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   3111篇
  免费   25篇
  国内免费   80篇
安全科学   84篇
废物处理   215篇
环保管理   254篇
综合类   326篇
基础理论   678篇
环境理论   3篇
污染及防治   1173篇
评价与监测   278篇
社会与环境   192篇
灾害及防治   13篇
  2023年   24篇
  2022年   114篇
  2021年   70篇
  2020年   46篇
  2019年   60篇
  2018年   137篇
  2017年   96篇
  2016年   146篇
  2015年   111篇
  2014年   155篇
  2013年   261篇
  2012年   177篇
  2011年   240篇
  2010年   166篇
  2009年   147篇
  2008年   160篇
  2007年   213篇
  2006年   149篇
  2005年   103篇
  2004年   131篇
  2003年   94篇
  2002年   88篇
  2001年   119篇
  2000年   54篇
  1999年   33篇
  1998年   18篇
  1997年   12篇
  1996年   18篇
  1995年   17篇
  1994年   12篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1990年   4篇
  1989年   6篇
  1988年   5篇
  1987年   2篇
  1986年   2篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1967年   2篇
  1964年   2篇
  1960年   1篇
  1958年   1篇
  1956年   1篇
  1951年   1篇
  1915年   1篇
排序方式: 共有3216条查询结果,搜索用时 0 毫秒
261.
Metal contamination of farming soils affected by industry   总被引:50,自引:0,他引:50  
The contents of nine elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Sb and Zn) have been assayed in the farming soils of Suszec commune (southern Poland). This area is affected by the main industrial centre of Poland (the Upper Silesian Industrial Region), the Czech Republic (Trzyniec smelter) and local contamination sources (coal mine). The contamination of the soils was assessed on the basis of geoaccumulation index, enrichment factor, contamination factor and degree of contamination. The tests revealed elevated contents of cadmium, lead, arsenic, antimony and mercury. The contents of the other elements were similar to the levels in the Earth's crust or pointed to metal depletion in the soil (EF<1).  相似文献   
262.
The REEF Fish Survey Project is a volunteer fish monitoring program developed by the Reef Environmental Education Foundation (REEF). REEF volunteers collect fish distribution and abundance data using a standardized visual method during regular diving and snorkeling activities. Survey data are recorded on preprinted data sheets that are returned to REEF and optically digitized. Data are housed in a publicly accessible database on REEF's Web site (http: //www.reef.org). Since the project's inception in 1993, over 40,000 surveys have been conducted in the coastal waters of North America, tropical western Atlantic, Gulf of California and Hawaii. The Fish Survey Project has been incorporated into existing monitoring programs through partnerships with government agencies, scientists, conservation organizations, and private institutions. REEF's partners benefit from the educational value and increased stewardship resulting from volunteer data collection. Applications of the data include an evaluation of fish/habitat interactions in the Florida Keys National Marine Sanctuary, the development of a multi-species trend analysis method to identify sites of management concern, assessment of the current distribution of species, status reports on fish assemblages of marine parks, and the evaluation of no-take zones in the Florida Keys. REEF's collaboration with a variety of partners, combined with the Fish Survey Project's standardized census method and database management system, has resulted in a successful citizen science monitoring program.  相似文献   
263.
The feed additive ractopamine hydrochloride was fortified at four concentrations into batch vials containing soils that differed in both biological activity and organic matter(OM).Sampling of the liquid layer for 14 days demonstrated that ractopamine rapidly dissipated from the liquid layer. Less than 20% of the fortified dose remained in the liquid layer after 4 hr,and recoveries of dosed ractopamine ranged from 8 to 18% in the liquid layer at 336 hr. Sorption to soil was the major fate for ractopamine in soil:water systems, i.e., 42%–51% of the dose at14 days. The major portion of the sorbed fraction was comprised of non-extractables; a smaller fraction of the sorbed dose was extracted into water and acetone, portions which would be potentially mobile in the environment. Partitioning coefficients for all soils suggested strong sorption of ractopamine to soil which is governed by hydrophobic interactions and cation exchange complexes within the soil OM. Ractopamine degradation was observed, but to mostly non-polar compounds which had a higher potential than ractopamine to sorb to soil. The formation of volatiles was also suggested. Therefore, despite rapid and extensive soil sorption,these studies indicated a portion of ractopamine, present in manures used to fertilize soils,may be mobile in the environment via water-borne events.  相似文献   
264.
