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   208篇
  免费   16篇
电工技术   3篇
化学工业   44篇
金属工艺   3篇
机械仪表   2篇
建筑科学   8篇
能源动力   5篇
轻工业   13篇
水利工程   4篇
无线电   24篇
一般工业技术   40篇
冶金工业   41篇
原子能技术   1篇
自动化技术   36篇
  2024年   1篇
  2023年   9篇
  2022年   12篇
  2021年   15篇
  2020年   7篇
  2019年   11篇
  2018年   13篇
  2017年   11篇
  2016年   5篇
  2015年   5篇
  2014年   11篇
  2013年   18篇
  2012年   12篇
  2011年   15篇
  2010年   6篇
  2009年   4篇
  2008年   7篇
  2007年   8篇
  2006年   9篇
  2005年   7篇
  2004年   4篇
  2003年   7篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   2篇
  1995年   5篇
  1993年   1篇
  1992年   3篇
  1989年   1篇
  1986年   2篇
  1983年   1篇
  1979年   1篇
排序方式: 共有224条查询结果,搜索用时 23 毫秒
41.
A series of studies further explored the way in which irrelevant sound disrupts the serial recall of visually presented verbal sequences. The hypothesis that distinctiveness (stimulus mismatch) within auditory irrelevant sequences is a critical determinant of disruption of serial recall was tested. Experiment 1 showed that the degree of disruption was related to the degree of mismatch between successive stimuli. However, in Experiment 2, changes in 2 attributes of a stimulus produced less disruption than when only 1 was changed, suggesting mismatch alone was not the key factor. These results were reconciled with the changing-state hypothesis in Experiment 3 in which change and disruption were monotonically related up to the point at which mismatch created 2 streams. Object-based theories are able to explain this pattern of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
42.
Task-irrelevant background sound disrupts serial recall. One account of this effect assumes that irrelevant events close to or during the presentation of a to-be-remembered list will interfere by disrupting temporal codes. A second account predicts that disruption will be greatest when the burden on rehearsal is high, as order cues in the auditory sequence interfere with those in the memory set. The authors tested these predictions by restricting the sound to different phases of the serial recall task. Sound presented just before the list and sound presented early in list presentation did not disrupt recall, but sound presented late in the list or after list presentation produced significant disruption. Sound presented after the list was more disruptive of recall for early list items than sound presented at the same time as those items. An account based on disruption of serial rehearsal, not the disruption of temporal codes, is supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
Cytochromes P450 (CYP) are one of the major xenobiotic metabolizing enzymes with increasing importance in pharmacogenetics. The CYP2C9 enzyme is responsible for the metabolism of a wide range of clinical drugs. More than sixty genetic variations have been identified in CYP2C9 with many demonstrating reduced activity compared to the wild-type (WT) enzyme. The CYP2C9*8 allele is predominantly found in persons of African ancestry and results in altered clearance of several drug substrates of CYP2C9. The X-ray crystal structure of CYP2C9*8, which represents an amino acid variation from arginine to histidine at position 150 (R150H), was solved in complex with losartan. The overall conformation of the CYP2C9*8-losartan complex was similar to the previously solved complex with wild type (WT) protein, but it differs in the occupancy of losartan. One molecule of losartan was bound in the active site and another on the surface in an identical orientation to that observed in the WT complex. However, unlike the WT structure, the losartan in the access channel was not observed in the *8 complex. Furthermore, isothermal titration calorimetry studies illustrated weaker binding of losartan to *8 compared to WT. Interestingly, the CYP2C9*8 interaction with losartan was not as weak as the CYP2C9*3 variant, which showed up to three-fold weaker average dissociation constant compared to the WT. Taken together, the structural and solution characterization yields insights into the similarities and differences of losartan binding to CYP2C9 variants and provides a useful framework for probing the role of amino acid substitution and substrate dependent activity.  相似文献   
44.
