全文获取类型
| 收费全文 | 582篇 |
| 免费 | 94篇 |
| 国内免费 | 12篇 |
专业分类
| 安全科学 | 110篇 |
| 废物处理 | 1篇 |
| 环保管理 | 81篇 |
| 综合类 | 305篇 |
| 基础理论 | 99篇 |
| 环境理论 | 1篇 |
| 污染及防治 | 28篇 |
| 评价与监测 | 13篇 |
| 社会与环境 | 25篇 |
| 灾害及防治 | 25篇 |
出版年
| 2025年 | 3篇 |
| 2024年 | 14篇 |
| 2023年 | 15篇 |
| 2022年 | 15篇 |
| 2021年 | 21篇 |
| 2020年 | 27篇 |
| 2019年 | 30篇 |
| 2018年 | 24篇 |
| 2017年 | 35篇 |
| 2016年 | 35篇 |
| 2015年 | 24篇 |
| 2014年 | 25篇 |
| 2013年 | 34篇 |
| 2012年 | 29篇 |
| 2011年 | 41篇 |
| 2010年 | 23篇 |
| 2009年 | 24篇 |
| 2008年 | 23篇 |
| 2007年 | 33篇 |
| 2006年 | 26篇 |
| 2005年 | 22篇 |
| 2004年 | 26篇 |
| 2003年 | 11篇 |
| 2002年 | 11篇 |
| 2001年 | 11篇 |
| 2000年 | 19篇 |
| 1999年 | 10篇 |
| 1998年 | 14篇 |
| 1997年 | 11篇 |
| 1996年 | 9篇 |
| 1995年 | 7篇 |
| 1994年 | 9篇 |
| 1993年 | 2篇 |
| 1992年 | 6篇 |
| 1991年 | 2篇 |
| 1990年 | 4篇 |
| 1989年 | 2篇 |
| 1988年 | 1篇 |
| 1987年 | 2篇 |
| 1985年 | 1篇 |
| 1982年 | 1篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1977年 | 1篇 |
| 1976年 | 1篇 |
| 1970年 | 1篇 |
| 1969年 | 1篇 |
排序方式： 共有688条查询结果，搜索用时 0 毫秒
71.
Soil acidification caused by acid deposition has been significant in some forests in southern China. We present an approach for assessing the current stage maximum allowed load (SML) of acid deposition for terrestrial system in the country. The main idea was that soil base cation exchange as a finite buffer to acidity was included in the soil acidity mass balance calculation at current acidification stage. We calculated the SML for five forests in southern China. The usual critical loads for the same forests were also calculated by the steady state mass balance model for comparison. The results showed that the SML is a more tolerant limit than the critical load for the forests with soils not acidified seriously at current stage. However, the SML become a more stringent limit to acid deposition when the forest soils have acidified seriously to very low base cation saturation. In this case the SML assessment is beneficial for the soils recovering from a serious acidified state. Based on a national scale database, the SML mapping for non-agricultural soil system in China was carried out. 相似文献
72.
青藏高原西北部近地表气温直减率时空分布特征 总被引：1，自引：1，他引：1
近地表气温直减率是研究山地生态系统对气候变化响应过程中的重要参数,论文基于青藏高原西北部1951—2013年的9个标准气象站以及2012—2016年的高山自设观测站的日平均气温、最低气温、最高气温（Tave、Tmin、Tmax）数据,分析了青藏高原西北部近地表气温直减率（LRTave、LRTmin、LRTmax）的时空分布特征。结果表明：1）青藏高原西北部近地表气温随高程增大有显著下降趋势。研究区两个区域的LRTave、LRTmin、LRTmax均呈现出显著的空间差异性,而基于气象站的LRTave、LRTmin高于高山观测站的LRTave、LRTmin、LRTmax,其中LRTmin差异最为显著,而LRTmax空间差异较小。2）青藏高原西北部近地表气温直减率具有明显的季节差异,气象站的LRTave、LRTmin、LRTmax季节变化趋势为春季高、夏季较高、冬季低,而高山观测站的LRTave、LRTmin、LRTmax季节变化趋势为夏季高、冬季低。其中气象站LRTmax在四季中的差异最显著,而高山观测站的LRTmin的季节差异最大。高山观测站的气温直减率在4—9月间具有较为稳定的值。3）青藏高原西北部LRTave、LRTmin在气温突变年前后具有显著的差异,LRTmax无显著的变化。其中,在气温突变年之后,LRTave、LRTmin有显著的上升趋势,表明青藏高原西北部地区的LRTave、LRTmin对区域气候变化的响应显著,而LRTmax对区域气候变化的响应不显著。研究将有效改善青藏高原西北部气温空间分布规律研究的不足,为区域气候变化研究及生态系统对气候响应等定量研究提供理论基础。 相似文献
73.