265.
Molecular techniques and modelling are presented as powerful tools required in the performance of efficient soil and water bioremediation systems. An Escherichia coli CC118-D strain was constructed by inserting the Klebsiella pneumoniae hpa B gene, coding for the unstable 3,4-dihydroxyphenylacetate 2,3-dioxygenase, into its chromosome. When the constructed strain was immobilized, both enzyme stability and viability increased along the studied period, in absence of antibiotic. We proposed this strategy as an approach to overcoming plasmid instability and to enhance enzyme activity and stability, avoiding antibiotic utilization. A model was developed to understand and predict the behaviour of bacteria and pollutants in a bioreactor system, considering: fluid dynamics, molecular/cellular scale processes and biofilm formation.  相似文献   
266.
IntroductionAtmosphericnitrousoxide (N2 O)isaveryradioactivelyactivegreenhousegas,alsocontributingtothedepletionofozonelayerofstratosphere .AtmosphericN2 Omainlyoriginatedfromnitrificationanddenitrificationinterrestrialecosystems.Grasslandecosystem ,accoun…  相似文献   
267.
Biodegradability and ecotoxicity of amine oxide based surfactants   总被引:1,自引:0,他引:1  
García MT  Campos E  Ribosa I 《Chemosphere》2007,69(10):1574-1578
The aerobic and anaerobic biodegradability as well as the aquatic toxicity of two fatty amine oxides and one fatty amido amine oxide were investigated. Aerobic biodegradation was evaluated using the CO(2) headspace test (ISO 14593) and biodegradation under anaerobic conditions was assessed employing a standardised batch test. The three amine oxide based surfactants tested were readily biodegradable under aerobic conditions but only the alkyl amido amine oxide was found to be easily biodegradable under anaerobic conditions. Toxicity to Photobacterium phosphoreum and Daphnia magna was evaluated. Bacteria (EC(50) from 0.11 to 11 mg l(-1)) proved to be more sensitive to the toxic effects of the amine oxide based surfactants than crustacea (IC(50) from 6.8 to 45 mg l(-1)). The fatty amido amine oxide showed the lowest aquatic toxicity.  相似文献   
268.
Ozone (O3) concentration and flux (Fo) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O3-induced wheat yield loss was estimated by utilizing O3 exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O3 concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O3 concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O3 concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (Vd) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged Vd during daytime (6:00–18:00) and nighttime (18:00–6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured Vd was about 1.5 cm/sec. The magnitude of Vd was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean Fo appeared at 14:00, and the maximum measured Fo was − 33.5 nmol/(m2·sec). Averaged Fo during daytime and nighttime were − 6.9 and − 1.5 nmol/(m2·sec), respectively. (4) Using O3 exposure-response functions obtained from the USA, Europe, and China, the O3-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%–23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions.  相似文献   
269.
Human pressure has been exponentially growing during recent decades in coastal areas, which have led to drastic losses of biodiversity in coastal ecosystems. The current conservation status of many coastal plant species is directly related to a lack of environmental criteria in the urban planning of coastal areas over recent decades. This study aimed to evaluate the evolution, over the last 9 years, of the conservation status of various populations of the endangered plant Glaucium flavum, exploring the extent to which human pressure and different management strategies practiced in the coastal areas where the populations are established have affected the conservation status of the species. The populations analysed have evolved in a different manner over the last 9 years, as have their threat factors, and a relationship was evident between their conservation status and the evolution of these different threat factors. Our results indicate that an appropriate planning of local management actions, such as the installation of walkways or the successful eradication of invasive species, may be determinant factors for successful conservation of the coastal vegetation. The presence of species that are sensitive to slight changes in the ecosystem, and the main factors that govern the plant performance of these species, must be given full consideration in decision-making processes of coastal planning and management.  相似文献   
270.
The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting C stocks in Amazonia when such great pedological variability is not taken into account.  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