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   642篇
  免费   25篇
  国内免费   8篇
安全科学   40篇
废物处理   3篇
环保管理   114篇
综合类   184篇
基础理论   26篇
污染及防治   55篇
评价与监测   239篇
社会与环境   9篇
灾害及防治   5篇
  2023年   3篇
  2022年   12篇
  2021年   10篇
  2020年   27篇
  2019年   5篇
  2018年   2篇
  2017年   17篇
  2016年   14篇
  2015年   15篇
  2014年   32篇
  2013年   26篇
  2012年   26篇
  2011年   53篇
  2010年   24篇
  2009年   35篇
  2008年   43篇
  2007年   47篇
  2006年   31篇
  2005年   26篇
  2004年   23篇
  2003年   24篇
  2002年   14篇
  2001年   31篇
  2000年   23篇
  1999年   17篇
  1998年   20篇
  1997年   9篇
  1996年   13篇
  1995年   7篇
  1994年   6篇
  1993年   13篇
  1992年   7篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1987年   2篇
  1986年   2篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1977年   1篇
排序方式: 共有675条查询结果,搜索用时 296 毫秒
541.
汽车轮胎气压监测系统发展综述   总被引:13,自引:1,他引:13  
轮胎气压监测系统是汽车上一种新的主动安全技术产品,近年来,在国内外发展迅速。由于它能够实时监测汽车轮胎的气压和温度情况,并能及时给驾驶员以警告,因而可以最大限度地避免由爆胎引发的交通事故,提高了汽车的行车安全。综述了汽车轮胎气压监测系统的发展,包括间接式轮胎气压监测系统、直接式轮胎气压监测系统和下一代无电池轮胎气压监测系统(被动式TPMS)。介绍了各种汽车轮胎气压监测系统的结构组成和工作原理,分析比较了它们各自的优缺点。重点介绍了国外3种主流的直接式TPMS开发系统,对TPMS的研究、开发具有实用参考意义。展望了未来轮胎气压监测技术的发展趋势:无电池TPMS将取代现有类型,成为未来TPMS发展的主流。  相似文献   
542.
十二五"期间全国PM_(10)浓度陡增导致了达标城市比例降低,影响了《国家环境保护"十二五"规划》空气质量指标的完成。通过对PM_(10)浓度时间和空间变化分析,得出《环境空气质量标准》(GB3095-2012)的逐步实施对全国PM_(10)浓度的异常变化有着显著影响。新标准的发布施行,促进了PM_(10)监测仪器和方法更新升级,大幅收严了监测数据统计的有效性,提升了监测数据的质量控制水平,从主观和客观上更加有效的提高了监测数据的精度。  相似文献   
543.
The next stage in the process will be to obtain the views of as many people working in as many different fields as possible, to see whether the proposed scheme suits their needs and how it should be modified. With a few modifications, such a scheme could easily be appended to an existing land cover classification scheme, such as the FAO system, greatly increasing the usefulness and accessability of the results of the landcover classification.  相似文献   
544.
于2005年8月25日至8月28日对太湖进行现场监测,得到了太湖梅梁湾到大太湖的悬浮物、浊度数据,分析得出:(1)光照强度较高时,对应于微囊藻峰值的出现,浊度在水深0.5m处出现最高值,光照强度较弱时,浊度的分布在垂直方向上趋于均匀;(2)悬浮物浓度与浊度具有较高的相关性,悬浮物浓度值可以用浊度的测定值换算得到;(3)河流流入、风浪条件和湖内藻类繁殖等影响着太湖悬浮物的垂直和纵向空间分布,出现梅梁湾到大太湖不同的悬浮物垂直和纵向分布。  相似文献   
545.
我国环境监测技术存在的问题及对策   总被引:7,自引:0,他引:7  
从监测结果的科学性、监测方法的系统性及应急技术的实用性角度,提出了目前我国环境监测技术存在的问题,指出应通过科学监测,反映真实的环境质量,研究有毒有害污染物的监测方法并使其标准化,加强突发污染事故的快速监测技术研究.  相似文献   
546.