Nobutane Hanayama 《Environmetrics》2004,15(3):219-232
In the field of breast cancer study, it has become accepted that crucial exposures to environmental risks might have occurred years before a malignant tumor is evident in human breasts, while age factors such as ages at menstruation have been known as risks for the disease already. To project trends in two such kinds of risks for the disease, the concept of environment effects is introduced for (age, period)‐specific breast cancer mortality rates. Also, a new model, named the age–environment (AE) model, which assumes that the logarithm of the expected rate is a linear function of environment effects and age effects, is proposed. It is shown that, although environment effects have different meanings from period effects or cohort effects, in the age–period–cohort (APC) model, the range space of the design matrix for the AE model is included in that for APC model. It is seen, however, that the AE model provides a better fit to the data for females in Japan and the four Nordic countries than does the APC model in terms of AIC. From the results of ML estimation of the parameters in the AE model based on the data obtained in Japan, we see high levels of environment effects associated with the Sino–Japanese war, World War II and the environmental pollution due to the economy in the recovery period from the defeat. Besides, from those based on the data obtained in the four Nordic countries, we see high levels of environment effects associated with the environment becoming worse after the year of Helsinki Olympics and low levels of them associated with the period including the year of ‘Miracle of the Winter War’ in Finland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
74.
This article is concerned with the estimation of the mean μ and standard deviation σ utilizing a singly‐left‐censored sample of normally distributed data having a known detection limit (DL). A new computer algorithm for obtaining the Cohen ( 1959 ) maximum likelihood estimates of μ and σ is provided which does not require auxiliary tables. The algorithm utilizes S‐PLUS or R languages. Closed form estimates of the mean and standard deviation obtained under a new replacement method are given for normally distributed left‐censored samples, which appear to be superior to existing replacement method estimates. The replacement method estimates are based on replacing the left‐censored observations by a non‐constant value. The performances of these methods are compared utilizing many simulated data sets. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
75.
Moisture contained in an Eulerian atmospheric column is modelled as a stochastic process obtained from gluing together two diffusion processes along the branches of a certain graph. The glued diffusions are solutions of two stochastic differential equations, each one governing the budget of moisture content during dry and wet epochs of the column, respectively. The model accounts for the intermittent behaviour of rainfall, via a hysteresis effect of moisture content between two fixed threshold values. Explicit probability density functions are obtained for the random duration of dry and wet epochs. The statistical method of maximum likelihood and the method of moments are used for estimation of the model's parameters, based on TOGA-COARE measurements of rainfall in a certain tropical region. Testing goodness-of-fit is also performed for the parametric density estimates. © 1997 John Wiley & Sons, Ltd. 相似文献
76.
Serge B. Provost 《Environmetrics》1991,2(4):487-496
The likelihood ratio criterion for testing the mutual independence of q subvectors of an l-dimentional normal vector on the basis of a sample of size N on l components and of an incomplete sample of size M on r components (r < l). This is equivalent to testing the hypothesis that each variable in one subvector is uncorrelated with each variable in the other subvectors. This asymptotic distribution of the test statistic is given. 相似文献
77.
