全文获取类型
收费全文 | 2599篇 |
免费 | 457篇 |
国内免费 | 356篇 |
专业分类
安全科学 | 886篇 |
废物处理 | 51篇 |
环保管理 | 788篇 |
综合类 | 869篇 |
基础理论 | 299篇 |
污染及防治 | 212篇 |
评价与监测 | 109篇 |
社会与环境 | 57篇 |
灾害及防治 | 141篇 |
出版年
2024年 | 6篇 |
2023年 | 54篇 |
2022年 | 105篇 |
2021年 | 126篇 |
2020年 | 114篇 |
2019年 | 114篇 |
2018年 | 72篇 |
2017年 | 127篇 |
2016年 | 153篇 |
2015年 | 166篇 |
2014年 | 124篇 |
2013年 | 129篇 |
2012年 | 206篇 |
2011年 | 192篇 |
2010年 | 139篇 |
2009年 | 189篇 |
2008年 | 124篇 |
2007年 | 147篇 |
2006年 | 133篇 |
2005年 | 119篇 |
2004年 | 79篇 |
2003年 | 107篇 |
2002年 | 101篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 62篇 |
1998年 | 50篇 |
1997年 | 34篇 |
1996年 | 44篇 |
1995年 | 27篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有3412条查询结果,搜索用时 15 毫秒
981.
Mark E. Jensen Roland L. Redmond Jeff P. Dibenedetto Patrick S. Bourgeron Iris A. Goodman 《Environmental monitoring and assessment》2000,64(1):197-212
The Little Missouri National Grasslands (LMNG) of western North Dakota support the largest permitted cattle grazing use within all lands administered by the USDA, Forest Service, as well as critical habitat for many wildlife species. This fact, coupled with the need to revise current planning direction for range allotments of the LMNG, necessitated that a broad-level characterization of ecosystem integrity and resource conditions be conducted across all lands within the study area (approximately 800,000 hectares) in a rapid and cost-effective manner. The approach taken in this study was based on ecological classifications, which effectively utilized existing field plot data collected for a variety of previous inventory objectives, and their continuous spatial projection across the LMNG by maps of both existing and potential vegetation. These two map themes represent current and reference conditions (existing vs. potential vegetation); their intersection allowed us to assign various ecological status ratings (i.e., ecosystem integrity and resource condition) based on the degree of departure between current and reference conditions. In this paper, we present a brief review of methodologies used in the development of ecological classifications, and also illustrate their application to assessments of rangeland health through selected maps of ecological status ratings for the LMNG. 相似文献
982.
F. Stagnitti G. Allinson M. Morita M. Nishikawa H. Il T. Hirata 《Environmental Modeling and Assessment》2000,5(4):229-236
Temporal moments analysis of solute breakthrough curves is used to investigate the preferential leaching of chloride, nitrate and phosphate through an Australian soil. Recent studies have shown that current models and methods do not adequately describe the leaching of nutrients through soil, often underestimating the risk of groundwater contamination by surface-applied chemicals, and overestimating the concentration of resident solutes. This inaccuracy results primarily from ignoring soil structure and non-equilibrium between soil constituents, water and solutes. Therefore simple models are required to accurately characterise solute transport in natural and agricultural soils under non-equilibrium conditions. A multiple sample percolation system, consisting of 25 individual collection wells was constructed to study the effects of localised soil heterogeneities on the transport of nutrients (NO3
–, Cl–, PO4
3
–) in the vadose zone of an agricultural soil predominantly dominated by clay. Using data collected from the multiple sample percolation experiments, this paper compares and contrasts the performance of temporal moments analysis with two mathematical models for predicting solute transport, the advective-dispersion model with a reaction term (ADR) and a two-region preferential flow model (TRM) suitable for modelling preferential transport. The values for solute transport parameters predicted by temporal moments analysis were in excellent agreement with experimental data and results from ADR and TRM. It is concluded that temporal moments analysis when applied with other physical models such as the ADR and TRM, provide an excellent means of obtaining values for important solute transport parameters and gaining insight of preferential flow. These results have significant ramifications for modelling solute transport and predicting nutrient loadings. 相似文献
983.
A geographic information system (GIS)-based approach with spatial analysis advantages was developed to optimize the total
emission control scheme on air pollution in Lanzhou, combined with Models-3 modeling system and a linear programming model.
GIS system is mainly used for establishing a multifactor assessment model to quantitatively divide environmental functional
zone, and also used for selecting control sites in linear programming model. The results show that most of the urban area
belongs to the second type of function, which is 122.8 km2 occupying about 76.5% and the third type of about 32.9 km2 occupying 20.5%. To reach the air quality up to the national standard in the entire control area, some large-emission factories
need to cut emissions from 19% to 27%. For small but low-emission height sources, the cut may be as high 40%. The improvement
of the ecological environment is urgently needed for controlling the background particle pollution in Lanzhou city. 相似文献
984.
