全文获取类型
收费全文 | 652541篇 |
免费 | 54384篇 |
国内免费 | 33085篇 |
专业分类
电工技术 | 62275篇 |
技术理论 | 87篇 |
综合类 | 78082篇 |
化学工业 | 53913篇 |
金属工艺 | 23477篇 |
机械仪表 | 47156篇 |
建筑科学 | 80907篇 |
矿业工程 | 30054篇 |
能源动力 | 23023篇 |
轻工业 | 31185篇 |
水利工程 | 28094篇 |
石油天然气 | 25434篇 |
武器工业 | 7733篇 |
无线电 | 49247篇 |
一般工业技术 | 45265篇 |
冶金工业 | 30673篇 |
原子能技术 | 7216篇 |
自动化技术 | 116189篇 |
出版年
2024年 | 905篇 |
2023年 | 5975篇 |
2022年 | 11608篇 |
2021年 | 15023篇 |
2020年 | 16012篇 |
2019年 | 12733篇 |
2018年 | 12042篇 |
2017年 | 15555篇 |
2016年 | 19010篇 |
2015年 | 21252篇 |
2014年 | 40657篇 |
2013年 | 36718篇 |
2012年 | 46601篇 |
2011年 | 50310篇 |
2010年 | 38411篇 |
2009年 | 39525篇 |
2008年 | 38150篇 |
2007年 | 48291篇 |
2006年 | 43846篇 |
2005年 | 38225篇 |
2004年 | 32110篇 |
2003年 | 28682篇 |
2002年 | 22827篇 |
2001年 | 18821篇 |
2000年 | 15609篇 |
1999年 | 12646篇 |
1998年 | 9710篇 |
1997年 | 8106篇 |
1996年 | 7345篇 |
1995年 | 6327篇 |
1994年 | 5403篇 |
1993年 | 3952篇 |
1992年 | 3426篇 |
1991年 | 2539篇 |
1990年 | 2156篇 |
1989年 | 1865篇 |
1988年 | 1477篇 |
1987年 | 942篇 |
1986年 | 765篇 |
1985年 | 692篇 |
1984年 | 676篇 |
1983年 | 562篇 |
1982年 | 425篇 |
1981年 | 307篇 |
1980年 | 270篇 |
1979年 | 217篇 |
1978年 | 136篇 |
1977年 | 139篇 |
1976年 | 110篇 |
1959年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
深凹露天矿山由于其特殊的结构,爆破产生的炮烟扩散稀释较为困难,严重危害生产作业人员的生命安全与健康。基于实际矿山构建了深凹露天矿山的二维物理及数学模型,采用非稳态数值分析方法研究了不同爆破位置下,深凹露天矿山采坑内爆破炮烟的扩散规律。研究结果表明:不同爆破位置下,露天采坑内均出现复环流,爆破点位置是影响露天采坑内风流结构特征的重要因素;露天采坑内的炮烟最高浓度均随着时间变化而逐渐下降,但下降的速率逐步减小,呈现三个阶段的下降趋势;爆破位置位于背风侧时露天采坑内的炮烟最高浓度和降至安全浓度所需时间远高于迎风侧三个爆破位置;随着背风侧爆破点距采坑底部距离的减小,炮烟最高浓度及降至安全浓度所需时间先降低后增加,炮烟最高浓度及降至安全浓度所需时间随着迎风侧爆破位置距采坑底部距离的减小而增加。研究结果对于指导深凹露天矿山企业合理组织爆破后的生产作业和保障作业人员安全具有重要意义。 相似文献
3.
4.
5.
6.
7.
《International Journal of Hydrogen Energy》2022,47(85):36216-36231
The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(62):26435-26457
In this study, some locations with different climates, off-grid zero energy buildings with hydrogen energy storage systems are designed, and transient analysis is conducted. These considered buildings supply their electricity consumption without using the electrical grid and PV panels or wind turbines. Also, they supply thermal comfort to occupants by using a vapor compression chiller and humidifier. Domestic hot water of occupants is supplied using solar collectors. For analyzing building's performance and objectives achievement, TRNSYS software is used. Also, for evaluating occupant thermal comfort, the Fanger model is used. The considered building is a one-story building with a 150 m2 area. Four occupants are considered. Both of them are seated at rest, and another is seated with light working such as typing. Using the Fanger model equation and MATLAB software, the thermal comfort of occupants is determined. For domestic hot water consumption, verified profiles that vary during 24 h of the day are considered. Achieved results show that for humid and cold cities, PV panels with an area of 73 and 76 m2 can be supplied the required electricity of considered building with four occupants and battery state of charge is higher than 50% and 10%, respectively. Moreover, with a suitable air conditioner system, the predicted percentage of dissatisfied (PPD) can be lower than 12% and 8% for humid and cold cities. Therefore, the building can be converted to a zero-energy building using its rooftop area. 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(65):28152-28164
The combustion characteristics of ammonia/methanol mixtures were investigated numerically in this study. Methanol has a dramatic promotive effect on the laminar burning velocity (LBV) of ammonia. Three mechanisms from literature and another four self-developed mechanisms constructed in this study were evaluated using the measured laminar burning velocities of ammonia/methanol mixtures from Wang et al. (Combust.Flame. 2021). Generally, none of the selected mechanisms can precisely predict the measured laminar burning velocities at all conditions. Aiming to develop a simplified and reliable mechanism for ammonia/methanol mixtures, the constructed mechanism utilized NUI Galway mechanism (Combust.Flame. 2016) as methanol sub-mechanism and the Otomo mechanism (Int. J. Hydrogen. Energy. 2018) as ammonia sub-mechanism was optimized and reduced. The reduced mechanism entitled ‘DNO-NH3’, can accurately reproduce the measured laminar burning velocities of ammonia/methanol mixtures under all conditions. A reaction path analysis of the ammonia/methanol mixtures based on the DNO-NH3 mechanism shows that methanol is not directly involved in ammonia oxidation, instead, the produced methyl radicals from methanol oxidization contribute to the dehydrogenation of ammonia. Besides, NOx emission analysis demonstrates that 60% methanol addition results in the highest NOx emissions. The most important reactions dominating the NOx consumption and production are identified in this study. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(67):29172-29183
To improve the safety of wet dust removal systems for processing magnesium-based alloys, a new method is proposed for preventing hydrogen generation. In this paper, hydrogen generation by Mg–Zn alloy dust was inhibited with six common metal corrosion inhibitors. The results showed that sodium dodecylbenzene sulfonate was the best hydrogen inhibitor, while CeCl3 enhanced hydrogen precipitation. The film-forming stability of sodium dodecylbenzene sulfonate was tested with different contents, temperatures, Cl? concentrations and perturbation rates. The results showed that this inhibitor formed stable protective films on the surfaces of Mg–Zn alloy particles, and adsorption followed the Langmuir adsorption model. 相似文献