全文获取类型
收费全文 | 247篇 |
免费 | 13篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 63篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 24篇 |
能源动力 | 12篇 |
轻工业 | 42篇 |
水利工程 | 1篇 |
无线电 | 9篇 |
一般工业技术 | 45篇 |
冶金工业 | 23篇 |
自动化技术 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 27篇 |
2012年 | 15篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有260条查询结果,搜索用时 15 毫秒
1.
2.
3.
A series active power filter working as a sinusoidal current source, in-phase with the mains voltage, has been developed and tested. The amplitude of the fundamental current in the series filter is controlled through the error signal generated between the load voltage and a pre-established reference. The control allows an effective correction of power factor, harmonic distortion and load voltage regulation. Compared with previous methods of control developed for series active filters, this method is simpler to implement because it is only required to generate a sinusoidal current, in-phase with the mains voltage, the amplitude of which is controlled through the error in the load voltage. The proposed system has been studied analytically and tested using computer simulations and experiments. In the experiments, it has been verified that the filter keeps the line current almost sinusoidal and in-phase with the line voltage supply. It also responds very quickly under sudden changes in load conditions, reaching its steady-state in about two cycles of the fundamental 相似文献
4.
The main purpose of the study reported here was to investigate the relative importance of complexity of syllable structure and task differences in measuring phonological awareness in low-literacy adults. This study is a replication of a study with children conducted by S. A. Stahl and B. A. Murray (1994). Results indicated that the complexity of syllable structure did indeed better describe the construct of phonological awareness in low-literacy adults. At the same time, the authors also found some differences in the pattern of literacy acquisition for their Spanish adults in comparison with child literacy acquisition in English. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
We analyze the classic board game of Mastermind with n holes and a constant number of colors. The classic result of Chvátal (Combinatorica 3:325–329, 1983) states that the codebreaker can find the secret code with Θ(n/logn) questions. We show that this bound remains valid if the codebreaker may only store a constant number of guesses and answers. In addition to an intrinsic interest in this question, our result also disproves a conjecture of Droste, Jansen, and Wegener (Theory Comput. Syst. 39:525–544, 2006) on the memory-restricted black-box complexity of the OneMax function class. 相似文献
6.
7.
Prediction of parking space availability in real time 总被引:1,自引:0,他引:1
Intelligent parking reservation (IPR) systems allow customers to select a parking facility according to their preferences, rapidly park their vehicle without searching for a free stall, and pay their reservation in advance avoiding queues. Some IPR systems interact with in-vehicle navigation systems and provide users with information in real time such as capacity, parking fee, and current parking utilization. However, few of these systems provide information on the forecast utilization at specific hours - a process that requires the study of the competition between parking alternatives for the market share. This paper proposes a methodology for predicting real-time parking space availability in IPR architectures. This methodology consists of three subroutines to allocate simulated parking requests, estimate future departures, and forecast parking availability. Parking requests are allocated iteratively using an aggregated approach as a function of simulated drivers’ preferences, and parking availability. This approach is based on a calibrated discrete choice model for selecting parking alternatives. A numerical comparison between a one-by-one simulation-based forecast and the proposed aggregated approach indicates that no significant discrepancies exists, validating and suggesting the use of the less time consuming proposed aggregated methodology. Results obtained from contrasting predictions with real data yielded small average error availabilities. The forecast improves as the system registers arrivals and departures. Thus, the forecast is adequate for potential distribution in real-time using different media such as Internet, navigation systems, cell phones or GIS. 相似文献
8.
Modeling and performance analysis of an absorption chiller with a microchannel membrane‐based absorber using LiBr‐H2O,LiCl‐H2O,and LiNO3‐NH3
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In order to develop compact absorption refrigeration cycles driven by low heat sources, the simulated performance of a microchannel absorber of 5‐cm length and 9.5 cm3 in volume provided with a porous membrane is presented for 3 different solution‐refrigerant pairs: LiBr‐H2O, LiCl‐H2O, and LiNO3‐NH3. The high absorption rates calculated for the 3 solutions lead to large cooling effect to absorber volume ratios: 625 kW/m3 for the LiNO3‐NH3, 552 kW/m3 for the LiBr‐H2O, and 318 kW/m3 for the LiCl‐H2O solutions given the studied geometry. The performance of a complete absorption system is also analyzed varying the solution concentration, condensation temperature, and desorption temperature. The LiNO3‐NH3 and the LiBr‐H2O solutions provide the largest cooling effects. The LiNO3‐NH3 can work at a lower temperature of the heating source, in comparison with the one needed in a LiBr‐H2O system. The lowest cooling effect and coefficient of performance are found for the LiCl‐H2O solution, but this mixture allows the use of lower temperature heating sources (below 70°C). These results can be used for the selection of the most suitable solution for a given cooling duty, depending on the available heat source and condensation temperature. 相似文献
9.
Carola de Groot Dorien Manting Clara H. Mulder 《Journal of Housing and the Built Environment》2013,28(3):469-488
This study investigates how life course characteristics and housing market circumstances affect the formation and realisation of preferences to move into homeownership. Using a data set from the Netherlands in which data from three cross-sectional housing surveys are enriched with longitudinal register data for the period 1998–2008, we follow aspiring homeowners regarding their actual residential behaviour. We find that only 31 % of the aspiring homeowners became homeowners within 2 years, approximately 13 % moved to rental homes, and the vast majority did not move at all. Insufficient socioeconomic resources and a high house price-to-rent ratio hamper the realisation of preferences to move into homeownership. However, these hampering factors are at least as important as the extent to which individuals prefer to move into homeownership. This last finding suggests that housing tenure preferences cannot be viewed as ‘pure’ preferences. 相似文献
10.
Anja Wessely Theresa Steeb Ulrike Leiter Claus Garbe Carola Berking Markus Vincent Heppt 《International journal of molecular sciences》2020,21(23)
Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer that predominantly arises in chronically sun-damaged skin. Immunosuppression, genetic disorders such as xeroderma pigmentosum (XP), exposure to certain drugs and environmental noxae have been identified as major risk factors. Surgical removal of cSCC is the therapy of choice and mostly curative in early stages. However, a minority of patients develop locally advanced tumors or distant metastases that are still challenging to treat. Immune checkpoint blockade (ICB) targeting CTLA-4, PD-L1 and PD-1 has tremendously changed the field of oncological therapy and especially the treatment of skin cancers as tumors with a high mutational burden. In this review, we focus on the differences between cSCC and cutaneous melanoma (CM) and their implications on therapy, summarize the current evidence on ICB for the treatment of advanced cSCC and discuss the chances and pitfalls of this therapy option for this cancer entity. Furthermore, we focus on special subgroups of interest such as organ transplant recipients, patients with hematologic malignancies, XP and field cancerization. 相似文献