全文获取类型
收费全文 | 37749篇 |
免费 | 446篇 |
国内免费 | 560篇 |
专业分类
安全科学 | 1144篇 |
废物处理 | 1676篇 |
环保管理 | 4792篇 |
综合类 | 6429篇 |
基础理论 | 9600篇 |
环境理论 | 16篇 |
污染及防治 | 9988篇 |
评价与监测 | 2546篇 |
社会与环境 | 2327篇 |
灾害及防治 | 237篇 |
出版年
2023年 | 180篇 |
2022年 | 376篇 |
2021年 | 366篇 |
2020年 | 316篇 |
2019年 | 330篇 |
2018年 | 628篇 |
2017年 | 611篇 |
2016年 | 935篇 |
2015年 | 696篇 |
2014年 | 998篇 |
2013年 | 3033篇 |
2012年 | 1262篇 |
2011年 | 1737篇 |
2010年 | 1441篇 |
2009年 | 1466篇 |
2008年 | 1708篇 |
2007年 | 1803篇 |
2006年 | 1565篇 |
2005年 | 1305篇 |
2004年 | 1268篇 |
2003年 | 1221篇 |
2002年 | 1186篇 |
2001年 | 1441篇 |
2000年 | 1067篇 |
1999年 | 683篇 |
1998年 | 477篇 |
1997年 | 463篇 |
1996年 | 508篇 |
1995年 | 517篇 |
1994年 | 466篇 |
1993年 | 431篇 |
1992年 | 416篇 |
1991年 | 394篇 |
1990年 | 390篇 |
1989年 | 389篇 |
1988年 | 336篇 |
1987年 | 287篇 |
1986年 | 275篇 |
1985年 | 282篇 |
1984年 | 354篇 |
1983年 | 294篇 |
1982年 | 360篇 |
1981年 | 292篇 |
1980年 | 247篇 |
1979年 | 292篇 |
1978年 | 219篇 |
1977年 | 213篇 |
1976年 | 190篇 |
1975年 | 179篇 |
1974年 | 182篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Adsorption of Pb, Cd to Fe, Mn oxides in natural freshwater surface coatings developed in different seasons 总被引:4,自引:0,他引:4
Metal oxides( Fe, Mn oxides) in natural surface coatings(biofilms and associated minerals) are believed to play a significant role n the fate and transport of trace metal in aquatic environments. Seasonal variation of Fe, Mn oxides and organic materials in surface oatings, which were developed periodically on glass slides in Nanhu Lake, Jilin Province, China over the time frame of three seasons,was investigated in order to understand the influence of metal oxides on Pb and Cd adsorption to heterogeneous surface coating materials(biofilm). Pb and Cd adsorption was measured under controlled laboratory conditions( mineral salts solution with defined speciation, ionic trength 0.05 mol/L, 25~C and pH 6.0). The classical Langmuir adsorption isotherm was applied to estimate equilibrium coefficients of Pb nd Cd adsorption to the surface coatings. In general, components in the surface coatings varied greatly with seasons altering and btained higher concentrations in summer while the content of iron oxides always exceeded that of manganese oxides. Correlation nalyses between the maximum adsorption of Pb and Cd and components in the surface coatings developed periodically indicated that Pb hase association with Mn oxides and Cd phase association with Fe oxides as well as Mn oxides were statistically significant. Effect of Mn xides on Cd adsorption was confirmed in view of its higher content in the surface coatings. The importance of ferromanganese oxides for b and Cd adsorption to the natural surface coatings developed in different seasons was evidenced. 相似文献
952.
不同种类有机肥施用对稻田CH4和N2O排放的综合影响 总被引:22,自引:4,他引:22
以麦茬稻田为对象,研究基肥施用不同有机肥对稻田CH4和N2O排放的综合影响.结果表明:有机肥施用对稻田CH4和N2O排放的季节变化模式无明显影响,但影响其排放量.与施用化肥(化肥处理)相比,施用菜饼+化肥(菜饼处理)促进CH4和N2O的排放,其季节排放总量分别增加了252%和22%;施用小麦秸秆+化肥(秸秆处理)和牛厩肥+化肥(牛厩肥处理)明显增加CH4排放,增加量分别为250%和45%,同时却减少N2O排放,分别减少18%和21%;施用猪厩肥+化肥(猪厩肥处理)降低CH4和N2O的排放,分别降低4%和18%.对CH4和N2O排放的综合温室效应分析表明,菜饼和秸秆处理的全球增温潜势(GWP)约为化肥处理的2.5倍,牛厩肥和化肥处理基本持平,但施用猪厩肥可减少10%~15%.各处理的GWP从高到低依次为菜饼、秸秆、牛厩肥、化肥和猪厩肥.单位产量的GWP以秸秆处理最高,菜饼次之,牛厩肥比化肥处理略高,猪厩肥处理最低.从本生长季来看,猪厩肥的施用对于实现环境效益与生产效益的协调发展具有一定作用. 相似文献
953.
对1980-2007年广东沿海赤潮灾害历史资料进行统计分析,研究赤潮灾害的时空分布规律和赤潮肇事种的变化规律.结果表明,广东沿海赤潮灾害总体呈上升趋势,发生频率不断增加;赤潮高发季节由过去的春季扩展到春夏秋冬季;赤潮发生海域和影响范围不断扩大;鱼毒性藻类和有毒藻越来越频繁地引发赤潮;引发赤潮灾害的生物种类不断增多,由甲藻和硅藻引发的赤潮减少,而由针胞藻类、定鞭藻类和纤毛虫类引发的赤潮明显增多.研究表明,赤潮生物种类繁多和日益增多的海洋污染可能是广东沿海赤潮灾害频发的原因. 相似文献
954.
