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   1810篇
  免费   28篇
  国内免费   15篇
安全科学   53篇
废物处理   67篇
环保管理   298篇
综合类   303篇
基础理论   431篇
环境理论   4篇
污染及防治   475篇
评价与监测   134篇
社会与环境   83篇
灾害及防治   5篇
  2023年   22篇
  2022年   20篇
  2021年   25篇
  2020年   24篇
  2019年   23篇
  2018年   39篇
  2017年   47篇
  2016年   43篇
  2015年   46篇
  2014年   50篇
  2013年   127篇
  2012年   73篇
  2011年   108篇
  2010年   77篇
  2009年   92篇
  2008年   95篇
  2007年   115篇
  2006年   84篇
  2005年   73篇
  2004年   72篇
  2003年   68篇
  2002年   78篇
  2001年   33篇
  2000年   28篇
  1999年   18篇
  1998年   19篇
  1997年   23篇
  1996年   18篇
  1995年   23篇
  1994年   25篇
  1993年   13篇
  1992年   16篇
  1991年   15篇
  1990年   12篇
  1989年   12篇
  1988年   17篇
  1987年   12篇
  1986年   15篇
  1984年   8篇
  1983年   10篇
  1982年   11篇
  1981年   9篇
  1980年   7篇
  1979年   10篇
  1978年   7篇
  1977年   5篇
  1976年   6篇
  1974年   6篇
  1955年   5篇
  1954年   8篇
排序方式: 共有1853条查询结果,搜索用时 11 毫秒
141.
Sediment samples and soils along the coast line of the Adriatic Sea were sampled along a transect near the coast line at Zadar/Croatia, ranging from north-western suburbs via the historical centre and the industrial area to south-east suburbs. The sediments were dominated by carbonates and clay minerals, and contaminations with Cd–Cu–Pb–Zn–TOC (total organic carbon) at the historical centre and the industrial site were detected, as well as P and Mo input at the mouth of a small creek, probably from agriculture. No trends between the composition of surface and subsurface sea sediments were seen. At the historic harbour site, total element concentrations versus grain size showed a minimum in the fine silt fraction for most of the elements analysed. The soil samples behind the shoreline were not carbonaceous, but dominated by Fe–Al– oxides, some contained high levels of Be–Cd–Cu–Sn–Zn. Surprisingly, high TOC values within the soils might be assigned to human impacts, not to humus. Contrary to data from street dust samples from Seoul city/Korea, which were measured within our laboratory at the same time, Pt–Ir–Au were at ambient levels due to the limited use of catalysts in cars in the Zadar area at the time of sampling.  相似文献   
142.
We analyzed whether decision‐making triggers increase accountability of adaptive‐management plans. Triggers are prenegotiated commitments in an adaptive‐management plan that specify what actions are to be taken and when on the basis of information obtained from monitoring. Triggers improve certainty that particular actions will be taken by agencies in the future. We conducted an in‐depth, qualitative review of the political and legal contexts of adaptive management and its application by U.S. federal agencies. Agencies must satisfy the judiciary that adaptive‐management plans meet substantive legal standards and comply with the U.S. National Environmental Policy Act. We examined 3 cases in which triggers were used in adaptive‐management plans: salmon (Oncorhynchus spp.) in the Columbia River, oil and gas development by the Bureau of Land Management, and a habitat conservation plan under the U.S. Endangered Species Act. In all the cases, key aspects of adaptive management, including controls and preidentified feedback loops, were not incorporated in the plans. Monitoring and triggered mitigation actions were limited in their enforceability, which was contingent on several factors, including which laws applied in each case and the degree of specificity in how triggers were written into plans. Other controversial aspects of these plans revolved around who designed, conducted, interpreted, and funded monitoring programs. Additional contentious issues were the level of precaution associated with trigger mechanisms and the definition of ecological baselines used as points of comparison. Despite these challenges, triggers can be used to increase accountability, by predefining points at which an adaptive management plan will be revisited and reevaluated, and thus improve the application of adaptive management in its complicated political and legal context. Detonadores de la Toma de Decisiones en el Manejo Adaptativo  相似文献   
143.
