全文获取类型
收费全文 | 2956篇 |
免费 | 88篇 |
国内免费 | 683篇 |
专业分类
安全科学 | 110篇 |
废物处理 | 202篇 |
环保管理 | 245篇 |
综合类 | 1145篇 |
基础理论 | 608篇 |
环境理论 | 3篇 |
污染及防治 | 949篇 |
评价与监测 | 177篇 |
社会与环境 | 169篇 |
灾害及防治 | 119篇 |
出版年
2023年 | 37篇 |
2022年 | 129篇 |
2021年 | 89篇 |
2020年 | 49篇 |
2019年 | 60篇 |
2018年 | 105篇 |
2017年 | 80篇 |
2016年 | 103篇 |
2015年 | 139篇 |
2014年 | 151篇 |
2013年 | 240篇 |
2012年 | 147篇 |
2011年 | 206篇 |
2010年 | 180篇 |
2009年 | 173篇 |
2008年 | 171篇 |
2007年 | 130篇 |
2006年 | 136篇 |
2005年 | 93篇 |
2004年 | 141篇 |
2003年 | 113篇 |
2002年 | 101篇 |
2001年 | 150篇 |
2000年 | 98篇 |
1999年 | 79篇 |
1998年 | 71篇 |
1997年 | 74篇 |
1996年 | 54篇 |
1995年 | 63篇 |
1994年 | 35篇 |
1993年 | 45篇 |
1992年 | 34篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1972年 | 12篇 |
1959年 | 5篇 |
1957年 | 5篇 |
排序方式: 共有3727条查询结果,搜索用时 15 毫秒
151.
Daniel Q. Tong Nicholas Z. Muller Haidong Kan Robert O. Mendelsohn 《Environment international》2009,35(8):1109-1117
Human exposure to ambient ozone (O3) has been linked to a variety of adverse health effects. The ozone level at a location is contributed by local production, regional transport, and background ozone. This study combines detailed emission inventory, air quality modeling, and census data to investigate the source–receptor relationships between nitrogen oxides (NOx) emissions and population exposure to ambient O3 in 48 states over the continental United States. By removing NOx emissions from each state one at a time, we calculate the change in O3 exposures by examining the difference between the base and the sensitivity simulations. Based on the 49 simulations, we construct state-level and census region-level source–receptor matrices describing the relationships among these states/regions. We find that, for 43 receptor states, cumulative NOx emissions from upwind states contribute more to O3 exposures than the state's own emissions. In-state emissions are responsible for less than 15% of O3 exposures in 90% of U.S. states. A state's NOx emissions can influence 2 to 40 downwind states by at least a 0.1 ppbv change in population-averaged O3 exposure. The results suggest that the U.S. generally needs a regional strategy to effectively reduce O3 exposures. But the current regional emission control program in the U.S. is a cap-and-trade program that assumes the marginal damage of every ton of NOx is equal. In this study, the average O3 exposures caused by one ton of NOx emissions ranges from ? 2.0 to 2.3 ppm-people-hours depending on the state. The actual damage caused by one ton of NOx emissions varies considerably over space. 相似文献
152.
Chaosheng Zhang Ya Tang Lin Luo Weilin Xu 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):3083-3090
Outliers in urban soil geochemical databases may imply potential contaminated land. Different methodologies which can be easily implemented for the identification of global and spatial outliers were applied for Pb concentrations in urban soils of Galway City in Ireland. Due to its strongly skewed probability feature, a Box–Cox transformation was performed prior to further analyses. The graphic methods of histogram and box-and-whisker plot were effective in identification of global outliers at the original scale of the dataset. Spatial outliers could be identified by a local indicator of spatial association of local Moran's I, cross-validation of kriging, and a geographically weighted regression. The spatial locations of outliers were visualised using a geographical information system. Different methods showed generally consistent results, but differences existed. It is suggested that outliers identified by statistical methods should be confirmed and justified using scientific knowledge before they are properly dealt with. 相似文献
153.
