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   1615篇
  免费   17篇
  国内免费   40篇
安全科学   22篇
废物处理   109篇
环保管理   156篇
综合类   139篇
基础理论   290篇
环境理论   2篇
污染及防治   545篇
评价与监测   300篇
社会与环境   105篇
灾害及防治   4篇
  2023年   59篇
  2022年   172篇
  2021年   116篇
  2020年   25篇
  2019年   46篇
  2018年   82篇
  2017年   88篇
  2016年   109篇
  2015年   45篇
  2014年   78篇
  2013年   176篇
  2012年   74篇
  2011年   89篇
  2010年   69篇
  2009年   58篇
  2008年   71篇
  2007年   54篇
  2006年   63篇
  2005年   34篇
  2004年   24篇
  2003年   20篇
  2002年   28篇
  2001年   8篇
  2000年   7篇
  1999年   5篇
  1998年   3篇
  1997年   2篇
  1996年   6篇
  1995年   2篇
  1994年   4篇
  1993年   3篇
  1992年   3篇
  1989年   2篇
  1988年   3篇
  1985年   2篇
  1984年   2篇
  1983年   4篇
  1982年   5篇
  1979年   2篇
  1969年   1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
排序方式: 共有1672条查询结果,搜索用时 406 毫秒
791.
The Gulf of Kachchh is characterised by a strong tidal variation and the reef communities are capable of higher exposure time during negative tides. About 11 sites located along the Marine National Park (MNP) from west to east were studied for assessing the present status of live coral cover along with other life-form categories. In the present study, the maximum live coral cover was recorded in Pirotan Island, followed by Laku Point, Mithapur and Boriya reef. Multivariate analyses such as Principal Component Analysis and Correspondence Analysis supported that the contribution of live coral cover was more towards Pirotan Island whereas the contribution of coral species cover was more towards Laku Point. Bray-Curtis cluster analysis categorized all the study sites into four major clusters with 78 % similarity based on life-form categories. Among them, two clusters from western region (one forming site from Mithapur Reef to Lakku Point and another one forming from Ashaba Gugar Reef to Dabdaba Island), the third one combines the western and eastern regions (Boriya Reef to Kalubar Island), the fourth one comprises the eastern region (Narara Reef to Sikka), and one outlier Pirotan Island. Based on coral species cover, two major clusters with 55 % similarity were formed. Among them, one cluster was formed from Pirotan Island to Kalubar Island in the eastern side of MNP and the second one comprised the western region of MNP (Boriya Reef to Laku Point), and one outlier Mithapur Reef. Thirty one species of live corals belonging to 8 families and 18 genera were recorded in the Marine National Park itself during the study period.  相似文献   
792.
Nanotechnology is expected to have a beneficial influence on agriculture, food and environment, due to the unique properties of nanomaterials. However, little is known about their safety and potential toxicity. Here we review metal nanoparticles, nanometal oxides, carbon nanotubes, liposomes and dendrimers. We present the application of these nanomaterials in agriculture, food and environment for plant protection; disease treatment; packing materials; development of new tastes, textures and sensations; pathogen detection; and delivery systems. We discuss risk assessment of nanomaterials and toxicological impacts of nanomaterials on agriculture, food and environment. We then provide regulatory guidelines for the safer use of nanomaterials.  相似文献   
793.
Roughly one-third of the food produced in the world for human consumption every year, approximately 1.3 billion tonnes, gets lost or wasted, according to the Food and Agriculture Organization (FAO). There is therefore an urgent need for new methods to preserve food. Encapsulation using nanoemulsions is a powerful technique for the protection of food-grade ingredients including vitamins, lipids, antioxidants and antimicrobial agents. In general, nanoemulsion systems demonstrate superior characteristics over conventional emulsions. This is due to their smaller droplet size, transparent optical properties, higher physical stability against droplet destabilization factors and improved bioavailability of the entrapped active ingredients. In general, nanoemulsions have been prepared with different sizes of droplets. However, a droplet size higher than 200 nm is generally preferred for food applications. Here we review nanoemulsion compositions, types of active ingredients, applications in different types of food systems, toxicological and safety aspects, and future directions.  相似文献   
794.
