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   5477篇
  免费   27篇
  国内免费   25篇
安全科学   131篇
废物处理   296篇
环保管理   432篇
综合类   829篇
基础理论   1356篇
环境理论   1篇
污染及防治   1352篇
评价与监测   396篇
社会与环境   709篇
灾害及防治   27篇
  2023年   43篇
  2022年   76篇
  2021年   60篇
  2020年   29篇
  2019年   42篇
  2018年   75篇
  2017年   90篇
  2016年   110篇
  2015年   70篇
  2014年   146篇
  2013年   416篇
  2012年   167篇
  2011年   241篇
  2010年   214篇
  2009年   219篇
  2008年   253篇
  2007年   250篇
  2006年   240篇
  2005年   207篇
  2004年   187篇
  2003年   214篇
  2002年   175篇
  2001年   254篇
  2000年   161篇
  1999年   101篇
  1998年   41篇
  1997年   58篇
  1996年   53篇
  1995年   60篇
  1994年   64篇
  1993年   59篇
  1992年   58篇
  1991年   61篇
  1990年   66篇
  1989年   52篇
  1988年   56篇
  1987年   54篇
  1986年   55篇
  1985年   41篇
  1984年   47篇
  1983年   47篇
  1982年   48篇
  1980年   30篇
  1979年   32篇
  1978年   29篇
  1977年   28篇
  1976年   28篇
  1974年   31篇
  1973年   30篇
  1972年   27篇
排序方式: 共有5529条查询结果,搜索用时 0 毫秒
691.
692.
The aim of this study was to investigate the effect of relative humidity (RH) and temperature on norovirus (NoV) persistence as infectious particles on food-contact surfaces such as stainless steel and polyvinyl chloride (PVC). For this purpose, a new method combining enzymatic digestion with molecular beacon-based NASBA targeting the ORF1-ORF2 domain was developed to discriminate between infectious and noninfectious NoV. Stainless steel and PVC disks were contaminated with known amounts of human NoV and kept for 56 days at 7 and 20°C at high (86% ± 4%) and low (30% ± 10%) RH. NoV retained its putative infectivity for 56 days on PVC and for 49 days on stainless steel at 7°C and for 7 and 28 days, respectively, at low and high RH at 20°C on both tested surfaces. These results confirm that NoV persists in an infective state on inert surfaces for long periods of time and consequently may cause illness. The new molecular approach to detecting infectious NoV on inert surfaces may provide valuable information for evaluating environmental surface decontamination strategies.  相似文献   
693.
Each year governments and industry around the globe spend billions of dollars in search of treatments and cures for diseases that shorten lives, which often means gadgets, implants, radiation and pills. These “cures”, do not get to the root of the problem. Perhaps it is time for us to adjust our thinking to be more proactive instead of reactive in public health. Perhaps we need to consider confronting environmental pollution of air, soil and water at a local level. As the Physicians for Social Responsibility point out, we should be “preventing what we cannot cure”. One such preventive measure is ensuring that our communities, including our poor inner-city neighbourhoods, enjoy a clean environment. We challenge local and national policy-makers to respond to the global call and to take action to address environmental toxins; to take local action to ameliorate the pollution of the air, water and soil in so many of our nation’s neighbourhoods. A person’s neighbourhood, and the proximity of dangerous environmental contaminants within it, is a powerful predictor of how long s/he will live. While situations like the poisoning of the water in Flint, Michigan have gotten some attention, they are generally treated as the exception rather than a reflection of real environmental hazards that exist in the west. Moreover we wonder why more endemic issues of neighbourhood environmental contamination that shorten human lives are not a priority for local action or that it is not linked to disproportionate production of greenhouse gases that cause climate change/warming/chaos.  相似文献   
694.
