首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5088篇
  免费   367篇
  国内免费   1942篇
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
  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
1.
探究土地利用方式对长江中游小流域土壤团聚体稳定性的影响,为鄂西地区土地合理利用与管理以及土壤结构改良提供借鉴.以下牢溪小流域5种不同土地利用方式(柏树林、蔬菜地、石坎农田、撂荒地、天然林)土壤为研究对象,对比分析各土地利用方式间土壤团聚体粒径组成及稳定性差异.结果 表明:(1)柏树林、石坎农田、撂荒地和天然林土壤团聚体以>2 mm为优势粒级,平均为57.66%,蔬菜地以<0.25 mm微粒径团聚体为主,均值为60.86%;(2)林地(柏树林和天然林)土壤稳定性和抗蚀性要优于农用地(石坎农田和蔬菜地),耕地撂荒提升团聚体稳定性;(3)分形维数D与破坏率PAD、可蚀性K呈正相关,与团聚体直径(MWD和GMD)和水稳性大团聚体WR0.25呈负相关,分形维数较好反映小流域土壤团聚体的稳定性和抗侵蚀性.对流域内林区的封育是提升土壤结构稳定性的最优管理方式.  相似文献   
2.
Chen  Hongqiang  Lin  Lijin  Liao  Ming’an  Wang  Jin  Tang  Yi  Sun  Guochao  Liang  Dong  Xia  Hui  Deng  Qunxian  Wang  Xun  Lv  Xiulan  Ren  Wei 《Environmental science and pollution research international》2019,26(24):24474-24481
Environmental Science and Pollution Research - Grapevine (Vitis vinifera L.) intercropping with floricultural cadmium (Cd) accumulator plants (Helianthus annuus L., Cosmos sulphureus Cav., Cosmos...  相似文献   
3.

A process combining catalyzed Fe(0)-carbon microelectrolysis (IC-ME) with activated carbon (AC) adsorption was developed for advanced reclaimed water treatment. Simultaneous nitrate reduction and chemical oxygen demand (COD) removal were achieved, and the effects of composite catalyst (CC) addition, AC addition, and initial pH were investigated. The reaction kinetics and reaction mechanisms were calculated and analyzed. The results showed that CC addition could enhance the reduction rate of nitrate and effectively inhibit the production of ammonia. Moreover, AC addition increased the adsorption capacity of biorefractory organic compounds (BROs) and enhanced the degradation of BRO. The reduction of NO3?–N at different pH values was consistently greater than 96.9%, and NH4+–N was suppressed by high pH. The presence of CC ensured the reaction rate of IC-ME at high pH. The reaction kinetics orders and constants were calculated. Catalyzed iron scrap (IS)-AC showed much better nitrate reduction and BRO degradation performances than IS-AC and AC. The IC-ME showed great potential for application to nitrate and BRO reduction in reclaimed water.

  相似文献   
4.
为了解石家庄市2016年春季大气颗粒物的铅污染特征及来源,利用单颗粒气溶胶质谱仪(SPAMS),分析了大气中含铅颗粒的化学成分。结果表明: 研究期间大气环境中含铅颗粒数浓度共出现11次跳跃式升高,跳跃时间段内石家庄均处于轻度污染过程。从成分分析来看,含铅颗粒分为纯铅颗粒、Pb与K(Pb-K)、OC(Pb-OC)、Cl(Pb-Cl)、混合颗粒等八大类。观测结果表明:Pb-K颗粒最多,占到含铅颗粒的84.4%;其次为纯铅颗粒,占比为13.0%。与石家庄市污染源谱库比对进行来源解析,得到Pb-K颗粒主要来自生活垃圾焚烧源, 纯铅颗粒主要来自工业源。结合石家庄市大气污染源排放清单和后向气流轨迹分析,推测含铅颗粒可能来自市区西南方向某区县的生活垃圾焚烧企业。  相似文献   
5.
The lack of high-resolution distribution maps for freshwater species across large extents fundamentally challenges biodiversity conservation worldwide. We devised a simple framework to delineate the distributions of freshwater fishes in a high-resolution drainage map based on stacked species distribution models and expert information. We applied this framework to the entire Chinese freshwater fish fauna (>1600 species) to examine high-resolution biodiversity patterns and reveal potential conflicts between freshwater biodiversity and anthropogenic disturbances. The correlations between spatial patterns of biodiversity facets (species richness, endemicity, and phylogenetic diversity) were all significant (r = 0.43–0.98, p < 0.001). Areas with high values of different biodiversity facets overlapped with anthropogenic disturbances. Existing protected areas (PAs), covering 22% of China's territory, protected 25–29% of fish habitats, 16–23% of species, and 30–31% of priority conservation areas. Moreover, 6–21% of the species were completely unprotected. These results suggest the need for extending the network of PAs to ensure the conservation of China's freshwater fishes and the goods and services they provide. Specifically, middle to low reaches of large rivers and their associated lakes from northeast to southwest China hosted the most diverse species assemblages and thus should be the target of future expansions of the network of PAs. More generally, our framework, which can be used to draw high-resolution freshwater biodiversity maps combining species occurrence data and expert knowledge on species distribution, provides an efficient way to design PAs regardless of the ecosystem, taxonomic group, or region considered.  相似文献   
6.
针对压力容器制造监检中某些受检单位在法规标准的理解上存在误区或者疏忽、不知如何进行后续整改工作的现状,笔者结合多年压力容器监督检验的工作经验,提出自己的解决方案,以供参考,也希望广大读者在遇到类似情况时能够正确理解并执行相关法规标准。  相似文献   
7.
Environmental Science and Pollution Research - The estuarine delta of the Yellow River is a region of strong land-ocean-human interactions that undergoes a unique evolutionary process. The delta is...  相似文献   
8.
Objective: Electric bike/moped-related road traffic injuries have become a burgeoning public health problem in China. The objective of this study was to identify the prevalence and potential risk factors of electric bike/moped-related road traffic injuries among electric bike/moped riders in southern China.

