全文获取类型
收费全文 | 774篇 |
免费 | 62篇 |
国内免费 | 88篇 |
专业分类
安全科学 | 85篇 |
废物处理 | 10篇 |
环保管理 | 201篇 |
综合类 | 309篇 |
基础理论 | 128篇 |
污染及防治 | 44篇 |
评价与监测 | 86篇 |
社会与环境 | 41篇 |
灾害及防治 | 20篇 |
出版年
2024年 | 3篇 |
2023年 | 15篇 |
2022年 | 14篇 |
2021年 | 28篇 |
2020年 | 30篇 |
2019年 | 28篇 |
2018年 | 26篇 |
2017年 | 26篇 |
2016年 | 40篇 |
2015年 | 30篇 |
2014年 | 50篇 |
2013年 | 58篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 44篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 50篇 |
2006年 | 49篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有924条查询结果,搜索用时 625 毫秒
631.
632.
Water quality criteria were developed for delivery waters to Everglades National Park. The park receives a minimum of 12.34 m3/sec (315,000 acre-ft/yr) of water from controlled sources external to its boundary. These waters often originate from areas that are or potentially are impacted from urban and agricultural developments. When, in 1970, the U.S. Congress guaranteed minimum water deliveries to Everglades National Park, it also required that these waters be of good quality.The Everglades National Park water quality data base was analyzed from 1970 to 1978 at both in-park and water delivery sites to determine the current level of delivery water quality and to select representative delivery sites. It was found that current delivery water quality was sufficiently high to be adopted as criteria against which future water quality could be compared. From the delivery sites S-12C and L-67A all data were combined from 1970–1978 for 36 parameters including macronutrients, heavy metals, and field parameters such as DO, pH, and specific conductance. Mean concentrations and upper limits were computed and tabulated for comparison during future monitoring programs. These criteria were subsequently adopted through a joint memorandum of agreement between the U.S. Army Corps of Engineers, South Florida Water Management District and the U.S. National Park Service. 相似文献
633.
Bruce W. Lium W. Thomas Shoaf 《Journal of the American Water Resources Association》1980,16(2):359-360
ABSTRACT: Nine samples, each with different kinds and numbers of algae, were filtered at five pressures from 5 to 75 pounds per square inch and the amounts of chlorophylls a and b were measured. Pressures in the range tested had no effect on the measured amounts. 相似文献
634.
我国的危险化学品区域风险评估研究工作起步较晚,针对危险化学品泄漏入海的方法研究较少。现有区域风险评估方法中评估对象多为单一风险因素,存在着未全面考虑研究区域内其他风险源和敏感资源等综合影响的不足。在结合国内外研究进展现状的基础上,强化与相关技术方法的衔接,建立了综合考虑危险化学品危险性和区域风险承受力等因素的危险化学品泄漏入海区域风险评估方法工作,并选择天津市XX企业开展方法案例应用。本研究能够为科学合理划分危险化学品泄漏区域海洋环境风险等级提供技术支撑,为开展危险化学品泄漏入海风险防范和修复评估等工作提供决策依据。 相似文献
635.
636.
Numerical Simulation of Interaction of the Heavy Gas Cloud with the Atmospheric Surface Layer 总被引:3,自引:0,他引:3
The numerical time-dependent three-dimensional model [Kovalets, I.V. and Maderich, V.S.: 2001, Int. J. Fluid Mech. Res. 30, 410–429] of the heavy gas dispersion in the atmospheric boundary layer has been improved by parameterizing momentum and
heat fluxes on the surface of Earth using Monin–Obukhov similarity theory. Three parameterizations of heat exchange with the
surface of Earth were considered: (A) formula of Yaglom A.M. and Kader B.A. [1974, J. Fluid Mech. 62, 601–623] for forced convection, (B) interpolation formula for mixed convection and (C) similarity relationship for mixed
convection [Kader, B.A. and Yaglom, A.M.: 1990, J. Fluid Mech. 212, 637–662]. Two case studies were considered. In the first study based on experiment of Zhu et al., J. Hazard Mater 62, 161–186], the interaction of an isothermal heavy gas plume with an atmospheric surface layer was simulated. It was found
that stable stratification in the cloud essentially suppresses the turbulence in the plume, reducing the turbulent momentum
flux by a factor of down to 1/5 in comparison with the undisturbed value. This reduction essentially influences velocities
in the atmospheric boundary layer above the cloud, increasing the mean velocity by a factor of up to 1.3 in comparison with
the undisturbed value. A simulation of cold heavy gas dispersion was carried out in the second case based on field experiment
BURRO 8. It was shown that both forced and free convections under moderate wind speeds significantly influence the plume.