TAAR1 is a neuroregulator with emerging evidence suggesting a role in immunomodulation. Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system. Here, we investigate TAAR1 expression in human primary monocytes, peripherally-derived macrophages, and MS brain tissue. RT-qPCR was used to assess TAAR1 levels in MS monocytes. Using a previously validated anti-human TAAR1 antibody and fluorescence microscopy, TAAR1 protein was visualized in lipopolysaccharide-stimulated or basal human macrophages, as well as macrophage/microglia populations surrounding, bordering, and within a mixed active/inactive MS lesion. In vivo, TAAR1 mRNA expression was significantly lower in MS monocytes compared to age- and sex-matched healthy controls. In vitro, TAAR1 protein showed a predominant nuclear localization in quiescent/control macrophages with a shift to a diffuse intracellular distribution following lipopolysaccharide-induced activation. In brain tissue, TAAR1 protein was predominantly expressed in macrophages/microglia within the border region of mixed active/inactive MS lesions. Considering that TAAR1-mediated anti-inflammatory effects have been previously reported, decreased mRNA in MS patients suggests possible pathophysiologic relevance. A shift in TAAR1 localization following pro-inflammatory activation suggests its function is altered in pro-inflammatory states, while TAAR1-expressing macrophages/microglia bordering an MS lesion supports TAAR1 as a novel pharmacological target in cells directly implicated in MS neuroinflammation.  相似文献   
45.
Evidence-based profiling of obesity and overweight in Indigenous Australian children has been poor. This study systematically reviewed evidence of the prevalence and patterns of obesity/overweight, with respect to gender, age, remoteness, and birth weight, in Indigenous Australian children, 0–18 years (PROSPERO CRD42014007626). Study quality and risk of bias were assessed. Twenty-five publications (21 studies) met inclusion criteria, with large variations in prevalence for obesity or overweight (11 to 54%) reported. A high degree of heterogeneity in study design was observed, few studies (6/21) were representative of the target population, and few appropriately recruited Indigenous children (8/21). Variability in study design, conduct, and small sample sizes mean that it is not possible to derive a single estimate for prevalence although two high-quality studies indicate at least one in four Indigenous Australian children are overweight or obese. Four of six studies reporting on gender, found overweight/obesity higher in girls and eight studies reporting on overweight/obesity by age suggest prevalence increases with age with one high quality large national study reporting total overweight/obesity as 22.4% of children aged 2–4 years, 27.5% of those aged 5–9, 38.5% aged 10–14, and 36.3% aged 15–17. Three of four studies, reporting obesity/overweight by region, found lower rates for children living in more remote areas than urban areas.  相似文献   
46.
We used an ensemble of aircraft measurements with the GEOS-Chem chemical transport model to constrain present-day North American ethanol sources, and gauge potential long-range impacts of increased ethanol fuel use. We find that current ethanol emissions are underestimated by 50% in Western North America, and overestimated by a factor of 2 in the east. Our best estimate for year-2005 North American ethanol emissions is 670 GgC/y, with 440 GgC/y from the continental U.S. We apply these optimized source estimates to investigate two scenarios for increased ethanol fuel use in the U.S.: one that assumes a complete transition from gasoline to E85 fuel, and one tied to the biofuel requirements of the U.S. Energy Indepence and Security Act (EISA). For both scenarios, increased ethanol emissions lead to higher atmospheric acetaldehyde concentrations (by up to 14% during winter for the All-E85 scenario and 2% for the EISA scenario) and an associated shift in reactive nitrogen partitioning reflected by an increase in the peroxyacetyl nitrate (PAN) to NO(y) ratio. The largest relative impacts occur during fall, winter, and spring because of large natural emissions of ethanol and other organic compounds during summer. Projected changes in atmospheric PAN reflect a balance between an increased supply of peroxyacetyl radicals from acetaldehyde oxidation, and the lower NO(x) emissions for E85 relative to gasoline vehicles. The net effect is a general PAN increase in fall through spring, and a weak decrease over the U.S. Southeast and the Atlantic Ocean during summer. Predicted NO(x) concentrations decrease in surface air over North America (by as much 5% in the All-E85 scenario). Downwind of North America this effect is counteracted by higher NO(x) export efficiency driven by increased PAN production and transport. From the point of view of NO(x) export from North America, the increased PAN formation associated with E85 fuel use thus acts to offset the associated lower NO(x) emissions.  相似文献   
47.
