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   89818篇
  免费   1234篇
  国内免费   1104篇
安全科学   3595篇
废物处理   3217篇
环保管理   13964篇
综合类   21136篇
基础理论   26351篇
环境理论   77篇
污染及防治   14163篇
评价与监测   5453篇
社会与环境   3649篇
灾害及防治   551篇
  2022年   739篇
  2021年   800篇
  2020年   647篇
  2019年   870篇
  2018年   1118篇
  2017年   1184篇
  2016年   2166篇
  2015年   1826篇
  2014年   2580篇
  2013年   9283篇
  2012年   2213篇
  2011年   2451篇
  2010年   3258篇
  2009年   3430篇
  2008年   1989篇
  2007年   1859篇
  2006年   2269篇
  2005年   2222篇
  2004年   2528篇
  2003年   2386篇
  2002年   1914篇
  2001年   2101篇
  2000年   1828篇
  1999年   1425篇
  1998年   1333篇
  1997年   1316篇
  1996年   1450篇
  1995年   1573篇
  1994年   1470篇
  1993年   1304篇
  1992年   1310篇
  1991年   1280篇
  1990年   1230篇
  1989年   1200篇
  1988年   1035篇
  1987年   969篇
  1986年   994篇
  1985年   1064篇
  1984年   1156篇
  1983年   1180篇
  1982年   1183篇
  1981年   1099篇
  1980年   944篇
  1979年   933篇
  1978年   820篇
  1977年   726篇
  1976年   641篇
  1975年   613篇
  1973年   637篇
  1972年   650篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Research increasingly highlights cause and effect relationships between urbanization and stream conditions are complex and highly variable across physical and biological regions. Research also demonstrates stormwater runoff is a key causal agent in altering stream conditions in urban settings. More specifically, thermal pollution and high salt levels are two consequences of urbanization and subsequent runoff. This study describes a demonstration model populated with data from a high gradient headwaters stream. The model was designed to explain surface water‐groundwater dynamics related to salinity and thermal pollution. Modeled scenarios show long‐term additive impacts from salt application and suggest reducing flow rates, as stormwater management practices are typically designed to do, have the potential to greatly reduce salt concentrations and simultaneously reduce thermal pollution. This demonstration model offers planners and managers reason to be confident that stormwater management efforts can have positive impacts.  相似文献   
992.
Small body size is generally correlated with r‐selected life‐history traits, including early maturation, short‐generation times, and rapid growth rates, that result in high population turnover and a reduced risk of extinction. Unlike other classes of vertebrates, however, small freshwater fishes appear to have an equal or greater risk of extinction than large fishes. We explored whether particular traits explain the International Union for Conservation of Nature (IUCN) Red List conservation status of small‐bodied freshwater fishes from 4 temperate river basins: Murray‐Darling, Australia; Danube, Europe; Mississippi‐Missouri, North America; and the Rio Grande, North America. Twenty‐three ecological and life‐history traits were collated for all 171 freshwater fishes of ≤120 mm total length. We used generalized linear mixed‐effects models to assess which combination of the 23 traits best explained whether a species was threatened or not threatened. We used the best models to predict the probability of 29 unclassified species being listed as threatened. With and without controlling for phylogeny at the family level, small body size—among small‐bodied species—was the most influential trait correlated with threatened species listings. The k‐folds cross‐validation demonstrated that body size and a random effect structure that included family predicted the threat status with an accuracy of 78% (SE 0.5). We identified 10 species likely to be threatened that are not listed as such on the IUCN Red List. Small body size is not a trait that provides universal resistance to extinction, particularly for vertebrates inhabiting environments affected by extreme habitat loss and fragmentation. We hypothesize that this is because small‐bodied species have smaller home ranges, lower dispersal capabilities, and heightened ecological specialization relative to larger vertebrates. Trait data and further model development are needed to predict the IUCN conservation status of the over 11,000 unclassified freshwater fishes, especially those under threat from proposed dam construction in the world's most biodiverse river basins.  相似文献   
993.
