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651.
652.
Copper adsorption by vineyard soils of the Geneva canton was evaluated by batch equilibration experiments in a pH range from 4 to 6. The adsorption curves fit significantly to Freundlich function log q = n log C + log Kf, where q is adsorbed Cu concentration on the solid phase and C is solution Cu concentration at the end of the equilibration time. Moreover, we found that Freundlich parameters n and log Kf are moderately correlated to pH, yielding the following equations: log Kf = 0.23 pH + 0.51 (R
2 0.59) and n = –0.12 pH + 1.06 (R
2 0.59). Such equations may be useful to predict Cu mobility for risk assessment studies. 相似文献
653.
McGill RA Pearce JM Fortey NJ Watt J Ault L Parrish RR 《Environmental geochemistry and health》2003,25(1):25-32
By combining scanning electron microscopy (SEM) image analysis and laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS), high precision lead isotope analyses can be obtained from individual metal-rich particles. Soils from Wolverhampton and Nottingham were sampled on the basis of high Pb concentrations or brownfield location. Pressed powder pellets of each were rastered by LA-PIMMS to obtain a bulk Pb-isotope signature. The results plot along an apparent mixing line between the major sources of lead contamination in the UK, that is UK ore deposits and alkyl-lead from petrol additives (Australian ore). Two particularly lead-rich soils were chosen to investigate the lead distribution and isotope variability between size and density fractions. The fine-grained and low-density fractions contained most of the lead and have Pb-isotope ratios comparable with the bulk soils. By contrast, the small, lead-enriched denser fractions contained only a minor proportion of the total lead but Pb-isotope signatures indicating relative enrichment in one or other of the end-members from the mixing line. Further characterisation of individual Pb-rich grains is in progress. 相似文献
654.
Estimating the area affected by phosphorus runoff in an Everglades wetland: a comparison of universal kriging and Bayesian kriging 总被引:2,自引:0,他引:2
Phosphorus-enriched agriculture runoff is believed to be the leading cause of ecosystem changes of Everglades wetlands. To study this effect, it is necessary to estimate the area of the affected region. In this study, Bayesian kriging and universal kriging were used to estimate the area by analysing the data collected by Reddy et al. (1991). The background level of the soil's total phosphorus concentration is usedto determine whether the region is affected by the agriculture runoff, through an indicator function. The area of the affected region was represented by the integration of the indicator function over the entire wetland. The expected value of the affected area was calculated using the results derived from Bayesian and universal kriging. The outcome indicates that universal kriging is sensitive to specification of thecovariance model. It was observed that universal kriging and Bayesian kriging yield comparable results, if the specified covariance structures are of similar nature. 相似文献
655.
Simmons RW Pongsakul P Saiyasitpanich D Klinphoklap S 《Environmental geochemistry and health》2005,27(5-6):501-511
Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence
communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous
mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual
entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated
rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken.
Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg−1 and 100 to 8036 mg kg−1, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to
fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity
to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading
associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged
from 0.05 to 7.7 mg kg−1. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives
and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg−1. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body.
This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based
field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values
via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated
rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate
the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’
areas. 相似文献
656.
多氯联苯复合污染土壤的微生物群落结构多样性变化 总被引:2,自引:0,他引:2
土壤微生物群落结构多样性是指示土壤生态系统稳定性及其功能的重要传感器。采用磷脂脂肪酸(Phospholipid fatty acids,PLFAs)方法,对长江三角洲地区某POPs高风险区PCBs长期复合污染土壤的微生物群落结构多样性进行了初步研究。结果表明,PCBs重度污染土壤中格兰氏阴性菌(16:1w9、cy17:0等)和厌氧微生物(18:1w7)的PLFAs组分含量较多,而格兰氏阳性菌(如i15:0、i17:0等)、放线菌(16:0(10Me))及真菌(18:2ω6,9)和好氧性微生物的PLFAs含量较低,表明PCBs污染土壤中微生物群落结构与组成发生了明显变化。这一结果为PCBs降解微生物资源的定向筛选提供了科学依据。 相似文献
657.