Understanding the impact of environmental stressors on predator activity is a prerequisite to understanding the underlying mechanisms shaping community structure. The nemertean Prosorhochmus nelsoni is a common predator in the mid-intertidal zone on rocky shores along the Chilean coast, where it can reach very high abundances (up to 260 ind m−2) in algal turfs, algal crusts, barnacle crusts, and mixed substrata. Tidal and diurnal scans revealed that the activity of P. nelsoni is primarily restricted to night and early-morning low tides and is relatively low when air temperatures are high. On average, larger worms crawled faster than smaller worms, with their maximum velocity being influenced by substratum type. Their estimated rate of predation is 0.092 prey items nemertean−1 day−1, just below the laboratory rate of ~0.2 amphipods nemertean−1 day−1 previously estimated for this species. P. nelsoni consumes a diverse spectrum of prey items (i.e., amphipods, isopods, decapods, barnacles, and dipterans) and is possibly exerting a significant influence on its prey populations. We suggest that the opportunistic predatory behavior of this intertidal predator is caused by the trade-off between immediate persistence (e.g., avoidance of desiccation) and long-term survival through successful foraging.  相似文献   
144.
The rehabilitation of the former nuclear test site at Maralinga involved (among other processes) the removal of contaminated soil from an area of approximately 2.5 km2. The two most stringent rehabilitation criteria required measurements to ensure that no radioactive particle exceeding 100 kBq of 241Am activity, and no area of 1 ha exceeding 3 kBq/m2 of 241Am activity, remained in the rehabilitated area. The project timetable required that the area be scanned at the rate of approximately 3 ha/day. Two vehicle-mounted detection systems were developed and constructed to obtain the necessary measurements in the available timeframe. The scientific basis for the designs are presented, together with details of the selected equipment and technical solutions found. The performance of this equipment in the field is discussed in terms of both its scientific and technical operation. Based on the experience gained at Maralinga, improved versions of this equipment were produced under contract for the People's Republic of China.  相似文献   
145.
This paper discusses the perceived impacts of weather-related extreme events on different social groups in New Delhi, India. Using network statistics and scenario analysis with the Fuzzy Cognitive Mapping as part of a vulnerability analysis, the investigation provides quantitative and qualitative measures to compare impacts and adaptation strategies for different social groups. Impacts of rain events and heat waves are considered and differ across groups. Rain events affect the lower income classes more, while heat waves are the bigger burden for higher income classes. Overall, the strength of perceived impacts is larger for lower income classes, directly threatening their daily incomes. Urban managers have no immediate feedback on their livelihood, but often refer to health issues. The strongest effect on ameliorating burdens is investments in schemes to ease traffic, e.g., by improving the sewage and drainage infrastructure paired with other supply side measures to enable transport of goods for lower income classes during rain. During heat events, improving the water supply situation would reduce burden for all, while constant electricity supply is an effective means in reducing burden for the higher income classes in particular. Our analysis suggests that improvements in the water supply and sewage infrastructure would be the most suitable first step to initiate a well-planned adaptation strategy for all social groups.  相似文献   
146.
Abandoned peat extraction areas are continuous emitters of GHGs; hence, abandonment of peat extraction areas should immediately be followed by conversion to an appropriate after-use. Our primary aim was to clarify the atmospheric impact of reed canary grass (RCG, Phalaris arundinacea L.) cultivation on an abandoned peat extraction area and to compare it to other after-treatment alternatives. We performed a life-cycle assessment for five different after-use options for a drained organic soil withdrawn from peat extraction: (I) bare peat soil (no management), (II) non-fertilised Phalaris cultivation, (III) fertilised Phalaris cultivation, (IV) afforestation, and (V) rewetting. Our results showed that on average the non-fertilised and fertilised Phalaris alternatives had a cooling effect on the atmosphere (?10,837 and ?477 kg CO2-eq ha?1 year?1, respectively), whereas afforestation, rewetting, and no-management alternatives contributed to global warming (9,511, 8,195, and 2,529 kg CO2-eq ha?1 year?1, respectively). The main components influencing the global warming potential of different after-use alternatives were site GHG emissions, carbon assimilation by plants, and emissions from combustion, while management-related emissions played a relatively minor role. The results of this study indicate that, from the perspective of atmospheric impact, the most suitable after-use option for an abandoned peat extraction area is cultivation of RCG.  相似文献   
147.
