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   11083篇
  免费   17篇
  国内免费   40篇
安全科学   22篇
废物处理   855篇
环保管理   1355篇
综合类   1059篇
基础理论   3353篇
环境理论   2篇
污染及防治   2241篇
评价与监测   1274篇
社会与环境   975篇
灾害及防治   4篇
  2023年   59篇
  2022年   172篇
  2021年   115篇
  2020年   25篇
  2019年   47篇
  2018年   1508篇
  2017年   1421篇
  2016年   1274篇
  2015年   166篇
  2014年   93篇
  2013年   179篇
  2012年   519篇
  2011年   1418篇
  2010年   744篇
  2009年   652篇
  2008年   945篇
  2007年   1278篇
  2006年   63篇
  2005年   52篇
  2004年   55篇
  2003年   81篇
  2002年   125篇
  2001年   22篇
  2000年   17篇
  1999年   7篇
  1998年   12篇
  1997年   2篇
  1996年   6篇
  1995年   2篇
  1994年   4篇
  1993年   3篇
  1992年   4篇
  1989年   2篇
  1988年   3篇
  1985年   2篇
  1984年   13篇
  1983年   12篇
  1982年   5篇
  1979年   2篇
  1966年   1篇
  1965年   2篇
  1964年   2篇
  1962年   2篇
  1961年   4篇
  1958年   3篇
  1957年   3篇
  1956年   2篇
  1955年   4篇
  1953年   1篇
  1935年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Hydroxylated polychlorobiphenyls (OH-PCBs) are major metabolites of PCBs that are widely distributed in the environment. While the effects of penta- to hepta-chlorinated OH-PCBs on neuronal differentiation have been widely reported, those of lower chlorinated OH-PCBs have not been extensively studied. To investigate the effects of lower chlorinated OH-PCBs on neuronal development, we studied the effects of mono- to hexa-chlorinated OH-PCBs on PC12 cells. Morphological changes were examined using an automatic system IN Cell Analyzer. Seventeen of the 20 OH-PCBs investigated promoted neuronal elongation in an OH-PCB concentration-dependent manner, while three OH-PCB congeners suppressed neuronal elongation based on Dunnett’s analysis. In particular, the top five OH-PCBs (4OH-PCB2, 4′OH-PCB3, 4′OH-PCB25, 4′OH-PCB68, and 4′OH-PCB159), which have hydroxyl groups at the para-position and chlorine substitutions at the 2, 4, or 3′ positions, significantly promoted neuronal elongation. Moreover, these neuronal elongations were suppressed by U0126, and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was observed in PC12 cells treated with 4OH-PCB2, 4′OH-PCB25, and 4′OH-PCB159. Taken together, our results indicate that the effect of OH-PCB on neuronal development is not dependent on the number of chlorine groups but on the chemical structure, and the mitogen-activated kinase kinase (MEK)-ERK1/2 signaling pathway is involved in this process.  相似文献   
22.
Purpose. The current research was carried out to determine grip strength (GS) with change in posture and upper-limb muscle activity of manual workers and investigate the impacts of these changes. Methods. For the current research, 120 male and 80 female participants were selected and GS was assessed using a digital hand grip dynamometer in various conditions. Results. The outcomes showed that male participants had higher GS as compared to female participants. Maximum GS was found in a standing posture with the fixed forward shoulder at 45°, elbow at 90° and a neutral position of the wrist and forearm for all participants. Conclusions. Higher values of GS were attained in standing postures which may result in attainment of higher performance levels by the workers. The outcomes justify the importance of correct postures during manual work in industries employing traditional methods.  相似文献   
23.
Chemical coagulation and adsorption, despite many drawbacks, are actually the main techniques used for the removal of pollutants from aqueous solution; however, these techniques are becoming ineffective due to the exponential increase in the amount and complexity of discharged pollutants; thus, the sludge treatment process became a more complex challenge. The present study focuses on the way to reduce the quantity of sludge formed during the removal of Ridomil Gold, a widely used pesticide-fungicide in agriculture. Results revealed that pre-treatment of initial waste solution by the gliding arc (Glidarc), a source of non-thermal plasma, leads to a significant reduction of the sludge formed during the coagulation treatment. For a 20-min pre-treated effluent Glidarc followed by chemical coagulation, there was a reduction in the volume of sludge formed in the order of 90 and 80% for alum and ferric sulfate coagulants respectively without reducing the performance of pesticide removal. Therefore, there is a positive synergism between treatment by chemical coagulation and plasma treatment. These results suggest that the Glidarc can be an effective solution for the reduction of sludge obtained during treatment by coagulation.  相似文献   
24.