Protected areas present a global heritage. Assessing conservation achievements in protected areas is of crucial importance with respect to the on-time delivery of international biodiversity conservation targets. However, monitoring data from publicly accessible databases for comparative studies of conservation achievements in the protected areas of the world are very scarce, if not non-existent. At first glance this is surprising because, with regards to protected areas, at least according to well established protected area management guidelines and widely accepted public mandates, a great deal of monitoring work and data gathering is to be conducted. This would imply that data on changes of biodiversity in protected areas could be expected to exist, and the constant progress in information technologies and Web tools engenders hope that some of it might even be available online for the global public. This review article presents the results of an extensive online search and review of existing monitoring data from freely accessible online databases for its use in an assessment of conservation achievements in a larger sample of protected areas. Results show two contrary sides to the status quo of accessible data from the World Wide Web for conservation science: data overkill and data scarcity with poor metadata provision. While ever more research is, in fact, based on open-access online data, such as extrapolations of species ranges used in conservation management and planning, it remains almost impossible to obtain a basic set of information for an assessment of conservation achievements within a larger number of protected areas. This awareness has triggered a detailed discussion about the discrepancies in sharing data at the level of protected areas; mismatching relationships between expected activities in protected areas and the capacity for delivering these requirements are certainly among the main challenges. In addition, the fear of data misuse potentially resulting in harm for nature, careers, and competencies still seems to be a critical barrier strictly controlling the willingness to share data. Various initiatives aimed at tackling technical and cultural obstacles are introduced and discussed to reach the goal of a modern resource management based on adaptive management using digital opportunities of the new millennium for a sustainable global village.  相似文献   
547.
The diamondback terrapin’s (Malaclemys terrapin) wide geographic distribution, long life span, occurrence in a variety of habitats within the saltmarsh ecosystem, predatory foraging behavior, and high site fidelity make it a useful indicator species for contaminant monitoring in estuarine ecosystems. In this study fat biopsies and plasma samples were collected from males and females from two sites within Barnegat Bay, New Jersey, as well as tissues from a gravid female and blue mussels (Mytilus edulis), which are terrapin prey. Samples were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, and methyl-triclosan. Terrapins from the northern site, Spizzle Creek, closest to influences from industrial areas, had higher POP concentrations for both tissues than terrapins from the less impacted Forsythe National Wildlife Refuge. Sex differences were observed with males having higher contaminant concentrations in fat and females in plasma. PCB patterns in terrapin fat and plasma were comparable to other wildlife. An atypical PBDE pattern was observed, dominated by PBDEs 153 and 100 instead of PBDEs 47 and 99, which has been documented in only a few other turtle species. The typical PBDE patterns measured in mussels, terrapin prey, suggests that the terrapin may efficiently biotransform or eliminate PBDE 47 and possibly PBDE 99. Plasma contaminant concentrations significantly and positively correlated with those in fat. This study addresses several aspects of using the terrapin as an indicator species for POP monitoring: site and sex differences, tissue sampling choices, maternal transfer, and biomagnification.  相似文献   
548.
Recent developments in scanning electron microscopy (SEM) have produced tabletop instruments capable of reasonable imaging resolution at less cost compared to conventional equipment. Combining the SEM with energy dispersive spectroscopy (EDS) allows the possibility of elemental analysis through detection of X-rays emitted from interaction between individual particles and the SEM electron beam, revealing their atomic composition. It’s well known that exposure to inhalable particulate matter (PM) poses health risks and routine monitoring of the chemical content of these has been realized. Exposure information is of a general character but by combining the chemical build-up of monitored particles and knowledge of their inherent health effects will allow better risk assessment. An analysis technique using a tabletop SEM with EDS is demonstrated on particles collected onto nucleopore filters from urban, industrial and rural areas. Detailed characterization of the instruments analysis capabilities as applied to PM are described.  相似文献   
549.
Measurements of ground-level ozone concentrations and meteorology (temperature, vapour pressure deficit (VPD), solar radiation) at the monitoring site Ostad (south-west Sweden) were compared to data from the corresponding grid in the EMEP photo-oxidant model for 1997, 1999 and 2000. The influence of synoptic weather on the agreement between model and measurements was studied. Implications of differences between modelled and observed inputs for ozone flux calculations for wheat and potato were investigated. The EMEP model output of ozone, temperature and VPD correlated well with measurements during daytime. Deviations were larger during the night, especially in calm conditions, attributed to local climatological conditions at the monitoring site deviating from average conditions of the grid. These differences did not lead to significant differences in calculated ozone uptake, which was reproduced remarkably well. The uptake calculations were sensitive to errors in the ozone and temperature input data, especially when including a flux threshold.  相似文献   
550.
电除尘器是火电厂重要环保设备,其运行的稳定性和参数合理性直接影响粉尘排放浓度。针对上述问题,详述利用ARM微处理器和GPRS网络相结合,开发电除尘器高频电源智能监测系统设备,在远距离处可以获得现场的实时数据,实现对高频电源远程监控和诊断。  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