全文获取类型
收费全文 | 3402篇 |
免费 | 37篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 43篇 |
综合类 | 28篇 |
化学工业 | 94篇 |
金属工艺 | 7篇 |
机械仪表 | 106篇 |
建筑科学 | 24篇 |
矿业工程 | 6篇 |
能源动力 | 6篇 |
轻工业 | 464篇 |
水利工程 | 3篇 |
石油天然气 | 17篇 |
无线电 | 26篇 |
一般工业技术 | 114篇 |
冶金工业 | 2382篇 |
原子能技术 | 3篇 |
自动化技术 | 130篇 |
出版年
2022年 | 19篇 |
2020年 | 22篇 |
2019年 | 38篇 |
2018年 | 11篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 160篇 |
2012年 | 39篇 |
2011年 | 30篇 |
2010年 | 36篇 |
2009年 | 32篇 |
2008年 | 41篇 |
2007年 | 43篇 |
2006年 | 34篇 |
2005年 | 32篇 |
2004年 | 29篇 |
2003年 | 27篇 |
2002年 | 23篇 |
2001年 | 11篇 |
2000年 | 17篇 |
1999年 | 92篇 |
1998年 | 766篇 |
1997年 | 442篇 |
1996年 | 297篇 |
1995年 | 162篇 |
1994年 | 131篇 |
1993年 | 154篇 |
1992年 | 30篇 |
1991年 | 38篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 42篇 |
1987年 | 58篇 |
1986年 | 43篇 |
1985年 | 44篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 15篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 66篇 |
1976年 | 129篇 |
1975年 | 9篇 |
1973年 | 10篇 |
1971年 | 8篇 |
1969年 | 6篇 |
1955年 | 18篇 |
1954年 | 16篇 |
排序方式: 共有3453条查询结果,搜索用时 15 毫秒
81.
Ultrahigh molecular weight polyethylene (UHMWPE) powder (60 micron diameter) and chopped fiber (6.5 mm length) were surface treated with a blend of reactive gases (fluorine and oxygen.) These powders and fibers were then compounded into a thermoset polyurethane matrix. Surface-treated and control reinforcements are compared at a 10 vol.% loading level. Tensile testing indicates improved stress transfer with surface treatment. Stress transfer is also improved with fibers versus powders. Fracture toughness is characterized by measuring the essential work of fracture, we. Surface-treated fiber composites exhibit work of fracture values almost three times the unfilled polyurethane values. Abrasion resistance was also measured. Surface treatment was found to significantly lower wear rates of powder composites. Fiber composites had lower wear rates than powder composites, although surface treatment had little effect. An approximate inverse relationship was found between wear rate and essential work of fracture. 相似文献
82.
D. M. dos Anjos K. B. Kokoh J.M. Léger A.R. DE Andrade P. Olivi G. Tremiliosi-Filho 《Journal of Applied Electrochemistry》2006,36(12):1391-1397
Pt–Mo alloy electrocatalysts were prepared by an arc-melting furnace process to investigate the origin of their enhanced activity toward ethanol oxidation. Two Mo contents were chosen in zones of the binary phase diagram where they are supposed to form either a pure alloy mixture or a solid solution. Pt–Mo alloy catalysts were more active than Pt-alone. Gradual Mo dissolution at the electrode surface was observed after voltammetric and chronoamperometric measurements. The dissolved Mo contributed to the catalytic effect of the electrode as underpotentially deposited (upd) adatoms. This dissolution probably also leads to an increase in the electrode surface roughness. Low molybdenum content in the electrode material enhances the activity toward ethanol oxidation when compared to Pt-alone. Ethanol oxidation was also investigated by in situ infrared reflectance spectroscopy in order to determine the presence of adsorbed intermediates like CO species. Acetaldehyde, acetic acid and CO2 were also found by spectroscopic experiments. 相似文献
83.
AISI 304奥氏体不锈钢表面经激光熔化处理,引入一个大的张应力,它可用注Ne的方法使其缓解本文介绍测量0.1μm薄层应力变化的原理和技术,由测得的应力分布曲线证明了注Ne缓解表面张应力的效果 相似文献
84.
