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   17091篇
  免费   1085篇
  国内免费   2185篇
安全科学   2445篇
废物处理   256篇
环保管理   3101篇
综合类   8470篇
基础理论   1760篇
环境理论   11篇
污染及防治   928篇
评价与监测   904篇
社会与环境   1450篇
灾害及防治   1036篇
  2024年   41篇
  2023年   162篇
  2022年   334篇
  2021年   446篇
  2020年   428篇
  2019年   368篇
  2018年   338篇
  2017年   462篇
  2016年   558篇
  2015年   602篇
  2014年   641篇
  2013年   822篇
  2012年   1056篇
  2011年   1207篇
  2010年   888篇
  2009年   878篇
  2008年   746篇
  2007年   1078篇
  2006年   1109篇
  2005年   888篇
  2004年   773篇
  2003年   906篇
  2002年   825篇
  2001年   703篇
  2000年   673篇
  1999年   628篇
  1998年   484篇
  1997年   383篇
  1996年   453篇
  1995年   284篇
  1994年   248篇
  1993年   205篇
  1992年   157篇
  1991年   120篇
  1990年   80篇
  1989年   51篇
  1988年   44篇
  1987年   20篇
  1986年   20篇
  1985年   37篇
  1984年   48篇
  1983年   50篇
  1982年   14篇
  1981年   12篇
  1980年   14篇
  1979年   11篇
  1978年   9篇
  1977年   12篇
  1973年   9篇
  1971年   18篇
排序方式: 共有10000条查询结果,搜索用时 195 毫秒
521.
液化石油气储罐火灾爆炸事故分析   总被引:3,自引:0,他引:3  
周浩  杨光  尹达  雷孝平 《交通环保》2001,22(3):15-17
应用基于可能性分布的模糊事故树分析法,对引发液化石油气储罐发生火灾爆炸事故的可能因素进行了定量分析。  相似文献   
522.
音乐教育对每个人的素质培养具有重要作用,但长久以来音乐教育都不被学校、学生所重视,在我国高校的音乐教育才刚刚起步。作者根据自身多年的高校音乐教学经验,认为高校的音乐教育关键是编订独具特色的音乐教材、开启学生的兴趣之门、施行兼收并蓄的教学方法。  相似文献   
523.
An analysis is presented of the environmental effects of the most serious radiation accident recorded after Chernobyl, which occurred in the formerly secret town of Tomsk-7 in Siberia, Russia, on 6, April 1993. Fortunately, it appears not to have become a major industrial crisis or disaster. The causes of the accident are described. It is argued that a mixture of both objective and subjective prerequisites, including specific human, organizational, and technological factors, were responsible for the explosion or directly facilitated it. The Tomsk-7 accident's ecological, medical, social, and psychological consequences are discussed.  相似文献   
524.
Biodegradable polyesters were synthesized by ring-opening copolymerization of -butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.1H and13C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×104. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT m andT g values of the copolymers showed a gradual depression with an increase in BL content. NoT m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of -methyl--butyrolactone (MBL) or -ethyl--butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.  相似文献   
525.
/ The valleys of European piedmonts constitute changing narrow corridors within which water, matter, nutrients, energy, and species flow. The dispersion patterns of these flows have been significantly disturbed since the end of the 18th century. Thus, western European valleys have been changed into complex mosaics by implementation of socioeconomical programs. In order to define future actions allowing the preservation of this "ecocomplex" (Blandin and Lamotte 1988), it is necessary to gather precise information of the landscape dynamics. Hence, the study of the European river valleys must be based upon two major steps: (1)the analysis of the present landscape with suitable remote sensing techniques, allowing us to map the complex mosaic of narrow corridors; and (2) the analysis of temporal landscape development patterns since the first engineering works that have transformed the braided channel system. In this paper, the efficiency of the addition of two techniques is highlighted: (1) the "wavelet merging method" from multispectral and panchromatic SPOT images for the floodplain land-cover mapping, and (2) the historical reconstruction techniques from old maps and archive documents in order to analyze the cumulative impacts of engineering works on landscape diversity. To illustrate the method, a particularly complex case study is chosen: the Arc/Isere confluence (downstream from Albertville, Savoie, France). Remote sensing, field survey, and historical reconstruction allowed us to distinguish two types of spatial units: (1) the "functional sets" characterized by independent state factors (edaphic, hydrological, and topographic) and supporting a limited number of vegetation types (spontaneous or cultivated), and (2) the functional unit (= ecotope), which corresponds to a unique combination of vegetation type/functional set.KEY WORDS: Landscape ecology; Floodplains; Vegetation; Land use; Remote sensing; Historical reconstruction; Mapping; Merging methods; Human impacts; Alps; Isere river; France  相似文献   
526.
河南省小麦白粉病流行原因和减灾对策   总被引:4,自引:0,他引:4  
本文阐述了河南省小麦白粉病流行成灾的特点、原因和发展趋势,指出今后数年内小麦白粉病的发生仍将严重,并提出了短期和长期减灾对策建议.  相似文献   
527.
Taylor AJ 《Disasters》1983,7(1):37-40
This paper defines the various levels within government, the voluntary agencies and the community which might benefit from training and makes suggestions as to where the emphasis should be placed. It points out that training programmes should be designed to meet the expressed needs of a particular group of trainees as well as be related to the current or potential disaster situation.  相似文献   
528.
Carter W 《Disasters》1983,7(1):34-36
This paper discusses both the need for training within a wider context of community disaster preparedness and the major alternatives in methods of training. Emphasis is placed on the importance of compatibility between the resources within a given country and appropriate training programmes.  相似文献   
529.
从经济学和管理科学的角度 ,笔者结合铁路运输系统的特殊性 ,对铁路企业安全管理激励与约束机制问题进行分析和探讨 ;指出了在铁路安全管理中要坚持长期激励为主 ,短期激励为辅的原则 ;合理调整物质激励与非物质激励的关系 ,使两者有效相容 ,使职工和企业成为利益的共同体 ;并在铁路系统内部要注重安全文化建设 ,形成铁路安全文化的氛围  相似文献   
530.
青藏高原多年冻土区铁路路堤变形特征研究   总被引:6,自引:1,他引:6  
路堤的稳定是公路、铁路等行车安全的保证。路堤变形通过路基—轨道—车辆大系统的相互作用而影响行车安全。冻胀、融沉是多年冻土地区路堤变形的重要形式。多年冻土区的路基变形问题是至今仍未彻底解决的一大难题。青藏铁路穿越 5 5 0km多年冻土区 ,为研究多年冻土区路堤变形特征 ,笔者对青藏铁路某试验段进行变形监测并对监测数据进行分析。结果表明铁路路堤的修建改变了多年冻土原来的水热平衡 ,天然冻土上限的变化导致路堤产生变形。同时 ,变形特征还受路堤边坡的坡向、降水量和地基土类型等因素的制约。在此基础上 ,提出几点减少多年冻土区铁路路堤变形的一些看法和建议。  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