全文获取类型
收费全文 | 20778篇 |
免费 | 4535篇 |
国内免费 | 369篇 |
专业分类
安全科学 | 3217篇 |
废物处理 | 323篇 |
环保管理 | 3208篇 |
综合类 | 11742篇 |
基础理论 | 2113篇 |
环境理论 | 9篇 |
污染及防治 | 1715篇 |
评价与监测 | 996篇 |
社会与环境 | 1311篇 |
灾害及防治 | 1048篇 |
出版年
2025年 | 205篇 |
2024年 | 585篇 |
2023年 | 710篇 |
2022年 | 839篇 |
2021年 | 984篇 |
2020年 | 934篇 |
2019年 | 795篇 |
2018年 | 643篇 |
2017年 | 878篇 |
2016年 | 929篇 |
2015年 | 911篇 |
2014年 | 945篇 |
2013年 | 1136篇 |
2012年 | 1314篇 |
2011年 | 1425篇 |
2010年 | 973篇 |
2009年 | 1056篇 |
2008年 | 822篇 |
2007年 | 1230篇 |
2006年 | 1218篇 |
2005年 | 1061篇 |
2004年 | 920篇 |
2003年 | 873篇 |
2002年 | 755篇 |
2001年 | 627篇 |
2000年 | 565篇 |
1999年 | 541篇 |
1998年 | 366篇 |
1997年 | 298篇 |
1996年 | 204篇 |
1995年 | 191篇 |
1994年 | 164篇 |
1993年 | 154篇 |
1992年 | 99篇 |
1991年 | 59篇 |
1990年 | 42篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1973年 | 8篇 |
1972年 | 7篇 |
1971年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Salmon aquaculture has emerged as a successful economic industry generating high economic revenues to invest in the development of Chiloe region, Southern Chile. However, salmon aquaculture also consumes a substantial amount of ecosystem services, and the direct and indirect impacts on human wellbeing are still unknown and unexplored. This paper identifies the synergies and trade-offs caused by the salmon industry on a range of ecosystem services. The results show that large economic benefits due to the increase of provisioning ecosystem services are also causing a reduction on regulating and cultural services. Despite the improvement on average income and poverty levels experienced in communities closely associated with the sector, this progress is not large enough and social welfare did not improve substantially over the last decade. The rest of human wellbeing constituents in Chiloe region have not changed significantly compared to the development in the rest of the country. 相似文献
32.
The bromination of five selected pharmaceuticals (metoprolol, naproxen, amoxicillin, phenacetin, and hydrochlorothiazide) was studied with these compounds individually dissolved in ultra-pure water. The apparent rate constants for the bromination reaction were determined as a function of the pH, obtaining the sequence amoxicillin > naproxen ? hydrochlorothiazide ≈ phenacetin ≈ metoprolol. A kinetic mechanism specifying the dissociation reactions and the species formed for each compound according to its pKa value and the pH allowed the intrinsic rate constants to be determined for each elementary reaction. There was fairly good agreement between the experimental and calculated values of the apparent rate constants, confirming the goodness of the proposed reaction mechanism.In a second stage, the bromination of the selected pharmaceuticals simultaneously dissolved in three water matrices (a groundwater, a surface water from a public reservoir, and a secondary effluent from a WWTP) was investigated. The pharmaceutical elimination trend agreed with the previously determined rate constants. The influence of the main operating conditions (pH, initial bromine dose, and characteristics of the water matrix) on the degradation of the pharmaceuticals was established. An elimination concentration profile for each pharmaceutical in the water matrices was proposed based on the use of the previously evaluated apparent rate constants, and the theoretical results agreed satisfactorily with experiment. Finally, chlorination experiments performed in the presence of bromide showed that low bromide concentrations slightly accelerate the oxidation of the selected pharmaceuticals during chlorine disinfection. 相似文献
33.
Mobility of Cd and Cu in formulated sediments coated with iron hydroxides and/or humic acids: a DGT and DGT-PROFS modeling approach 总被引:1,自引:0,他引:1
The diffusive gradients technique in thin films (DGT) was used to investigate the kinetic resupply of Cd and Cu to pore water from the solid phase. For the sake of simplification, experiments were performed using formulated sediments that differed in the presence or absence of humic acids (HA) and/or of iron hydroxides (i.e., goethite and ferrihydrite). The effects of the time after the contamination of the solid phase (aging effect) on formulated sediments that were coated with goethite and HA and spiked with Cd were also evaluated. Kinetic DGT results were interpreted using the newly developed, multi-compartmental model DGT-PROFS.Due to Cu humate formation, the addition of HA slightly increased the Cu concentration in the pore water independent of the effect of the iron hydroxide coating on the formulated sediments and slightly decreased that of Cd. The impact of 8-190 d of aging resulted in a significant decrease in the Cd concentration of the pore water over an increasing incubation time.Modeling our results with DGT-PROFS led to the following conclusions concerning the impact of HA and iron hydroxides on Cd and Cu availability. First, in the presence of HA and absence of iron hydroxides, Cd is associated mainly with weak sites, while Cu is bound to strong sites. Similarly, in the presence of both iron hydroxides and HA, Cu appeared to be more heavily associated with the strong sites than did Cd. When the incubation time increased from 8 to 190 d, a proportion of Cd initially adsorbed onto weak sites transferred to the strong sites, suggesting that the adsorption of Cd on sediments is controlled partially by slow kinetic processes. 相似文献
34.
