全文获取类型
收费全文 | 2193篇 |
免费 | 255篇 |
国内免费 | 1649篇 |
专业分类
安全科学 | 172篇 |
废物处理 | 100篇 |
环保管理 | 236篇 |
综合类 | 2449篇 |
基础理论 | 345篇 |
环境理论 | 1篇 |
污染及防治 | 741篇 |
评价与监测 | 34篇 |
社会与环境 | 17篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 5篇 |
2023年 | 30篇 |
2022年 | 80篇 |
2021年 | 131篇 |
2020年 | 123篇 |
2019年 | 140篇 |
2018年 | 120篇 |
2017年 | 100篇 |
2016年 | 152篇 |
2015年 | 194篇 |
2014年 | 229篇 |
2013年 | 263篇 |
2012年 | 282篇 |
2011年 | 270篇 |
2010年 | 207篇 |
2009年 | 273篇 |
2008年 | 158篇 |
2007年 | 280篇 |
2006年 | 242篇 |
2005年 | 167篇 |
2004年 | 114篇 |
2003年 | 136篇 |
2002年 | 75篇 |
2001年 | 63篇 |
2000年 | 62篇 |
1999年 | 53篇 |
1998年 | 26篇 |
1997年 | 33篇 |
1996年 | 22篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有4097条查询结果,搜索用时 62 毫秒
301.
本文介绍了关于洗涤剂中磷对环境影响的两种典型观点和解决的办法,并从经济和环境的角度进行全面的分析,得出合理的结论和建议。 相似文献
302.
Pollution in the marine protected area of North Sporades Islands was investigated in July 1997. Salinity, temperature, dissolved oxygen, dissolved inorganic nutrients, organic carbon, hydrocarbons as well as dissolved and particulate trace metals were determined at 15 offshore and coastal stations. Dissolved organic carbon and inorganic nutrient concentrations indicate the mesotrophic character of the investigated waters. The dissolved forms of nitrogen were slightly higher at coastal stations. Dissolved and particulate Cu, Zn and Ni, were higher in coastal stations, whereas concentrations of Pb were generally low and likely of atmospheric origin. Dissolved/Dispersed petroleum hydrocarbons (DDPH) were close to detection limits at all stations. Temperature and salinity vertical profiles, nutrient and trace metal concentrations revealed the presence of a slight influence of the Black Sea water coming from Dardanelles straits. 相似文献
303.
Monitoring of eutrophication and nutrient limitation in the Izmir Bay (Turkey) before and after Wastewater Treatment Plant 总被引:3,自引:0,他引:3
The distribution of inorganic nutrients and phytoplankton chlorophyll-a was investigated and N/P ratios were determined in Izmir Bay during 1996-2001. The average concentrations showed ranges of 0.01-0.19 and 0.01-10 microM for phosphate-phosphorus; 0.11-1.8 and 0.13-27 microM for (nitrate+nitrite)-nitrogen, 0.30-4.1 and 0.50-39 microM for silicate and 0.02-4.3 and 0.10-26 microg l(-1) for chlorophyll-a in the outer and middle-inner bays, respectively. The results are compared with the values obtained from the relatively unpolluted waters of the Aegean Sea. The N/P ratio is significantly lower than the assimilatory optimal (N/P=15:1) in conformity with Redfield's ratio N/P=16:1. Nitrogen is the limiting element in the Izmir Bay. Phosphate, which originates from detergents, is an important source for eutrophication in the bay, especially in the inner bay. In early 2000, a Wastewater Treatment Plant (WTP) began to treat domestic and industrial wastes. This plant treats the wastes about 60% capacity between 2000 and 2001. The sampling periods cover before and after treatment plant. Although the capacity of wastewater plant is sufficient for removal of nitrogen from the wastes, it is inadequate for removal of phosphate. This is also in accordance with the decreasing N/P ratios observed during 2000-2001 (after WTP) in the middle-inner bays. 相似文献
304.
305.
306.
Various approaches have been used to classify large geographical areas into smaller regions of similar water quality or extrapolate
water-quality data from a few streams to other unmonitored streams. A combination of some of the strengths of existing techniques
is used to develop a new approach for these purposes. In this new approach, referred to here as SPARTA (SPAtial Regression-Tree
Analysis), environmental characteristics for each monitored stream are first quantified using a Geographic Information System
(GIS) and then regression-tree analysis is used to determine which characteristics are most statistically important in describing
the distribution of a specific water-quality constituent. GIS coverages of only the most statistically significant environmental
characteristics are then used to subdivide the area of interest into relatively homogeneous environmental water-quality zones.