In this paper, Loofa egyptiaca (LE), an agricultural plant cultivated in Egypt, was used to prepare low-cost activated carbon (LEC1 and LEC2) adsorbents. The adsorbents (LE, LEC1 and LEC2) were evaluated for their ability to remove direct blue 106 dye from aqueous solutions. Batch mode experiments were conducted using various parameters such as pH, contact time, dye concentration and adsorbent concentration. The surface chemistry of LE, LEC1 and LEC2 was analyzed by scanning electron microscopy (SEM). The experimental data were examined using Langmuir, Freundlich, Temkin and Harkins–Jura isotherms. The results showed that the adsorption of direct blue 106 was maximal at the lowest value of pH (pH = 2). Removal efficiency was increased with an increase in dye concentration and a decrease in amount of adsorbent. Maximum adsorption capacity was found to be 57.14, 63.3 and 73.53 mg/g for LE, LEC1 and LEC2 respectively. Kinetics were also investigated using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The experimental data fitted very well with the pseudo-first-order and pseudo-second-order kinetic models. The results indicate that LE, LEC1 and LEC2 could be employed as adsorbents for the removal of direct blue dye from aqueous solutions. 相似文献
154.
Mohammednoor Altarawneh Daniel Carrizo Artur Ziolkowski Eric M. Kennedy Bogdan Z. Dlugogorski John C. Mackie 《Chemosphere》2009,74(11):1435-1443
This article reports the computational and experimental results of the thermal decomposition of permethrin, a potential source of dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). We have performed a quantum chemical analysis by applying density functional theory to obtain the decomposition pathways of permethrin and the formation mechanism of dibenzofuran. We have conducted the pyrolysis experiments in a tubular reactor and identified the pyrolysis products to demonstrate the agreement between the experimental measurements and quantum chemical calculations. The initiation of the decomposition of permethrin involves principally the aromatisation of permethrin into 3-phenoxyphenylacetic acid, 2-methylphenyl ester (J) and concomitant loss of 2HCl. This rearrangement is followed by the rupture of the O–CH2 linkage in J, with a rate constant derived from the quantum chemical results of 1 × 1015 exp(−68 kcal/mol/RT) s−1 for temperatures between 700 and 1300 K. This is confirmed by finding that the rate constant for unimolecular rearrangement of permethrin into J is 1.2 × 1012 exp(−53 kcal/mol/RT) s−1 over the same range of temperatures and exceeds the direct fission rate constant at all temperatures up to 850 ± 120 °C as well as by the experimental detection of J prior to the detection of the initial products incorporating diphenyl ether, 1-methyl-3-phenoxybenzene, 3-phenoxybenzaldehyde and 1-chloromethyl-3-phenoxybenzene. As the temperature increases, we observe a rise in secondary products formed directly or indirectly (via phenol/phenoxy) including aromatics (naphthalene), biphenyls (biphenyl, 4-methyl-1,1′-biphenyl) and dibenzofuran (DF). In particular, we discover by means of quantum chemistry a direct route from 2-phenoxyphenoxy to naphthalene. We detect no polychlorinated dibenzo-p-dioxins and dibenzofurans. Unlike the case of oxidative pyrolysis [Tame, N.W., Dlugogorski, B.Z., Kennedy, E.M., 2007b. Formation of dioxins in fires of arsenic-free treated wood: Role of organic preservatives. Environ. Sci. Technol. 41, 6425–6432] where significant yields of both PCDD and PCDF were obtained, under non-oxidative conditions the thermal decomposition of permethrin does not form appreciable amounts of PCDD or PCDF and the presence of oxygen (and/or a sizable radical pool) appears necessary for the formation of dibenzo-p-dioxin itself or PCDD/F from phenol/phenoxy. 相似文献
155.
