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   2418篇
  免费   18篇
  国内免费   24篇
安全科学   58篇
废物处理   174篇
环保管理   160篇
综合类   219篇
基础理论   496篇
环境理论   3篇
污染及防治   923篇
评价与监测   261篇
社会与环境   156篇
灾害及防治   10篇
  2023年   30篇
  2022年   84篇
  2021年   105篇
  2020年   54篇
  2019年   54篇
  2018年   75篇
  2017年   106篇
  2016年   139篇
  2015年   70篇
  2014年   124篇
  2013年   237篇
  2012年   173篇
  2011年   210篇
  2010年   135篇
  2009年   122篇
  2008年   106篇
  2007年   148篇
  2006年   106篇
  2005年   79篇
  2004年   60篇
  2003年   49篇
  2002年   52篇
  2001年   29篇
  2000年   25篇
  1999年   18篇
  1998年   14篇
  1997年   6篇
  1996年   10篇
  1995年   7篇
  1994年   5篇
  1993年   3篇
  1992年   4篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   3篇
  1986年   2篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1968年   1篇
  1967年   1篇
  1958年   1篇
  1956年   1篇
  1915年   1篇
排序方式: 共有2460条查询结果,搜索用时 15 毫秒
971.
The aim of this study was to analyze the incidence of fungi in the chapel crypt. The MAS 100 was used to monitor the air pollution. The lowest numbers of fungal colonies were isolated at the entrance to the cemetery (2400 CFU/m3). The outside temperature ranged from 24.5oC to 28.1oC, and relative humidity was between 35.3% and 46.4 %. The highest of fungal colonies from air samples at baseline were isolated inside the crypt when coffin was opened (4820 CFU/m3). The temperature in the crypt at baseline varied between 19.6°C and 25.6°C and humidity was between 50.8% and 60.1%. The number of fungal colonies increased significantly at the end of the study. Ten species of fungi were isolated from air samples inside and outside the chapel, and seven species of fungi were isolated on the surface of the exterior and interior of the chapel. Thirteen types/species of fungus were isolated from air samples collected in the crypt; 15 species of fungi were isolated on the walls, surface of the coffin, bones and other objects. Assessment of fungi in the air samples and different surfaces of the crypt, it revealed very high levels of molds in the air samples.

Implications: Assessment of fungi in the air samples and different surfaces of the crypt revealed high levels of molds in the air samples. Fungal numbers within the crypt exceed recommended limits for occupational exposure. Employees working in the crypts should know about these hazards.  相似文献   
972.
ABSTRACT

