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151.
于桥水库富营养化防治前置库对策可行性研究 总被引:12,自引:0,他引:12
于桥水库库前区墙截老河道入口,形成一个近9km ̄2,容积达2000万m ̄3~2500万m ̄3的前置库,可充分发挥其物理、生物、化学的综合作用,延长入流水在前置库区的滞留时间,降低流速,均化流场使入流水在前置库区得到净化,大量的泥沙及营养盐截留在前置库区,从而使进入主库的营养盐含量大幅度降低,抑制主库中藻类的过度繁殖,起到防治或减缓于桥水库富营养化的作用。 相似文献
152.
卞有生 《生态与农村环境学报》1995,(1)
采用典型定点法调查农户庭院经济系统,并对其进行能流和经济效益分析。结果表明,菜-鸡-猪-沼气结构的庭院经济系统能获得较好的效益。 相似文献
153.
1999年10月12日零点零二分,地球上的第60亿位居民,一个3.6公斤重的男婴在波黑首都萨拉热窝的一个医院降生,在我们为他祝贺的同时,是否也应想一想60亿人吃什么?烧什么?喝什么? 相似文献
154.
The aim of this study was to evaluate the effect of chronic formaldehyde (FA) exposure on the hippocampus in the chronic cerebral hypoperfusion rat model. Seventy-two male Sprague-Dawley rats were randomly divided into four groups: (A) sham-operated bilateral common carotid artery occlusion (BCCAO) with room air inhalation, (B) BCCAO with room air inhalation, (C) sham-operated BCCAO with FA inhalation at a concentration of 10?mL?vapor?m?3, 1?h per day for 90 days, and (D) BCCAO with FA inhalation. Decreased mobility, injected conjunctivae, and overreaction were observed in groups C and D rats after 30 days of FA exposure. The level of malondialdehyde (MDA) increased significantly in group D at 90 days after FA exposure. The expression of Bax protein increased, while Bcl-2 and NR2B proteins decreased significantly in group D compared to group B or C. Neuronal nuclear antigen (NeuN) positive cells decreased significantly in group D. Neuronal loss, oxidative stress, and the expression of proteins were more prominent at 90 days after FA exposure, especially in group D. Oxidative stress-induced neuronal damages in the hippocampus may be a possible mechanism of neurotoxicity as a result of chronic FA exposure. Chronic exposure of FA caused more neuronal damage in the chronic cerebral hypoperfusion rat model. 相似文献
155.
156.
In China, endemic arseniasis attributable to the geological-geochemistry environment is mainly found in the plain of the Great Bend of the Yellow River and the Hu-Bao plain in the Inner Mongolia Autonomous Region, in the Datong basin of Shanxi Province, the floodplain of the northern side of the Tian Mountain of Xinjiang Uygur Autonomous Region, and in the southwest coastal plain of Taiwan. These areas share many similar characteristics including widespread occurrences, a large population being affected, and the magnitude of risk involved. The population living in these areas is estimated to be around 5.5 × 105, of which of 2.5 × 105 are resident in Inner Mongolia. Based on our systematic research and comparison of various areas, we found the different types of arseniasis are often associated with different regions. The neural arseniasis is distributed in Xinjiang Uygur Autonomous Region and Shanxi Province, caused by inorganic arsenic in drinking water while the cycling-obstacle arseniasis is mainly found in Inner Mongolia and Taiwan, associated with organic arsenic in water. The distribution of arsenic affected villages in Inner Mongolia exhibits orientation and focus on low-lying land in the subsiding centre of the Great Bend basin, which was enriched with humus in the lake and limnetic deposits. Much CH4 gas can be detected in the water of shallow and deep wells in these villages. Some of the wells with higher concentrations of CH4 can even be ignited. This is a typical reductive geochemical environment. We tested the total amount of arsenic (As), As3+, and methyl arsenate in all types of water sources. It is found that the number of arseniasis cases is not clearly related to the total amount of arsenic (As) in the water. However, it is related to the ratio of As3+ plus methyl arsenic to the total amount of arsenic (As). The higher the ratio, the higher the number of people affected and the more serious the illness. The statistical results also indicate that good drinking water accounts for 60% of the drinking water source while the arsenic contaminated water makes up about 25% of the drinking water in the study area. This research reveals that the local geochemical environment is responsible for the spreading of the endemic arseniasis in the area and thus suggests a new direction of how to prevent such disease. 相似文献
157.
158.
卞有生 《生态与农村环境学报》1999,(1)
以北京市留民营农业生态工程为例,从系统中能量流动分析出发,阐述了能量摄取效率、同化效率、生长效率和利用效率的概念和计算方法,指出通过生态效率计算,指导系统调控,对于提高生产效益的重要作用。 相似文献
159.
Liyun Song Shilin Deng Chunyi Bian Cui Liu Zongcheng Zhan Shuangye Li Jian Li Xing Fan Hong He 《Frontiers of Environmental Science & Engineering》2023,17(8):96
160.
S.A. Edgerton X. Bian J.C. Doran J.D. Fast J.M. Hubbe E.L. Malone 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1221-1229
ABSTRACT PM10, PM25, precursor gas, and upper-air meteorological measurements were taken in Mexico City, Mexico, from February 23 to March 22, 1997, to understand concentrations and chemical compositions of the city's particulate matter (PM). Average 24-hr PM10 concentrations over the period of study at the core sites in the city were 75 H g/m3. The 24-hr standard of 150 μ g/m3 was exceeded for seven samples taken during the study period; the maximum 24-hr concentration measured was 542 μ g/m3. Nearly half of the PM10 was composed of fugitive dust from roadways, construction, and bare land. About 50% of the PM10 consisted of PM2.5, with higher percentages during the morning hours. Organic and black carbon constituted up to half of the PM2.5. PM concentrations were highest during the early morning and after sunset, when the mixed layers were shallow. Meteorological measurements taken during the field campaign show that on most days air was transported out of the Mexico City basin during the afternoon with little day-to-day carryover. 相似文献