全文获取类型
收费全文 | 4797篇 |
免费 | 436篇 |
国内免费 | 1402篇 |
专业分类
安全科学 | 833篇 |
废物处理 | 219篇 |
环保管理 | 633篇 |
综合类 | 3201篇 |
基础理论 | 665篇 |
环境理论 | 2篇 |
污染及防治 | 635篇 |
评价与监测 | 141篇 |
社会与环境 | 215篇 |
灾害及防治 | 91篇 |
出版年
2024年 | 8篇 |
2023年 | 47篇 |
2022年 | 109篇 |
2021年 | 178篇 |
2020年 | 160篇 |
2019年 | 157篇 |
2018年 | 178篇 |
2017年 | 209篇 |
2016年 | 217篇 |
2015年 | 240篇 |
2014年 | 296篇 |
2013年 | 406篇 |
2012年 | 409篇 |
2011年 | 466篇 |
2010年 | 319篇 |
2009年 | 347篇 |
2008年 | 240篇 |
2007年 | 412篇 |
2006年 | 354篇 |
2005年 | 252篇 |
2004年 | 237篇 |
2003年 | 224篇 |
2002年 | 188篇 |
2001年 | 159篇 |
2000年 | 151篇 |
1999年 | 119篇 |
1998年 | 90篇 |
1997年 | 80篇 |
1996年 | 65篇 |
1995年 | 73篇 |
1994年 | 61篇 |
1993年 | 42篇 |
1992年 | 23篇 |
1991年 | 28篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有6635条查询结果,搜索用时 171 毫秒
291.
Evaluating potential hazards caused by accidental LNG release from underwater pipelines or vessels is a significant consideration in marine transportation safety. The aim of this study was to capture the dynamic behavior of LNG jet released under water and to analyze its vapor dispersion characteristics and combustion characteristics on the water surface during different release scenarios. Controlled experiments were conducted where LNG was jet released from a cryogenic storage tank. The dynamic process of LNG being jet released from orifices of different sizes and shapes, as well as the rising plume structure, were captured by a high-speed camera. The leakage flow rate and pipeline pressure were recorded by a flow meter and pressure gauge, respectively. The concentration distribution that emanated from the water surface was measured utilizing methane sensors in different positions with various wind speeds. The flame combustion characteristics of LNG vapor clouds, which immediately ignited upon the enclosed water tank, were also recorded. Additionally, the mass burning rate of the flame on the water surface was evaluated, and a new correlation between the ratio of flame length and width was established. The results indicated a large dimensionless heat release rate (Q*) and a continuous release flow rate in a limited burning area. This study could provide greater understanding of the mechanisms of LNG release and combustion behavior under water. 相似文献
292.
Pool evaporation is a major source of flammable vapour clouds. Predicting the evaporation rate of a liquid hydrocarbon pool is therefore a key issue of dispersion modelling for safety concerns. This paper presents small- and medium-scale experiments of pool evaporation carried out with liquid hydrocarbons (pentane, heptane), hydrocarbon “gasoline-like” mixtures and gasoline. Liquid mass loss was measured and the evaporation rate deduced with its evolution in time. Other observations are highlighted, regarding the evolution of liquid temperatures, mixture compositions, and scale effects like the influence of pool length on surface evaporation rate. Comparisons with well-known correlations are then shown. The authors finally suggest a new semi-empirical correlation with a set of parameters fitted on the performed experiments. 相似文献
293.
Melike E. Bildirici 《Natural resources forum》2020,44(4):289-310
In this paper, the life span of hydro and nuclear energy generations and the relationship between hydro and nuclear energy generations, environmental pollution, and economic growth were investigated for Japan covering the period of 1960–2018 by employing the Bathtub-Weibull curve and Markov switching-vector error correcting (MSVEC) method, respectively. According to the Bathtub-Weibull curve analysis, a rising failure rate for nuclear energy was found, indicating that the life of nuclear energy has expired, but a decreasing failure rate for hydroelectric energy has been detected. Then two different MSVEC models were used. The MSVEC method, unlike traditional approaches, determines the relationship between variables under different regimes. The results of MSVEC methods indicate three important points. First, regime-dependent asymmetry and regime changes are crucial for policy recommendations. Second, the shocks to hydropower and nuclear energy generations cause temporary deviations from the long-run growth path in both regimes. Lastly, the increase in hydropower generation leads to a decrease in environmental pollution and an increase in GDP, and an increase in nuclear power generation increases pollution and growth in both regimes. 相似文献
294.
Mona Akbar Muhammad Farooq Saleem Khan Ling Qian Hui Wang 《Frontiers of Environmental Science & Engineering》2020,14(6):98
295.
A submersible sonde equipped with a specific conductivity probe, linked with a global positioning satellite receiver was developed, deployed on a small boat, and used to map spatial and temporal variations in specific conductivity in a large reservoir. 7,695 sample points were recorded during 8 sampling trips. Specific conductivity ranged from 442,uS/cm to 3,378,uS/cm over the nine-month study. The data showed five statistically different zones in the reservoir: 2 different riverine zones, 2 different riverine transition zones, and a lacustrine zone (the main lake zone). These data were imported to a geographic information system where they were spatially interpolated to generate 8 maps showing specific conductivity levels across the entire surface of the lake. The highly dynamic nature of water quality, due to the widely differing nature of the rivers that flow into the reservoir and the effect of large inflows of fresh water during winter storms is easily captured and visualized using this approach. 相似文献
296.
297.
298.
299.
Dimitrakopoulos PG Siamantziouras AS Galanidis A Mprezetou I Troumbis AY 《Environmental management》2006,37(6):826-839
We conducted a field experiment using constructed communities to test whether species richness contributed to the maintenance
of ecosystem processes under fire disturbance. We studied the effects of diversity components (i.e., species richness and
species composition) upon productivity, structural traits of vegetation, decomposition rates, and soil nutrients between burnt
and unburnt experimental Mediterranean grassland communities. Our results demonstrated that fire and species richness had
interactive effects on aboveground biomass production and canopy structure components. Fire increased biomass production of
the highest-richness communities. The effects of fire on aboveground biomass production at different levels of species richness
were derived from changes in both vertical and horizontal canopy structure of the communities. The most species-rich communities
appeared to be more resistant to fire in relation to species-poor ones, due to both compositional and richness effects. Interactive
effects of fire and species richness were not important for belowground processes. Decomposition rates increased with species
richness, related in part to increased levels of canopy structure traits. Fire increased soil nutrients and long-term decomposition
rate. Our results provide evidence that composition within richness levels had often larger effects on the stability of aboveground
ecosystem processes in the face of fire disturbance than species richness per se. 相似文献
300.