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排序方式: 共有1426条查询结果,搜索用时 281 毫秒
411.
Jia-Yeong Ku Huiting Mao Kesu Zhang Kevin Civerolo S. Trivikrama Rao C. Russell Philbrick Bruce Doddridge Richard Clark 《Environmental Fluid Mechanics》2001,1(2):209-233
This paper examines the effects of two different planetary boundary-layer (PBL) parameterization schemes – Blackadar and Gayno–Seaman – on the predicted ozone (O3) concentration fields using the MM5 (Version 3.3) meteorological model and the MODELS-3 photochemical model. The meteorological fields obtained from the two boundary-layer schemes have been used to drive the photochemical model to simulate O3 concentrations in the northeastern United States for a three-day O3 episodic period. In addition to large differences in the predicted O3 levels at individual grid cells, the simulated daily maximum 1-h O3 concentrations appear at different regions of the modeling domain in these simulations, due to the differences in the vertical exchange formulations in these two PBL schemes. Using process analysis, we compared the differences between the different simulations in terms of the relative importance of chemical and physical processes to O3 formation and destruction over the diurnal cycle. Finally, examination of the photochemical model's response to reductions in emissions reveals that the choice of equally valid boundary-layer parameterizations can significantly influence the efficacy of emission control strategies. 相似文献
412.
应用137Cs示踪技术估算农耕地土壤侵蚀量的定量模型主要有两类径流小区上建立的经验关系式及各种理论模型.文章主要对各种主要模型作了简要介绍,并对各种模型的优点、局限性进行了比较和评价;指出今后在模型的建立和应用中注意的问题. 相似文献
413.
基于道路交通噪声990 h监测数据,对英国CRTN模型中源强计算模型在中国的适用性进行了验证。试验结果表明,理论计算与实测结果之间平均仅相差0.57 dB(A),CRTN源强预测模型在中国可以可靠地预测道路交通噪声。 相似文献
414.
415.
Global Grids from Recursive Diamond Subdivisions of the Surface of an Octahedron or Icosahedron 总被引:8,自引:0,他引:8
Denis White 《Environmental monitoring and assessment》2000,64(1):93-103
In recent years a number of methods have been developed for subdividing the surface of the earth to meet the needs of applications in dynamic modeling, survey sampling, and information storage and display. One set of methods uses the surfaces of Platonic solids, or regular polyhedra, as approximations to the surface of the earth. Diamond partitions are similar to recursive subdivisions of the triangular faces of either the octahedron or icosahedron. This method views the surface as either four (octahedron) or ten (icosahedron) tessellated diamonds, where each diamond is composed of two adjacent triangular faces of the figure. The method allows for a recursive partition on each diamond, creating nested sub-dimaonds, that is implementable as a quadtree, including the provision for a Peano or Morton type coding system for addressing the hierarchical pattern of diamonds and their neighborhoods, and for linearizing storage. Furthermore, diamond partitions, in an aperture-4 hierarchy, provide direct access through the addressing system to the aperture-4 hierarchy of hexagons developed on the figure. Diamond partitions provide a nested hierarchy of grid cells for applications that require nesting and diamond cells have radial symmetry for those that require this property. Finally, diamond partitions can be cross-referenced with hierarchical triangle partitions used in other methods. 相似文献
416.
de Leeuw Frank A. A. M. van Pul W. Addo J. van den Berg Frederik Gilbert Andrew J. 《Environmental monitoring and assessment》2000,62(2):133-145
In the evaluation of potentially adverse effects oforganic chemicals such as pesticides on theenvironment the atmosphere may play an important role.After its release to the atmosphere the chemical willbe transported/dispersed in the atmosphere and finallyit will be removed either by atmospheric-chemicaldestruction or by deposition to the underlying soil orsurface water. In a risk assessment decision supportsystem both ambient concentrations and depositionfluxes must be known to evaluate the risk of directexposure (inhalation) or the risk of soil and watercontamination caused by deposition. This paperdiscusses the use of atmospheric dispersion models insuch risk assessment decision support systems. 相似文献
417.
McCreanor L Tsuji LJ Wainman BC Martin ID Weber JP 《Environmental monitoring and assessment》2008,140(1-3):211-222
Abandoned military sites in northern North America are relics of the Cold War and sources of polychlorinated biphenyls (PCBs).
In the late 1990s, the Canadian federal and provincial governments began the cleanup of the mid-Canada radar line in Ontario,
Canada. The first site to be remediated was Site 050 (Fort Albany First Nation) in 2001; however, the community remains concerned
that contaminants may have moved prior to, during, and after remediation into the Albany River directly adjacent to Site 050.
Thus, the Albany River was monitored (1999, 2001, 2002) during the remediation process to determine if the cleanup itself
further contaminated the aquatic compartment, using leeches (Haemopis spp.) as bioindicators. Few organochlorines were found in leeches at levels higher than the detection limit, aside from PCBs.
Leech data from the present study indicated that PCB levels were significantly higher near Site 050 than the control site
upstream, indicating point source contamination from Site 050. The temporal trend in leech contaminant data indicated an increase
in PCB contaminant load from 1999 (pre-remediation) to 2001 (immediately post-remediation), but this difference was not statistically
significant due to high variances. Nevertheless, logit log-linear contingency modeling did reveal that immediately after cleanup
(2001), contaminants (CBs 99, 118, 128, 156, 170, 183) in leeches were detected significantly more frequent than expected.
When taken together, leech body burden and frequency of detection data suggest that the remediation process itself further
contaminated the aquatic environment, if only temporarily. Lastly, the removal of the terrestrial source of PCBs during remediation
did remove the source of aquatic contaminants in that body burden of contaminants in leeches were significantly lower a year
after cleanup. 相似文献
418.
In this study, we present the application of the passive microwave emission models to snow-cover environment monitoring and
assessment in Northeast China. The study employs the radiative transfer function and strong fluctuation theory to develop
the models. We used the exponential form of a spherical symmetric correlation function to describe random permittivity fluctuations.
From strong fluctuation, we then obtained the phase matrix and extinction coefficients of snow-packs for the spherical symmetric
correlation function. We also used the vector radiative transfer formula for the layer of a random medium by solving Gaussian
quadrature and eigen analysis. By comparing the brightness temperatures at 5, 10.7, 18, and 37 GHz, the modelling results
agreed with experimental data of dry-snow physical parameters as measured in the fieldwork. 相似文献
419.
420.
南京市臭氧、VOCs和PANs污染特征及变化趋势 总被引:1,自引:0,他引:1
对2013—2016年基于国家环境空气质量监测站以及省建大气多参数站所获取的南京市O_3、NO_2、CO、VOCs、PANs观测结果进行综合评价,结果表明:2016年南京市O_3第90百分位日最大8 h平均质量浓度比2013年上升33.3%,超标天数中O_3引起的超标占比增至32.0%。南京市区大气中非甲烷总烃冬季浓度高于夏季,含氧挥发性有机物则与之相反;在5—9月,含氧挥发性有机物组分在日变化过程中出现峰值的时间先后顺序依次为醚、醛、酮类,且O_3和过氧乙酰硝酸酯(PANs)生成存在有一定的线性关系。VOCs/NOx比值表明南京市处于VOCs控制区,因此对NO_2浓度下降不敏感,植物源挥发性有机物连续3年上升,夏季大气光化学反应活性未显著下降,这些现象是城市O_3浓度维持在较高水平的重要因素。 相似文献