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881.
Russian Journal of Ecology - 相似文献
882.
Jeroen C. van den Bergh 《Regional Environmental Change》2001,2(1):13-23
This article provides a short overview of the main themes of ecological economics (EE). It is argued that EE provides a platform
that fosters multidisciplinary environmental research by bringing together the core contributing disciplines – economics and
ecology. In addition, EE is regarded as a pluralistic approach to environmental research that can be set opposite to, and
has indeed developed as a response to, traditional environmental and resource economics. A comparison of the two fields is
presented to clarify the essential differences between them. In addition, specific themes are examined in more detail. These
include: sustainable development; the growth debate; international trade; dynamic processes; and behaviour and policy.
Electronic Publication 相似文献
883.
The geysers panic grass [Dichanthelium lanuginosum Spellenberg var. thermale (Bol.) Spellenberg or DILA] is exclusively associated with surface geothermal manifestations in Sonoma County, California,
USA (38°46′N, 122°38′W). Steam extraction by power plants could alter the subsurface distribution of heat and water to the
site, potentially impacting subpopulations of this rare plant. The purpose of this study was to use demographic monitoring
to determine: (1) temporal and spatial patterns of soil temperature in relation to the distribution of established DILA individuals
at Little Geysers, (2) in situ response of experimental populations of DILA to spatial variations in soil temperature, and
(3) habitat requirements of DILA as an indicator of its tolerance to variations in surficial geothermal features. Thermocouple
transects and a datalogger provided data for characterizing the spatial and temporal patterns of soil temperature in four
microhabitats (fumarole, DILA stand, Andropogon stand, and cleared). Experimental populations were established by precisely sowing and monitoring DILA seeds in these microhabitats.
The results indicated that spatial and temporal variations in soil temperature had significant effects on the processes of
germination, growth, survivorship, and reproduction, thus producing a readily observed metapopulation patch dynamic in relation
to geothermal activity. Seasonal depressions of soil temperature near the fumaroles by cold air and prolonged rainfall events
also promoted the emergence and survival of DILA seedlings in a microhabitat that was previously too hot to occupy. Over longer
periods of time, DILA metapopulation dynamism reflected climatic and geothermal variation. Drought years inhibited germination
for lack of water, but more importantly for the lack of requisite soil temperature depressions in the fumarole microhabitat.
Wet years promoted subpopulation expansion into transition areas that were once too hot and dry. There have also been shifts
in the underground distribution of steam into areas distant from known geothermal features. The demographic responses of DILA
to spatial and temporal variations in soil temperature indicate that heat is an absolutely essential component of the steam
resource. In its absence, germination, seeding survivorship, growth, and maturation are significantly inhibited even if soil
conditions are favorable and potential competitors are controlled. Ultimately, persistence of the species depends on maintaining
the ecosystem dynamic of colonization and extirpation in response to variations in surficial geothermal features over long
spatial and temporal scales. This should shift management perspective from its narrow focus on individual plants to a wider
focus on monitoring the essential habitat component of steam. 相似文献
884.
Many financial time series exhibit irregular behaviour. Economic theory suggests that this irregular behaviour might be due to the existence of nonlinear dependence in the markets. Thus, economic time series are governed by nonlinear dynamics.The purpose of this paper is to investigate price behaviour in the London Metal Exchange market. Thus, this study will test the two most attractive nonlinear models—long memory and chaos—on six metal commodities to ascertain which model is consistent with the observed metal price nonlinear dynamics.Application of long memory and chaos analysis provides new approaches for assessing the behaviour of metal prices. We identified, in tin, a case of chaos. Our empirical results in the case of aluminium support the long memory hypothesis. A short memory model explains the underlying processes of the nickel and lead returns series, while zinc returns reflect an anti-persistent process. To our knowledge, this is one of the first attempts to apply long memory and chaos analysis in the evaluation of the behaviour of metal prices. 相似文献
885.
