全文获取类型
收费全文 | 6086篇 |
免费 | 486篇 |
国内免费 | 2083篇 |
专业分类
安全科学 | 487篇 |
废物处理 | 281篇 |
环保管理 | 466篇 |
综合类 | 3742篇 |
基础理论 | 951篇 |
环境理论 | 1篇 |
污染及防治 | 1647篇 |
评价与监测 | 371篇 |
社会与环境 | 514篇 |
灾害及防治 | 195篇 |
出版年
2024年 | 33篇 |
2023年 | 152篇 |
2022年 | 389篇 |
2021年 | 371篇 |
2020年 | 364篇 |
2019年 | 299篇 |
2018年 | 293篇 |
2017年 | 365篇 |
2016年 | 379篇 |
2015年 | 419篇 |
2014年 | 466篇 |
2013年 | 554篇 |
2012年 | 504篇 |
2011年 | 492篇 |
2010年 | 393篇 |
2009年 | 380篇 |
2008年 | 416篇 |
2007年 | 301篇 |
2006年 | 326篇 |
2005年 | 216篇 |
2004年 | 182篇 |
2003年 | 203篇 |
2002年 | 188篇 |
2001年 | 154篇 |
2000年 | 166篇 |
1999年 | 105篇 |
1998年 | 107篇 |
1997年 | 80篇 |
1996年 | 71篇 |
1995年 | 48篇 |
1994年 | 51篇 |
1993年 | 45篇 |
1992年 | 37篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1986年 | 8篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有8655条查询结果,搜索用时 15 毫秒
771.
772.
Selective extraction and separation of Fe, Mn oxides and organic materials in river surficial sediments 总被引:2,自引:0,他引:2
In order to investigate the adsorption mechanism of trace metals to surficial sediments (SSs), a selective extraction procedure was improved in the present work. The selective extraction procedure has been proved to selectively remove and separate Fe, Mn oxides and organic materials (OMs) in the non-residual fraction from the SSs collected in Songhua River, China. After screening different kinds of conventional extractants of Fe and Mn oxides and OMs used for separation of heavy metals in the soils and sediments, NH2OH .HCl (0.1 mol/L) + HNO3 (0.1 mol/L), (NH4)2C2O4 (0.2 mol/L) + H2C2O4 (pH 3.0), and 30% of H2O2 were respectively applied to selectively extract Mn oxides, Fe/Mn oxides and OMs. After the extraction treatments, the target components were removed with extraction efficiencies between 86.09%--3.36% for the hydroxylamine hydrochloride treatment, 80.63%- 101.09% for the oxalate solution extraction, and 94.76%-102.83% for the hydrogen peroxide digestion, respectively. The results indicate that this selective extraction technology was effective for the extraction and separation ofFe, Mn oxides and OMs in the SSs, and important for further mechanism study of trace metal adsorption onto SSs. 相似文献
773.
Effective removal of coordinated copper from wastewater using a new dithiocarbamate-type supramolecular heavy metal precipitant 总被引:1,自引:0,他引:1
A new dithiocarbamate-type heavy metal precipitant, sodium 1,3,5-hexahydrotriazinedithiocarbamate (HTDC), was prepared and used to remove coordinated copper from wastewater. In the reported dithiocarbamate-type precipitants, HTDC possesses the highest percentage of the effective functional groups. It could effectively precipitate copper to less than 0.5 mg l−1 from both synthetic and actual industrial wastewater containing CuEDTA in the range of pH 3–9. UV–vis spectral investigation and elemental analysis suggested that the precipitate was a kind of coordination supramolecular compound, [Cu3(HTDC)2]n. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) indicated that the supramolecular precipitate was non-hazardous and stable in weak acid and alkaline conditions. Tests of an anion exchange resin D231 provided a clue to simultaneously remove excess HTDC and residual CuEDTA in practical process of wastewater treatment. 相似文献
774.
