全文获取类型
收费全文 | 9095篇 |
免费 | 73篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 54篇 |
综合类 | 2篇 |
化学工业 | 520篇 |
金属工艺 | 40篇 |
机械仪表 | 60篇 |
建筑科学 | 103篇 |
矿业工程 | 4篇 |
能源动力 | 49篇 |
轻工业 | 326篇 |
水利工程 | 19篇 |
石油天然气 | 12篇 |
无线电 | 411篇 |
一般工业技术 | 579篇 |
冶金工业 | 6724篇 |
原子能技术 | 20篇 |
自动化技术 | 247篇 |
出版年
2021年 | 36篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 40篇 |
2016年 | 29篇 |
2015年 | 30篇 |
2014年 | 46篇 |
2013年 | 147篇 |
2012年 | 77篇 |
2011年 | 117篇 |
2010年 | 84篇 |
2009年 | 74篇 |
2008年 | 91篇 |
2007年 | 103篇 |
2006年 | 99篇 |
2005年 | 90篇 |
2004年 | 88篇 |
2003年 | 99篇 |
2002年 | 83篇 |
2001年 | 77篇 |
2000年 | 90篇 |
1999年 | 254篇 |
1998年 | 2148篇 |
1997年 | 1255篇 |
1996年 | 832篇 |
1995年 | 464篇 |
1994年 | 349篇 |
1993年 | 453篇 |
1992年 | 87篇 |
1991年 | 79篇 |
1990年 | 102篇 |
1989年 | 107篇 |
1988年 | 100篇 |
1987年 | 82篇 |
1986年 | 78篇 |
1985年 | 91篇 |
1984年 | 30篇 |
1983年 | 45篇 |
1982年 | 55篇 |
1981年 | 80篇 |
1980年 | 85篇 |
1979年 | 32篇 |
1978年 | 40篇 |
1977年 | 190篇 |
1976年 | 356篇 |
1975年 | 39篇 |
1974年 | 21篇 |
1973年 | 19篇 |
1972年 | 19篇 |
排序方式: 共有9170条查询结果,搜索用时 15 毫秒
51.
Pertussis in Massachusetts, 1981-1991: incidence, serologic diagnosis, and vaccine effectiveness 总被引:1,自引:0,他引:1
CD Marchant AM Loughlin SM Lett CW Todd LH Wetterlow R Bicchieri S Higham P Etkind E Silva GR Siber 《Canadian Metallurgical Quarterly》1994,169(6):1297-1305
Massachusetts provides diphtheria-tetanus toxoid-pertussis (DTP) vaccine, and since 1980 has monitored pertussis with a statewide diagnostic service. The incidence of bacteriologically confirmed pertussis was 104.5 per 100,000 person-years in 1-month-old infants and declined progressively thereafter. Infants < 6 months old experienced disproportionate morbidity: 44% of bacteriologically confirmed pertussis, 64% of hospitalizations, and 71% of hospital days. Most children with pertussis had received < 3 DTP doses during childhood, whereas 87% of adolescents with pertussis had received > or = 4 doses. Serodiagnosis by single serum anti-pertussis toxin antibody ELISA increased the incidence of confirmed pertussis in persons 11-19 years old from 3.0 to 12.9 per 100,000 and in persons > or = 20 years old from 0.16 to 0.56 per 100,000. Bacteriologic methods underestimate pertussis incidence, but a single serum anti-pertussis toxin antibody ELISA is a practical method for population-based diagnosis in adolescents and adults. 相似文献
52.
53.
JH Winstanley SJ Leinster TG Cooke BR Westley AM Platt-Higgins PS Rudland 《Canadian Metallurgical Quarterly》1993,67(4):767-772
The expression of the protease cathepsin-D has been evaluated using an immunohistochemical technique with a polyclonal antibody in paraffin-embedded tissue from 359 patients treated between the years 1975-1981 for Stage I and II breast cancer. One hundred and twenty seven patients (35%) have strongly positive, granular staining, 138 (38%) are intermediately stained in the cytoplasm, and in 94 (26%) no staining is observed. There is a strong positive association between expression of cathepsin-D and the presence of tumour in axillary lymph nodes (P < 0.006). Expression of the protease is associated with significantly poorer survival of patients in univariate analysis (P = 0.025); however, this is not independent of other tumour variables. 相似文献
54.
AM Sherman 《Canadian Metallurgical Quarterly》1993,12(6):27-30
Urinary incontinence is most frequently associated with the elderly, particularly women, and is often thought of as inevitable. However, orthopaedic nurses encounter incontinence as a response to alterations in orthopaedic health. This article reviews the types of urinary incontinence, with emphasis on those which may most directly result from orthopaedic problems. It will also help the nurse differentiate between types of incontinence in a way that will clarify appropriate interventions. 相似文献
55.
