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1.
徐红  刘飚 《干旱环境监测》1991,5(4):208-209,213
本文对某铀矿职业工人和非职业工人头发中的总β、总α放射性水平和铀、钍含量进行了分析测定.结果表明,该矿工人体内铀和钍的蓄积量均在正常放射性本底水平范围内,从头发中检验未观察到工人体内铀、钍放射性水平有明显的升高.  相似文献   
2.
    
The intimate contact of components in a heterojunction photocatalyst is essential in determining the photocatalytic performance. To build a face-to-face interface in a 2D–2D heterojunction is an effective strategy to improve the charge carrier separation and utilization efficiency. In this work, the fabrication of a Step-scheme heterojunction on thin titania (TiO2) nanosheets with few-layered MoO3 structures is reported. With a decoration of a low dose of MoO3 layer by ball milling method, TiO2 (B) shows a three-fold increase in the hydrogen evolution rate. The reaction mechanism and driving force of charge transfer in the S-scheme heterojunction photocatalyst are investigated and discussed. Such 2D-2D heterojunction improves photocatalytic reaction rate because photogenerated electrons and holes at the interface can be quickly transferred to the surface. In situ XPS and PL demonstrates that the presence of MoO3 promotes the electron-hole pair separation via the Step-scheme heterojunction. Temperature programmed desorption of hydrogen shows that the heterojunction structure facilitates the desorption of hydrogen molecules. The approach used in this work to fabricate 2D–2D assembled structure thus improve the photocatalytic activity can be applied to other 2D metal oxides and sulfides, among others.  相似文献   
3.
针对游乐设施行业危险源、损伤、失效和故障四个概念的认知差异,通过研究相关领域这四个概念定义内涵及外延,结合游乐设施安全保障要求高、人-机-环交互频繁、运行工况复杂的特点,重新定义游乐设施这四个概念,辨析相互之间的逻辑关系,并结合游乐设施事故案例进行解析.结果表明:新定义对游乐设施危险源、失效、损伤和故障之间的关系阐述更加清晰准确,为后续的风险评价奠定良好基础.  相似文献   
4.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants that are toxic to human and nonhuman organisms. Dietary intake of PAHs is a dominant route of exposure for the general population because food crops are a major source of dietary PAHs. The mechanism for crop root uptake of PAHs remains unclear. Here we reveal that wheat root uptake of PAHs involves active and passive processes. The passive uptake is mercury and glycerol dependent. Mercury and glycerol inhibit uptake, indicating that aquaglyceroporins sensitive to mercury contribute to passive uptake. Active uptake is mediated by a phenanthrene/H symporter. The electrical response of wheat roots triggered by phenanthrene consists of two sequential phases: depolarization followed by repolarization. The depolarization is phenanthrene concentration dependent, with saturation kinetics that have an apparent of K(m) 10.8 μmol L(-1). As uptake proceeds, external solution pH increase is noticed. Lower pH favors the uptake. Vanadate and 2,4-dinitrophenol suppress the electrical response to phenanthrene and phenanthrene uptake, suggesting that plasma membrane H(+)-ATPase is involved in the establishment of an electrochemical proton gradient acting as a driving force for active uptake. Therefore, it is suggested that aquaglyceroporin and phenanthrene/H symporter are implicated in phenanthrene uptake. Our results provide insight into PAH uptake mechanism in wheat roots that is relevant to strategies for reducing PAH accumulation in wheat for food safety, improving phytoremediation of PAH-contaminated soils or water by agronomic practices and genetic modification to target remedial plants for higher PAH uptake capacity.  相似文献   
5.
Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland-to-cropland conversion on nitrate-nitrogen (NO3-N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO3-N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed-scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20 PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (Bromus L.) cover for at least 10 yr. Nonperennial areas were maintained under a no-till 2-yr corn (Zea mays L.)--soybean [Glycine max. (L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO3-N concentration from 2005 to 2008. The results indicated significant increases in NO3-N concentration in soil and groundwater following grassland-to-cropland conversion. Nitrate-nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long-term monitoring is needed to observe and understand the full response to land-use conversion.  相似文献   
6.
针对我国钛白粉工业发展的现状与存在的问题,深入分析造成钛白粉上业现状的原因,并从环保角度提出对策与建议.  相似文献   
7.
    
Based on stakeholder theory, this research aims to examine the effects of the two dimensions of corporate environmental responsibility (CER), which are CER strength and CER concern, on firm innovation performance, and the moderating effect of firm visibility on these relationships. Using data on Chinese firms listed on Shenzhen stock exchange from 2006 to 2015, this research finds that CER strength positively affects firm innovation performance while CER concern negatively affects innovation performance. These relationships are stronger for firms with greater visibility. This research provides insights for understanding the relationship between CER and innovation performance and has important managerial implications for firms to manage their environmental behaviors and improve innovation performance to achieve sustainable development.  相似文献   
8.
给水管壁生物膜会吸附水中的重金属元素积累在管壁生物膜中,在受到扰动时释放回到水体,危害饮用水水质安全。试验以上海管网末梢水为实验对象,研究了PVC、铸铁和紫铜等三种管材上生物膜对铅、镉的解吸特性。结果表明,PVC、铸铁和紫铜附着生物膜对铅的解吸容量qe分别为:5.92211μmol·m^-2、128.3051μmol·m^-2和21.1808,解吸速率常数k分别为:0.001060 m^2·μmol^-1·min^-1、0.000041 m^2·μmol^-1·min^-1和0.000503 m^2·μmol^-1·min^-1,对于镉元素三种材质的解吸容量qe分别为:14.71519μmol·m^-2、18.50481μmol·m^-2和2.25225μmol·m^-2;解吸速率常数k分别为:0.000102 m^2·μmol^-1·min^-1、0.001070 m^2·μmol^-1·min^-1和0.000103 m^2·μmol^-1·min^-1。  相似文献   
9.
论国有大中型企业的安全管理   总被引:2,自引:0,他引:2  
指出了国有大中型企业安全管理的特殊性:从内部看,部分国有大中型企业政治化严重,安全生产的责任主体空缺,事故隐患整改不及时,安全管理手段单一,安全技术人才、设备不能被充分利用;从外部看,政府部门对国有大中型企业直接干预较多,政出多门,地方保护主义,监察不到位,责任追究不严.国有大中型企业应建立自我管理机制,积极与国际接轨,建设企业安全文化,建立现代安全管理体系;政府应为企业建立可预期的法治环境,赋予大中型企业安全技术检测检验、培训教育、评估评价组织一定的职能,充分利用企业安全技术人才、设备资源,为安全生产服务.  相似文献   
10.
高层建筑火灾人员疏散和人员伤亡的模拟   总被引:4,自引:0,他引:4  
基于建筑火灾全风网网络模型的基础上,结合紧急疏散模型,模拟火灾时期疏散时间和建筑物内人员滞留的情况,同时也可以模拟可能出现的伤亡情况,有助于高层建筑的疏散系统设计,为火灾的再现提供了一个有效的分析工具,也为高层建筑火灾的风险评价提供了理论数据.  相似文献   
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