全文获取类型
收费全文 | 1800篇 |
免费 | 41篇 |
国内免费 | 15篇 |
专业分类
安全科学 | 62篇 |
废物处理 | 61篇 |
环保管理 | 373篇 |
综合类 | 195篇 |
基础理论 | 503篇 |
环境理论 | 2篇 |
污染及防治 | 432篇 |
评价与监测 | 109篇 |
社会与环境 | 103篇 |
灾害及防治 | 16篇 |
出版年
2022年 | 21篇 |
2021年 | 22篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 46篇 |
2017年 | 33篇 |
2016年 | 73篇 |
2015年 | 53篇 |
2014年 | 55篇 |
2013年 | 167篇 |
2012年 | 62篇 |
2011年 | 110篇 |
2010年 | 67篇 |
2009年 | 77篇 |
2008年 | 81篇 |
2007年 | 88篇 |
2006年 | 72篇 |
2005年 | 65篇 |
2004年 | 53篇 |
2003年 | 57篇 |
2002年 | 57篇 |
2001年 | 50篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 39篇 |
1994年 | 21篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 15篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有1856条查询结果,搜索用时 15 毫秒
841.
Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O2 (> 300 µM) and NH4+ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O2, NH4+, and NO3− (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both sites (1.8 to 350 g− 1 and 33 to 35,000 g− 1, respectively). Potential nitrifying activity measured in core material in the laboratory was also very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily sequences associated with the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in the deeper anoxic, NH4+ zone at the down-gradient site. Only a single Nitrosospira sequence was detected beneath the infiltration bed. Furthermore, the majority of Nitrosospira-associated sequences represent an unrecognized cluster. We conclude that an uncharacterized group associated with Nitrosospira dominate at the geochemically stable, down-gradient site, but found little evidence for Betaproteobacteria nitrifiers beneath the infiltration beds where geochemical conditions were more variable. 相似文献
842.
843.
The controversial family Adapisoriculidae, a group of shrew-sized Paleocene mammals, had proposed relationships with insectivores,
marsupials and more recently to plesiadapiforms. Adapisoriculid remains are numerous in the early Paleocene locality of Hainin,
Belgium, and allow us a test of these different phylogenetic hypotheses. Here, we identify the first tarsal bones of adapisoriculid
mammals. The highly specialised bones indicate an arboreal mode of life with euarchontan affinity. Moreover, the tarsal bones
are morphologically very close to those of the late Cretaceous Deccanolestes from the Deccan intertrappean beds of India, and also share several characters with the Paleocene plesiadapiforms and the
extant cynocephalid dermopterans. The adapisoriculid affinities of Deccanolestes are also confirmed by tooth morphology, indicating that Deccanolestes is a primitive member of this family. These phylogenetic affinities suggest a paleobiogeographic scenario for the family
with dispersal either via East Africa or across the Tethys area. 相似文献
844.
845.
Robert C. Carr Wallace B. Smith 《Journal of the Air & Waste Management Association (1995)》2013,63(6):694-699
This is the sixth and last part in a series of papers discussing the experience of electric utilities in applying baghouse technology for the collection of particulate matter at coal-fired electric power generating plants. The series presents new data obtained in research sponsored by the Electric Power Research Institute (EPRI) on reverse-gas and shake/deflate cleaned baghouses, and specifically addresses a number of unresolved issues in the design and operation of these units. This paper discusses research, development and demonstration activities now underway or planned to further understand baghouse technology to ensure efficient, economic and reliable service in utility applications. In addition, it summarizes the major findings reported in Parts I through V. 相似文献
846.
Simon K. Dinehart Loren M. Smith Philip N. Smith David A. Haukos 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2610-2617
Pesticides have been implicated in widespread amphibian declines. We assessed acute and chronic toxicity of two widely used herbicides to larval New Mexico (Spea multiplicata) and Plains (S. bombifrons) spadefoots from cropland and native grassland playas. Roundup WeatherMAX® (WM) toxicity estimates (48- and 216-h LC50; 48-h LC1) for both species were similar to environmental concentrations expected from accidental overspray. Chronic (30-day) exposure to WM at predicted environmental concentrations (2.0 and 2.8 mg glyphosate acid equivalents/L) reduced survival of both species. Ignite® 280 SL (IG) toxicity estimates (48-h LC50 and LC1) for both species were above predicted environmental concentrations of 1.0 mg glufosinate/L. Chronic exposure to predicted environmental concentrations of IG did not reduce survival of either species. Toxicity test results suggest that at predicted environmental concentrations IG would not cause extensive mortalities among larval New Mexico and Plains spadefoots. However, WM may cause extensive mortality among larvae of these species. 相似文献
847.
