首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   721篇
  免费   16篇
  国内免费   5篇
电工技术   16篇
综合类   37篇
化学工业   129篇
金属工艺   16篇
机械仪表   35篇
建筑科学   93篇
矿业工程   108篇
能源动力   32篇
轻工业   30篇
水利工程   1篇
石油天然气   15篇
武器工业   5篇
无线电   30篇
一般工业技术   69篇
冶金工业   81篇
原子能技术   11篇
自动化技术   34篇
  2023年   3篇
  2022年   18篇
  2021年   14篇
  2020年   18篇
  2019年   20篇
  2018年   13篇
  2017年   17篇
  2016年   23篇
  2015年   17篇
  2014年   37篇
  2013年   43篇
  2012年   29篇
  2011年   58篇
  2010年   40篇
  2009年   37篇
  2008年   24篇
  2007年   36篇
  2006年   45篇
  2005年   29篇
  2004年   33篇
  2003年   24篇
  2002年   23篇
  2001年   27篇
  2000年   16篇
  1999年   16篇
  1998年   22篇
  1997年   18篇
  1996年   6篇
  1995年   15篇
  1994年   6篇
  1993年   5篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
排序方式: 共有742条查询结果,搜索用时 15 毫秒
731.
Background. In the Danish Town Hall Study" it has previously been shown that the sick building syndrome is a widespread phenomenon. This has given rise to speculations as to whether biologically active components in dust or whether absorbed organic gases and vapours in the indoor climate may be partly responsible for the sick building syndrome. Therefore, we wished to study whether qualitative conditions in dust, of a physical, chemical, and biological nature, are related to the prevalence of symptoms of the sick building syndrome. Material and methods. The study included 12 town halls in the Copenhagen area. A total of 870 persons participated, 584 women and 286 men. All the participants filled out a questionnaire regarding health and working conditions, and dust samples were collected with a special vacuum cleaner in the working environment of the participants, after which the contents of inorganic and organic particles as well as of human source fragments the (hair, nails, skin) and various fibres were determined. Results. There was a significant correlation (P<0.05) between the prevalence of gram-negative bacteria in the indoor climate dust, and general symptoms (fatigue, heavy-headedness, headache, dizziness, concentration problems) (corr.coeff.=0.73), as well as symptoms from the mucous membranes of the upper respiratory tract (corr.coeff.=0.76). Also, there was a significant relation between the prevalence of particles in the dust and the prevalence of symptoms from the mucous membranes (corr.coeff.=0.81). There was a strong and significant correlation between the total amount of volatile organic components (TVOC) and lack of concentration (corr.coeff. =0.85) and feeling heavy-headed (corr.coeff.=0.72). Macromolecular dust (potentially allergenetic material) was significantly correlated to the prevalence of headache and general malaise/dizziness (corr.coeff.=0.66), while the ability of the dust to liberate histamine was significantly related to the prevalence of general malaise, dizziness (corr.coeff.=0.65) and lack of concentration (corr.coeff. =0.58). Further analyses including a number of potential confounders did not change the results of the above analyses. Conclusion. The results of this study support the hypothesis that qualitative properties of dust are important to the sick building syndrome. The study was based on relatively few buildings, but nevertheless strong correlations were found. In perspective, epidemiological intervention studies should be carried out to investigate whether minimizing the amount of both dust and bacteria in the indoor climate affect the prevalence of sick building syndrome.  相似文献   
732.
Green building materials are becoming more popular. However, little is known about their ability to support or limit microbial growth. The growth of fungi was evaluated on five building materials. Two green, two conventional building materials and wood as a positive control were selected. The materials were inoculated with Aspergillus versicolor, Cladosporium cladosporioides and Penicillium brevicompactum, in the absence and presence of house dust. Microbial growth was assessed at four different time points by cultivation and determining fungal biomass using the N‐acetylhexosaminidase (NAHA) enzyme assay. No clear differences were seen between green and conventional building materials in their susceptibility to support microbial growth. The presence of dust, an external source of nutrients, promoted growth of all the fungal species similarly on green and conventional materials. The results also showed a correlation coefficient ranging from 0.81 to 0.88 between NAHA activity and culturable counts. The results suggest that the growth of microbes on a material surface depends on the availability of organic matter rather than the classification of the material as green or conventional. NAHA activity and culturability correlated well indicating that the two methods used in the experiments gave similar trends for the growth of fungi on material surfaces.  相似文献   
733.
To mitigate dust contamination in the mine intake roadway, Computational Fluid Dynamics (CFD) study was first conducted to understand the ventilation and respirable dust flow behaviour above the bin. Based on the modelling results, two possible solutions were proposed for dust control, one is modifying the ventilation system to dilute the respirable dust particles, and the other is using water mist dust droppers to suppress and capture the majority of the dust particles. Modelling results indicated that respirable dust particles could be significantly diluted at the operators’ breathing level by increasing the ventilation volume from the horizontal air intake, where 10–13 m3/s of air flow rate was suggested to be a preferable quantity. The mechanism of respirable dust capture using water mist was investigated from classical theory and two phase flow theory, respectively, both of which demonstrated a good dust mitigation effect was achievable. CFD models were employed to investigate the flow behaviour of water mists when sprays were oriented at different directions above the bin. An innovative design of dust control system employing water mist technology with four nozzles was proposed and subsequently built for field implementation. An independent field dust evaluation demonstrated that a reduction up to 68% of respirable dust particles has been achieved in the vicinity of the underground bin, and an average of 40% respirable dust reduction along the belt roadway. The successful application of the new dust mitigation system also demonstrates its potential use in underground longwall faces, roadway development and subsurface tunnel excavations by roadheader.  相似文献   
734.
