全文获取类型
收费全文 | 14442篇 |
免费 | 129篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 97篇 |
综合类 | 3篇 |
化学工业 | 1036篇 |
金属工艺 | 104篇 |
机械仪表 | 301篇 |
建筑科学 | 217篇 |
矿业工程 | 30篇 |
能源动力 | 130篇 |
轻工业 | 890篇 |
水利工程 | 107篇 |
石油天然气 | 15篇 |
无线电 | 866篇 |
一般工业技术 | 1030篇 |
冶金工业 | 8898篇 |
原子能技术 | 108篇 |
自动化技术 | 749篇 |
出版年
2021年 | 67篇 |
2020年 | 55篇 |
2019年 | 62篇 |
2018年 | 62篇 |
2017年 | 86篇 |
2016年 | 67篇 |
2015年 | 48篇 |
2014年 | 108篇 |
2013年 | 318篇 |
2012年 | 162篇 |
2011年 | 240篇 |
2010年 | 215篇 |
2009年 | 231篇 |
2008年 | 262篇 |
2007年 | 243篇 |
2006年 | 248篇 |
2005年 | 221篇 |
2004年 | 184篇 |
2003年 | 210篇 |
2002年 | 201篇 |
2001年 | 162篇 |
2000年 | 162篇 |
1999年 | 381篇 |
1998年 | 2657篇 |
1997年 | 1567篇 |
1996年 | 1116篇 |
1995年 | 667篇 |
1994年 | 526篇 |
1993年 | 607篇 |
1992年 | 154篇 |
1991年 | 169篇 |
1990年 | 190篇 |
1989年 | 178篇 |
1988年 | 171篇 |
1987年 | 174篇 |
1986年 | 141篇 |
1985年 | 171篇 |
1984年 | 95篇 |
1983年 | 108篇 |
1982年 | 88篇 |
1981年 | 125篇 |
1980年 | 122篇 |
1979年 | 81篇 |
1978年 | 84篇 |
1977年 | 238篇 |
1976年 | 489篇 |
1975年 | 85篇 |
1974年 | 72篇 |
1973年 | 65篇 |
1972年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
72.
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
73.
74.
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
75.
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
76.
Johnson J 《Environmental science & technology》1996,30(11):481A-482A
Society. 相似文献
77.
RA Newman JC Vidal LJ Viskatis J Johnson MA Etcheverry 《Canadian Metallurgical Quarterly》1993,11(2-3):151-159
Two purified animal venom toxins, crotoxin and cardiotoxin, have been combined to produce a unique natural product (VRCTC-310) currently under investigation as an antitumor agent by the National Cancer Institute. In vitro, it has demonstrated cytotoxic disease specificity and a unique mechanism of action when submitted to COMPARE analysis. In vivo, tolerance was developed to the neurotoxic properties of crotoxin which allowed comparison of several schedules of fixed and escalating daily i.m. doses to mice bearing s.c. Lewis Lung carcinoma. An 83% inhibition of tumor growth was achieved using an escalating dose schedule starting at 1.8 mg/kg and reaching 6.3 mg/kg/day on day 20. Although some irritation around the sites of i.m. injection was noted, animal weight loss was negligible and there were no other signs of adverse toxicity. This natural product represents a new, membrane interactive anticancer agent which produces a unique spectrum of cytotoxicity in vitro and which has demonstrated interesting in vivo antitumor efficacy. 相似文献
78.
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
79.
We compared the data from four growth hormone (GH) immunoassays for analyzing 24-h GH profiles in four apparently normal subjects and four obese subjects (508 serum samples). The detection limit was 0.02 microgram/L for one immunochemiluminometric assay (ICMA), 0.1 microgram/L for two IRMAs, and 0.4 microgram/L for one RIA. All GH pulses with a peak ICMA value > 1 microgram/L were detected by each of the other methods. Overall, the correlation coefficient between the values obtained with all four assays exceeded 0.90. However, for GH concentrations < or = 0.25 microgram/L, acceptable concordance (r2 > or = 0.80) was reached only between the ICMA and one IRMA; between the ICMA and the RIA, concordance was acceptable only for GH concentrations > or = 10 micrograms/L. In the normal subjects, the percentage of undetectable values was 0% with the ICMA but 29% with one of the IRMAs; in obese subjects, the corresponding values were 12% and 38%. 相似文献
80.