K. Omasa F. Hosoi T. M. Uenishi Y. Shimizu Y. Akiyama 《Environmental Modeling and Assessment》2008,13(4):473-481
In this study, we confirmed the utility of airborne and portable on-ground scanning light detection and ranging (LIDARs) for
three-dimensional visualization of an urban park and quantification of biophysical variables of trees in the park. The digital
canopy height model (DCHM) and digital terrain model generated from airborne scanning LIDAR data provided precise images of
the ground surface and individual tree canopies. The heights of 166 coniferous and broadleaf trees of 11 species in the park
were estimated from the DCHM images with slight underestimation (mean error = −0.14 m, RMSE = 0.30 m). Portable on-ground
scanning LIDAR provided images of individual trees with detailed features. Tree height and trunk diameter were estimated to
be within 0.31 m and 1 cm, respectively, from the on-ground LIDAR images. We combined airborne and on-ground LIDAR images
to overcome blind regions and created a complete three-dimensional model of three standing trees. The model allowed not only
visual assessment from all viewpoints but also quantitative estimation of canopy volume, trunk volume, and canopy cross-sectional
area. 相似文献
985.
Exposure to perchlorate is widespread in the United States and many studies have attempted to character the perchlorate exposure by estimating the average daily intakes of perchlorate. These approaches provided population-based estimates, but did not provide individual-level exposure estimates. Until recently, exposure activity database such as CSFII, TDS and NHANES become available and provide opportunities to evaluate the individual-level exposure to chemical using exposure surveillance dataset. In this study, we use perchlorate as an example to investigate the usefulness of urinary biomarker data for predicting exposures at the individual level. Specifically, two analyses were conducted: (1) using data from a controlled human study to examine the ability of a physiologically based pharmacokinetic (PBPK) model to predict perchlorate concentrations in single-spot and cumulative urine samples; and (2) using biomarker data from a population-based study and a PBPK model to demonstrate the challenges in linking urinary biomarker concentrations to intake doses for individuals. Results showed that the modeling approach was able to characterize the distribution of biomarker concentrations at the population level, but predicting the exposure-biomarker relationship for individuals was much more difficult. The type of information needed to reduce the uncertainty in estimating intake doses, for individuals, based on biomarker measurements is discussed. 相似文献
986.
Zhenxing Chi Rutao Liu Hong You Donglin Wang 《Journal of environmental science and health. Part. B》2013,48(12):978-984
Tetracycline (TC) is a widely used veterinary drug in animal breeding and fishery. Because of its low bioavailability, the TC residue extensively exists in the environment (e.g. soils, lakes and rivers), which can enter the human body, being potentially harmful. Hemoglobin (Hb) is a protein responsible for oxygen carrying in the vascular system of animals. The aim of this study was to investigate the interaction of bovine hemoglobin (BHb) with TC through spectroscopic and molecular modeling methods. The experimental results revealed that TC can interact with BHb with one binding site to form a TC-BHb complex, mainly through van der Waals interactions and hydrogen bonds. The UV-visible absorption, synchronous fluorescence, and circular dichroism (CD) results revealed that the binding of TC can cause conformational and some microenvironmental changes of BHb, which may affect BHb physiological functions. The synchronous fluorescence experiment disclosed that TC binds into BHb central cavity, which was verified by molecular modeling study. The work contributes to clarify the molecular mechanism of TC toxicity in vivo. 相似文献
987.
以PCF型湿式脱硫除尘器为物理模型,利用Fluent软件包,采用RNGк-ε湍流模型和SIMPLEC算法,对装置内三维流场进行数值模拟.模拟结果发现,原倾斜入口(A)的装置内烟气分布不均匀.提出了水平入口(B)、左入口(C)、右入口(D)3种优化结构,并分别对A、B、C、D入口装置内气流速度、湍流强度与压降进行了模拟分析.结果表明,C、D入口使装置内气流速度分布更加均匀,且增强了装置内湍流强度,但C入口会导致压降增加,因此最佳入口为D.最后,针对入口D装置中的低速区,模拟分析了30°、45°与54°3种不同切入角度,得出45 °效果最佳. 相似文献
988.
Coastal development has severely affected habitats and biodiversity during the last century, but quantitative estimates of the impacts are usually lacking. We utilize predictive habitat modeling and mapping of human pressures to estimate the cumulative long-term effects of coastal development in relation to fish habitats. Based on aerial photographs since the 1960s, shoreline development rates were estimated in the Stockholm archipelago in the Baltic Sea. By combining shoreline development rates with spatial predictions of fish reproduction habitats, we estimated annual habitat degradation rates for three of the most common coastal fish species, northern pike (Esox lucius), Eurasian perch (Perca fluviatilis) and roach (Rutilus rutilus). The results showed that shoreline constructions were concentrated to the reproduction habitats of these species. The estimated degradation rates, where a degraded habitat was defined as having ≥3 constructions per 100 m shoreline, were on average 0.5 % of available habitats per year and about 1 % in areas close to larger population centers. Approximately 40 % of available habitats were already degraded in 2005. These results provide an example of how many small construction projects over time may have a vast impact on coastal fish populations.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-014-0522-y) contains supplementary material, which is available to authorized users. 相似文献989.
通过对机械絮凝池内不同进水流量和不同桨板转速的流场分别进行数值模拟,计算得到湍动能k和湍动耗散率ε等水力参数,并结合混凝实验分析水流对絮凝效果的影响。结果表明:湍动能k和湍动耗散率ε可以作为评价絮凝是否充分的标准;机械絮凝池最佳水力停留时间为18 min;平均k值为0.00613~0.00212 m2/s2,平均ε值为0.00869~0.00199 m2/s3时,机械絮凝池装置的絮凝效果比较理想。 相似文献
990.