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   188篇
  免费   3篇
  国内免费   4篇
安全科学   4篇
废物处理   14篇
环保管理   15篇
综合类   36篇
基础理论   29篇
污染及防治   57篇
评价与监测   22篇
社会与环境   18篇
  2023年   2篇
  2022年   12篇
  2021年   4篇
  2020年   2篇
  2019年   6篇
  2018年   7篇
  2017年   6篇
  2016年   7篇
  2015年   10篇
  2014年   13篇
  2013年   21篇
  2012年   13篇
  2011年   8篇
  2010年   5篇
  2009年   7篇
  2008年   6篇
  2007年   6篇
  2006年   7篇
  2005年   4篇
  2004年   3篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1994年   2篇
  1991年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1977年   1篇
  1975年   1篇
  1974年   3篇
  1973年   1篇
  1972年   4篇
  1968年   1篇
  1961年   1篇
  1959年   1篇
  1958年   3篇
  1957年   1篇
  1956年   2篇
  1955年   3篇
  1954年   1篇
排序方式: 共有195条查询结果,搜索用时 15 毫秒
151.
The population of climbing perch, Anabas testudineus, an important food fish in India, is presently under threat and has been declared endangered. A narrow range of environmental conditions for successful reproduction of the species was previously ascertained in breeding experiments. In this study, the role of physiological parameters including plasma glucose, total protein, cholesterol, and glycogen content in liver and ovary were determined with respect to the reproductive cycling stages. Flow cytometric analysis of cell cycle of ovary and testis in relation to reproductive cycle was also analyzed. In both the sexes, plasma glucose and plasma protein changed significantly during breeding cycle. Plasma cholesterol levels were reduced markedly during spawning. Liver and ovarian glycogen levels showed significant variation during reproductive cycling. Flow cytometric study revealed that the hypoploid and synthesis phase were altered significantly with breeding cycle in ovarian and testicular cells. Data indicate that the biochemical parameters indicative of the fish reproduction capacity are influenced by environmental conditions. Thus, climatic changes may therefore potentially induce biochemical alterations that may exert detrimental effects on fish reproduction and subsequent population decline.  相似文献   
152.
Electrocoagulation (EC) technique was adopted for the treatment of fluoride-containing drinking water in a 3?L capacity batch reactor. Experimental investigation was carried out to observe the effect of different operating parameters, such as initial fluoride concentration, current density, inter-electrode distance, on the removal of fluoride from the fluoride-rich drinking water. Aluminum flat sheet was used as the electrode material. It was observed that with an increase in current density, percentage removal of fluoride increased. It was seen that at electrode distance of 0.005?m, removal of fluoride attained its maximum compared to the other performances obtained at different inter-electrode distances. Life time of the aluminum electrodes was estimated from the electrode corrosion observed during the experiment. Total operating cost was estimated as a combination of energy cost and electrode cost. The total operating cost was evaluated as 0.38?US$?m?3 to remove fluoride from the solution with an initial fluoride concentration 10?mg?L?1. Characterizations of the electrochemically generated by-products were carried out by powder X-ray diffraction, Fourier transform infra-red Raman spectroscopy, scanning electron microscopy image and corresponding elemental analysis.  相似文献   
153.
In this paper, we propose a Bayesian method to estimate the underlying density function of a study variable Y using a ranked set sample in which an auxiliary variable X is used to rank the sampling units. The amount of association between X and Y is not known, resulting in an unknown degree of ranking error. We assume that (XY) follows a Morgenstern family of distributions. The study variable Y is assumed to have a parametric distribution, with the distribution of the parameters having a Dirichlet process prior. A Markov chain Monte Carlo procedure is developed to obtain a Bayesian estimator of the desired density function as well as of the ranking error. A simulation study is used to evaluate the performance of the proposed method. An example from forestry is used to illustrate a real-life application of the proposed methodology.  相似文献   
154.