Samin Raziperchikolaee Ola Babarinde Joel Sminchak Neeraj Gupta 《Greenhouse Gases: Science and Technology》2019,9(6):1247-1265
Understanding the distribution and orientation of natural fractures within Knox Groups is of significance in seeking potential CO2 storage zones with high practical storage capacity. Over 700 observations of natural fractures were interpreted on acquired resistivity and acoustic image logs collected at multiple well locations ranging in depth from 730 to 3900 m in the Knox Group interval on the western flank of Appalachian Basin. We evaluated the structural parameters of the fractures using statistical analysis. Natural fracture intensity was observed to increase up‐dip within the studied area. The present day maximum horizontal stress direction was derived using the interpretation of wellbore breakouts and drilling‐induced tensile fractures in image logs. Overall, a high percentage of fractures with varying dip directions were observed to strike subparallel to the contemporary maximum horizontal stress direction. Multiphase flow–geomechanics coupled numerical simulations and poromechanics analytical solutions were then used to study pressure and stress response of CO2 injection into the fractured Knox reservoirs. In addition, we applied a dual permeability model combined with a fracture activation model to study the permeability enhancement and its effect on injection mass increase. We also showed the line source injection solution can reasonably predict stress changes of CO2 injection into the deep saline formations. Results were analyzed to understand the potential effect of natural fractures in sandstone formations and fractured layers in thick carbonate formations on CO2‐injected mass, time‐dependent stress evolution, and the ratio of stress to pore pressure changes. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd. 相似文献
78.
Three approaches to modelling spatial data in which simulation plays a vital role are described and illustrated with examples. The first approach uses flexible regression models, such as generalized additive models, together with locational covariates to fit a surface to spatial data. We show how the bootstrap can be used to quantify the effects of model selection uncertainty and to avoid oversmoothing. The second approach, which is appropriate for binary data, allows for local spatial correlation by the inclusion in a logistic regression model of a covariate derived from neighbouring values of the response variable. The resulting autologistic model can be fitted to survey data obtained from a random sample of sites by incorporating the Gibbs sampler into the modelling procedure. We show how this modelling strategy can be used not only to fit the autologistic model to sites included in the survey, but also to estimate the probability that a certain species is present in the unsurveyed sites. Our third approach relates to the analysis of spatio-temporal data. Here we model the distribution of a plant or animal species as a function of the distribution at an earlier time point. The bootstrap is used to estimate parameters and quantify their precision. © 1998 John Wiley & Sons, Ltd. 相似文献
79.
A modification of ranked set sampling (RSS) called moving extremes ranked set sampling (MERSS) is considered parametrically, for the location parameter of symmetric distributions. A maximum likelihood estimator (MLE) and a modified MLE are considered and their properties are studied. Their efficiency with respect to the corresponding estimators based on simple random sampling (SRS) are compared for the case of normal distribution. The method is studied under both perfect and imperfect ranking (with error in ranking). It appears that these estimators can be real competitors to the MLE using (SRS). The procedure is illustrated using tree data. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
80.
The aim of the study is an uncertainty analysis of an air dispersion model. The model used is described in NRPB‐R91 (Clarke, 1979), a model for short and medium range dispersion of radionuclides released into the atmosphere. Uncertainties in the model predictions arise both from the uncertainty of the input variables and the model simplifications, resulting in parameter uncertainty. The uncertainty of the predictions is well described by the credibility intervals of the predictions (prediction limits), which in turn are derived from the distribution of the predictions. The methodology for estimating this distribution consists of running multiple simulations of the model for discrete values of input parameters following some assumed random distributions. The value of the prediction limits lies in their objectivity. However, they depend on the assumed input distributions and their ranges (as do the model results). Hence the choice of distributions is very important for the reliability of the uncertainty analysis. In this work, the choice of input distributions is analysed from the point of view of the reliability of the predictive uncertainty of the model. An analysis of the influence of different assumptions regarding model input parameters is performed. Of the parameters investigated (i.e. roughness length, release height, wind fluctuation coefficient and wind speed), the model showed the greatest sensitivity to wind speed values. A major influence on the results of the stability condition specification is also demonstrated. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献