In the present study, we identified and examined the spatial trends, sources and dietary relationships of bioaccumulative perfluorinated sulfonate (PFSA; C(6), C(8), and C(10) chain lengths) and carboxylate (PFCA; C(6) to C(15) chain lengths) contaminants, as well as precursor compounds including several perfluorinated sulfonamides, and fluorotelomer acids and alcohols, in individual eggs (collected in 2008) from four gull species [glaucous-winged (Larus glaucescens), California (Larus californicus), ring-billed (Larus delawarensis) and herring (Larus argentatus) gulls] from 15 marine and freshwater colony sites in provinces across Canada. The pattern of PFSAs was dominated by perfluorooctane sulfonate (PFOS; >89% of ΣPFSA concentration) regardless of egg collection location. The highest ΣPFSA concentrations were found in the eggs collected in the urbanized areas in the Great Lakes and the St. Lawrence River area [Big Chicken Island 308 ng/g ww, Toronto Harbour 486 ng/g ww, and Ile Deslauriers (HG) 299 ng/g ww]. Also, eggs from all freshwater colony sites had higher ΣPFSA concentrations, which were significant (p<0.05) in many cases, compared to the marine sites with the exception of the Sable Island colony in Atlantic Canada off the coast of Nova Scotia. C(6) to C(15) chain length PFCAs were detected in the eggs, although the pattern was variable among the 15 sites, where PFUnA and PFTrA dominated the pattern for most colonies. Like the ΣPFSA, the highest concentrations of ΣPFCA were found in the eggs from Big Chicken Island, Toronto Harbour, Ile Deslauriers (HG), and Sable Island, although not all freshwater sites had higher concentrations compared to marine sites. Dietary tracers [δ(15)N and δ(13)C stable isotopes (SIs)] revealed that PFSA and PFCA exposure is colony dependent. SI signatures suggested that gulls from most marine colony sites were exposed to PFCs via marine prey. The exception was the Mandarte Island colony in Pacific British Columbia, where PFSA and PFCA exposure appeared to be via terrestrial and/or freshwater prey consumption. The same was true for the freshwater sites where egg SIs suggested both aquatic and terrestrial prey consumption as the source for PFC exposure depending on the colony. Both aquatic (marine and freshwater) and terrestrial prey are likely sources of PFC exposure to gulls but exposure scenarios are colony-specific.  相似文献   
148.
Regional Environmental Change - By 2014 approximately 2.2 million km2 (~43%) of Brazil’s Legal Amazonia region had been incorporated into an extensive network of 718 protected areas, which...  相似文献   
149.
Literature data on numerical values obtained for the parameters of the two most popular models for simulating the migration of radionuclides in undisturbed soils have been compiled and evaluated statistically. Due to restrictions on the applicability of compartmental models, the convection–dispersion equation and its parameter values should be preferred. For radiocaesium, recommended values are derived for its effective convection velocity and dispersion coefficient. Data deficiencies still exist for radionuclides other than caesium and for soils of non-temperate environments.  相似文献   
150.
A major bottleneck for data-based policy making is that data sources are collected, managed, and distributed by different institutions, residing in different locations, resulting in conceptual and practical problems. The use of dispersed data for agricultural systems research requires the integration of data sources, which means to ensure consistency in data interpretations, units, spatial and temporal scales, to respect legal regulations of privacy, ownership and copyright, and to enable easy dissemination of data. This paper describes the SEAMLESS integrated database on European agricultural systems. It contains data on cropping patterns, production, farm structural data, soil and climate conditions, current agricultural management and policy information. To arrive at one integrated database, a shared ontology was developed according to a collaborative process, which facilitates interdisciplinary research. The paper details this process, which can be re-used in other research projects for integrating data sources.  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