结合环境监测实验实质量控制数据处理的实际要求,用计算机高级语言,设计开发成功了《精密度-偏性分析质控试验数据处理系统》,该系统具有数据输入,查询,修改,统计分析和打印报告等功能,在实际应用中,取得良好效果。 相似文献
35.
Rolf Groeneveld Lex Bouwman Sonja Kruitwagen Ekko van Ierland 《Environmental Modeling and Assessment》2001,6(2):101-109
Nitrate leaching forms an important environmental problem because it causes pollution of groundwater and surface water, and adds to already problematic eutrophication. This study analyses the impact of reductions in nitrate leaching on land cover decisions of dairy farms, of which the activities make an important contribution to nitrate leaching. As the level of nitrate leaching depends on groundwater depth as well as on the supply of nitrogen, spatial variation in groundwater levels will cause a spatial variation in land cover under restrictions on nitrate leaching. A non-linear partial optimisation model for the economic and ecological aspects of the problem were used to show how land cover and dairy farms' financial balances change when nitrate losses are reduced. The model is spatially explicit, and describes nitrate leakage and yields of maize and grass as a function of groundwater depth, including the effects of various grazing systems. The model analyses the decisions of a risk neutral agent who minimises costs under the following constraints: (i) production, feed requirements and mass balances for fodder; (ii) constraints for nitrate leaching. Economic costs are attributed to increased costs of fodder and processing of manure when nitrate restrictions are tightened. An important result of the study is the variation in compliance costs and land cover for maize and grass production brought about by spatial variation in groundwater depth. While the effects are negligible for some shallow groundwater classes, it is extremely difficult in other classes – if not impossible – to obtain the EU standard of maximum admissible losses of 34 kg N ha–1 at low costs. The study shows an important reduction in land cover by maize. 相似文献
36.
In this study, the relation between sulfur dioxide (SO2) and particulate matter (PM) concentrations periodically measured in the city of Afyon’s atmosphere with meteorological factors
such as precipitation, humidity, temperature, wind velocity, and inversion were investigated. The mean values of SO2 and PM concentrations measured during the winter months of October–March 1990–1999 were correlated with the meteorological
parameters of the same period. Simple and multiple linear regression analysis were utilized to evaluate the contribution of
meteorological variables. The statistical results show that the pollutants, i.e., SO2 and PM are dependent upon humidity, temperature, and inversion at the 1% significance level; while the dependence of both
pollutants with temperature is negative when those of humidity and inversion are positive. Two models in which temperature
and inversion are dependent with multiple variables are recommended for predicting the contribution of meteorological parameters
on SO2 and PM. In addition, the relationship between humidity, temperature, and inversion with pollutants is also determined using
nonlinear (polynomial) models. 相似文献
37.
A Global Model Tracking Water, Nitrogen, and Land Inputs and Virtual Transfers from Industrialized Meat Production and Trade 总被引:1,自引:0,他引:1
Marshall Burke Kirsten Oleson Ellen McCullough Joanne Gaskell 《Environmental Modeling and Assessment》2009,14(2):179-193
Rising populations and incomes throughout the world have boosted meat demand by over 75% in the last 20years, intensifying
pressures on production systems and the natural resources to which they are linked. As a growing proportion of global meat
production is traded, the environmental impacts of production become increasingly separated from where the meat is consumed.
In this paper, we quantify the use of three important resources associated with industrial livestock production and trade—water,
land, and nitrogen—using a country-specific model that combines trade, agronomic, biogeochemical, and hydrological data. Our
model focuses on pigs and chickens, as these animals are raised predominantly in intensive systems using concentrated, compound
feeds. The results describe the geographical patterns of environmental resource use due to meat production, trade, and consumption.
We show that US feed, animal, and meat destined for export require almost as much nitrogen and land, and 20% more water, than
products destined for domestic consumption. Model results also demonstrate that among various production factors, improvements
in crop yields and animal feed conversion efficiencies result in the most significant reductions in environmental harm. By
explicitly tracking the externalities of meat production, we hope to bolster suppliers’ accountability and provide better
information to meat consumers.
相似文献
Kirsten OlesonEmail: |
38.
通过监测和田地区生态修复项目实施后所取得生态效益的结果表明,生态修复项目实施后,由于项目区风速降低,温度和相对湿度的变化减少,提高了植被盖度,降低了风蚀量,促进了成土作用的进行,从而逐渐改善了土壤的理化性质。 相似文献
39.
城市污水排江工程模型试验的研究 总被引:1,自引:0,他引:1
对城市污水排江问题进行了模拟试验,通过对水力模型不同试验工况中改变喷嘴个数、射流速度、射流角度和上升管间距条件下的试验结果分析,结合武汉市污水排江工程问题,确定了黄浦路、平湖门尾水排放中的近区多喷口形式的最佳工程参数,实践证明效果良好。 相似文献
40.