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   738篇
  免费   9篇
  国内免费   3篇
电工技术   9篇
化学工业   96篇
金属工艺   10篇
机械仪表   33篇
建筑科学   38篇
矿业工程   2篇
能源动力   9篇
轻工业   38篇
水利工程   1篇
石油天然气   1篇
无线电   66篇
一般工业技术   137篇
冶金工业   232篇
原子能技术   5篇
自动化技术   73篇
  2022年   6篇
  2021年   10篇
  2020年   9篇
  2019年   8篇
  2018年   8篇
  2017年   7篇
  2016年   6篇
  2015年   8篇
  2014年   16篇
  2013年   44篇
  2012年   15篇
  2011年   25篇
  2010年   27篇
  2009年   12篇
  2008年   16篇
  2007年   35篇
  2006年   22篇
  2005年   16篇
  2004年   14篇
  2003年   12篇
  2002年   15篇
  2001年   13篇
  2000年   7篇
  1999年   13篇
  1998年   48篇
  1997年   37篇
  1996年   29篇
  1995年   23篇
  1994年   21篇
  1993年   21篇
  1992年   5篇
  1991年   6篇
  1990年   4篇
  1989年   7篇
  1988年   12篇
  1987年   7篇
  1986年   9篇
  1985年   10篇
  1984年   10篇
  1983年   12篇
  1982年   9篇
  1981年   12篇
  1980年   15篇
  1979年   12篇
  1978年   9篇
  1977年   10篇
  1976年   19篇
  1975年   4篇
  1973年   4篇
  1970年   4篇
排序方式: 共有750条查询结果,搜索用时 11 毫秒
51.
Grouping the studies under the general topic headings of techniques of measurement, analysis of the reading process, training to improve eye movements, typography and eye movements, and eye movements and fatigue the author reviews the relevant research literature which has appeared since January, 1945. In general there has been a dimunition of interest in this area. However, there has appeared a large amount of work on visual fixation, speed of eye movements, reaction time of the eye, oculomotor efficiency, and vision during eye movements. There is a need for more basic research. 72-item bibliography. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
52.
This paper estimates the cost of mastitis for the New York dairy sector. The average cost is found to be $125 per cow from reduced milk production, treatment, and increased culling. At the 1988 cow inventory, this translates to approximately $100 million annually for the entire dairy farm sector. When quality and production losses for the processing sector are added, the cost to the New York industry alone is nearly $150 million annually. Two promising new treatments, a bacteriocin and a vaccine, are evaluated. Both have shown effectiveness in preliminary trials against Staphylococcus aureus. Assuming that further development will allow the treatments to be effective against the major bacterial sources of mastitis infections, the treatments are projected to increase the annual income of the New York dairy industry by $18.8 to $39.7 million. The bacteriocin could replace antibiotic usage, a desirable goal in the opinion of many, and the vaccine promises to immunize cows against mastitis very effectively.  相似文献   
53.
An accurate calculation of the size distribution of coarse particles is crucial in the mining and quarrying industry. Machine vision has the capability to overcome many inherent limitations of traditional sieving methods and is an active research area. However, inaccurate image segmentation of particles through software based algorithms is a significant source of error. In this paper, a hardware based approach to improving image segmentation is demonstrated using multi-flash Imaging (MFI), where multiple images captured with different illumination allows depth edges around a particle to be captured through shadow information. The MFI method is compared with conventional segmentation methods such as watershed and Canny edge detection. In order to provide more accurate evaluation of performance wooden spheres of known diameter were evaluated. Imaging the size distribution of pebbles provided a practical scenario in the evaluation of MFI. The results revealed that MFI produced more accurate size estimations than conventional segmentation techniques for both the wooden spheres and pebbles, demonstrating the potential for future use in the mining industry.  相似文献   
54.
Schottky barrier diodes have been integrated into on-chip rectangular waveguides. Two novel techniques have been developed to fabricate diodes with posts suitable for integration into waveguides. One technique produces diodes with anode diameters of the order of microns with post heights from 90 to 125 microns and the second technique produces sub-micron anodes with post heights around 20 microns. A method has been developed to incorporate these structures into a rectangular waveguide and provide a top contact onto the anode which could be used as an I.F. output in a mixer circuit. Devices have been fabricated and D.C. characterized.  相似文献   
55.
Residuum lodges comprise small dams constructed on feeder streams immediately before they enter a reservoir, behind which ponds form, where sediment is deposited. Despite their construction on many impoundment reservoirs (IRE) and catchwaters, little research has previously investigated their efficacy at removing sediments from feeder streams. The current pilot study has, therefore, been carried out at an IRE supplying Halifax, West Yorkshire, UK, where a residuum lodge was recently cleaned out. Sediment concentrations reaching the reservoir were reduced by up to 42% although no certain impacts were noted on the other water quality variables that were measured. Moreover, it was found that the clearance operation did not result in the release of excessive quantities of sediment into the reservoir. It was estimated that the cleared residuum lodge would take 12 years to refill. A survey of other residuum lodges in the Yorkshire region showed there to be considerable differences in their remaining capacities.  相似文献   
56.
