全文获取类型
收费全文 | 22556篇 |
免费 | 195篇 |
国内免费 | 234篇 |
专业分类
安全科学 | 604篇 |
废物处理 | 962篇 |
环保管理 | 2642篇 |
综合类 | 4195篇 |
基础理论 | 5630篇 |
环境理论 | 8篇 |
污染及防治 | 5846篇 |
评价与监测 | 1660篇 |
社会与环境 | 1324篇 |
灾害及防治 | 114篇 |
出版年
2022年 | 214篇 |
2021年 | 170篇 |
2020年 | 130篇 |
2019年 | 162篇 |
2018年 | 314篇 |
2017年 | 320篇 |
2016年 | 486篇 |
2015年 | 363篇 |
2014年 | 590篇 |
2013年 | 1679篇 |
2012年 | 695篇 |
2011年 | 956篇 |
2010年 | 773篇 |
2009年 | 844篇 |
2008年 | 954篇 |
2007年 | 981篇 |
2006年 | 887篇 |
2005年 | 791篇 |
2004年 | 711篇 |
2003年 | 757篇 |
2002年 | 685篇 |
2001年 | 991篇 |
2000年 | 636篇 |
1999年 | 421篇 |
1998年 | 263篇 |
1997年 | 275篇 |
1996年 | 286篇 |
1995年 | 336篇 |
1994年 | 281篇 |
1993年 | 217篇 |
1992年 | 267篇 |
1991年 | 269篇 |
1990年 | 278篇 |
1989年 | 258篇 |
1988年 | 236篇 |
1987年 | 173篇 |
1986年 | 178篇 |
1985年 | 203篇 |
1984年 | 203篇 |
1983年 | 195篇 |
1982年 | 191篇 |
1981年 | 182篇 |
1980年 | 137篇 |
1979年 | 164篇 |
1978年 | 143篇 |
1977年 | 133篇 |
1976年 | 135篇 |
1975年 | 132篇 |
1974年 | 144篇 |
1973年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
Lynn M. Russell Ranjit Bahadur Lelia N. Hawkins James Allan Darrel Baumgardner Patricia K. Quinn Timothy S. Bates 《Atmospheric environment (Oxford, England : 1994)》2009,43(38):6100-6105
Organic aerosol chemical markers from normalized concentrations of independent measurements of mass fragments (using Aerosol Mass Spectrometry, AMS) are compared to bond-based functional groups (from Fourier Transform Infrared spectroscopy, FTIR) during eight field projects in the western hemisphere. Several field projects show weak correlations between alcohol group fractions and m/z 60 fractions, consistent with the organic hydroxyl groups and the fragmentation of saccharides, but the weakness of the correlations indicate chemical differences among the relationships for ambient aerosols in different regions. Carboxylic acid group fractions and m/z 44 fractions are correlated weakly for three projects, with correlations expected for aerosols dominated by di-acid compounds since their fragmentation is typically dominated by m/z 44. Despite differences for three projects with ratios of m/z 44 to m/z 57 fragments less than 10, five projects showed a linear trend between the project-average m/z 44 to m/z 57 ratio and the ratio of acid and alkane functional groups. While this correlation explains only a fraction of the fragment and bond variability measured, the consistency of this relationship at multiple sites indicates a general agreement with the interpretation of the relative amount of m/z 44 as a carboxylic acid group marker and m/z 57 as an alkane group marker. 相似文献
902.
J.M. Logue K.E. Huff-Hartz A.T. Lambe N.M. Donahue A.L. Robinson 《Atmospheric environment (Oxford, England : 1994)》2009,43(39):6205-6217
High time-resolved (HTR) measurements can provide significant insight into sources and exposures of air pollution. In this study, an automated instrument was developed and deployed to measure hourly concentrations of 18 gas-phase organic air toxics and 6 volatile organic compounds (VOCs) at three sites in and around Pittsburgh, Pennsylvania. The sites represent different source regimes: a site with substantial mobile-source emissions; a residential site adjacent to a heavily industrialized zone; and an urban background site. Despite the close proximity of the sites (less than 13 km apart), the temporal characteristic of outdoor concentrations varied widely. Most of the compounds measured were characterized by short periods of elevated concentrations or plume events, but the duration, magnitude and composition of these events varied from site to site. The HTR data underscored the strong role of emissions from local sources on exposure to most air toxics. Plume events contributed more than 50% of the study average concentrations for all pollutants except chloroform, 1,2-dichloroethane, and carbon tetrachloride. Wind directional dependence of air toxic concentrations revealed that emissions from large industrial facilities affected concentrations at all of the sites. Diurnal patterns and weekend/weekday variations indicated the effects of the mixing layer, point source emissions patterns, and mobile source air toxics (MSATs) on concentrations. Concentrations of many air toxics were temporally correlated, especially MSATs, indicating that they are likely co-emitted. It was also shown that correlations of the HTR data were greater than lower time resolution data (24-h measurements). This difference was most pronounced for the chlorinated pollutants. The stronger correlations in HTR measurements underscore their value for source apportionment studies. 相似文献
903.