This study examined the influencing factors of the self-reported behavioral intentions toward genetically modified (GM) crops using a multi-stakeholder approach in the Khuzestan Province in Southwest Iran. The study focused on three different groups, including: “agricultural students,” “agricultural private firms’ managers” and “rich-resource farmers.” Data were collected using a researcher-made questionnaire and was analyzed by SPSS (V20) and AMOS (V20). Results indicated that the respondents perceive more benefits than risks for GM crops and that the perception of benefits and risks, respectively, had positive and negative impacts on the self-reported behavioral intention of the respondents. The knowledge of the respondents regarding these crops had positive impacts on perception of benefits. The results showed that both managers and students worried about the food safety and impact of GM crops on human health while farmers worried about the environmental risks of GM crops. The results also revealed that those who are the most conscious about GM crops are more trusted. The findings also showed that the majority of the respondents hold a positive view of the potential of GM crops.  相似文献   
25.
The purpose of this paper is to study the impacts of the vagueness about the transfer of the harvest right on the use of a natural resource. We develop one-period non-cooperative game frameworks to examine whether the choice of the resource owner to be hazy about the transmission of the harvest contract is optimal. In the perfect information situation, we show that it is optimal for the resource owner to forbid the transfer of the harvest right instead of being hazy about it when the transfer fees are lesser than the collected net punishment fines of the monitoring costs even though the resource would be inefficiently used. In particular, we find in this case that the government’s announcement to forbid the transfer of the right should be public. We further show that there are subgame Nash equilibria in the perfect information context and a unique Nash equilibrium in the imperfect information setting. Specifically, we show that, when the transfer fees are greater or equal to the (net) punishment fines, there is a Nash equilibrium both in perfect and imperfect information situations, precisely when the owner chooses to allow the transfer of harvest title and the resource harvester transfers it.  相似文献   
26.
Poly(butylene succinate) (PBS) was melt blended with glycerol based polyesters (PGS) synthesized from pure and technical glycerol aiming to improve the impact strength of PBS. It was found that after addition of 30 wt% PGS to PBS its impact strength was significantly increased by 344% (from 31.9 to 110 J/m) and its elongation at break was maintained at 220%. Infrared spectra of the blends showed the presence of hydroxyl groups from the PGS phase suggesting that hydrogen bonding between the phases could be responsible for a good stress transfer and an efficient toughening in the PBS/PGS blends. Scanning electron microscopy imaging showed a good dispersion of PGS phase into PBS with a PGS particle size of 10 μm and less and no agglomeration. Addition of PGS to PBS was shown to be an effective strategy for improvement of PBS impact resistance without serious detrimental effects on its thermal and rheological properties.  相似文献   
27.
28.
Selection of appropriate residue application method is essential for better use of biomass for soil and environmental health improvement. A laboratory incubation experiment was conducted for 75 days to investigate C and N mineralization of residues of soybean (Glycine max L.), chickpea (Cicer arietinum L.), maize (Zea mays L.), and wheat (Triticum aestivum L.) placed on the soil surface and incorporated into the soil. The residue of soybean and chickpea had a greater decomposition rate than that of maize and wheat, despite of their placements. Higher rate of decomposition of the residue of soybean and chickpea was recorded when it was kept on the soil surface while soil incorporation of residue of wheat and maize resulted in faster decomposition. Therefore, these findings could be used as guidelines for management of crop residue application in farmland to improve soil and environmental quality.  相似文献   
29.
Phyllanthus niruri is a plant that is used to prevent calcium oxalate crystallisation and to block the stone formation in urolithiasis. Contaminants in the environment can be readily taken up by medicinal plants due to their ability to absorb chemicals into their tissues. If contaminated plants are ingested, they have the potential to negatively affect human and environmental health. The aim of this study was to assess contamination in the soil and the medicinal plant P. niruri by cadmium (Cd) in ceramic industrial areas of Monte Carmelo, Brazil. Soil samples and plant samples (divided in root, shoot and leaves) were collected from a contaminated monitoring site and from a rural area (which was used as a reference site for comparative purposes). The Cd concentrations of the samples were analysed with an atomic absorption spectrometer. P. niruri was found to be sensitive to soil contamination by Cd that was attributed to ceramic industrial emissions. The results revealed that Cd bioaccumulation in the roots and shoots of P. niruri was associated with a significant increase (p?<?0.05) in the concentration of active lignan compounds (phyllanthin and hypophyllanthin) in the leaves. The identification of high concentrations of Cd and active lignan compounds suggests a risk of contamination of the site and the risk of a high dose of Cd to people exposed at the site.  相似文献   
30.
A good water supply and wastewater management is essential for a local sustainable community development. This is emphasized in the new global goals of the UN Sustainable Development, where the sixth objective is to: “Ensure availability and sustainable management of water and sanitation for all” (United Nations 2015). This obviously raises the question of how this can be achieved considering the very different conditions and cultures around the globe. This article presents the Greenlandic context and elucidates the current Greenland water supply system and wastewater management system from a socio-technical approach, focusing on the geographic, climatic and cultural challenges. The article identifies a diverse set of system constellations in different parts of Greenland and concludes with a discussion of health and quality of life implications.  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