The relative rms and bias errors of prediction the plume’s height were σH ≈ 30% and ɛH = − 10%, respectively, for parameterization B, while for A and C the errors were σH ≈ 80% and ɛH ≈ − 65%. It is therefore advised to use the simple parameterization B in dense gas dispersion models. 相似文献
637.
638.
Water samples taken at three depth layers from the offshore oligotrophic Cretan Sea were analyzed for ultraphytoplankton size fractionation using different methods: (a) sequential filtration on filters of pore size 5, 1 and 0.2 m, (b) separate filtration using filters 5 and 0.2 m as well as 1 and 0.2 m and (c) direct filtration on 0.2 m filters after staining of the samples with DAPI. Total abundance of photosynthetic organisms as well as the abundance of different groups such as flagellates and cyanobacteria measured by means of sizing after DAPI staining were significantly higher than those obtained by the other methods. This indicates that although there were no significant differences between the estimates provided by the separate and sequential filtration, both these methods underestimated total abundance by at least 25–50%. The estimates for the size fractions were also found to range from relatively imprecise to completely unreliable depending on the group and the size range. Although size fractionation through direct observation after staining largely depends on the expertise of the observer, this study suggests that it may provide more informative estimates than the other two methods. Although it is difficult to generalize the results of this study in a global context, the paper provides strong indications on the limitations of the sequential and separate methods for size fractionation of photosynthetic organisms and implies that their results are likely to be less accurate than is presently believed. 相似文献
639.
A Comparison of Three Methods to Collect Submerged Aquatic Vegetation in a Shallow Lake 总被引:1,自引:0,他引:1
Rodusky AJ Sharfstein B East TL Maki RP 《Environmental monitoring and assessment》2005,110(1-3):87-97
Two boat-based and one in-water sampling method have been used to collect submerged aquatic vegetation (SAV) as part of a
long-term monitoring program in Lake Okeechobee, Florida, USA. The boat-based methods consisted of collecting SAV with a ponar
dredge, used only to collect Chara, and an oyster tongs-like rake apparatus, used to collect all SAV. The in-water method involved use of a 0.5 m2 PVC quadrat frame deployed by a diver. During summer 2002, SAV biomass samples were collected using all three methods at
various sites in the lake to compare between-methods sampling precision. Sites used for these comparisons were selected based
on plant type, plant density and sediment type. Statistical comparisons indicated that there were significant (p ≤ 0.05) biomass differences in 8 of 15 possible pairwise comparisons between sampling method biomass means. In four of the
eight comparisons, significantly higher biomass mean values were obtained using the quadrat frame. In three of the remaining
four comparisons, significantly higher biomass mean values were obtained with the rake apparatus. For the fourth comparison,
a significantly higher biomass mean value was obtained with the ponar dredge. Three of the four relationships between SAV
biomass collected by the rake and the quadrat and the rake and the quadrat/ponar dredge were statistically significant, linear
and explained between 67 and 78% of the biomass variability. There were no significant differences between regression coefficients
or elevations for these relationships, therefore these regressions estimated the same population regression. The population
regression coefficient was 0.95, suggesting that the quadrat and ponar over-sampled relative to the rake, but the amount of
this over-sampling was very small. Since there was no consistent pattern in the sampling method which yielded the significantly
different biomass values and there were no significant differences in sampling precision across a range of plant species,
plant densities and two sediment types, the boat-based rake method appears to be a suitable replacement for the previously
used ponar dredge and quadrat methods, when in-lake measurements are not practical. 相似文献
640.
Edward A. Parson 《Environmental Modeling and Assessment》1997,2(4):267-279
Practice and research in assessment of global environmental change are dominated by two conventional assessment methods, formal models and expert panels. Models construct a representation of biophysical and socioeconomic components of a policy issue, to project future trends or consequences of interventions. Panels articulate consensus views of policyrelevant knowledge through deliberations among selected experts. These methods make valuable contributions, but are weak in addressing certain kinds of knowledge needs that are typical of globalchange issues. To address these needs, a set of novel assessment methods is proposed that combine elements of representation and deliberation. These methods, of which policy exercises, simulationgaming, and scenario exercises are examples, involve human participants in structured relevant decision and task settings. Relative to models and panels, these methods can more readily incorporate diverse perspectives, can integrate across broader collections of knowledge domains, and can both encourage creative insights and innovations, and provide tests of their relevance and practicality. Risks of bias, and of overconfident generalization from unique experiences, are effectively mitigated by critical debriefings, and appear no more severe than corresponding risks in conventional assessment methods, or in policymakers generalizations from historical experience. While serious development and implementation challenges remain, early experience suggests that these methods can offer useful ideas and insights for policymaking that are not available through other means. 相似文献