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   410篇
  免费   14篇
  国内免费   2篇
安全科学   13篇
废物处理   22篇
环保管理   126篇
综合类   34篇
基础理论   99篇
污染及防治   87篇
评价与监测   27篇
社会与环境   10篇
灾害及防治   8篇
  2023年   5篇
  2021年   2篇
  2020年   3篇
  2019年   3篇
  2018年   7篇
  2017年   7篇
  2016年   8篇
  2015年   9篇
  2014年   10篇
  2013年   31篇
  2012年   10篇
  2011年   19篇
  2010年   16篇
  2009年   15篇
  2008年   26篇
  2007年   26篇
  2006年   25篇
  2005年   15篇
  2004年   16篇
  2003年   20篇
  2002年   17篇
  2001年   17篇
  2000年   13篇
  1999年   8篇
  1998年   7篇
  1997年   7篇
  1996年   6篇
  1995年   10篇
  1994年   6篇
  1993年   2篇
  1992年   6篇
  1991年   3篇
  1990年   2篇
  1989年   4篇
  1988年   2篇
  1986年   2篇
  1985年   3篇
  1983年   4篇
  1981年   6篇
  1980年   4篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   4篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1966年   1篇
  1935年   1篇
排序方式: 共有426条查询结果,搜索用时 203 毫秒
111.
An in‐well sediment incubator (ISI) was developed to investigate the stability and dynamics of sediment‐associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Herein we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During a seven‐month period in which oxidized Rifle Aquifer background sediment (RABS) were deployed in previously biostimulated wells under iron‐reducing conditions, cell densities of known iron‐reducing bacteria, including Geobacteraceae, increased significantly, showing the microbial community response to local subsurface conditions. Phospholipid fatty acid (PLFA) profiles of RABS following in situ deployment were strikingly similar to those of adjacent sediment cores, suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployment with laboratory‐reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISI to monitor microbial community stability and response to subsurface conditions. © 2009 Wiley Periodicals, Inc.  相似文献   
112.
RaMCo is a prototype version of a decision-support system for coastal-zone management. The model is based on the findings of a multidisiciplinary research program, conducted in Southwest Sulawesi, Indonesia. Different management strategies can be compared on the basis of the short- and long-term consequences. Land-use change has been included in RaMCo in view of the impacts of land-based human activities on the marine environment. The key aspect of the model is a combination of the temporal dynamics of land-use change on the regional (macro-level) scale and spatial dynamics on the local (micro-level) scale. Constrained cellular automata are used to integrate both scale levels. The state changes of the cells depend on the consistency with the macro-scale model, local geographical conditions, and interaction with neighboring cells. In this paper, we discuss the underlying theoretical assumptions of the macro-scale and micro-scale models, some characteristic results for land-use change in the study area, and the validation problem.  相似文献   
113.
Klinefelter syndrome (KS) or 47,XXY is the most common sex chromosome aneuploidy (SCA), occurring at a prevalence of 1 in 600 male pregnancies. Historically, only 25% of individuals with KS came to medical attention, for a range of issues across the life course including under-virilisation at birth, developmental and social concerns in childhood, absence, delay or arrest of puberty in adolescence or infertility in adulthood. Our understanding of the phenotypic spectrum of KS has been largely influenced by this ascertainment bias. With increasing uptake of antenatal noninvasive prenatal testing (NIPT), a corresponding increase in identification of KS has been documented. Population-based longitudinal data from infancy to adulthood on these individuals is lacking, which impedes balanced antenatal genetic counselling and raises issues for prospective parents and clinicians alike.  相似文献   
114.
Large marine protected areas (MPAs) of unprecedented size have recently been established across the global oceans, yet their ability to meet conservation objectives is debated. Key areas of debate include uncertainty over nations’ abilities to enforce fishing bans across vast, remote regions and the intensity of human impacts before and after MPA implementation. We used a recently developed vessel tracking data set (produced using Automatic Identification System detections) to quantify the response of industrial fishing fleets to 5 of the largest MPAs established in the Pacific Ocean since 2013. After their implementation, all 5 MPAs successfully kept industrial fishing effort exceptionally low. Detected fishing effort was already low in 4 of the 5 large MPAs prior to MPA implementation, particularly relative to nearby regions that did not receive formal protection. Our results suggest that these large MPAs may present major conservation opportunities in relatively intact ecosystems with low immediate impact to industrial fisheries, but the large MPAs we considered often did not significantly reduce fishing effort because baseline fishing was typically low. It is yet to be determined how large MPAs may shape global ocean conservation in the future if the footprint of human influence continues to expand. Continued improvement in understanding of how large MPAs interact with industrial fisheries is a crucial step toward defining their role in global ocean management.  相似文献   
115.
116.
117.
