全文获取类型
收费全文 | 2850篇 |
免费 | 388篇 |
国内免费 | 1009篇 |
专业分类
安全科学 | 314篇 |
废物处理 | 124篇 |
环保管理 | 272篇 |
综合类 | 1994篇 |
基础理论 | 432篇 |
环境理论 | 1篇 |
污染及防治 | 535篇 |
评价与监测 | 200篇 |
社会与环境 | 214篇 |
灾害及防治 | 161篇 |
出版年
2024年 | 11篇 |
2023年 | 70篇 |
2022年 | 173篇 |
2021年 | 192篇 |
2020年 | 206篇 |
2019年 | 124篇 |
2018年 | 151篇 |
2017年 | 171篇 |
2016年 | 135篇 |
2015年 | 174篇 |
2014年 | 249篇 |
2013年 | 277篇 |
2012年 | 254篇 |
2011年 | 237篇 |
2010年 | 201篇 |
2009年 | 191篇 |
2008年 | 210篇 |
2007年 | 188篇 |
2006年 | 152篇 |
2005年 | 126篇 |
2004年 | 115篇 |
2003年 | 114篇 |
2002年 | 100篇 |
2001年 | 67篇 |
2000年 | 97篇 |
1999年 | 61篇 |
1998年 | 37篇 |
1997年 | 37篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 24篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有4247条查询结果,搜索用时 46 毫秒
971.
Mengmeng Zheng Hua Zheng Yingxia Wu Yi Xiao Yihua Du Weihua Xu Fei Lu Xiaoke Wang Zhiyun Ouyang 《环境科学学报(英文版)》2015,28(2):195-202
The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output,surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields.Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010,partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk,decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields. 相似文献
972.
该研究以探索不同菌群对黄姜废渣厌氧消化产沼气的性质为目的,分别以酵母废水活性污泥和实验室驯化的秸秆分解产甲烷菌群为产沼气菌源进行发酵,通过监测厌氧发酵过程中的甲烷生产效率、纤维素酶活性等指标,评价黄姜废渣厌氧发酵产甲烷的能力,同时考察纤维素分解菌群WDC2的加入对黄姜废渣产沼气的影响。该研究对有效处理黄姜皂素生产废渣、促进区域环境安全具有重要意义。结果表明:黄姜废渣在产甲烷菌群的作用下均能生成大量沼气,最高日产气量为可达到2 701 m L/d,最大产气效率为855 m L/g。酵母废水活性污泥产气效率明显优于秸秆分解产甲烷菌群。加入WDC2菌群能显著提高厌氧消化的前期纤维素酶活力,最高酶活分别为达到1.22 U/m L和9.42 U/m L,但WDC2的加入并没有对发酵体系的产甲烷效率产生明显的促进作用。 相似文献
973.
根据加油站实际工况,模拟埋地油罐人孔井内发生汽油泄漏时,挥发的油气在人孔井内积聚并遇到点火源发生爆炸的事故.埋地油罐内布置压力传感器,实验人孔井内布置压力传感器,人孔井周围布置热流传感器,以获得事故对埋地油罐、人孔井口人员及设备的影响数据.实验结果表明:爆炸在人孔井内产生的压力冲击波和热辐射冲击,会对人孔井口的人员造成严重伤害,但对埋地油罐罐内不会造成影响.油气闪爆后,人孔井盖可能处于关闭或打开两种状态,使得人孔井内火焰熄灭或形成稳定燃烧,燃烧限制于人孔井,对埋地油罐和周围设施影响较小. 相似文献
974.
975.
Development of EMC-based empirical model for estimating spatial distribution of pollutant loads and its application in rural areas of Korea 总被引:1,自引:0,他引:1
An integrated approach to easily calculate pollutant loads from agricultural watersheds is suggested and verified in this research. The basic concepts of this empirical tool were based on the assumption that variations in event mean concentrations (EMCs) of pollutants from a given agricultural watershed during rainstorms were only attributable to the rainfall pattern. Fifty one sets of EMC values were obtained from nine different watersheds located in the rural areas of Korea, and these data were used to develop predictive tools for the EMCs in rainfall runoff. The results of statistical tests of these formulas show that they are fairly good in predicting actual EMC values of some parameters, and useful in terms of calculating pollutant loads for any rainfall event time span such as daily, weekly, monthly, and yearly. This model was further checked in for its field applicability in a reservoir receiving stormwater after a cleanup of the sediments, covering 17 consecutive rainfall events from 1 July to 15 August in 2007. Overall the predicted values matched the observed values, indicating the feasibility of this empirical tool as a simple and useful solution in evaluating timely distribution of nonpoint source pollution loads from small rural watersheds of Korea. 相似文献
976.