OBJECTIVE: Although there have been many studies of the outcome of anorexia nervosa, methodological weaknesses limit their interpretation. The authors used a case-control design to try to improve knowledge about the outcome of anorexia nervosa. METHOD: All new female patients referred to an eating disorders service between Jan. 1, 1981, and Dec. 31, 1984, who had probable or definite anorexia nervosa were eligible for inclusion. Of these women, 86.4% (N = 70) were located and agreed to participate. The comparison group (N = 98) was a random community sample. All subjects were interviewed with a structured diagnostic instrument. RESULTS: A minority of the patients (10%) continued to meet the criteria for anorexia nervosa a mean of 12 years after initial referral. Even among those who no longer met these criteria, relatively low body weight and cognitive features characteristic of anorexia nervosa (perfectionism and cognitive restraint) persisted. The rates of lifetime comorbid major depression, alcohol dependence, and a number of anxiety disorders were very high. CONCLUSIONS: In the managed care/brief treatment era, therapeutic approaches with an excessive focus on weight gain that neglect the detection and treatment of associated psychological features and comorbidity may be inappropriate. Anorexia nervosa is a serious psychiatric disorder with substantial morbidity. 相似文献
56.
M Elena M Pérez M Jansà R Déulofeu E Esmatjes N Schinca E Mas R Molina AM Ballesta 《Canadian Metallurgical Quarterly》1998,110(10):365-369
BACKGROUND: In order to elaborate recommendations for the dietetic care of diabetic patients and other clinical disorders we have measured the concentration of carbohydrates and trace elements in a group of non alcoholic refreshments of current use in Spain. MATERIAL AND METHODS: Thirty refreshments were classified into 10 groups. Glucose and phosphate were measured by hexokinase and reduction of phospho-molybdate methods respectively in an autoanalyzer Dax-72. Glucose and fructose were analyzed by cellulose thin-layer chromatography; glucose, fructose and sucrose by gas chromatographys. Sodium and potassium by emission spectrophotometry and calcium, magnesium, iron, copper and zinc by atomic absorption spectrophotometry. RESULTS: Light refreshments and soft drinks have no carbohydrates. Isotonic beverages, fruit juices, cool tea and non alcoholic beers had less than 10 g/dl. Tonic waters, Fanta, different coles, non alcoholic bitter and others had more than 10 g/dl. Sodium levels between 15-20 mEq/l were found in the isotonic beverages and 7-Up and levels of 7 mEq/l in the others. Potassium values between 15-40 mEq/l were found in the fruit juices, 3-4 mEq/l in Gatorade and less than 1 mEq/l in the others. CONCLUSIONS: Light refreshments and soft drinks contain low concentrations of carbohydrates and sodium. Fruit juices have high potassium concentration. Such information can be especially useful for dietetic care of diabetic patients. 相似文献
57.
TJ Meyer SE Eveloff MS Bauer WA Schwartz NS Hill RP Millman 《Canadian Metallurgical Quarterly》1994,105(4):1211-1216
Sleep deprivation and fragmentation occurring in the hospital setting may have a negative impact on the respiratory system by decreasing respiratory muscle function and ventilatory response to CO2. Sleep deprivation in a patient with respiratory failure may, therefore, impair recovery and weaning from mechanical ventilation. We postulate that light, sound, and interruption levels in a weaning unit are major factors resulting in sleep disorders and possibly circadian rhythm disruption. As an initial test of this hypothesis, we sampled interruption levels and continuously monitored light and sound levels for a minimum of seven consecutive days in a medical ICU, a multiple bed respiratory care unit (RCU) room, a single-bed RCU room, and a private room. Light levels in all areas maintained a day-night rhythm, with peak levels dependent on window orientation and shading. Peak sound levels were extremely high in all areas representing values significantly higher than those recommended by the Environmental Protection Agency as acceptable for a hospital environment. The number of sound peaks greater than 80 decibels, which may result in sleep arousals, was especially high in the intensive and respiratory care areas, but did show a day-night rhythm in all settings. Patient interruptions tended to be erratic, leaving little time for condensed sleep. We conclude that the potential for environmentally induced sleep disruption is high in all areas, but especially high in the intensive and respiratory care areas where the negative consequences may be the most severe. 相似文献
58.
59.
The rostral migratory stream consists of a large number of cells migrating from the lateral ventricles to the rostral telencephalon, primarily the olfactory bulb. The pathway continually provides neuro- and glioblasts throughout life. The present paper indicates that a considerable number of cells undergo apoptotic cell death en route, even in young (day 3) rats when presumably many vacant sites are still available in the developing brain. 相似文献
60.
电力市场化是全球电力工业都在热烈讨论和积极探索的热点课题 ,在中国电力市场化改革的今天 ,尤其具有重要的理论和实践意义。 2 0 0 2年 5月 1 3日至 1 8日 ,由清华港大深圳电力系统研究所主办的“电力市场新进展高级研讨会”在深圳清华大学研究院举行。在研讨会上 ,与会专家分别就电力市场研究和实践中的若干问题发表了演讲。本刊将主要内容摘录、汇编成文 ,奉献给大家 ,以便广大读者对电力市场的研究动态有比较全面的了解。在此 ,衷心感谢参加“电力市场新进展研讨会”的各位专家给予的大力支持和帮助 ,特别感谢香港大学 /浙江大学文福拴博士、香港大学严正博士在本文的摘编过程中提供的技术指导和具体帮助。 相似文献