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811.
812.
Effect of activated sludge treatment on the formation of Nnitrosamines under different chloramination conditions 下载免费PDF全文
Municipal wastewater discharge is considered as one of the main sources of N-nitrosamine precursors which can impact the qualities of downstream source waters and reclaimed wastewaters for potable reuse. NNitrosamine precursors can be removed to various degrees during biological wastewater treatment (e.g., the activated sludge (AS) process). So far, little is known about the impact of the AS process on N-nitrosamine formation under practical disinfection condition (e.g., uniform formation condition (UFC)). In this study, N-nitrosamine UFC from selected model compounds, sewage components (i.e., blackwaters and greywaters) and sewage samples were comprehensively investigated during batch AS treatment tests. NNitrosodimethylamine (NDMA) formation from the tested precursor compounds (i.e., trimethylamine (TMA) and sumatriptan (SMTR)) under UFC chloramination decreased mostly after 6 or 24 hr treatment with different types of AS (i.e., domestic rural AS, domestic urban AS, and textile AS), and the reductions in NDMA UFC were comparable to their NDMA formation potential (FP) reductions. In urine and feces blackwaters, NDMA UFC increased after 6 or 24 hr treatment with the domestic (i.e., rural and urban) AS, while NDMA FP decreased substantially. The increases in NDMA UFC after AS treatment was presumably attributed to the removal of bulk organic matters (e.g., dissolved organic carbon (DOC)) which favored NDMA formation under UFC. On the other hand, in laundry greywaters having relatively abundant DOC, N-nitrosamine UFC was less affected by DOC removal before or after AS treatment, but decreased to similar degrees with N-nitrosamine FP. In sewage samples collected from wastewater treatment plants, N-nitrosamines UFC tended to increase or remain constant during AS treatment, despite the decreases in their FPs. These results suggest that biological wastewater treatment (e.g., the AS process) may not effectively reduce N-nitrosamine formation (e.g., measured under UFC) partially because the concurrent removal of bulk organic matters (e.g., DOC) favored N-nitrosamine formation in s econdary effluents. 相似文献
813.
Modeling of spatial and temporal variations of ozone-NOx-VOC sensitivity based on photochemical indicators in China 下载免费PDF全文
Xiaohui Du Wei Tang Miaomiao Cheng Zhongzhi Zhang Yang Li Yu Li Fan Meng 《环境科学学报(英文版)》2022,34(4):454-464
Comprehensive air quality model with extensions (CAMx)-decoupled direct method (DDM) was used to simulate ozone-NOx-VOCs sensitivity of for May–November in 2016–2018 in China. Based on the relationship between the simulated ozone (O3) sensitivity values and the ratio of formaldehyde (HCHO) to NO2 (FNR) and the ratio of production rate of hydrogen peroxide (H2O2) to production rate of nitric acid (HNO3) (), the localized range of FNR and thresholds in different regions in China were obtained. The overall simulated FNR values are about 1.640–2.520, and values are about 0.540–0.830 for the transition regime. Model simulated O3 sensitivities or region specific FNR or thresholds should be applied to ensure the accurate local O3 sensitivity regimes. Using the tropospheric column FNR values from ozone monitoring instrument (OMI) satellite data as an indicator with the simulated threshold values, the spatial distributions of O3 formation regimes in China are determined. The O3 sensitivity regimes from eastern to central China are gradually from VOC-limited, transition to NOx-limited spatially, and moving toward to transition or NOx-limited regime from 2005 to 2019 temporally. 相似文献
814.
Unravelling the effects of complexation of transition metal ions on the hydroxylation of catechol over the whole pH region 下载免费PDF全文
Zexiu An Jianfei Sun Qiong Mei Bo Wei Mingxue Li Ju Xie Maoxia He Qiao Wang 《环境科学学报(英文版)》2022,34(5):392-402
Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation. 相似文献
815.
Simplified creation of polyester fabric supported Fe-based MOFs by an industrialized dyeing process: Conditions optimization, photocatalytics activity and polyvinyl alcohol removal 下载免费PDF全文
MIL-53(Fe) was successfully prepared and deposited on the surface carboxylated polyester (PET) fiber by an optimized conventional solvothermal or industrialized high temperature pressure exhaustion (HTPE) process to develop a PET fiber supported MIL-53(Fe) photocatalyst ([email protected]) for the degradation of polyvinyl alcohol (PVA) in water under light emitting diode (LED) visible irradiation. On the basis of several characterizations, [email protected] was tested for the photocalytic ability and degradation mechanism. It was found that temperature elevation significantly enhanced the formation and deposition of MIL-53(Fe) with better photocatalytic activity. However, higher temperature than 130°C was not in favor of its photocatalytic activity. Increasing the number of surface carboxyl groups of the modified PET fiber could cause a liner improvement in MIL-53(Fe) loading content and photocatalytic ability. High visible irradiation intensity also dramatically increased photocatalytic ability and PVA degradation efficiency of [email protected] Na2S2O8 was used to replace H2O2 as electron acceptor for further promoting PVA degradation in this system. [email protected] prepared by HTPE process showed higher MIL-53(Fe) loading content and slightly lower PVA degradation efficiency than that prepared by solvothermal process at the same conditions. These findings provided a practical strategy for the large-scale production of the supported MIL-53(Fe) as a photocatalyst in the future. 相似文献