全文获取类型
收费全文 | 6969篇 |
免费 | 681篇 |
国内免费 | 501篇 |
专业分类
电工技术 | 553篇 |
综合类 | 454篇 |
化学工业 | 983篇 |
金属工艺 | 203篇 |
机械仪表 | 343篇 |
建筑科学 | 571篇 |
矿业工程 | 567篇 |
能源动力 | 301篇 |
轻工业 | 257篇 |
水利工程 | 93篇 |
石油天然气 | 219篇 |
武器工业 | 684篇 |
无线电 | 299篇 |
一般工业技术 | 920篇 |
冶金工业 | 199篇 |
原子能技术 | 119篇 |
自动化技术 | 1386篇 |
出版年
2024年 | 22篇 |
2023年 | 60篇 |
2022年 | 246篇 |
2021年 | 182篇 |
2020年 | 180篇 |
2019年 | 157篇 |
2018年 | 135篇 |
2017年 | 235篇 |
2016年 | 223篇 |
2015年 | 237篇 |
2014年 | 406篇 |
2013年 | 418篇 |
2012年 | 471篇 |
2011年 | 581篇 |
2010年 | 453篇 |
2009年 | 457篇 |
2008年 | 395篇 |
2007年 | 482篇 |
2006年 | 484篇 |
2005年 | 404篇 |
2004年 | 326篇 |
2003年 | 296篇 |
2002年 | 223篇 |
2001年 | 183篇 |
2000年 | 145篇 |
1999年 | 126篇 |
1998年 | 112篇 |
1997年 | 72篇 |
1996年 | 65篇 |
1995年 | 72篇 |
1994年 | 60篇 |
1993年 | 38篇 |
1992年 | 23篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1974年 | 3篇 |
1954年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有8151条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(94):40099-40115
In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships. 相似文献
2.
The effect of the emergency perception of bystanders of cyberbullying victims on helping behaviors is often neglected in research on cyberbullying. In this study, we explored the influence of this cognitive factor on cyber-bystanders’ helping tendencies as well as elucidated possible underlying processes. The results of two studies were reported. In Study 1, 150 undergraduates read a true case of a girl experiencing cyberbullying. The results indicated that when the participants perceived the victim’s situation to be more critical (i.e., higher emergency perception), their helping tendencies were stronger, partly through increased state empathy followed by feelings of responsibility to help. In Study 2, we randomly assigned 300 undergraduates to two groups. The low emergency group read the same cyberbullying case as Study 1, whereas the cyberbullying case read by the high emergency group contained additional emergency information of the victim. The results indicated that the high emergency group expressed stronger helping tendencies than did the low emergency group. This effect was caused by a stronger perception that the victim was in an emergency situation, which not only strengthened the participants’ helping tendencies directly but also indirectly through increasing their state empathy and feelings of responsibility to help. 相似文献
4.
In this paper, we proposed a robust discrete-time controller. This control system, which is derived from the idea of the normalized plant, does not include plant parameters. Thus, we obtain a control system independent of plant parameters and that has the same structure as a conventional optimal servo control system. Simulation and experimental results show that the proposed method is fairly robust to plant parameter variations and external disturbances. 相似文献
5.
对爆炸效应在淤泥软基工程中的应用问题进行了探讨,并首次提出了爆炸在淤泥软基中的分界应力特征以及排水固结及破坏分区的基本模式。为采用动力加速对淤泥软基工程的处理,提供了试验依据,具有实用价值和指导意义。 相似文献
6.
本文基于矩阵方程解,提出了一种开环稳定系统反馈的设计方法,所设计的系统对任意传感器失效具有完整性。 相似文献
7.
8.
The Florida Department of Transportation (FDOT) is in the process of implementing Pontis, a Bridge Management System, to provide decision support to engineers in the headquarters and district offices as they make routine policy, programming, and budgeting decisions regarding the preservation and improvement of the state’s bridges. As part of this effort, an ongoing research program is underway to adapt the system to FDOT needs as well as to advance the state of the art in several areas important to the Department. Most of the research results are organized around a new project-level decision support framework that complements and builds on Pontis’ existing network-level analysis. Specific new models include accident risk and user cost due to roadway width and alignment deficiencies; user cost of load capacity and vertical clearance restrictions, and moveable bridge openings; project-level prediction models for bridge element condition and costs; and prediction of economics of scale and scoping possibilities. The new models are built into a highly graphical spreadsheet model for decision support use. 相似文献
9.
This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
10.
E. N. Aleksandrov 《Combustion, Explosion, and Shock Waves》2006,42(2):131-139
An analysis of papers on hydrogen combustion at low pressures is performed, which refines the contribution of the catalytic
reactions on the reactor wall to the gas-phase part of the process. A new model for the heterogeneous loss of active reaction
centers was proposed and tested experimentally to explain inconsistencies that occur in some papers. In this model, the diffusion
region of chain termination is formed under standard experimental conditions in vacuum oxyhydrogen flames at a reactor gas
pressure a thousand times lower than the boundary pressure postulated by the previous models as the pressure below which the
diffusion region of chain termination cannot be formed.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 10–18, March–April, 2006. 相似文献