全文获取类型
收费全文 | 2671篇 |
免费 | 133篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 42篇 |
综合类 | 18篇 |
化学工业 | 712篇 |
金属工艺 | 61篇 |
机械仪表 | 52篇 |
建筑科学 | 94篇 |
矿业工程 | 11篇 |
能源动力 | 83篇 |
轻工业 | 330篇 |
水利工程 | 30篇 |
石油天然气 | 25篇 |
武器工业 | 2篇 |
无线电 | 236篇 |
一般工业技术 | 343篇 |
冶金工业 | 506篇 |
原子能技术 | 14篇 |
自动化技术 | 265篇 |
出版年
2023年 | 17篇 |
2022年 | 51篇 |
2021年 | 109篇 |
2020年 | 57篇 |
2019年 | 47篇 |
2018年 | 70篇 |
2017年 | 65篇 |
2016年 | 64篇 |
2015年 | 63篇 |
2014年 | 82篇 |
2013年 | 151篇 |
2012年 | 113篇 |
2011年 | 142篇 |
2010年 | 115篇 |
2009年 | 123篇 |
2008年 | 108篇 |
2007年 | 116篇 |
2006年 | 92篇 |
2005年 | 75篇 |
2004年 | 74篇 |
2003年 | 85篇 |
2002年 | 80篇 |
2001年 | 59篇 |
2000年 | 45篇 |
1999年 | 36篇 |
1998年 | 177篇 |
1997年 | 109篇 |
1996年 | 101篇 |
1995年 | 60篇 |
1994年 | 47篇 |
1993年 | 49篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 23篇 |
1971年 | 7篇 |
1943年 | 2篇 |
排序方式: 共有2824条查询结果,搜索用时 46 毫秒
81.
Methodology for the reliability evaluation of a passive system and its integration into a Probabilistic Safety Assessment 总被引:2,自引:0,他引:2
Michel Marqus J.F. Pignatel P. Saignes F. DAuria L. Burgazzi C. Müller R. Bolado-Lavin C. Kirchsteiger V. La Lumia I. Ivanov 《Nuclear Engineering and Design》2005,235(24):1864-2631
A methodology has been developed to evaluate the reliability of passive systems characterised by a moving fluid and whose operation is based on thermal–hydraulic (T-H) principles. The methodology includes:
- • identification and quantification of the sources of uncertainties and determination of the important variables;
- • propagation of the uncertainties through T-H models and assessment of T-H passive system unreliability;
- • introduction of passive system unreliability in the accident sequence analysis.
82.
83.
基于遗传算法的分布式异构数据库的查询优化 总被引:2,自引:1,他引:2
对于分布武异构数据库,查询优化问题是其核心问题。本文用基于位、值结构树型编码的遗传算法对分布武异构数据库进行查询优化,取得了很好的效果。 相似文献
84.
85.
Fatigue of bituminous mixtures 总被引:1,自引:0,他引:1
H. Di Benedetto C. de La Roche H. Baaj A. Pronk R. Lundström 《Materials and Structures》2004,37(3):202-216
This paper presents an interlaboratory test campaign organized by the RILEM 182-PEB Technical Committee. In the campaign,
11 different test methods, comprising uniaxial tension/compression, 2-, 3- and 4-point bending and indirecttension tests,
were utilized in order to investigate fatigue characteristics of a dense graded asphalt concrete mixture. The testing conditions
specified were sinusoidal excitation at 10Hz and 10°C using controlled strain and stress modes. In total, more than 150 fatigue
tests were carried out during the investigation. The fatigue test results were analyzed using both classical as well as continuum
damage mechanics approaches. The fatigue test results obtained using the classical fatigue approach are considerably influenced
by test type and mode of loading (controlled stress or strain) used. Consequently, this approach has limited use in realistic
fatigue characterization of bituminous materials and pavement structures. In contrast to the classical approach, models founded
on continuum damage theory may serve to isolate intrinsic fatigue characteristics from the influence of so-called biased effects,
which are largely caused by the accelerated laboratory testing. The continuum damage models investigated may constitute steps,
towards a rational mechanistic fatigue characterization model, which are important for effective future pavement design. 相似文献
86.
87.
This 6-year longitudinal study examined girls' peer-nominated social preference and aggression in childhood as predictors of self- and parent-reported externalizing symptoms, substance use (i.e.. cigarette, alcohol, and marijuana use), and sexual risk behavior in adolescence. Participants were 148 girls from diverse ethnic backgrounds, who were initially assessed in Grades 4-6 and again in Grades 10-12. Results supported a moderator model, indicating that social preference changed the nature of the association between childhood aggression and adolescent outcomes. When accompanied by peer rejection, aggressive behavior was moderately stable over time and significantly associated with adolescent girls' substance use and sexual risk behavior. However, under conditions of peer acceptance, no significant association between childhood aggression and adolescent outcomes emerged. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
89.
Liliana Martelo Alfonso Jiménez Artur JM Valente Hugh D Burrows Ana T Marques Michael Forster Ullrich Scherf Mercedes Peltzer Sofia M Fonseca 《Polymer International》2012,61(6):1023-1030
Films of neat and plasticized biodegradable poly(lactic acid) (PLA) matrices containing anionic conjugated polyelectrolytes, poly[9,9‐bis(4‐phenoxybutylsulfonate)]fluorene‐2,7‐diyl‐alt‐arylenes, with 1,4‐phenylene and 4,4″‐p‐terphenylene, respectively, as arylene groups or a neutral poly(9,9‐dialkylfluorene) for comparison were prepared by solution casting. These films were characterized using differential scanning calorimetry, thermogravimetry, scanning electron microscopy and fluorescence spectroscopy. In addition, the effects of plasticizer on the thermal properties and the oxygen permeability of the PLA films were measured through the oxygen transmission rate. Results show that it is possible to obtain thin, optically transparent and luminescent films with potential in oxygen sensing, exhibiting good thermal and photochemical stability. At high polyelectrolyte content, evidence is found for phase separation and aggregate formation and it is no longer possible to obtain completely homogeneous films. The possibility of incorporating the cationic metal complex tris(2,2′‐bipyridyl)ruthenium(II) into plasticized PLA films containing conjugated polyelectrolytes for dual‐wavelength ratiometric luminescence sensing is also discussed. Copyright © 2012 Society of Chemical Industry 相似文献
90.
Ioana Veronica Ciuchi Cristina Stefania Olariu Liliana Mitoseriu 《Materials Science and Engineering: B》2013,178(19):1296-1302
Measurements by impedance spectroscopy and Bruggeman effective medium approximation model were employed in order to determine the mineral volume fraction of dry bone. This approach assumes that two or more phases are present into the composite: the matrix (environment) and the other ones are inclusion phases. A fragment of femur diaphysis dense bone from a young pig was investigated in its dehydrated state. Measuring the dielectric properties of bone and its main components (hydroxyapatite and collagen) and using the Bruggeman approach, the mineral volume filling factor was determined. The computed volume fraction of the mineral volume fraction was confirmed by a histogram test analysis based on the SEM microstructures. In spite of its simplicity, the method provides a good approximation for the bone mineral volume fraction. The method which uses impedance spectroscopy and EMA modeling can be further developed by considering the conductive components of the bone tissue as a non-invasive in situ impedance technique for bone composition evaluation and monitoring. 相似文献