Self-healing was achieved with a dual-microcapsule epoxy-amine chemistry in thermoset epoxy. One capsule contained a modified aliphatic polyamine (EPIKURE 3274) while the second capsule contained a diluted epoxy monomer (EPON 815C). Amine microcapsules were prepared by vacuum infiltration of EPIKURE 3274 into hollow polymeric microcapsules. Epoxy microcapsules were prepared by an in situ polymerization method. Both types of capsules were incorporated into an epoxy matrix (EPON 828:DETA) and recovery of mode-I fracture toughness was measured using tapered-double-cantilever-beam (TDCB) specimens. The optimal mass ratio of amine: epoxy capsules was 4: 6 and an average healing efficiency of 91% was achieved with 7 wt% amine capsules and 10.5 wt% epoxy capsules. Long-term stability of the healing system was demonstrated for six months at ambient conditions. Thermal stability was investigated by post curing samples at 121 °C and assessing healing performance.  相似文献   
48.
Potential characterization of deflected piezoelectric nanowires (NWs) is of great interest for current development of electromechanical nanogenerators that harvest ambient mechanical energy. In this paper, a Kelvin probe microscopy (KPM) technique hybridizing scanning KPM (SKPM) with atomic force microscope (AFM) surface‐approach spectroscopy methods for characterizing in‐plane piezoelectric potential of ZnO microwires (MWs) is presented. This technique decouples the scanning motion of the AFM tip from sample topography, and thus effectively eliminates artifacts induced by high topographical variations along the edges of MWs/NWs which make characterization by conventional SKPM inappropriate or impossible. By virtue of the topography/tip motion decoupling approach, the electrical potential can also be mapped in a three‐dimensional (3D) spatial volume above the sample surface. Therefore, this technique is named 3DKPM. Through 3DKPM mapping, the piezopotential generated by a laterally deflected ZnO MW was determined by extracting the potential asymmetry from opposite sides of the MW. The measurement results agree well with theoretical predictions. Integrating an external bias to the MW sample allowed direct observation of piezopotential and carrier concentration coupling phenomenon in ZnO, opening a door toward quantitative microscopic investigation of the piezotronic effect. With further positioning refinements, 3DKPM could become a powerful technique for the characterization of piezoelectric potential and related effects in micro/nanostructures of high topographical variations, as well as development of MW/NW‐based piezoelectric nanodevices.  相似文献   
49.
BACKGROUND: Little is known about the relative reliability of medical record and clinical automated data, sources commonly used to assess diabetes quality of care. The agreement between diabetes quality measures constructed from clinical automated versus medical record data sources was compared, and the performance of hybrid measures derived from a combination of the two data sources was examined. METHODS: Medical records were abstracted for 1,032 patients with diabetes who received care from 21 facilities in 4 Veterans Integrated Service Networks. Automated data were obtained from a central Veterans Health Administration diabetes registry containing information on laboratory tests and medication use. RESULTS: Success rates were higher for process measures derived from medical record data than from automated data, but no substantial differences among data sources were found for the intermediate outcome measures. Agreement for measures derived from the medical record compared with automated data was moderate for process measures but high for intermediate outcome measures. Hybrid measures yielded success rates similar to those of medical record-based measures but would have required about 50% fewer chart reviews. CONCLUSIONS: Agreement between medical record and automated data was generally high. Yet even in an integrated health care system with sophisticated information technology, automated data tended to underestimate the success rate in technical process measures for diabetes care and yielded different quartile performance rankings for facilities. Applying hybrid methodology yielded results consistent with the medical record but required less data to come from medical record reviews.  相似文献   
50.
The functional characteristics of auditory temporal-spatial short-term memory were explored in 8 experiments in which the to-be-remembered stimuli were sequences of bursts of white noise presented in spatial locations separated in azimuth. Primacy and recency effects were observed in all experiments. A 10-s delay impaired recall for primacy and middle list items but not recency. This effect was shown not to depend on the response modality or on the incidence of omissions or repetitions. Verbal and nonverbal secondary tasks did not affect memory for auditory spatial sounds. Temporal errors rather than spatial errors predominated, suggesting that participants were engaged in a process of maintaining order. This pattern of results may reflect characteristics that serial recall has in common with verbal and spatial recall, but some are unique to the representation of memory for temporal-spatial auditory events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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