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   1154篇
  免费   88篇
  国内免费   224篇
安全科学   264篇
废物处理   4篇
环保管理   96篇
综合类   503篇
基础理论   310篇
环境理论   1篇
污染及防治   60篇
评价与监测   42篇
社会与环境   138篇
灾害及防治   48篇
  2024年   6篇
  2023年   22篇
  2022年   44篇
  2021年   61篇
  2020年   52篇
  2019年   47篇
  2018年   46篇
  2017年   52篇
  2016年   57篇
  2015年   64篇
  2014年   58篇
  2013年   130篇
  2012年   69篇
  2011年   83篇
  2010年   69篇
  2009年   58篇
  2008年   52篇
  2007年   72篇
  2006年   67篇
  2005年   53篇
  2004年   45篇
  2003年   38篇
  2002年   35篇
  2001年   34篇
  2000年   24篇
  1999年   30篇
  1998年   16篇
  1997年   12篇
  1996年   5篇
  1995年   18篇
  1994年   18篇
  1993年   2篇
  1992年   2篇
  1990年   8篇
  1989年   7篇
  1988年   1篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1980年   1篇
  1979年   1篇
  1973年   1篇
排序方式: 共有1466条查询结果,搜索用时 31 毫秒
991.
井喷是海上钻井平台的重要威胁,而人因失误又是造成井喷的主要原因,所以对井喷事故人因失误分析对指导海上钻井安全有重要意义。本文建立了井喷事故人因失误类故障树模型,并对此进行定量分析。根据井喷事故的4个指标并结合风险图得到降低风险所需的置信水平,然后使用训练屏障和 GPS 定位屏障将风险降低到可接受水平。最后通过蝴蝶结模型将安全屏障对风险的影响清楚的展示出来,为人因失误的预防和控制提供指导。  相似文献   
992.
The human dimensions of visibility degradation remain under-researched academically. Based on Zube and Sell's Process Model of the Perception of, and Response to, Environmental Change, a questionnaire survey was conducted in Hong Kong between 5 June 2012 and 26 January 2013 (n = 1,203). The respondents’ perceptions towards visibility degradation were collected. The results show that respondents were moderately knowledgeable to visibility degradation, perceiving the problem as anthropogenic and unfavorable and identifying the fight against the degradation as an important environmental issue. It is further deduced that the respondents’ physical and sociocultural attributes, and the way they gain information about visibility degradation, can affect their perceptions of visibility degradation. The results reveal that improving information channels can positively promote human sensitivity to and understanding of visibility degradation in order to mitigate it. Yet, any attempts to educate the lay public should not assume the existence of a homogenous community of like-minded people.  相似文献   
993.
Despite the high profile of amphibian declines and the increasing threat of drought and fragmentation to aquatic ecosystems, few studies have examined long‐term rates of change for a single species across a large geographic area. We analyzed growth in annual egg‐mass counts of the Columbia spotted frog (Rana luteiventris) across the northwestern United States, an area encompassing 3 genetic clades. On the basis of data collected by multiple partners from 98 water bodies between 1991 and 2011, we used state‐space and linear‐regression models to measure effects of patch characteristics, frequency of summer drought, and wetland restoration on population growth. Abundance increased in the 2 clades with greatest decline history, but declined where populations are considered most secure. Population growth was negatively associated with temporary hydroperiods and landscape modification (measured by the human footprint index), but was similar in modified and natural water bodies. The effect of drought was mediated by the size of the water body: populations in large water bodies maintained positive growth despite drought, whereas drought magnified declines in small water bodies. Rapid growth in restored wetlands in areas of historical population declines provided strong evidence of successful management. Our results highlight the importance of maintaining large areas of habitat and underscore the greater vulnerability of small areas of habitat to environmental stochasticity. Similar long‐term growth rates in modified and natural water bodies and rapid, positive responses to restoration suggest pond construction and other forms of management can effectively increase population growth. These tools are likely to become increasingly important to mitigate effects of increased drought expected from global climate change. Papeles de las Características del Fragmento, Frecuencia de Sequía y Restauración en las Tendencias a Largo Plazo de un Anfibio Ampliamente Distribuido  相似文献   
994.
Bioassay using cultured human cell lines was applied to an effluent of a wastewater treatment plant (WWTP) in Sapporo to assess their toxicity, and in order to investigate the fate of toxicity in the WWTP, bioassay of the water samples from several points in WWTP (influent, effluent, return flow from thickener, from dewatering process and from incineration process) was performed. We also applied bioassay to the mixture of the activated sludge from the investigated plant and artificial sewage. These results showed that the toxicity of the effluent was more intensive than the influent, and organic matter released from activated sludge bacteria during their decay process contributed to the increase of toxicity in the effluent.  相似文献   
995.
人类健康风险的定量评估与分析   总被引:1,自引:0,他引:1  
通过深入研究.将人类健康风险解析环境污染、食物安全、疾病流行和医疗保障四个方面。在建立一套评价人类健康风险指标体系的基础上。对40个样本国家进行评估。用聚类分析的方法.将40个国家分为四类,在对每一类国家的人类健康风险特点进行对比发现,在同等经济发展水平下,中国的人类健康风险相对较高。通过分析人类健康风险与经济发展水平的关系得出,人均GNI 1000,3000美元是国家经济发展的关键时期。同样也是改善人类健康状况的关键时期,这一时期国家要高度重视改善人类健康状况。  相似文献   
996.
