全文获取类型
收费全文 | 20981篇 |
免费 | 1734篇 |
国内免费 | 780篇 |
专业分类
电工技术 | 660篇 |
综合类 | 2041篇 |
化学工业 | 1621篇 |
金属工艺 | 2301篇 |
机械仪表 | 1821篇 |
建筑科学 | 3206篇 |
矿业工程 | 1082篇 |
能源动力 | 1025篇 |
轻工业 | 609篇 |
水利工程 | 452篇 |
石油天然气 | 831篇 |
武器工业 | 223篇 |
无线电 | 932篇 |
一般工业技术 | 2542篇 |
冶金工业 | 2534篇 |
原子能技术 | 173篇 |
自动化技术 | 1442篇 |
出版年
2024年 | 71篇 |
2023年 | 180篇 |
2022年 | 462篇 |
2021年 | 599篇 |
2020年 | 614篇 |
2019年 | 476篇 |
2018年 | 389篇 |
2017年 | 585篇 |
2016年 | 616篇 |
2015年 | 700篇 |
2014年 | 1306篇 |
2013年 | 1069篇 |
2012年 | 1573篇 |
2011年 | 1672篇 |
2010年 | 1312篇 |
2009年 | 1286篇 |
2008年 | 1051篇 |
2007年 | 1410篇 |
2006年 | 1221篇 |
2005年 | 1028篇 |
2004年 | 894篇 |
2003年 | 839篇 |
2002年 | 695篇 |
2001年 | 623篇 |
2000年 | 538篇 |
1999年 | 455篇 |
1998年 | 379篇 |
1997年 | 286篇 |
1996年 | 231篇 |
1995年 | 230篇 |
1994年 | 170篇 |
1993年 | 117篇 |
1992年 | 87篇 |
1991年 | 73篇 |
1990年 | 54篇 |
1989年 | 58篇 |
1988年 | 30篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 5篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1964年 | 4篇 |
1958年 | 3篇 |
1956年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(40):17737-17748
Due to problems such as pores on surface-treated coatings, the corrosion resistance of pure titanium bipolar plates for proton-exchange membrane fuel cells can be further improved by increasing the corrosion resistance of pure titanium by using differential speed-rolling (DSR); however, these materials have not yet reached the standard requirements of bipolar plates (corrosion current density icorr<103 nA·cm?2). In this work, the corrosion resistance of pure titanium was improved by optimizing the DSR process while the strength was maintained. The best corrosion resistance of the DSR pure titanium was achieved when the roller speed ratio was 2, while icorr was 429 nA·cm?2 in a solution of 0.5 M H2SO4 and 2 mg/L HF at room temperature. The formability of the DSR pure titanium for bipolar plates was verified. The optimal holding pressure range was 6.8–7.0 kN. 相似文献
2.
《Journal of the European Ceramic Society》2022,42(5):2429-2440
A ring-on-ring (ROR) test is a prevailing test method for evaluating the equi-biaxial strength of glass materials. However, current ROR test standards limit the strength and size of glass to prevent a nonlinear behavior. In this study, the feasibility of ROR testing for non-standard, high-strength glass, such as tempered or ion-exchanged rectangular glass is investigated. To this end, ROR simulation based on theory and experiment is conducted for thirty non-standard glasses with widths of 100–300 mm and aspect ratios of 1.0–2.0. As a result, the maximum measurable stress was about 215.6 MPa for 100 × 200 mm glass and 481.3 MPa for 300 × 600 mm glass with a 3% deviation, which is well above the strength of regular tempered glass. The main purpose of this work is to understand the range of aspect ratio of horizontal and vertical widths of a glass plate that can be evaluated by the standard ROR test. 相似文献
3.
Lauren Folk Kiara Gonzales John Gales Michael Kinsey Elisabetta Carattin Tim Young 《火与材料》2020,44(4):585-606
Practitioners are continuing to develop egress modelling software for the design of the built environment. These models require data about human behaviour and factors for calibration, validation and verification. This study aims to address the specific data and knowledge gap: emergency egress of the elderly. Such data are difficult to collect given privacy and consent concerns, with strong relationships generally being required between residences and researchers. Through the observation of nine fire drills at six Canadian long-term care (LTC) and retirement homes, specific evacuation actions and behaviour were observed for 37 staff members and information about the evacuation of 56 residents was collected. These drills demonstrated that emergency egress in LTC and retirement homes is highly staff dependent with 72% of residents recorded requiring full assistance at all stages of movement in evacuation, and that the type of announced/unannounced drill and level of resident care will affect the type of data collected. The development of travel speed and pre-movement is discussed subject to limitation with qualitative behavioural insights of residents that were observed. This study provides valuable methodological discussion on how to conduct behavioural studies in similar highly restricted research environments. Specific attention is given to understanding the considerations that must be made when using fire drills as data sources, and the impact that these can have on using such data for modelling. This study may inform the initial setup and programming of evacuation models from an actions and behavioural perspectives of staff members and residents. 相似文献
4.
In this article, two novel kinds of focusing elements as reflectors are analyzed and compared. One is the grooved Fresnel zone plate reflector with continuous phase‐correcting. The other called subzone paraboloid reflector, has the profile that consists of a series of paraboloids. Their diffraction efficiencies and bandwidths are described. The two elements still preserve the advantages of Fresnel zone plates, namely, low profile, high efficiency, and simple fabrication. Two dual‐reflector antennas using the proposed focusing elements as the main reflectors are simulated and the results show that these antennas have good radiation performances. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:101–108, 2015. 相似文献
5.
G. Inglese 《Inverse Problems in Science & Engineering》2019,27(4):439-459
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation. 相似文献
6.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
7.
8.
热镀锌板(卷)工程设计中的环境保护问题 总被引:1,自引:0,他引:1
对热镀锌板(卷)的生产工艺、主要生产设备进行了简要介绍,并就其污染源(工序)、生产过程中产生的污染物及其控制措施进行了评述,同时就设计和生产中宜注意的几个环保问题进行了分析。 相似文献
9.
10.
本文就利用诸如蛋白石这样的疏松多孔矿料同灰土构成的混合料,在路面结构中表现出的独特有效的抗冻作用机理作了深入分析,并结合足尺试验数据加以验证。阐述了所谓多孔板体结构的概念、机制和材料组成要求。 相似文献