全文获取类型
收费全文 | 1000篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 177篇 |
金属工艺 | 13篇 |
机械仪表 | 21篇 |
建筑科学 | 54篇 |
矿业工程 | 22篇 |
能源动力 | 34篇 |
轻工业 | 108篇 |
水利工程 | 19篇 |
石油天然气 | 2篇 |
无线电 | 85篇 |
一般工业技术 | 123篇 |
冶金工业 | 97篇 |
原子能技术 | 2篇 |
自动化技术 | 252篇 |
出版年
2023年 | 11篇 |
2022年 | 21篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 16篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 57篇 |
2012年 | 47篇 |
2011年 | 85篇 |
2010年 | 55篇 |
2009年 | 84篇 |
2008年 | 57篇 |
2007年 | 57篇 |
2006年 | 50篇 |
2005年 | 59篇 |
2004年 | 37篇 |
2003年 | 35篇 |
2002年 | 26篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 2篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1939年 | 4篇 |
1938年 | 3篇 |
1932年 | 4篇 |
1929年 | 5篇 |
1928年 | 1篇 |
1927年 | 2篇 |
1926年 | 3篇 |
排序方式: 共有1022条查询结果,搜索用时 10 毫秒
101.
102.
Two processes have been hypothesized to underlie improvement in perception: attunement and calibration. These processes were examined in a dynamic touch paradigm in which participants were asked to report the lengths of unseen, wielded rods differing in length, diameter, and material. Two experiments addressed whether feedback informs about the need for reattunement and recalibration. Feedback indicating actual length induced both recalibration and reattunement. Recalibration did not occur when feedback indicated only whether 2 rods were of the same length or of different lengths. Such feedback, however, did induce reattunement. These results suggest that attunement and calibration are dissociable processes and that feedback informs which is needed. The observed change in variable use has implications also for research on what mechanical variables underlie length perception by dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
Short tests containing at most 15 items are used in clinical and health psychology, medicine, and psychiatry for making decisions about patients. Because short tests have large measurement error, the authors ask whether they are reliable enough for classifying patients into a treatment and a nontreatment group. For a given certainty level, proportions of correct classifications were computed for varying test length, cut-scores, item scoring, and choices of item parameters. Short tests were found to classify at most 50% of a group consistently. Results were much better for tests containing 20 or 40 items. Small differences were found between dichotomous and polytomous (5 ordered scores) items. It is recommended that short tests for high-stakes decision making be used in combination with other information so as to increase reliability and classification consistency. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
We study the scheduling problem of minimizing the maximum starting time on-line. The goal is to minimize the last time that a job starts. We show that while the greedy algorithm has a competitive ratio of Θ (log m), we can give a constant competitive algorithm for this problem. We also show that the greedy algorithm is optimal for resource augmentation in the sense that it requires 2m − 1 machines to have a competitive ratio of 1, whereas no algorithm can achieve this with 2m − 2 machines. 相似文献
105.
Luca Aceto Wan Fokkink Rob van Glabbeek Anna Inglfsdttir 《Information and Computation》2004,191(2):203
This paper studies nested simulation and nested trace semantics over the language BCCSP, a basic formalism to express finite process behaviour. It is shown that none of these semantics affords finite (in)equational axiomatizations over BCCSP. In particular, for each of the nested semantics studied in this paper, the collection of sound, closed (in)equations over a singleton action set is not finitely based. 相似文献
106.
Eijsink Vincent G.H.; Vriend Gerrit; van den Burg Bertus; van der Zee J.Rob; Veltman Oene R.; Stulp Ben K.; Venema Gerard 《Protein engineering, design & selection : PEDS》1992,5(2):157-163
A 10 residue ß-hairpin, which is characteristic ofthermostable Bacillus neutral proteases, was engineered intothe thermolabile neutral protease of Bacillus subtilis. Therecipient enzyme remained fully active after introduction ofthe loop. However, the mutant protein exhibited autocatalyticnicking and a 0.4°C decrease in thermostability. Two additionalpoint mutations designed to improve the interactions betweenthe enzyme surface and the introduced ß-hairpin resultedin reduced nicking and increased thermostability. After theintroduction of both additional mutations in the loopcontainingmutant, nicking was largely prevented and an increase in thermostabilityof 1.1°C was achieved. 相似文献
107.
Feng Lin Dennis Nordlund Tsu‐Chien Weng Rob G. Moore Dane T. Gillaspie Kim M. Jones Anne C. Dillon Ryan M. Richards Chaiwat Engtrakul 《Advanced Materials Interfaces》2015,2(6)
Interface engineering has attracted great interest and is essential for the fabrication of thin‐film devices, such as smart windows. In this study, a solid‐state conversion reaction for the development of an interlayer enriched with lithium peroxide (Li2O2) is presented for an electrochromic device. We demonstrate that efficient lithium insertion and electron transport can be achieved by the inclusion of a Li2O2‐rich interlayer between an active electrochromic material and Li ion solid‐state electrolyte layer. The presence of a Li2O2‐rich interlayer enhances electrochromic efficiency, kinetics, optical contrast, and bleached‐state transparency in a nickel oxide‐based electrochromic thin film. This work opens up new opportunities to enhance the functionalities of thin‐film devices by solid‐state conversion reactions. 相似文献
108.
