全文获取类型
收费全文 | 3874篇 |
免费 | 355篇 |
国内免费 | 1479篇 |
专业分类
安全科学 | 239篇 |
废物处理 | 170篇 |
环保管理 | 701篇 |
综合类 | 2595篇 |
基础理论 | 588篇 |
污染及防治 | 851篇 |
评价与监测 | 294篇 |
社会与环境 | 219篇 |
灾害及防治 | 51篇 |
出版年
2024年 | 6篇 |
2023年 | 49篇 |
2022年 | 112篇 |
2021年 | 125篇 |
2020年 | 114篇 |
2019年 | 151篇 |
2018年 | 153篇 |
2017年 | 175篇 |
2016年 | 241篇 |
2015年 | 219篇 |
2014年 | 280篇 |
2013年 | 362篇 |
2012年 | 370篇 |
2011年 | 397篇 |
2010年 | 316篇 |
2009年 | 410篇 |
2008年 | 229篇 |
2007年 | 272篇 |
2006年 | 263篇 |
2005年 | 257篇 |
2004年 | 171篇 |
2003年 | 157篇 |
2002年 | 141篇 |
2001年 | 112篇 |
2000年 | 102篇 |
1999年 | 90篇 |
1998年 | 68篇 |
1997年 | 63篇 |
1996年 | 58篇 |
1995年 | 70篇 |
1994年 | 41篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有5708条查询结果,搜索用时 515 毫秒
971.
Investigation of titanium liquid/gas diffusion layers in proton exchange membrane electrolyzer cells
Stuart M. Steen III Jingke Mo Zhenye Kang Gaoqiang Yang 《International Journal of Green Energy》2017,14(2):162-170
In a proton exchange membrane electrolyzer cell (PEMEC), liquid/gas diffusion layer (LGDL) is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. In addition, carbon materials, which are typically used in PEM fuel cells (PEMFCs), are unsuitable in PEMECs due to the high ohmic potential and highly oxidative environment of the oxygen electrode. In this study, a set of titanium gas diffusion layers with different thicknesses and porosities are designed and examined coupled with the development of a robust titanium bipolar plate. It has been found that the performance of electrolyzer improves along with a decrease in thickness or porosity of the anode LGDL of titanium woven meshes. The ohmic resistance of anode LGDL and contact resistance between anode LGDL and the anode catalyst play dominant roles in electrolyzer performance, and better performance can be obtained by reducing ohmic resistance. Thin titanium LGDLs with straight-through pores and optimal pore morphologies are recommended for the future developments of low-cost LGDLs with minimum ohmic/transport losses. 相似文献
972.
Detention Outlet Retrofit Improves the Functionality of Existing Detention Basins by Reducing Erosive Flows in Receiving Channels 下载免费PDF全文
Robert J. Hawley James A. Goodrich Nora L. Korth Christopher J. Rust Elizabeth V. Fet Craig Frye Katherine R. MacMannis Matthew S. Wooten Mark Jacobs Rajib Sinha 《Journal of the American Water Resources Association》2017,53(5):1032-1047
By discharging excess stormwater at rates that more frequently exceed the critical flow for stream erosion, conventional detention basins often contribute to increased channel instability in urban and suburban systems that can be detrimental to aquatic habitat and water quality, as well as adjacent property and infrastructure. However, these ubiquitous assets, valued at approximately $600,000 per km2 in a representative suburban watershed, are ideal candidates to aid in reversing such cycles of channel degradation because improving their functionality would not necessarily require property acquisition or heavy construction. The objective of this research was to develop a simple, cost‐effective device that could be installed in detention basin outlets to reduce the erosive power of the relatively frequent storm events (~ < two‐year recurrence) and provide a passive bypass to maintain flood control performance during infrequent storms (such as the 100‐year recurrence). Results from a pilot installation show that the Detain H2O device reduced the cumulative sediment transport capacity of the preretrofit condition by greater than 40%, and contributed to reduced flashiness and prolonged baseflows in receiving streams. When scaling the strategy across a watershed, these results suggest that potential gains in water quality and stream channel stability could be achieved at costs that are orders of magnitude less than comparable benefits from newly constructed stormwater control measures. 相似文献
973.
