全文获取类型
收费全文 | 4949篇 |
免费 | 140篇 |
国内免费 | 61篇 |
专业分类
安全科学 | 270篇 |
废物处理 | 170篇 |
环保管理 | 1251篇 |
综合类 | 536篇 |
基础理论 | 1368篇 |
环境理论 | 8篇 |
污染及防治 | 998篇 |
评价与监测 | 320篇 |
社会与环境 | 172篇 |
灾害及防治 | 57篇 |
出版年
2023年 | 57篇 |
2022年 | 55篇 |
2021年 | 55篇 |
2020年 | 65篇 |
2019年 | 69篇 |
2018年 | 122篇 |
2017年 | 134篇 |
2016年 | 179篇 |
2015年 | 121篇 |
2014年 | 162篇 |
2013年 | 407篇 |
2012年 | 233篇 |
2011年 | 306篇 |
2010年 | 204篇 |
2009年 | 237篇 |
2008年 | 262篇 |
2007年 | 257篇 |
2006年 | 229篇 |
2005年 | 195篇 |
2004年 | 180篇 |
2003年 | 149篇 |
2002年 | 141篇 |
2001年 | 86篇 |
2000年 | 94篇 |
1999年 | 72篇 |
1998年 | 75篇 |
1997年 | 61篇 |
1996年 | 65篇 |
1995年 | 83篇 |
1994年 | 74篇 |
1993年 | 68篇 |
1992年 | 57篇 |
1991年 | 39篇 |
1990年 | 35篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 39篇 |
1986年 | 41篇 |
1985年 | 40篇 |
1984年 | 45篇 |
1983年 | 44篇 |
1982年 | 52篇 |
1981年 | 44篇 |
1980年 | 32篇 |
1979年 | 15篇 |
1978年 | 29篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1972年 | 7篇 |
1971年 | 9篇 |
排序方式: 共有5150条查询结果,搜索用时 46 毫秒
981.
We demonstrate an approach for evaluating the level of protection attained using a variety of forms and levels of past, current,
and proposed Air Quality Standards (AQSs). The U.S. Clean Air Act requires the establishment of ambient air quality standards
to protect health and public welfare. However, determination of attainment of these standards is based on ambient pollutant
concentrations rather than prevention of adverse effects. To determine if a given AQS protected against adverse effects on
vegetation, hourly ozone concentrations were adjusted to create exposure levels that “just attain” a given standard. These
exposures were used in combination with a physiologically-based tree growth model to account for the interactions of climate
and ozone. In the evaluation, we used ozone concentrations from two 6-year time periods from the San Bernardino Mountains
in California. There were clear differences in the level of vegetation protection achieved with the various AQSs. Based on
modeled plant growth, the most effective standards were the California 8-hr average maximum of 70 ppb and a seasonal, cumulative,
concentration-weighted index (SUM06), which if attained, resulted in annual growth reductions of 1% or less. Least effective
was the 1-hr maximum of 120 ppb which resulted in a 7% annual reduction. We conclude that combining climate, exposure scenarios,
and a process-based plant growth simulator was a useful approach for evaluating effectiveness of current or proposed air quality
standards, or evaluating the form and/or level of a standard based on preventing adverse growth effects. 相似文献
982.
Snowmobile use in Yellowstone National Park has been shown to impact air quality, with implications for the safety and welfare
of Park staff and other Park resource values. Localized impacts have been documented at several high-use sites in the Park,
but the broader spatial variability of snowmobile emissions and air quality was not understood. Measurements of 87 volatile
organic compounds (VOCs) were made for ambient air sampled across the Park and West Yellowstone, Montana, during 2 days of
the 2002–2003 winter use season, 1 year before the implementation of a new snowmobile policy. The data were compared with
similar data from pristine West Coast sites at similar latitudes. Backward trajectories of local air masses, alkyl nitrate-parent
alkane ratios, and atmospheric soundings were used to identify the VOC sources and assess their impact. Different oversnow
vehicle types used in the Park were sampled to determine their relative influence on air mass pollutant composition. VOCs
were of local origin and demonstrated strong spatiotemporal variability that is primarily influenced by levels of snowmobile
traffic on given road segments at different times of day. High levels of snowmobile traffic in and around West Yellowstone
produced consistently high levels of benzene, toluene, and carbon monoxide. 相似文献
983.
Perceiving the Environment from the Lay Perspective in Desertified Areas,Northern China 总被引:1,自引:0,他引:1
Investigating local people’s environmental perceptions can produce useful information that could be incorporated into decision
making processes that help resolve environmental problems. Although China is undergoing severe desertification, the perceptions
of the local people toward their degraded environment and the related issues have so far not been actively solicited. This
article, which is a supplement to Lee and Zhang’s (2004, 2005) studies, seeks to further investigate the lay public’s general environmental attitudes, perceptions of desertification, interpretations
of land-degrading activities, and particularly their interrelations in severely desertified areas. Minqin County in Gansu
Province, northern China, was chosen to be the study area. Data was collected via a questionnaire survey (n = 1138) administered in December 2002. Major findings were: (1) Most respondents had only weak altruistic environmental attitudes,
with educational level to be a significant determinant. (2) Respondents’ perceptions of desertification and interpretations
of land-degrading activities were contingent on personal attributes, general environmental attitudes, and other conceptions
related to desertification. It is recommended that the interrelations between the various aspects of the public’s environmental
perceptions should be thoroughly examined to facilitate their participation in environmental management. 相似文献
984.
