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431.
H. Florou 《Chemistry and Ecology》1996,12(4):253-258
This study deals with 137Cs dispersion and behaviour in the Aegean and Ionian Sea based on work done during the period 1984-1994, as a brief general review. Sea water, sediment and marine biota were analysed and measured by gamma spectrometry and the activity concentrations of 137Cs were evaluated with consideration to the sources of pollution. According to 137Cs levels the period is distinguished into three sub-periods, the pre-Chernobyl, the early Chernobyl influence and the late Chernobyl influence period. During the early period of the Chernobyl accident the 137Cs levels in the Greek marine environment increased roughly up to an order of magnitude if compared with the pre-accident ones. Since 1988, the late impact of the accident is focused mainly in the North Aegean Sea, at the Dardanelles mouth, due to the Black Sea outflow. 相似文献
432.
The effects of nitrate additions on the physics, chemistry and biology of lake water were studied in 5 × 10 m polyethylene enclosures installed in Lake Kastoria, a shallow eutrophic lake in Northern Greece. The water physics, chemistry, chlorophyll a and nitrogenase activity were monitored from July 10 till October 17 1985 at 2 week intervals. The experiment included a control enclosure.
Water confinement in the control enclosure resulted in ammonia accumulation, a slight decrease in chlorophyll a, a significant reduction of nitrogenase activity and an increase in phosphorus release from the sediments at the end of the experimental period.
The addition of KNO3 resulted in higher than the control accumulation of NH3, chlorophyll reduction, increase in water transparency and reduction of nitrogenase activity. Large losses of nitrogen added were measured which were attributed to denitrification, organic matter sedimentation and ammonia volatilization. Anaerobic but not aerobic phosphorus release from sediments was inhibited at the end of the period. The reduction of nitrogenase activity and of chlorophyll a concentration are attributed to changes in phytoplankton composition from blue-greens to small-sized species grazed by zooplankters. 相似文献
Water confinement in the control enclosure resulted in ammonia accumulation, a slight decrease in chlorophyll a, a significant reduction of nitrogenase activity and an increase in phosphorus release from the sediments at the end of the experimental period.
The addition of KNO3 resulted in higher than the control accumulation of NH3, chlorophyll reduction, increase in water transparency and reduction of nitrogenase activity. Large losses of nitrogen added were measured which were attributed to denitrification, organic matter sedimentation and ammonia volatilization. Anaerobic but not aerobic phosphorus release from sediments was inhibited at the end of the period. The reduction of nitrogenase activity and of chlorophyll a concentration are attributed to changes in phytoplankton composition from blue-greens to small-sized species grazed by zooplankters. 相似文献
433.
434.
In June 1990, sediment cores were obtained from several locations in the Northwest Black Sea shelf and slope by a joint US/USSR scientific team aboard the survey vessel R/V VODYANITSKY. the goal of this investigation was to determine the distribution and levels of radioactivity resulting from the Chernobyl 1986 nuclear accident. the sediment was characterized for texture, mineral composition, redox state, heavy metals, and radionuclides. Correlations emerging from these data reveal paths of dispersal and transport of materials from river sources to deposition sites on the shelf and slope. Kaolinite in the clay mineral suite clearly reflects a dispersal pattern originating in the Danube River and progressing in an easterly direction across the shelf. Sand-size gypsum and the elemental heavy metals Zn, Cu, Cr, and Pb (probable industrial source) as well as the elements Al and Mg (probable terrigenous source) also show a dispersal pattern from the Danube station location in an easterly direction across the shelf. the dispersal direction indicated by these materials is not in conflict with recent existing notions concerning the hydrology of the Northwest Black Sea. Barium anomalies at a midshelf location may be related to operations in the Lebada oil fields situated updrift. Heavy mineral dispersal reflect the Danube and -Crimean Provinces established for the shelf and relate to terrestrial source areas. in addition, the heavy mineral monazite correlates with the radioactive Th 232 found most abundantly in the Crimean Province. Local anomalies of Mn, Fe and U in the sediment at station locations are related to redox (Eh) conditions and other factors. Cs134/137 data, reported by Curtis and Broadway (1991), correspond to transport and dispersal patterns implicit in the mineralogic, anthropogenic indicators, and sediment characteristics of the study area. 相似文献
435.
Sources and Distribution of Polychlorinated Terphenyls at a Major US Aeronautics Research Facility 总被引:1,自引:0,他引:1
O -deethylase (EROD) activity to a similar degree as PCB Aroclor 1254 and to a greater extent than PCT Aroclor 5460. The presence
of high concentrations of PCTs contributed to the facility being included on the National Priorities List. It subsequently
became the first US federal facility to sign a Federal Facility Agreement, identifying cleanup responsibilities, prior to
formal listing. 相似文献
436.
BackgroundcontentsofheavymetalsinsedimentsoftheYangtzeRiversystemandtheircalculationmethodsZhangChaosheng,ZhangShen,ZhangLich... 相似文献
437.
针对城市雨水管网沉积物中抗生素抗性基因(ARGs)污染特性尚不清楚的问题,本研究选择南京江北新区3种不同功能区(文教区、交通区及商业区)分流制雨水管网沉积物作为研究对象,考察了各功能区雨水管网沉积物中细菌耐药性,分析了β-内酰胺类和四环素类两类典型ARGs的组成种类及其相对丰度差异,重点探讨了上述典型ARGs在不同粒径颗粒中的分布特征.结果表明,各功能区可培养细菌总数大小顺序为商业区 > 文教区 > 交通区,而携带典型ARGs的耐药菌(ARB)相对含量大小顺序却为文教区 > 商业区 > 交通区;交通区的典型ARGs相对丰度高于文教区和商业区1个数量级;随着干期长度的增加,各功能区雨水管网沉积物中典型ARGs种类及相对丰度均有不同程度的减少;随着颗粒粒径的减小,文教区雨水管道沉积物中典型ARGs的丰度变化不大,交通区的雨水管道沉积物中典型ARGs的丰度则呈增加趋势,而商业区的无明显规律;粒径较小的颗粒中可移动遗传因子(MGEs)对ARGs的分布影响更大,且以<75 μm粒径段颗粒中的最明显(相关系数为0.874). 相似文献
438.
439.
440.
Hydrocarbon and elemental carbon signatures in a tropical wetland: biogeochemical evidence of forest fire and vegetation changes 总被引:2,自引:0,他引:2
Evidence of changing vegetation in the tropical wetland (Rawa Danau, west Java, Indonesia) over the past 7428 years is illustrated by elemental (soot) carbon (EC) and n-alkane composition of sedimentary geolipids. In this study, vegetation changes and relevant controlling factors (e.g. forest fire and climate change) were documented on a decadal to centennial scale. The n-alkane composition that changes with depth might record changes in sources of organic matter (OM) in the wetland. The presence of EC (0.01–0.24% of organic carbon: OC) during late (0–1700 cal. year BP) and mid (3500–4500 cal. year BP) Holocene (at depths 0–50 cm, and 160–210 cm) indicated that large-scale forest fires severely affected the tropical vegetation. The hydrocarbon indices (CPI: carbon preference index, MCN: mean carbon number, and HVI: hydrocarbon vegetation index) significantly correlated with one another while a comparison of EC profile with the profiles of hydrocarbon indices indicated that n-alkane composition of the geolipid in lake sediment could record signatures of changes in catchment vegetation. Forest fire and vegetation changes might be related to regional climatic shifts relating to ENSO activity as well as being influenced by human influences. 相似文献