采用曝气生物滤池工艺对含氟苯酚工业废水进行处理研究,主要考察了气水比、水力负荷、进水pH对处理效果的影响。氟苯酚和可吸附有机氟去除率随着气水比升高而增大,但气水比达到6∶1后又降低,最佳气水比为6∶1。随着水力负荷增大,有机物去除率减小,确定最佳水力负荷为0.58 m3/(m2.h)。进水pH在5.0~9.0范围内,BAF对氟苯酚的去除率都在90%以上,当pH达到9.5时去除率急剧降低到30%左右。当进水浓度为40 mg/L,气水比为6∶1,水力负荷为0.58m3/(m2.h),pH 6.5,出水效果稳定,出水氟苯酚、可吸附氟代有机物、氟离子含量均达到了《污水综合排放标准》(GB8978-96)一级标准。氟苯酚生物降解符合一级动力学。 相似文献
886.
The impacts of production disruption in Remanufacturing/Manufacturing (R/M) integrated supply chain on the sales and the methods of production disruption management were studied. A system dynamics model for the R/M integrated supply chain with production disruption was improved by system dynamics methodology. The numerical examples were shown to illustrate the simulation results. The impacts of different recovery times of production disruption on the sales were presented. In order to mitigate the disruption risks and ensure the sales at the needed sales ratio, the methods for setting multi-echelon inventory levels before the occurring of the production disruption and the methods for making back-up plans after the production disruption occurs were given. 相似文献
887.
根据对城市地震次生灾害发生机理的分析,绘制了地震次生灾害演化的因果回路图和存量流量图。在此基础上借助系统动力学仿真软件Vensim PLE,对城市地震次生灾害演化过程建立了系统动力学模型,并进行了模型验证及仿真,得出了不同防震抗灾能力下城市地震次生灾害可能造成的损失情况,为城市防震救灾工作提供参考。 相似文献
888.
889.
Radon-222 and carbon dioxide concentrations have been measured during several years at several points in the atmosphere of an underground limestone quarry located at a depth of 18 m in Vincennes, near Paris, France. Both concentrations showed a seasonal cycle. Radon concentration varied from 1200 to 2000 Bq m−3 in summer to about 800-1400 Bq m−3 in winter, indicating winter ventilation rates varying from 0.6 to 2.5 × 10−6 s−1. Carbon dioxide concentration varied from 0.9 to 1.0% in summer, to about 0.1-0.3% in winter. Radon concentration can be corrected for natural ventilation using temperature measurements. The obtained model also accounts for the measured seasonal variation of carbon dioxide. After correction, radon concentrations still exhibit significant temporal variation, mostly associated with the variation of atmospheric pressure, with coupling coefficients varying from −7 to −26 Bq m−3 hPa−1. This variation can be accounted for using a barometric pumping model, coupled with natural ventilation in winter, and including internal mixing as well. After correction, radon concentrations exhibit residual temporal variation, poorly correlated between different points, with standard deviations varying from 3 to 6%. This study shows that temporal variation of radon concentrations in underground cavities can be understood to a satisfactory level of detail using non-linear and time-dependent modelling. It is important to understand the temporal variation of radon concentrations and the limitations in their modelling to monitor the properties of natural or artificial underground settings, and to be able to assess the existence of new processes, for example associated with the preparatory phases of volcanic eruptions or earthquakes. 相似文献
890.
This paper presents model predictions obtained with the CFD tool FLACS for hydrogen releases and vented deflagrations in containers and larger enclosures. The paper consists of two parts. The first part compares experimental results and model predictions for two test cases: experiments performed by Gexcon in 20-foot ISO containers (volume 33 m3) as part of the HySEA project and experiments conducted by SRI International and Sandia National Laboratories in a scaled warehouse geometry (volume 45.4 m3). The second part explores the use of the model system validated in the first part to accidental releases of hydrogen from forklift trucks inside a full-scale warehouse geometry (32 400 m3). The results demonstrate the importance of using realistic and reasonably accurate geometry models of the systems under consideration when performing CFD-based risk assessment studies. The discussion highlights the significant inherent uncertainty associated with quantitative risk assessments for vented hydrogen deflagrations in complex geometries. The suggestions for further work include a pragmatic approach for developing empirical correlations for pressure loads from vented hydrogen deflagrations in industrial warehouses with hydrogen-powered forklift trucks. 相似文献