全文获取类型
收费全文 | 3295篇 |
免费 | 95篇 |
国内免费 | 197篇 |
专业分类
安全科学 | 160篇 |
废物处理 | 17篇 |
环保管理 | 789篇 |
综合类 | 1346篇 |
基础理论 | 216篇 |
污染及防治 | 271篇 |
评价与监测 | 593篇 |
社会与环境 | 150篇 |
灾害及防治 | 45篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 46篇 |
2021年 | 69篇 |
2020年 | 95篇 |
2019年 | 48篇 |
2018年 | 51篇 |
2017年 | 90篇 |
2016年 | 109篇 |
2015年 | 124篇 |
2014年 | 149篇 |
2013年 | 163篇 |
2012年 | 134篇 |
2011年 | 256篇 |
2010年 | 93篇 |
2009年 | 237篇 |
2008年 | 203篇 |
2007年 | 207篇 |
2006年 | 158篇 |
2005年 | 136篇 |
2004年 | 134篇 |
2003年 | 125篇 |
2002年 | 105篇 |
2001年 | 94篇 |
2000年 | 91篇 |
1999年 | 90篇 |
1998年 | 85篇 |
1997年 | 63篇 |
1996年 | 47篇 |
1995年 | 56篇 |
1994年 | 67篇 |
1993年 | 40篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1973年 | 5篇 |
1969年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有3587条查询结果,搜索用时 171 毫秒
131.
L. Jeffrey Lefkoff Donald R. Kendall 《Journal of the American Water Resources Association》1996,32(3):451-463
ABSTRACT: A non-linear optimization model is applied to the California State Water Project (SWP) and portions of the Central Valley Project (CVP). The model accounts for the major hydrologic, regulatory, and operational features of both projects. The model maximizes long-term SWP yields over a 70-year period, using a quarterly time step. The potential for increased yield associated with a proposed facility improvement is evaluated with the model. The proposed facility is an extension of the Folsom-South Canal, which would allow water to be conveyed from the American River below Folsom Reservoir into New Melones Reservoir on the Stanislaus River or into the California Aqueduct. Model results indicate that extension of the Folsom-South Canal has the potential to increase SWP yields by 13 percent. 相似文献
132.
本文根据常微分方程参数反问题的数学理论,将正交化方法同有限差分法结合用于确定水质模型参数,并与正则化方法、最速下降法和共轭梯度法作了比较。其计算结果对比表明,正交化方法具有快速、简便、可靠的特点。更适合于水质模型参数的确定。 相似文献
133.
Characteristics of large cooking oil pool fires and their extinguishment by water mist 总被引:1,自引:0,他引:1
Z. Liu D. Carpenter A.K. Kim 《Journal of Loss Prevention in the Process Industries》2006,19(6):516-526
Large cooking oil pool fires, occurring in industrial oil cookers, present a severe hazard to food processing plants due to their size and the large amount of hot oil involved. This paper reports a series of full-scale fire experiments conducted in a large industrial oil cooker mock-up. The characteristics of large cooking oil pool fires and the effect of oil depth and hood position in the oil cooker on fire growth were studied. The use of water mist for extinguishing large oil pool fires and their extinguishing performance under different discharge pressure and with different types of water mist systems were investigated. Experimental results showed that the cooking oil underwent a substantial expansion in volume during heating. The fires developed quickly once the oil auto-ignited. The fire growth rate was affected by the oil depth in the pan and the hood position in the oil cooker. The water mist fire suppression systems effectively extinguished large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker. 相似文献
134.
135.
The Water Fluxes of the Yellow River to the Sea in the Past 50 Years, in Response to Climate Change and Human Activities 总被引:12,自引:1,他引:12
Jiongxin X 《Environmental management》2005,35(5):620-631
Since the 1970s, the water fluxes to the sea of the Yellow River have declined significantly. Based on data of precipitation, air temperature, the measured and “natural” river flow, the water diversion and consumption, and the areas of erosion and sediment control measures over the drainage basin, water fluxes to the sea of the Yellow River are studied in relation with the influences of changing climate and human activities. The Yellow River basin can be divided into different water source areas; multiple regression indicates that the variation in precipitation over different water source areas has different effect on water fluxes to the sea. In the period between 1970 and 1997, averaged air temperature over the whole Yellow River increased by about 1.0°C, from 16.5°C to 17.5°C, a factor that is negatively correlated with the water yield of the Yellow River. Water diversion and consumption has sharply increased and resulted in a significant decline in the water fluxes to the sea. Since the 1960s, erosion and sediment control measures have been practiced over the drainage basin. This factor, to a lesser degree, is also responsible for the decrease in water fluxes to the sea. A multiple regression equation has been established to estimate the change in water fluxes to the sea caused by the changes in precipitation, air temperature, water diversion and consumption, erosion, and sediment control measures, indicating that the contribution of water diversion and consumption to the variation in annual water flux to the sea is 41.3%, that of precipitation is 40.8%, that of temperature is 11.4%, and that of erosion and sediment control measures is 6.5%. 相似文献
136.