Designing and Implementing a Network for Sensing Water Quality and Hydrology across Mountain to Urban Transitions 下载免费PDF全文
Amber Spackman Jones Zachary T. Aanderud Jeffery S. Horsburgh David P. Eiriksson Dylan Dastrup Christopher Cox Scott B. Jones David R. Bowling Jonathan Carlisle Gregory T. Carling Michelle A. Baker 《Journal of the American Water Resources Association》2017,53(5):1095-1120
Water resources are increasingly impacted by growing human populations, land use, and climate changes, and complex interactions among biophysical processes. In an effort to better understand these factors in semiarid northern Utah, United States, we created a real‐time observatory consisting of sensors deployed at aquatic and terrestrial stations to monitor water quality, water inputs, and outputs along mountain to urban gradients. The Gradients Along Mountain to Urban Transitions (GAMUT) monitoring network spans three watersheds with similar climates and streams fed by mountain winter‐derived precipitation, but that differ in urbanization level, land use, and biophysical characteristics. The aquatic monitoring stations in the GAMUT network include sensors to measure chemical (dissolved oxygen, specific conductance, pH, nitrate, and dissolved organic matter), physical (stage, temperature, and turbidity), and biological components (chlorophyll‐a and phycocyanin). We present the logistics of designing, implementing, and maintaining the network; quality assurance and control of numerous, large datasets; and data acquisition, dissemination, and visualization. Data from GAMUT reveal spatial differences in water quality due to urbanization and built infrastructure; capture rapid temporal changes in water quality due to anthropogenic activity; and identify changes in biological structure, each of which are demonstrated via case study datasets. 相似文献
974.
975.
Shelly L. Miller Peter Scaramella Joseph Campe Cynthia W. Goss Sandra Diaz-Castillo Ed Hendrikson Carolyn DiGuiseppi Jill Litt 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5661-5667
An indoor air quality assessment was conducted on 100 homes of recent Mexican immigrants in Commerce City, Colorado, an urban industrial community north of Denver. Head of households were administered a family health survey, filled out an activity diary, and participated in a home inspection. Carbon monoxide (CO) and carbon dioxide (CO2) were measured for 24 h inside the main living area and outside of the homes. Harvard Impactors were used to collect 24-h samples of PM2.5 at the same locations for gravimetric analysis. Dust samples were collected by vacuuming carpeting and flooring at four locations within the home and analyzed by ELISA for seven allergens. Mean indoor and outdoor PM2.5 levels were 27.2 and 8.5 μg m−3, respectively. Indoor PM2.5 and CO2 were elevated in homes for which the number of hours with door/window open was zero compared to homes in which the number of hours was high (>15 h). Indoor PM2.5 levels did not correlate with outdoor levels and tended to increase with number of inhabitants, and results indicate that the source of indoor particles were occupants and their activities, excluding smoking and cooking. Mean indoor CO2 and CO levels were 1170 and 2.4 ppm, respectively. Carbon monoxide was higher than the 24-h National Ambient Air Quality Standard in 3 of the homes. The predominant allergens were cat (Fel d 1) and mouse (Mus m 1) allergens, found in 20 and 34 homes, respectively. 相似文献
976.
壳聚糖/纳米CdS复合颗粒可见光光催化降解猩红B动力学研究 总被引:2,自引:0,他引:2
采用仿生矿化法制备了壳聚糖/纳米CdS复合颗粒光催化剂,并用于可见光光催化降解猩红B染料模拟废水,研究了猩红B初始浓度、pH、催化剂投加量和催化剂重复使用次数等因素对猩红B光催化降解的影响.X射线衍射(XRD)分析表明,壳聚糖能有效负载CdS纳米微晶.采用Langmuir-Hinshelwood模型描述壳聚糖/纳米CdS复合颗粒可见光光催化降解猩红B反应动力学行为,在猩红B初始质量浓度较低(≤20 mg/L)时,光催化降解过程符合假一级动力学方程.降低猩红B初始浓度和溶液pH都可显著增大光催化降解速率常数;催化剂投加量小于0.7 g/L时,光催化降解速率随其增加而增大,但催化剂投加量过大会使光催化降解速率减小;催化剂重复使用第5次时,猩红B光催化降解速率常数仍为第1次使用时的63.4%. 相似文献
977.
