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   197篇
  免费   1篇
  国内免费   1篇
安全科学   2篇
废物处理   10篇
环保管理   17篇
综合类   36篇
基础理论   63篇
污染及防治   52篇
评价与监测   5篇
社会与环境   11篇
灾害及防治   3篇
  2023年   2篇
  2022年   4篇
  2021年   5篇
  2019年   2篇
  2018年   1篇
  2017年   9篇
  2016年   8篇
  2015年   7篇
  2014年   6篇
  2013年   12篇
  2012年   12篇
  2011年   8篇
  2010年   5篇
  2009年   12篇
  2008年   17篇
  2007年   13篇
  2006年   7篇
  2005年   10篇
  2004年   7篇
  2003年   10篇
  2002年   10篇
  2001年   3篇
  2000年   5篇
  1999年   2篇
  1998年   4篇
  1997年   5篇
  1996年   1篇
  1995年   1篇
  1994年   4篇
  1992年   3篇
  1989年   2篇
  1976年   1篇
  1962年   1篇
排序方式: 共有199条查询结果,搜索用时 531 毫秒
71.
Olafsson E  Buchmayer S  Skov MW 《Ambio》2002,31(7-8):569-573
Leaf litter removal by the abundant mangrove decapod crab Neosarmatium meinerti was studied in series of field and laboratory experiments in East Africa. In the high intertidal Avicennia marina zone crabs buried all leaves placed on the forest floor and consumed on average 67% of them within 2 hrs. High shore crabs in Kenya buried 4 g m(-2) leaf-litter in 1 hr, i.e. approx. twice the daily litter fall. In contrast, in the low shore Sonneratia alba zone, where typical leaf-eating crabs were absent, none of the offered leaves showed signs of herbivory. Leaf choice experiments in the laboratory showed that N. meinerti preferred some species to others. Leaf consumption per gram crab was higher in females than males. The laboratory studies also indicated that crabs could consume substantially more than the average daily litter fall. Video recordings documented frequent fights to gain or retain fallen leaves, suggesting strong competition for leaf litter. Earlier studies indicating that N. meinerti may sweep mangrove forest floors clean of leaf litter are confirmed. In high shore mangroves of East and South Africa where N. meinerti is common, energy flow appears unique: virtually all litter production is retained.  相似文献   
72.
Since the late 1980s, our group has examined the effects of radiofrequency electromagnetic fields (RF-EMF), including pulse-modulated waves of the type emitted by mobile phones, upon the blood?Cbrain barrier. In more than 2,000 rats, we have repeatedly demonstrated a passage of the rats?? own albumin from the blood through the brain capillaries into the surrounding brain parenchyma at SAR values down to 0.1mW/kg. In most of these experiments, the animals were exposed in TEM-cells, ventilated by an external electrical fan at 50 Hz. In the present study, we examined whether the extremely low frequency (ELF) magnetic fields from the fan (50 Hz, 0.3?C1.5 ??T) might add to the RF effect. Sixty-four rats were divided into 4 groups: RF only, ELF only and RF + ELF exposure plus a sham group. The GSM-900 MHz RF exposure was at the very low, nonthermal, average whole-body SAR level 0.4 mW/kg. Demonstration of the normally occurring albumin extravasation in the basal hypothalamus is our inbuilt control proving that the staining is reliable. Two full series of staining of the whole material gave negative results for hypothalamus. Not until we changed to avidin, biotin, and antibodies from a third supplier, we received an acceptable staining. Twenty-five percent of the RF animals had a pathological albumin leakage, while the ELF and RF + ELF groups with three and two pathological findings, respectively, were not significantly different from the control group. We conclude that the use of external fans has had no major influence upon the result.  相似文献   
73.
Coastal swamps are among the rapidly vanishing wetland habitats in Louisiana. Increased flooding, nutrient and sediment deprivation, and salt-water intrusion have been implicated as probable causes of the decline of coastal swamps. We developed a two-species individual-based forest succession model to compare the growth and composition of a cypress-tupelo swamp under various combinations of flooding intensity and salinity levels, using historical time-series of stage and salinity data as inputs. Our model simulates forest succession over 500 years by representing the growth, mortality, and reproduction of individual Taxodium distichum (baldcypress) and Nyssa aquatica (water tupelo) trees in a 1-km2 spatial grid of 10 m × 10 m cells that vary in water levels and salinity through differences in elevation. We independently adjusted the elevations of each cell to obtain different grid-wide mean elevations and standard deviations of elevation; this affected the temporal and spatial pattern of flooding. We calibrated the model by adjusting selected parameters until averaged basal area, stem density and wood production rates under two different mean elevations (partially versus highly flooded) were qualitatively similar to comparable values reported for swamps in the literature. Corroboration involved comparing model predictions to four well-monitored contrasting habitat sites within the Maurepas Basin, Louisiana, USA. Model predictions of both species combined showed the same patterns among sites as the data, but the model overestimated wood production and the dominance of T. distichum. Exploratory simulations predicted that increased flooding leads to swamps with reduced basal areas and stem densities, while increased salinity resulted in lower basal areas at low salinity concentration (∼1-3 psu) and complete tree mortality at higher salinity concentrations (∼2-6 psu). Our model can provide insight into the succession dynamics of coastal swamps and information for the effective design of restoration actions.  相似文献   
74.
