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   69篇
  免费   2篇
化学工业   3篇
金属工艺   2篇
机械仪表   1篇
建筑科学   3篇
能源动力   9篇
轻工业   4篇
水利工程   1篇
无线电   6篇
一般工业技术   6篇
冶金工业   30篇
原子能技术   2篇
自动化技术   4篇
  2021年   1篇
  2020年   1篇
  2017年   2篇
  2015年   1篇
  2013年   2篇
  2012年   1篇
  2011年   3篇
  2009年   1篇
  2008年   1篇
  2006年   1篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   4篇
  1994年   1篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
  1946年   1篇
排序方式: 共有71条查询结果,搜索用时 390 毫秒
1.
OBJECTIVE: The incidence of back pain in children in our country is unknown. Several causes can produce this symptom, but it is necessary to rule out pathologies that require specific treatments. The goal of this work was to study the incidence and the etiology of back pain in children in our country. PATIENTS AND METHODS: We present a prospective study done in our Orthopedic Department during a period of 7 months. Twenty-two patients were referred with back pain of at least two months duration. The incidence was 2.9% compared to the total number of patients. The average age ranged from 7 to 17 years. RESULTS: A careful history and a radiological examination diagnosed 50% (11 cases) of the causes of backache in the present study. An idiopathic etiology was the most frequent cause and represented 9 patients (41%). In the remaining 12 cases (59%) pathological causes that required special treatment were identified including 2 cases of Scheuermann disease, 4 cases of painful scoliosis, 3 spondylolysis with spondylolisthesis, 2 cases of discitis, 1 benign neoplasm and 1 psychogenic cause. CONCLUSIONS: We recommend conservative management with the use of medication for relief of pain and physical therapy in the idiopathic cases. In the remaining cases, the specific treatment of the disease can improve the back pain.  相似文献   
2.
In an infertility treatment programme for spinal-cord injured men, vibrator application was primarily used in cases of upper motor neurone lesion and electroejaculation in men with lower lesions, or when vibrator application failed to induce ejaculation. Spermatozoa were obtained by these methods from 29 out of 35 men who desired infertility treatment. No ejaculate was obtained from six men. Three of these men plus two others with very poor sperm quality with electroejaculation underwent micro-surgical sperm aspiration from the vas deferens for invitro fertilization (IVF), and spermatozoa were obtained from all of them. Thus it was possible to obtain spermatozoa from almost every spinal-cord injured man who had ongoing spermatogenesis using these three methods. Insemination was the primary infertility treatment used with all the couples where there was successful ejaculation. In all, 12 pregnancies resulted from home vaginal inseminations, eight from intrauterine inseminations, two from IVF with ejaculated spermatozoa, and two from IVF with spermatozoa aspirated from the vas. Three couples had children from donor inseminations (not counted in the results); 12 are still in the programme. From 24 pregnancies, 22 children have now been born to 18 couples out of the original 35 (51%), and there were four abortions. Hence, overall, infertility treatment of spinal-cord injured men has given good results.  相似文献   
3.
A bacterium identified as Arthrobacter sp. was grown on dibenzothiophene (DBT) sulfone as a sole source of sulfur, producing sulfite and sulfate. Sulfur in DBT sulfone (1.0 mM) was nearly quantitatively converted to sulfate by the organism. The organism could also use DBT sulfone as a sole source of carbon and energy. There was evidence for transient accumulation of benzoic acid in the culture medium after growth of the cells slowed. The DBT sulfoxide analogue 9-fluorenone was converted by resting cells to a product identified as 1,10-dihydroxy-1,10-dihydrofluoren-9-one, suggesting that DBT sulfone may be metabolized via an angular hydroxylation resulting in carbon- sulfur bond cleavage. This strain of Arthrobacter showed no ability to desulfurize oxidized Illinois No. 6 coal.  相似文献   
4.
Musculoskeletal disorders are more common among women than among men. When comparing the difference between men and women in the prevalence of musculoskeletal disorders, methodological problems arise as men and women seldom perform the same type of activities, neither at work nor at home.

