全文获取类型
收费全文 | 5121篇 |
免费 | 325篇 |
国内免费 | 1951篇 |
专业分类
安全科学 | 446篇 |
废物处理 | 251篇 |
环保管理 | 379篇 |
综合类 | 3145篇 |
基础理论 | 852篇 |
污染及防治 | 1578篇 |
评价与监测 | 278篇 |
社会与环境 | 240篇 |
灾害及防治 | 228篇 |
出版年
2024年 | 8篇 |
2023年 | 97篇 |
2022年 | 251篇 |
2021年 | 241篇 |
2020年 | 221篇 |
2019年 | 179篇 |
2018年 | 207篇 |
2017年 | 272篇 |
2016年 | 235篇 |
2015年 | 288篇 |
2014年 | 372篇 |
2013年 | 480篇 |
2012年 | 436篇 |
2011年 | 408篇 |
2010年 | 340篇 |
2009年 | 343篇 |
2008年 | 349篇 |
2007年 | 359篇 |
2006年 | 296篇 |
2005年 | 216篇 |
2004年 | 192篇 |
2003年 | 190篇 |
2002年 | 173篇 |
2001年 | 187篇 |
2000年 | 168篇 |
1999年 | 165篇 |
1998年 | 134篇 |
1997年 | 110篇 |
1996年 | 87篇 |
1995年 | 102篇 |
1994年 | 62篇 |
1993年 | 59篇 |
1992年 | 54篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 24篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有7397条查询结果,搜索用时 15 毫秒
981.
Yong MinXiaogang Jin Jie Chang Changhui PengBaojing Gu Ying GeYang Zhong 《Ecological modelling》2011,222(17):3277-3284
Indirect effects are assumed to be the major causes of the complexity and stability of ecological networks. The complexity of urban-rural complexes (URCs) could also be attributed to the indirect effects associated with human activities. No studies, however, have quantified the strength of indirect effects in relation to urban biogeochemistry. A network environ analysis (NEA) was used for this study to investigate and compare indirect effects in relation to the nitrogen (N) cycling networks of 22 natural ecosystems and five URCs. Results show that indirect effects were proven to be weak for URC N cycling networks (accounting for only ∼2% of the overall effects measured in natural ecosystems). The weak indirect effects found provide a counterexample for the hypothesis that indirect effects are in fact the dominant components of biogeochemical networks. It also implies that human activity in itself does not always raise the complexity of ecological processes as previously suggested. Weak indirect effects also lead to perturbation fragility for URC N cycles (where the decay rate is greater in comparison to natural ecosystems by a factor of 13). In order to improve the robustness and efficiency of URC biogeochemical cycling, a knockout analysis was carried out. By comparing results after removing single interactions between natural ecosystems and URCs it was found that the loss of indirect effects require cooperative strategies to optimize N cycling networks within URCs. 相似文献
982.
Menghong Hu Youji Wang Sau Ting Tsang Siu Gin Cheung Paul K. S. Shin 《Marine Biology》2011,158(7):1591-1600
Energy budget is one of the most studied parameters in aquatic animals under environmental challenge. To examine how prolonged
starvation would affect their energy budget, respiration rate (RR), ammonia excretion rate (ER), oxygen consumption to ammonia–nitrogen
excretion (O:N) ratio and scope for growth (SfG) representing the balance between energy intake and metabolic output, two
Asian horseshoe crab species, Tachypleus tridentatus and Carcinoscorpius rotundicauda, were investigated in two feeding regimes (fed and starved) over a period of 7 weeks. No significant effects of species and
time course, as well as their interaction, on absorption efficiency were observed in the fed treatments. For both species,
RR and ER of the starved treatments significantly decreased, while their O:N ratio significantly increased during the experiment.
However, such values for the fed treatments remained relatively stable over the study period. A rapid reduction in SfG was
only apparent in the first week of the starved treatments for both species; thereafter, their SfG remained relatively constant.
In the fed treatments, SfG of T. tridentatus was significantly lower than that of C. rotundicauda throughout the experiment. In general, C. rotundicauda showed a greater decrease in SfG under starvation than T. tridentatus, suggesting that they may have a more competitive life-history strategy for adjusting to poor nutritional conditions. 相似文献
983.