Climate change impacts human health in a variety of ways. Variables including the climate-related risk factor, the health outcome and location all determine the nature and extent of the impact. The existence of different pathways and endpoints presents a problem for quantifying and comparing impacts. Disability-adjusted life year (DALY) provides a common scale, whereby the impact of climate change on both acute and chronic health outcomes can be compared. This study presents a methodology to calculate the impact of climate change on human health at a local scale, using cardiovascular disease (CVD) and meteorological disaster-related injuries (DRIs) in Osaka Prefecture, Japan, as applied case studies. An additional very fine scale assessment of CVD conducted at the neighbourhood level to demonstrate the importance of conducting risk assessments at a local level. The comparative results calculated the impact of climate change in 2050 to be 16.866 DALY/100,000 population for CVD and 0.645 DALY/100,000 for meteorological DRIs. The actual impact of climate change by 2050 on CVD is judged to be higher, although the relative risk was projected to be lower (1.006, compared to 1.263 for meteorological DRIs). The fine scale assessment revealed the variations in the projected impact of climate change on CVD for all administrative zones in Osaka Prefecture. The range of impacts varied from 0 to 114.29 DALY/100,000. The results demonstrate the applicability of using DALY to quantify the impact of climate change on different health outcomes, using a transferable methodology, and provide information that enables evidence-based prioritisation of climate change adaptation strategies at a local scale.  相似文献   
994.
In this study, bio-thermoset from epoxidized soybean oil (ESO) was prepared in the presence of methylhexahydrophthalic anhydride curing agent and 2-ethyl-4-methylimidazole catalyst. The crosslink densities of the synthesized ESO are ranged from 0.109 × 10?3 to 0.308 × 10?3 mol/cm3. The ESO bio-thermosets were exposed to the soil-burial test for 8 months. Weight change and morphology of the degraded ESO specimens were assessed. It was found that the weight loss of ESO was governed by the materials compositions, crosslink density and the soil-burial exposure time. The 3 mm thickness ESO bio-thermosets with crosslink density of 0.109 × 10?3 mol/cm3 had fully biodegraded after soil-burial for 6 months. In addition, 16S rDNA sequencing was carried out to identify the soil microorganisms. It was suggested that Comamonas sp., Bacillus sp., Streptomyces sp. and Acinetobacter sp. are the possible soil microbes that degrade the ESO bio-thermosets in the compost soil environment.  相似文献   
995.
The increasing awareness of the society about safe guarding heritage buildings and at the same time protecting the environment promotes strategies of combining principles of restoration with environmentally friendly materials and techniques. Along these lines, an experimental program was carried out in order to investigate the possibility of producing repair, lime-based mortars used in historic buildings incorporating secondary materials. The alternative material tested was recycled fine aggregates originating from mixed construction and demolition waste. Extensive tests on the raw materials have been performed and mortar mixtures were produced using different binding systems with natural, standard and recycled sand in order to compare their mechanical, physical and microstructure properties. The study reveals the improved behavior of lime mortars, even at early ages, due to the reaction of lime with the Al and Si constituents of the fine recycled sand. The role of the recycled sand was more beneficial in lime mortars rather than the lime–pozzolan or lime–pozzolan–cement mortars as a decrease in their performance was recorded in the latter cases due to the mortars’ structure.  相似文献   
996.
A marginal abatement cost curve (MACC) traces out the relationship between the quantity of pollution abated and the marginal cost of abating each additional unit. In the context of air quality management, MACCs are typically developed by sorting control technologies by their relative cost-effectiveness. Other potentially important abatement measures such as renewable electricity, energy efficiency, and fuel switching (RE/EE/FS) are often not incorporated into MACCs, as it is difficult to quantify their costs and abatement potential. In this paper, a U.S. energy system model is used to develop a MACC for nitrogen oxides (NOx) that incorporates both traditional controls and these additional measures. The MACC is decomposed by sector, and the relative cost-effectiveness of RE/EE/FS and traditional controls are compared. RE/EE/FS are shown to have the potential to increase emission reductions beyond what is possible when applying traditional controls alone. Furthermore, a portion of RE/EE/FS appear to be cost-competitive with traditional controls.

