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   115篇
  免费   1篇
  国内免费   2篇
安全科学   2篇
废物处理   11篇
环保管理   10篇
综合类   23篇
基础理论   17篇
污染及防治   39篇
评价与监测   11篇
社会与环境   5篇
  2023年   1篇
  2022年   6篇
  2021年   3篇
  2020年   2篇
  2019年   1篇
  2018年   6篇
  2017年   5篇
  2016年   2篇
  2015年   2篇
  2014年   6篇
  2013年   12篇
  2012年   6篇
  2011年   5篇
  2010年   4篇
  2009年   5篇
  2008年   3篇
  2007年   5篇
  2006年   8篇
  2005年   2篇
  2004年   4篇
  2003年   3篇
  2002年   4篇
  2001年   2篇
  1999年   1篇
  1995年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1979年   1篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1969年   1篇
  1966年   1篇
  1964年   2篇
  1963年   3篇
  1961年   1篇
  1959年   1篇
  1958年   2篇
  1957年   1篇
排序方式: 共有118条查询结果,搜索用时 31 毫秒
71.
The Sharda River creates and maintains the ecologically diverse remnant patches of rare Terai ecosystem in northern India. This study used repeat satellite imagery and geographic information system analysis to assess the planform dynamics along a 60 km length of the Sharda River between 1977 and 2001 to understand the altered dynamics and its plausible causes in this data-poor region. Analyses revealed that the Sharda River has undergone significant change corresponding to enhanced instability in terms of increased number of neck cut-offs and consistent occurrence of avulsions in subsequent shorter assessment periods. An increased channel area (8 %), decreased sinuosity (15 %), increased braiding intensity, and abrupt migrations were also documented. The river has migrated toward the east with its west bankline being more unstable. The maximum shifts were 2.85 km in 13 years (1977–1990), 2.33 km in next 9 years (1990–1999), and a substantial shift of 2.39 km in just 2 years (1999–2001). The altered dynamics is making the future of critical wildlife habitats in Kishanpur Wildlife Sanctuary and North Kheri Forest Division precarious and causing significant economic damage. Extensive deforestation and expansion of agriculture since the 1950s in the catchment area are presumed to have severely impacted the equilibrium of the river, which urgently needs a management plan including wildlife habitat conservation, control, and risk reduction. The present study provides a strong foundation for understanding channel changes in the Sharda River and the finding can serve as a valuable information base for effective management planning and ecological restoration.  相似文献   
72.
Environmental Science and Pollution Research - Non-small cell lung cancer (NSCLC) is reported to have a high incidence rate and is one of the most prevalent types of cancer contributing towards 85%...  相似文献   
73.
We present two cases of OEIS (omphalocele, exstrophy, imperforate anus, spinal defects) complex -MIM 258040 and a review of the literature. Case 1 was a 14-year-old girl who presented at 30 weeks' gestation. An ultrasound examination showed an omphalocele and spina bifida; the bladder was not visualised. She went into spontaneous labour two weeks later and the baby died shortly after birth. A full post-mortem examination was refused, but the mother did agree to an external examination, skin biopsy for fibroblast culture, X rays and MR imaging. The MR imaging showed a pelvic kidney, a large omphalocele containing the other kidney, liver, bowel and a fluid filled structure thought to represent an exstrophy of the bladder (EB). Case 2 was a 30-year-old woman who had an ultrasound examination at 20 weeks' gestation; this showed an omphalocele, but the bladder was not visualised. The pregnancy was subsequently terminated and a post-mortem examination showed a low set umbilical cord associated with a small omphalocele; there was an imperforate anus; a blind ending rectum terminated in the omphalocele. We conclude that these two cases illustrate the variability of the OEIS complex. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
74.
75.
The practice of operating municipal solid waste landfills as bioreactor landfills has become more common over the past decade. Because simulating moisture balance and flow is more critical in such landfills than in dry landfills, researchers have developed methods to address this problem using the hydrologic evaluation of landfill performance (HELP) model. This paper discusses three methods of applying the HELP model to simulate the percolation of liquids added to landfill waste: the leachate recirculation feature (LRF), the subsurface inflow (SSI) feature, and additional rainfall to mimic liquids addition. The LRF is simple to use but may not be able to bring the landfill to bioreactor conditions. The SSI feature provides a convenient user interface for modeling liquids addition to each layer. The additional rainfall feature provides flexibility to the model, allowing users to estimate the leachate generation rate and the leachate head on bottom liner associated with daily variation in the liquids addition rate. Additionally, this paper discusses several issues that may affect the HELP model, such as the time of model simulation, layers of liquids addition, and the limitations of the HELP model itself. Based on the simulation results, it is suggested that the HELP model should be run over an extended period of time after the cessation of liquids addition in order to capture the peak leachate generation rate and the head on the liner (HOL). From the perspectives of leachate generation and the HOL, there are few differences between single-layer injection and multiple-layer injection. This paper also discusses the limitations of using the HELP model for designing and permitting bioreactor landfills.  相似文献   
76.
