全文获取类型
| 收费全文 | 552篇 |
| 免费 | 49篇 |
| 国内免费 | 8篇 |
专业分类
| 安全科学 | 59篇 |
| 废物处理 | 10篇 |
| 环保管理 | 121篇 |
| 综合类 | 240篇 |
| 基础理论 | 53篇 |
| 污染及防治 | 26篇 |
| 评价与监测 | 32篇 |
| 社会与环境 | 29篇 |
| 灾害及防治 | 39篇 |
出版年
| 2025年 | 4篇 |
| 2024年 | 10篇 |
| 2023年 | 15篇 |
| 2022年 | 13篇 |
| 2021年 | 14篇 |
| 2020年 | 17篇 |
| 2019年 | 27篇 |
| 2018年 | 14篇 |
| 2017年 | 16篇 |
| 2016年 | 23篇 |
| 2015年 | 15篇 |
| 2014年 | 24篇 |
| 2013年 | 21篇 |
| 2012年 | 26篇 |
| 2011年 | 35篇 |
| 2010年 | 19篇 |
| 2009年 | 26篇 |
| 2008年 | 25篇 |
| 2007年 | 28篇 |
| 2006年 | 25篇 |
| 2005年 | 19篇 |
| 2004年 | 12篇 |
| 2003年 | 13篇 |
| 2002年 | 10篇 |
| 2001年 | 13篇 |
| 2000年 | 23篇 |
| 1999年 | 17篇 |
| 1998年 | 13篇 |
| 1997年 | 13篇 |
| 1996年 | 14篇 |
| 1995年 | 7篇 |
| 1994年 | 8篇 |
| 1993年 | 6篇 |
| 1992年 | 5篇 |
| 1991年 | 4篇 |
| 1990年 | 1篇 |
| 1989年 | 4篇 |
| 1988年 | 5篇 |
| 1986年 | 1篇 |
| 1985年 | 13篇 |
| 1984年 | 2篇 |
| 1982年 | 1篇 |
| 1981年 | 2篇 |
| 1979年 | 1篇 |
| 1978年 | 2篇 |
| 1976年 | 2篇 |
| 1972年 | 1篇 |
排序方式： 共有609条查询结果，搜索用时 15 毫秒
471.
A. Ramachandra Rao Srinivasa G. Rao R. L. Kashyap 《Journal of the American Water Resources Association》1985,21(5):757-770
Stochastic models fitted to hydrologic data of different time scales are interrelated because the higher time scale data (aggregated data) are derived from those of lower time scale. Relationships between the statistical properties and parameters of models of aggregated data and of original data are examined in this paper. It is also shown that the aggregated data can be more accurately predicted by using a valid model of the original data than by using a valid model of the aggregated data. This property is particularly important in forecasting annual values because only a few annual values are usually available and the resulting forecasts are relatively inaccurate if models based only on annual data are used. The relationships and forecasting equations are developed for general aggregation time and can be used for hourly and daily, daily and monthly or monthly and yearly data. The method is illustrated by using monthly and yearly streamflow data. The results indicate that various statistical characteristics and parameters of the model of annual data can be accurately estimated by using the monthly data and forecasts of annual data by using monthly models have smaller one step ahead mean square error than those obtained by using annual data models. 相似文献
472.
William H. Bruvold Bruce R. Smith 《Journal of the American Water Resources Association》1988,24(3):661-669
ABSTRACT: Relevant literature was reviewed from which a model of residential water conservation was developed. Four residential conservation program interventions were posited: 1) public education, 2) pricing variables, 3) water use restrictions, and 4) building code requirements. Four exogenous variables affecting residential water use were also posited: 1) temperature, 2) rainfall, 3) household income, and 4) household size. The impacts of these eight variables on residential per capita daily use were assessed by cross sectional and time series analysis. Study results generally supported the porposed model, with less consistent support obtained for pricing variables and conservation beliefs. The paper concludes with the hypothesis that an inclining block rate structure coupled with an informational program designed to inform consumers of their consumption under each block will have a synergistic impact. 相似文献
473.
Yihun Taddele Dile Raghavan Srinivasan 《Journal of the American Water Resources Association》2014,50(5):1226-1241
Data scarcity has been a huge problem in modeling the water resources of the Upper Blue Nile basin, Ethiopia. Satellite data and different statistical methods have been used to improve the quality of conventional meteorological data. This study assesses the applicability of the National Centers for Environmental Prediction's Climate Forecast System Reanalysis (CFSR) climate data in modeling the hydrology of the region. The Soil and Water Assessment Tool was set up to compare the performance of CFSR weather with that of conventional weather in simulating observed streamflow at four river gauging stations in the Lake Tana basin — the upper part of the Upper Blue Nile basin. The conventional weather simulation performed satisfactorily (e.g., NSE ≥ 0.5) for three gauging stations, while the CFSR weather simulation performed satisfactorily for two. The simulations with CFSR and conventional weather yielded minor differences in the water balance components in all but one watershed, where the CFSR weather simulation gave much higher average annual rainfall, resulting in higher water balance components. Both weather simulations gave similar annual crop yields in the four administrative zones. Overall the simulation with the conventional weather performed better than the CFSR weather. However, in data‐scarce regions such as remote parts of the Upper Blue Nile basin, CFSR weather could be a valuable option for hydrological predictions where conventional gauges are not available. 相似文献
474.
