全文获取类型
收费全文 | 425篇 |
免费 | 43篇 |
国内免费 | 92篇 |
专业分类
安全科学 | 62篇 |
废物处理 | 7篇 |
环保管理 | 92篇 |
综合类 | 214篇 |
基础理论 | 79篇 |
污染及防治 | 17篇 |
评价与监测 | 43篇 |
社会与环境 | 31篇 |
灾害及防治 | 15篇 |
出版年
2023年 | 18篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 20篇 |
2017年 | 12篇 |
2016年 | 17篇 |
2015年 | 26篇 |
2014年 | 21篇 |
2013年 | 28篇 |
2012年 | 31篇 |
2011年 | 26篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 15篇 |
2007年 | 41篇 |
2006年 | 23篇 |
2005年 | 21篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 15篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1970年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 507 毫秒
471.
INTRODUCTION: Aggressive driving encompasses a continuum of behaviors that range from extreme acts, such as shootings, to less severe manifestations, such as arguments and gestures. It is clear from the available data that aggressive driving is not uncommon and very risky. However, little is known about the opinions and practices of drivers. The purpose of this study was to help bridge these gaps. METHODS: The data were gathered by means of a public opinion poll among a representative sample of 1,201 Canadian drivers. Univariate frequency distributions and 95% confidence intervals were calculated and logistic regression and generalized linear latent models were used to summarize the data. RESULTS: It was found that the issue of aggressive driving is a significant one as a considerable percentage of drivers admits to it. The results coming from the logistic regression and the generalized linear latent model suggest that male and younger drivers are more likely to behave aggressively in traffic and that behaving more aggressively is associated with a history of traffic tickets. DISCUSSION: When gauging people's attitudes, opinions, and behaviors, it becomes clear that aggressive driving is a considerable problem. There also seems to be a need for a better understanding of which specific behaviors respondents associate with the generic term "aggressive driving." IMPACT ON INDUSTRY: Results from this study further emphasize the need of increasing the aggressive driving knowledge base. 相似文献
472.
吹扫捕集/气相色谱/质谱法测定水体中54种常见挥发性有机物的研究 总被引:2,自引:0,他引:2
运用吹扫捕集/气相色谱/质谱(P&T/GC/MS)法对水体中54种常见的挥发性有机物(VOCs)进行了测定.结果表明,VOCs的色谱分离情况较好,平均加标回收率为88.5%~117.0%,相对标准偏差为0.71%~8.50%,准确度和精密度均符合有关分析测试的要求;方法检出限为0.10~0.61μg/L,远低于<地表水环境质量标准>(GB 3838-2002)、<生活饮用水卫生标准>(GB3838-2002)及国外相关标准的限值;54种VOCs的线性范围不同,低沸点的VOCs线性范围较宽,高沸点的VOCs的线性范围较窄,因此在分析VOCs样品配制标准工作曲线时,应注意不同沸点VOCs的线性范围. 相似文献
473.
Receptor modeling for source apportionment of polycyclic aromatic hydrocarbons in urban atmosphere 总被引:1,自引:0,他引:1
Singh KP Malik A Kumar R Saxena P Sinha S 《Environmental monitoring and assessment》2008,136(1-3):183-196
This study reports source apportionment of polycyclic aromatic hydrocarbons (PAHs) in particulate depositions on vegetation
foliages near highway in the urban environment of Lucknow city (India) using the principal components analysis/absolute principal
components scores (PCA/APCS) receptor modeling approach. The multivariate method enables identification of major PAHs sources
along with their quantitative contributions with respect to individual PAH. The PCA identified three major sources of PAHs
viz. combustion, vehicular emissions, and diesel based activities. The PCA/APCS receptor modeling approach revealed that the
combustion sources (natural gas, wood, coal/coke, biomass) contributed 19–97% of various PAHs, vehicular emissions 0–70%,
diesel based sources 0–81% and other miscellaneous sources 0–20% of different PAHs. The contributions of major pyrolytic and
petrogenic sources to the total PAHs were 56 and 42%, respectively. Further, the combustion related sources contribute major
fraction of the carcinogenic PAHs in the study area. High correlation coefficient (R
2 > 0.75 for most PAHs) between the measured and predicted concentrations of PAHs suggests for the applicability of the PCA/APCS
receptor modeling approach for estimation of source contribution to the PAHs in particulates. 相似文献
474.
The use of linear programming as a planning tool for determining the optimal long-range development of an urban water supply system was explored. A stochastic trace of water demand was synthesized and used as an input to the model. This permitted evaluating the feasibility of imposing demand restrictions as an effective cost reduction mechanism. The City of Lincoln, Nebraska, was used as the urban model. The fundamental problem was to allocate limited water supplies from several sources to an urban load center to minimize costs and comply with system constraints. The study period covered twenty years, and findings indicate the planning direction for stage development during this period. Sensitivity analyses were performed on cost coefficients and demands. Thirteen sources were included in the initial computations. Conclusions were that linear programming and generated demand traces are useful tools for both short- and long-term urban water supply planning. Lowering peak demands results in long-range development of fewer sources of supply and more economic and efficient use of the supplies developed. 相似文献
475.