Lynn A. Brandvold Barbara R. Popp Sandra J. Swartz 《Environmental geochemistry and health》1996,18(1):1-4
Two primary lead smelters and one secondary lead smelter have been active in the Socorro, New Mexico (USA) area in the last 110 years: the Billing smelter from 1883 to 1894, the Cuba Road smelter from 1881 to 1900, and Cal West from 1979 to 1984. Samples of plants and surface soil under each plant from all three sites were analysed for lead. The plants consisted of sparse grasses, cacti, creosote bush, snakeweed, mesquite and fourwing saltbush. Lead levels in the plants increased (2-440 g g–1) as the lead in the alkaline soils (25-10000 ng g–1) increased. However, the BAC (biological absorption coefficient), which is the ratio of lead content in the plant to the lead content in the soil, a measure of relative accumulation, decreased by one to two orders of magnitude, except for grasses and snakeweed. At background lead levels, there was little difference between lead in rootsversus foliage. At high lead levels, there was higher lead in roots versus foliage at the Billing and Cuba Road sites. The reverse was noted at Cal West. Because this is a recent operation, the higher lead in foliage may be due to foliar uptake. Plant growth at all sites appeared healthy. 相似文献
658.
Arun Kumar Rath B. Ramakrishnan N. Sethunathan 《Agriculture, ecosystems & environment》2002,90(3):319-325
Agricultural sources of atmospheric methane include flooded rice (Oryza sativa L.) paddies. However, certain soil nutrient management and cultural practices offer opportunities to reduce methane emissions. The effect of application of ammonium thiosulphate, a potential source of nitrogen and sulphur and also an inhibitor of nitrification and urease on methane production and emission from flooded alluvial (Typic Haplaquept) rice soil in India, was examined. Methane production and emission from control and urea-amended soil samples were almost identical. Application of ammonium thiosulphate to laboratory-incubated flooded soil (30 and 60 μg N g−1 soil) and flooded rice fields (45.6 and 60 kg N ha−1) effected a distinct inhibition of methane production and emission. Ammonium thiosulphate stimulated the population of sulphate-reducing bacteria (SRB) to a greater extent at 60 μg N g−1 soil than at 30 μg N g−1 soil. In ammonium thiosulphate-applied rice field plots, mean methane efflux decreased by about 38 and 60% at 45.6 and 60 kg N ha−1, respectively, over that of control. Inhibition of methane production by ammonium thiosulphate is, at least in part, due to the stimulation of SRB. Results suggest the mitigation potential of ammonium thiosulphate on methane emission from flooded rice paddies. 相似文献
659.
660.
K.M.S. Sundaram 《Journal of environmental science and health. Part. B》2013,48(3):415-442
Abstract Adsorption‐desorption behavior of RH‐5992 [Mimic®, N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyl) hydrazine] in sandy and clay loam forest soils was studied using the batch equilibrium method. Adsorption was higher in the clay loam soil than in the sandy loam, and increased linearly with RH‐5992 concentration, but decreased with increasing pH and temperature. The adsorption data fit better to the Freundlich, than to the Langmuir equation. The KD (linear adsorption constant) and KF (Freundlich constant) were similar for each soil at 5, 15 and 25°C and decreased with increase of temperature, indicating that the enthalpy of adsorption was negative. The exponent of the Freundlich equation was close to unity for both soils at all three temperatures. The low Ea (energy of activation) indicated a diffusion‐controlled process during the initial stages of adsorption. The desorption isotherm differed from that of adsorption, and the linear desorption constant, KD(d), was ca 25 times higher than the KD, indicating that adsorption of RH‐5992 was not readily reversible. Evaluation of thermo‐dynamic parameters confirmed the presence of strong bonds between the solute and soil. These findings suggest that RH‐5992 has a limited potential for downward mobility leading to groundwater contamination. 相似文献