全文获取类型
收费全文 | 1359篇 |
免费 | 99篇 |
国内免费 | 276篇 |
专业分类
安全科学 | 190篇 |
废物处理 | 21篇 |
环保管理 | 330篇 |
综合类 | 523篇 |
基础理论 | 385篇 |
环境理论 | 1篇 |
污染及防治 | 109篇 |
评价与监测 | 69篇 |
社会与环境 | 64篇 |
灾害及防治 | 42篇 |
出版年
2023年 | 44篇 |
2022年 | 56篇 |
2021年 | 55篇 |
2020年 | 74篇 |
2019年 | 55篇 |
2018年 | 34篇 |
2017年 | 48篇 |
2016年 | 66篇 |
2015年 | 52篇 |
2014年 | 49篇 |
2013年 | 107篇 |
2012年 | 69篇 |
2011年 | 109篇 |
2010年 | 75篇 |
2009年 | 101篇 |
2008年 | 75篇 |
2007年 | 76篇 |
2006年 | 83篇 |
2005年 | 63篇 |
2004年 | 44篇 |
2003年 | 39篇 |
2002年 | 37篇 |
2001年 | 34篇 |
2000年 | 27篇 |
1999年 | 17篇 |
1998年 | 26篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有1734条查询结果,搜索用时 109 毫秒
61.
Mohamed Edali Ahmed Aboudheir Raphael Idem 《International Journal of Greenhouse Gas Control》2009,3(5):550-560
New comprehensive numerically solved 1D and 2D absorption rate/kinetics models have been developed, for the first time, to interpret the experimental kinetic data obtained with a laminar jet apparatus for the absorption of carbon dioxide (CO2) in CO2 loaded mixed solutions of mixed amine system of methyldiethanolamine (MDEA) and monoethanolamine (MEA). Three MDEA/MEA weight ratios ranging from 27/03 to 23/07, over a concentration range of 2.316–1.996 kmol/m3 for MDEA and of 0.490–1.147 kmol/m3 for MEA were studied. The models take into account the coupling between chemical equilibrium, mass transfer, and the chemical kinetics of all possible chemical reactions involved in the CO2 reaction with MDEA/MEA solvent. The partial differential equations of the 1D model were solved by two numerical techniques; the finite difference method (FDM) based on in-house coded Barakat–Clark scheme and the finite element method (FEM) based on COMSOL software. The FEM comprehensive model was then used to solve the set of partial differential equations in the 2D cylindrical coordinate system setting. Both FDM and FEM produced very accurate results for both the 1D and 2D models, which were much better than our previously published simplified model. The reaction rate constant obtained for MEA blended into MDEA at 298–333 K was kMEA = 5.127 × 108 exp(−3373.8/T). In addition, the 2D model, for the first time, has provided the concentration profiles of all the species in both the radial and axial directions of the laminar jet, thereby enabling an understanding of the correct sequence in which the reaction steps involved in the reactive absorption of CO2 in aqueous mixed amines occur. 相似文献
62.
63.
石墨炉法测定铅的基体改进剂的选择 总被引:9,自引:0,他引:9
通过一系列实验,选择了石墨炉法测定铅的最佳基体改进剂,并确定了使用该基体改进剂的最佳灰化温度和原子化温度。 相似文献
64.
Z. Zlatev I. Dimov Tz. Ostromsky G. Geernaert I. Tzvetanov A. Bastrup-Birk 《Environmental Modeling and Assessment》2001,6(1):35-55
In order to help guide air pollution legislation at the European level, harmful air pollution effects on agriculture crops and the consequent economic implications for policy have been studied for more than a decade. Ozone has been labeled as the most serious of the damaging air pollutants to agriculture, where growth rates and consequently yields are dramatically reduced. Quantifying the effects has formed a key factor in policymaking. Based on the widely held view that AOT40 (Accumulated exposure Over Threshold of 40 ppb) is a good indicator of ozone-induced damage, the Danish Eulerian Model (DEM) was used to compute reduced agriculture yields on a 50 km×50 km grid over Europe. In one set of scenarios, a ten year meteorological time series was combined with realistic emission inventories. In another, various idealized emission reduction scenarios are applied to the same meteorological time series. The results show substantial inter-annual variability in economic losses, due in most part to meteorological conditions which varied much more substantially than the emissions during the same period. It is further shown that, taking all uncertainties into account, estimates of ozone-induced economic losses require that a long meteorological record is included in the analysis, for statistical significance to be improved to acceptable levels for use in policy analysis. In this study, calculations were made for Europe as a whole, though this paper presents results relevant for Denmark. 相似文献
65.
The long-term water quality monitoring program implemented by the Massachusetts Water Resources Authority in 1992 is extensive
and has provide substantial understanding of the seasonality of the waters in both Boston Harbor and Massachusetts Bay and
the response to improvements in effluent quality and offshore transfer of the effluent in September 2000. The monitoring program
was designed with limited knowledge of spatial and temporal variability and long-term trends within the system. This led to
an extensive spatial and temporal sampling program. The data through 2003 showed high correlation within physical parameters
measured (e.g., salinity, dissolved oxygen) and in biological measures such as chlorophyll fluorescence. To address the potential
sampling redundancies in the measurement program, an assessment of the impact of reduced levels of monitoring on the ability
to make water quality decisions was completed. The optimization was conducted by applying statistical models that took into
account whether there was evidence of a seasonal pattern in the data. The optimization used model survey average readings
to identify temporal fixed effects, model survey-average-corrected individual station readings to identify spatial fixed effects,
corrected the individual station readings for temporal and spatial fixed effects and derived a correlation model for the corrected
data, and applied the correlation model to characterize the correlation of annual average readings from reduced monitoring
programs with true parameter levels. Reductions in the number of sampling stations were found less detrimental to the quality
of the data for annual decision-making than reductions in the number of surveys per year, although there is less of a difference
in this regard for dissolved oxygen than there is for chlorophyll. The analysis led to recommendations for a substantially
lower monitoring effort with minimal loss of information. The recommendation supported an annual budget savings of approximately
$183,000. Most of the savings was from fewer surveys as approximately $21,000 came from the reduction in the number of stations
monitored from 21 to 7 and associated laboratory analytical costs. 相似文献
66.
