全文获取类型
收费全文 | 2335篇 |
免费 | 242篇 |
国内免费 | 656篇 |
专业分类
安全科学 | 422篇 |
废物处理 | 74篇 |
环保管理 | 342篇 |
综合类 | 1451篇 |
基础理论 | 271篇 |
污染及防治 | 289篇 |
评价与监测 | 100篇 |
社会与环境 | 185篇 |
灾害及防治 | 99篇 |
出版年
2024年 | 4篇 |
2023年 | 42篇 |
2022年 | 58篇 |
2021年 | 95篇 |
2020年 | 97篇 |
2019年 | 78篇 |
2018年 | 62篇 |
2017年 | 98篇 |
2016年 | 121篇 |
2015年 | 103篇 |
2014年 | 134篇 |
2013年 | 172篇 |
2012年 | 168篇 |
2011年 | 208篇 |
2010年 | 146篇 |
2009年 | 156篇 |
2008年 | 120篇 |
2007年 | 206篇 |
2006年 | 163篇 |
2005年 | 125篇 |
2004年 | 104篇 |
2003年 | 112篇 |
2002年 | 92篇 |
2001年 | 71篇 |
2000年 | 68篇 |
1999年 | 73篇 |
1998年 | 61篇 |
1997年 | 55篇 |
1996年 | 39篇 |
1995年 | 33篇 |
1994年 | 29篇 |
1993年 | 34篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有3233条查询结果,搜索用时 515 毫秒
21.
选取三峡库区支流御临河为研究对象,测量了5个水动力条件(平均流速为0.00,0.03,0.07,0.12,0.20m/s)下沉积物-水界面(SWI)氧通量的变化及水动力条件对SWI氧通量产生机制的影响.结果表明,随着平均流速的升高,SWI氧通量增加,由0.00m/s时的1.197mmol/(m2·h)增加为0.20m/s时的43.981mmol/(m2·h),溶解氧穿透深度增加,氧进入沉积物更深处并被微生物和还原性物质所利用,沉积物耗氧量上升;当平均流速较低时,沉积物耗氧量以生物耗氧量为主,在0.00m/s与0.03m/s时生物耗氧量为氧通量的85.3%与57.7%;当水体平均流速较高,化学耗氧量与其他耗氧量中的化学过程耗氧量在氧通量中的比重逐步提高. 相似文献
22.
23.
Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). Near-atomic resolution elemental mappings of Cr(Ⅵ)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(Ⅵ) encapsulation are strongly dependent on the initial concentration of Cr(Ⅵ) in solution. Low Cr loading in nZⅥ(1.0 wt%) promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading(1.0 wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(Ⅵ)(e.g., 10 mg/L). Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr(Ⅵ)(e.g., 100 mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy(XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxides with Cr(Ⅵ) adsorbed on the outside surface. The insoluble and insulating Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr(Ⅵ) solution is detrimental to the performance of nZⅥ for Cr(Ⅵ) treatment and remediation. 相似文献
24.
25.
Review on the annual PM10 concentrations over a 10-year period shows that Macau is subjected to severe fine particulate pollution. Investigations of its variation in monthly and daily time scales with the local meteorological records reveal further details. It is found that a distinct feature of the Asian monsoon climates, the changes of wind direction, mainly controls the general trend of PM10 concentration in a year. The monsoon driven winter north-easterly winds bring upon Macau dry and particle enriched air masses leading to a higher concentration in that period while the summer south-westerly winds transport humid and cleaner air to the region leading to a lower PM10 value. This distinct seasonal feature is further enhanced by the lower rainfall volume and frequency as well as mixing height in winter and their higher counterparts in summer. It is also found that the development of tropical cyclones near Macau could also impose episode like PM10 concentration spikes due to the pre-typhoon induced stagnant air motion followed by the swing of wind direction to the northerly. 相似文献
26.
27.
鲍学杰 《环境监测管理与技术》1996,8(5):9-11
指出了环境污染纠纷调处与环境行政处罚的性质,程序,结果等均不相同,在理论上不能将两者混一谈,实践中应区别对待。 相似文献
28.
分析了《征收排污费暂行办法》在新形势下存在的问题,并从排污费的征收,管理和使用等方面提出了修改建议。 相似文献
29.
基于网格空间数据的晋陕蒙接壤区生态环境综合评价 总被引:6,自引:0,他引:6
晋陕蒙接壤区是典型的生态过渡带、生态脆弱带。文章在调查研究的基础上 ,选取了 1 3个评价指标 ,应用层次分析法确定其权重 ,并将各个因子分级标准化和定量赋值 ,再用加权求和法得到每个评价单元的环境质量综合评价指数。根据环境综合评价指数将环境质量分为较好 (≥ 8)、一般 (≥ 6~ <8)、较差 (≥ 4~ <6)、恶劣 (<4) 4级。结果表明 :晋陕蒙接壤区的环境质量大多处于较差等级 ,较好、一般、较差、恶劣等级的面积比例分别为 2 .2 % ,2 8% ,5 7.4%和1 2 .4% 相似文献
30.
The degradation of several biodegradable polymers was measured as a result of exposure to an anaerobic medium. The polymers investigated included materials based upon polylactic acid, polylactone, and poly(hydroxy butyrate/valerate) as well as those incorporating starch-based materials. The degradation was monitored by methane and carbon dioxide evolution. In addition, the physical and chemical changes were noted as a result of exposure. These measurements included changes in mass, dimension, and molecular weight. FTIR, UV-vis, proton, and13C NMR spectra were also recorded prior to and after exposure. The results clearly indicated that several biological and chemical degradation processes were occurring with the biodegradable polymers studied.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Issued as NRCC No. 37549. 相似文献