Genevieve Briand Eric C. Schuck David W. Holland 《Journal of the American Water Resources Association》2008,44(2):360-366
Abstract: For over 10 years, several species of salmon have been identified as either threatened or endangered in the Snake River Basin of Idaho. The United States Bureau of Reclamation, in cooperation with the National Marine Fisheries Service, has proposed a variety of plans to increase stream flows in the Snake River Basin to facilitate movement by juvenile salmon smolts to the ocean. This research examines two of the flow augmentation plans proposed by the Bureau of Reclamation as well as two alternative plans, one founded purely on existing priority‐based water rights and another geared toward minimizing the effects of flow augmentations on farms profitability. Results from a basin‐wide model of agricultural production in the Snake River Basin, the Snake River Agricultural Model, present evidence that (1) older water rights are used towards production of less valuable crops, (2) flow augmentation scenarios have unequal effects on farms profitability across agricultural regions within the basin, and (3) irrigation water is valued from US$4 to US$59 an acre‐foot. 相似文献
985.
David L. Rosgen 《Journal of the American Water Resources Association》2008,44(3):782-792
986.
987.
Zhi‐Jun Liu Donald E. Weller Thomas E. Jordan David L. Correll Kathleen B. Boomer 《Journal of the American Water Resources Association》2008,44(3):700-723
Abstract: We present a simple modular landscape simulation model that is based on a watershed modeling framework in which different sets of processes occurring in a watershed can be simulated separately with different models. The model consists of three loosely coupled submodels: a rainfall‐runoff model (TOPMODEL) for runoff generation in a subwatershed, a nutrient model for estimation of nutrients from nonpoint sources in a subwatershed, and a stream network model for integration of point and nonpoint sources in the routing process. The model performance was evaluated using monitoring data in the watershed of the Patuxent River, a tributary to the Chesapeake Bay in Maryland, from July 1997 through August 1999. Despite its simplicity, the landscape model predictions of streamflow, and sediment and nutrient loads were as good as or better than those of the Hydrological Simulation Program‐Fortran model, one of the most widely used comprehensive watershed models. The landscape model was applied to predict discharges of water, sediment, silicate, organic carbon, nitrate, ammonium, organic nitrogen, total nitrogen, organic phosphorus, phosphate, and total phosphorus from the Patuxent watershed to its estuary. The predicted annual water discharge to the estuary was very close to the measured annual total in terms of percent errors for both years of the study period (≤2%). The model predictions for loads of nutrients were also good (20‐30%) or very good (<20%) with exceptions of sediment (40%), phosphate (36%), and organic carbon (53%) for Year 1. 相似文献
988.
989.
Volatile Organic Compounds (VOCs) in the air provoke health and environmental concerns. This paper focuses on the absorption method to treat industrial polluted air loaded with VOCs. The key variable of this treatment being the choice of a suitable liquid absorbent, the aim of this research work is to investigate the effectiveness and the regeneration of a new potential family of absorbent: cyclodextrins (CDs). All CDs derivatives tested are able to decrease the Henry's law constant of toluene: a reduction of volatility up to 95% may be obtained, depending on CD nature and concentration. Moreover, absorption experiments show that beta-CD, which presents the highest absorption ability, is 250 time more efficient than water. The absorption efficiency is not totally correlated with static experiments, suggesting that, in addition to Henry's law constants and inclusion compounds stability, toluene diffusion into such solutions has to be taken into account. It is also to be noted that salt and pH variations seem to have little influence on the absorption capacity of CDs, which may be of great interest for industrial applications. Finally, since production of solid compounds was not observed during these experiments and since temperature decreases the capture ability in a drastic way, regeneration of the washing solution can be achieved by heating the solution in combination with air stripping. 相似文献
990.
Organic matter has long been recognized as the main sorbent phase in soils for hydrophobic organic compounds (HOCs). In recent times, there has been an increasing realization that not only the amount, but also the chemical composition, of organic matter can influence the sorption properties of a soil. Here, we show that the organic carbon-normalized sorption coefficient (K(OC)) for diuron is 27-81% higher in 10 A11 horizons than in 10 matching A12 horizons for soils collected from a small (2ha) field. K(OC) was generally greater for the deeper (B) horizons, although these values may be inflated by sorption of diuron to clays. Organic matter chemistry of the A11 and A12 horizons was determined using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. K(OC) was positively correlated with aryl C (r2=0.59, significance level 0.001) and negatively correlated with O-alkyl C (r2=0.84, significance level <0.001). This is only the second report of correlations between whole soil K(OC) and NMR-derived measures of organic matter chemistry. We suggest that this success may be a consequence of limiting this study to a very small area (a single field). There is growing evidence that interactions between organic matter and clay minerals strongly affect K(OC). However, because the soil mineralogy varies little across the field, the influence of these interactions is greatly diminished, allowing the effect of organic matter chemistry on K(OC) to be seen clearly. This study in some way reconciles studies that show strong correlations between K(OC) and the chemistry of purified organic materials and the general lack of such correlations for whole soils. 相似文献