全文获取类型
收费全文 | 25526篇 |
免费 | 251篇 |
国内免费 | 208篇 |
专业分类
安全科学 | 679篇 |
废物处理 | 1046篇 |
环保管理 | 3245篇 |
综合类 | 4333篇 |
基础理论 | 6943篇 |
环境理论 | 11篇 |
污染及防治 | 6451篇 |
评价与监测 | 1649篇 |
社会与环境 | 1460篇 |
灾害及防治 | 168篇 |
出版年
2022年 | 212篇 |
2021年 | 184篇 |
2020年 | 164篇 |
2019年 | 187篇 |
2018年 | 334篇 |
2017年 | 356篇 |
2016年 | 522篇 |
2015年 | 427篇 |
2014年 | 671篇 |
2013年 | 1961篇 |
2012年 | 790篇 |
2011年 | 1099篇 |
2010年 | 931篇 |
2009年 | 977篇 |
2008年 | 1109篇 |
2007年 | 1154篇 |
2006年 | 975篇 |
2005年 | 854篇 |
2004年 | 801篇 |
2003年 | 813篇 |
2002年 | 769篇 |
2001年 | 1027篇 |
2000年 | 753篇 |
1999年 | 436篇 |
1998年 | 284篇 |
1997年 | 338篇 |
1996年 | 346篇 |
1995年 | 400篇 |
1994年 | 388篇 |
1993年 | 319篇 |
1992年 | 313篇 |
1991年 | 324篇 |
1990年 | 336篇 |
1989年 | 322篇 |
1988年 | 251篇 |
1987年 | 262篇 |
1986年 | 255篇 |
1985年 | 233篇 |
1984年 | 244篇 |
1983年 | 230篇 |
1982年 | 222篇 |
1981年 | 215篇 |
1980年 | 194篇 |
1979年 | 219篇 |
1978年 | 161篇 |
1977年 | 178篇 |
1975年 | 150篇 |
1974年 | 139篇 |
1973年 | 157篇 |
1972年 | 143篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
971.
Importance Measures (IMs) are used to rank the contributions of components or basic events to the system performance, e.g. its reliability or risk. Most times, IMs are calculated without due account of the uncertainties in the model of the behavior of the system. The objective of this work is to investigate how uncertainties can influence IMs and to develop a method for giving them due account in the corresponding ranking of the components or basic events. The uncertainties considered in this work affect the model parameters values and are assumed to be described by probability density functions. The method for ranking the contributors to the system performance measure is applied to the auxiliary feedwater system of a nuclear pressurized water reactor. 相似文献
972.
Sinkings of fishing vessels, when accompanied by human loss, are accidents which lead to a great social upheaval, especially in the local area where they occur. In order to avoid or reduce these accidents, national governments must include in their legislation for this sector the appropriate safety measures. These resources and their distribution must be assigned in accordance with the needs of the accidentality, this requiring a detailed knowledge of the concentration of accidentality of a country’s fishing sector. In this context, the aim of the present work is twofold: first, to formulate a methodology for the fishing sector of a country, allowing the inequalities in the concentration of sinking accidents to be analysed; and second, to apply this methodology to the Spanish fishing fleet. Thus, two indices are constructed per region and type of fishing, for two variables: fishermen and vessels. Results are obtained both for the concentration of accidents and the associated Lorenz curves. An increase in the inequality in the spatial and functional distribution of these accidents is verified. 相似文献
973.
K. Walha R. Ben Amar P. Bourseau P. Jaouen 《Process Safety and Environmental Protection》2009,87(5):331-335
Tuna cooking juice from a Tunisian tuna-processing unit has a high level of polluting load: chemical oxygen demand (COD) is comprised between 4 and 20 g L−1, nitrogen kjedahl (NK) between 0.6 and 3 g L−1 and dry matter between 120 and 160 g L−1. The juice has thus to be treated before being rejected into the environment. This paper considers the nanofiltration (NF) of these concentrated organic/inorganic mixtures using an AFC 30 (NF) membrane. The work focusses on the effect of organic and inorganic matters on the permeate flux and rejections of these matters. For this purpose, mixtures of salt and organic pollution (COD), used as model solutions, were prepared by the dilution of a typical industrial tuna cooking juice. The permeate flux was found to decrease when salt and organic matter concentrations increase. The recovery rate in organic matter decreases with increasing salt or organic matter content and the recovery rate of salt decreases when the COD concentration increases. 相似文献
974.
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
975.
Most of the mesoscale models use roughness parameters to characterise the ground and to compute the surface stress. As the experimental determinations of the urban roughness parameters are rare and not very reliable, a new methodology based on microscale numerical simulations is presented here and the first results from two-dimensional simulations with different roof shapes are analysed.Firstly, it appears that the roof shape has a large influence : large difference in the Reynolds stress profile and in the roughness sub-layer thickness, enhancement of the exchanges at the roof level by buildings with attic. It also appears that the fetch necessary to obtain a constant flux layer is unrealistic compared to the real spatial homogeneity of quarters in European cities. Consequently, a new parameterisation of the urban ground-induced friction is to be developed without reference to the constant flux layer theory. 相似文献
976.
