全文获取类型
收费全文 | 86篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
化学 | 14篇 |
力学 | 55篇 |
综合类 | 1篇 |
数学 | 3篇 |
物理学 | 21篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 8篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 2篇 |
2010年 | 9篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有94条查询结果,搜索用时 31 毫秒
41.
Particulate matter(PM) pollution in an underground car park in Wuhan was investigated.Mass concentrations of PM10 and PM2.5 were obtained using gravimetric method.Selected metal elements,such as Fe,Mn,Zn,Pb,and Cu in PM10 samples,were determined using atomic absorption spectrometer(AAS). Beta attenuation method was applied to observe the hourly variation of PM10 levels.Results show that average PM10 concentrations at the entrance and at the exit were 101.3μg/m3 and 234.4μg/m3,respectively, and average PM2.5 concentrations at the entrance and at the exit were 47.7μg/m3 and 62.7μg/m3, respectively.PM pollution was worse at the exit than at the entrance.Hourly PM10 concentration was weakly correlated with traffic flow.Regarding element concentrations,the most enriched element in PM10 samples was Fe.Re-suspension of soil dust at the exit is an important source of PM10. 相似文献
42.
Underground coal fires (UCFs) exist in almost all coal mining countries. In this paper, an optimised Thermal–Hydraulic–Chemical model, which includes variable reaction kinetics of coal and permeability variation in UCF zones, was developed for the simulation of dynamic temperature evolution of an actual UCF in Xinjiang, China. The model was also adopted in the analysis of the effect of surface coverage permeability on the temperature field, providing a theoretical reference for UCFs control. The results demonstrate that the temperature evolution included three distinct stages which were slow-heating stage, rapid-heating stage and stable-development stage. The slow-heating stage was occupied by the low-temperature oxidation of residual coal. During the rapid-heating stage, a hotspot (combustion centre) formed in residual coal zone and moved toward the air inlet side when the temperature reached a certain threshold. And before moving back into the deeper coal seam, the hotspot developed the temperature to the maximum when it got to the air inlet side. In the stable-development stage, the hotspot spread along the coal seam with the maximum temperature staying between about 800°C and 1000°C, creating elliptical temperature anomalies around the combustion centre. The simulation proved to be in good agreement with the in situ measurements. Surface covering will extinguish the UCF when the permeability of the coverage layer is lower than 10–10?m2, otherwise the fire will persist and continue to spread. 相似文献
43.
44.
Solvents used in microextraction require high solubilising capability to efficiently extract the target compounds. In this article, nanostructured solvents made up of alkyl carboxylic acids (ACAs) aggregate are proposed for the efficient microextraction of acidic pesticides from natural waters. The target compounds were chlorophenoxy acid herbicides (CPAHs) widely used in agriculture, forestry and gardening (viz. 2,4-D, MCPA, MCPP, 2,4,5-T and MCPB). The supramolecular solvents (SUPRASs) tested were generated from solutions of reverse micelles of octanoic (OcA), decanoic (DeA) and dodecanoic (DoA) acid in THF by the addition of water, which acted as the coacervating agent. The DeA-based SUPRAS was the most efficient extractant for CPAHs; actual concentration factors (ACFs) of 260 for 2,4-D, 290 for MCPA, and 400 for MCPP, 2,4,5-T and MCPB were obtained. The explanation for so high ACFs can be found in the extremely efficient retention mechanisms that the DeA-based SUPRAS provides for CPAHs (i.e. formation of hydrogen bonds and hydrophobic interactions), and the high number of binding sites that it contains (i.e. the concentration of biosurfactant in the SUPRAS was 0.56 mg μL−1). Both characteristics permitted to effectively extract the target analytes in a low volume of solvent (about 2 μL of solvent per mL of sample). Others assets of the proposed supramolecular solvent-based microextraction (SUSME) approach included recoveries no dependent on matrix composition, rapidity (sample treatment spent about 15 min), use of low volume of sample (63 mL per analysis) and simplicity (no special lab equipments was needed). Combination with liquid chromatography/ion–trap mass spectrometry [LC–(IT)MS] afforded method quantitation limits for CPAHs within the interval 22–30 ng L−1. The precision of the method, expressed as relative standard deviation (n = 11, [CPAH] = 200 ng L−1), was in the range 2.9–5.8%. The applicability of the method to the analysis of natural waters was assessed by determining the target analytes in fortified river and underground water samples. 相似文献
45.
This paper focuses on effects of protection with a silicone resin to develop a fiber-optic oxygen sensor with long-term stability and durability in harsh underground environments. Ruthenium (II) complexes were used as oxygen-sensing compounds. A uniform composite film composed of silicone resin and the Ru complex was prepared with spin coating technique. A comparison of dissolved-oxygen (DO) sensitivity between the composite film and a Ru complex film was made by exposing to hot water (80 °C). The result of the accelerated degradation test showed that sensitivity of the Ru complex film was stable; meanwhile that of the composite film increased with exposure time in a short period. In order to improve stability, the Ru complex film overcoated with silicone resin was prepared. Differences in sensitivity for saturated DO (8.5 ppm) between with and without the silicone resin overcoating on the Ru complex film were investigated by exposing to the hot water and simulated underground water. These results revealed that the sensitivities and response times of the overcoated films were stable and slow, respectively, compared to those of non-overcoated films. Then, optodes were evaluated for effects of the overcoating on sensing properties by exposing to 100 vol.% oxygen gas. The experiment showed that: (1) the response time was significantly influenced by the thickness of the overcoating; and (2) response speed of the overcoated optode was slow by a factor of about 35 compared to that of the non-overcoated. We concluded that the overcoating was effective in the application to mid- and long-term oxygen monitoring in the harsh environments. 相似文献
46.
采用电感耦合等离子体发射光谱法(ICP-AES)测定地表水和地下水中的全S、P、B来近似代替水中的SO42-、PO43-、H3BO3。结果表明,ICP-AES可同时测定地表水和地下水的SO42-、PO43-、H3BO3,方法检出限分别为0.0265mg/L、0.0320mg/L、0.0192mg/L。方法的精密度(RSD,n=6)为0.53﹪~6.09﹪,加标回收率为91.9﹪~102.2﹪,经与单个项目分别测定的方法比对实验,测定值无明显系统偏差。方法快速、准确,经国家标准物质验证,结果与标准值相符。 相似文献
47.
条形装药硐室爆破研究 总被引:10,自引:0,他引:10
从理论上分析计算了条形装药硐室爆破急待解决的最佳空腔比、装药端部效应,给出了条形装药爆破设计的有关参数,并通过具体实例验证了理论结果的准确住,同时通过地震测量,讨论了条形装药爆破的地震效应。 相似文献
48.
库水位上升条件下边坡渗流场模拟 总被引:2,自引:0,他引:2
库水位的上升将导致边坡体内渗流场的变化,进而引起边坡的失稳破坏。边坡体内的渗流场是饱和渗流与非饱和渗流共同作用的结果,通过对库水位上升过程中坡体内地下水位线的位置变化及相应的渗流场参数的计算表明:由于上部松散堆积体与基岩渗透系数的差异,基岩内地下水位线的抬升速度明显滞后于上部松散堆积体;体积含水量、压力水头、流速和水力梯度等渗流参量在基岩中的变化幅度较小,而在上部松散堆积体中的变化幅度则相对较大。这说明库水位上升对上部松散堆积体的影响相对来说还是比较明显的。 相似文献
49.
50.