Pamela J. Lombard David J. Holtschlag 《Journal of the American Water Resources Association》2018,54(4):949-961
We test the use of a mixed‐effects model for estimating lag to peak for small basins in Maine (drainage areas from 0.8 to 78 km2). Lag to peak is defined as the time between the center of volume of the excess rainfall during a storm event and the resulting peak streamflow. A mixed‐effects model allows for multiple observations at sites without violating model assumptions inherent in traditional ordinary least squares models, which assume each observation is independent. The mixed model includes basin drainage area and maximum 15‐min rainfall depth for individual storms as explanatory features. Based on a remove‐one‐site cross‐validation analysis, the prediction errors of this model ranged from ?42% to +73%. The mixed model substantially outperformed three published models for lag to peak and one published model for centroid lag for estimating lag to peak for small basins in Maine. Lag to peak estimates are a key input to rainfall–runoff models used to design hydraulic infrastructure. The improved accuracy and consistency with model assumptions indicates that mixed models may provide increased data utilization that could enhance models and estimates of lag to peak in other regions. 相似文献
475.
《环境科学学报(英文版)》2023,35(4):506-516
Deterioration of surface ozone (O3) pollution in Northern China over the past few years received much attention. For many cities, it is still under debate whether the trend of surface O3 variation is driven by meteorology or the change in precursors emissions. In this work, a time series decomposition method (Seasonal-Trend decomposition procedure based on Loess (STL)) and random forest (RF) algorithm were utilized to quantify the meteorological impacts on the recorded O3 trend and identify the key meteorological factors affecting O3 pollution in Tianjin, the biggest coastal port city in Northern China. After “removing” the meteorological fluctuations from the observed O3 time series, we found that variation of O3 in Tianjin was largely driven by the changes in precursors emissions. The meteorology was unfavorable for O3 pollution in period of 2015-2016, and turned out to be favorable during 2017-2021. Specifically, meteorology contributed 9.3 µg/m3 O3 (13%) in 2019, together with the increase in precursors emissions, making 2019 to be the worst year of O3 pollution since 2015. Since then, the favorable effects of meteorology on O3 pollution tended to be weaker. Temperature was the most important factor affecting O3 level, followed by air humidity in O3 pollution season. In the midday of summer days, O3 pollution frequently exceeded the standard level (>160 µg/m3) at a combined condition with relative humidity in 40%-50% and temperature > 31°C. Both the temperature and the dryness of the atmosphere need to be subtly considered for summer O3 forecasting. 相似文献
476.
477.
We examine hourly ozone data collected in connection with a model evaluation study for ozone transport in the San Joaquin Valley of California. A space-time analysis of a subset of the data, 17 sites concentrated around the Sacramento area, indicates a relatively simple spatial covariance structure at night-time, while the afternoon readings show a more complex spatial covariance, which is partly explained by observations from a single station with suspicious data. Simple separable space-time covariance models do not appear applicable to these data. 相似文献
478.
交通事故损失的时间序列分析 总被引：4，自引：4，他引：0
为揭示交通事故经济损失的变化规律,笔者研究并利用时间序列的方法,建立了ARIMA模型,对1985-2005年全国交通事故经济损失的数据进行了分析和预测.根据原始数据的特点,选择随机时间序列分析方法.通过对模型的识别和参数的选择,得到2006-2008年的交通事故损失的预测值分别为2.955 9,2.970 7和3.012 9亿元,置信区间为95%.通过对1985-2005年交通事故经济损失的预测结果与原始数据的比较表明,预测结果接近原始数据,该方法为交通事故的预防和控制提供了技术指导和有益参考. 相似文献
479.
为提高水电工程施工安全隐患治理水平,分析水电工程施工安全隐患非线性时间序列特点,基于可视图算法构建隐患时间序列的复杂网络模型,挖掘某水电站2016—2020年3 160条施工安全隐患排查数据,计算安全隐患时间序列网络的度及度分布、幂律指数、聚类系数、网络直径、平均路径长度等网络特征参数,揭示水电工程施工安全隐患发生的时间规律特性。结果表明:该水电工程的施工安全隐患发现时间表现出显著阶段性、无标度性和小世界性等演化特征。隐患时间间隔过长会极大地削弱整个水电工程建设安全隐患管理的鲁棒性,及时管控少数关键时间节点,可降低水电工程安全隐患风险。 相似文献
480.
基于激波管的油气爆炸实验和数据分析 总被引：1，自引：0，他引：1
通过对封闭激波管的油气爆炸实验,发现了爆炸时存在"呼吸"现象和震荡现象。通过对爆炸时的压力时间序列分析,除了得到了不同位置压力数量变化特征外,还得到了"呼吸"现象与油气的CH浓度和生成的二氧化碳浓度有关;在不同的CH浓度下,存在三种典型的压力变化曲线;震荡现象与CH浓度有关,没有固定的震荡周期,而且在不同压力变化阶段存在不同的震荡情况等结论。 相似文献