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   1174篇
  免费   89篇
  国内免费   222篇
安全科学   90篇
废物处理   78篇
环保管理   107篇
综合类   516篇
基础理论   217篇
环境理论   1篇
污染及防治   302篇
评价与监测   88篇
社会与环境   52篇
灾害及防治   34篇
  2024年   3篇
  2023年   24篇
  2022年   73篇
  2021年   73篇
  2020年   63篇
  2019年   60篇
  2018年   46篇
  2017年   70篇
  2016年   59篇
  2015年   75篇
  2014年   69篇
  2013年   108篇
  2012年   83篇
  2011年   89篇
  2010年   69篇
  2009年   78篇
  2008年   64篇
  2007年   54篇
  2006年   56篇
  2005年   49篇
  2004年   48篇
  2003年   40篇
  2002年   36篇
  2001年   15篇
  2000年   10篇
  1999年   8篇
  1998年   7篇
  1997年   4篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   6篇
  1992年   4篇
  1991年   5篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1986年   4篇
  1985年   3篇
  1981年   2篇
  1972年   1篇
  1971年   1篇
  1967年   1篇
  1966年   1篇
  1964年   1篇
  1962年   1篇
  1960年   1篇
  1958年   2篇
排序方式: 共有1485条查询结果,搜索用时 62 毫秒
891.
煤矿企业安全风险集成管理系统及其ANP测评模型研究   总被引:1,自引:0,他引:1  
为了帮助煤矿企业科学地评价其安全风险集成管理水平和不断提高安全风险管理能力,通过采用问卷调查、实地走访和理论演绎等方法,提出以全过程、全要素和全员安全风险管理为目标,风险管理为过程,组织保障、管理机制、管理方法、资源投入、人员能力和安全文化为要素的煤矿安全风险集成管理系统,并基于网络分析法(ANP)建立煤矿企业安全风险集成管理水平测评模型,同时结合对某煤矿集团的相关问卷调查数据,对该测评模型的有效性和合理性进行检验。  相似文献   
892.
High energy prices and the growing concern for “Peak Oil” have put energy analysis, once again, on the front burner. However, before speculating about possible roadmaps regarding our energy future, it would be wise to develop better quantitative analyses. This paper flags the existence of systemic epistemological flaws in the current use of aggregate energy indicators and presents an alternative approach capable of dealing with the issue of multiple dimensions and multiple scales. Starting from a critical appraisal of the aggregate indicator “Economic Energy Intensity” it shows that economic and biophysical variables are often correlated and that their value is determined by characteristics which can only observed across different levels and scales. Complex metabolic systems (systems that use energy to maintain and reproduce themselves) are operating simultaneously at different scales. This implies that changes in the characteristics of parts, defined at the local scale, and changes in the characteristics of the whole, defined at the large scale can only be obtained after establishing a scaling mechanism in the analysis. In order to deal with the issue of scale in energy accounting, we propose to make a distinction between three different categories: (i) primary energy sources (PES) - establishing a link between energy quantities and the associated requirement of biophysical gradients, at the large scale, on the interface black-box/context; (ii) energy carriers (EC) - defining the set of energy inputs required by technical devices for expressing useful functions, at the local scale, within the parts operating inside the black-box; (iii) end uses (EU) the set of functions to be expressed by society across hierarchical levels for reproducing itself. Finally, the paper presents examples of quantitative results obtained using an innovative method of analysis - Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM). We conclude that by using this new accounting method it is possible to generate a better understanding of external and internal constraints determining the desirability and viability of the metabolic pattern of societies.  相似文献   
893.
微塑料既是一种新兴污染物,还能作为载体吸附污染物,对河流等生态系统构成了威胁.但目前针对我国北方河流中微塑料污染问题的研究鲜见.基于对北京市通州区内6条河流共19个点位的水样采集和分析,研究了微塑料的组成及空间分布特征,并揭示了微塑料的潜在来源.结果表明,微塑料在所有点位上的检出率为100%,其中小中河中微塑料的平均丰度是所有河流中最高的(3.50×104 n·m-3),是运潮减河中平均丰度的4.04倍.粒径上,90.49%微塑料的粒径小于2 000μm,且仅在2个点位上监测到了粒径大于4 000μm的微塑料.微塑料呈现出纤维状、薄膜状、碎片状和颗粒状等4种形态,其中纤维状的微塑料占比最高(90.23%).微塑料以透明色和蓝色为主,共占比84.29%.人造丝的占比最高,且在各点位上的占比都在66.67%以上,而其他成分微塑料的分布在不同点位上存在较大的差异.无论是微塑料丰度还是成分种类,河流上游均高于下游.根据微塑料的形状、成分、颜色和丰度的空间特征,解析了不同类型微塑料的来源.对于河流中占比最高的纤维状微塑料,其主要来源可能为服装洗涤、渔具...  相似文献   
894.
