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141.
Akira Watanabe Benito H. Purwanto Ho Ando Ken-ichi Kakuda Foh-Shoon Jong 《Agriculture, ecosystems & environment》2009,134(1-2):14-18
Tropical peatland is a vast potential land source for biological production, but peatland is a major natural source of greenhouse gases, especially methane (CH4). It is important to evaluate the changes in greenhouse gas emissions induced by cultivation practices for sustainable agricultural use of tropical peatland. We investigated the effects of fertilizer application and the groundwater level on CH4 and carbon dioxide (CO2) fluxes in an Indonesian peat soil. The crop cultivated was sago palm (Metroxylon sagu Rottb.), which can grow on tropical peat soil without drainage and yield great amounts of starch. CH4 emission through sago palm plants was first estimated by collecting gas samples immediately after cutting sago suckers using the closed chamber method. The CH4 fluxes ranged from negative values to 1.0 mg C m−2 h−1. The mean CH4 flux from treatment with macroelements (N, P, and K) and microelements (B, Cu, Fe, and Zn) applied at normal rates did not differ significantly from that of the No fertilizer treatment, although increasing the application rates of macroelements or microelements by 10-fold increased the CH4 flux by a factor of two or three. The relationship between CH4 flux and the groundwater table was regressed to a logarithmic equation, which indicated that to maintain a small CH4 flux, the groundwater table should be maintained at <−45 cm. The CO2 fluxes ranged between 24 and 150 mg C m−2 h−1, and were not significantly affected by either fertilizer treatments or the groundwater level. The inclusion of sago palm suckers in a chamber increased CH4 emission from the peat soil significantly. Thus, gas emissions mediated by certain kinds of palm plants should not be disregarded. 相似文献
142.
Volatile organic compounds (VOCs) in urban atmosphere of Hong Kong 总被引:21,自引:0,他引:21
The assessment of volatile organic compounds (VOCs) has become a major issue of air quality network monitoring in Hong Kong. This study is aimed to identify, quantify and characterize volatile organic compounds (VOCs) in different urban areas in Hong Kong. The spatial distribution, temporal variation as well as correlations of VOCs at five roadside sampling sites were discussed. Twelve VOCs were routinely detected in urban areas (Mong Kok, Kwai Chung, Yuen Long and Causeway Bay). The concentrations of VOCs ranged from undetectable to 1396 microg/m3. Among all of the VOC species, toluene has the highest concentration. Benzene, toluene, ethylbenzene and xylenes (BTEX) were the major constituents (more than 60% in composition of total VOC detected), mainly contributed from mobile sources. Similar to other Asian cities, the VOC levels measured in urban areas in Hong Kong were affected both by automobile exhaust and industrial emissions. High toluene to benzene ratios (average T/B ratio = 5) was also found in Hong Kong as in other Asian cities. In general, VOC concentrations in the winter were higher than those measured in the summer (winter to summer ratio > 1). As toluene and benzene were the major pollutants from vehicle exhausts, there is a necessity to tighten automobile emission standards in Hong Kong. 相似文献
143.
Ho Ngoc-Ninh Do Truong Lam Tran Dinh-Thao Nguyen Trung Thanh 《Environment, Development and Sustainability》2022,24(1):156-179
Environment, Development and Sustainability - Eliminating ultra-poverty has received particular attention of policymakers and scholars. The ultra-poor in mountainous regions often live on... 相似文献
144.
Marylne Gagn Amy Wei Tian Christine Soo Bo Zhang Khee Seng Benjamin Ho Katrina Hosszu 《组织行为杂志》2019,40(7):783-799
Little research to date has focused on understanding employee motivation to share and hide knowledge. Using self‐determination theory, we tested the premise that knowledge sharing and hiding might be differentially motivated and that work design characteristics might influence the motivation to share knowledge with colleagues. In a panel survey of Australian knowledge workers and in a Chinese knowledge‐intensive organization, we asked knowledge workers, using time‐lagged designs, about perceptions of work design, motivation to share knowledge, and self‐reported knowledge sharing and hiding behaviors. Results, largely replicated across both samples, indicated that cognitive job demands and job autonomy were positively related to future reports of knowledge‐sharing frequency and usefulness via autonomous motivation to share knowledge. Unexpectedly, task interdependence was positively related to the three forms of knowledge hiding (evasive and rationalized hiding, and playing dumb) via external regulation to share knowledge. Implications for the design of jobs that motivate knowledge sharing and demotivate knowledge hiding are discussed. 相似文献
145.
Hao Zheng Jian Cheng Hung Chak Ho Baoli Zhu Zhen Ding Wencong Du Xin Wang Yang Yu Juan Fei Zhiwei Xu Jinyi Zhou Jie Yang 《Frontiers of Environmental Science & Engineering》2023,17(9):105
146.
