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731.
Atmospheric phenanthrene pollution modulates carbon allocation in red clover (Trifolium pratense L.)
Desalme D Binet P Epron D Bernard N Gilbert D Toussaint ML Plain C Chiapusio G 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2759-2765
The influence of atmospheric phenanthrene (PHE) exposure (160 μg m−3) during one month on carbon allocation in clover was investigated by integrative (plant growth analysis) and instantaneous 13CO2 pulse-labelling approaches. PHE exposure diminished plant growth parameters (relative growth rate and net assimilation rate) and disturbed photosynthesis (carbon assimilation rate and chlorophyll content), leading to a 25% decrease in clover biomass. The root-shoot ratio was significantly enhanced (from 0.32 to 0.44). Photosynthates were identically allocated to leaves while less allocated to stems and roots. PHE exposure had a significant overall effect on the 13C partitioning among clover organs as more carbon was retained in leaves at the expense of roots and stems. The findings indicate that PHE decreases root exudation or transfer to symbionts and in leaves, retains carbon in a non-structural form diverting photosynthates away from growth and respiration (emergence of an additional C loss process). 相似文献
732.
Likun Xue Tao Wang Isobel. J. Simpson Aijun Ding Jian Gao Donald R. Blake Xuezhong Wang Wenxing Wang Hengchi Lei Dezhen Jin 《Atmospheric environment (Oxford, England : 1994)》2011,45(36):6501-6509
Vertical distributions of air pollutants are crucial for understanding the key processes of atmospheric transport and for evaluating chemical transport models. In this paper, we present measurements of non-methane hydrocarbons (NMHCs) and halocarbons obtained from an intensive aircraft study over northeast (NE) China in summer 2007. Most compounds exhibited a typical negative profile of decreasing mixing ratios with increasing altitude, although the gradients differed with different species. Three regional plumes with enhanced VOC mixing ratios were discerned and characterized. An aged plume transported from the northern part of the densely populated North China Plain (NCP; i.e. Beijing–Tianjin area) showed relatively higher levels of HCFC-22, 1,2-dichloroethane (1,2-DCE) and toluene. In comparison, the plume originating from Korea had higher abundances of CFC-12, tetrachloroethene (C2Cl4) and methyl chloride (CH3Cl), while regional air masses from NE China contained more abundant light alkanes. By comparing these results with the earlier PEM-West B (1994) and TRACE-P (2001) aircraft measurements, continuing declining trends were derived for methyl chloroform (CH3CCl3), tetrachloromethane (CCl4) and C2Cl4 over the greater China–northwestern Pacific region, indicating the accomplishment of China in reducing these compounds under the Montreal protocol. However, the study also provided evidence for the continuing emissions of several halocarbons in China in 2007, such as CFCs (mainly from materials in stock) and HCFCs. 相似文献
733.
Lakhani A Parmar RS Satsangi GS Prakash S 《Environmental monitoring and assessment》2007,133(1-3):435-445
Fog water samples were collected in the months of December and January during 1998–2000 at Agra, India. The samples were analyzed
for pH, major anions (F−, Cl−, SO4
2−, NO3
−, HCOO− and CH3COO−), major cations (Ca2+, Mg2+, Na+ and K+) and NH4
+ using ion chromatography, ICP-AES and spectrophotometer methods, respectively. pH of fog water samples ranged between 7.0
and 7.6 with a volume weighted mean of 7.2, indicating its alkaline characteristic. NH4
+ contributed 40%, SO4
2− and NO3
− accounted for 28%, while Ca2+, Mg2+, Na+ and K+ accounted for 16% of the total ionic concentration. The ratios of Mg2+/Ca2+ and Na+/Ca2+ in fog water indicates that 50–75% of fog water samples correspond to the respective ratios in local soil. Significant correlation
between Ca2+, Mg2+, Na+ and K+ suggests their soil origin. The order of neutralization, NH4
+ (1.4) > Ca2+ (0.28) > Mg2+ (0.12), indicates that NH4
+ is the major neutralizing species. Fog water and atmospheric alkalinity were also computed and were found to be 873 and 903 neqm−3, respectively. Both of these values are higher than values reported from temperate sites and thus indicate that at the present
level of pollutants, there is no risk of acid fog problem. The study also shows that the alkaline nature of fog water is due
to dissolution of ammonia gas and partly due to interaction of fog water with soil derived aerosols. 相似文献
734.
This research proposes an integrated framework to investigate human-dominated systems and provide a basic approach to urban
and regional studies in which the multiple interactions between economic and ecological processes are considered as a whole.