85.
DE Gibbons 《Canadian Metallurgical Quarterly》1998,60(11):669-671
The former purchaser-provider split underwent an important change during the last years in UK. Especially since the new government came into office in 1997 the approach to equity and equality in dental health care has been characterised by two decisions. Firstly, the level of commissioning services was shifted from the centre to so-called natural communities of about 100,000 people. Secondly, the groups responsible for planning and providing care are constituted from local medical practitioners, community nurses and social services representatives, in line with the Regional Health Authority and the national framework "Our Healthier Nation". The new community dental service is expected to be in a better position to improve the situation in areas of social exclusion. 相似文献
86.
M Delgado EJ Munoz-Elias Y Kan I Gozes M Fridkin DE Brenneman RP Gomariz D Ganea 《Canadian Metallurgical Quarterly》1998,273(47):31427-31436
87.
JD Reveille GS Alarcón SE Fowler SR Pillemer R Neuner DO Clegg IS Mikhail DE Trentham JC Leisen G Bluhm SM Cooper H Duncan M Tuttleman SP Heyse JT Sharp B Tilley 《Canadian Metallurgical Quarterly》1996,39(11):1802-1807
OBJECTIVE: To examine the effect of alleles encoding the "shared"/"rheumatoid" epitope on rheumatoid arthritis (RA) disease severity in patients who participated in the minocycline in RA (MIRA) trial. METHODS: Of 205 patients with a week-48 visit, blood was available for typing of HLA-DRB1 and HLA-DQB1 in 174 (85%) and successfully completed in 169 (82%). Baseline erosions were used to assess disease severity and new erosions at the last visit served as a proxy for progression. RESULTS: At baseline, there was no association between the presence of erosive disease or rheumatoid factor status and the dose of rheumatoid epitope (homozygous, heterozygous, none) or the specific alleles identified. At the final visit, a gradient was observed for the 3 allelic subgroups (and their gene doses) in the occurrence of new erosions among the Caucasian placebo-treated, but not the minocycline-treated, patients. A treatment group/HLA-DR4 epitope interaction was demonstrated in multivariate analyses. Approximately two-thirds of African-American patients did not have the rheumatoid epitope. CONCLUSION: HLA-DRB1 oligotyping may be useful in predicting the progression of disease in some Caucasian patients. Our study corroborates the infrequency of the epitope among African-American patients with RA. 相似文献
88.
Clients are leaving the hospital "quicker and sicker," and they frequently have acute care needs that must be met by resources outside the hospital setting. Community resources are diverse, vary widely from place to place, and have no central administration. Thus, using them can be challenging for both the nurse, client, and family. Reimbursement mechanisms underlie a person's ability to use resources and receive health care. By presenting two actual case scenarios where clients have mobility problems commonly seen by orthopaedic nurses, the authors discuss the community resources available, avenues of access to them, and their reimbursement mechanisms. 相似文献
89.
90.
FIGOLI A HOINKIS J CRISCUOLI A FRANZ C DE RYCKE M BLOCK C DEOWAN S A ISLAM R DRIOLI E 《哈尔滨工业大学学报(英文版)》2012,19(1):63-66
Arsenic is a natural tasteless and odourless element,existing in the earth’s crust at average levels of between two and five thousands micrograms per liter (parts per million) . Arsenic is highly toxic to humans, who are exposed to it primarily from air,food and water. The occurrence of arsenic in groundwater is due to geological composition of soil. High concentrations of arsenic in water are the result of dissolution or desorption of ferric oxides and the oxidation of mineral arsenopyrites. Arsenic in drinking water has an important impact on the human health,especially in the less developed countries. Different methods exist to remove arsenic from aquatic media,and one of them is by adsorption. In this work,the adsorption of both As(III) and As(V) by means of novel microspheres has been investigated. In particular,TiO2 has been embedded into polymeric microspheres PES (PolyEtherSulphone) and PEEK-WC (PolyEtherEther-Ketone) . The main advantages of this encapsulation adsorption material are: no loss of adsorbents into the water stream,easy to be used and scaled-up. 相似文献