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1.
此文介绍尺寸为φ1547×L900×δ30的大直径TA2卷焊坯的制备工艺。主要包括卷焊坯设计、展开下料的计算、卷圆工艺、焊接工艺等,可供同类材质圆筒件卷圆时参考。 相似文献
2.
环境影响综合评价灰色层次模型研究 总被引:8,自引:1,他引:8
针对水电工程环境影响综合评价问题,应用拓展的灰关联理论和最小二乘准则,建立了环境影响综合评价的灰色层次模型。以东江水电工程环境影响综合评价为实例说明了该模型的合理性、可信性。结果表明:此基工程使环境总体向理想的18.1% 相似文献
3.
青藏高原多年冻土区铁路路堤变形特征研究 总被引:6,自引:1,他引:6
路堤的稳定是公路、铁路等行车安全的保证。路堤变形通过路基—轨道—车辆大系统的相互作用而影响行车安全。冻胀、融沉是多年冻土地区路堤变形的重要形式。多年冻土区的路基变形问题是至今仍未彻底解决的一大难题。青藏铁路穿越 5 5 0km多年冻土区 ,为研究多年冻土区路堤变形特征 ,笔者对青藏铁路某试验段进行变形监测并对监测数据进行分析。结果表明铁路路堤的修建改变了多年冻土原来的水热平衡 ,天然冻土上限的变化导致路堤产生变形。同时 ,变形特征还受路堤边坡的坡向、降水量和地基土类型等因素的制约。在此基础上 ,提出几点减少多年冻土区铁路路堤变形的一些看法和建议。 相似文献
4.
爆炸冲击波作用下靶板的塑性大变形响应研究 总被引:13,自引:0,他引:13
对四边约束方形靶板 ,在爆炸冲击波作用下的塑性大变形响应情况 ,进行了理论分析与试验研究。运用能量守恒的方法 ,同时考虑试验过程中靶板的边界约束条件 ,得到了四边约束方形靶板在爆炸冲击波作用下发生塑性大变形时挠度的半经验公式。理论计算与试验结果吻合性较好 ,这种方法可应用于板结构在爆炸冲击波作用下的毁伤或防护方面的工程预测 相似文献
5.
6.
The need for accurate carbon budgeting, climate change modelling, and sustainable resource management has lead to an increase
in the number of large area forest monitoring programs. Large area forest monitoring programs often utilize field and remotely
sensed data sources. Sampling, via field or photo plots, enables the collection of data with the desired level of categorical
detail in a timely and efficient manner. When sampling, the aim is to collect representative detailed data enabling the statistical
reporting upon the characteristics of larger areas. As a consequence, approaches for investigating how well sample data represent
larger areas (i.e., the sample neighbourhood and the population) are desired. Presented in this communication is a quantitative
approach for assessing the nature of sampled areas in relation to surrounding areas and the overall population of interest.
Classified Landsat data is converted to forest/non-forest categories to provide a consistent and uniform data set over a 130,000 km2 study region in central British Columbia, Canada. From this larger study area 322 2 × 2 km photo plots on a 20 × 20 km systematic
grid are populated with composition and configuration information for comparison to non-sampled areas. Results indicate that
typically, within the study area, the spatial pattern of forest within a photo plot is representative of the forest patterns
found within primary and secondary neighbourhoods and over the entire population of the study. These methods have implications
for understanding the nature of data used in monitoring programs worldwide. The ability to audit photo and field plot information
promotes an increased understanding of the results developed from sampling and provides tools identifying locations of possible
bias. 相似文献
7.
Preventing the propagation of flames in a pipeline is an effective measure for avoiding gas explosion accidents and reducing losses. To evaluate the effect of wire mesh, acting as a porous media, experimental and simulation studies are conducted to determine the influence of the wire mesh on the dynamics of premixed methane/air flame propagation in a semi-closed pipe. Four different kinds of wire mesh with different numbers of layers are chosen in the experiments and simulation, and the mechanism of wire mesh quenching of the flame is investigated. The experimental and simulation results are consistent. Flames are quenched when 4 layers of 40-mesh or 3 layers of 60-mesh wire mesh are used; however, once the flame propagates through the wire mesh, the risk of methane combustion may increase. The wire mesh becomes the key factor causing flame folds and acceleration, and the greater the number of layers or the larger the mesh size is, the more obvious the folds after the flame passes through the wire mesh. Moreover, the combination of heat absorption and disruption of the continuous flame surface by the mesh causes flame quenching. Wire mesh can effectively attenuate the flame temperature during premixed flame propagation in a pipe, and the attenuated maximum rate reaches approximately 79% in the case of adding 3 layers of 60-mesh wire mesh. 相似文献
8.
We documented valley and channel characteristics and wood loads in 19 reaches of forested headwater mountain streams in the
Bighorn National Forest of northern Wyoming. Ten of these reaches were in the Upper Tongue River watershed, which has a history
of management including timber harvest, tie floating, and road construction. Nine reaches were in the North Rock Creek watershed,
which has little history of management activities. We used these data to test hypotheses that (i) valley geometry correlates
with wood load, (ii) stream gradient correlates with wood load, and (iii) wood loads are significantly lower in managed watersheds
than in otherwise similar unmanaged watersheds. Statistical analyses of the data support the first and third hypotheses. Stream
reaches with steeper valley side slopes tend to have higher wood loads, and reaches in managed watersheds tend to have lower
wood loads than reaches in unmanaged watersheds. Results do not support the second hypothesis. Shear stress correlated more
strongly with wood load than did stream gradient, but statistical models with valley-scale variables had greater explanatory
power than statistical models with channel-scale variables. Wood loads in stream reaches within managed watersheds in the
Bighorn National Forest tend to be two to three times lower than wood loads in unmanaged watersheds. 相似文献
9.
关于现代中国安全生产管理体系研究:管理、法规、文化 总被引:1,自引:0,他引:1
金磊 《中国安全科学学报》1994,4(2):7-12
对我国安全生产管理的宏观及微观形势分析,论证了安全生产与国民经济的关系。特别指出从根本上遏制新的事故高峰,关键应强化“大安全观”的安全生产管理体系建设与实践。研究向市场经济转换过程中的中国安全减灾业的发展及管理思路,重点探索了体系化管理、安全文化及安全生产法的主题。 相似文献
10.
River systems as providers of goods and services: a basis for comparing desired and undesired effects of large dam projects 总被引:3,自引:0,他引:3
Brismar A 《Environmental management》2002,29(5):598-609
In developing countries, large dam projects continue to be launched, primarily to secure a time-stable freshwater supply and
to generate hydropower. Meanwhile, calls for environmentally sustainable development put pressure on the dam-building industry
to integrate ecological concerns in project planning and decision-making. Such integration requires environmental impact statements
(EISs) that can communicate the societal implications of the ecological effects in terms that are understandable and useful
to planners and decision-makers.
The purpose of this study is to develop a basic framework for assessing the societal implications of the river ecological
effects expected of a proposed large dam project. The aim is to facilitate a comparison of desired and potential undesired
effects on-site and downstream. The study involves two main tasks: to identify key river goods and services that a river system
may provide, and to analyze how the implementation of a large dam project may alter the on-site capacity and downstream potentials
to derive river goods and services from the river system.
Three river goods and six river services are identified. River goods are defined as extractable partly man-made products and
river services as naturally sustained processes. By four main types of flow manipulations, a large dam project improves the
on-site capacity to derive desired river goods, but simultaneously threatens the provision of desirable river goods and services
downstream. However, by adjusting the site, design, and operational schedule of the proposed dam project, undesirable effects
on river goods and services can be minimized. 相似文献