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   174篇
  免费   4篇
电工技术   1篇
化学工业   15篇
金属工艺   2篇
机械仪表   2篇
建筑科学   14篇
能源动力   1篇
轻工业   17篇
无线电   10篇
一般工业技术   9篇
冶金工业   89篇
自动化技术   18篇
  2024年   1篇
  2022年   1篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   3篇
  2017年   1篇
  2016年   6篇
  2013年   4篇
  2012年   3篇
  2011年   8篇
  2010年   15篇
  2009年   5篇
  2008年   5篇
  2007年   4篇
  2006年   3篇
  2005年   3篇
  2004年   8篇
  2003年   5篇
  2002年   4篇
  2001年   2篇
  2000年   5篇
  1999年   2篇
  1998年   20篇
  1997年   9篇
  1996年   10篇
  1995年   5篇
  1994年   2篇
  1993年   6篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1988年   2篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1976年   2篇
  1972年   1篇
  1966年   2篇
排序方式: 共有178条查询结果,搜索用时 15 毫秒
31.
A possible removal mechanism for fragrance materials (FMs) in wastewater is adsorption to sludge, and sludge application to land may be a route through which FMs are released to the soil environment. However, little is known about the concentrations and fate of FMs in soil receiving sludge application. This study was conducted to better understand the dissipation of FMs in sludge-amended soils. We first determined the spiking and extraction efficiencies for 22 FMs in soil and leachate samples. Nine FMs were detected in digested sludges from two wastewater treatment plants in Delaware using these methods. We conducted a 1-year die-away experiment which involved four different soils amended with sludge, with and without spiking of the 22 FMs. The initial dissipation of FMs in all spiked trays was rapid, and only seven FMs remained at concentrations above the quantification limits after 3 months: AHTN, HHCB, musk ketone, musk xylene, acetyl cedrene, OTNE, and DPMI. After 1 year, the only FMs remaining in all spiked trays were musk ketone and AHTN. DPMI was the only FM that leached significantly from the spiked trays, and no FMs were detected in leachate from any unspiked tray. While soil organic matter content affected the dissipation rate in general, different mechanisms (volatilization, transformation, leaching) appeared to be important for different FMs.  相似文献   
32.
Random effects models were used to examine the association between behavioral disturbances in persons with Alzheimer's disease (N = 90) and caregiver depressive symptoms at 2-month intervals over an 18-month period. There was substantial variability in trajectories of change in caregiver depressive symptoms over time but no systematic increase in distress despite increased severity of dementia symptoms. Total behavioral disturbances were associated with higher levels of caregiver depressive symptoms: this effect was primarily attributable to aggressive behaviors. No consistent departure from linearity was evident in the relationship between behavior and depression over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
33.
Carpenters and other construction workers who install drywall have high rates of strains and sprains to the low back and shoulder. Drywall is heavy and awkward to handle resulting in increased risk of injury. The purpose of this study was to evaluate several low-cost coupling tools that have the potential to reduce awkward postures in drywall installers. Five coupling tools were evaluated using the Lumbar Motion Monitor that measures trunk kinematics and predicts probability of low back disorder group membership risk (LBD risk). Workers answered surveys about their comfort while using each tool. The results indicate that use of the 2-person manual lift and the J-handle provide the best reduction in awkward postures, motions, low back sagittal moment, and LBD risk. The two-person manual lift appears to be the safest method of lifting and moving drywall, though using the two-person J-handle also significantly reduces injury risk. Given that carpenters are skeptical about using equipment that can get in the way or get lost, a practical recommendation is promotion of two-person manual lifting. For single-person lifts, the Old Man tool is a viable option to decrease risk of MSDs.  相似文献   
34.
The intramolecular hydroamination of aminoalkynes and unactivated aminoalkenes catalyzed by yttrium N,O‐ and N,N‐complexes has been investigated. The N,N‐yttrium complexes are highly active, catalyzing the conversion of a wide range of terminal aminoalkenes at room temperature, and internal aminoalkenes at elevated temperature, to yield pyrrolidine and piperidine products in high yields. A high diastereoselectivity of up to 23:1 is observed at 0 °C with 1‐methyl‐4‐pentenylamine as substrate.  相似文献   
35.
Targeted delivery of the chemotherapeutic agent methotrexate (MTX) to cancer cells using poly(ethyleneimine)‐functionalized mesoporous silica particles as drug‐delivery vectors is reported. Due to its high affinity for folate receptors, the expression of which is elevated in cancer cells, MTX serves as both a targeting ligand and a cytotoxic agent. Enhanced cancer‐cell apoptosis (programmed cell death) relative to free MTX is thus observed at particle concentrations where nonspecific MTX‐induced apoptosis is not observed in the nontargeted healthy cell line, while corresponding amounts of free drug affect both cell lines equally. The particles remain compartmentalized in endo‐/lysosomes during the time of observation (up to 72 h), while the drug is released from the particle only upon cell entry, thereby inducing selective apoptosis in the target cells. As MTX is mainly attached to the particle surface, an additional advantage is that the presented carrier design allows for adsorption (loading) of additional drugs into the pore network for therapies based on a combination of drugs.  相似文献   
36.
