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   9227篇
  免费   904篇
  国内免费   1435篇
安全科学   815篇
废物处理   410篇
环保管理   767篇
综合类   4405篇
基础理论   1669篇
环境理论   4篇
污染及防治   1914篇
评价与监测   716篇
社会与环境   587篇
灾害及防治   279篇
  2024年   32篇
  2023年   173篇
  2022年   474篇
  2021年   472篇
  2020年   491篇
  2019年   346篇
  2018年   463篇
  2017年   398篇
  2016年   471篇
  2015年   446篇
  2014年   531篇
  2013年   790篇
  2012年   732篇
  2011年   708篇
  2010年   637篇
  2009年   529篇
  2008年   593篇
  2007年   647篇
  2006年   565篇
  2005年   402篇
  2004年   328篇
  2003年   223篇
  2002年   198篇
  2001年   170篇
  2000年   122篇
  1999年   79篇
  1998年   28篇
  1997年   21篇
  1996年   13篇
  1995年   41篇
  1994年   34篇
  1993年   15篇
  1992年   21篇
  1991年   12篇
  1990年   12篇
  1989年   13篇
  1988年   10篇
  1967年   8篇
  1966年   13篇
  1965年   15篇
  1964年   30篇
  1963年   12篇
  1962年   18篇
  1961年   13篇
  1960年   10篇
  1959年   26篇
  1958年   28篇
  1957年   19篇
  1956年   13篇
  1955年   19篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
981.
The primary aim of our research was to investigate the applicability of activated sludge models (ASM) for aerobic thermophilic processes, especially autothermal thermophilic aerobic digestion (ATAD). The ASM3 model (Gujer et al., 1999) theoretically seems to be the most suitable, because storage plays an important role in a batch-feed cycle system like ATAD. The ASM3 model was extended with an activation step of the thermophilic organisms. This model was calibrated and verified by independent test results, demonstrating its ability to describe the process. The growth (microH = 26.04 day(-1)), storage (k(STO) = 20.39 day(-1)), hydrolysis (kH = 11.15 day(-1)) and decay rates (b 9H,O2) = 1.28 day(-1), b(STO,O2 = 1.10 day-1)) obtained from calibration are significantly higher at 55 degrees C than at mesophilic temperatures, justifying the faster metabolism at higher temperatures. An inert fraction of the biomass (characterized by the model parameter f(i) = 0.4) was found to be significantly greater than in the mesophilic case. This can be attributed to the lower diversity of the thermophilic species and thus to their narrower substrate spectra.  相似文献   
982.
Corals are the primary reef-building organisms, therefore it is key to understand their recruitment patterns for effective reef management. Coral recruitment rates and juvenile coral abundance were recorded in the Wakatobi National Marine Park, Indonesia, on two reefs (Sampela and Hoga) with different levels of environmental degradation (12.5 vs. 44 % coral cover with high and low sedimentation rates, respectively) to examine consistencies in recruitment patterns between years and seasons. Recruitment was measured on multiple panels at two sites on each reef (6–7 m depth) and cleared areas of natural reef. Although coral recruitment was twofold higher in 2008–2009 than in 2007–2008, and seasonal differences were identified, consistent significant differences in recruitment rates were found between the two reefs even though they are separated by only ~1.5 km. Recruitment rates and juvenile abundance were lower on the more degraded reef. These patterns are likely a consequence of differential pre- and post-settlement mortality as a result of the high sedimentation rates and degraded conditions and possibly reduced larval supply.  相似文献   
983.
984.
Summary. We investigated the hypothesis that aggregation signals produced by male webbing clothes moths (WCM), Tineola bisselliella (Hum.) (Lepidoptera: Tineidae), and close-range male attractant signals produced by females have a pheromonal basis, at least in part. Gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses of bioactive methanolic extracts of male WCM disclosed three candidate pheromone components: hexadecanoic acid methyl ester (16:Ester), (Z)-9-hexadecenoic acid methyl ester (Z9—16:Ester), and octadecanoic acid methyl ester (18:Ester). In bioassay experiments in a large Plexiglas™ arena, a blend of synthetic 16:Ester plus Z9—16:Ester was attractive to male and virgin (but not mated) female WCM; the 18:Ester was inactive. GC-EAD analyses of pheromone gland extracts from female WCM revealed (E,Z)-2,13-octadecadienal (E2Z13—18:Ald) and (E,Z)-2,13-octadecadienol (E2Z13—18:OH) as candidate sex pheromone components. In arena bioassay experiments, 1—5 female equivalents of synthetic E2Z13—18:Ald (0.2 ng) and E2Z13—18:OH (0.1 ng) were more attractive to male WCM than were two virgin female WCM. We anticipate that the combination of aggregation and sex pheromones, male-produced sonic aggregation signals, and habitat-derived semiochemicals will be highly effective in attracting male and female WCM to commercial traps. Received 12 January 2001; accepted 8 June 2001.  相似文献   
985.
在对某铸造车间砂再生除尘系统存在的问题进行实测和分析的基础上,更新了除尘器,并对管路及除尘器进行了系统的重新分配和组合改造,取得了明显效果,改善了车间环境及工人的劳动条件。  相似文献   
986.
Dynamic Games in the Economics and Management of Pollution   总被引:1,自引:0,他引:1  
The paper provides a survey of the literature which utilizes dynamic state-space games to formulate and analyze intertemporal, many decision-maker problems in the economics and management of pollution.  相似文献   
987.
This article analyses, using Bayesian networks, the circumstances surrounding workplace tasks performed using auxiliary equipment (ladders, scaffolding, etc.) that may result in falls. The information source was a survey of employees working at a height. We were able to determine the usefulness of this approach – innovative in the accident research field – in identifying the causes that have the greatest bearing on accidents involving auxiliary equipment: in these cases, the adoption of incorrect postures during work and a worker’s inadequate knowledge of safety regulations. Likewise, the duration of tasks was also associated with both these variables, and therefore, with the accident rate. Bayesian networks also enable dependency relationships to be established between the different causes of accidents. This information – which is not usually furnished by conventional statistical methods applied in the field of labour risk prevention – allow a causality model to be defined for workplace accidents in a more realistic way. With this statistic tool, the expert is also provided with useful information that can be input to a management model for labour risk prevention.  相似文献   
988.
The chemical speciation of the 16 polycyclic aromatic hydrocarbons associated to the particulate matter of conventional diesel fuel, rapeseed methyl esters, waste cooking oil methyl esters, waste cooking oil ethyl esters and their conventional fuel blends has been carried out. The speciation of these individual compounds was made by a combination of thermal extraction, solid phase micro-extraction and GC/MS analysis. This PAH speciation method was applied to a real samples obtained from a diesel engine under two different operating modes, urban and extraurban modes. The purpose of this work was to study the relationship between the amount, type and carcinogenic potency of polycyclic aromatic hydrocarbons in engine emissions and the multi-component biodiesel fuel composition.  相似文献   
989.
Helpful advice and discussions with Prof. M. Eigen are gratefully acknowledged. A conversation with Dr. Chr. Biebricher proved most useful.  相似文献   
990.
Among the difficulties found in the implementation of ISO 14001 systems, resistance to change can always be found. It is mainly a consequence of the hurry to change, loss of focus, concentration of decision making at the level of top management, arbitrary imposition of objectives and results, faulty communication, and the absence of motivational and financial incentive for change.Therefore, the main objective of this paper is to present best practices with respect to the management of organizational change due to the implementation of ISO 14001 norms in two industrial companies in the Midwest region of the State of São Paulo – Brazil.  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