全文获取类型
收费全文 | 20887篇 |
免费 | 195篇 |
国内免费 | 160篇 |
专业分类
安全科学 | 560篇 |
废物处理 | 872篇 |
环保管理 | 2644篇 |
综合类 | 3262篇 |
基础理论 | 5611篇 |
环境理论 | 5篇 |
污染及防治 | 5381篇 |
评价与监测 | 1338篇 |
社会与环境 | 1444篇 |
灾害及防治 | 125篇 |
出版年
2022年 | 180篇 |
2021年 | 181篇 |
2020年 | 130篇 |
2019年 | 182篇 |
2018年 | 286篇 |
2017年 | 293篇 |
2016年 | 451篇 |
2015年 | 301篇 |
2014年 | 478篇 |
2013年 | 1608篇 |
2012年 | 569篇 |
2011年 | 841篇 |
2010年 | 710篇 |
2009年 | 696篇 |
2008年 | 900篇 |
2007年 | 895篇 |
2006年 | 860篇 |
2005年 | 685篇 |
2004年 | 733篇 |
2003年 | 698篇 |
2002年 | 622篇 |
2001年 | 905篇 |
2000年 | 604篇 |
1999年 | 366篇 |
1998年 | 275篇 |
1997年 | 266篇 |
1996年 | 272篇 |
1995年 | 297篇 |
1994年 | 325篇 |
1993年 | 266篇 |
1992年 | 293篇 |
1991年 | 266篇 |
1990年 | 308篇 |
1989年 | 284篇 |
1988年 | 244篇 |
1987年 | 214篇 |
1986年 | 207篇 |
1985年 | 204篇 |
1984年 | 227篇 |
1983年 | 218篇 |
1982年 | 226篇 |
1981年 | 200篇 |
1980年 | 158篇 |
1979年 | 176篇 |
1978年 | 155篇 |
1977年 | 144篇 |
1975年 | 133篇 |
1974年 | 143篇 |
1973年 | 137篇 |
1972年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 819 毫秒
881.
The Effect of Masterbatch Addition on the Mechanical, Thermal, Optical and Surface Properties of Poly(lactic acid) 总被引:1,自引:0,他引:1
F. Byrne P. G. Ward J. Kennedy N. Imaz D. Hughes D. P. Dowling 《Journal of Polymers and the Environment》2009,17(1):28-33
There has been considerable interest in the use of the biodegradable polymer poly(lactic acid) (PLA) as a replacement for
petroleum derived polymers due to ease of processability and its high mechanical strength. Other material properties have
however limited its wider application. These include its brittle properties, low impact strength and yellow tint. In an attempt
to overcome these drawbacks, PLA was blended with four commercially available additives, commonly known as masterbatches.
The effect of the addition of 1.5 wt% of the four masterbatches on the mechanical, thermal, optical and surface properties
of the polymer was evaluated. All four masterbatches had a slight negative effect on the tensile strength of PLA (3–5% reduction).
There was a four fold increase in impact resistance however with the addition of one of the masterbatches. Differential scanning
calorimetry demonstrated that this increase corresponded to a decrease in the polymer crystallinity. However there was an
associated increase in polymer haze with the addition of this masterbatch. The clarity of PLA was improved through the addition
of an optical brightener masterbatch, but the impact resistance remained low. The glass transition and melting temperatures
of PLA were not affected by the addition of the masterbatches, and no change was observed in surface energy. Some delay in
PLA degradation, in a PBS degradation medium at 50 °C, was observed due to blending with these masterbatches. 相似文献
882.
Ibrahim A. Al-Darrab Author Vitae Author Vitae Shiekh I. Ishrat Author Vitae 《Journal of Safety Research》2009,40(3):185-189
Introduction
This paper presents an experimental study in which the effect of three factors (distance between cars, mobile call duration, and time of driving (day or night)) on drivers' reaction time in braking response was investigated.Methods
The experiment was performed in a real driving environment in which 27 male adults between the ages of 22 and 24 years participated. Three levels of the first two factors (i.e., distance between cars and call duration) and two levels of the last factor (i.e., time of driving) were selected to conduct the experimental study. A full factorial design of experiment with 18 treatment combinations and three replicates of each combination were used. Fifty-four trial runs were performed in a random manner and for each run drivers' reaction time in braking response was measured, which served the data for further analysis. Analysis of variance (ANOVA), interaction effect analysis, and various model adequacy tests were carried out using Design Expert software.Results
The results of the study indicated that the most important factor affecting the drivers' reaction time in car braking response was the mobile call duration followed by the time of driving, with a high level of interaction between the two factors. It was also found that the distance between cars did not seem to have a significant effect on the reaction time in braking response. It is to be noted that these response times are expected to be higher under normal driving conditions where awareness of experimental environment is not present.Impact on Industry
The findings of this study would help mobile phone industries in improving safety of mobile phone users in driving environment. 相似文献883.