955.
956.
J. Sun Y. P. Li X. W. Zhuang S.W. Jin G. H. Huang R. F. Feng 《Mitigation and Adaptation Strategies for Global Change》2018,23(4):553-578
In this study, an integrated simulation-based allocation modeling system (ISAMS) is developed for identifying water resources management strategies in response to climate change. The ISAMS incorporates global climate models (GCMs), a semi-distributed land use-based runoff process (SLURP) model, and a multistage interval-stochastic programming (MISP) approach within a general framework. The ISAMS can not only handle uncertainties expressed as probability distributions and interval values but also reveal climate change impacts on water resources allocation under different projections of GCMs. The ISAMS is then applied to the Kaidu-kongque watershed with cold arid characteristics in the Tarim River Basin (the largest inland watershed basin in China) for demonstrating its efficiency. Results reveal that different climate change models corresponding to various projections (e.g., precipitation and temperature) would lead to changed water resources allocation patterns. Variations in water availability and demand due to uncertainties could result in different water allocation targets and shortages. A variety of decision alternatives about water allocations adaptive to climate change are generated under combinations of different global climate models and ecological water release plans. These findings indicate that understanding the uncertainties in water resources system, building adaptive methods for generating sustainable water allocation patterns, and taking actions for mitigating water shortage problems are key adaptation strategies responding to climate change. 相似文献
957.
采用高效菌提高普通活性污泥系统抗2,4-DCP负荷冲击能力 总被引:4,自引:3,他引:4
研究了用于处理生活污水的普通活性污泥反应器(CAS)受到2,4-二氯酚(2,4-DCP)间歇性负荷冲击时,投加高效菌的生物强化系统和对照系统对污染物的响应及系统稳定性,并考察了长期运行过程中强化系统对目标污染物去除能力的变化.结果表明,投加5%和15% 2,4-DCP复合高效菌的强化CAS系统,其对目标污染物的降解能力及抗负荷冲击能力得到显著提高.当系统受到间歇性2,4-DCP负荷冲击[110.37~171.60 mg/(L·d)]时,对于单次投菌后前30日内发生的间歇性负荷冲击,强化系统有效保持了对目标污染物的强化效果;在无2,4-DCP存在的情况下连续运行70d,当系统再次受到2,4-DCP负荷冲击时,强化系统的强化效果与前几次相比已明显下降,不能够快速有效去除污染物并维持系统稳定,因此有必要再次投加高效菌. 相似文献
958.
Over the past few years, antibiotics have been considered emerging pollutants due to their continuous input and persistence in the aquatic ecosystem even at low concentrations. They have been detected worldwide in environmental matrices, indicating their ineffective removal from water and wastewater using conventional treatment methods. To prevent this contamination, several processes to degrade/remove antibiotics have been studied. This review addresses the current state of knowledge concerning the input sources, occurrence and mainly the degradation and removal processes applied to a specific class of micropollutants, the antibiotics. In this paper, different remediation techniques were evaluated and compared, such as conventional techniques (biological processes, filtration, coagulation, flocculation and sedimentation), advanced oxidation processes (AOPs), adsorption, membrane processes and combined methods. In this study, it was found that ozonation, Fenton/photo-Fenton and semiconductor photocatalysis were the most tested methodologies. Combined processes seem to be the best solution for the treatment of effluents containing antibiotics, especially those using renewable energy and by-products materials. 相似文献
959.
960.
Terrace-contouring systems with on-site water detention cannot be installed in areas of complex topography, small parceling and multi-blade moldboard plow use. However, field borders at the downslope end may be raised at the deepest part where runoff overtops to create detention ponds, which can be drained by subsurface tile outlets and act similar to terrace-contouring systems. Four of such detention ponds were monitored over 8 years. Monitored effects included the prevention of linear erosion down slope, the sediment trapping from upslope, the enrichment of major nutrients in the trapped and delivered sediments, the amount of runoff retained temporarily, the amount of runoff reduced by infiltration, the decrease in peak runoff rate and the decrease in peak concentrations of agrochemicals due to the mixing of different volumes of water within the detention ponds. The detention ponds had a volume of 30–260 m3 ha−1 and trapped 54–85% of the incoming sediment, which was insignificantly to slightly depleted (5–25%) in organic carbon, phosphorus, nitrogen and clay as compared to the eroding topsoil, while the delivered sediment was strongly enriched (+70–270%) but part of this enrichment already resulted from the enrichment of soil loss. The detention ponds temporarily stored 200–500 m3 of runoff. A failure was never experienced. Due to the siltation of the pond bottom, the short filled time (1–5 days) and the small water covered area, infiltration and evaporation reduced runoff by less than 10% for large events. Peak runoff during heavy rains was lowered by a factor of three. Peak concentrations of agrochemicals (Terbutylazin) were lowered by a factor of two. The detention ponds created by raising the downslope field borders at the pour point efficiently reduced adverse erosion effects downslope the eroding site. They are cheap and can easily be created with on-farm machinery. Their efficiency is improved where they are combined with an on-site erosion control like mulch tillage because sediment and runoff input are reduced. Ponds had to be dredged only after the first year when on-site erosion control was not fully effective. 相似文献