This study examined the reliability and validity of the Mississippi Scale for Combat-Related Posttraumatic Stress Disorder (M-PTSD) in a sample of Vietnam combat veterans with PTSD (n?=?101) and substance-abusing patients without combat-related PTSD (n?=?102). The M-PTSD was found to have high internal consistency, and a principle-components analysis indicated that its items measure three dimensions: intrusive reexperiencing/numbing-avoidance, anger/lability, and social alienation. Discriminant validity of the M-PTSD was supported by its high sensitivity in identifying PTSD patients (93%) and specificity in discriminating them from substance-abusing control subjects (88.2%). Finally, convergent validity of the M-PTSD was substantiated by significant correlations of the instrument with measures of combat exposure and interview and psychometric measures of PTSD symptomatology. The M-PTSD was shown to be a highly reliable and valid measure of the spectrum of PTSD symptoms in Vietnam combat veterans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
57.
A spectrophotometric bioassay was used to screen selected food ingredients intended for development of functional foods designed to influence the growth of gut bacteria. Dose–response profiles displaying Δgrowth, the magnitude of deviation from growth of controls, were generated for probiotics Lactobacillus reuteri, Lactobacillus rhamnosus, Bifidobacterium lactis and pathogens Escherichia coli, Salmonella Typhimurium and Staphylococcus aureus. Ingredients were manuka honey UMF?20+(dose‐dependently increased probiotics and decreased pathogens); bee pollen (biphasic growth effects against all); Rosehips and BroccoSprouts® (increased all dose‐dependently); blackcurrant oil (little effect) and propolis (inhibited all strains). Ingredients were also bioassayed in pairs to assess desirable or undesirable synergistic interactions. Observed synergies included manuka honey (predominantly desirable); rosehips or BroccoSprouts® (desirable and undesirable); blackcurrant oil (desirable) and propolis (tended towards synergies reinforcing its antimicrobial effects), collectively revealing a complex web of interactions which varied by ingredient and bacterial strain. Manuka honey was particularly effective at influencing gut bacteria. The surprising frequency of undesirable synergistic interactions illustrates the importance of pre‐testing potential ingredient combinations intended for use in functional foods.  相似文献   
58.
S. C. Wright, A. Aron, T. McLaughlin-Volpe, and S. A. Ropp (1997) proposed that the benefits associated with cross-group friendship might also stem from vicarious experiences of friendship. Extended contact was proposed to reduce prejudice by reducing intergroup anxiety, by generating perceptions of positive ingroup and outgroup norms regarding the other group, and through inclusion of the outgroup in the self. This article documents the first test of Wright et al.'s model, which used structural equation modeling among two independent samples in the context of South Asian-White relations in the United Kingdom. Supporting the model, all four variables mediated the relationship between extended contact and outgroup attitude, controlling for the effect of direct contact. A number of alternative models were ruled out, indicating that the four mediators operate concurrently rather than predicting one another. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
59.
The output voltage waveforms expected when replaying with various head structures from media magnetized in arbitrary directions are predicted. Expressions are given in useful closed forms for the outputs in isolated and pulse crowded circumstances. Output waveforms are shown for a range of orientations of the recorded magnetization to reveal aspects of pulse symmetry and their effects on “roll-off” curves  相似文献   
60.
The aim of this study was to evaluate psychosocial quality of life after heart transplantation. We examined 29 patients (25 M and 4 F), average age was 43.5 y (18-62 y). The age at time of heart transplantation was 43 years (17-55 y). The time after heart transplantation was 3.3 year (0.3-9 y). Spielberger's Questionnaire of Anxiety, Knobloch's inventory of neuroticism, Freiburg's Personality Inventory and Quality of Life Inventory were used, 33% of patients demonstrated increasing frequency and 29% of patients increasing intensity of neurotic symptoms. 23% of patients presented increasing levels of anxiety (as a state). The personality dimensions (depression, excitability and low emotional stability) displayed high frequency. The results showed that patients were more satisfied with family support, with sexual activities, and less satisfied with financial situation, social activities, social isolations, sleep, memory, excitability, fatigue. 41.5% of patients returned back to work. The results indicate that these psychosocial factors play an important role in quality of life after heart transplantation. That is why if is necessary to dedicate an increasing attention to them. (Tab. 1, Fig. 6, Ref. 14.)  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