全文获取类型
收费全文 | 4154篇 |
免费 | 566篇 |
国内免费 | 193篇 |
专业分类
电工技术 | 1460篇 |
技术理论 | 1篇 |
综合类 | 276篇 |
化学工业 | 167篇 |
金属工艺 | 124篇 |
机械仪表 | 174篇 |
建筑科学 | 265篇 |
矿业工程 | 146篇 |
能源动力 | 277篇 |
轻工业 | 24篇 |
水利工程 | 248篇 |
石油天然气 | 275篇 |
武器工业 | 42篇 |
无线电 | 401篇 |
一般工业技术 | 265篇 |
冶金工业 | 419篇 |
原子能技术 | 31篇 |
自动化技术 | 318篇 |
出版年
2024年 | 32篇 |
2023年 | 94篇 |
2022年 | 176篇 |
2021年 | 185篇 |
2020年 | 219篇 |
2019年 | 167篇 |
2018年 | 165篇 |
2017年 | 213篇 |
2016年 | 194篇 |
2015年 | 199篇 |
2014年 | 329篇 |
2013年 | 278篇 |
2012年 | 335篇 |
2011年 | 348篇 |
2010年 | 191篇 |
2009年 | 195篇 |
2008年 | 163篇 |
2007年 | 203篇 |
2006年 | 192篇 |
2005年 | 159篇 |
2004年 | 141篇 |
2003年 | 139篇 |
2002年 | 111篇 |
2001年 | 103篇 |
2000年 | 78篇 |
1999年 | 61篇 |
1998年 | 55篇 |
1997年 | 29篇 |
1996年 | 28篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有4913条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(38):17056-17068
The study of steels which guarantee safety and reliability throughout their service life in hydrogen-rich environments has increased considerably in recent years. Their mechanical behavior in terms of hydrogen embrittlement is of utmost importance. This work aims to assess the effects of hydrogen on the tensile properties of quenched and tempered 42CrMo4 steels. Tensile tests were performed on smooth and notched specimens under different conditions: pre-charged in high pressure hydrogen gas, electrochemically pre-charged, and in-situ hydrogen charged in an acid aqueous medium. The influence of the charging methodology on the corresponding embrittlement indexes was assessed. The role of other test variables, such as the applied current density, the electrolyte composition, and the displacement rate was also studied. An important reduction of the strength was detected when notched specimens were subjected to in-situ charging. When the same tests were performed on smooth tensile specimens, the deformation results were reduced. This behavior is related to significant changes in the operative failure micromechanisms, from ductile (microvoids coalescence) in absence of hydrogen or under low hydrogen contents, to brittle (decohesion of martensite lath interfaces) under the most stringent conditions. 相似文献
2.
A low pressure impactor is used to measure triboelectric charging behavior of metallic nanoparticles. Ag nanoparticles, produced by spark discharge, were impacted onto Pt sputtered targets. The influence of the impaction angle and impaction velocity on the triboelectric charging was investigated. While for perpendicular impaction the charge transfer behavior of previous work was confirmed, the oblique impaction revealed new phenomena. Additional charge transfer was observable, which increases with obliqueness. The possibility of mass transfer between particle and target due to the high-energy collisions was also investigated. SEM characterization and Auger spectroscopy indicate mass transfer from the particle to the target surface. 相似文献
3.
Zhi Li Wenju Wang Meng Ye Xuedong Liang 《International Journal of Hydrogen Energy》2021,46(35):18453-18465
Lack of hydrogen refueling stations (HRSs) has hindered the diffusion of hydrogen fuel cell vehicles (HFCVs) in the Chinese transport market. By combining the agent-based model (ABM) and the experience weighted attraction (EWA) learning algorithm, this paper explores the impact of government subsidy strategy for HRSs on the market diffusion of HFCVs. The actions of the parties (government, HRS planning department and consumers) and their interactions are taken into account. The new model suggests dynamic subsidy mode based on EWA algorithm yields better results than static subsidy mode: HFCV purchases, HRS construction effort, total number of HRSs and expected HRS planning department profits all outperform static data by around 27%. In addition, choosing an appropriate initial subsidy strategy can increase the sales of HFCVs by nearly 40%. Early investment from government to establish initial HRSs can also increase market diffusion efficiency by more than 76.7%. 相似文献
4.