Guor-Cheng Fang Shin-Jay Lin Shih-Yu Chang Charles-C.K. Chou 《Atmospheric environment (Oxford, England : 1994)》2009,43(38):6039-6048
Previous studies have suggested that the ongoing global climate change will likely increase the intensity and frequency of extreme weather, such as typhoons. Since the beginning of global warming, it has become necessary to understand the influence of typhoons on air quality. Rare data, especially particulate measurements data could be used to establish the relationship between the air pollution and typhoons. One of main limiting factors is that most of the previous chemical analyses of particulates used a relatively long sampling time, which could dilute the temporal impact of particulate characteristics and their sources. This work, depending more time-resolved measurements, focus on the characteristics and sources of high particulate matter levels and the influence of typhoons and the Pacific high system. Depending on the measurements, two pollutant groups were clearly identified in this work. The first pollutant group was the emissions from neighboring riverbeds under the strong circulation of the typhoon in the driest season and characterized as high coarse particle concentrations with high mass fraction of Ca2+. The second pollutant group was characterized as the formation and transport of secondary particles with prevalent ions of NH4+, NO3?, and SO42? and occurred in the sea-land breeze circulation under the influence the Pacific high system. 相似文献
904.
T.J. Wallington M.D. Hurley O.J. Nielsen 《Atmospheric environment (Oxford, England : 1994)》2009,43(27):4247-4249
The infrared spectrum of HCF2OCF2OCF2CF2OCF2H (CAS# 188690-77-9) has been re-measured. The integrated absorption intensity over the range 1000–1500 cm?1 measured in the present work is (6.65 ± 0.33) × 10?17 cm2 molecule?1 cm?1 in 700 Torr of air at 296 K. The radiative efficiency of HCF2OCF2OCF2CF2OCF2H is calculated to be 1.02 W m?2 ppb?1. The value reported in the 2007 Intergovernmental Panel on Climate Change (IPCC) report is approximately 35% larger reflecting what we believe to be an erroneously high value for the absorption strength of HCF2OCF2OCF2CF2OCF2H adopted by the IPCC. 相似文献
905.
Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach 总被引:1,自引:0,他引:1
The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result
in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research,
an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing
with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers
primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth
of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater
has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation
Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological
characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban
growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further,
remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization
and its impact on groundwater system. 相似文献
906.
907.
Heavy metals in the aquatic environment have, to date, come essentially from naturally occurring geochemical resources. However,
this has been enhanced by anthropogenic activities such as crude oil exploration and exploitation activities, resulting in
pollution in the Taylor Creek aquatic ecosystem. The catfish species Bagrus bayad and other environmental segments were collected from five selected sites along Taylor Creek, southern Nigeria, and total
metal concentration determined. The concentration levels of the metals in B. bayad were higher than the values reported in the literature for fresh fish and may lead to a higher risk of harmful effects. The
bivariate regression models relating metals in B. bayad and metals in the surface waters were significant (R
2 ≥ 0.9002). The log (bio-concentration factor; BCF) values of Cr and Zn in B. bayad were the highest, whereas the lowest was found for Ni. The ecological distribution of the log (BCF) values was, for all the
heavy metals, moderately stable over the creek. All log-transformed bio-magnification factors (BMF) in the creek were positive,
which indicates that the metal concentration was greater in B. bayad than in suspended particulate matter (SPM). The absolute log (BMF) values of heavy metals can, therefore, be ranked in order
of decreasing magnitude: Cr (3.26) > Zn (2.99) > Cd (2.93) > Fe (2.76) > Pb (2.66) > Mn (2.36) > Ni (2.24). This sequence
indicates that toxic metals such as Cd, Cr and Pb are undergoing significant bio-reduction from SPM to B. bayad. The degree of correlation between the metals was different in B. bayad, which suggests that the sources of the metals polluting Taylor Creek were diverse. 相似文献
908.