DGGE、T-RFLP 、LH-PCR对两种活性污泥的微生物种群多样性分析的比较 总被引:8,自引:1,他引:7
采用基于PCR扩增的分子生态技术DGGE、T-RFLP和LH-PCR,对2种典型污水处理系统中的活性污泥(生活污泥、焦化污泥)进行微生物种群多样性分析;并以此比较3种技术的优劣,提出不同应用条件下研究方法的选择依据。根据实验结果:DGGE得到的条带较多,但误差来源也最多;T-RFLP技术较为灵敏,但需要选择适当的内切酶,严格控制酶切条件,并且文库比对误差较大;而LH-PCR操作简单,结果稳定性较高。虽然目前尚无法判断3种方法的准确性,但LH-PCR在活性污泥的微生物种群多样性分析中已显示出潜在优势。 相似文献
156.
基于GIS的耕地土壤重金属污染与农业功能定位研究——以山东省聊城市为例 总被引:1,自引:0,他引:1
按8km×8km的网格将聊城市耕地分为137个采样点,调查砷、镉、铬、铜、汞、镍、铅、锌等重金属的污染状况。采用国家土壤环境质量标准、农产品安全质量标准和绿色食品产地环境条件作为评价标准,采用单因子指数和综合指数为评价方法进行污染评价。研究表明,聊城市土壤污染强度依次为铜〉镍〉锌〉砷〉铬〉镉〉铅〉汞,但均未超标。以GIS为操作平台显示聊城市重金属空间分布状况,并对区域耕地进行了功能的定位。聊城市西南部土壤质量最优,适宜种植绿色食品;无公害蔬菜和安全粮食种植区在各县市均有不同程度的分布。 相似文献
157.
干法腈纶生产废水脱氨氮研究 总被引:1,自引:0,他引:1
采用本实验室富集驯化的高效硝化细菌对生化处理后的干法腈纶生产废水进行了脱NH3-N研究,在连续运行装置中考察了DO和MLSS的变化特征,并研究了废水NH3-N负荷和COD负荷对脱NH3-N效果的影响.实验结果表明:该菌能适应干法腈纶生产废水中的难生物降解物质并有效去除废水中的NH3-N,启动期DO呈现"高-低-高"的变化,运行期污泥增长速率呈现"S"型变化;进水NH3-N负荷达到0.405 kg/(m3·d)时仍能维持出水P(NH3-N)在5 mg/L以下,进水COD负荷由0.126 kg/(m3·d)提高到0.975 kg/(m3·d)的过程中,NH3-N去除率始终高于96%. 相似文献
158.
159.
160.
Vanderstraeten P Lénelle Y Meurrens A Carati D Brenig L Offer ZY Zaady E 《Environmental monitoring and assessment》2008,146(1-3):33-39
The main objective of our research was to compare the airborne particle micromorphology and chemistry in the Brussels environment during agriculture working periods in the surrounding farming region. We used specific methods and instrumentation that are adapted to the climate peculiarities of the Brussels region, the period of investigations (12 months) and the proposed objectives. For the agricultural works we defined the following six periods: before sowing, sowing, after sowing, before harvest, harvest and after harvest. The results indicate a possible temporal correlation between agricultural work periods and airborne particle concentration, micromorphology and chemistry in the Brabant-Brussels region. For wheat and corn plant-growth periods, the average particle size, defined as the area obtained by a planar projection of the particulate, showed important variations in time. For sugar beet and endive, the average area size variations are less important. The roughness and sphericity parameters for the growth periods of the four different plants also showed significant differences. Many of the larger particulates (> 10 microm) are aggregates of even finer particles coated with many still finer ones. The airborne particle chemistry averages (atomic percentage At%), showed that three constituents (Si, S and Fe) dominate all the samples (except for particles 3-10 microm in size, which contain a relatively large percentage of Al). Applying similar investigation methods to study the correlations between airborne particle dynamics in urban zones and the agriculture working periods in their surrounding regions could be of interest to better understand the complexity of the PM problematic. 相似文献