A multi-objective optimisation approach to water management 总被引:3,自引:0,他引:3
The management of river basins is complex especially when decisions about environmental flows are considered in addition to those concerning urban and agricultural water demand. The solution to these complex decision problems requires the use of mathematical techniques that are formulated to take into account conflicting objectives. Many optimization models exist for water management systems but there is a knowledge gap in linking bio-economic objectives with the optimum use of all water resources under conflicting demands. The efficient operation and management of a network of nodes comprising storages, canals, river reaches and irrigation districts under environmental flow constraints is challenging. Minimization of risks associated with agricultural production requires accounting for uncertainty involved with climate, environmental policy and markets. Markets and economic criteria determine what crops farmers would like to grow with subsequent effect on water resources and the environment. Due to conflicts between multiple goal requirements and the competing water demands of different sectors, a multi-criteria decision-making (MCDM) framework was developed to analyze production targets under physical, biological, economic and environmental constraints. This approach is described by analyzing the conflicts that may arise between profitability, variable costs of production and pumping of groundwater for a hypothetical irrigation area. 相似文献
137.
《Journal of Environmental Economics and Management》2014,67(3):639-655
By signing a water sharing agreement (WSA), countries agree to release an amount of river water in exchange for a negotiated compensation. We examine the vulnerability of such agreements to reduced water flows. Among all WSAs that are acceptable to riparian countries, we find out the one which is self-enforced under the most severe drought scenarios. The so-called upstream incremental WSA assigns to each country its marginal contribution to its followers in the river. Its mirror image, the downstream incremental WSA, is not sustainable to reduced flow at the source. Self-enforcement problems can be solved by setting water releases and compensations contingent to water flow. We apply our analysis to the Aral Sea Basin. We compute the upstream incremental compensations for the Bishkek agreement and asses its vulnerability with historical flows. 相似文献
138.
Xueqi Fan Jie Gao Wenchao Li Jun Huang Gang Yu 《Frontiers of Environmental Science & Engineering》2020,14(1):8
139.
Heijo Scharff 《Waste management (New York, N.Y.)》2014,34(11):2218-2224
Modern waste legislation aims at resource efficiency and landfill reduction. This paper analyses more than 20 years of landfill reduction in the Netherlands. The combination of landfill regulations, landfill tax and landfill bans resulted in the desired landfill reduction, but also had negative effects. A fierce competition developed over the remaining waste to be landfilled. In 2013 the Dutch landfill industry generated €40 million of annual revenue, had €58 million annual costs and therefore incurred an annual loss of €18 million. It is not an attractive option to prematurely end business. There is a risk that Dutch landfill operators will not be able to fulfil the financial obligations for closure and aftercare. Contrary to the polluter pays principle the burden may end up with society. EU regulations prohibiting export of waste for disposal are in place. Strong differentials in landfill tax rate between nations have nevertheless resulted in transboundary shipment of waste and in non-compliance with the self-sufficiency and proximity principles. During the transformation from a disposal society to a recycling society, it is important to carefully plan required capacity and to guide the reorganisation of the landfill sector. At some point, it is no longer profitable to provide landfill services. It may be necessary for public organisations or the state to take responsibility for the continued operation of a ‘safety net’ in waste management. Regulations have created a financial incentive to pass on the burden of monitoring and controlling the impact of waste to future generations. To prevent this, it is necessary to revise regulations on aftercare and create incentives to actively stabilise landfills. 相似文献
140.
N. Said T. Bishara A. García-Maraver M. Zamorano 《Waste management (New York, N.Y.)》2013,33(11):2250-2256
Rice straw can be used as a renewable fuel for heat and power generation. It is a viable mean of replacing fossil fuels and preventing pollution caused by open burning, especially in the areas where this residual biomass is generated. Nevertheless, the thermal conversion of rice straw can cause some operating problems such as slag formation, which negatively affects thermal conversion systems. So, the main objective of this research is studying the combustion behavior of rice straw samples collected from various regions by applying thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In addition, the thermal behavior of ashes from rice straw was also analyzed in order to detect their melting points, and ash sintering was detected at different temperatures within the range between 550 and 1000 °C. Since washing rice straw with water could reduce the content of undesirable inorganic compounds related to the ash fusibility, samples of washed rice straw were analyzed under combustion conditions to investigate its differences regarding the thermal behavior of rice straw. The results showed that rice straw washing led to a significant improvement in its thermal behavior, since it reduced the ash contents and sintering formation. 相似文献