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   3124篇
  免费   11篇
  国内免费   35篇
安全科学   64篇
废物处理   149篇
环保管理   334篇
综合类   450篇
基础理论   1146篇
环境理论   1篇
污染及防治   642篇
评价与监测   199篇
社会与环境   181篇
灾害及防治   4篇
  2023年   6篇
  2022年   5篇
  2021年   11篇
  2020年   7篇
  2019年   8篇
  2018年   114篇
  2017年   122篇
  2016年   192篇
  2015年   58篇
  2014年   26篇
  2013年   49篇
  2012年   434篇
  2011年   236篇
  2010年   45篇
  2009年   44篇
  2008年   63篇
  2007年   73篇
  2006年   73篇
  2005年   399篇
  2004年   540篇
  2003年   412篇
  2002年   47篇
  2001年   44篇
  2000年   21篇
  1999年   32篇
  1998年   4篇
  1997年   10篇
  1996年   3篇
  1995年   14篇
  1994年   8篇
  1993年   5篇
  1992年   8篇
  1991年   7篇
  1990年   6篇
  1989年   5篇
  1986年   3篇
  1984年   2篇
  1983年   2篇
  1975年   2篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1969年   2篇
  1968年   2篇
  1966年   2篇
  1964年   1篇
  1963年   1篇
  1961年   1篇
  1957年   2篇
  1928年   1篇
排序方式: 共有3170条查询结果,搜索用时 46 毫秒
941.