CaO/SiO2对流化床焚烧飞灰熔融过程中重金属挥发的影响 总被引:1,自引:1,他引:0
对掺煤混烧的流化床焚烧飞灰熔融过程中重金属在气相(吸收率)中和固相(固定率)中的分布进行了研究,并采用HNO3-NaOH2级吸收方式对气相重金属进行了吸收.结果表明,CaO/SiO2(摩尔比)对重金属的迁移行为有重要影响,CaO/SiO2降低,Cd、Pb固定率总体呈上升趋势;2级吸收对气相重金属的吸收有限,大部分重金属主要溶解在HNO3吸收液中,但NaOH吸收液对Cr的吸收效果好于HNO3吸收液;氯对重金属的挥发有重要影响,当重金属以氯化物形式存在时,其挥发受到SiO2的限制.随着SiO2含量增加,挥发率降低. 相似文献
978.
A new direct thermal desorption-GC/MS method: Organic speciation of ambient particulate matter collected in Golden, BC 总被引:1,自引:0,他引:1
Luyi C. Ding Fu Ke Daniel K.W. Wang Tom Dann Claire C. Austin 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):4894-4902
Particulate matter having an aerodynamic diameter less than 2.5 μm (PM2.5) is thought to be implicated in a number of medical conditions, including cancer, rheumatoid arthritis, heart attack, and aging. However, very little chemical speciation data is available for the organic fraction of ambient aerosols. A new direct thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed for the analysis of the organic fraction of PM2.5. Samples were collected in Golden, British Columbia, over a 15-month period. n-Alkanes constituted 33–98% by mass of the organic compounds identified. PAHs accounted for 1–65% and biomarkers (hopanes and steranes) 1–8% of the organic mass. Annual mean concentrations were: n-alkanes (0.07–1.55 ng m−3), 16 PAHs (0.02–1.83 ng m−3), and biomarkers (0.02–0.18 ng m−3). Daily levels of these organics were 4.89–74.38 ng m−3, 0.27–100.24 ng m−3, 0.14–4.39 ng m−3, respectively. Ratios of organic carbon to elemental carbon (OC/EC) and trends over time were similar to those observed for PM2.5. There was no clear seasonal variation in the distribution of petroleum biomarkers, but elevated levels of other organic species were observed during the winter. Strong correlations between PAHs and EC, and between petroleum biomarkers and EC, suggest a common emission source – most likely motor vehicles and space heating. 相似文献
979.
C/N比和曝气量影响MBR同步硝化反硝化的研究 总被引:9,自引:3,他引:6
通过连续运行MBR研究了C/N比和曝气量对同步硝化反硝化的影响,结果表明,在环境温度13~23℃,MLSS为6.0~6.8 g/L,进水NH+4-N浓度50 mg/L,曝气量0.5 m3/h,HRT为6 h实验条件下,总氮去除率随着进水C/N比的增加而增加,在C/N比为6∶1~8∶1时,TN去除率达到79%~89%,低的C/N比抑制反硝化,过高的C/N比增加了碳源补加的成本。改变反应曝气量,当C/N比为6∶1,曝气量为0.4 m3/h时,TN的去除率达到了最大值85%。曝气量过高或过低,TN去除率均下降。并对在不同曝气量下MBR 内的DO 值分布进行了初步研究。 相似文献
980.
采用浸渍法制备了CuCoOx/TiO2催化剂,考察了焙烧温度、反应温度、氧含量、NO浓度和空间速度对催化剂催化氧化NO性能的影响,并考察了催化剂的抗硫抗水性能。XRD、TPR和BET分析表明,350℃焙烧的催化剂具有CuCo2O4尖晶石结构,比表面积大,对NO的氧化效果好。在空速为5 000 h-1,NO进口浓度500 mg/m3,含氧量10%的条件下,反应温度300℃时NO转化率可达79.5%,250℃时NO转化率接近50%。该催化剂具有良好的单独抗SO2、抗H2O毒化性能,H2O和SO2同时存在时很快失活。该催化剂可用于不同时含H2O和SO2的含NO气体催化氧化后再吸收处理。 相似文献