Methods: A cross-sectional study was used to interview 3,151 electric bike/moped riders in southern China. Electric bike/moped-related road traffic injuries that occurred from July 2014 to June 2015 were investigated. Data were collected by face-to-face interviews and analyzed between July 2015 and June 2017.

Results: The prevalence of electric bike/moped-related road traffic injuries among the investigated riders was 15.99%. Electric bike/moped-related road traffic injuries were significantly associated with category of electric bike (adjusted odds ratio [AOR] = 1.36, 95% confidence interval [CI], 1.01–1.82), self-reported confusion (AOR = 1.77, 95% CI, 1.13–2.78), history of crashes (AOR = 6.14, 95% CI, 4.68–8.07), running red lights (AOR = 3.57, 95% CI, 2.42–5.25), carrying children while riding (AOR = 1.96, 95% CI, 1.37–2.85), carrying adults while riding (AOR = 1.68, 95% CI, 1.23–2.28), riding in the motor lane (AOR = 2.42, 95% CI, 1.05–3.93), and riding in the wrong traffic direction (AOR = 1.63, 95% CI, 1.13–2.35). In over 77.58% of electric bike/moped-related road traffic crashes, riders were determined by the police to be responsible for the crash. Major crash-causing factors included violating traffic signals or signs, careless riding, speeding, and riding in the wrong lane.

Conclusion: Traffic safety related to electric bikes/moped is becoming more problematic with growing popularity compared with other 2-wheeled vehicles. Programs need to be developed to prevent electric bike/moped-related road traffic injuries in this emerging country.  相似文献   

9.
针对西北部分地区地表层粉砂分布不均、砂岩不易破碎、块石回填方量大、回填厚度深等问题,考虑特高压换流站工程地基处理的适用性及其成效、工期、造价等多方面因素,提出强夯地基处理方案。应用结果表明:该方法具有快速提高填土密实程度,加速填土前期固结,提高填土的物理力学性能,减少填土的后期沉降和建(构)筑物及地面设备基础的沉降等优点,可广泛应用于西北地区特高压换流站及其他大面积土石方开挖、回填及地基处理施工工程。  相似文献   
10.
为了研究不同好氧预处理方式对餐厨垃圾厌氧消化产甲烷的影响,通过建立3个模拟厌氧生物反应器,研究了传统厌氧生物反应器C1、上层好氧预处理-厌氧生物反应器C2和底部好氧预处理-厌氧生物反应器C3 3种不同操作条件下的产甲烷过程.结果表明,挥发性有机酸的累积使C1始终处于产甲烷滞后阶段;而C2、C3的好氧预处理通过加快易水解酸化组分和过量挥发性有机酸的好氧降解,有效缓解了酸性抑制,产甲烷滞后时间明显缩短至10 d内.第32天C2停止上层曝气后,在27 d内甲烷浓度达到了50%以上,同时,产甲烷速率迅速上升,并在第81天可达到峰值773 mL/(kg·d).C3在第11天停止底部曝气后,虽然经过22 d的时间甲烷浓度即上升至50%,但之后产甲烷速率经历回落阶段后再次逐渐上升,在实验结束时仅达到517 mL/(kg·d).上层曝气的好氧预处理方式所需曝气时间相对较长,但其产甲烷启动快,与底部曝气相比,其后期的甲烷化过程更稳定并可达到较高的产甲烷速率.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号