Turnover potentially leads to a new individual being selected into a work team. This study investigated the safety-specific trust which team members place in their organisation’s selection and induction processes, and related this to the perceived risk from new employees. The research was conducted with teams working in forest harvesting, an occupation which has high-turnover, high risk and a high accident rate. Results indicate that trust in induction processes was negatively correlated with perceived risk from a new employee. Team members also engaged in a number of safety ensuring behaviours when a new individual joined the team, and these were related to the level of perceived risk, and how much they cared about their team members’ safety. It is argued that trust in the safety-specific characteristics of an organisation’s selection and induction process may have negative consequences for safety. 相似文献
884.
D. Ray R. Ravindar Rao A. V. Bhoi A. K. Biswas A. K. Ganguly P. B. Sanyal 《Environmental monitoring and assessment》2000,61(3):387-398
Water Quality Survey of Rohtas district of Bihar was conducted. Samples were collected from differentsources and analysed. 209 samples were collectedfrom 196 villages. Results of water quality surveyidentified the problem areas in respect of high iron,manganese, fluoride, nitrate and brackishness of water in the district. 相似文献
885.
A.J. Wheeler I. Williams R.A. Beaumont R.S. Hamilton 《Environmental monitoring and assessment》2000,65(1-2):69-77
The personal exposure of children aged 9 – 11 years to particulate matter (PM10 and PM2.5) was carried out between January and September 1997 in the London Borough of Barnet. Personal sampling along with home, garden and classroom microenvironmental monitoring was completed for all ten children. Each child was monitored for five days during winter, spring and summer. All children completed daily time activity diaries to provide information on any potential activities that could influence their exposure to particulate matter. Each evening a household activity questionnaire was also completed by the parents. Personal Environmental Monitors were used to sample personal exposure to PM10 and PM2.5. Harvard Impactors were used for the microenvironmental sampling of both size fractions. The children's mean personal exposure concentrations for PM10 during winter, spring and summer were 72, 54 and 35 µg/m3 respectively and for PM2.5 22, 17 and 18 µg/m3 respectively. In order to determine the potential sources of particulate matter, analysis of the Teflon filters has been undertaken. The physical characteristics of the particles have been identified using Scanning Electron Microscopy. The relationships between personal exposure concentrations and the different microenvironments will be discussed. 相似文献
886.
887.
D.S. Lee R.D. Kingdon M.E. Jenkin A. Webster 《Environmental Modeling and Assessment》2000,5(2):105-118
In order to understand relationships between sources and receptors of atmospheric deposition, computer models must be used.
This paper describes a Lagrangian acid deposition model that represents emissions of trace species across Northern Europe.
The chemistry of sulphur dioxide, dimethyl sulphide and hydrogen sulphide is represented and the model tested against estimates
of UK wet and dry deposition. Mean UK wet and dry deposition for the period 1992–1994 was 206 and 145 ktonne S yr-1, respectively. The model predicted wet and dry deposition of 222 and 166 ktonne S yr-1, in good agreement with measurements. The model has been used to examine the sources of deposited S to the UK. For a base
year of 1992, 86% of the UK's SO2 emissions are exported. The S deposition attributable from mainland European sources was 36% of the UK total S deposition,
in good agreement with other UK models but this differs substantially from the calculations of the EMEP model. Natural sources
of S deposition from planktonic emissions of dimethyl sulphide, biological emissions of hydrogen sulphide and non-eruptive
volcanic emissions of sulphur dioxide contributed approximately 1% of the modelled UK S deposition, of which 95% originated
from dimethyl sulphide. The explicit chemical scheme for dimethyl sulphide incorporated into the model showed that 24% of
the resultant deposited S was methane sulphonic acid. Boundary conditions of the model were tested and it was found that initialisation
of sulphur dioxide and sulphate concentrations to representative ambient conditions had a very small effect. The modelled
contribution of UK and European sources to UK S deposition was approximately 40 and 60%, respectively, showing the dramatic
change arising from projected UK SO2 emissions in 2010.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
888.
This article measures the effect of an increase in productivityattributable to an increase in soil organic carbon associated with theincrease in the use of conservation practices in agriculture in theUnited States. Both the direct and indirect effects are calibrated. Theanalytical approach used consists of a dynamic computable generalequilibrium model composed of 14 producing sectors, 10 consumingsectors, seven household categories classified by income, and agovernment. The results suggest that the impact of a change inproductivity is an increase in output over a six year period starting in1998 in field crops. The most significant impact is felt in thelivestock sector. This is because field crops are a major input in theproduction of livestock. The food processing sector also exhibits arelatively large increase because of the increase in inputs of both fieldcrops and livestock. Manufacturing output increases primarily becauseoverall investment rises and most investment utilizes manufacturinggoods. The other producing sectors are generally unaffected by theincrease in agricultural production due to an increase in soil organiccarbon. Coincident with the increase in the production of field cropsis a relatively large decrease in the price of field crops. Othernoticeable price reductions occur in the livestock sector and the foodprocessing sector. For the consuming sectors, the consumption offood and alcohol and tobacco increase but consumption in all of theother sectors remains basically unchanged. Prices in the food andalcohol and tobacco sectors decline by about 1% while theprices in the other sectors remain static. Household welfare increasesin the aggregate by only 0.1% with this increase occurringuniformly across all household categories. Revenue received by thegovernment increases a modest 2% in response to an increase inoutput and, hence, an increase in taxes paid. The results indicate thatthere are significant production benefits for several sectors that can berealized by an increase in the use of conservation practices inagricultural production which, in turn, enhances soil organic carbon.There are a number of policy options available to promote the use ofconservation practices. These include education and technicalassistance, financial assistance, research and development, landretirement, and regulation and taxes. 相似文献
889.
