全文获取类型
收费全文 | 975篇 |
免费 | 50篇 |
国内免费 | 366篇 |
专业分类
安全科学 | 66篇 |
废物处理 | 55篇 |
环保管理 | 89篇 |
综合类 | 537篇 |
基础理论 | 196篇 |
污染及防治 | 301篇 |
评价与监测 | 30篇 |
社会与环境 | 39篇 |
灾害及防治 | 78篇 |
出版年
2023年 | 17篇 |
2022年 | 53篇 |
2021年 | 40篇 |
2020年 | 30篇 |
2019年 | 27篇 |
2018年 | 46篇 |
2017年 | 48篇 |
2016年 | 51篇 |
2015年 | 71篇 |
2014年 | 82篇 |
2013年 | 103篇 |
2012年 | 97篇 |
2011年 | 98篇 |
2010年 | 69篇 |
2009年 | 61篇 |
2008年 | 69篇 |
2007年 | 61篇 |
2006年 | 41篇 |
2005年 | 37篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 27篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 21篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
排序方式: 共有1391条查询结果,搜索用时 46 毫秒
941.
In China, the health risk from overexposure to particles is becoming an important public health concern. To investigate daily exposure characteristics to PM 2.5 with high ambient concentration in urban area, a personal exposure study was conducted for school children, and office workers in Beijing, China. For all participants (N = 114), the mean personal 24-hr exposure concentration was 102.5, 14.7, 0.093, 0.528, 0.934, 0.174 and 0.703 μg/m 3 for PM 2.5 , black carbon, Mn, Al, Ca, Pb, and Fe. Children's exposure concentrations of PM 2.5 were 4-5 times higher than those in related studies. The ambient concentration of PM 2.5 (128.5 μg/m 3 ) was significantly higher than the personal exposure concentration (P 0.05), and exceed the reference concentration (25 μg/m 3 ) of WHO air quality guideline. Good correlation relationships and significant differences were identified between ambient concentration and personal exposure concentration. The relationships indicate that the ambient concentration is the main factor influencing personal exposure concentration, but is not a good indicator of personal exposure concentration. Outdoor activities (commute mode, exposure to heating, workday or weekend travel) influenced personal exposure concentrations significantly, but the magnitude of the influence from indoor activities (exposure to cooking) was masked by the high ambient concentrations. 相似文献
942.
重庆主城区流域邻苯二甲酸酯生态风险评价 总被引:4,自引:0,他引:4
以长江、嘉陵江重庆主城区段为研究水域,利用Agilent6890N气相色谱仪对丰水期该研究水域12个采样点水体中五种邻苯二甲酸酯(PAEs)含量进行测定,分析了PAEs在该区域水体中丰水期的分布特征并进行了生态安全评价。结果表明:丰水期水体中∑PAEs的浓度范围为0.87μg/L-55.66μg/L;DBP与DEHP为优先污染物,其浓度范围在0.15μg/L-28.32μg/L与0.26μg/L-26.29μg/L;按商值法对PAEs进行生态安全评价,DMP、DEP对该水域中水生动植物无生态风险,DBP和DEHP存在潜在低风险。 相似文献
943.
Integrating Stressor and Response Monitoring into a Resource-Based Water-Quality Assessment Framework 总被引:1,自引:0,他引:1
Dirk J. Roux Phillip L. Kempster Cornelius J. Kleynhans Henk R. Van Vliet Hein H. Du Preez 《Environmental management》1999,23(1):15-30
Following a global trend, the new policy goals emphasize the need to protect rather than to use the ability of ecosystems
to recover from disturbances. This necessitates the adoption of response measurements to quantify ecological condition and
monitor ecological change. Response monitoring focuses on properties that are essential to the sustainability of the ecosystem.
These monitoring tools can be used to establish natural ranges of ecological change within ecosystems, as well as to quantify
conceptually acceptable and unacceptable ranges of change. Through a framework of biological criteria and biological impairment
standards, the results of response monitoring can become an integral part of future water resource management strategies in
South Africa. 相似文献
944.
945.
946.
The forest succession model FORDYN is developed based on TREEDEV model. TREEDEV is a process-based tree growth model, that calculates tree growth based on carbon and nitrogen balance, and is calculated using on the photo-production of leaves, respiration, nitrogen content of all organisms and that in soil, and other losses due to respiration, litter and renewal of stems, branches, leaves and roots. In the FORDYN model succession is divided into three phases called early, middle and late succession, and the transition between these three succession phases is distinguished by a difference in leaf area index. As a verification of the model we used the characteristics and available data of a monsoon evergreen broad-leaved forest in Dinghushan Biosphere Reserve (DHS-BR). The model was validated with natural forest data. In addition, a sensitivity analysis was performed in which 30 independent variables were varied and analyzed in connection with their influence on 16 dependent variables describing forest conditions. The simulation results describe the changes in total biomass, carbon and nitrogen change in plant–litter–soil system of an undisturbed monsoon evergreen broad-leaved forest during succession. We compared these findings with simulation in which different logging management strategies were used. The results show that having a longer logging cycle, delaying the first logging time and a smaller logging fraction the scenario can contribute to a sustainable forest development, while still having a positive economic yield. 相似文献
947.