Vermicompost is a very important biofertilizer produced through the artificial cultivation of worms i.e. Vermiculture. Vermicompost is enriched with all beneficial soil bacteria and also contain many of the essential plant nutrients like N, P, K and micronutrients. It increases soil aeration, texture and jilt. In this work, study is being carried out to find out the effect of different fertilizers such as DAF, FYM and Vermicompost on various morphological parameters and on the in vitro growth of bacterial colonies and its diversity in relation to two important leguminous plants such as Pisum sp. and Cicer sp. Results showed that plant grown in Vermicompost pretreated soil exhibited maximum increase in all morphological parameters such as root length, shoot length, number of root branches, number of stem branches, number of leaves, number of flowers, number of pods and number of root nodules in four months sampling in comparison to untreated, FYM treated and DAP treated soils. Further in Vermicompost pretreated soil, number of N2 fixing bacterial colony was maximum and showed highest diversity indices (1.6 and 0.99 and 2.0 and 0.99 for Cicer sp. and Pisum sp. respectively) than FYM, DAP and untreated control. Thus not only does the Vermicompost stimulate plant growth but also it increases the N2 fixing bacterial population in soil and also its diversity.  相似文献   
155.
A range of bio-nanocomposites were prepared by incorporation of organo modified montmorillonite nanoclay (OMMT) with or without use of aluminum hydroxide (Al(OH)3) within polylactic acid (PLA) solution. Furthermore, the solution was employed for modification of ligno-cellulosic (jute) fabric structural reinforcements. The successful incorporation of nanofillers within the host polymer, polylactic acid (PLA) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). Water uptake and swelling behaviour studies revealed that the water uptake and swelling ratio of bio-composites reduced significantly as compared to pristine jute fabric, whereas upon incorporation of OMMT and Al(OH)3, the water barrier properties reduced even further in the developed bio-nanocomposites. The flexural strength of the bio-nanocomposites also showed improved mechanical and dimensional stability. Synergistic effects of OMMT and Al(OH)3 were observed in enhancing the aforementioned physico-mechanical properties. Scanning electron microscopy (SEM) studies revealed microstructural details of developed samples. Similarly, the thermo-gravimetric analysis and linear burning rate studies of Al(OH)treated bio-nanocomposite materials revealed enhanced thermal resistance and reduced flammability respectively compared to both pristine woven jute fabric and fabrics treated with PLA alone or those without Al(OH)3. From the above results it can safely be said that the bio-nanocomposite material can be a prospective candidate for development of flame retardant biopackaging.  相似文献   
156.
Presence of pesticide residues in tobacco increases health risk of both active and passive smokers, apart from the imminent potential health problems associated with it. Thus, monitoring of pesticide residue is an important issue in terms of formulating stringent policies, enabling global trade and safeguarding the consumer’s safety. In this study, a gas chromatography-single quadrupole mass spectrometry (GC-MS) method based upon quantifier-qualifier ions (m/z) ratio was employed for detecting and assessing ten organochlorine pesticide residues (α-HCH, β-HCH, γ-HCH, δ-HCH, 2,4-DDT, 4,4-DDT, endrin, α-endosulfan, β-endosulfan and endosulfan sulphate) in 152 flue-cured (FC) tobacco leave samples from two major tobacco growing states, Karnataka and Andhra Pradesh, of India. In the majority of samples, pesticide residue levels were below the limit of quantification (LOQ). In few samples, pesticide residues were detected and they found to comply with the guidance residue levels (GRL) specifications of the Cooperation Center for Scientific Research Relative to Tobacco (CORESTA). Detection of the phase out pesticides like DDT/HCH might be due to transfer of persistent residues from the environmental components to the plant. This is the first report on these ten organochlorine pesticide residues in Indian FC tobacco.  相似文献   
157.
Soil samples were collected from agricultural fields and gardens in North 24 Parganas, West Bengal, and fungi species were isolated from them. Thirty-one fungal species were isolated with 19 found in agricultural soil and 28 in garden soil. Twenty-eight out of 31 were identified using cultural and microscopic characters, and three were unidentified. The diversity of isolated fungi was calculated by Simpson’s diversity index. The garden soil possessed more fungal colonies (750) than agricultural soil (477). In agricultural soil, the dominant fungi were Aspergillus niger, Rhizopus oryzae, and Penicillium expansum, and the dominant fungi of garden soil were A. niger and Fusarium moniliforme. Simpson’s diversity index indicated that garden soil had more fungal diversity (0.939) than agricultural soil (0.896). The entomopathogenic capacity of the isolated fungi was tested against the brinjal shoot and fruit borer (Leucinodes orbonalis Guen) which is the major insect pest of brinjal. The isolated fungi were screened against larva of L. orbonalis for their entomopathogenic potential. Beauveria bassiana, A. niger, and P. expansum showed appreciable antagonism to L. orbonalis, and their lethal doses with 50 % mortality (LD50s) were 4.0?×?107, 9.06?×?107, and 1.50?×?108 spore/mL, respectively, and their times taken to reach 50 % mortality (LT50s) were 9.77, 10.56, and 10.60 days, respectively. This work suggests the restriction of chemical pesticide application in agricultural fields to increase fungal diversity. The entomopathogenic efficacy of B. bassiana could be used in agricultural fields to increase fugal diversity and protect the brinjal crop.  相似文献   
158.
