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排序方式: 共有671条查询结果,搜索用时 15 毫秒
51.
高压旋喷灌浆法是本世纪70 年代发展起来的地基处理新技术,在砂性土和粘性土等软弱地层加固工程中已得到广泛应用,但在含有碎石的淤泥质土及穿过它对其下淤泥的加固尚少见,笔者简要介绍了采用钻灌分开两大工序的新双管法及其成功完成加固任务的事例。 相似文献
52.
新亚欧大陆桥新疆段易损性分析 总被引:4,自引:2,他引:2
从灾害频数、断道密度分析着手,选取与易损性评价指标;根据新亚欧大陆桥新疆段近40年的灾害资料,在详尽分析各不同区段灾害密度,断道时间和断道次数密度的基础上,对各区一路的脆弱性和易损性强度进行评价,提出了新亚欧大陆桥新疆段的最易受损区段,并与全国平均水平进行了对比。 相似文献
53.
Chang WR 《Journal of Safety Research》2004,35(1):71-79
PROBLEM: Surface roughness affects friction, so selection of floor surfaces with certain roughness characteristics could potentially reduce slip and fall accidents. This article summarizes the preferred surface microscopic geometric features that could increase friction on surfaces covered with liquid contaminants. METHOD: Three types of surface features, represented by the average of the maximum height above the mean line in each cut-off length (R(pm)), the arithmetical average of surface slope (Delta(a)), and the kernel roughness depth (R(k)), are identified as preferred surface microscopic geometric features for a higher friction. The proper settings on the profilometers (instruments used to measure surface roughness) for optimizing these surface parameters are specified. The friction mechanisms involved reveal why these features are more desirable. RESULTS: Although surface roughness is important in determining slipperiness, there is still insufficient information to establish a safety criterion based on roughness; however, the method presented in this paper can readily provide a relative comparison. IMPACT ON INDUSTRY: The summary presented will help safety professionals properly select new floor surfaces or assess existing floors to reduce slip and fall accidents. 相似文献
54.
PROBLEM: In recent years, there has been a significant reduction in traffic crash injury among young people, but they continue to be overrepresented in the traffic crash statistics. To improve this situation, sound scientific evidence is needed to develop effective policies and programs. METHOD: The aim of the proposed study is to provide this evidence by examining early driving and driving-related experiences of newly licensed drivers as they progress through the learner-, restricted-, and full-license stages of the graduated licensing system and to determine the impact of these experiences on subsequent negative traffic-related outcomes (risky driving behavior, injury traffic crashes, noninjury traffic crashes, infringements, convictions). Given the size and complexity of the proposed study, a comprehensive pilot study was undertaken to determine the feasibility of conducting a New Zealand-wide cohort study of newly licensed drivers. RESULTS: This article describes the pilot study process and the methodology that has been developed for the New Zealand-wide study. 相似文献
55.
Vernal pools are vulnerable to loss through development and agricultural and forestry practices owing to their isolation from open water bodies and their small size. Some vernal pool-dependent species are already listed in New England as Endangered, Threatened, or Species of Special Concern. Vernal pool creation is becoming more common in compensatory mitigation as open water ponds, in general, may be easier to create than wooded wetlands. However, research on vernal pool creation is limited. A recent National Research Council study (2001) cites vernal pools as challenging to recreate. We reviewed documentation on 15 vernal pool creation projects in New England that were required by federal regulatory action. Our purpose was to determine whether vernal pool creation for compensatory mitigation in New England replaced key vernal pool functions by assessing project goals and documentation (including mitigation plans, pool design criteria, monitoring protocols, and performance standards). Our results indicate that creation attempts often fail to replicate lost pool functions. Pool design specifications are often based on conjecture rather than on reference wetlands or created pools that function successfully. Project monitoring lacks consistency and reliability, and record keeping by regulatory agencies is inadequate. Strengthening of protection of isolated wetlands in general, and standardization across all aspects of vernal pool creation, is needed to ensure success and to promote conservation of the long-term landscape functions of vernal pools. 相似文献
56.