Results from the regression-tree analysis not only define the most important environmental characteristics, but also describe
how to subdivide the coverage of the specific characteristic (for example, areas with <26% or ≥26% soil clay content). The
resulting regionalization scheme is customized for each water-quality constituent based on the environmental characteristics
most statistically related to that constituent. SPARTA was used to delineate areas of similar phosphorus, nitrogen, and sediment
concentrations (by including land-use characteristics) and areas of similar potential water quality (by excluding land-use
characteristics). The SPARTA approach reduced the variability in water-quality concentrations (phosphorus, total nitrogen,
Kjeldahl nitrogen, and suspended sediment) within similarly classified zones from that obtained using the US Environmental
Protection Agency's nutrient ecoregions. 相似文献
307.
EMMC process for combined removal of organics, nitrogen and an odor producing substance 总被引:2,自引:0,他引:2
In order to improve the process performance regarding the removal of organics, nitrogen, and an odor-causing compound (sulfide) contained in domestic wastewater, an entrapped-mixed-microbial cell (EMMC) with and without humic substances for both fixed and moving carrier reactors and conventional suspended growth culture (i.e. conventional activated sludge process) were investigated simultaneously. Both synthetic (simulated to the organics concentration of general domestic sewage) and actual domestic wastewater were investigated under operational conditions of 12 h of hydraulic retention time (HRT) with 1 h of aeration and 1 h of non-aeration, and 6 h of HRT with continuous aeration, at a room temperature of 25 +/- 2 degrees C. It was found that entrapping humic substances in the EMMC carriers had no impact on the removal of organics, nitrogen, and the odor-producing compound. Additionally, the performance of the EMMC moving carrier system for the removal of these pollutants is similar to that of the EMMC fixed carrier system. In general, the EMMC associated systems which provide high solids retention time achieve a better removal of chemical oxygen demand (COD), nitrogen, and the odor-producing substance than the suspended growth system for both HRTs of 6 h (continuous aeration) and 12 h (1 h of aeration and 1 h of non-aeration). Both the fixed and moving carrier EMMC processes, therefore, have the potential for improvement or replacement of the existing conventional activated sludge process with regard to improving the effluent qualities (such as COD, nitrogen and odor-producing compound) for reuse/disposal. 相似文献
308.
Methodological Development of an Index of Coastal Water Quality: Application in a Tourist Area 总被引:2,自引:0,他引:2
With the aim of obtaining an index of coastal water quality, a methodological procedure based on numerical classification and discriminant analysis is presented. The procedure was applied to nutrient data (ammonia, nitrite, nitrate, and phosphate) analyzed along the coastal waters of a Spanish tourist area. Using numerical classification, three levels of nutrient loading were revealed, characterizing oligotrophic, mesotrophic, and potentially eutrophic waters. Discriminant analysis was shown to be an effective methodological tool in the discrimination between trophic groups. For every group, the discriminant procedure generated the centroids. The centroids representing oligotrophic and potentially eutrophic conditions were used to establish the two extremes of the continuum of mesotrophic conditions in these coastal waters: Standardizing values from -1 to 1, the centroids for oligotrophic and potentially eutrophic waters yielded an interval that defined the range of mesotrophic conditions. This interval is proposed as a water quality index. The ability of the coastal water quality index to successfully predict mesotrophic conditions was proved with random samples. 相似文献
309.
310.
Saber A. El-Shafai Fatma A. El-Gohary Fayza A. Naser P. van der Steen Huub J. Gijzen 《The Environmentalist》2007,27(2):287-302
An integrated system, consisting of Up-flow Anaerobic Sludge Blanket (UASB)-duckweed-tilapia ponds was used for recovery of
sewage nutrients and water recycling. A UASB reactor with 40 liter working volume was used as pre-treatment unit followed
by a series of three duckweed ponds for nitrogen recovery. The treated effluent and duckweed biomass was used to feed fishponds
stocked with Nile tilapia (Oreochromis niloticus). The UASB reactor was fed with raw, domestic sewage at 6 h hydraulic retention time. The three duckweed ponds were stocked
with Lemna gibba and fed with UASB effluent at 15 days hydraulic retention time. Nitrogen recovery from UASB effluent via duckweed biomass
represented 81% of total nitrogen removal and 46.5% from the total nitrogen input to the system. In subsequent fishponds the
nitrogen recovery from duckweed as fish feed was in the range of 13.4–20%. This nitrogen in fish biomass represented 10.6–11.5
g N from the total nitrogen in the raw sewage fed to the UASB reactor. The growth performance of tilapia (Oreochromis niloticus) showed specific growth rates (SGR) in the range of 0.53–0.97. The range of feed conversion ratio (FCR) and protein efficiency
ratio (PER) were 1.2–2.2 and 2.1–2.28, respectively. The results of the experiments showed total fish yield and net fish yield
in the range of 17–22.8 ton/ha/y and 11.8–15.7 ton/ha/y respectively. In conclusion UASB-duckweed-tilapia ponds provide marketable
by-products in the form of duckweed and fish protein, which represent a cost recovery for sewage treatment. 相似文献