《International Journal of Hydrogen Energy》2020,45(35):17671-17684
The effect of microstructural features on the hydrogen induced cracking (HIC) susceptibility of two API 5L X65 pipeline steels were investigated by cathodic charging, hydrogen permeation and hydrogen microprint experiments. Microstructural evaluation after hydrogen charging revealed cracks at the mid-thickness (segregation zone) of both plates. However, more severe cracks were observed in the plate with higher dislocation density and residual stresses. The plate with lower plastic strain and more {111}-oriented grains had less severe cracks. Inclusions found along the crack path, comprising of Si-enriched oxides and carbides contributed to the initiation and propagation of cracks. The variation of the trapping behaviour and hydrogen diffusion through the plates were examined. The results confirmed that a higher ratio of reversible to irreversible traps contributes to increasing HIC severity in steels. Additionally, hydrogen transport through the steels was most prominent along the grain boundaries, indicating the importance of grain boundary character to HIC. 相似文献
5.
《International Journal of Hydrogen Energy》2020,45(38):19900-19911
The Republic of Korea government has set yearly targets of hydrogen cars and buses and plans to install hydrogen refueling stations nationwide. This paper proposes a methodology for developing a strategic deployment plan with three mathematical models. For a given target, future refueling demand locations and amount from general road and expressway are systematically estimated. First, the required number of refueling stations to satisfy the target covering ratio of the total demand set by the government is determined by the Station number determination model. Next, the locations of the capacitated stations and the allocation of demand to the stations are determined by the second Max cover and the third p-median models. Since the max covering is more important than minimizing the travel time, the two models are used sequentially. The nationwide hydrogen station deployment plan for the years 2022–2040 obtained by the proposed methodology is reported. 相似文献
6.
《International Journal of Hydrogen Energy》2021,46(60):30698-30717
As of January 2021, Japan had the world's largest hydrogen station network with merely 4600 hydrogen fuel-cell vehicles (HFCVs) on roads, as compared to the 9000 HFCVs in the US, with only one-third of the hydrogen refueling stations in Japan. To understand behavioral differences among Japanese adopters, we administered a survey, in cooperation with public and private sector stakeholders, involving 89 private HFCV adopters in the Aichi Prefectural region, which hosts the largest number of HFCVs and refueling stations in Japan. Results suggest that HFCV adopters have a higher socioeconomic status than non-adopters, are mostly male in their 50s and above, and have a higher interest in new vehicle fuel technology. HFCV adopters who leased and bought vehicles were similar in terms of socioeconomic status, with differences in attitudes toward governmental incentives. The lack of refueling stations and station business hours restrict HFCV adopters from continuing with this fuel technology. 相似文献
7.
Effects of Smart Charging of Multiple Electric Vehicles in Reducing Power Generation Fuel Cost 下载免费PDF全文
Takashi Ikegami Hitoshi Yano Koji Kudo Kazuhiko Ogimoto 《Electrical Engineering in Japan》2015,193(2):42-57
The high penetration of variable sources of renewable power generation will lead to operational difficulties in supply/demand balancing in the entire power system. The mass deployment of electric vehicles (EVs) and plug‐in hybrid vehicles (PHEVs) will also cause significant changes in electricity demand. Therefore, controlling and managing the charging time of EVs/PHEVs are effective approaches that are imperative for improving balancing in power system operation. We assumed travel patterns for EVs in a model of the future Tokyo power system and analyzed the power system loads, including the charging load of the EVs, under several charging control scenarios. We verified that charging time controls are substantially effective for reducing the fuel costs in the power system. Further, we found that load leveling under a multicar charging management scenario gave the best results in terms of the fuel costs in all cases. 相似文献
8.
安彦玲 《锻压装备与制造技术》2020,(2):28-31
立捣卧挤炭素挤压机采用立式捣固预压,卧式挤压,旋转料室+延长料室结构,旋转料室和延伸料室均采用过盈配合,粗加工后要进行热装,压机整体高度较高,由于厂内不具备现场安装条件,导致装配难度很大,通过工艺和装配攻关,确定合理的安装方案,制作专用工装工具,采取相应措施,保证装配精度符合要求。 相似文献
9.
10.
刘刚 《中国水能及电气化》2020,(4):30-32,52
水电站厂用电指标使用综合厂用率,反映电站厂用电消耗的实际情况,可通过厂用电率合理性分析电站厂用耗电情况以及节能降耗挖潜的空间,促进厂用电的合理管理,提高电站效益。文章结合华能甘肃水电开发有限公司管控的6座小型水电站厂用电管理实践,分析了影响水电厂用电损耗的相关因素,提出了厂用电节能降耗的应对措施。 相似文献