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   363篇
  免费   3篇
  国内免费   10篇
安全科学   3篇
废物处理   18篇
环保管理   48篇
综合类   52篇
基础理论   76篇
环境理论   1篇
污染及防治   93篇
评价与监测   53篇
社会与环境   32篇
  2023年   4篇
  2022年   27篇
  2021年   21篇
  2020年   7篇
  2019年   14篇
  2018年   11篇
  2017年   17篇
  2016年   18篇
  2015年   13篇
  2014年   14篇
  2013年   39篇
  2012年   11篇
  2011年   20篇
  2010年   16篇
  2009年   20篇
  2008年   21篇
  2007年   10篇
  2006年   15篇
  2005年   12篇
  2004年   10篇
  2003年   3篇
  2002年   6篇
  2001年   1篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1992年   2篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1983年   2篇
  1980年   2篇
  1979年   4篇
  1978年   1篇
  1976年   5篇
  1975年   1篇
  1974年   4篇
  1973年   3篇
  1972年   2篇
  1971年   2篇
  1967年   1篇
  1965年   1篇
  1964年   1篇
  1962年   1篇
  1961年   1篇
  1959年   1篇
  1955年   1篇
排序方式: 共有376条查询结果,搜索用时 31 毫秒
341.
A study on the toxicokinetic behavior, metabolism of chlorpropham, and its effect on cytochrome P450 from liver microsomes was carried out in albino rats after a single and consecutive oral administration at 500?mg?kg?1 body weight for 10 and 20 days. Chlorpropham was detected in the blood at 0.08?h (11.43?±?1.72?µg?mL?1) reaching a maximum concentration at 2?h (30.90?±?2.55?µg?mL?1) and a minimum at 48?h (1.95?±?0.20?µg?mL?1) after a single oral administration of 500?mg?kg?1. The absorption rate constant (K a) was 0.66?±?0.48?h?1. The Vd area (18.01?±?2.78?L?kg?1) and t 1/2 β (12.23?±?1.96?h) values suggested a wide distribution and long persistence of the compound in the body, respectively. The higher ClR (0.82?±?0.00?L?kg?1?h?1) compared to ClH (0.18?±?0.02?L?kg?1?h?1) value indicated that a major portion of chlorpropham was excreted through the urine (30%) compared to the faeces (2.81%). Chlorpropham residue was detected in all tissues of rat at 0.25?h while its metabolite, meta-chloroaniline was detected in liver, kidney, heart, lung, and spleen tissue at 0.25?h. Meta-chloroaniline was not detected in skeletal muscle, brain, fat, and stomach tissue at any time of the observation period. Maximum concentrations of chlorpropham and meta-chloroaniline were detected at 2?h (except in the spleen), and minimum concentrations of chlorpropham at 24 (heart, lung, spleen, skeletal muscle, and stomach) and 48?h (liver, kidney, brain, and fat tissue) respectively; and meta-chloroaniline at 24?h (except heart and spleen). The tissue half-life of chlorpropham in rat varied from 3.80 to 11.60?h. Repeated oral administration of chlorpropham at 500?mg?kg?1 for 10 and 20 days caused an induction of the liver microsomal pellet of rat.  相似文献   
342.
The effect of antioxidant rich diet supplements of Spirulina and tamarind fruit pulp at 230 mg kg?1 body weight, separately as well as in combination, on various hematological parameters of Swiss albino mice exposed to fluoride for seven days at daily doses of 190 mg kg?1 body weight and for 90 days at daily doses of 94 mg kg?1 body weight is reported. Compared with controls, fluoride exposure decreased erythrocyte (12%–18%), leukocyte (16%) and platelet counts (7%, only for short-term exposure), hemoglobin (2%–17%) and packed cell volume (2%–14%) in Swiss albino mice reared on standard feed but these were altered little in the diet supplement groups. Fluoride exposure decreased lymphocytes in both standard feed (16%–21%) and diet supplement groups (5%–19%, but only after long-term exposure). Fluoride withdrawal led to recovery of the post-treated mice from long-term exposure. Spirulina alone and also in combination with tamarind fruit pulp was found more effective than tamarind alone in reducing hematological disorders in fluoride treated mice.  相似文献   
343.