Long-term evaluation of coal fly ash and mine tailings co-placement: A site-specific study 总被引:2,自引:0,他引:2
Muluken B. Yeheyis Julie Q. Shang Ernest K. Yanful 《Journal of environmental management》2009,91(1):237-244
This study presents the results of a laboratory investigation conducted to evaluate the efficiency of coal fly ash to control the formation of acid mine drainage (AMD) from mine waste. Site-specific materials, coal fly ash from Atikokan Thermal Generating Station and mine tailings from Musselwhite mine, were mixed at different proportions for the investigation of the drainage chemistry and the optimal mix using static testing (acid–base accounting) and kinetic (column) testing. The acid–base accounting (ABA) results indicated that the fly ash possessed strong alkaline (neutralization) potential (NP) and could be used in the management of reactive mine tailings, thus ensuring prevention of AMD in the long-term. Column tests conducted in the laboratory to further investigate long-term performance of fly ash in the neutralization and prevention of acid mine drainage from tailings similarly showed that mixing fly ash with mine tailings reduces dissolution of many heavy metals from tailings by providing alkalinity to the system. It was found that a fly ash to tailings mass ratio equal to or greater than 15% can effectively prevent AMD generation from Musselwhite mine tailings in the co-placement approach. 相似文献
909.
M.J. Robertson T.G. Measham G. Batchelor R. George R. Kingwell K. Hosking 《Journal of environmental management》2009,90(10):3023-3030
Community and catchment-based approaches to salinity management continue to attract interest in Australia. In one such approach, Catchment Demonstration Initiative (CDI) projects were established by the Western Australian (WA) Government in 2000 for targeted investment in large-scale catchment-based demonstrations of integrated salinity management practices. The aim was to promote a process for technically-informed salinity management by landholders. This paper offers an evaluation of the effectiveness of one CDI project in the central wheatbelt of WA, covering issues including: its role in fostering adoption of salinity management options, the role of research and the technical requirements for design and implementation of on-ground works, the role of monitoring and evaluation, the identification and measurement of public and private benefits, comparison and identification of the place and value of plant-based and engineering-based options, reliance on social processes and impacts of constraints on capacity, management of governance and administration requirements and an appreciation of the value of group-based approaches.A number of factors may reduce the effectiveness of CDI-type approaches in facilitating landholder action to address salinity, many of these are socially-based. Such approaches can create considerable demands on landholders, can be expensive (because of the planning and accountability required) on the basis of dollars per hectare impacted, and can be difficult to garner ownership from all involved. An additional problem could be that few community groups would have the capacity to run such programs and disseminate the new knowledge so that the CDI-type projects can impact outside the focus catchment. In common with many publicly-funded approaches to salinity, we found that direct benefits on public assets are smaller than planned and that results from science-based requirements of monitoring and evaluation have long lead times, causing farmers to either wait for the information or act sooner and take risks based on initial results. We also found that often it is a clear outline of the process that is of most importance in decision making as opposed to the actual results. We identified limitations in regulatory processes and the capacity for local government to engage in the CDI.The opportunities that CDI-type approaches provide centre around the value of its group-based approach. We conclude that they can overcome knowledge constraints in managing salinity by fostering group-based learning, offer a structured process of trialling options so that the costs and benefits can be clearly and transparently quantified, and avoid the costly mistakes and “learning failures” of the past. 相似文献
910.
Removal of Pb(II) ions from aqueous solution using activated tea waste: Adsorption on a fixed-bed column 总被引:1,自引:0,他引:1
An inexpensive and effective adsorbent was developed from waste tea leaves for the dynamic uptake of Pb(II). Characterization of the adsorbents showed a clear change between physico-chemical properties of activated tea waste and simply tea waste. The purpose of this work was to evaluate the potential of activated tea waste in continuous flow removal of Pb(II) ions from synthetic aqueous effluents. The performance of the system was evaluated to assess the effect of various process variables, viz., of bed height, hydraulic loading rate and initial feed concentration on breakthrough time and adsorption capacity. The shape of the breakthrough curves was determined for the adsorption of Pb(II) by varying different operating parameters like hydraulic loading rate (2.3–9.17 m3/h m2), bed height (0.3–0.5 m) and feed concentration (2–10 mg/l). An attempt has also been made to model the data generated from column studies using the empirical relationship based on the Bohart–Adams model. There was an acceptable degree of agreement between the data for breakthrough time calculated from the Bohart–Adams model and the present experimental study with average absolute deviation of less than 5.0%. The activated tea waste in this study showed very good promise as compared with the other adsorbents available in the literature. The adsorbent could be suitable for repeated use (for more than four cycles) without noticeable loss of capacity. 相似文献