针对采油管柱落井事故原因多且复杂的问题,基于FT与BCCT对采油管柱落井事故进行溯源分析。通过建立采油管柱落井事故树(FT)计算最小割集,绘制等效事故树;结合博德事故因果连锁理论(BCCT)确定直接原因、间接原因,在此基础上追溯其根本原因。结果表明:造成采油管柱落井事故的直接原因是油管挂断裂、油管断裂、修井队操作失误、卡瓦故障;间接原因是油管挂或新油管或丝扣或卡瓦质量差、油管挂或油管长期服役、修井频繁、操作不稳、解卡不当、起下钻操作不当、对扣作业不当、设备失灵、卡瓦磨损严重、卡瓦操作失误;根本原因是与管理相关的产品采购、校准、检验、试验过程管理不当,缺少寿命预测或设备更新改造不合理,人员的培训不足或考核不合格,未制定合理的设备检验维修计划。最后通过钻井现场实例分析,说明管理缺陷对采油管柱落井事故发生的影响。  相似文献   
895.
为了提升天然非金属矿物对Cd2+的吸附性能,采用MT(蒙脱石)和HP(海泡石)为前驱材料,依次通过酸纯化和SDS(十二烷基磺酸钠)改性后合成了有机非金属矿物材料,利用扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线荧光光谱分析(XRF)等手段对2种改性材料〔SDS-MT(十二烷基磺酸钠改性蒙脱石)和SDS-HP(十二烷基磺酸钠改性海泡石)〕吸附Cd2+的机制进行探究,并对吸附过程分别进行了动力学拟合和等温吸附方程拟合.结果表明:①SDS-MT和SDS-HP吸附模拟废水中Cd2+的效果分别比未改性的MT和HP平均提升约40%和19.5%. ②改性过程没有改变2种前驱材料的基本结构,但引起其元素质量分数、阳离子交换量和比表面积的改变. ③SDS-MT、SDS-HP对模拟废水中Cd2+的吸附量受溶液的pH影响较大,最大吸附量分别达16.54、9.24 mg/g,2种改性材料对模拟废水中Cd2+的吸附过程能较好地满足准二级动力学方程,并且其平衡传质时间较短. ④SDS-MT对模拟废水Cd2+的吸附模型较满足于Freundlich吸附等温模型,推测SDS-MT是一种有限吸附位点的吸附剂,吸附过程为单分子层吸附,而SDS-HP则较好的满足Langmuir吸附等温模型.研究显示,对2种天然非金属矿物材料的有机改性能够有效提升材料对Cd2+的吸附容量,发挥材料的实际运用价值.   相似文献   
896.
The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nanoscale edges can act as ‘nano-knives', which are able to cut the long chain of carboxymethyl cellulose(CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules(41,000 Da) were decomposed into a series of smaller molecules(460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution(2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared(FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional groupβ-1-4-glycosidic bond(wavenumber 1062 cm-1) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of β-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents.  相似文献   
897.
Environmental Science and Pollution Research - Radon exhalation from soil and ores is among the most dangerous risks for the public health care. The impact becomes even more powerful when...  相似文献   
898.
Environmental Science and Pollution Research - A large amount of fresh tobacco waste with high water content are produced in farmland, and it may cause environmental pollution if it is not properly...  相似文献   
899.
Environmental Science and Pollution Research - To control the dust pollution caused by open-pit coal mining and reduce or avoid the secondary hazards of existing dust suppressants to the...  相似文献   
900.

Copper oxide nanoparticles (CuO NPs) have received considerable attention for their toxic effects on crops and potential application in agriculture. In order to investigate the biological effects of CuO NPs on plants, we exposed cucumber (Cucumis sativus) to two sizes of CuO NPs (510 nm, μCuO and 43 nm, nCuO). Results indicated that with concentration increased, the available Cu content in soil increased significantly. The addition of CuO NPs increased Cu content and other nutrient element (e.g., K, P, Mn, and Zn) content in plants. However, diverse particle sizes had different effects. The nCuO treatment had larger translocation factor, higher nutrient element content in fruits, and lower oxidative damage than μCuO treatment. Moreover, nCuO of 100 mg/kg could stimulate cucumber growth, while μCuO had no obvious effects on growth. Conclusively, CuO NPs could be used as copper fertilizer to supply copper to cucumber. The nCuO had better effects on improving the bioavailability of Cu and nutritional value of fruits. These results can help develop strategies for safe disposal of CuO NPs as agricultural fertilizer.

  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