Michael J. L. Magrath Peter Santema Karen M. Bouwman Dušan M. Brinkhuizen Simon C. Griffith Naomi E. Langmore 《Behavioral ecology and sociobiology》2009,63(5):661-672
Reproductive success within populations often varies with the timing of breeding, typically declining over the season. This
variation is usually attributed to seasonal changes in resource availability and/or differences in the quality or experience
of breeders. In colonial species, the timing of breeding may be of particular importance because the costs and benefits of
colonial breeding are likely to vary over the season and also with colony size. In this study, we examine the relationship
between timing of breeding and reproductive performance (clutch size and nest success) both within and between variable sized
colonies (n = 18) of fairy martins, Petrochelidon ariel. In four of these colonies, we also experimentally delayed laying in selected nests to disentangle the effects of laying
date and individual quality/experience on reproductive success. Within colonies, later laying birds produced smaller clutches,
but only in larger colonies. The general seasonal decline in nest success was also more pronounced in larger colonies. Late
laying birds were generally smaller than earlier laying birds, but morphological differences were also related to colony size,
suggesting optimal colony size also varies with phenotype. Experimentally delayed clutches were larger than concurrently produced
non-delayed clutches, but only in larger colonies. Similarly, delayed clutches were more likely to produce fledglings, particularly
later in the season and in larger colonies. We suggest that the reduced performance of late breeding pairs in larger colonies
resulted primarily from inexperienced/low quality birds preferring to settle in larger colonies, possibly exacerbated by an
increase in the costs of coloniality (e.g., resource depletion and ectoparasite infestations) with date and colony size. These
findings highlight the importance of phenotype-related differences in settlement decisions and reproductive performance to
an improved understanding of colonial breeding and variation in colony size. 相似文献
948.
Soil fertility is conventionally evaluated by soil properties such as C, N, and P contents. Evaluation of soil fertility is
now becoming a routine work for soil management and crop production. However, laboratory-analysis based determination of soil
properties is time and cost consuming, which is not suitable for precision agriculture. Here, infrared spectroscopy (IR) appears
as an alternative and fast technique to measure soil fertility. The IR transmission method is generally used in soil qualitative
analysis, while the IR reflectance can be used in soil quantitative analysis, and most of soil-related research is focused
on reflectance spectroscopy. Infrared reflectance spectra, including diffuse reflectance spectra and total attenuated reflectance
spectra, are involved in soil quantitative analysis. We observe an excellent performance of predicting soil C and N contents
using IR spectra. Moreover, in most of cases the predictions of the contents of soil P, K, Ca, Mg, S, and some other microelements
are satisfactory. Soil water, soil clays, and soil microbes can also be characterized and evaluated using IR spectroscopy.
In recent years, a new method named infrared photoacoustic spectra was applied in soil analysis. Infrared-photoacoustic spectra
is indeed more convenient for sample pretreatment and spectra recording, and the recorded soil spectra contain more useful
information versus conventional reflectance spectroscopy. Though currently the application of infrared photoacoustic spectroscopy
in soil analysis is limited, it appears promising to measure soil fertility. The application of infrared spectroscopy in soil
fertility is largely dependent on spectra pretreatment and multivariate calibration due to strong interferences in the spectra.
Partial least square (PLS) and artificial neural network (ANN) are two widely used mathematical tools in the prediction of
soil properties, and more mathematical tools combined models will benefit the prediction performance. To make full use of
soil infrared spectra, soil spectra library construction is needed in future, and a standard procedure should be first decided
in the construction. Based on soil infrared spectra library soil fertility can be fast evaluated combining suitable mathematical
model, which will play an important role in the sustainable agriculture. 相似文献
949.
950.
Lianfeng Du Jiaojiao Zhao Farhat Abbas Wenke Liu 《Environmental Chemistry Letters》2013,11(4):385-390
This report shows a higher soil quality under medicinal plants versus food-crop plants. Long-term continuous cultivation of food crops induces changes of soil properties that can lead to fertility loss and, in turn, decline of food productivity. Effect of cropping on soil changes has been studied mainly for food crops and vegetables worldwide, whereas soil changes in herbal fields are scarcely known. Therefore, we compared here soil nutrients and soil chemical properties of herbal fields, cultivated with Chinese medicinal plants, and food-crop fields. Fields are located at the famous traditional planting base of Chinese medicinal plants in Anguo, China. The results showed that in herbal fields, soil nitrate, available P, soil organic matter (SOM), and electrical conductivity decreased with soil depth, whereas soil pH and soil water content increased with depth. In herbal fields, soil nitrate, available P contents, and soil electrical conductivity were higher than those of food-crop fields at various soil layers. SOM and soil water content were similar in herbal and food-crop fields. Soil pH of herbal fields at 0–20 cm was lower than those of food-crop fields. Findings show overall that soil nutrient accumulation and changes under medicinal plants are higher than food-crop fields. 相似文献