Claudia Pahl-Wostl Christoph Schlumpf Martin Büssenschütt Andreas Schönborn Jan Burse 《Integrated Assessment》2000,1(4):267-280
Within the CLEAR project a new approach to integrated assessment modelling has been developed for the participatory integrated
assessment of regional climate change involving citizens' focus groups. The climate change decision problem was structured
by focusing separately on climate impacts and mitigation options. The attempt was made to link the different scales of the
problem from the individual to the global level. The abstract topic of climate change was related to options on the level
of a citizen's individual lifestyle. The option of a low energy society was emphasised in order to embed the climate change
decision problem in a wider range of societal concerns. Special emphasis was given to the characterisation and communication
of uncertainties. The chosen approach allows different kinds of uncertainties in one framework to be addressed. The paper
concludes with a summary of the experience made, and recommendations for the use of models in participatory integrated assessments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
977.
Long-Term Relationship between Phosphorus Inputs and Wetland Phosphorus Concentrations in a Northern Everglades Marsh 总被引:3,自引:0,他引:3
Assessments of long-term relationships between changes innutrient inputs and wetland nutrient concentrations can becomplicated by fluctuations in other environmental factors aswell as by problems typical of long-term monitoring data.Consequently, statistical analysisof these types of data sets requirescareful consideration of environmental covariates, potentialbiases in the monitoring design, and irregularities caused bychanges in field sampling protocols. We evaluated therelationship between anthropogenic phosphorus (P) inputs andwater-column total P (TP) concentrations in a northernEverglades marsh by statistically analyzing available datacollected from several sampling programs over the past 20 years(1978–1997). Canal inputs of agricultural runoff contributemost of the P to the marsh and have produced a zone ofenrichment within the marsh during the past few decades.Regression analyses showed that both canal and marsh TPconcentrations increased during the 1980s and then decreased inthe 1990s. However, the statistical relationship between canal Pinputs and marsh TP, while significant, generally was weakexcept for marsh locations adjacent to the canal. Strongerrelationships existed between marsh TP and hydrologic parameterssuch as marsh water depth, which is controlled by changes inweather patterns and marsh management. In particular, dryconditions during the 1980s may have contributed to observedincreases in marsh P concentrations and the movement of a P`front' further into the marsh. Higher rainfall and water depthsand agricultural best management programs initiated during the1990s have been associated with reduced P concentrations incanal waters entering the marsh. While it is anticipated thatthis reduction eventually will result in lower marsh TPconcentrations, this effect is not yet evident, possibly due tointernal loading of P from enriched marsh soils. Our findingsillustrate some of the environmental factors that can complicateattempts to develop empirical relationships between P inputs andwetland P concentrations and to use such relationships to forecast changesin marsh concentrations based on past monitoring data alone. 相似文献
978.
Ali-Khodja H Belaala A Demmane-Debbih W Habbas B Boumagoura N 《Environmental monitoring and assessment》2008,138(1-3):219-231
Total suspended particulate matter and deposition fluxes of particles were investigated in the town of Didouche Mourad which
is located 13 km north of Constantine. Samples of air particulate matter were collected at one site located in the heart of
the town and situated 3 km north of a cement plant. Samples were collected from 2 November 2002 to 28 April 2003 every 3 days
using a high volume air sampler. Sampling intervals were 24 h in all cases. During the same period, samples of dust fallout
were collected at the same site. Samples were collected at 30-day intervals. Lead, chromium, manganese, nickel, copper, cobalt
and cadmium deposition fluxes were measured and both the soluble and insoluble fractions were determined. Furthermore, the
information gathered by this study was correlated with the corresponding hourly weather data provided by a weather station
installed at the study station. The possible sources for dust and trace metals were analyzed by comparing average contributions
of wind aspects to the concentrations and depositions of mass and chemical species with the average frequencies of wind direction.
The mean concentration was 300 μg/m3. The average dust deposition rate through the period of study was 221 mg/(m2.day). Results indicate that anthropogenic sources contribute greatly to trace elements. An exposure assessment to the heavy
metals taking into account the inhalation route and soil dust ingestion was carried out and allowed direct comparison of trace
metal intakes via these routes. 相似文献
979.
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
980.
Bhattacharyya P Mitra A Chakrabarti K Chattopadhyay DJ Chakraborty A Kim K 《Environmental monitoring and assessment》2008,139(1-3):299-306
The present investigation deals with the limnobiotic status of Almatti reservoir from February, 2003 to January, 2005. The
study revealed that, the distribution and population density of zooplankton species depend upon the physico-chemical factors
of the environment. Statistical analysis showed that there exists a significant relation between the biological and non-biological
factors. The benthic fauna constituting the food of fish can be utilized for extensive culture operation so that the nutrients
in the reservoir are not only properly cycled but also serve as a check on further eutrophication. 相似文献