Anping Zhang Xuemei Xie Jing Ye Chunmian Lin Xiaoyan Hu 《Environmental Chemistry Letters》2011,9(3):369-373
In recent years, the stereoselective toxicity of chiral organophosphorus pesticides has received increasing attention from
environmental toxicology scientists. In an attempt to explore the stereoselective effects of chiral organophosphorus pesticides
on non-target organisms and enzymes, this work investigated the stereoselective toxicity and inhibition of malathion, malaoxon
and isomalathion on Daphnia magna and on acid α-naphthyl acetate esterase extracted from wheat flour, respectively. Toxicity differences were observed between
the two enantiomers of malathion and malaoxon and among the four stereoisomers of isomalathion in the LC50 values on D. magna and the IC50 values on acid α-naphthyl acetate esterase. Enantiomers with (R)-configuration in all the tested compounds showed
higher toxicity to D. magna than their (S)-forms and racemic forms. Racemic malaoxon and isomalathion showed the strongest inhibition on acid α-naphthyl
acetate esterase compared to their respective enantiomers and stereoisomers. 相似文献
984.
985.
986.
Polycyclic aromatic hydrocarbons in effluents from wastewater treatment plants and receiving streams in Tianjin, China 总被引:1,自引:0,他引:1
Weixiao Qi Huijuan Liu Jiuhui Qu Chengzhi Hu Huachun Lan Michael Berg Huimin Ren Wei Xu 《Environmental monitoring and assessment》2011,177(1-4):467-480
Surface water, suspended particulate matter, pore water, and sediment samples were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) in Yongding New River, South Drainage Canal and North Drainage Canal, which receive most of wastewater from industrial city of Tianjin. PAH concentrations in effluent samples of wastewater treatment plants (WTP) discharging into the South Drainage Canal and North Drainage Canal were quantified for the first time. The results showed that the discharge of the WTPs recently only contributed to the PAH contamination in the canals near the outlets of the WTPs. PAH levels in sediments of the streams were greatly higher than those in soils by riverbank probably due to receiving large amounts of untreated wastewater. Unusually high benz[a] anthracene concentration strongly influenced the seasonal and spatial variation of total PAH concentrations in South Drainage Canal. Paired samples t test of ??Nap, Fl, Phe, Fluo and ??Nap, Phe, Fluo, Chry concentrations, which were dominant components in the air samples from non-heating and heating season, respectively, in the suspended particulate matters from the streams showed that PAH source from air deposition was more important for Yongding New River than that for South Drainage Canal and North Drainage Canal. Source apportionment based on PAH profiles indicated that coal combustion was the major PAH contamination source, and coke oven sources and wood combustion also contributed to the PAH contamination of the streams. This was further indicated by organic petrography analysis. 相似文献
987.
988.
为减少化工事故频发造成严重人员伤亡及财产损失,在分析危化品泄漏事故类型的基础上,从事故发生概率和事故后果两方面提出危化品泄漏事故风险评估模型.以中毒事故为例,对重庆长寿化工园区内某企业一液氨储罐进行风险评估.基于概率模型计算中毒事故概率,结果表明该储罐发生泄漏引起中毒的概率较小;数值模拟结果显示:影响范围随时间的增加而... 相似文献
989.
综合交通枢纽运营安全集成管理机制的构建 总被引:2,自引:0,他引:2
为提高综合交通枢纽(ITH)运营安全管理的效率和效果,从脆弱性的角度,分析综合交通枢纽运营安全事故的机理和运营安全管理的特性,构建综合交通枢纽运营安全集成管理机制。该机制以安全信息、安全组织和安全资源的协调、集成和优化为核心,包含干扰监测、威胁预警、漏洞修复、事故控制、鲁棒性提升和应急与恢复等实施机制。建立包含管理措施和技术手段的支撑体系。研究表明:脆弱性是综合交通枢纽运营安全事故发生的根源;该机制以脆弱性为突破口,通过若干管理措施和技术手段,能够实现综合交通枢纽运营安全的全要素、全过程和全资源的集成管理。 相似文献
990.