger relationship between lower PBDE levels and time without meat, specifically, is consistent with substantial PBDE intake from meat relative to fish or dairy products in Americans. These vegans had somewhat lower PBDE levels with a range 12.4–127 and a median 23.9?ppb than published reports of US general population samples which had a range of 4–366 and median of 26?ppb. Our findings suggest that food of animal origin may be a major but not the sole contributor to human body burden of PBDEs.  相似文献   
756.
An indicator can be considered any measure – quantitative or qualitative – that seeks to produce information on an issue of interest. Safety indicators can play a key role in providing information on organizational performance, motivating people to work on safety and increasing organizational potential for safety. We will describe the challenges of monitoring and driving system safety. Currently, the same lead indicators are used – explicitly or implicitly – for both purposes. The fact that the selection and use of safety performance indicators is always based on a certain understanding (a model) of the sociotechnical system and safety is often forgotten. We present a theoretical framework for utilizing safety performance indicators in safety–critical organizations that incorporates three types of safety performance indicators – outcome, monitor and drive indicators. We provide examples of each type of indicator and discuss the application of the framework in organizational safety management. We argue that outcome indicators are lag indicators since outcomes always follow something; they are the consequences arising from multiple other situational and contextual factors. Monitor and drive indicators are lead indicators. The main function of the drive indicators is to direct the sociotechnical activity in the organization by motivating certain safety-related activities. Monitor indicators provide a view on the dynamics of the organization: the practices, abilities, skills and motivation of the personnel – the organizational potential for safety. We conclude that organizations should better acknowledge the significance of monitor and drive indicators in safety management.  相似文献   
757.
Non-parametric statistical tests are commonly used in the behavioral sciences. Researchers need to be aware that non-parameteric methods involving ranks can perform unreliably as a result of very small amounts of noise added in the storage and manipulation of values by computers, causing spurious reduction in the number of ties. In order to avoid this problem, researchers should round values to an appropriate number of decimal places prior to the ranking procedure to ensure that data points whose values cannot be separated according to the precision of their measurement are recorded as having identical rank. We also recommend exact rather than asymptotic evaluation of p values in non-parametric statistical tests.  相似文献   
758.
Different uptake routes of contaminants were analysed with focus on particle-bound pollutants. Bioavailability of cadmium was determined with quantitative mRNA-analysis using the expression of the “cadmium responsive gene” cdr- in Caenorhabditis elegans. Comparable experiments were performed with fluoranthene as organic pollutant. The exposure in medium was compared with and without bacteria as food particles. Both bioaccumulation and toxic effects were most influenced via the food exposure. Inorganic particles increased also the uptake of cadmium, but significantly less than food or mixtures of food and inorganic particles. The exposure of fluoranthene reduced the reproduction of the nematodes, if a gene expression threshold was exceeded. However, bioavailabilty of fluoranthene via food particles caused a faster response of the cyp-expression. Thus means, the internal availability is crucial influenced by the uptake route.  相似文献   
759.
The genetic structure of benthic marine invertebrates is often described as “chaotic” when genetic structure cannot be explained and barriers to dispersal and gene flow cannot be identified. Here, chaotic patterns of genetic structure for the polychaete Pygospio elegans (Claparède) sampled at 16 locations from the heterogeneous Isefjord–Roskilde Fjord estuary complex in Denmark were found. There was no isolation by distance, and the geography of the estuary complex did not seem to pose a barrier to dispersal and gene flow in this species. We investigated whether characteristics of the environment could be related to the genetic structure and possibly restrict gene flow in this species. Additionally, since P. elegans is poecilogonous, producing larvae with different pelagic developmental periods, we investigated whether observed developmental modes in the samples might clarify the genetic patterns. None of the tested factors explained the population genetic structure. However, a high degree of relatedness among individuals in almost all samples was found. Samples with a larger percentage of young individuals had more related individuals, suggesting that different cohorts could be comprised of individuals with different degrees of relatedness. Relatedness within a site could be increased by limited larval dispersal, collective dispersal of related larvae, sweepstakes reproductive success, or asexual reproduction, but distinguishing between these requires further study. Using a “seascape genetics” approach allowed us to investigate some of the numerous potential factors that could influence population genetic structure in a poecilogonous species.  相似文献   
760.
Environment Systems and Decisions - Organizational and technical approaches have proven successful in increasing the performance and preventing risks at socio-technical systems at all scales....  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