The present work deals with the determination of uranium concentrations in drinking and ground water samples by laser fluorimetry and calculation of cumulative, age-dependent radiation doses to humans. The concentrations were found to be between 0.20 ± 0.03 and 64.0 ± 3.6 μg L?1, with an average of 11.1 ± 1.5 μg L?1, well within the drinking water limit of regulatory bodies. The concentrations of uranium increase with depth of water samples collection. The estimated annual ingestion dose due to the intake of uranium through drinking water for all age groups varied between 0.2 and 137 μSv a?1, with an average of 17.3 μSv a?1. The mean annual ingestion dose is 5% of the global average ingestion dose, for infants, marginally higher than for other age group. Most effective dose values were less than 20 μSv a?1.  相似文献   
344.
Five medicinal plants viz. Abelmoschatus moschatus Linn., Clitoria tematea L., Plumbagozeylanica L., Psorolea corylifolia L. and Withania sominifera L. were grown in a polypot experiment in five soils representing coal mine soil, coppermine soil, fly ash, skeletal soil and forest soil with and without mycorrhizal inoculations in a completely randomized block design. Dry matter yield and mycorrhizal root colonization of plants varied both in uninoculated and inoculated conditions. The forest soil rendered highest dry matter due to higher yield of A. moschatus, P. zeylanica and P corylifolia while fly ash showed lowest dry matter without any inoculants. P. cematea were best in coalmine soil and W. sominifera in copper mine soil without mycorrhizal inoculation. The mycorrhiza was found to enhance the dry matter yield. This contributed minimum 0.19% to maximum up to 422.0% in different soils as compared to uninoculated plants. The mycorrhizal dependency was noticed maximum in plants grown in fly ash followed by coal mine soil, copper mine soil, skeletal soil and forest soil. The mycorrhizal response was increased maximum in W. sominifera due to survival in fly ash after inoculation followed by P corylifolia and P cematea. Percent root colonization in inoculated plant was increased minimum of 1.10 fold to maximum of 12.0 folds in comparison to un-inoculated plants . The native mycorrhiza fungi were also observed to colonize 4.0 to 32.0% roots in plants understudy. This study suggests that mycorrhizal inoculation increased the dry matter yield of medicinal plants in all soils under study. It also helps in survival of W. sominifera in fly ash.  相似文献   
345.
Guineagrass (Panicum maximum Jacq.) is an important forage grass of tropical and semi-tropical regions, largely apomictic and predominantly exist in tetraploid form. For molecular breeding work, it is prerequisite to develop and design molecular markers for characterization of genotypes, development of linkage map and marker assisted selection. Hence, it is an important researchable issue to develop molecular markers in those crops where such information is scanty. Among many molecular markers, microsatellites or simple sequence repeat (SSR) markers are preferred markers in plant breeding. Degenerate primers bearing simple sequence repeat as anchor motifs can be utilized in rapid development of SSR markers; however selection of suitable degenerate primers is a prerequisite for such procedure so that SSR enriched genomic library can be made rapidly. In the present study seven degenerated primers namely KKVRVRV(AG)10, KKVRVRV(GGT)5, KKVRVRV(CT)10, KKVRVRV(AAT)6, KKVRVRV(GTG)6, KKVRVRV(GACA)5, and KKVRVRV(CAA)6 were used in amplification of Panicum maximum genomic DNA. Primers with repeat motifs (GGT)5 and (AAT)6 have not reacted whereas (AG)10, (GACA)5 and (CAA)6 highly informative as they have generated many DNA fragments ranging from 250 to 1600 bps as revealed from the results obtained with restriction digestion of recombinant plasmids. Primer with (CT)10 anchor repeat, amplified fragments of high molecular weight where as (GTG)6 primer generated only six bands with low concentration indicating less suitability of these primerin SSR markers development in P maximum.  相似文献   
346.
Cenchrus is an important component of major grass cover of world. Similar to the other major tropical grasses most of the species in genus Cenchrus are also apomictic in nature hence correct and precise identification of accessions and species are problematic and dubious. In the present study 187 decamer oligonucleotide primers were tested for PCR-based DNA amplification of six prominent species of genus Cenchrus. Of these, 32 potential repetitive and polymorphic primers were tested for identification of species-specific markers for C. ciliaris, C. setigerus, C. pennisetiformis, C. prieurri, C. biflorus and C. myosuroides. These primers yielded 51 unique RAPD markers either specific to a species (37) or shared by two or more species (14). Maximum markers were shared between C. ciliaris and C. setigerus confirming theirmore closeness to each other Primers like OPF09, OPF11, OPR15, OPAJ11, OPQ10 and OPAK20 generated strong intense bands can be used on priority in identifying the species from their natural habitat for the development of species-specific core germplasm. Due to apomictic nature this is the prime method of developing cultivars, as morphological characters are largely unable to distinguish them. The level of variation observed clearly suggest RAPD as an appropriate marker for genetic studies and in identifying the lines with species-specific markers for Cenchrus germplasm management activity and also maintaining identity and purity for proprietary reasons.  相似文献   
347.