MgO nanocrystals were synthesized and doped with different concentrations in poly(methylmethacrylate) (PMMA) to prepare hybrid organic-inorganic coatings based on polymer nanohybrid thin films. The nanoparticles were found to be spherical with 62 nm diameter as determined by X-ray diffraction (XRD) and atomic force microscope (AFM). The coatings were characterized by spectroscopic tools such as optical absorption, transmission and fluorescence spectroscopy. The prepared nanohybrid films were spin-coated on cost-effective luminescent PMMA substrates doped with highly efficient luminescent dyes luminescent solar concentrators (LSCs). The outdoor photostability tests demonstrated enhanced protection against UVA radiation for coated LSCs compared to bare LSC substrates. The current–voltage characteristics of commercially produced LSC prototypes showed that the poor UV response of monocrystalline silicon solar cell can be improved by for LSCs coated by PMMA/MgO nanohybrid films which act as luminescent down shifting layer (LDSL).  相似文献   
695.
Gypsum is one of the most important mined mineral commodities of the world. As an industrial rock, it is primarily used by the construction industry. Therefore, the economics of the gypsum market can be correlated with parameters that have controlled the origin and development of the Spanish building bubble between years 1998 and 2006. The burst of this building bubble has been interpreted as the main triggering factor for Spain's current crisis.  相似文献   
696.
With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria ‘number of colonies’ and ‘culture duration until harvest’, early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis.  相似文献   
697.
This study investigated the acute nickel toxicity on nitrification of low ammonia synthetic wastewater at 10, 23, and 35°C. The nickel inhibition half-velocity constants(K_(I,Ni)) for ammonia oxidizing bacteria(AOB) and nitrite oxidizing bacteria(NOB) based on Ni/MLSS ratio at 10, 23, and 35°C were 5.4 and 5.6 mg Ni/g MLSS, 4.6 and 3.5 mg Ni/g MLSS, and 9.1 and 2.7 mg Ni/g MLSS, respectively. In addition, chronic toxicity of nickel to nitrification of low ammonia synthetic wastewater was investigated at 10°C in two sequencing batch reactors(SBRs). Long-term SBRs operation and short-term batch tests were comparable with respect to the extent of inhibition and corresponding Ni/MLSS ratio. The μ_(max), b, and K_o of AOB were 0.16 day~(-1), 0.098 day~(-1) and 2.08 mg O_2/L after long-term acclimatization to nickel of 1 mg/L at 10°C, high dissolved oxygen(DO)(7 mg/L) and long solids retention time(SRT) of 63–70 days. Acute nickel toxicity of nitrifying bacteria was completely reversible.  相似文献   
698.
The European Union (EU) has set a target to reduce its greenhouse gas (GHG) emissions at least 10 % below the 2005 levels by 2020 in the non-Emission Trading Sector (non-ETS). As part of this, each Member State has a binding national emission limitation target for the non-ETS sector. Finland’s target, examined as a case study in this paper, is to reduce emissions at least 16 % below 2005 levels by 2020. The objective of this study is to find cost optimal mitigation portfolios that meet Finland’s reduction target and to analyze the risks of not attaining the emission target or exceeding the assumed costs. The question was addressed with a stochastic optimization model, Stochastic Optimization of non-ETS Emissions (SONETS) selecting separate mitigation measures that meet the target on expectation. The results show that optimal portfolios include relatively high uncertainty both in costs and achieved reductions. The prices of crude oil and diesel, and the abatement cost of reducing hydrofluorocarbon (HFC) emissions seem to account for the majority of uncertainty regarding total costs. The baseline predictions for various non-ETS subsectors (such as transport and agriculture) were found to have the greatest contribution to the uncertainty of attaining emission target. The results also show that some abatement actions are chosen in nearly all efficient portfolios, while other actions are seldom chosen. For example replacing oil burners in the end of technical life time or recovery of methane (CH4) from waste are often chosen whereas ban of landfilling of organic waste is chosen extremely seldom. It also seems that the results are somewhat sensitive to the inclusion or exclusion of the interdependencies of mitigation measures.  相似文献   
699.
Mitigation and Adaptation Strategies for Global Change - Bioenergy with carbon dioxide (CO2) capture and storage (BECCS) technologies represent an interesting option to reach negative carbon...  相似文献   
700.
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