Goal, Scope and Background Cadavers for gross anatomy laboratories are usually prepared by using embalming fluid which contains formaldehyde (FA) as a principal component. During the process of dissection, FA vapors are emitted from the cadavers, resulting in the exposure of medical students and their instructors to elevated levels of FA in the laboratory. The American Conference of Governmental Industrial Hygienists (ACGIH) has set a ceiling limit for FA at 0.3 ppm. In Japan, the Ministry of Health, Labour and Welfare has set an air quality guideline defining two limit values for environmental exposure to FA: 0.08 ppm as an average for general workplaces and 0.25 ppm for specific workplaces such as an FA factory. Although there are many reports on indoor FA concentrations in gross anatomy laboratories, only a few reports have described personal FA exposure levels. The purpose of the present study was to clarify personal exposure levels as well as indoor FA concentrations in our laboratory in order to investigate the relationship between them. Methods The gross anatomy laboratory was evaluated in the 4th, 10th and 18th sessions of 20 laboratory sessions in total over a period of 10 weeks. Air samples were collected using a diffusive sampling device for organic carbonyl compounds. Area samples were taken in the center and four corners of the laboratory during the entire time of each session (4-6 hours). Personal samples were collected from instructors and students using a sampling device pinned on each person's lapel, and they were 1.1 to 6 hours in duration. Analysis was carried out using high performance liquid chromatography. Results and Discussion Room averages of FA concentrations were 0.45, 0.38 and 0.68 ppm for the 4th, 10th and 18th sessions, respectively, ranging from 0.23 to 1.03 ppm. These levels were comparable to or relatively lower than the levels reported previously, but were still higher than the guideline limit for specific workplaces in Japan and the ACGIH ceiling limit. The indoor FA concentrations varied depending on the contents of laboratory sessions and seemed to increase when body cavity or deep structures were being dissected. In all sessions but the 4th, FA levels at the center of the room were higher than those in the corners. This might be related to the arrangement of air supply diffusers and return grills. However, it cannot be ruled out that FA levels in the corners were lowered by leakage of FA through the doors and windows. Average personal exposure levels were 0.80, 0.45 and 0.51 ppm for instructors and 1.02, 1.08 and 0.89 ppm for students for the 4th, 10th and 18th session, respectively. The exposure levels of students were significantly higher than the mean indoor FA concentrations in the 4th and 10th sessions, and the same tendency was also observed in the 18th session. The personal exposure level of instructors was also significantly higher than the indoor FA level in the 4th session, while they were almost the same in the 10th and 18th sessions. Differences in behavior during the sessions might reflect the differential personal exposure levels between students and instructors. Conclusion The present study revealed that, if a person is close to the cadavers during the gross anatomy laboratory, his/her personal exposure level is possibly 2 to 3-fold higher than the mean indoor FA concentration. This should be considered in the risk assessment of FA in gross anatomy laboratories. Recommendation and Outlook If the risk of FA in gross anatomy laboratories is assessed based on the indoor FA levels, the possibility that personal exposure levels are 2 to 3-fold higher than the mean indoor FA level should be taken into account. Otherwise, the risk should be assessed based on the personal exposure levels. However, it is hard to measure everyone's exposure level. Therefore, further studies are necessary to develop a method of personal exposure assessment from the indoor FA concentration.  相似文献   
997.
超市火灾烟气蔓延及人员疏散的模拟研究   总被引:3,自引:0,他引:3  
针对某大型超市的实际建筑结构以及人员分布情况,利用计算机模拟设定了几种不同情况下的火灾场景,研究了火灾情况下影响人员疏散的因素,并根据烟气运动和人员疏散模拟的结果,对该超市人员疏散楼梯的数量、宽度以及位置分布进行评估.指出了实际超市火灾过程中人员疏散应该注意的一些问题,给出了合理的防火分区划分以及疏散楼梯的分配方式,对超市建筑人员疏散具有一定的指导意义.  相似文献   
998.
伤亡赔偿标准由于人的年龄、经历、工作等的不同而不同。本文参考国内外相关资料后,在人人平等的基础上区分了不同人的生命价值,设计的估算方法基本包含了各个年龄段的人的生命价值。估算结果仅适用于事故和不可抗力造成的伤亡情况,不适用于故意伤害谋杀等犯罪活动造成的伤亡。生命价值没有上限只有下限,使生命经济价值的估算值有较大提高,这对提高伤亡赔偿标准,对提高人们对生命价值的认识都有一定的价值。  相似文献   
999.
社会保障制度和人力资本投资的关系是近年来劳动经济学中新出现的一个课题,相关研究尚不多见。以我国养老保险的“统帐结合”模式为例,分析了社会保障对人力资本投资的影响,同时结合我国劳动力市场现状,对劳动力市场分割状态下“统帐结合”模式与人力资本投资的关系进行了分析。结果表明,增加“统帐结合”模式中个人账户的比例,将激励个人进行较多的人力资本投资,但劳动力市场分割的存在削弱了这种激励作用。因此,建议:适当增加“统帐结合”模式中个人承担的比例;建立覆盖全国的社会保障体系;加快劳动力市场建设。逐步消除劳动力市场分割状态,促进全国统一的、自由竞争的劳动力市场的形成。  相似文献   
1000.
Abstract

Based on the flood affected area (FA) data of the provinces in China from 1950 to 2005, the article discusses the change of the flood patterns in China, and investigates its relationship with climate change and human activities. The flood center shifted from North China and the Yangtze–Huaihe basin in the 1950s towards the south, north and west of China, and located in the south of the Yangtze River and South China after the 1990s. The FA in the western provinces was continuously on the rise since the 1950s. There are two characteristics for the future flood pattern in China. The pattern of “flood in the south and drought in the north” depends on the north–south shift of the maximum rainfall region in eastern China. The flood intensification to the west of Hu Huanyong’s line mainly results from the increase of rainfall, extreme precipitation and the melting of glaciers under the background of human activity magnification.  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