Implications: Renewable electricity, energy efficiency, and fuel switching can be cost-competitive with traditional air pollutant controls for abating air pollutant emissions. The application of renewable electricity, energy efficiency, and fuel switching is also shown to have the potential to increase emission reductions beyond what is possible when applying traditional controls alone.  相似文献   

997.
Gas platforms can exert relevant effects on various ecosystem properties of the hosting area, modifying patterns of productivity and particle sedimentation. We hypothesised that the presence of gas platforms is associated with higher organic matter (OM) contents and we tested the null hypothesis by which benthic trophic conditions do not vary significantly among gas structures with different architectural characteristics. To test these hypotheses, we investigated sedimentary OM contents and biochemical composition at increasing distance from two distinct structures: one subsea well-site and one four-leg platform (FLP). We found that sediments surrounding the structures were characterised by similar OM contents, but different biochemical compositions, and that sedimentary OM compositional change with increasing distance from the structure is confirmed only at the FLP. These results suggest that: (i) benthic eutrophication is not consistent among different structures; (ii) OM biochemical composition changes are more evident than those in OM quantity; and (iii) the effect, wherever present, disappears at a very narrow distance from the platform. As biochemical composition of OM reflects food availability for benthic organisms, our results suggest that the enrichment of macrozoobenthic communities around these structures could be the consequence of increased nutritional quality of resources.  相似文献   
998.
Expanding populations of farmland foraging geese are causing escalating conflict with agriculture. We used questionnaires to investigate farmers´ perceptions in mid-Norway of spring staging geese and the extent to which they attempt to reduce pasture damage by goose scaring. We predicted farmers’ scaring effort (a measure of dissatisfaction) to increase on fields closer to goose roosting sites where goose grazing intensity was highest (measured by dropping counts). Results showed no such relationship, suggesting that farmers’ perception of goose use was not linked to actual goose use, but influenced by sociological factors and individual opinion. These results confirm the need to distribute subsidies/compensation to affected farmers based upon quantifiable measures of goose use rather than complaint levels. To avoid further conflict escalation, it is equally important that managers are aware of farmers´ perceptions and their causes, to effectively target communication about policies and measures to mitigate goose–agriculture problems.  相似文献   
999.
Glyphosate has become the most commonly used herbicide worldwide and is reputedly environmentally benign, nontoxic, and safe for use near wildlife and humans. However, studies indicate its toxicity is underestimated and its persistence in the environment is greater than once thought. Its actions as a neurotoxin and endocrine disruptor indicate its potential to act in similar ways to persistent organic pollutants such as the organochlorines dichlorodiphenyltrichloroethane (DDT) and dioxin. Exposure to glyphosate and glyphosate‐based herbicides for both wildlife and people is likely to be chronic and at sublethal levels, with multiple and ongoing exposure events occurring in urban and agricultural landscapes. Despite this, there has been little research on the impact of glyphosate on wildlife populations, and existing studies appear in the agricultural, toxicology, and water‐chemistry literature that may have limited visibility among wildlife biologists. These studies clearly demonstrate a link between chronic exposure and neurotoxicity, endocrine disruption, cell damage, and immune suppression. There is a strong case for the recognition of glyphosate as an emerging organic contaminant and substantial potential exists for collaborative research among ecologists, toxicologists, and chemists to quantify the impact of glyphosate on wildlife and to evaluate the role of biosentinel species in a preemptive move to mitigate downstream impacts on people. There is scope to develop a decision framework to aid the choice of species to biomonitor and analysis methods based on the target contaminant, spatial and temporal extent of contamination, and perceived risk. Birds in particular offer considerable potential in this role because they span agricultural and urban environments, coastal, inland, and wetland ecosystems where glyphosate residues are known to be present.  相似文献   
1000.
Journal of Material Cycles and Waste Management - In this study, the composition, characteristics and generation rates of solid waste (SW) in Ogbe-Ijoh community were investigated to provide...  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