Although omnivory is common in nature, its impact on trophic interactions is variable. Predicting the food web consequences of omnivory is complicated because omnivores can simultaneously produce conflicting direct and indirect effects on the same species or trophic level. We conducted field and laboratory experiments testing the top-down impacts of an omnivorous salt marsh crab, Armases cinereum, on the shrub Iva frutescens and its herbivorous and predatory arthropod fauna. Armases is a "true omnivore," consuming both Iva and arthropods living on Iva. We hypothesized that Armases would benefit Iva through a top-down trophic cascade, and that this benefit would be stronger than the direct negative effect of Armases on Iva. A field experiment on Sapelo Island, Georgia (USA), supported this hypothesis. Although Armases suppressed predators (spiders), it also suppressed herbivores (aphids), and benefited Iva, increasing leaf number, and reducing the proportion of dead shoots. A one-month laboratory experiment, focusing on the most common species in the food web, also supported this hypothesis. Armases strongly suppressed aphids and consumed fewer Iva leaves if aphids were available as an alternate diet. Armases gained more body mass if they could feed on aphids as well as on Iva. Although Armases had a negative effect on Iva when aphids were not present, Armases benefited Iva if aphids were present, because Armases controlled aphid populations, releasing Iva from herbivory. Although Armases is an omnivore, it produced strong top-down forces and a trophic cascade because it fed preferentially on herbivores rather than plants when both were available. At the same time, the ability of Armases to subsist on a plant diet allows it to persist in the food web when animal food is not available. Because omnivores feed on multiple trophic levels, their effects on food webs may differ from those predicted by standard trophic models that assume that each species feeds only on a single trophic level. To better understand the complexity of real food webs, the variable feeding habits and feeding preferences of different omnivorous species must be taken into consideration. 相似文献
147.
Desorption characteristics of kaolin clay contaminated with zinc from electrokinetic soil processing 总被引:1,自引:0,他引:1
A number of bench scale laboratory column tests were carried out using a newly designed and developed electrokinetic cell
to investigate the fundamental behavior of zinc-spiked kaolin clay subjected to an electric field. Laboratory investigations
focused on (i) zinc migration by the combined effects of electromigration and electro-osmosis and (ii) the electrically induced
desorption characteristics of zinc-contaminated kaolin that occurred during processing. The correlations of the applied voltage
gradient, electro-osmotic flow rate, and the development of a pH gradient were examined and evaluated. The results showed
that the removal efficiency was high during the early stage of processing due to rapid desorption by electrokinetic effects
in the cathode region. However, the majority of zinc migrating from the anode was precipitated due to the high pH environment
in the cathode region. 相似文献
148.
The fate of multiple cyanobacterial metabolites was assessed in two Australian source waters. The saxitoxins were the only metabolites shown to be non-biodegradable in Myponga Reservoir water, while microcystin-LR (MCLR) and geosmin were biodegradable in this water source. Likewise, cylindrospermopsin (CYN) was shown to be biodegradable in River Murray water. The order of ease of biodegradability followed the trend: MCLR > CYN > geosmin > saxitoxins. Biodegradation of the metabolites was affected by temperature and seasonal variations with more rapid degradation at 24 °C and during autumn compared with 14 °C and during winter. A microcystin-degrading bacterium was isolated and shown to degrade four microcystin variants within 4 h. This bacterium, designated as TT25, was shown to be 99% similar to a Sphingopyxis sp. based on a 16S rRNA gene fragment. Isolate TT25 was shown to contain a homologue of the mlrA gene; the sequence of which was 99% similar to that of a previously reported microcystin-degrader. Furthermore, isolate TT25 could degrade the microcystins in the presence of copper sulphate (0.5 mg L−1 as Cu2+) which is advantageous for water authorities dosing such algicides into water bodies to control cyanobacterial blooms. 相似文献
149.
The possible consequences of global warming on plant communities and ecosystems have wide-ranging ramifications. We examined how environmental change affects plant growth as a function of the variations in the microclimate along an urban-suburban climate gradient for two allergy-inducing, invasive plants, Humulus japonicus and Ambrosia artemisiifolia var. elatior. The environmental factors and plant growth responses were measured at two urban sites (Gangbuk and Seongbuk) and two suburban sites (Goyang and Incheon) around Seoul, South Korea. The mean temperatures and CO(2) concentrations differed significantly between the urban (14.8 °C and 439 ppm CO(2)) and suburban (13.0 °C and 427 ppm CO(2)) sites. The soil moisture and nitrogen contents of the suburban sites were higher than those at the urban sites, especially for the Goyang site. The two invasive plants showed significantly higher biomasses and nitrogen contents at the two urban sites. We conducted experiments in a greenhouse to confirm the responses of the plants to increased temperatures, and we found consistently higher growth rates under conditions of higher temperatures. Because we controlled the other factors, the better performance of the two invasive plants appears to be primarily attributable to their responses to temperature. Our study demonstrates that even small temperature changes in the environment can confer significant competitive advantages to invasive species. As habitats become urbanized and warmer, these invasive plants should be able to displace native species, which will adversely affect people living in these areas. 相似文献
150.