全文获取类型
收费全文 | 454篇 |
免费 | 12篇 |
国内免费 | 14篇 |
专业分类
安全科学 | 9篇 |
废物处理 | 5篇 |
环保管理 | 91篇 |
综合类 | 113篇 |
基础理论 | 129篇 |
环境理论 | 2篇 |
污染及防治 | 80篇 |
评价与监测 | 28篇 |
社会与环境 | 19篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 9篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 18篇 |
2015年 | 22篇 |
2014年 | 20篇 |
2013年 | 29篇 |
2012年 | 22篇 |
2011年 | 28篇 |
2010年 | 26篇 |
2009年 | 19篇 |
2008年 | 38篇 |
2007年 | 31篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有480条查询结果,搜索用时 46 毫秒
221.
222.
Daniel P. Cartamil Chugey A. Sepulveda Nicholas C. Wegner Scott A. Aalbers Andres Baquero Jeffrey B. Graham 《Marine Biology》2011,158(4):935-944
The common thresher shark (Alopias vulpinus) is a secondary target species of the California drift gillnet fishery (CA-DGN) and supports a growing recreational fishery
in California waters. This study used archival tags to examine the movement patterns and habitat preferences of common threshers
of the size range captured in the CA-DGN (>120 cm fork length). Depth and temperature-logging archival tags were deployed
on 57 subadult and adult common threshers in the Southern California Bight. Tags from five individuals (8.8%) were recovered,
and 154 days of data were successfully obtained from four of these. By night, shark movements were primarily limited to waters
above the thermocline, which ranged in depth from 15 to 20 m. Sharks were significantly deeper by day, and daytime vertical
distribution consisted of two distinct modes: a ‘shallow mode’ (wherein sharks occupied only the upper 20 m of the water column)
and a ‘deep mode’ (characterized by frequent vertical excursions below the thermocline). This modal switch is interpreted
as relating to regional differences in abundance of surface-oriented prey and prey in deeper water. Maximum dive depth was
320 m, greatest dive duration was 712 min, minimum temperature experienced during a dive was 9.1°C, and dive descent rate
was significantly greater than ascent rate. Sharks inhabited waters corresponding to a sea surface temperature range of 16
to 21°C. The nocturnal depth distribution of common threshers has implications for management of drift gillnet deployment
depths in the CA-DGN. 相似文献
223.
224.
The need to recover and recycle valuable resources from Waste Electrical and Electronic Equipment (WEEE) is of growing importance as increasing amounts are generated due to shorter product life cycles, market expansions, new product developments and, higher consumption and production rates. The European Commission (EC) directive, 2002/96/EC, on WEEE became law in UK in January 2007 setting targets to recover up to 80% of all WEEE generated.Printed Wire Board (PWB) and/or Printed Circuit Board (PCB) is an important component of WEEE with an ever increasing tonnage being generated. However, the lack of an accurate estimate for PCB production, future supply and uncertain demands of its recycled materials in international markets has provided the motivation to explore different approaches to recycle PCBs.The work contained in this paper focuses on a novel, dry separation methodology in which vertical vibration is used to separate the metallic and non-metallic fractions of PCBs. When PCBs were comminuted to less than 1 mm in size, metallic grades as high as 95% (measured by heavy liquid analysis) could be achieved in the recovered products. 相似文献
225.
Changing contaminant mobility in a dredged canal sediment during a three-year phytoremediation trial
King RF Royle A Putwain PD Dickinson NM 《Environmental pollution (Barking, Essex : 1987)》2006,143(2):318-326
Metal mobility and degradation of organic pollutants were investigated in a contaminated canal sediment in NW England. Sediment was dredged and exposed above the water surface, planted with multiple taxa of Salix, Populus and Alnus and monitored over 32 months. Short-term metal fractionation and phytotoxicity during sediment oxidation were also evaluated in separate laboratory studies. Zinc and Pb redistributed into more mobile fractions, which increased toxicity of the sediment to plants in the laboratory. In contrast, at the canal site, mobility of most elements decreased and total concentrations of Zn, Pb, Cu and Cd fell. Petroleum hydrocarbon concentrations decreased, but the tree-planted treatments appeared less effective at reducing PAH concentrations than treatments colonised by invasive plants. Tree survivorship decreased over time, suggesting increasing phytotoxicity of the exposed sediment in the longer term. Trees provided little benefit in terms of sediment remediation. Options for future management of the sediment are evaluated. 相似文献
226.