Differences between scientist and policy-maker response types and times, or the “how” and “when” of action, constrain effective
water resource management in suburbanizing watersheds. Policy-makers are often rushed to find a single policy that can be
applied across an entire, homogeneous, geopolitical region, whereas scientists undertake multiyear research projects to appreciate
the complex interactions occurring within heterogeneous catchments. As a result, watershed management is often practiced with
science and policy out of synch. Meanwhile, development pressures in suburban watersheds create changes in the social and
physical fabric and pose a moving target for science and policy. Recent and anticipated advances in the scientific understanding
of urbanized catchment hydrology and pollutant transport suggest that management should become increasingly sensitive to spatial
heterogeneities in watershed features, such as soil types, terrain slopes, and seasonal watertable profiles. Toward this end,
policy-makers should encourage funding scientific research that characterizes the impacts of these watershed heterogeneities
within a geopolitical zoning and development framework. 相似文献
57.
Specific Conductance and pH as Indicators of Watershed Disturbance in Streams of the New Jersey Pinelands, USA 总被引:2,自引:0,他引:2
/ We used linear regression to independently and jointly relate specific conductance and pH measured at New Jersey Pinelands stream sites to the percentage of altered land in a watershed. Percentage altered land included developed and agricultural land uses and represented watershed disturbance for a given site. Median values calculated for a 2-year period (September 1992 through August 1994) characterized pH and specific conductance at the study sites. We found the relationships between the median values for both water-quality measures and percentage altered land for a site to be consistent across subregion and dominant altered-land use. Our results also demonstrated that the water-quality/altered-land relationships developed using median values were similar to relationships developed using data from any single-sample period within the entire study period. Individually, pH and specific conductance explained 48% and 56%, respectively, of the variability in watershed disturbance among study sites. The joint use of pH and specific conductance explained 79% of the watershed disturbance variability among sites. The joint use of these easily obtained water-quality measures can provide a quick assessment of instream water-quality impacts from upstream watershed disturbance at any Pinelands stream site. Additionally, a range in pH and specific conductance, and hence a range in ambient water quality, can be predicted for a given altered-land percentage or a change in existing altered-land conditions. 相似文献
58.
巢湖作为安徽省境内的一个重要湖泊,对安徽省生态环境起到一定的影响作用。蒸发量是影响生态环境的重要因子,在很多方面是该区生态环境的一个反映。采用了统计学方法,对巢湖流域15个蒸发点20年(1981-2000年)的资料进行了分析,初步探讨了巢湖流域的蒸发量空间分布特征与地势、气温、风速、降水量等因子的关系,以及蒸发量在1年内的变化特征和年际变化趋势,试图说明研究时段内人类活动对区域蒸发量的影响。研究表明,由于地形等因素的影响,巢湖流域的蒸发量空间分布不均衡,在研究时段内蒸发量大体呈上升趋势。 相似文献
59.
Judith A. Pickering Richard A. Andrews 《Journal of the American Water Resources Association》1979,15(4):1039-1049
ABSTRACT: The objective of the study was to evaluate alternative land developments around New Hampshire lakes. Alternative development patterns, evaluated by their impacts on the lake area environment and area economy, included residential patterns, commercial patterns, and combinations of these two types. Phosphorus loading of the lake water was used as a proxy variable for changes in the lake water quality. Commercial developments yielded the highest revenues to the town and the local area. It also attracted the most lake users to the area as well as contributing the largest phosphorus loading in the lake waters. Residential developments, although contributing high revenues to the businessmen in the area, yielded less net income to the town. Phosphorus loading levels from residential developments were much lower than lake phosphorus loading by commercial developments. 相似文献
60.
S. Lawrence Dingman 《Journal of the American Water Resources Association》1981,17(4):684-690
: In general, the choice among reservoirs for water supply or flow augmentation is a multiobjective problem. Choices are based in part on the yield available from water supply reservoirs or, in the case of flow augmentation reservoirs, on the increase in low flows at downstream locations. Detailed estimates of these effects may be too costly for basin planning purposes. Thus this paper presents methods for rapid estimation of those quantities for New Hampshire. For water supply reservoirs, a composite empirical relation between Y95 (the draft available 95 percent of the time) and storage ratio, S*, is developed from previous studies in the region. For flow augmentation reservoirs, empirical relations between S* and degree of regulation, R*, are applied to each upstream regulating reservoir. Values of regulation arc then summed and divided by the mean flow at the downstream reach of interest. This parameter, (ΓR)*, is then related to increase in flow available 95 percent of the time by an empirical relation. 相似文献