75.
In a previous study, we found that juvenile northern wheatears (Oenanthe oenanthe) exposed to a magnetic displacement to the west of their natural migration route increased their body mass. The total intensity and inclination used for the western displacement may also have been interpreted as northern compared to the experimental site (stronger total field intensity and steeper inclination angle). In order to investigate whether the fuelling response was a response to an unexpected magnetic field or specific to the northern magnetic field, we conducted a new experiment. Juvenile wheatears from the same study population were magnetically displaced to southwestern magnetic fields, exposing the birds to unexpected magnetic combinations, but eliminating the possible effect of a northern magnetic field. A control group was kept in the local geomagnetic field in Sweden for comparison. There was no difference in body mass increase between treatments, suggesting that the fuelling response previously found was not a simple response to an unexpected magnetic field, but rather a specific response to the northern magnetic field. Juvenile wheatears may have developed a fuelling response to northern magnetic fields in order to enable a successful flight towards the migration goal.  相似文献   
76.
Planning for adaptation to climate change is often regarded to be a local imperative and considered to be more effective if grounded on a solid evidence base and recognisant of relevant climate projections. Research has already documented some of the challenges of making climate information usable in decision-making but has not yet sufficiently reflected on the role of the wider institutional and regulatory context. This article examines the impact of the external institutional context on the use and usability of climate projections in local government through an analysis of 44 planning and climate change (adaptation) documents and 54 semi-structured interviews with planners in England and Germany conducted between July 2013 and May 2014. We show that there is little demand for climate projections in local adaptation planning in either country due to existing policy, legal and regulatory frameworks. Local government in England has not only experienced a decline in use of climate projections, but also the waning of the climate change adaptation agenda more widely, amidst changes in the planning and regulatory framework and severe budget cuts. In Germany, spatial planning makes substantial use of past and present climate data, but the strictly regulated nature of planning prevents the use of climate projections, due to their inherent uncertainties. Findings from the two countries highlight that if we are to better understand the usability of climate projections, we need to be more aware of the institutional context within which planning decisions are made. Otherwise we run the risk of continuing to provide tools and information that are of limited use within their intended context.  相似文献   
77.
End-of-life vehicles (ELV) have become a global concern as automobiles have become popular worldwide. An international workshop was held to gather data and to discuss 3R policies and ELV recycling systems, their background and present situation, outcomes of related policies and programs, the framework of recycling and waste management, and case studies on related topics in several countries and regions, as well as the essential points of the comparison. Legislative ELV recycling systems are established in the EU, Japan, Korea, and China, while in the US, ELV recycling is managed under existing laws on environmental protection. Since automobile shredding residue (ASR) has a high calorific value and ash content, and includes heavy metals as well as a mass of unclassified fine particles, recycling ASR is considered highly difficult. Countries with a legislative ELV system commonly set a target for recovery rates, with many aiming for more than 95 % recovery. In order to reach this target, higher efficiency in ASR recovery is needed, in addition to material recycling of collectable components and metals. Environmentally friendly design was considered necessary at the planning and manufacturing stages, and the development of recycling systems and techniques in line with these changes are required for sound ELV management.  相似文献   
78.
Veterinary antimicrobials are emerging environmental contaminants of concern. In this study, the sorption of enrofloxacin (ENR) onto humic acids (HAs) extracted from three Brazilian soils was evaluated. HAs were characterized by elemental analysis and solid 13C nuclear magnetic resonance spectroscopy. The sorption of ENR onto HAs was at least 20-fold higher than onto the soils from which they were separated. Ionic and cation bridging are the primary interactions involved. The interactions driven by cation exchange are predominant on HAs, which appear to have abundant carboxylic groups and a relatively high proportion of H-bond donor moieties with carbohydrate-like structures. Interactions explained by cation bridging and/or surface complexation on HAs are facilitated by moieties containing conjugated ligands, significant content of oxygen-containing functional groups, such as phenolic-OH or lignin-like structures. HAs containing electron-donating phenolic moieties and carboxylic acid ligand groups exhibit a sorption mechanism that is primarily driven by strong metal binding, favoring the formation of ternary complexes between functional groups of the organic matter and drugs.  相似文献   
79.
为了研究未来的可持续生产系统,本文采用循序渐进的方法,基于不同可持续发展目标,设计了3种生猪生产情景.第一种情景集中考虑动物福利和动物的自然行为.第二种情景则以对环境影响最小,有效利用自然资源为目标.第三种情景以产品质量和安全为目标.每一种情景各自实现可持续发展不同方面的目标,但是这些目标存在着冲突,没有哪种情景能够实现所有的目标.之后,将情景参数化,使用生命周期评估(LCA)方法,计算各自对环境的影响,并用同一套数据计算经济成本.计算结果是,每公斤猪肉成本以动物福利情景最高,其它两种情景成本较为接近.环境情景的环境影响最低,产品质量情景的环境影响最大.最后,基于未来的不同优先序,讨论各个结果.  相似文献   
80.
本文通过在东非进行的一系列野外和实验室试验,研究了丰富的红树林十足类螃蟹迈纳新胀蟹(Neosarmatium meinerti)对落叶的清理.在地势高的海榄雌(Avicennia meinerti)潮间带,螃蟹掩埋了所有红树林林区海底的落叶,而且会在2小时内平均消耗其中的67%.  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