Yinghui Han Xiaolei Li Maohong Fan Armistead G. Russell Yi Zhao Chunmei Cao Ning Zhang Genshan Jiang 《环境科学学报(英文版)》2015,27(4):55-64
A novel ferruginous active absorbent, prepared by fly ash, industrial lime and the additive Fe(VI), was introduced for synchronous abatement of binary mixtures of SO2–NOx from simulated coal-fired flue gas. The synergistic action of various factors on the absorption of SO2 and NOx was investigated. The results show that a strong synergistic effect exists between Fe(VI) dose and reaction temperature for the desulfurization. It was observed that in the denitration process, the synergy of Fe(VI) dose and Ca/(S + N) had the most significant impact on the removal of NO, followed by the synergy of Fe(VI) and reaction temperature, and then the synergy of reaction temperature and flue gas humidity. A scanning electron microscope(SEM) and an accessory X-ray energy spectrometer(EDS)were used to observe the surface characteristics of the raw and spent absorbent as well as fly ash. A reaction mechanism was proposed based on chemical analysis of sulfur and nitrogen species concentrations in the spent absorbent. The Gibbs free energy, equilibrium constants and partial pressures of the SO2–NOx binary system were determined by thermodynamics. 相似文献
977.
Feasibility of bioleaching combined with Fenton oxidation to improve sewage sludge dewaterability 总被引:1,自引:0,他引:1
A novel joint method of bioleaching with Fenton oxidation was applied to condition sewage sludge. The specific resistance to filtration (SRF) and moisture of sludge cake (MSC) were adopted to evaluate the improvement of sludge dewaterability. After 2-day bioleaching, the sludge pH dropped to about 2.5 which satisfied the acidic condition for Fenton oxidation. Meanwhile, the SRF declined from 6.45 × 1010 to 2.07 × 1010 s2/g, and MSC decreased from 91.42% to 87.66%. The bioleached sludge was further conditionedwith Fenton oxidation. From an economical point of view, the optimal dosages of H2O2 and Fe2+ were 0.12 and 0.036 mol/L, respectively, and the optimal reaction time was 60 min. Under optimal conditions, SRF, volatile solids reduction, and MSC were 3.43 × 108 s2/g, 36.93%, and 79.58%, respectively. The stability and settleability of sewage sludge were both improved significantly. Besides, the results indicated that bioleaching-Fenton oxidation was more efficient in dewatering the sewage sludge than traditional Fenton oxidation. The sludge conditioningmechanisms by bioleaching-Fenton oxidationmight mainly include the flocculation effects and the releases of extracellular polymeric substances-bound water and intercellular water. 相似文献
978.
979.
MnxCe1- xO2(x: 0.3–0.9) prepared by Pechini method was used as a catalyst for the thermal catalytic oxidation of formaldehyde(HCHO). At x = 0.3 and 0.5, most of the manganese was incorporated in the fluorite structure of Ce O2 to form a solid solution. The catalytic activity was best at x = 0.5, at which the temperature of 100% removal rate is the lowest(270°C). The temperature for 100% removal of HCHO oxidation is reduced by approximately 40°C by loading 5 wt.% Cu Oxinto Mn0.5Ce0.5O2. With ozone catalytic oxidation, HCHO(61 ppm) in gas stream was completely oxidized by adding 506 ppm O3 over Mn0.5Ce0.5O2 catalyst with a GHSV(gas hourly space velocity) of 10,000 hr-1at 25°C. The effect of the molar ratio of O3 to HCHO was also investigated. As O3/HCHO ratio was increased from 3 to 8, the removal efficiency of HCHO was increased from 83.3% to 100%. With O3/HCHO ratio of 8, the mineralization efficiency of HCHO to CO2 was 86.1%. At 25°C, the p-type oxide semiconductor(Mn0.5Ce0.5O2) exhibited an excellent ozone decomposition efficiency of 99.2%,which significantly exceeded that of n-type oxide semiconductors such as Ti O2, which had a low ozone decomposition efficiency(9.81%). At a GHSV of 10,000 hr-1, [O3]/[HCHO] = 3 and temperature of 25°C, a high HCHO removal efficiency(≥ 81.2%) was maintained throughout the durability test of 80 hr, indicating the long-term stability of the catalyst for HCHO removal. 相似文献
980.
Linlin Xing Yongbing Xie Daisuke Minakat Hongbin Cao Jiadong Xiao Yi Zhang John C. Crittenden 《环境科学学报(英文版)》2014,26(10):2095-2105
Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon(AC)in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals(HOU) in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol(tBA) with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate. 相似文献