Nabil Semmar Maurice Jay Muhammad Farman Maurice Roux 《Environmental Modeling and Assessment》2008,13(1):17-33
The quantitative assessment of plant diversity and its monitoring with time represent a key environmental issue for management
and conservation of natural resources. Assessment of plant diversity could be based on chemical analyses of secondary metabolites
(e.g. flavonoids, terpenoids), because of the substantial quantitative and qualitative between-individual variability in such
compounds. At a geographical scale, the plant populations become widely dispersed, and their monitoring from numerous routine
individual analyses could become restricting. To overcome such constraint, this study develops a multivariate calibration
model giving the relative frequency of a particular taxon from a simple high-performance liquid chromatography (HPLC) analysis
of a plant mixture. The model was built from a complete set of mixtures combining different taxons, according to an experimental
design (Scheffé’s matrix). For each mixture, a reference HPLC pattern was simulated by averaging the individual HPLC profiles
of the constitutive taxons. The calibration models, based on Bayesian discriminant analysis (BDA), gave statistical relationships
between the contributions of each taxon in mixtures and reference HPLC patterns of these mixtures. Finally, these models were
validated on new mixtures by using outside plants. This new biodiversity survey approach is illustrated on four chemical taxons
(four chemotypes) of Astragalus caprinus (Fabaceae). The more differentiated the taxon, the better predicted its contributions (in mixtures) were by BDA calibration
model. This new approach could be very useful for a global routine survey of plant diversity. 相似文献
67.
水安全及城市水安全研究进展与趋势 总被引:2,自引:1,他引:1
归纳和总结国内外水安全及城市水安全相关研究实践及其所用的评价指标体系,并对几种常用模型与方法的应用情况及其各自的特点进行分析,针对目前水安全及城市水安全研究中存在的主要问题,指出水安全及城市水安全进一步研究的方向:从自然、生态环境、社会经济、人文4个基本方向,以系统性、持续性、动态性和层次性4个特征为基础,分析水安全及城市水安全的概念与内涵;根据研究区域特征及其主要水安全问题建立评价指标体系;以研究者对各个模型的理解程度及驾驭能力为准则选用或改造现有模型与方法;针对加强城市应急水源地建设、突发性水安全事件应急预案、湿润地区水安全等问题开展研究。 相似文献
68.
The measurement of the bed shear stress along vegetated river beds is essential for accurately predicting the water level, velocity and solute and sediment transport fluxes in computational hydroenvironmental models. Details are given herein of an experimental and theoretical study to determine the bed boundary shear stress along vegetated river beds introducing a novel field measuring method, namely the FliessWasserStammtisch (FST)-hemispheres. Although investigations have been conducted previously for sedimentary channels using the FST-hemispheres, this preliminary study is thought to be the first time that such hemispheres have been used to investigate the bed shear stresses in vegetated channels. FST-hemispheres were first developed by Statzner and Müller [1989. Standard hemispheres as indicators of flow characteristics in lotic benthos research. Freshwater Biology 21, 445-459] to act as an integrated indicator of the gross hydrodynamic stresses present near the bed. Test and validation data were found to be at least of the same order of magnitude for the stresses predicted from literature for sedimentary channels, with this study establishing the commencement of a database of calibrated FST-hemisphere laboratory data for vegetated channel beds. In a series of experiments, depths ranging from 0.1 to 0.28m were considered, equating directly to comparable conditions in small rivers or streams. The results of this study provide a basis for enabling the FST-hemispheres to be used to evaluate the boundary shear stress for a wider range of applications in the future, including vegetated river beds. 相似文献
69.
Milan Stra
kraba 《Ecological modelling》2001,140(3)
Based on cybernetic categories of natural control mechanisms, four generations of ecosystem models are distinguished: feed-forward, feedback, self-adaptation and self-organization models. The analysis of the natural control mechanisms in aquatic ecosystems suggests that different processes are controlled in different ways, and, although the four mechanisms were identified in historical sequence, they all operate simultaneously. The concept of self-organization of an ecosystem is introduced and specified for a model of an aquatic pelagic ecosystem. The concept of the ecosystem as a multilayer, multigoal and multiechelon hierarchical system with hierarchy of the levels of biological organization is also introduced. 相似文献
70.
针对我国当前广泛使用的2种高速公路噪声预测模型《06规范》预测模型与《09导则》预测模型在预测时比较研究,重点利用环境现状监测数据分别对2种模型验证与对比分析.结果表明,2种模型预测值与实测值相差3dB ~5dB,车流量> 300辆/h,《09导则》更接近实测值;在夜间车流量<300辆/h,《06规范》更接近实测值,2种模型结合采用《06规范》计算的车速,距离衰减考虑车流量的大小,在此基础上应用《09导则》,预测结果与实测值更为接近. 相似文献