Journal of Material Cycles and Waste Management - In this study, pyrolysis of agricultural residues, such as rice straw (RS), wheat straw (WS), and sugarcane bagasse (SB), was performed in a...  相似文献   
795.
Masto  R. E.  Singh  M. K.  Rout  T. K.  Kumar  A.  Kumar  S.  George  J.  Selvi  V. A.  Dutta  P.  Tripathi  R. C.  Srivastava  N. K. 《Environmental geochemistry and health》2019,41(5):1923-1937
Environmental Geochemistry and Health - Polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) (Ba, Zn, Pb, Cu, Cr, Ni, As, Co) were determined in the road dusts of a coal...  相似文献   
796.
797.
798.
An index known as leachate pollution index (LPI) for quantifying the leachate contamination potential of municipal landfills had been developed and reported by the authors. It is a quantitative tool by which the leachate pollution data of landfill sites can be reported uniformly. LPI is an increasing scale index and has been formulated based on the Delphi technique. It provides a convenient means of summarizing complex leachate pollution data and facilitates its communication to the general public, field professionals and policy makers. However, it is observed that the LPI, like any other environmental index, fails to effectively communicate the details about the strength of various pollutants/pollutant groups present. In an effort to make the LPI more informative and useful, it is proposed to divide the LPI into three sub-indices. The aggregation of these three sub-LPIs will result in the overall LPI. The formulation and the application of LPI and its three sub-indices are presented in this paper. It has been concluded that the splitting of LPI into three sub-indices provides a better insight on the strength of various pollutants and can be useful to the experts in deciding various management issues regarding leachate treatment. The leachate characteristics of a UK landfill have been used as a case study to demonstrate the calculation of three sub-LPIs and the overall LPI.  相似文献   
799.
ABSTRACT: Past historical evidence indicates that droughts have had great impacts on human life. Drought (or scarcity of water) is assessed based on two key factors, namely, the estimated water demand, and the expected water supply. The formulation of these key factors for a region largely depends on the agro-climatic and economic conditions. Consideration of one such key factor is the relationship between the crop yield and water deficit in the assessment and prediction of agricultural droughts. The varying nature of this relationship from crop to crop adds to the complexity of agricultural drought analysis. To overcome this difficulty in analyzing agricultural droughts of a region, it is adequate to consider and place emphasis on a single crop (i.e., an index crop) grown homogeneously over the major area of the region. From one year to another year, the pattern of water requirement during the growing season of an index crop is rather stationary, and the water supply in arid and semi-arid area is mainly from seasonal random precipitation. In a region, grain yield of the index crop and, in turn, assessment of the severity of drought can reasonably be predicted as a function of the time of crop sowing and the distribution of rainfall, provided that temporal and spatial effects of other contributing factors (crop variety, soil fertility status, crop disease, pest control, cultivation practices etc.) on grain yield are considered to be uniformly distributed (i.e., stable). A predictive method of assessing agricultural droughts in an arid area of western India is presented. The major crop (Pearl Millet) of this region is grown from. July through September. The formulation of the proposed predictive method inherently implies that the grain yield of the main crop is a reliable indicator of agricultural drought. In the development of this predictive relationship (i.e., a regression type model) a number of potential yet simple variables affecting the grain yield in the region were investigated. The soil moisture index, although generally considered significant compared to the simple variables, has been found to account for insignificant variation in the grain yield. Results of our investigations suggest that it would be advisable to exclude the soil moisture index variable from the model. The proposed regression model can be used in the prediction of grain yield of the main crop several months ahead of crop harvesting operations and, in turn, the assessment of agricultural drought severity as mild, moderate, or severe. Such an assessment is expected to be helpful to planners for arranging appropriate measures to effectively combat agricultural drought situations.  相似文献   
800.
A number of chlorinated derivatives of phenols, catechols, guaiacols, syringaldehydes, have been detected and their concentrations estimated, using gas chromatography in the chlorination (C) and extraction (E) stage of spent bleach liquor generated in the laboratory by bleaching rice-straw soda pulp. The concentration of various compounds detected have also been compared with their reported 96LC50 values.  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