An attempt was made to desulfurize coals by bacterial means. A strain of Thiobacillus ferrooxidans has been found effective in removing pyritic sulfur and sulfate sulfur from coal. The removal of organic sulfur depends on the sulfur containing organic compounds present in coal. Assuming presence of thiophene in coal, a mixed bacterial culture was isolated from soil using dibenzothiophene as the sole source of carbon. These strains proved effective in removing organic sulfur from coal in addition to some pyritic and sulfate sulfur.Coal treated with bacteria shows an improvement in quality. Apart from the reduction of the sulfur contents, the ash contents of the bacteria treated coals are substantially reduced. The coking property remains unaffected by the bacterial treatment.  相似文献   
348.
Iodine Deficiency Disorders (IDD) are a common health problem prevalent in the wet zone of Sri Lanka with a prevalence of >25 of the population. In comparison, in the dry zone of Sri Lanka IDD occurs in <10 of the population. Seventy soil samples from 14 villages selected on the basis of the incidence of goitre, were collected and analysed for 13 trace elements using ICP-MS. In order to identify any prevailing differences in antecedent chemical environments, soil samples from each pre-selected village were classified into three groups in terms of their geographical location. Among the elements investigated, the total soil concentrations of Rb, Sr, Ba, Mn and Co are lower in the wet zone of Kalutara. In contrast, total soil Rb, Sr, Ba and Mn contents are higher in the dry zone of Anuradhapura. Further soil total Mo and Nb levels are relatively similar in all pre-selected study locations. The high endemic goitre regions (IDD >25 of the population) show low levels of Rb, Sr, Ba, and Mn and higher levels of V, Cr, Co, Ni, Cu, Zn and Pb as compared with moderate and non-goitre areas. Factor analysis was used to exploit the correlation structure present in data and yielded three groups in all cases. This indicated that most transition group elements and iodine are associated with the Mn phase in the low IDD areas whereas iodine shows a high affinity for the organic phase in high IDD regions. The variable distribution of trace elements, therefore, must be due to differences in mobility and capacity for incorporation into the structure of secondary minerals or organic phases.  相似文献   
349.
Duckweed (Lemna minor) a small vascular plant, grows rapidly, is sensitive to a wide variety of toxicants and is easy to culture. A method is described that measures duckweed frond growth, chlorophyll, protein and biomass content as indicator of growth inhibition. The physico-chemical analysis of anaerobically treated distillery effluent revealed high BOD (28,000 mg/l), COD (52,400 mg/l) and dark brown colour (180,000 Co. Pt.). This effluent showed high toxicity to Lemna minor after 96 h of exposure in laboratory condition. EC50 of the fronds for chlorophyll, protein and biomass was found to be 25%, however, the bacterial decolourised effluent showed reduction of BOD (87.50%), COD (84.50%) and colour (76%). Further the toxicity evaluation with Lemna minor showed toxicity reduction up to 63% for all tested parameters. The EC50 noted for chlorophyll, protein and biomass was 100% concentration of decolourised effluent.  相似文献   
350.
Kolleru lake is the largest fresh water lake in the districts of East and West Godavari of Andhra Pradesh, India. Many anthropogenic sources contribute to the heavy metal pollution in the lake and the bioaccumulation of heavy metals in fish helps in assessing the aquatic pollution. Total contents and fractionation of selected heavy metals, viz., Zn, Cu, Cd, Pb, Cr, Ni and Co were measured in sediment sample and three edible fish. The investigation aimed at revealing differences in the accumulation pattern of heavy metals in fish inhabiting sediments characterized by varying metal bioavailability. The metal concentrations were found to be greater than the background concentrations of sediments indicating the anthropogenic origin of metals. Good recovery values were obtained for metal contents in sediments and fish. Large fractions of Zn, Cd and Cu were associated with mobile fraction of sediment and showed greater bioaccumulation in fish whereas Ni and Co were least mobilisable. The results clearly indicate that the fish of Kolleru lake are contaminated with metals and not advisable 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