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   2974篇
  免费   422篇
  国内免费   1356篇
安全科学   582篇
废物处理   98篇
环保管理   333篇
综合类   2292篇
基础理论   479篇
污染及防治   502篇
评价与监测   72篇
社会与环境   196篇
灾害及防治   198篇
  2024年   37篇
  2023年   158篇
  2022年   232篇
  2021年   254篇
  2020年   210篇
  2019年   211篇
  2018年   127篇
  2017年   181篇
  2016年   202篇
  2015年   185篇
  2014年   194篇
  2013年   215篇
  2012年   301篇
  2011年   277篇
  2010年   203篇
  2009年   187篇
  2008年   159篇
  2007年   238篇
  2006年   222篇
  2005年   170篇
  2004年   124篇
  2003年   116篇
  2002年   102篇
  2001年   89篇
  2000年   78篇
  1999年   52篇
  1998年   52篇
  1997年   44篇
  1996年   37篇
  1995年   26篇
  1994年   16篇
  1993年   19篇
  1992年   12篇
  1991年   5篇
  1990年   5篇
  1989年   1篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1983年   2篇
  1981年   1篇
  1978年   1篇
排序方式: 共有4752条查询结果,搜索用时 15 毫秒
941.

在“放管服”改革背景下,规划环评与项目环评的联动实践,重在简化规划所包含项目的环评内容和程序,但过于重视效率,不利于环评制度风险预防功能的实现。现行法律法规和国家层面政策文件中相关规定较为原则,各地在实践探索中联动条件、联动范围、简化内容、审批方式等均存在较大差异,规范统一的联动机制尚未形成。对此,基于规划环评与项目环评联动机制的构建机理,针对现有实践存在的问题,以《中华人民共和国环境影响评价法》修改为契机,回归环评制度预防性规制的本质,明确联动机制的适用条件和范围,确定项目环评简化或强化的内容,回应环评审批改革实践可能存在的合法性质疑,建立自下而上的反馈和监督机制,从而为规划环评与项目环评联动机制提供法治化构建方案。

  相似文献   
942.

含铀废水中铀的回收主要是基于材料与[UO2(H2O)5]2+中UO2 2+之间的络合,但H2O的电偶极矩对络合有显著弱化作用。采用酰胺基两性分子N,N-二甲基-9-癸烯酰胺(NADA)氢键作用与[UO2(H2O)5]2+形成UO2[(H2O)xC12H23NO]n *x<5,UO2-Coordination Compound,简称UO2-CC),选取惰性物质WS2为吸附材料,通过静态吸附试验(不同pH、接触时间、浓度和温度)分别研究其对UO2 2+和UO2-CC的吸附量。动力学拟合结果表明,二者的吸附反应是化学吸附过程,UO2 2+经NADA重构后,吸附时间从240 min缩短至180 min,准二级动力学吸附常数提高1.35倍。等温吸附研究结果表明,WS2与UO2-CC络合过程符合Langmuir吸附等温模型,且NADA的加入使吸附由自发吸热过程转变为自发放热过程,吸附反应过程有序度增加。NADA原位重构[UO2(H2O)5]2+后,WS2对UO2 2+的平衡吸附量由45.03 mg/g(WS2/UO2 2+体系)提高到122.14 mg/g(WS2/UO2-CC体系)。采用光谱分析(X射线光电子能谱法)从分子水平深入研究NADA原位重构[UO2(H2O)5]2+后在WS2上的吸附机制,揭示静电、氢键和U—S共价键等作用力对吸附的贡献,特别是NADA的氢键作用。

  相似文献   
943.
生物质炭(biochar)是一种碳含量高、比表面积大、孔隙度高且吸附能力强的土壤改良与修复材料,可通过物理、化学和生物方式作用于土壤,但其影响和作用机制随土壤性质和生物质炭类型不同而异。从生物质炭组成、比表面积和孔隙度、酸碱度及表面官能团等特性与原料和制备工艺关系入手,结合土壤和生物质炭类型,综合阐述了生物质炭添加在改善土壤结构、提高土壤肥力、调节土壤酸碱度、修复污染土壤、增强生物活性和促进养分转化等方面的作用。发现生物质炭通过填充扩容、孔隙截留、胶结凝聚、物理吸附、化学吸附、离子交换、配位络合、共沉淀、微生物介导等方式作用于土壤,实现土壤改良和修复。从物理、化学和生物3方面分类阐述了生物质炭对土壤的影响和作用机制,同时提出未来可重点关注生物质炭改性与制备工艺、不同生物质炭混施比例及施用后的环境风险评估等方面。  相似文献   
944.

针对城镇化进程加快导致的珠三角地区生态景观胁迫程度日趋严峻,亟需加强区域生态保护的现状,构建新型城镇化与景观生态安全的耦合协调模型,定量测度2000—2020年珠三角地区城镇空间扩展与景观生态安全耦合协调时空格局以及发展状态,运用多元回归分析和灰色预测模型揭示其驱动机理,并预测2040年城镇空间扩展和景观生态安全耦合的发展趋势。结果表明:珠三角地区9市城镇化与景观生态安全的耦合协调度在20年间呈现缓慢波动上升的趋势,耦合协调度由2000年的0.305~0.436升至2020年的0.385~0.545,现处于拮抗耦合阶段,未来20年将继续向着协调同步、有序发展的方向前进。珠三角地区经济发展不平衡,城镇开发建设和生态环境保护难以同步发展,景观生态状况不乐观,生态环境滞后型的地市逐渐增多,尚未全面形成良好的协调发展状态。对外开放程度、经济发展水平、科技投入水平等因素对耦合协调度的影响较为显著(P<0.05),今后对于区域可持续发展需要加强耦合协调的机理研究,持续关注城镇空间拓展与景观生态安全的协调发展趋势及特征。

