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   26篇
  免费   0篇
化学工业   2篇
建筑科学   1篇
轻工业   8篇
无线电   2篇
冶金工业   13篇
  2014年   1篇
  2012年   4篇
  2011年   1篇
  2008年   3篇
  2006年   1篇
  2005年   2篇
  2004年   1篇
  1999年   1篇
  1998年   3篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
The collapse of Soviet Union in early 1990s led to abandonment of large area of arable land which is assumed to act as a carbon (C) sink. We studied the ability of two dynamic soil C models (Yasso07 and RothC) to predict changes in soil C content after cropland abandonment. The performance of the models was compared using the results of a long-term experiment in Pushchino, Moscow region (54°50′N, 37°35′E) in Russia. The experiment was divided in four combinations of fertilizer or mowing treatments on former cropland soil. The soil C content was determined in the year of establishment (1980) and thereafter in 1999 and 2004. The soil C stocks increased by about 1.5- to 1.8-fold during the study period. Both models predicted the overall change in soil C relatively well (modelling efficiency of Yasso07 and RothC were 0.60 and 0.73, respectively). According to the models, the soil gained on average 140–150 g C m?2 year?1 during the first 5 years after conversion of cropland to grassland. The C sequestration rate decreased to 40–50 g C m?2 year?1 after 20 years of land use change. The sequestration rates estimated in this study are comparable to the rates observed in other studies.  相似文献   
2.
A nationwide outbreak of Salmonella enterica serotypes Newport and Reading occurred between 17 October and 28 November 2008 in Finland. A total of 77 culture-confirmed Salmonella Newport and 30 Salmonella Reading cases, including one case with a double infection, were reported. All strains isolated from the patients were subtyped using serotyping, microbial resistance profiling, and pulsed-field gel electrophoresis (PFGE). Here, the PFGE patterns of the studied Salmonella Newport strains were identical, whereas four different PFGE profiles were found among the Salmonella Reading strains. Two elderly patients died within 2 weeks of the onset of symptoms. Three geographical clusters of cases with an epidemiological link were identified. The traceback investigation suggested that the factor connecting the cases was ready-chopped iceberg lettuce available for mass catering use. However, none of the tested food, environmental samples, or the samples taken from the staff of the processing plant contained Salmonella bacteria. Tracing back to outbreak sources with a short shelf life can be complex.  相似文献   
3.
The present study is aimed at examining the combined effects of effort-reward imbalance (ERI), overcommitment (OVC), and perceived organizational support (POS) on turnover intentions and work engagement, among Finnish managers (n = 1,301). Consequently, the study contributes to the research literature by examining how the ERI-outcomes relationship was dependent simultaneously on OVC and POS. The results showed that ERI × OVC × POS interaction was significant only for turnover intentions. The ERI-turnover intentions relationship was strongest under conditions of high OVC and low POS. In addition, the relationship between ERI and decreased work engagement, especially dedication, was strengthened among overcommitted managers, compared to their less committed counterparts. Altogether, the results indicate that interventions aimed at reducing turnover intentions and increasing work engagement by increasing ERI should consider OVC and POS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
Previous research has linked depression to difficulties in smoking cessation. The authors followed 269 smokers who attempted to quit smoking for 3 months. Participants were given nicotine gum (2 or 4 mg) or placebo gum and brief counseling. The study found that 34% of the smokers met the criterion for current depression using the Center for Epidemiological Studies Depression Scale. Depressed smokers relapsed significantly earlier than the nondepressed. Nicotine gum was significantly more effective than placebo gum among all smokers. The benefits of nicotine gum were particularly apparent among the depressed. Only 12.5% of depressed smokers quit successfully with placebo gum for 3 months, whereas 29.5% quit with nicotine gum. Depressed smokers reported more stress, less coping resources, more physical and psychological symptoms, and more frequent smoking in the presence of negative affect than did the nondepressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
IgE and IgG subclass antibodies against Aedes communis mosquito saliva were studied by immunoblotting in 12 adults with immediate and/or delayed skin reactions to mosquito bites. Four antigenic proteins, with molecular weights of 22, 30, 36, and 64 kd, were found in the mosquito saliva. Almost all subjects (11 of 12) had anti-mosquito saliva-specific IgE antibodies directed against the 36 kd protein. The IgG antibody response appeared to be restricted mostly to IgG4 (11 of 12) and IgG1 (8 of 11) subclasses against the same 36 kd antigen. Ten of the 12 subjects had both IgE and IgG4 antibodies to the 36 kd protein. No anti-mosquito antibodies were found in pooled sera of five infants never exposed to mosquito bites. These results show that most persons with immediate skin reactivity to A. communis mosquito bites have both IgE and IgG4 antibodies that recognize the 36 kd antigen present in the mosquito saliva, suggesting that anti-saliva antibodies may play a role in the pathogenesis of mosquito bite reactions.  相似文献   
6.
