全文获取类型
收费全文 | 372篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 14篇 |
废物处理 | 3篇 |
环保管理 | 56篇 |
综合类 | 30篇 |
基础理论 | 150篇 |
污染及防治 | 100篇 |
评价与监测 | 19篇 |
社会与环境 | 9篇 |
灾害及防治 | 1篇 |
出版年
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 1篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 31篇 |
2012年 | 9篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 21篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有382条查询结果,搜索用时 156 毫秒
41.
42.
The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO2 suspension under UV illumination has been investigated using oxygen (O2) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O2 for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO2–UV–O2 system, while in contrast phthalic acid was found to be the main intermediate product in the TiO2–UV–Fe(VI) system. These findings indicate that DMP degradation in the TiO2–UV–O2 and TiO2–UV–Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO2–UV–O2 reaction system and an unknown radical species (most likely an iron–oxo species) is suspected to exist in the TiO2–UV–Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO2–UV–O2 and TiO2–UV–Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO2–UV–O2 reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO2–UV–Fe(VI) reaction systems attack the alkyl chain of DMP. 相似文献
43.
The ultrastructure of the genera Althornia, Aplanochytrium, Japonochytrium, Schizochytrium and Thraustochytrium is described, and all are regarded as members of the new order Thraustochytriales Sparrow. Species considered are Althornia crouchii, Aplanochytrium kerguelensis, Hyalochlorella marina, Japonochytrium sp., Schizochytrium aggregatum, Thraustochytrium kinnei and T. striatum. All but H. marina are, on ultrastructural evidence, related genera, and some speculative suggestions are made about possible interrelationships both between the species discussed, between the Thraustochytriales and Labyrinthulales, and between these two and other major taxa. 相似文献
44.
45.
46.
Forest networks 总被引:1,自引:1,他引:0
Nigel Dudley 《The Environmentalist》1995,15(3):182-187
Summary A study beyond the political boundaries in planning strategies for long-term management of the global forest estate is presented. Three alternative forest networks are proposed: (1) the genetic-evolutionary network, based around common evolutionary features, thus delineating similar forest types where conservation and management issues are likely to be compatible; (2) the current ecological and environmental network, based around the role that forests play in the wider ecosystem, including regular and irregular migration pathways, networks to absorb the impact of climate change, water filters etc; (3) the human impact network, based on the history of human involvement in the forest and its implications. The practical policy significance of the various networks is discussed in turn.This paper was researched as part of a project carried out for the World Wide Fund for Nature (WWF). Nigel Dudley is an ecologist, based in the UK, with 15 years experience as a consultant for NGOs, local government and international organizations. He is a former director of the Soil Association and now works with Equilibrium Consultants at the above address. For the past five years he has worked closely with WWF on forest conservation projects and has written several reports for the organization, includingForests in trouble: a review of the status of temperate forests worldwide. 相似文献
47.
Phytoplankton assemblages were collected during spring blooms in 1982 in Washington State and in Hawaii. Sinking rate responses of these assemblages were examined under nitrate, phosphate, and silicate depletion. Ambient nutrient concentrations, chlorophyll concentrations, photosynthetic rates, sinking rates, and floristic compositions were determined. Under nutrient-replete conditions, the temperate assemblage, composed primarily of large centric diatoms, had a sinking rate of 0.96 m d-1; sinking rates did not change appreciably over 4 d without nitrate. Without phosphate or silicate, the sinking rates remained constant for 3 d and then increased after biomass indices began to decline. These findings illustrate the potential importance of phosphate or silicate depletion to the sedimentation of spring-bloom diatom populations. The subtropical assemblage, composed primarily of diatoms, coccolithophorids, and dinoflagellates, had an initial sinking rate of 0.22 m d-1 and did not display substantial sinking rate changes in the absence of nitrate, phosphate or silicate. Floristic data consistently showed a proliferation of pennate diatoms, which had lower settling rates than centric diatoms. Growth and sedimentation patterns indicated a competitive advantage for pennate diatom components of subtropical assemblages; this in turn may limit phytoplankton sedimentation losses in such ecosystems. 相似文献
48.
Carbon flow into the end-products of photosynthesis in short and long incubations of a natural phytoplankton population 总被引:4,自引:0,他引:4
During a cruise to the eastern Canadian Arctic (Northern Baffin Bay) in the summer of 1980, we took advantage of the 24-h photoperiod to conduct a 32-h time course experiment of 14C accumulation under natural solar radiation. The degree of non-linearity in the time course was judged against a time-dependent curve of radioactivity constructed by cumulatively adding the amount of 14C taken up in sequential short (2 h) incubations of plankton held in a replicate bottle but left unlabelled until removed for assay. Departure from linearity was due first to decreasing rates of 14C incorporation into polysaccharides and then into lipids. There was a close correspondence between 14C incorporation into proteins in the 32-h incubation and in the sequence of short incubations. These observations are consistent with patterns in utilization of photosynthetic end-products established from laboratory studies of unicellular algal cultures. Based on parallel or independent control experiments, it was judged that complicating factors such as diel light changes, nitrogenous nutrient exhaustion, bottle size effects or inhibitory conterminants in NaH14CO3 stock solutions would not seriously affect our interpretation that non-linearity resulted from catabolic loss of radiocarbon. 相似文献
49.
Inadequacies in the knowledge base seriously hamper discussion of the resource problem. Following a mercury-centered explanation of the problems of estimates, resource limits and of calculation of figures for different categories of resources and reserves, the article attempts to clarify the roles that theoretical and empirical knowledge have in structuring the options within the resource system. 相似文献
50.
Exotic species have been observed to be more prevalent in sites where the richness of native species is highest, possibly reflecting variation among sites in resources, propagule supply, heterogeneity, or disturbance. However, such a pattern leaves unclear whether natives at species-rich sites are subject to especially severe impacts from exotics as a result. We considered this question using path models in which relationships between exotic cover and native richness were evaluated in the presence of correlated environmental factors. At 109 sites on serpentine soils across California, USA, exotic cover was positively correlated with total native herbaceous richness and was negatively correlated with the richness of both serpentine-endemic and rare native herbs. However, in path models that accounted for the influences of soil chemistry, disturbance, overstory cover, and regional rainfall and elevation, we found no indication that exotic cover reduced any component of native herb richness. Rather, our results indicated similarities and differences in the conditions favoring exotic, native, endemic, and rare species. Our results suggest that, in spite of some localized impacts, exotic species are not exerting a detectable overall effect on the community richness of the unique native flora of Californian serpentine. 相似文献