Development projects that impact wetlands commonly require compensatory mitigation, usually through creation or restoration
of wetlands on or off the project site. Over the last decade, federal support has increased for third-party off-site mitigation
methods. At the same time, regulators have lowered the minimum impact size that triggers the requirement for compensatory
mitigation. Few studies have examined the aggregate impact of individual wetland mitigation projects. No previous study has
compared the choice of mitigation method by regulatory agency or development size. We analyze 1058 locally and federally permitted
wetland mitigation transactions in the Chicago region between 1993 and 2004. We show that decreasing mitigation thresholds
have had striking effects on the methods and spatial distribution of wetland mitigation. In particular, the observed increase
in mitigation bank use is driven largely by the needs of the smallest impacts. Conversely, throughout the time period studied,
large developments have rarely used mitigation banking, and have been relatively unaffected by changing regulatory focus and
banking industry growth. We surmise that small developments lack the scale economies necessary for feasible permittee responsible
mitigation. Finally, we compare the rates at which compensation required by both county and federal regulators is performed
across major watershed boundaries. We show that local regulations prohibiting cross-county mitigation lead to higher levels
of cross- watershed mitigation than federal regulations without cross-county prohibitions. Our data suggest that local control
over wetland mitigation may prioritize administrative boundaries over hydrologic function in the matter of selecting compensation
sites. 相似文献
227.
Predicting the Vulnerability of Tropical Reef Fishes to Exploitation with Phylogenies and Life Histories 总被引:9,自引:0,他引:9
Simon Jennings ‡ John D. Reynolds and Nicholas V. C. Polunin† 《Conservation biology》1999,13(6):1466-1475
Abstract: Fishing has led to local extirpations of reef fishes. For conservation and management purposes, it is important to identify all those species that are vulnerable to fishing, but this cannot be done using a priori assessments or by describing trends in abundance because the necessary scientific resources are not available. Thus the predictions of vulnerability that provide the basis for conservation action will have to be made with existing data or data that can be acquired rapidly before further extirpations occur. The life histories of species may determine their responses to exploitation, and we describe how an easily measured parameter, maximum observed size, is related to population trends of exploited fishes on coral reefs. Using a phylogenetic comparative approach, we demonstrated that species of grouper (Epinephelinae), snapper (Lutjanidae), and parrotfish (Scaridae) that decreased in abundance more than their nearest phylogenetic relative had greater maximum size. Our results suggest that one can predict the vulnerability of reef fishes to exploitation based on responses of their relatives. The quality of the prediction was good for the intensively fished groupers and snappers but poor for the lightly fished parrotfishes. Our approach may help proactive conservationists and fishery managers identify and conserve vulnerable species in new, developing, or lightly exploited fisheries, thereby reducing their reliance on reactive management methods. 相似文献
228.
229.
230.
Twin–twin transfusion syndrome (TTTS) is attributed to trans-anastomotic transfusion between twins. Anastomoses are ubiquitous in monochorionic (MC) placentae, yet TTTS develops in only 15%. Although ex vivo and in vivo studies fail to identify a unique anastomotic signature, TTTS placentae are typically associated with an imbalance in unidirectional arteriovenous anastomoses with absent bidirectional anastomoses. Doppler detection of an artery-artery anastomosis reduces the chance of TTTS, whereas, in those that develop the disease, it improves stage-independent survival. Selective laser is often curative, but an increasingly recognized risk of persistent or reverse TTTS may be attributable to atypical arteriovenous anastomoses not identifiable from the chorionic plate. Simple dysvolaemia fails to explain several phenotypic features, including haematological concordancy, recipient hypertension, and reversibly absent end diastolic flow in the donor. The renin-angiotensin system is upregulated in the donor and downregulated in the recipient's kidneys, while paradoxically raised renin levels in the recipient may contribute to raised afterload along with endothelin. Although research is limited in humans by therapy and the lack of a suitable experimental model, further studies of placental and vascular pathophysiology may not only refine current treatment modalities but may also, in addition, suggest further avenues for downstream management such as genetic predisposition testing or pharmacological intervention. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献