Water table fluctuation (??h) can be used to rapidly assess changes in groundwater storage. But ??h gives acceptable results only if the point of observation is ideally located in the catchment of interest and gives average ??h of the area, a condition which is rarely met. However, if large numbers of observation wells are located within a basin (a catchment) the average ??h can be computed and used. But, a better way is to use points obtained by shallowest water level and deepest water levels to construct a wedge of water table fluctuation across the area of interest; the mean height of this wedge can be assumed to be the mean ??h in the area. And when there is only one observation well, the fact that water table is a subdued replica of the topography, is made use to construct the wedge of water table fluctuation. The results from some randomly selected observations in typical semi-arid, hard rock environment in Andhra Pradesh show that through this approach mean ??h can be effectively used to get change in groundwater storage in area. The mean recharge obtained in this study is in the order of 75 and mean draft is 58?mm/a, while mean recharge and draft obtained by conventional technique are 66 and 54?mm/a, respectively. The most likely specific yield around the middle reaches of a catchment ranges between 0.012 and 0.041 which is within the range given by Groundwater Estimation Committee of India for hard rocks.  相似文献   
77.
Kumar P  Singh DK 《Chemosphere》2006,63(9):1568-1574
The molluscicidal activity of dried root latex powder of Ferula asafoetida, flower-bud powder of Syzygium aromaticum and seed powder of Carum carvi against the snail Lymnaea acuminata was studied. The molluscicidal activity of all the three plant products was found to be both time and concentration dependent. The toxicity of S. aromaticum flower-bud powder (96 h LC(50):51.98 mg/l) was more pronounced than that of root latex powder of F. asafoetida (96 h LC(50):82.71 mg/l) and seed powder of C. carvi (96 h LC(50):140.58 mg/l). Ethanol extract was more toxic than other organic extracts. The ethanol extract of S. aromaticum (24h LC(50):83.53 mg/l) was more effective than that of F. asafoetida (24h LC(50):132.31 mg/l) and C. carvi (24h LC(50):130.61 mg/l) in killing the test animals. The 96 h LC(50) of column purified fraction of seed powder of C. carvi was 5.40 mg/l whereas those of flower-bud powder of S. aromaticum and dried root latex powder of F. asafoetida were 7.87 and 9.67 mg/l, respectively. The product of F. asafoetida, S. aromaticum and C. carvi may be used as potent molluscicides.  相似文献   
78.
Leaves of Artemisia annua linn. and Azadirachta indica were extracted in petroleum ether and hexane respectively by different methods of extraction i.e. cold extraction, reflux extraction and soxhlet extraction. The crude extract obtained was tested against third instar larvae of Anopheles stephensi. On comparison of larval mortality of crude extract obtained by these three methods, both soxhlet and reflux extraction method showed 100% mortality at 200 ppm after 48 hr in case of A. annua. However LC50 (20 ppm) value of crude extract obtained by soxhlet extraction showed better results than reflux extraction (35 ppm) method after 72 hr. In case of A. indica, crude obtained by soxhlet showed 100% mortality (after 48 hr) at 250 ppm and LC50 of 69 ppm at 72 hr. Reflux extraction does not show any appreciable mortality even at 250 ppm concentration.  相似文献   
79.
The widespread application of pesticides in agriculture, public health, and industry and in and around the home can result in the accumulation of pesticides in the environment. Therefore, a survey has been conducted during 1993-1996 to investigate the magnitude of contamination of bovine milk with organochlorine pesticide (OCP) residues from Jaipur City, Rajasthan, India. Milk samples, i.e., dairy (toned and whole) and buffalo milk, were collected seasonally, and pesticide residues were assessed using a gas chromatograph (GC) with an electron capture detector (ECD). The results indicate that all the milk samples were contaminated with dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDE and p,p'-dichlorodiphenyldichloroethane [DDD]), isomers of hexachlorocyclohexane (HCH; alpha, beta, and gamma), heptachlor and its epoxide, and aldrin. Seasonal variations of these pesticide residue levels were also observed in all the milk samples. Samples collected during winter season were found to contain higher residue levels as compared to other seasons.  相似文献   
80.
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