代际公平原则与可持续土地利用规划--南京市的实例研究 总被引:3,自引:0,他引:3
但承龙 《中国人口.资源与环境》2004,14(2):99-103
本文首先阐述代际公平优先原则的可持续土地利用规划思路;接着通过设计满足代际公平基本要求的五种规划方案与构建可持续土地利用规划三效益最大化的目标函数相结合的方法进行南京市可持续土地利用规划方案的设计;然后应用多目标线性划模型优化南京市的规划方案;最后对规划方案的效益与公平进行评价,从规划方案规划的结果来看,规划方案基本达到了规划方案设计的要求。 相似文献
476.
Hatzianastassiou N Katsoulis BD Antakis B 《Environmental monitoring and assessment》2007,128(1-3):447-464
In the present study, we investigate the variation of NO
x
(NO + NO2) and O3 concentrations and the relation between the extreme events (episodes) of NO
x
and O3 concentrations and the relevant meteorological conditions in the urban atmosphere of the Athens basin. Hourly data of NO,
NO2 and O3 concentrations from 10 representative monitoring sites located in the Athens basin were used, covering the 10-year time period
from 1994 to 2003. The results of our analysis show that the concentrations of air pollutants differ significantly from one
monitoring site to another, due to the location and proximity of each station to the emission sources. For each site, there
are also significant differences in NO
x
and O3 concentrations from day to day, as well as from month to month and/or from season to season. The annual and seasonal variations
show higher NO values in winter and lower in summer. On the contrary, NO2 and O3 values are higher in summer (photochemical production of O3) and lower in winter. These differences are attributed, to a large extent, to the prevailing synoptic and meteorological
conditions, the most important between them being the wind direction and speed as well as the atmospheric pressure. Our analysis
of the identified 179 extreme NO
x
air pollution events shows that most of them took place under anticyclonic conditions, associated with calm or weak winds
(speed <2.5 ms−1) of mostly southern to southwestern directions, as well as with low air temperatures and intense stable surface atmospheric
conditions. There exists a significant decreasing tendency in NO
x
air pollution episodic events over the 10-year study period, resulting in very few to none events in the period from 2000
to 2003. As far as it concerns the extreme O3 concentrations, 34 air pollution events were identified, occurring under high air temperatures, variable weak winds and intense
solar irradiation. The trends of O3 concentrations are stronger in suburban sites than in urban ones. 相似文献
477.
15MV医用电子直线加速器感生放射性影响分析 总被引:1,自引:0,他引:1
对于电子能量大于10MeV的医用电子直线加速器,每次开机治疗完成后会产生感生放射性,可能对机房工作人员及附近公众产生辐射危害。本文对某医院15MV电子直线加速器运行后感生放射性进行量化,并由此估算可能对周围人员造成的辐射剂量。通过探讨,希望在对加速器产生的感生放射性影响评价时有参考意义。 相似文献
478.
M. H. Diskin J. R. McCarthy 《Journal of the American Water Resources Association》1972,8(6):1144-1156
The properties of an instantaneous unit hydrograph model consisting of two cascades of linear reservoirs in parallel were explored with the aid of an analog computer. By proper choice of the model parameters it is possible to produce two-peaked instantaneous unit hydrographs. The relative magnitudes and locations of the two peaks can be varied by changing the values of the parameters. An example of the use of the analog computer to select the parameters of the model giving the best fit to an observed runoff hydrograph is also included. The analog computer used in the study was the ASTRAC II developed at the University of Arizona. 相似文献
479.
K. P. Radha Krishnan L. T. Fan L. E. Erickson 《Journal of the American Water Resources Association》1973,9(3):455-466
ABSTRACT The problem of estimating missing values in water quality data using linear interpolation and harmonic analysis is studied to see which one of these two methods yields better estimates for the missing values. The data used in this study consisted of midnight values of dissolved oxygen from the Ohio River collected over a period of one year at Stratton station. Various hypothetical cases of missing data are considered and the two methods of supplementing missing values are evaluated using statistical tests. The results indicate that when the percentage of missed data points exceeded ten percent of the total number in the original sample, harmonic analysis usually yielded better estimates for both the regularly and irregularly missed cases. For data that exhibit cyclic variation, examples of which are dissolved oxygen concentration and water temperature, harmonic analysis as a data generation technique appears to be superior to linear interpolation. 相似文献
480.
Robert B. McKusick James M. Kress Peter G. Ashton Walter A. Bunter 《Journal of the American Water Resources Association》1973,9(3):467-484
ABSTRACT The paper presents a systems approach for planning and evaluating alternative plans for resource use incorporating the concepts of multiobjective planning and evaluation (MOPE). The need for multidisciplinary input and strong interagency cooperation in planning for resource use is related to the logical and orderly completion of the planning steps. The paper briefly describes MOPE, emphasizing two important concepts: (1) the relationship of the study problems and objectives to national social objectives, and (2) the display of alternative solutions showing tradeoffs. Several important characteristics of a plan of study which implements MOPE are presented and discussed. A proposed MOPE analytical system is discussed in detail. The MOPE analytical system is divided into eight interdependent subsystems that describe data collection, use, analysis, and results. A linear program (L.P.) model is proposed to analyze the present and future demand relationships for natural resources. The model will also evaluate the interaction of agriculture, forestry, and recreation with the resource base of the basin, considering National Economic Development, Environmental Quality, and Regional Development. 相似文献