Chang RR Wang SL Tzou YM Chen YM Wang MK 《Journal of environmental science and health. Part. B》2011,46(2):128-136
Removal of 2-chlorophenol from water using rice-straw derived ash (RSDA) was evaluated in this study to compare with commercial activated carbon. RSDA was obtained by burning rice-straw at 400 °C and 700 °C for 1 h. This ash can provide a better adsorbent for 2-chlorophenol. The adsorption capacities of RSDA at 400 °C and 700 °C are 37 and 52 mg g?1 at pH 4, respectively, and decrease to 9.0 and 40 mg g?1 at pH 10. Adsorption of either neutral or anionic 2-cholorphenol by the RSDA are shown as L-shaped nonlinear isotherms, suggesting surface adsorption rather than partitioning is occurring. At higher-burning temperatures, the surface area, porosity, point of zero charge and aromaticity of the resultant RSDA increase, but the oxygen content and surface acidity decrease. The combined effects result in a higher 2-chlorophenol adsorption of RSDA at 700 °C, which shows a slight pH effect on the adsorption of 2-chlorophenol, due to the lower content of oxygen-containing functional groups. Oxygen-containing functional groups contribute to surface acidity and H-bonding sites for adsorbed water, which compromises the interaction between 2-chlorophenol and the adsorbents. Thus, it suggests that rice-straw derived carbon (RSDC) can be used as an effective low-cost substitute material for activated carbon for removal of chlorophenols from wastewater. 相似文献
775.
Two-phase flow insights into open-channel flows with suspended particles of different densities 总被引:1,自引:0,他引:1
The effect of particle density on the turbulent open-channel flow carrying dilute particle suspensions is investigated using
two specific gravities and three concentrations of solid particles. The particles, identical in size and similar in shape,
were natural sand and a neutrally buoyant plastic. The particles were fully suspended, and formed no particle streaks on the
channel’s bed. Accordingly, the changes in the flow are attributed to the interactions between suspended particles and flow
turbulence structures. Measurements were obtained by means of image velocimetry enabling simultaneous, but distinct, measurement
of liquid and particle velocities. The experimental results show that, irrespective of particle specific gravity, particle
suspension influences bulk velocity of flow and the Kármán coefficient, while friction velocity essentially remains constant.
The results also show that particles in suspension modify local water turbulence over the flow depth, but in ways not accurately
predicted using the customary parameters for characterizing turbulence modification. 相似文献
776.
利用EXCEL求算水中非离子氨 总被引:2,自引:0,他引:2
Excel是办公自动化中非常重要的一款软件,它的数据处理功能在现有的文字处理软件中可以说是独占螯头,通过简单的学习,结合国家标准给出的换算公式,利用EXCEL编制程序,方便快捷地计算水中非离子氨浓度,计算结果表明,当实际测得水温和pH与表中数据吻合时三种计算方法结果无明显差异,当实际测得的水温和pH与表中不对应时,查表法存在明显偏差,而使用EXCEL运算就能与笔算结果一致,准确可靠。 相似文献
777.
778.
779.
机动车排放遥感监测反映实际道路行驶中的排放状况,对全面分析排放水平有很强的统计意义。北京市机动车排放遥感监测的CO、HC和NOx的平均浓度分别为1.94%、388×10-6和700×10-6。北京市机动车排放的CO、HC和NOx中50%分别来自于15.90%、13.98%、11.13%的高排放车,但某车辆对于一种污染物出现高排放并不意味着它对其他污染物也是高排放。根据遥感监测得到北京市轻型汽油车基于油耗的CO、HC和NOx平均尾气管排放因子分别为200.1g/L、11.05 g/L和6.68 g/L。 相似文献
780.
四种净水工艺对水源水微量有机物去除的研究 总被引:1,自引:0,他引:1
以UV254和CODMn代表饮用水源水中有机物替代指标.对常规处理、生物陶粒预处理、生物滤池、生物活性炭(BAC)、颗粒活性炭(GAC)、纳滤和光催化氧化进行组合,形成不同的处理流程,研究各流程对UV254和CODMn的去除效果.结果表明,各工艺流程都有一定的处理效率,其中以生物滤池和纳滤为主的组合流程处理效果最佳.此流程对UV254的去除率接近100%,CODMn的去除率达到78.6%,大大提高了饮用水的安全性. 相似文献