Humans generate patterns of land use, infrastructures and other settings and redistribute ecosystem functions as flows of
energy and matter for self-maintenance. To understand these emerging interactions between humans and ecological processes,
human activities (e.g. transformation processes, land conversions, use of resources) and biophysical agents such as geomorphology,
climate and natural cycles need to be considered. Emergy Analysis (spelled with an “m”) is then used as an environmental accounting
method to evaluate different categories of resource use with reference to their environmental cost. A case study of the Province
of Cagliari (in the island of Sardinia, Italy) is reported and the procedure for allocating emergy flows, assigning them to
districts and managing point data is discussed. Outcomes plotted on a map showed non-homogeneous spatial distribution of emergy
flows throughout the region, suggesting the way ecosystem functions are affected and restructured by the human economy. 相似文献
735.
Nianliang Cheng Yunting Li Bingfen Cheng Xin Wang Fan Meng Qin Wang Qihong Qiu 《环境科学学报(英文版)》2018,30(7):141-154
Characteristics of two serious air pollution episodes(9–15 January, as the winter case; and30 June to 1 July, as the summer case), which occurred in Beijing in 2013 were investigated and compared using multi-method observations and numerical simulations. During these two air pollution episodes, PM_(2.5) concentrations varied significantly within Beijing, with PM_(2.5) concentrations in southern parts of Beijing being significantly higher than in northern areas. Typically, heavy air pollution episodes begin in the southern parts and disperse towards the northern parts of Beijing. Clearly, synoptic patterns and the stability of atmospheric circulation patterns were the main factors controlling air pollution in Beijing.During the winter case, a warm center above 900 h Pa occurred over Beijing. Meanwhile, in the summer case, although there was only a weak inversion, the convective inhibition energy was strong(over 200 J/k G). This clearly influenced the duration of the air pollution event. Except for the local accumulation and secondary atmospheric reactions in both cases, regional straw burnings contributed a lot to the PM_(2.5) concentrations in summer case.Using the CAMxmodel, we established that regional transport contributed almost 59% to the PM_(2.5) averaged concentration in Beijing in the winter case, but only 31% in the summer case. Thus, the winter case was a typical regional air pollution episode, while the summer case resulted from local accumulation straw burnings transportation and strong secondary atmospheric reactions. Given that air pollution is a regional problem in China, consistent and simultaneous implementation of regional prevention and control strategies is necessary to improve regional air quality. 相似文献
736.
改进遗传神经网络方法在大气环境质量评价中的应用 总被引:8,自引:0,他引:8
运用双极性压缩函数适应度定标和基于排挤方法的选择算子改进标准遗传算法(SGA),使其成为简单通用、快速收敛的并行全局搜索算法。利用该算法优化误差反向传播网络(BPN),克服了BPN收敛慢和不具有全局收敛性的缺陷,在此基础上,建立大气环境质量评价模型,并将该模型用于实例。结果表明,该方法用于大气环境质量评价是可行的。 相似文献
737.
A statistical study was performed over 145 profiles of meteorological balloons, equipped with microthermal sensors, from the
ground to the midstratosphere. This study put into evidence the lognormal distribution of the fluctuations of the structure
constant of temperature, the fluctuations of the buoyancy force and the vertical shear of the horizontal wind speed. We show
that these quantities, computed over a large scale (100 m), are correlated up to the midstratosphere. A model is adjusted
to estimate the optical turbulence strength from the macroscopic meteorological parameters. The model performances, to estimate and forecast the strength and the altitude
of the optical turbulent layers, are quantified and compared with other already defined models. This model was shown to have
the best performances and put into evidence a new relation to describe the turbulence on a large scale. 相似文献
738.
739.
740.
In the period between 1999 and 2000 epiphytic bryophytes were taken as bioindicators for air pollution by use of the IAP method
(Index of Atmospheric Purity) and the VDI method within the Association of Engineers standards list (adapted from guideline
3799, 1995) in the heavy industrialized town of Linz, Austria. 52 study sites (265 trees) were analysed regarding species
richness, coverage, and vitality. Q-values (sensitivity factors), calculated for each species showed significant differences
for the various host tree species. The results gained by the IAP and the VDI methods were diverse, regarding the various sites
where only 25% were classified identical. These differences can mainly be attributed to the differing host tree species and
the size of the recording area on the various trees. Clusters of similar pollution levels were calculated and drawn as maps
for both methods tested. Comparing the results of the IAP and the VDI methods with data derived from technical measurements
(SO2, NO, NO2, and dust) a correlation between IAP-indices and SO2 concentrations could be observed. No correlation was detected between the results derived from VDI recording and for NO,
NO2, and dust. 相似文献