Purpose  

The purpose of this work is to contribute to the understanding of the photochemical air pollution analysing the levels and temporal variations of surface ozone in two rural areas situated in central-southern Spain.  相似文献   
942.
A number of key projects in the Environmental Protection Agency (EPA) particulate R&;D program having applicability to industry are presented. For electrostatic precipitators (ESP) there is presented the result of work on large diameter discharge electrodes which provide a decrease in penetration of up to a factor of 4 when compared to conventional small diameter electrodes. Also discussed is the multistage ESP which provides a collection efficiency that would require a collecting plate area 4 or 5 times larger with conventional ESP technology. The E-SOX technology makes use of the multistage concept to free up space in the ESP for SO2 removals of up to 90%. Electrostatically augmented fabric filtration provides a reduction in pressure drop of about 5 0% as compared to conventional fabric filtration. Wind tunnel modeling of windbreaks for material storage piles indicates a potential for providing engineering design data that would allow significant emission reduction caused by wind erosion  相似文献   
943.
Dynamic model simulations of the future climate and projections of future lifestyles within the Baltic Sea Drainage Basin (BSDB) were considered in this study to estimate potential trends in future nutrient loads to the Baltic Sea. Total nitrogen and total phosphorus loads were estimated using a simple proxy based only on human population (to account for nutrient sources) and stream discharges (to account for nutrient transport). This population-discharge proxy provided a good estimate for nutrient loads across the seven sub-basins of the BSDB considered. All climate scenarios considered here produced increased nutrient loads to the Baltic Sea over the next 100 years. There was variation between the climate scenarios such that sub-basin and regional differences were seen in future nutrient runoff depending on the climate model and scenario considered. Regardless, the results of this study indicate that changes in lifestyle brought about through shifts in consumption and population potentially overshadow the climate effects on future nutrient runoff for the entire BSDB. Regionally, however, lifestyle changes appear relatively more important in the southern regions of the BSDB while climatic changes appear more important in the northern regions with regards to future increases in nutrient loads. From a whole-ecosystem management perspective of the BSDB, this implies that implementation of improved and targeted management practices can still bring about improved conditions in the Baltic Sea in the face of a warmer and wetter future climate.  相似文献   
944.
G?ran Sundblad  Ulf Bergstr?m 《Ambio》2014,43(8):1020-1028
Coastal development has severely affected habitats and biodiversity during the last century, but quantitative estimates of the impacts are usually lacking. We utilize predictive habitat modeling and mapping of human pressures to estimate the cumulative long-term effects of coastal development in relation to fish habitats. Based on aerial photographs since the 1960s, shoreline development rates were estimated in the Stockholm archipelago in the Baltic Sea. By combining shoreline development rates with spatial predictions of fish reproduction habitats, we estimated annual habitat degradation rates for three of the most common coastal fish species, northern pike (Esox lucius), Eurasian perch (Perca fluviatilis) and roach (Rutilus rutilus). The results showed that shoreline constructions were concentrated to the reproduction habitats of these species. The estimated degradation rates, where a degraded habitat was defined as having ≥3 constructions per 100 m shoreline, were on average 0.5 % of available habitats per year and about 1 % in areas close to larger population centers. Approximately 40 % of available habitats were already degraded in 2005. These results provide an example of how many small construction projects over time may have a vast impact on coastal fish populations.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0522-y) contains supplementary material, which is available to authorized users.  相似文献   
945.
The potential influence of autochthonous microorganisms on virus fate in soil is usually determined through extreme conditions of sterilization vs. nonsterilization; however, the relative importance of microbial cells and their exudates remains unclear. In this study, bacterial cells (cell) were harvested, and their exuded extracellular polymeric substances (EPS) were extracted from three strains of bacteria, namely, Gram-negative bacteria Pseudomonas putida and Pseudomonas aeruginosa as well as Gram-positive bacterium Bacillus subtilis. This study aimed to evaluate virus removal in solutions in the presence of cell, EPS, and their combination (cell/EPS), as well as to investigate how their presence affects virus removal efficiencies by four red soils based on batch experiments. Results showed that virus removal percentage in solutions ranged from 11 to 23 in the presence of cells only and from 12 to 15 in the presence of EPS only. The removal percentage in the combined cell/EPS treatment can be estimated by summing the results achieved by the cell and EPS treatments, separately. Meanwhile, cell presence had a negligible effect on virus removal by red soils. EPS and combined cell/EPS significantly reduced virus removal by 20 to 69 % and 16 to 50 %, respectively, which indicated that EPS served a dominant function in reducing virus removal. This study clearly demonstrated that the prediction of virus removal by red soils must consider the effect of bacteria, especially those producing large quantities of EPS, which can be responsible for the underestimation of viral load in certain studies.  相似文献   
946.
The water-soluble fraction (WSF) of petroleum contains a mixture of polycyclic aromatic hydrocarbons, volatile hydrocarbons, phenols, and heterocyclic compounds, considered deleterious to aquatic biota. Marine “pejerrey” Odontesthes argentinensis (Teleostei: Atherinopsidae) has a great commercial importance in local fisheries and a high potential for aquaculture. The aim of this study was to evaluate the histopathological effects in “pejerrey” larvae exposed to different concentrations of petroleum WSF. The chronic toxicity test was conducted with newly hatched larvae exposed for 21 days to sublethal concentrations of WSF (2.5, 5, 10, and 20 % of WSF), plus one control. Survival and growth were significantly lower in the highest concentration. Several histopathological changes were found in the gills (e.g., hyperplasia, aneurisms, edema, and necrosis), kidney (e.g., nuclear alterations, decrease in the hematopoietic cells), and liver (e.g., hypertrophy, karyorrhexis, and karyopyknosis). An index of branchial lesion was proposed to standardize gill lesions to different pollutants.  相似文献   
947.
The Arctic marine ecosystem contains multiple elements that present alternative states. The most obvious of which is an Arctic Ocean largely covered by an ice sheet in summer versus one largely devoid of such cover. Ecosystems under pressure typically shift between such alternative states in an abrupt, rather than smooth manner, with the level of forcing required for shifting this status termed threshold or tipping point. Loss of Arctic ice due to anthropogenic climate change is accelerating, with the extent of Arctic sea ice displaying increased variance at present, a leading indicator of the proximity of a possible tipping point. Reduced ice extent is expected, in turn, to trigger a number of additional tipping elements, physical, chemical, and biological, in motion, with potentially large impacts on the Arctic marine ecosystem.  相似文献   
948.
This study investigated the removal of Reactive Black 5 (RB5) textile dye from aqueous solutions using cotton (Gossypium hirsutum) seed shell (CSS) as low cost adsorbents. The data were described according to the Freundlich and Langmuir isotherm models. Of these, the Langmuir model provided the best fit for the experimental data. The highest measured adsorption density was 12.19 mg/g at pH 2. An equilibrium adsorption rate of RB5 by CSS (q(e) = 11.879 mg/g) was observed at 30 minutes. In order to evaluate the adsorption kinetic mechanisms, pseudo first and second order rate kinetic models and an intraparticle diffusion model were applied, with the pseudo second order model providing an excellent fit for the data.  相似文献   
949.
950.

Purpose

Exploratory data analysis (EDA) is applied in this research to study the behavior of radioactive aerosols present in the surface atmosphere of Granada, using 7Be as radiotracer. The reason for this study is to reduce the large number of parameters involved in understanding their behavior, given the complexity of the atmosphere.

Methods

Aerosol particles were collected weekly in Granada (Spain) over a 5-year period. Low-background gamma spectrometry was used to determine concentrations of 7Be-aerosol activity. The variables studied were: 7Be concentration, cosmic ray intensity, temperature, temperature interval, rainfall, relative humidity, and Saharan intrusions. Least significant difference test (LSD), hierarchical cluster analysis (HCA), and principal component analysis (PCA) with varimax rotation have been applied to study the datasets.

Results and discussion

The results of our study reveal that aerosol behavior is represented by two principal components which explain 86.23?% of total variance. Components PC1 and PC2 respectively explain 74.61 and 11.62?% of total variance. PC1 explains the cyclical and seasonal pattern of the samples, while PC2 is related to the production of 7Be. In addition, PCA and HCA show good distribution of the samples by families with two groups, summer and winter, at the extremes and spring?Cautumn in the middle. This result corroborates that there are no differences between spring and autumn in the climate of Granada.

Conclusions

EDA has been found to be quite useful in studying the behavior of radioactive aerosols in the surface atmosphere of a city with the climate and geographical characteristics of Granada.  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