全文获取类型
收费全文 | 2798篇 |
免费 | 261篇 |
国内免费 | 140篇 |
专业分类
安全科学 | 264篇 |
废物处理 | 6篇 |
环保管理 | 121篇 |
综合类 | 748篇 |
基础理论 | 279篇 |
环境理论 | 2篇 |
污染及防治 | 33篇 |
评价与监测 | 35篇 |
社会与环境 | 109篇 |
灾害及防治 | 1602篇 |
出版年
2024年 | 13篇 |
2023年 | 42篇 |
2022年 | 63篇 |
2021年 | 92篇 |
2020年 | 62篇 |
2019年 | 86篇 |
2018年 | 57篇 |
2017年 | 78篇 |
2016年 | 70篇 |
2015年 | 93篇 |
2014年 | 74篇 |
2013年 | 132篇 |
2012年 | 194篇 |
2011年 | 173篇 |
2010年 | 130篇 |
2009年 | 139篇 |
2008年 | 86篇 |
2007年 | 166篇 |
2006年 | 170篇 |
2005年 | 142篇 |
2004年 | 109篇 |
2003年 | 88篇 |
2002年 | 123篇 |
2001年 | 119篇 |
2000年 | 109篇 |
1999年 | 72篇 |
1998年 | 88篇 |
1997年 | 83篇 |
1996年 | 75篇 |
1995年 | 77篇 |
1994年 | 56篇 |
1993年 | 52篇 |
1992年 | 43篇 |
1991年 | 20篇 |
1990年 | 8篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1983年 | 3篇 |
1982年 | 5篇 |
排序方式: 共有3199条查询结果,搜索用时 0 毫秒
71.
Robert A. Pikanowski 《Chemistry and Ecology》2013,29(1-4):199-212
Disposal of sewage sludge in the New York Bight Apex (12-Mile Dump Site) ceased at the end of December 1987. Previous efforts to quantify the effects of sludge were hindered by the inability to obtain true replication. the cessation of dumping afforded the opportunity to apply the technique of replication in time, also known as a Before/After, Control/Impact design. Conditionally, this method allows one to separate treatment effects from the natural differences that confound many environmental impact studies. the Environmental Processes Division of the Northeast Fisheries Center, National Marine Fisheries Service sampled the benthic environment of the New York Bight Apex from June 1986 through September 1989 using a sample design based on the technique of replication in time. Three dominant species (rock crab, Cancer irroratus; little skate; Raja erinacea; and winter flounder, Pseudopleuronectes americanus) and total demersal finfish, collected by otter trawl, showed no statistically significant response to the cessation of disposal. American lobster (Homarus americanus) increased in local abundance, but this result was possibly confounded by a change in fishing effort. 相似文献
72.
The National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends (NS&T) Programme has analyzed samples of surface sediment collected at almost 300 coastal and estuarine sites throughout the United States since 1984. the overall distributions for concentrations of each element are approximately lognormal allowing a definition of geometric means and of “high” concentrations as those exceeding the mean plus one standard deviation of the lognormal distribution. Those mean and “high” concentrations should be useful for comparing the NS&T data set and with other reports on sediment contamination. A world-wide data set, constructed from data in the literature, was summarized in an identical manner. It was found, after excluding locally extreme values, that the NS&T and world-wide data sets yielded very similar mean and “high” concentrations for Cu, Ni, Pb and Zn. Chromium was the sole element showing higher summary statistics in the NS&T data set, a result attributed to NS&T sampling in areas of naturally (not contaminated) elevated Cr content. It remains undetermined, however, why the world-wide data set, even with exclusion of “hot spots”, yielded higher means and “highs” for Cd, Hg, As, and Ag. 相似文献
73.
JULIO A. BAISRE 《Conservation biology》2013,27(5):927-935
The recent extnction of the Caribbean monk seal Monachus tropicalis has been considered an example of a human‐caused extinction in the marine environment, and this species was considered a driver of the changes that have occurred in the structure of Caribbean coral reef ecosystems since colonial times. I searched archaeological records, historical data, and geographic names (used as a proxy of the presence of seals) and evaluated the use and quality of these data to conclude that since prehistoric times the Caribbean monk seal was always rare and vulnerable to human predation. This finding supports the hypothesis that in AD 1500, the Caribbean monk seal persisted as a small fragmented population in which individuals were confined to small keys, banks, or isolated islands in the Gulf of Mexico and the Caribbean Sea. This hypothesis is contrary to the assumption that the species was widespread and abundant historically. The theory that the main driver of monk seal extinction was harvesting for its oil for use in the sugar cane industry of Jamaica during the 18th century is based primarily on anecdotal information and is overemphasized in the literature. An analysis of reported human encounters with this species indicates monk seal harvest was an occasional activity, rather than an ongoing enterprise. Nevertheless, given the rarity of this species and its restricted distribution, even small levels of hunting or specimen collecting must have contributed to its extinction, which was confirmed in the mid‐20th century. Some sources had been overlooked or only partially reviewed, others misinterpreted, and a considerable amount of anecdotal information had been uncritically used. Critical examination of archaeological and historical records is required to infer accurate estimations of the historical abundance of a species. In reconstructing the past to address the shifting baseline syndrome, it is important to avoid selecting evidence to confirm modern prejudices. Puntos de Referencia Cambiantes y la Extinción de la Foca Monje Caribeña 相似文献
74.