Ravi K. Srivastava Charles B. Sedman James D. Kilgroe Dennis Smith Scott Renninger 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1460-1470
ABSTRACT Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA) determined that regulation of mercury emissions from coal-fired power plants is appropriate and necessary. To aid in this determination, preliminary estimates of the performance and cost of powdered activated carbon (PAC) injection-based mercury control technologies were developed. This paper presents these estimates and develops projections of costs for future applications. Cost estimates were developed using PAC to achieve a minimum of 80% mercury removal at plants using electrostatic precipitators and a minimum of 90% removal at plants using fabric filters. These estimates ranged from 0.305 to 3.783 mills/kWh. However, the higher costs were associated with a minority of plants using hot-side electrostatic precipitators (HESPs). If these costs are excluded, the estimates range from 0.305 to 1.915 mills/kWh. Cost projections developed using a composite lime-PAC sorbent for mercury removal ranged from 0.183 to 2.270 mills/kWh, with the higher costs being associated with a minority of plants that used HESPs. 相似文献
848.
Neil R. Jordan Bradley P. Smith Robert G. Appleby Lily M. van Eeden Hugh S. Webster 《Conservation biology》2020,34(4):803-810
Millennia of human conflict with wildlife have built a culture of intolerance toward wildlife among some stakeholders. We explored 2 key obstacles to improved human–wildlife coexistence: coexistence inequality (how the costs and benefits of coexisting with wildlife are unequally shared) and intolerance. The costs of coexisting with wildlife are often disproportionately borne by the so-called global south and rural communities, and the benefits often flow to the global north and urban dwellers. Attitudes and behaviors toward wildlife (tolerance versus intolerance) vary with social and cultural norms. We suggest more empathetic advocacy is needed that, for example, promotes conservation while appropriately considering those who bear the costs of conflict with wildlife. To achieve more equitable cost-sharing, we suggest limiting the costs incurred by those most affected or by sharing those costs more widely. For example, we advocate for the development of improved wildlife compensation schemes, increasing the scale of rewilding efforts, and preventing wildlife-derived revenue leaching out of the local communities bearing the costs of coexistence. 相似文献
849.
Jerad D. Bales Benjamin F Pope 《Journal of the American Water Resources Association》2001,37(1):91-104
ABSTRACT: A set of procedures for identifying changes in selected streamflow characteristics at sites having long‐term continuous streamflow records is illustrated by using streamflow data from the Waccamaw River at Freeland, North Carolina for the 55‐year period of 1940–1994. Data were evaluated and compared to streamflow in the adjacent Lumber River Basin to determine if changes in streamflow characteristics in the Waccamaw River were localized and possibly the result of some human activity, or consistent with regional variations. Following 1963, droughts in the Waccamaw Basin seem to have been less severe than in the Lumber Basin, and the annual one‐, seven‐, and 30‐day low flows exhibited a slightly increasing trend in the Waccamaw River. Mean daily flows in the Waccamaw River at the 90 percent exceedance level (low flows) during 1985–194, a relatively dry period, were very nearly equal to flows at the same exceedance level for 1970–1979, which represents the 10‐year period between 1940 and 1994 with the highest flows. Prior to the 1980s, flows per unit drainage area in the Waccamaw Basin were generally less than those in the Lumber Basin, but after 1980, the opposite was true. The ratio of base flow to runoff in the Waccamaw River may have changed relative to that in the Lumber River in the late 1970s. There was greater variability in Waccamaw River streamflow than in Lumber River flow, and flow variability in the Waccamaw River may have increased slightly during 1985–1994. 相似文献
850.