The annual average concentrations (1986–1997) of the major ions SO4 2-, NO3 -, Cl-, NH4+, Na+, Mg2+, Ca2+, and K+ in precipitation are analyzed for selected EMEP stations. The objective is to determine the ion patterns or typologies in precipitation by principal component analysis (PCA) combined with a cluster analysis. SO4 2- and NO3 - ions are predominant in central and eastern Europe. This area corresponds to high emissions of SO2 and NO2. Sea spray ions are predominant in coastal sites. The soil components show an important contribution in southern Europe, possibly due to the soil dust transported from northern Africa.  相似文献   
973.
Fluoridated salt is an effective method to reduce dental decay in the population at large, in particular in settings where the more frequently used method of fluoridated water is not feasible due to unreliable water supplies. A salient problem of regular dosage and monitoring of fluoride in salt is its variable level at the industrial level. To evaluate the relative advantages of the present monitoring method used in Mexico, samples of domestic fluoridated salt were analysed by two comparative methods to determine their fluoride content. One of the methods employed was the relevant Mexican Offcial Norm (based on an acetic acid, sodium chloride, trans-1,2-diamine, cyclohexane N,N,N',N' tetracetic acid buffer solution) and the other was an alternative electrochemical methodology (based on an acetic acid, sodium chloride, sodium citrate buffer solution). The cost of the chemicals involved and simplicity of the alternative method, along with the equivalent precision of its results, makes it an interesting choice for the large scale analysis of fluoridated salt.  相似文献   
974.
A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha?1 and 5 kg ha?1. Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.  相似文献   
975.
This investigation was undertaken to determine the impact of the insecticides Dursban 480 EC (with organophosphate compound chlorpyrifos as the active ingredient) and Talstar 10 EC (with pyrethroid bifenthrin as the active ingredient) on the respiration activity and microbial diversity in a sandy loam luvisol soil. The insecticides were applied in two doses: the maximum recommended dose for field application (15 mg kg?1 for Dursban 480 EC and 6 mg kg?1 for Talstar 10 EC) and a 100-fold higher dose for extrapolation of their effect. Bacterial and fungal genetic diversity was analysed in soil samples using PCR DGGE and the functional diversity (catabolic potential) was studied using BIOLOG EcoPlates at 1, 3, 7, 14, 28, 56 and 112 days after insecticide application. Five bacterial groups (α, β, γ proteobacteria, firmibacteria and actinomycetes) and five groups of fungi or fungus-like microorganisms (Ascomycota, Basidiomycota, Chytridiomycota, Oomycota and Zygomycota) were analysed using specific primer sets. This approach provides high resolution of the analysis covering majority of microorganisms in the soil. Only the high-dose Dursban 480 EC significantly changed the community of microorganisms. We observed its negative effect on α- and γ-proteobacteria, as the number of OTUs (operational taxonomic units) decreased until the end of incubation. In the β-proteobacteria group, initial increase of OTUs was followed by strong decrease. Diversity in the firmibacteria, actinomycetes and Zygomycota groups was minimally disturbed by the insecticide application. Dursban 480 EC, however, both positively and negatively affected certain species. Among negatively affected species Sphingomonas, Flavobacterium or Penicillium were detected, but Achromobacter, Luteibacter or Aspergillus were supported by applied insecticide. The analysis of BIOLOG plates using AWCD values indicated a significant increase in metabolic potential of microorganisms in the soil after the high-dose Dursban application. Analysis of respiration demonstrated high microbial activity after insecticide treatments; thus, microbial degradation was relatively fast. The half-life of the active insecticide compounds were estimated within the range of 25 to 27 days for Talstar and 6 to 11 days for Dursban and higher doses stimulated degradation. The recommended dose levels of both insecticides can be considered as safe for microbial community in the soil.  相似文献   
976.
To gain a better understanding of the physiology of the herbicide aminocyclopyrachlor in young plants of trumpet flower, the uptake and translocation were evaluated after the application of herbicide. This was determined by treating individual leaves with formulated herbicides plus 14C-aminocyclopyrachlor after the application of the formulated herbicide. This experiment used a randomized experimental design with three replications. In addition, field studies were conducted to assess the effectiveness of foliar applications of aminocyclopyrachlor in association with metsulfuton-methyl. The plant absorbed 20% of the herbicide applied. The translocation percentage did not surpass 5% of the total amount applied. Only 1% of the herbicide applied was translocated to the roots. Rate of 40 + 13 g a.i. 100 L?1 of aminocyclopyrachlor+metsulfuron-methyl was effective to control T. stans.  相似文献   
977.
Abstract

The adsorption of simazine on two fractions of hu‐mic acids of different molecular size was investigated at a pH range of 2.5 to 6.2. The amounts of the herbicide adsorbed decreased with increasing pH for both of the two humic acids fractions used and no adsorption was observed at pH 5.5. The adsorption capacity of fraction I (Mv >100,000) exceeded that of fraction IV (Mv < 4,000) over the entire pH region used. No appreciable changes in the adsorbed amounts were observed after 24 hours.

Continuous flow dialysis techniques were used to determine the extent of binding between simazine and dissolved humic acids. It was observed that 50% and 60% of simazine added were thus removed from the dialysis bags containing humic acids fractions I and IV,respectively. Higher amounts of simazine were adsorbed by the high molecular weight humic fraction. The adsorption processes involve ionic bonds between simazine and humic acids. In addition it is likely that hydrogen bonds and physical forces are also involved in the adsorption of simazine by humic acids.  相似文献   
978.
Mineral phases and their content were determined in attic dust samples collected from 27 houses in the Tikve? Valley, Republic of Macedonia. By using quantitative X-ray diffraction, the principal mineral phases were determined to be the serpentinite group (chrysotile, lizardite) and amphibole group of minerals (ribecite, tremolite, actinolite) present in the attic dust samples from this region which are not common constituents of urban dust. Strong correlations existed between these mineral phases in the dust and those in ores processed at a ferronickel smelter plant situated in this region. Spatial distributions of specific mineral phases were made and were consistent with wind directions and predicted deposition (60–70 %) of dust emitted from the metallurgical plant.  相似文献   
979.
980.
A method based on matrix solid-phase dispersion (MSPD) was developed for quantitative extraction of three organophosphorus pesticides (OPPs) from the Mexican axolotl, Ambystoma mexicanum. The determination was carried out using high- performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection (DAD). The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, fenthion and methyl parathion. The method was validated, yielding recovery values higher than 90%. The precision, expressed as the relative standard deviation (RSD), was less than or equal to 6% in muscle samples at spiking levels of 10 and 5 ppm. Linearity was studied from 15 to 60 ppm for chlorpyrifos and fenthion, and from 7.5 to 30 ppm for methyl parathion. The limits of detection (LODs) were found to be less than or equal to 0.5 ppm.This method was applied to the analysis of samples from a chlorpyrifos-exposed axolotl, demonstrating its use as an analytical tool for toxicological studies.  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