全文获取类型
收费全文 | 19854篇 |
免费 | 716篇 |
国内免费 | 54篇 |
专业分类
电工技术 | 257篇 |
综合类 | 25篇 |
化学工业 | 3968篇 |
金属工艺 | 479篇 |
机械仪表 | 413篇 |
建筑科学 | 973篇 |
矿业工程 | 108篇 |
能源动力 | 645篇 |
轻工业 | 1701篇 |
水利工程 | 178篇 |
石油天然气 | 79篇 |
无线电 | 1577篇 |
一般工业技术 | 3524篇 |
冶金工业 | 3501篇 |
原子能技术 | 119篇 |
自动化技术 | 3077篇 |
出版年
2023年 | 144篇 |
2022年 | 260篇 |
2021年 | 382篇 |
2020年 | 275篇 |
2019年 | 314篇 |
2018年 | 430篇 |
2017年 | 416篇 |
2016年 | 458篇 |
2015年 | 374篇 |
2014年 | 554篇 |
2013年 | 1277篇 |
2012年 | 863篇 |
2011年 | 1199篇 |
2010年 | 831篇 |
2009年 | 854篇 |
2008年 | 962篇 |
2007年 | 891篇 |
2006年 | 775篇 |
2005年 | 758篇 |
2004年 | 606篇 |
2003年 | 560篇 |
2002年 | 539篇 |
2001年 | 342篇 |
2000年 | 313篇 |
1999年 | 340篇 |
1998年 | 384篇 |
1997年 | 307篇 |
1996年 | 348篇 |
1995年 | 318篇 |
1994年 | 300篇 |
1993年 | 275篇 |
1992年 | 261篇 |
1991年 | 165篇 |
1990年 | 231篇 |
1989年 | 204篇 |
1988年 | 171篇 |
1987年 | 170篇 |
1986年 | 160篇 |
1985年 | 189篇 |
1984年 | 203篇 |
1983年 | 165篇 |
1982年 | 172篇 |
1981年 | 169篇 |
1980年 | 145篇 |
1979年 | 169篇 |
1978年 | 124篇 |
1977年 | 122篇 |
1976年 | 163篇 |
1975年 | 125篇 |
1973年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Florsheim Paul; Behling Steven; South Mikle; Fowles Timothy R.; DeWitt John 《Canadian Metallurgical Quarterly》2004,1(2):126
This study adopted a systemic approach to studying intervention efforts with delinquent youth, examining the association between several youth corrections programs and adult criminal outcomes. Two studies were designed to use juvenile and adult court records to evaluate the effectiveness of treatment programs provided to delinquent youth in state custody. The results of Study 1 suggested that court-recorded delinquent charges can be used to estimate delinquency severity. The results of Study 2 presented a discouraging but not entirely unexpected illustration of the effectiveness of intervention efforts among delinquent youth. It was found that time spent in juvenile detention facilities, work programs, and group homes was associated with negative adult criminal outcomes. No links between time spent in youth corrections programs and positive outcomes were identified. Implications for future program evaluation efforts are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
Mai Lu Paul J. Leonard Duo-Wang Fan Fu-Yong Xu 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(10):1469-1479
In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits. 相似文献
83.
Paul N.Brauss 《印刷技术》2006,(29)
在谈到商品包装装潢市场的发展趋势时,有必要先分析一下整个供应链.从根本上讲,推动整个供应链发展的是消费者.CPG(综合性消费品)公司将会影响消费者的选择,而消费者的这些选择对整个供应链会产生很大的波动性影响,使供应链的各个环节都发生动态变化.另外,由于技术、需求、生产力和交货期等因素的影响,也会使整个供应链发生一些折衷性的变化. 相似文献
84.
Nano-crystal embedded PbO-P2O5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within
the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region.
The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment
of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature.
A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic
elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic
velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination
of the size of nano-crystals from the ultrasonic attenuation data. 相似文献
85.
HA Mook DM Paul BC Sales LA Boatner L Cussen 《Canadian Metallurgical Quarterly》1988,38(16):12008-12010
86.
Gellatly Angus; Pilling Michael; Cole Geoff; Skarratt Paul 《Canadian Metallurgical Quarterly》2006,32(6):1422
Object substitution masking (OSM) is said to occur when a perceptual object is hypothesized that is mismatched by subsequent sensory evidence, leading to a new hypothesized object being substituted for the first. For example, when a brief target is accompanied by a longer lasting display of nonoverlapping mask elements, reporting of target features may be impaired. J. T. Enns and V. Di Lollo (2000) considered it an outstanding question whether OSM masks some or all aspects of a target. The authors report three experiments demonstrating that OSM can selectively affect target features. Participants may be able to detect a target while being unable to report other aspects of it or to report the color but not the orientation of a target (or vice versa). We discuss these findings in relation to two other visual phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
A possible structure of the casein micelle based on high-resolution field-emission scanning electron microscopy 总被引:2,自引:0,他引:2
Douglas G. Dalgleish Paul A. Spagnuolo H. Douglas Goff 《International Dairy Journal》2004,14(12):1025-1031
New electron micrographs, produced using the technique of Field Emission Scanning Electron Microscopy, showing the details of the micellar surface, are presented. The images show the micellar surfaces without any coating, and suggest that the surface of the micelle may have a much more complex structure than has previously been demonstrated. Although there appear to be no spherical subunits (submicelles), there is evidence for the organization of the caseins into tubular structures within the micelle. The surface is not smooth, and contains gaps between the substructures. The observations are discussed in terms of published models of micellar structure, where is it suggested how the depiction of the micellar surface can be used to explain certain factors of its reactivity and behaviour. 相似文献
88.
Verhaeghen Paul; Cerella John; Basak Chandramallika 《Canadian Metallurgical Quarterly》2004,30(6):1322
Five individuals participated in an extensive practice study (10 1-hr sessions, 11,000 trials total) on a self-paced identity-judgment n-back task (n ranging from 1 to 5). Within Session 1, response time increased abruptly by about 300 ms in passing from n = 1 to n > 1, suggesting that the focus of attention can accommodate only a single item (H. Caravan, 1998; B. McElree, 2001). Within Session 10, response time was dramatically reduced and increased linearly with n for n ≤ 4, with a slope of about 30 ms. The data suggest that working memory consists of a focus of attention governed by a limited-capacity search, expandable through practice, and a content-addressable region outside the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
Paul F.Smith Sameer M.Prabhu Jonathan H.Friedman 《电子设计应用》2008,(5):88-92
本文引入了基于模型设计的概念,突出了其中的一些优点,详细讨论了组织中采用基于模型设计文化的10个最佳策略。这些最佳策略从不同工业领域的公司中收集,包括向基于模型设计的成功或者不成功的过渡。 相似文献
90.
The judged likelihood of a focal outcome should generally decrease as the list of alternative possibilities increases. For example, the likelihood that a runner will win a race goes down when 2 new entries are added to the field. However, 6 experiments demonstrate that the presence of implausible alternatives (duds) often increases the judged likelihood of a focal outcome. This dud-alternative effect was detected for judgments involving uncertainty about trivia facts and stochastic events. Nonnumeric likelihood measures and betting measures reliably detected the effect, but numeric likelihood measures did not. Time pressure increased the magnitude of the effect. The results were consistent with a contrast-effect account: The inclusion of duds increases the perceived strength of the evidence for the focal outcome, thereby affecting its judged likelihood. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献