全文获取类型
收费全文 | 19403篇 |
免费 | 1580篇 |
国内免费 | 710篇 |
专业分类
电工技术 | 869篇 |
综合类 | 1778篇 |
化学工业 | 1626篇 |
金属工艺 | 2186篇 |
机械仪表 | 1479篇 |
建筑科学 | 2985篇 |
矿业工程 | 521篇 |
能源动力 | 1080篇 |
轻工业 | 1070篇 |
水利工程 | 630篇 |
石油天然气 | 657篇 |
武器工业 | 162篇 |
无线电 | 797篇 |
一般工业技术 | 2532篇 |
冶金工业 | 2185篇 |
原子能技术 | 175篇 |
自动化技术 | 961篇 |
出版年
2024年 | 54篇 |
2023年 | 166篇 |
2022年 | 440篇 |
2021年 | 549篇 |
2020年 | 542篇 |
2019年 | 436篇 |
2018年 | 369篇 |
2017年 | 524篇 |
2016年 | 541篇 |
2015年 | 602篇 |
2014年 | 1194篇 |
2013年 | 991篇 |
2012年 | 1417篇 |
2011年 | 1586篇 |
2010年 | 1245篇 |
2009年 | 1187篇 |
2008年 | 999篇 |
2007年 | 1255篇 |
2006年 | 1140篇 |
2005年 | 965篇 |
2004年 | 826篇 |
2003年 | 779篇 |
2002年 | 672篇 |
2001年 | 584篇 |
2000年 | 504篇 |
1999年 | 448篇 |
1998年 | 361篇 |
1997年 | 275篇 |
1996年 | 215篇 |
1995年 | 209篇 |
1994年 | 153篇 |
1993年 | 103篇 |
1992年 | 79篇 |
1991年 | 67篇 |
1990年 | 48篇 |
1989年 | 51篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 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.
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
4.
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
5.
LNG冷量优化集成利用技术 总被引:7,自引:1,他引:6
我国将相继在沿海地区建成多个LNG接收站,每年将进口数以千万吨计的LNG,同时携带数着巨额冷量,而这些冷量可用于发电、空气分离、制造干冰、低温冷库等众多领域。基于国外LNG冷量利用现状,指出我国即将展开和实施此项技术还存在着:过程火用损较大,缺乏系统、全面的LNG冷量利用技术的研发指导机制,以及宏观调控力度薄弱等问题,进而提出了发展LNG冷量的集成利用方案,可为此类技术的研发利用提供新思路。以福建即将进口的LNG为例,模拟了空气分离与干冰制备的集成工艺流程,结果表明:福建每年进口的260×104t LNG可以冷却290×104t空气,相当于60000 m3/h的氧气制备规模,还可以生产100×104t的干冰,其过程火用损较小;其剩余的高温位冷量可应用于低温冻结库或冰灯等项目,这对主体装置的实施效果和过程火用损的影响较小。该技术的优点在于可灵活控制冷却空气的液化率,基本不用冷却循环水,流程简单,设备投资少,能耗低等。 相似文献
6.
沉管隧道水下最终接头施工技术初探 总被引:1,自引:0,他引:1
简述了沉管隧道水下最终接头施工技术的应用现状,结合具体隧道工程实例,从外模工程、混凝土结构两方面介绍了最终接头施工技术,表明了该技术具有运用价值。 相似文献
7.
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
8.
Myers Nicholas D.; Payment Craig A.; Feltz Deborah L. 《Canadian Metallurgical Quarterly》2004,8(3):182
This study examined reciprocal relationships between collective efficacy and team performance over a season of competition in women's intercollegiate ice hockey within weekends where the opponent was constant for 2 games. Collective efficacy beliefs within 12 teams were assessed prior to both games for at least 7 weekends. Team performance indexes produced an overall measure of performance for each game. The average influence of Saturday collective efficacy on Saturday performance was moderate and positive after controlling for Friday performance. The average influence of Friday performance on Saturday collective efficacy was small and positive after removing the influence of Friday collective efficacy from Friday performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
10.