This study examined trajectories of cognitive change in psychometrically matched measures of episodic memory, semantic memory, and executive function in an ethnically, demographically, and cognitively diverse sample of older persons. Individual rates of change showed considerable heterogeneity in each domain. Baseline clinical diagnosis predicted differential change in semantic memory and executive function, dementia > mild cognitive impairment (MCI) > normal, but average decline in verbal episodic memory was similar across all 3 diagnostic groups. There was substantial overlap of distributions of cognitive change across baseline diagnostic groups for all 3 measures. Cognitive change was strongly related to change in clinical diagnosis. Rapid and similar change was present for all 3 cognitive measures in patients with dementia and in those with normal cognition and those with MCI who progressed clinically. In cognitively normal patients, verbal episodic memory change was greater than change in the other two domains. Global status, measured by the Clinical Dementia Rating scale (Morris, 1993), predicted change in semantic memory and executive function, whereas APOE genotype predicted change in verbal episodic memory, and age had no effect on rates of change in any domain independent of global status and APOE. Results show important limitations in using cross-sectional diagnosis to predict prognosis and suggest that research to identify robust predictors of cognitive change across the full spectrum from normal to dementia is needed for better early identification of diseases that cause progressive decline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
37.
Fiedler and Kareev (2006) have claimed that taking a small sample of information (as opposed to a large one) can, in certain specific situations, lead to greater accuracy—beyond that gained by avoiding fatigue or overload. Specifically, they have argued that the propensity of small samples to provide more extreme evidence is sufficient to create an accuracy advantage in situations of high caution and uncertainty. However, a close examination of Fiedler and Kareev's experimental results does not reveal any strong reason to conclude that small samples can cause greater accuracy. We argue that the negative correlation between sample size and accuracy that they reported (found only for the second half of Experiment 1) is also consistent with mental fatigue and that their data in general are consistent with the causal structure opposite to the one they suggest: Rather than small samples causing clear data, early clear data may cause participants to stop sampling. More importantly, Experiment 2 provides unequivocal evidence that large samples result in greater accuracy; Fiedler and Kareev only found a small sample advantage here when they artificially reduced the data set. Finally, we examine the model that Fiedler and Kareev used; they surmised that decision makers operate with a fixed threshold independent of sample size. We discuss evidence for an alternative (better performing) model that incorporates a dynamic threshold that lowers with sample size. We conclude that there is no evidence currently to suggest that humans benefit from taking a small sample, other than as a tactic for avoiding fatigue, overload, and/or opportunity cost—that is, there is no accuracy advantage inherent to small samples. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
38.
As part of ongoing cooperation between the City of Phoenix and Arizona State University, a charrette was organized. Planners, landscape architects, environmental scientists, and architects explored concepts for development within a 110-square-mile (285-km2) portion of Phoenix. The charrette was the summation of over a year of environment studies of the planning area. This part of northern Phoenix occupies a largely undeveloped upper Sonoran desert landscape experiencing intense development pressure. Four charrette teams addressed desert preservation, rural desert development, suburban desert development, and growth corridors. This article focuses on some of the strategies proposed by the suburban desert development team. One of these called for an alternative pattern of development aligned with natural drainage corridors. Several concepts from the charrette and findings from the environmental research were adopted by the City in the revised general plan for the area.  相似文献   
39.
The extent of children's exposure to multiple toxic metals is not well described in many developing countries. We examined metal exposures in young children (6-37 months) from Montevideo, Uruguay and their mothers (15-47 years) participating in a community-based study. Hair samples collected from 180 children and their mothers were analyzed for: lead (Pb), cadmium (Cd), manganese (Mn), and arsenic (As) concentration using inductively coupled plasma-mass spectrometry (ICP-MS). Median metal levels (μg/g) were: Pb 13.69, Mn 1.45, Cd 0.17, and As 0.09 for children and Pb 4.27, Mn 1.42, Cd 0.08, and As 0.02 for mothers. Of the child and maternal samples, 1.7% and 2.9% were below the limit of detection (LOD) for Cd, and 21.3% and 38.5% were below the LOD for As, respectively. Correlations between maternal and child levels ranged 0.38-0.55 (p < 0.01). Maternal hair metal levels were the strongest predictors of metal concentrations in children's hair. Girls had significantly lower As levels than boys (p < 0.01) but did not differ on other metals. In addition, in bivariate logistic regressions predicting the likelihood that the child would be exposed to multiple metals, hemoglobin < 10.5 g/dL (OR = 2.12, p < 0.05), blood lead (OR = 1.17, p < 0.01), and the mother being exposed to two or more metals (OR = 3.34, p < 0.01) were identified as significant predictors of increased likelihood of multiple metal exposure. Older child age (OR = 0.96, p < 0.05), higher maternal education (OR = 0.35, p < 0.01), and higher number of household possessions (OR = 0.83, p < 0.01) were significantly associated with decreased likelihood of multiple metal exposure. Preschool children in Uruguay are exposed to multiple metals at levels that in other studies have been associated with cognitive and behavioral deficits. Sources of exposure, as well as cognitive and behavioral consequences of multiple metal exposure, should be investigated in this population.  相似文献   
40.
For Middle Eastern migrants to Australia, the process of acculturation is compounded by Islamophobia, which is on the rise, with many incidents occurring in public spaces and targeting women. Through in-depth interviews, this paper examines how women migrants from the Middle East, especially Muslim ones, are affected. The study finds that Middle Eastern women migrants have a different perspective on public space compared to local populations, and this difference stems from their cultural, political and religious backgrounds. These findings can help cities create inclusive and culturally-sensitive public spaces, which catalyze a ‘sense of belonging’ and ‘sense of place’ among migrants.  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