Fernandes C Fontaínhas-Fernandes A Cabral D Salgado MA 《Environmental monitoring and assessment》2008,136(1-3):267-275
Esmoriz–Paramos lagoon is an ecosystem of great ecological importance that is located on the northwest coast of Portugal and
has been degraded as a result of industrial and anthropogenic activities. Concentrations of heavy metals (Cr, Cu, Pb and Zn)
were measured in water, sediment and in tissues (liver and muscle) of Liza saliens, which is the dominant fish from the lagoon. Comparisons between metal concentrations in water and sediments were made with
those in tissues of fish caught at the lagoon. Metals in water were quantified predominantly bound to particulate and equalled
or exceeded the limit of chronic reference values. Metal concentrations in sediments varied among sampled sites. The relative
order of concentrations was “Zn > Cu ∼ Pb > Cr” the same pattern observed for metals in water. Metals in fish tissues showed
higher concentrations in liver (262 mg Cu·Kg−1 and 89 mg Zn·Kg−1) than in muscle (<3 mg Cu·Kg−1 and 26 mg Zn·Kg−1), while Pb and Cr were not detected. These results suggest that Cu and Zn are the metals of major concern in the lagoon.
Mullet detritivorous feeding habits, bioaccumulation pattern and the high sediment metals concentrations relative to the water
suggest that sediments can be the most important source of contamination in this ecosystem. The positive relationship found
between Cu in liver and fish length demonstrates that time of exposure is a crucial factor in bioaccumulation. Condition indices
(K and HSI) in mullets from the lagoon were higher compared to mullets from sea, suggesting abnormal condition in the lagoon
population. We conclude that metals chronic exposure in the lagoon can impose considerable fish stress. The results also show
that the lagoon is an area of environmental concern. 相似文献
890.
Govil PK Sorlie JE Murthy NN Sujatha D Reddy GL Rudolph-Lund K Krishna AK Rama Mohan K 《Environmental monitoring and assessment》2008,140(1-3):313-323
Studies on quantitative soil contamination due to heavy metals were carried out in Katedan Industrial Development Area (KIDA),
south of Hyderabad, Andhra Pradesh, India under the Indo-Norwegian Institutional Cooperation Programme. The study area falls
under a semi-arid type of climate and consists of granites and pegmatite of igneous origin belonging to the Archaean age.
There are about 300 industries dealing with dyeing, edible oil production, battery manufacturing, metal plating, chemicals,
etc. Most of the industries discharge their untreated effluents either on open land or into ditches. Solid waste from industries
is randomly dumped along roads and open grounds. Soil samples were collected throughout the industrial area and from downstream
residential areas and were analysed by X-ray Fluorescence Spectrometer for fourteen trace metals and ten major oxides. The
analytical data shows very high concentrations of lead, chromium, nickel, zinc, arsenic and cadmium through out the industrial
area. The random dumping of hazardous waste in the industrial area could be the main cause of the soil contamination spreading
by rainwater and wind. In the residential areas the local dumping is expected to be the main source as it is difficult to
foresee that rain and wind can transport the contaminants from the industrial area. If emission to air by the smokestacks
is significant, this may contribute to considerable spreading of contaminants like As, Cd and Pb throughout the area. A comparison
of the results with the Canadian Soil Quality Guidelines (SQGL) show that most of the industrial area is heavily contaminated
by As, Pb and Zn and local areas by Cr, Cu and Ni. The residential area is also contaminated by As and some small areas by
Cr, Cu, Pb and Zn. The Cd contamination is detected over large area but it is not exceeding the SQGL value. Natural background
values of As and Cr exceed the SQGL values and contribute significantly to the contamination in the residential area. However,
the availability is considerably less than anthropogenic contaminants and must therefore be assessed differently. The pre-
and post-monsoon sampling over two hydrological cycles in 2002 and 2003 indicate that the As, Cd and Pb contaminants are more
mobile and may expect to reach the groundwater. The other contaminants seem to be much more stable. The contamination is especially
serious in the industrial area as it is housing a large permanent residing population. The study not only aims at determining
the natural background levels of trace elements as a guide for future pollution monitoring but also focuses on the pollution
vulnerability of the watershed. A plan of action for remediation is recommended. 相似文献