Cities across the globe are considered as major anthropogenic sources of greenhouse gases (GHG), yet very few efforts has been made to monitor ambient concentration of GHG in cities, especially in a developing country like India. Here, variations in the ambient concentrations of carbon dioxide (CO2) and methane (CH4) in residential, commercial, and industrial areas of Delhi are determined from fortnightly daytime observations from July, 2008 to March, 2009. Results indicate that the average daytime ambient concentration of CO2 varied from 495 to 554 ppm in authorized residential areas, 503 to 621 ppm in the slums or jhuggies in the unauthorized residential areas, 489 to 582 ppm in commercial areas, and 512 to 568 ppm in industrial areas with an average of 541?±?27 ppm. CH4 concentration varied from 652 to 5,356 ppbv in authorized residential areas, 500 to15,220 ppbv in the unauthorized residential areas, 921 to 11,000 ppbv in the commercial areas, and 250 to 2,550 ppbv in the industrial areas with an average of 3,226?±?1,090 ppbv. A low mid-afternoon CO2 concentration was observed at most of the sites, primarily due to strong biospheric photosynthesis coupled with strong vertical mixing.  相似文献   
159.
This study focuses on mercury (Hg) bioaccumulation in Indian cat fish, Wallagoo attu and Mystus aor, from different rivers. Methyl mercury (MeHg) concentrations were determined in muscle tissue of two different parts, ventral and dorsal part, of each species and the levels of organic mercury were co-related with lipid content of each part. The MeHg concentrations increased in a linear fashion with both weight and age for these river species. The average concentration of MeHg was found to be 0.93?±?0.60 and 1.26?±?0.62 μg Hg g?1 (expressed in wet weight basis) for ventral and dorsal parts, respectively in W. attu and this was above the 0.25 μg Hg g?1 of wet weight, the limit set by the Prevention of Food Adulteration Act for the maximum level for consumption of fish exposed to mercury pollution. In M. Aor the concentration of MeHg was not above the standard limit but threatening, it was 0.22?±?0.07 and 0.23?±?0.08 μg Hg g?1 (expressed in wet weight basis) in dorsal and ventral parts, respectively.  相似文献   
160.
The concentrations of lead, cadmium, chromium, copper, and zinc were investigated in the sewage-fed pond water, sediment, and the various organs of Labeo rohita, Catla catla, Cirrhinus mrigala, Oreochromis mossambicus, and Cyprinus carpio cultured in sewage-fed ponds, Kolkata, India. Among the metals, cadmium, lead, and zinc were detected in water and, except lead, were below the water quality guideline levels for the protection of freshwater aquatic life proposed by CEQG (Canadian Environmental Quality Guidelines) and AENV (Alberta Environment). Therefore, lead could pose danger to aquatic organisms. All the five metals were detected in the sediment and, except cadmium and lead, were below the sediment quality guideline levels for aquatic life proposed by EPA (Environmental Protection Agency). Therefore, these two metals could be toxic to aquatic organisms. Significant (P > 0.05) differences were observed among the five fish species for all these metals accumulation. Also, significant (P > 0.05) differences were noticed among these metals accumulation in fish organs. Cadmium showed the least bioaccumulation, while zinc showed the highest bioaccumulation in all the fish species. Though the metal concentration in the different fish tissues was variable, the highest concentration was found in kidney and the lowest in the muscle. Concentrations of these metals in the muscle tissue of all the fish species were well below the consumption safety tolerance in fish set by WHO/FAO, and thus, so far as these metals are concerned, these sewage-fed cultured fishes are safe and suitable for human consumption.  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