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41.
The possibility of ignition and flame propagation in accumulated difluoromethane (CH2F2, R32) was examined experimentally, simulating a situation in which a service operative uses a kerosene lighter for smoking. To simulate the situation where a kerosene cigarette lighter is used in accumulated R32, electrodes fixed in the windbreak of the lighter were remotely supplied with electricity to generate sparks of various durations but of similar energies to those of actual sparks generated by rubbing a flint to ignite the fuel in the lighter. We identified several cases of ignition and formation of an open flame in the windbreak of the lighter, and the flame propagated to the accumulated R32 when it was supplied with sufficient energy from the spark. Gas chromatographic analyses confirmed that the mixture in the windbreak of the kerosene lighter consisted mainly of vaporized fuel and air, with no R32. Therefore, even if the lighter is located in accumulated R32, an open flame can be generated in the windbreak of the kerosene cigarette lighter through ignition by the spark energy generated by friction between the flint and the flint wheel. Our results confirmed that there is a real possibility of ignition and flame propagation when a kerosene cigarette lighter is used in accumulated R32 under the leak rate conditions of the present experiment. 相似文献
42.
用萃取火焰AAS法测定汽车道旁树叶中的铅含量 总被引:4,自引:0,他引:4
主要介绍了用碘化钾-甲基异丁基甲酮(KI-MIBK)萃取汽车道旁植物叶片中的微量铅,然后用原子吸收分光光度法(AAS)测定,该方法的精密度和准确度均有较满意的结果 相似文献
43.
44.
火焰振荡频率是火灾科学研究领域的一个重要基本参数,对横向风下火焰振荡频率的研究可以为火灾图像探测的参数设置提供理论依据。针对浮力扩散火焰(0.6×10~(-5)弗洛德数Fr2×10~(-2),10~2理查德森数Ri10~5),本研究将横向风条件下火焰结构假设为倾斜的柱状,通过对燃烧产生的浮力和横向风产生的拖曳力进行动力学分析,得出横向风条件下火焰振荡频率表达公式。结合实验结果得出,火焰振荡频率的理论值和实验值均随拖曳系数的增大(即外界风速的增加)而增大,但实验值的上升趋势较理论值平缓.这是因为公式忽略了风速对火焰温度和系数K的影响。 相似文献
45.
Emiel A. Den Hartog George Havenith 《International journal of occupational safety and ergonomics》2013,19(2):245-261
For wearers of protective clothing in radiation environments there are no quantitative guidelines available for the effect of a radiative heat load on heat exchange. Under the European Union funded project ThermProtect an analytical effort was defined to address the issue of radiative heat load while wearing protective clothing. As within the ThermProtect project much information has become available from thermal manikin experiments in thermal radiation environments, these sets of experimental data are used to verify the analytical approach. The analytical approach provided a good prediction of the heat loss in the manikin experiments, 95% of the variance was explained by the model. The model has not yet been validated at high radiative heat loads and neglects some physical properties of the radiation emissivity. Still, the analytical approach provides a pragmatic approach and may be useful for practical implementation in protective clothing standards for moderate thermal radiation environments. 相似文献
46.
Kalev Kuklane Valter Dejke 《International journal of occupational safety and ergonomics》2013,19(2):199-216
The European Standard on sleeping bag requirements (EN 13537:2002) describes a procedure to determine environmental temperature limits for safe usage of sleeping bags regarding their thermal insulation. However, there are several possible sources of error related to this procedure. The main aim of this work was to determine the influence of the various measuring parameters on the acuity of the respective parameters in order to judge the requirements. The results indicated that air velocity, mattress insulation and time between unpacking the bag and measurement had a significant impact on the result, with a difference of up to 5–15% in thermal insulation between minimum and maximum allowable parameter levels. On the other hand, manikin weight, thickness of the artificial ground and presence of a face mask were found to have a negligible influence. The article also discusses more general aspects of the standard including the calculation methods used. 相似文献
47.
A. Grov H.E.Z. OpsvikR.K. Eckhoff 《Journal of Loss Prevention in the Process Industries》2011,24(5):552-557
Electrical apparatus for use in the presence of explosive gas atmospheres has to be specially designed to prevent the apparatus from igniting the gas. Flameproof design is one of several options, and one requirement is then that any holes and slits in the enclosure wall be designed to prevent a possible gas explosion inside the enclosure from being transmitted to an explosive gas cloud outside it. Current standards (IEC) require that joint surfaces have a surface roughness of <6.3 μm. Any damaged joint surface has be restored to this quality. The present investigation has demonstrated that flame gap surfaces in flameproof electrical apparatuses can suffer considerable mechanical and corrosive damage before the flame gaps no longer function satisfactorily. In some cases very significant mechanical surface damage in fact improves the gap performance. This indicates that current high costs of repairing and replacing flameproof electrical apparatus in process plants offshore and onshore can be reduced considerably without any increase of the explosion risk. 相似文献
48.
S. B. Dorofeev M. S. Kuznetsov V. I. Alekseev A. A. Efimenko W. Breitung 《Journal of Loss Prevention in the Process Industries》2001,14(6):583-589
Results of experiments and data analysis on turbulent flame propagation in obstructed channels are presented. The data cover a wide range of mixtures: H2/air, H2/air/steam (from lean to rich) at normal and elevated initial temperatures (from 298 to 650 K) and pressures (from 1 to 3 bar); and stoichiometric H2/O2 mixtures diluted with N2, Ar, He and CO2 at normal initial conditions. The dataset chosen also covers a wide range of scales exceeding two orders of magnitude. It is shown that basic flame parameters, such as mixture expansion ratio σ, Zeldovich number β and Lewis number Le, can be used to estimate a priori a potential for effective flame acceleration for a given mixture. Critical conditions for effective flame acceleration are suggested in the form of correlations of critical expansion ratio σ* versus dimensionless effective activation energy. On this basis, limits for effective flame acceleration for hydrogen combustibles can be estimated. Uncertainties in determination of critical σ* values are discussed. 相似文献
49.
K. -H. Oh H. Kim J. -B. Kim S. -E. Lee 《Journal of Loss Prevention in the Process Industries》2001,14(6):597-602
A study on the variation of the gas explosion characteristics caused by the built-in obstacles was conducted in enclosed/vented gas explosion vessels. It has been well known that the obstacles in pipes and long ducts would accelerate the flame propagation, and cause the transition from deflagration to detonation. In this study, the explosion characteristics and the flame behavior of vented explosions and constant-volume explosions were investigated. Experiments were carried out in a 270-liter and 36-liter hexahedron vessels filled with LPG–air mixture. The explosion characteristics of the gas mixture were determined by using a strain-responding pressure transducer. The flame behavior was recorded by using a high-speed video camera. The shape and the size of the obstacle, and the gas concentration, were adjusted in the experiments.
It can be seen from the experimental results that, instead of being accelerated, the flame propagation inside the explosion vessel is decelerated by the plate obstacles fixed at the bottom of the vessel. Also, the characteristics of the enclosed explosion are not so affected by the built-in obstacles as those of the vented explosion are. It is believed that the eddy-induced turbulence behind the obstacle decelerates the flame propagation. 相似文献
50.