ABSTRACTThe impacts of extreme weather events, causing severe storms and wildfires, cascade across administrative borders within a country, challenging the steering capacity of governance networks at different political scales. This paper examines how accountability and risk were constructed and negotiated in the aftermath of Sweden’s largest wildfire. It draws on results from an interview study with executives of organizations and landowners involved, and an analysis of government reports about the wildfire’s cause and consequences. Although the fire was human-caused, public administrative bodies paid considerable attention to the local emergency services and their poor handling of the wildfire, caused by lack of knowledge of forest fire behavior. The study confirms many of the challenges associated with governance networks. It finds that issues about who to hold accountable, in what forum and for what issue are not fully addressed, being overwhelmed by demands for better knowledge of forest fire prevention and improved coordination and collaboration. To conclude, the paper calls for a better-informed public administration, forest sector and interrelated networks that take responsibility for their actions or lack thereof. 相似文献
75.
Biodegradation of N,N-bis(carboxymethyl)-L-glutamate and its utilization by micro-organisms in marine environments were studied in Organization of Economic Development and Cooperation (OECD) screening tests and with pure bacterial cultures. Biodegradation in excess of 60% was achieved in closed bottle tests in less than 60 days, suggesting complete degradation. The bacterial strain isolated from marine sandy sediment and utilizing N,N-bis(carboxymethyl)-L-glutamate as sole source of carbon, nitrogen, and energy was identified as Rhizobium radiobacter. The strain was capable to mineralize N,N-bis(carboxymethyl)-L-glutamate in seawater and in synthetic media containing 0–60 g L?1 sea salts. Growth and adaptation studies indicated that N-carboxymethyl-L-glutamate and L-glutamate are main metabolites. 相似文献
76.
77.
应用浮游植物群落结构指数评价海域富营养化 总被引:30,自引:0,他引:30
探讨了浮游植物对海水富营养化程度的指示作用,并用浮游植物群落结构指数对天津近岸海域的富营养化水平进行了现状评价,结果表明,天津近岸海域水质基本属中营养水平,但某些站位在有些季节呈严重的富营养水平,并呈现枯水期和丰水期高,平水期低的特征,与化学指标的评价结果相比,结果基本一致,说明该方法是可行的,特别是当浮游植物大量繁殖,消耗了大量的营养盐,生物学指标更能正确合理地进行水质评价 相似文献
78.
79.
微塑料一般指直径小于5 mm的微小型塑料颗粒或碎片,海洋中常见的微塑料类型主要包括聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯等。由于形状、颜色多变,分子量大,结构稳定,粒径范围与浮游植物相近,海洋中的微塑料很容易对浮游植物、浮游动物和其他海洋动物等产生影响。微塑料还可以为病毒、细菌提供附着载体,影响浮游植物分布,进入海洋生物消化道或进一步转移到组织中对机体产生毒性效应,甚至通过捕食作用沿食物链传递,对高等动物及人类健康造成威胁。此外,微塑料可以作为海水中痕量化学物质的吸附载体,对生物产生联合毒性。根据目前对微塑料的研究进展情况,未来应加强对海洋微塑料分离、鉴定技术的研发以及海洋微塑料的生物毒性效应和生物传递效应机制等问题的研究。 相似文献
80.
Ranjan Kumar Mohapatra Pankaj Kumar Parhi Hrudayanath Thatoi 《Chemistry and Ecology》2017,33(2):114-130
Hexavalent chromium-tolerant (1500?mg/L) bacterium MW1 was isolated from harbour water of Paradip Port and evaluated for Cr(VI) reduction potential. The isolate was identified as Exiguobacterium indicum by biochemical and 16S rRNA gene sequence methods. Salt tolerance of the bacterium was evaluated in a wide range of NaCl concentrations (0.5–13%, w/v). The Cr(VI) reduction of the strain was evaluated and optimised with varied Cr(VI) concentrations (100–1000?mg/L), pH (5.0–9.0), temperature (30–40°C) and shaking velocity (100–150?rpm) in two different minimal media (M9 and Acetate). Under optimised conditions, after 192?h of incubation nearly 92%, 50% and 46% reduction in the M9 minimal medium and 91%, 47% and 40% reduction in the acetate minimal medium were observed for 100, 500 and 1000?mg/L of Cr(VI), respectively. The exponential rate equation for Cr(VI) reduction yielded higher rate constant value, that is, 1.27?×?10?2?h?1 (M9) and 1.17?×?10?2?h?1 (Acetate) in case of 100?mg/L and became lower for 500 and 1000?mg/L Cr(VI) concentrations. Further, the association of bacterial cells with reduced product was ascertained by Fourier transform infrared spectrometer, UV–Vis–DRS and field-emission scanning electron microscope–energy-dispersive X-ray analyses. The above study suggests that the higher reducing ability of the marine bacterium E. indicum MW1 will be suitable for Cr(VI) reduction from saline effluents. 相似文献