  相似文献   
945.
Because they cause burns that are difficult to heal, acids are dangerous, and steps should be taken to ensure that the human skin does not come into contact with them. For this purpose safety gloves are generally used by workers who have to handle acids. Such gloves need to be tested to ensure that they are acid resistant. Standard EN 374 (European Committee for Standardization [CEN], 1993c) specifies a method of testing the permeation of liquid chemicals, on a molecular level, through glove material, but it may be difficult to ensure the fitness of the joints of a two-compartment cell, when gloves are lined with jersey. To deal with this a simple pH-meter method to test the permeation of acid and alkali solutions through safety gloves has been developed. The permeation of H2S04, HCI, HN03, and CH3COOH through gloves made from neoprene, nitrile, and PVC was tested. This method seems to be simple and economical.  相似文献   
946.
In the '90's a membrane-associated transport protein, discovered in aquatic organisms, was considered to be expressed in response to environmental xenobiotics. Like the multidrug resistance protein found in mammalian tumor cell lines, this protein confers resistance in organisms in polluted areas by binding xenobiotics and transporting them out of the cells in an energy-dependent manner.This study investigates the expression and the activity of a P-glycoprotein (Pgp) involved in a multixenobiotic resistance mechanism (MXRW) during the early developmental stages and in tissues of adult Xenopus laevis.  相似文献   
947.
Abstract

In present study, we constructed the direct protein-protein interaction network of insecticide resistance based on subcellular localization analysis. Totally 177 of 528 resistance proteins were identified and they were located in 11 subcellular localizations. We further analyzed topological properties of the network and the biological characteristics of resistance proteins, such as k-core, neighborhood connectivity, instability index and aliphatic index. They can be used to predict the key proteins and potential mechanisms from macro-perspective. The problem of resistance has not been solved fundamentally, because the development of new insecticides can’t keep pace with the development speed of resistance, and the lack of understanding of molecular mechanism of resistance. As the further analysis to reduce data noise, we constructed the direct protein-protein interaction network of insecticide resistance based on subcellular localization analysis. The interaction between proteins located at the same subcellular location belongs to direct interactions, thus eliminating indirect interaction. Totally 177 of 528 resistance proteins were identified and they were located in 11 subcellular localizations. We further analyzed topological properties of the network and the biological characteristics of resistance proteins, such as k-core, neighborhood connectivity, instability index and aliphatic index. They can be used to predict the hub proteins and potential mechanisms from macro-perspective. This is the first study to explore the insecticide resistance molecular mechanism of Drosophila melanogaster based on subcellular localization analysis. It can provide the bioinformatics foundation for further understanding the mechanisms of insecticide resistance. It also provides a reference for the study of molecular mechanism of insecticide resistance of other insects.  相似文献   
948.
• Sub-inhibitory levels of nC60 promote conjugative transfer of ARGs. • nC60 can induce ROS generation, oxidative stress and SOS response. • nC60 can increase cell membrane permeability and alter gene expression. • Results provide evidence of nC60 promoting antibiotic resistance dissemination. The spread and development of antibiotic resistance globally have led to severe public health problems. It has been shown that some non-antibiotic substances can also promote the diffusion and spread of antibiotic resistance genes (ARGs). Nanofullerene (nC60) is a type of nanomaterial widely used around the world, and some studies have discovered both the biological toxicity and environmental toxicity of nC60. In this study, cellular and molecular biology techniques were employed to investigate the influences of nC60 at sub-minimum inhibitory concentrations (sub-MICs) on the conjugation of ARGs between the E. coli strains. Compared with the control group, nC60 significantly increased the conjugation rates of ARGs by 1.32‒10.82 folds within the concentration range of 7.03‒1800 mg/L. This study further explored the mechanism of this phenomenon, finding that sub-MICs of nC60 could induce the production of reactive oxygen species (ROS), trigger SOS-response and oxidative stress, affect the expression of outer membrane proteins (OMPs) genes, increase membrane permeability, and thus promote the occurrence of conjugation. This research enriches our understanding of the environmental toxicity of nC60, raises our risk awareness toward nC60, and may promote the more rational employment of nC60 materials.  相似文献   
949.
In this paper, the kinetic mechanism of AIBN, AMBN, and ABVN was proposed, and the effect of molecular structure on their thermal hazards based on the kinetic mechanism was investigated. Calculated by non-isothermal DSC datum, the kinetic mechanism of AIBN, AMBN, and ABVN is revealed by the linear relationship between the integrated form of mechanical function and reaction time. The results indicate that the thermal decomposition process is controlled by the Johnson-Mehl-Avrami equation. Based on the determination of kinetic mechanism function, the reaction rate constants at various heating rates are directly calculated, and the intercept of the best fitting straight line of reaction rate constants with heating rate is approximately equal to the reaction rate constant under isothermal conditions. Besides, theoretical values obtained by multiplying kinetic mechanism function by reaction rate are well consistent with the experimental values, suggesting that the kinetic mechanism obtained is credible. Bond Dissociation Energies (BDE) calculated by quantum chemical equations are employed to evaluate the thermodynamics stability of AIBN, AMBN, and ABVN. Depending on similar molecular structures, the influence of differentiated group structure on the thermodynamic stability represented by BDE and heat release and the kinetic stability characterized by reaction rate constant were revealed. Finally, the results demonstrate that the thermal hazard increases as the volume of substituent group and molecular weight.  相似文献   
950.
本文简要论述了良好的决策机制是公众参与环境决策的基本保障,分析了当前我国公众参与环境决策运行机制存在的不足,并提出了优化其运行机制的一些思路。  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