Water quality impairment due to excessive nutrients and sediment is a major problem in the United States (U.S.). An important step in the mitigation of impairment in any given water body is determination of pollutant sources and amount. The sheer number of impaired waters and limited resources makes simplistic load estimation methods such as export coefficient (EC) methods attractive. Unfortunately ECs are typically based on small watershed monitoring data, which are very limited and/or often based on data collected from distant watersheds with drastically different conditions. In this research, we seek to improve the accuracy of these nutrient export estimation methods by developing a national database of localized EC for each ecoregion in the U.S. A stochastic sampling methodology loosely based on the Monte‐Carlo technique was used to construct a database of 45 million Soil and Water Assessment Tool (SWAT) simulations. These simulations consider a variety of climate, topography, soils, weather, land use, management, and conservation implementation conditions. SWAT model simulations were successfully validated with edge‐of‐field monitoring data. Simulated nutrient ECs compared favorably with previously published studies. These ECs may be used to rapidly estimate nutrient loading for any small catchment in the U.S. provided the location, area, and land‐use distribution are known.  相似文献   
118.
Recurring disagreements during national preparations to reduce emissions from deforestation and forest degradation (REDD+) are contributing to policy reform at multiple scales. The objectives of this study are to (i) develop a general framework to characterise diverse stakeholder perspectives on REDD+ programme objectives and governance arrangements, and (ii) apply this framework to analyse key stakeholders involved in REDD+ readiness process of Peru: the Inter-ethnic Association for the Development of the Peruvian Rainforest (Asociación Interétnica de Desarrollo de la Selva Peruana, AIDESEP), the Peruvian government and the World Bank. As indigenous peoples strive to maintain their own traditions and priorities, a turbulent readiness process is helping to resolve long-ignored issues of indigenous rights and to make REDD+ programme governance structures more inclusive. The Peruvian government/World Bank approach to REDD+ is incompatible with that of AIDESEP, therefore parallel implementation will be required for them to co-exist. Although a diversity of participants has helped to check and balance the centralization of decision-making power over REDD+ programme development, a history of failed assurances and agreements point to a need to maintain vigilance as new laws, regulations and safeguards are implemented.  相似文献   
119.
Constructed treatment wetlands are a relatively low-cost alternative used for tertiary treatment of wastewater. Phosphorus (P) removal capacity of these wetlands may decline, however, as P is released from the accrued organic soils. Little research has been done on methods to restore the treatment capacity of aging constructed wetlands. One possibility is the seasonal addition of alum during periods of low productivity and nutrient removal. Our 3-mo mesocosm study investigated the effectiveness of alum in immobilizing P during periods of reduced treatment efficiency, as well as the effects on soil biogeochemistry. Eighteen mesocosms were established, triplicate experimental and control units for Typha sp., Schoenoplectus californicus, and submerged aquatic vegetation (SAV) (Najas guadalupensis dominated). Alum was slowly dripped to the water column of the experimental units at a rate of 0.91 g Al m(-2) d(-1) and water quality parameters were monitored. Soil cores were collected at experiment initiation and completion and sectioned into 0- to 5- and 5- to 10-cm intervals for characterization. The alum floc remained in the 0- to 5-cm surface soil, however, soil pH and microbial parameters were impacted throughout the upper 10 cm with the lowest pH found in the Typha treatment. Plant type did not impact most biogeochemical parameters; however, data were more variable in the SAV mesocosms. Amorphous Al was greater in the surface soil of alum-treated mesocosms, inversely correlated with soil pH and microbial biomass P in both soil layers. Microbial activity was also suppressed in the surface soil of alum-treated mesocosms. This research suggests alum may significantly affect the biogeochemistry of treatment wetlands and needs further investigation.  相似文献   
120.
Experiments were conducted to assess the bioavailability of polyclycic aromatic hydrocarbons (PAHs) in soil from a Manufactured Gas Plant site. Three plant species were cultivated for four consecutive growing cycles (28 days each) in soil contaminated with 36.3 microg/g total PAH. During the first growth period, Cucurbita pepo ssp. pepo (zucchini) tissues contained significantly greater quantities of PAHs than did Cucumis sativus (cucumber) and Cucurbita pepo ssp. ovifera (squash). During the first growth cycle, zucchini plants accumulated up to 5.47 times more total PAH than did the other plants, including up to three orders of magnitude greater levels of the six ring PAHs. Over growth cycles 2-4, PAH accumulation by zucchini decreased by 85%, whereas the uptake of the contaminants by cucumber and squash remained relatively constant. Over all four growth cycles, the removal of PAHs by zucchini was still twice that of the other species. Two earthworm species accumulated significantly different amounts of PAH from the soil; Eisenia foetida and Lumbricus terrestris contained 0.204 and 0.084 microg/g total PAH, respectively, but neither species accumulated measurable quantities 5 or 6 ring PAHs. Lastly, in abiotic desorption experiments with an aqueous phase of synthetically prepared organic acid solutions, the release of 3 and 4 ring PAHs from soil was unaffected by the treatments but the desorption of 5-6 ring constituents was increased by up to two orders of magnitude. The data show that not only is the accumulation of weathered PAHs species-specific but also that the bioavailability of individual PAH constituents is highly variable.  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