结合冲激式除尘器和泡沫式除尘器的工作原理。以较低成本对冲激式除尘器进行改造,降低除尘器的运行成本和提高除尘器的运行效率。  相似文献   
735.
This study aimed to determine the particulate matter concentrations (PM10) in workplace air and personal dust, and their effects on the respiratory health of exposed workers. The lung function of 449 exposed workers was examined. The concentration of PM10 in workplace air and personal dust exposure was measured. Spirometry was used to evaluate the lung function capacity included forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), forced expiratory volume ratio (FEV%) and peak expiratory flow rate (PEF). The forced expiratory flow at 25% to 75% of the FVC (FEF 25-75%) was determined. The PM10 concentration in workplace air (6 study sites) and personal dust (4 study sites) exceeded the standard (REL) of 0.12 mg/m3. The results of this study showed a decrease in the mean values and percent predicted value of FVC, FEV1, FEV1%, PEF and FEF 25-75%. The lung capacity of participants revealed that 24.50%, 4.45% and 7.13% had mildly, moderately restrictive and small airway disease. The respiratory symptoms were dyspnoea (22.49%), wheezing (10.69%), chest pain (10.69%) and chronic cough (2.90%). Factors influencing lung capacity included mask usage (Adj.OR: 0.44 CI: 0.25-0.79 p-value: 0.006) and chest pain (Adj.OR: 2.68 CI: 1.14-6.30 p-value: 0.024).  相似文献   
736.
We have long known that human occupants are a major source of microbes in the built environment, thus raising the question: How much can we learn about the occupants of a building by analyzing the microbial communities found in indoor air? We investigated bacterial and fungal diversity found in airborne dust collected onto heating, ventilation, and air‐conditioning (HVAC) air filters and settling plates from 91 rooms within a university dormitory. The sex of the room occupants had the most significant effect on the bacterial communities, while the room occupants had no significant effect on fungal communities. By examining the abundances of bacterial genera, we could predict the sex of room occupants with 79% accuracy, a finding that demonstrates the potential forensic applications of studying indoor air microbiology. We also identified which bacterial taxa were indicators of female and male rooms, and found that those taxa often identified as members of the vaginal microbiome were more common in female‐occupied rooms while taxa associated with human skin or the male urogenital microbiota were more common in male‐occupied rooms.  相似文献   
737.
本文介绍了TBM施工技术条件下,隧洞的通风设计与空气质量控制方法。  相似文献   
738.
通过几种除尘技术的对比分析,明确了湍冲洗涤静电除尘技术的工艺原理、技术优势和特点以及应用效果,并对在甲醇制烯烃除尘装置应用进行了适用性研究,为后续同类装置提供数据支撑和参考依据。  相似文献   
739.
The comparison of endotoxin levels between study populations and countries is limited as a result of differences in sampling, extraction, and storage procedures. The objective of this study is to assess the levels and determinants of endotoxin in mattress and living room floor dust samples from three European countries, namely, Germany, the Netherlands, and Sweden, using a standardized sampling, storage, and analysis protocol. The mattress and living room floor dust was collected from the homes of 1065 German, Dutch, and Swedish (pre-)school children. All the samples were collected in the cool season and analyzed for endotoxin in a central laboratory. The determinants were assessed by a standardized questionnaire. The endotoxin concentrations in mattress and living room floor dust were found to be the highest in German homes and lowest in the Swedish ones. Differences between the geometric means were small (factor 1.1-1.7). Most of the associations between endotoxin concentrations and potential determinants were not statistically significant and heterogeneous across countries. However, keeping pets and having more than four persons living in the home were consistently associated with up to 1.7-fold higher endotoxin concentrations in mattress and floor dust. Furthermore, having carpets or rugs, and opening the windows frequently was associated with up to 3.4-fold and 1.3-fold higher endotoxin concentrations in living room floor dust, respectively. The proportion of variance explained by the questionnaire variables was generally low. In conclusion, the data on housing characteristics did not accurately predict the endotoxin concentrations in house dust, and could only partly explain the differences between countries. PRACTICAL IMPLICATIONS: The differences between the endotoxin concentrations in German, Dutch, and Swedish homes are small. House dust endotoxin concentrations are associated with a number of housing factors, such as pet-ownership, floor cover, number of persons living in the home, and ventilation. The variability of the endotoxin levels between homes and countries can only be partly explained by these factors.  相似文献   
740.
提高闪速炉烟气收尘效果的实践   总被引:1,自引:0,他引:1  
就贵溪冶炼厂三期改造后闪速炉烟气收尘系统出现的问题进行了分析,并对提高收尘效率等一系列技术改造进行了总结。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号