The main objective of this cross-sectional case study was to compare work technique and self-reported musculoskeletal symptoms between men and women performing the same type of work tasks within a metal industry. Other factors, such as leisure activities, were also taken into consideration. Three data collection methods were used; questionnaire, interviews and systematic observations. The results from the observations revealed that women worked more frequently and during longer times with their hands above shoulder height than men. Working with hands above shoulder height is considered a risk factor for neck and shoulder disorders according to previous studies. Workplace design factors were probably a reason for differences in working technique between men and women. A higher proportion of women than men reported shoulder symptoms. Women spent more time on household activities than men, which indicates a higher total workload in paid and unpaid work.  相似文献   

5.
Self-reported joint pain, a typical manifestation of osteoarthritis, was examined using 335 twin pairs from the Swedish Adoption/Twin Study of Aging to estimate relative genetic and environmental influences on self-reported joint pain and to examine the relationship between joint pain, health behavior, and psychological variables. Findings suggest that family resemblance for self-reported joint pain represents similar environments more than genetic similarity. Data from the early 1970s, including exercise, physical activity at work, obesity, and neuroticism, were used to predict joint pain in 1993. For men, moderate amounts of exercise decreased the likelihood of joint pain, but strenuous amounts of physical activity in the workplace had the opposite effect. For women, exercise and physical activity were not significant predictors, but past obesity and higher levels of neuroticism increased the likelihood of reporting joint pain in 1993. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
Editorial     
  相似文献   
7.
8.
9.
New methodologies based on supercritical fluid extraction (SFE) have been developed for the determination of fat-soluble vitamins in processed foods. The results obtained so far indicate that SFE is well suited to extraction of fat-soluble vitamins from food products, although validation work is required to establish accuracy and precision. The vitamins investigated were A, E and β-carotene, and the processed foods were UHT milk, milk powder, minced meat, liver paste, infant formula, canned baby food and margarine. Extraction equipment employed analyte collection on either a solid-phase trap or in a solvent. After extraction, the samples were saponified and the vitamins determined using reversed-phase liquid chromatography with ultraviolet or fluorescence detection. Sample throughput was at least 12 samples day -1 , i.e. at least twice the number achievable with a conventional extraction methodology. The detection limits for the vitamins in different processed foods were well below 0.1 µg g -1 . Recoveries (in comparison with vitamin levels obtained using conventional solvent extraction) were close to 100% for experienced personal with access to modern automatic equipment. To reach this level, it was necessary to protect the vitamins with an antioxidant during the different steps of the analysis procedure, to add methanol or ethanol to the extraction cell to facilitate the analyte extraction from the food matrix, and when using a solid-phase trap, to employ a fractionated extraction-elution procedure to prevent breakthrough losses. The developed methods were tested in a validation exercise between five laboratories, which had taken part in the method development, and in an intercomparison between 10 laboratories including laboratories with less experience of vitamin determination. The within-laboratory RSD was generally ≤11%. The average of the between-laboratory relative standard deviation (RSD) was about 23% in the validation, and increased to about 40% in the intercomparison. Ruggedness tests performed at different steps of the project showed that different types and models of equipment did not give large differences in recoveries. Thus, the increasing RSD can largely be ascribed to differences in experience in vitamin analysis of the participants.  相似文献   
10.
A series of methine bridge substituted porphyrin dye films have been fabricated both by vacuum sublimation and by the evaporation of a solution of the dye in methanol. The saturation surface photovoltage of these films at 4 × 10?7 Torr has been characterized by measuring the optical modulation of the transmission of incident electrons, and all of the films exhibit surface depletion layers with characteristic photovoltaic relaxation times on the order of 10 ms. There are appreciable differences, however, in the observed photovoltage resulting from the different methods of fabrication and the corresponding differences in crystallinity. In fact, this dependence on the structure appears to outweigh the much smaller dependence on the chemical nature of the methine bridge substituent. The sublimed films give evidence of additional electron levels in the bandgap which can be experimentally removed by annealing the films. The spectral dependence of the photovoltage does not indicate the presence of such levels in the spectral region examined.  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