Low-loss optical fibers are now indispensable transmission media for transmission systems. Recently, the ultralow-loss performance for long transmission systems, the water-loss-free performance for wide-band wavelength-division-multiplexing (WDM) systems, the hydrogen-loss-insensitive performance for system reliability, and the bending-loss-insensitive performance for access or indoor applications have attracted much interest. In this regard, pure-silica-core fibers (PSCFs) are suitable, and unprecedented low-loss PSCFs have been successfully fabricated. This paper introduces the recent progress of low-loss PSCFs and their possible impact on transmission systems.  相似文献   
7.
Microfiltered native whey protein (MFNW) exerts superior in vitro functional properties compared to traditional cheese whey protein. We here investigated the metabolic effects of a novel MFNW, produced by economic polymeric membranes and rich in α-lactalbumin (α-lactalbumin 24% and β-lactoglobulin 65% of the protein), in a mice model of diet-induced obesity during weight gain and weight loss. Furthermore, the effects of MFNW were compared with those of α-lactalbumin. Replacement of casein in the diet (18% of energy) by MFNW prevented weight gain and body fat accumulation without influencing food intake, body temperature or glucose homeostasis. However, the anti-obesity effect of MFNW was inferior compared to α-lactalbumin (approximately 1/3). During weight loss (70% of ad libitum energy intake) the beneficial effects of both MFNW and α-lactalbumin were attenuated. Our findings indicate that MFNW protects against diet-induced obesity, and suggest that the beneficial effects of MFNW are due, to a great extent, to its α-lactalbumin content.  相似文献   
8.
Research has suggested that race, gender, and menthol cigarette use influence tobacco-smoke exposure measures and smoking-related disease risk. For example, a high proportion of Black smokers prefer menthol cigarettes and, despite smoking fewer cigarettes per day (CPD) than do Whites, tend to have higher cotinine levels. Additionally, Black males are more at risk for smoking-related lung cancer. High cotinine levels and smoking menthol cigarettes may lead to higher toxin intake, which contributes to increased disease risk. We explored the relationship between tobacco exposure variables (i.e., cotinine, CPD, carbon monoxide [CO], nicotine content, and nicotine dependence) with respect to race, gender, and menthol content in a sample of 307 smokers recruited from the greater Boston area to participate in a smoking cessation treatment trial. The pattern of correlations between tobacco exposure measures and cotinine showed a consistently positive correlation between cotinine and CO in all smokers and a correlation between cotinine and CPD in those who smoked nonmenthol cigarettes. Cotinine and CPD correlations varied by gender and race among menthol cigarette smokers. Consistently, we found a significant gender x race x menthol interaction on salivary cotinine level as well as cotinine/CPD ratio. These findings suggest that the relationship between number of cigarettes consumed and salivary cotinine is more complex than previously believed. It is not sufficient to look at race alone; researchers and clinicians need to look at race and gender concurrently, as well as type of cigarette consumed.  相似文献   
9.
The performance of two immunoturbidimetric modifications for rheumatoid factor (RF) testing, which differ with respect to the means of complement inactivation (heat treatment and inactivation with polyvinyl sulphonate), were compared in serum samples from 87 patients with rheumatoid arthritis (RA) and from 403 healthy subjects. IgM-rheumatoid factor titres were also measured with an enzyme linked immunosorbent assay (ELISA). Both immunoturbidimetric tests gave positive reactions (rheumatoid factor > or = 20 IU/ml) in 74 out of the 87 (85%) RA sera. In cases with high RF concentrations the results after chemical inactivation tended to be slightly higher compared with heat inactivation. In healthy subjects rheumatoid factor was detected in 19/403 (4.7%) sera using heat inactivation and in 22/403 (5.5%) sera with chemical inactivation of complement. Interrun coefficient of variation in the chemical inactivation assay was 4.4%; with the heat inactivation method it was 8.1%. In the ELISA, a marginally better correlation was noted in the results obtained using chemical inactivation. Inactivation of complement by means of polyvinyl sulphonate offers the advantage of easier test performance and better reproducibility, and the results may reflect more accurately true rheumatoid factor concentrations.  相似文献   
10.
The Port of Kotka is situated by the Baltic Sea and the river Kymi. The river transports into the estuary sediments containing pollutants. The dredging and dumping of the polluted sediments are challenging tasks, which are strictly monitored by the environmental authorities. In this study, we show how a former dumping area was converted into a car storage area in an innovative way. The construction on wetland base was extremely challenging. The field was built by using tyre scrap, which weighs only a quarter of the stone material's weight. The advantage of frost season was used during the construction phase, which reduces the costs. The Port of Kotka's solution to use polluted dredged material and waste material, in order to economically reclaim new land, sets a good example that can be used in other ports as well.  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