Specific sleepiness symptoms are indicators of performance impairment during sleep deprivation 总被引:1,自引:0,他引:1
Mark E. Howard Melinda L. Jackson David Berlowitz Fergal O’Donoghue Philip Swann Justine Westlake Vanessa Wilkinson Rob J. Pierce 《Accident; analysis and prevention》2014
Drivers are not always aware that they are becoming impaired as a result of sleepiness. Using specific symptoms of sleepiness might assist with recognition of drowsiness related impairment and help drivers judge whether they are safe to drive a vehicle, however this has not been evaluated. In this study, 20 healthy volunteer professional drivers completed two randomized sessions in the laboratory – one under 24 h of acute sleep deprivation, and one with alcohol. The Psychomotor Vigilance Task (PVT) and a 30 min simulated driving task (AusEdTM) were performed every 3–4 h in the sleep deprivation session, and at a BAC of 0.00% and 0.05% in the alcohol session, while electroencephalography (EEG) and eye movements were recorded. After each test session, drivers completed the Karolinska Sleepiness Scale (KSS) and the Sleepiness Symptoms Questionnaire (SSQ), which includes eight specific sleepiness and driving performance symptoms. A second baseline session was completed on a separate day by the professional drivers and in an additional 20 non-professional drivers for test–retest reliability. There was moderate test–retest agreement on the SSQ (r = 0.59). Significant correlations were identified between individual sleepiness symptoms and the KSS score (r values 0.50–0.74, p < 0.01 for all symptoms). The frequency of all SSQ items increased during sleep deprivation (χ2 values of 28.4–80.2, p < 0.01 for all symptoms) and symptoms were related to increased subjective sleepiness and performance deterioration. The symptoms “struggling to keep your eyes open”, “difficulty maintaining correct speed”, “reactions were slow” and “head dropping down” were most closely related to increased alpha and theta activity on EEG (r values 0.49–0.59, p < 0.001) and “nodding off to sleep” and “struggling to keep your eyes open” were related to slow eye movements (r values 0.67 and 0.64, p < 0.001). Symptoms related to visual disturbance and impaired driving performance were most accurate at detecting severely impaired driving performance (AUC on ROC curve of 0.86–0.91 for detecting change in lateral lane position greater than the change at a BAC of 0.05%). Individual sleepiness symptoms are related to impairment during acute sleep deprivation and might be able to assist drivers in recognizing their own sleepiness and ability to drive safely. 相似文献
109.
Technological learning in bioenergy systems 总被引:1,自引:0,他引:1
Martin Junginger Erika de Visser Kurt Hjort-Gregersen Joris Koornneef Rob Raven Andr Faaij Wim Turkenburg 《Energy Policy》2006,34(18):4024-4041
The main goal of this article is to determine whether cost reductions in different bioenergy systems can be quantified using the experience curve approach, and how specific issues (arising from the complexity of biomass energy systems) can be addressed. This is pursued by case studies on biofuelled combined heat and power (CHP) plants in Sweden, global development of fluidized bed boilers and Danish biogas plants. As secondary goal, the aim is to identify learning mechanisms behind technology development and cost reduction for the biomass energy systems investigated. The case studies reveal large difficulties to devise empirical experience curves for investment costs of biomass-fuelled power plants. To some extent, this is due to lack of (detailed) data. The main reason, however, are varying plant costs due to differences in scale, fuel type, plant layout, region etc. For fluidized bed boiler plants built on a global level, progress ratios (PRs) for the price of entire plants lies approximately between 90–93% (which is typical for large plant-like technologies). The costs for the boiler section alone was found to decline much faster. The experience curve approach delivers better results, when the production costs of the final energy carrier are analyzed. Electricity from biofuelled CHP-plants yields PRs of 91–92%, i.e. an 8–9% reduction of electricity production costs with each cumulative doubling of electricity production. The experience curve for biogas production displays a PR of 85% from 1984 to the beginning of 1990, and then levels to approximately 100% until 2002. For technologies developed on a local level (e.g. biogas plants), learning-by-using and learning-by-interacting are important learning mechanism, while for CHP plants utilizing fluidized bed boilers, upscaling is probably one of the main mechanisms behind cost reductions. 相似文献
110.
Guoliang Zhu Yongbing Dai Da Shu Yanping Xiao Yongxiang Yang Jun Wang Baode Sun Rob Boom 《Computational Materials Science》2011,50(9):2636-2639
The formation energies of various point defects in Al3Ti(D022) have been calculated by using first-principles calculation. The effects of vacancies on Si site preference were examined to better understand Si substitution behavior in Al3Ti. The results show that, under Al-rich condition, the formation energy of antisite AlTi is the lowest than those of other point defects, and Ti vacancy is more preferred than Al vacancy. But Si prefers to occupy Al vacancy compared with Ti vacancy which causes a finite solubility of Si in Al3Ti system. The calculation is instructive for the further improvements of process of Si removal. 相似文献