全文获取类型
收费全文 | 2505篇 |
免费 | 86篇 |
国内免费 | 703篇 |
专业分类
安全科学 | 131篇 |
废物处理 | 167篇 |
环保管理 | 195篇 |
综合类 | 1114篇 |
基础理论 | 435篇 |
环境理论 | 1篇 |
污染及防治 | 966篇 |
评价与监测 | 111篇 |
社会与环境 | 58篇 |
灾害及防治 | 116篇 |
出版年
2023年 | 35篇 |
2022年 | 107篇 |
2021年 | 104篇 |
2020年 | 64篇 |
2019年 | 68篇 |
2018年 | 73篇 |
2017年 | 109篇 |
2016年 | 131篇 |
2015年 | 120篇 |
2014年 | 212篇 |
2013年 | 253篇 |
2012年 | 225篇 |
2011年 | 230篇 |
2010年 | 173篇 |
2009年 | 164篇 |
2008年 | 164篇 |
2007年 | 142篇 |
2006年 | 142篇 |
2005年 | 98篇 |
2004年 | 68篇 |
2003年 | 80篇 |
2002年 | 68篇 |
2001年 | 50篇 |
2000年 | 49篇 |
1999年 | 57篇 |
1998年 | 51篇 |
1997年 | 53篇 |
1996年 | 31篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1958年 | 2篇 |
排序方式: 共有3294条查询结果,搜索用时 562 毫秒
911.
失业保险制度产生于20世纪初.在发展初期,以强调基本生活保障为主.20世纪70年代,西方国家充分就业的阶段宣告结束.到了80年代,由于石油危机的影响,通货膨胀严重,国际竞争更趋激烈,很多国家的失业率大幅攀升,形成了自20世纪30年代以来最严重的失业局面.为减轻失业压力,很多国家大幅度改革了失业保险制度和公共就业服务制度. 相似文献
912.
Establishing a simple yet reliable compost stability test is essential for a better compost quality control and utilization efficiency. The objective of this study was to examine the relationship between extractable organic carbon (OC) and compost stability based on 18 compost samples from five composting facilities. The compost samples were extracted sequentially with water for 2 h [water(2h)] and 0.1 M NaOH for 2 and 24 h [NaOH(2h) and NaOH(24h), respectively]. The extractable OC was further separated into fulvic acid (FA) and humic acid (HA) fractions by adjusting the pH to <2. The mass specific absorbance (MSA) of OC in the six fractions was measured. Compost stability was estimated with a CO2 evolution method. The extractable OC concentration was influenced by the total volatile solids and decreased with curing time for compost with a high level of extractable OC. The OC levels in each fraction were significantly correlated (p < 0.05) to each other except for the water(2h)-extractable HA. In addition, all the FA and HA fractions except for water(2h)-extractable HA were highly (P < 0.01) and linearly correlated to CO2 evolution, but multiple regression showed that NaOH(24h)-extractable OC was insignificant for CO2 evolution. The relatively high slope of NaOH(2h)-extractable FA versus CO2 evolution suggests that this fraction may contribute the most to compost CO2 evolution. The water(2h)- and/or NaOH(2h)-extractable FA tests are recommended for measuring compost stability because of their high correlation with CO2 evolution. This estimation can be obtained through a simple photometric method covering a wide range of carbon concentrations up to 4,000 mg L(-1). 相似文献
913.
Ladder brake (Pteris vittata L.) is a newly discovered arsenic hyperaccumulator. No information is available about arsenic effects on ladder brake. This study determined the effects of different arsenic concentrations (50 to 1000 mg kg(-1)) or forms (organic vs. inorganic and arsenite vs. arsenate) applied to soils on growth and arsenic uptake by ladder brake. Young plants were grown in a greenhouse for 12 or 18 wk. Ladder brake was highly tolerant of arsenic and survived in soil containing up to 500 mg As kg(-1). The fact that addition of arsenate up to 100 mg As kg(-1) increased fern biomass by 64 to 107%, coupled with higher arsenic concentration in younger fronds at low soil arsenic concentrations and older fronds at high soil arsenic concentrations, implies that arsenic may be beneficial for fern growth. Addition of 50 mg As kg(-1) was best for fern growth and arsenic accumulation, resulting in the highest fern biomass (3.9 g plant(-1)), bioconcentration factor (up to 63), and translocation factor (up to 25). With an exception of FeAsO4 and AlAsO4, which had the lowest effects due to their low solubility, little difference was observed among other arsenic forms mainly because of arsenic conversion in soil. Aboveground biomass was mostly responsible for accumulation of arsenic by plant (75-99%). Up to 26% of the added arsenic was removed by ladder brake, showing the high efficiency of ladder brake in arsenic removal. The results suggest that ladder brake may be a good candidate to remediate arsenic-contaminated soils. 相似文献
914.
915.
916.
重视职工安全心理与需要 总被引:2,自引:0,他引:2
通过对职工安全心理过程 ,职工个性差异 ,管理人员安全心理以及职工安全需要的分析 ,阐述了其与企业安全生产的关系 ,并提出了满足职工安全需要 ,促进企业安全生产的途径 相似文献
917.
918.
固定床PVC燃烧脱氯的机理和试验 总被引:14,自引:2,他引:12
研究垃圾组分PVC在焚烧过程中HCl的排放和脱除特性的实验在准等温、电加热的水平石英管反应器中进行.随着床温从700℃升高到900℃,HCl的转化率从82.5%平缓增加到88.3%,而过量空气系数的增加促使部分HCl转化为C12(1.9%~4.5%)的形式存在.钙基吸收剂CaCO3,Ca(OH)2,Ca(CH3COO)2对HCl的脱除效率高达68%~79%,而镁基吸收剂的脱氯效率却低于3%.小的吸收剂粒径、高的Ca/Cl比会促进脱氯效率的提高;烟气中CO2和H2O对脱氯效率的影响与它们在反应平衡中所起作用有关.高温下燃烧固氯机理反应的平衡常数的计算不仅诠释了实验结果,而且提供了脱氯吸收剂选择的依据. 相似文献
919.
920.