全文获取类型
收费全文 | 1353篇 |
免费 | 140篇 |
国内免费 | 91篇 |
专业分类
化学 | 114篇 |
力学 | 1155篇 |
综合类 | 2篇 |
数学 | 42篇 |
物理学 | 271篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 14篇 |
2021年 | 21篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 54篇 |
2016年 | 99篇 |
2015年 | 118篇 |
2014年 | 51篇 |
2013年 | 44篇 |
2012年 | 97篇 |
2011年 | 125篇 |
2010年 | 77篇 |
2009年 | 129篇 |
2008年 | 97篇 |
2007年 | 81篇 |
2006年 | 99篇 |
2005年 | 92篇 |
2004年 | 97篇 |
2003年 | 71篇 |
2002年 | 28篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 9篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1979年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1584条查询结果,搜索用时 31 毫秒
101.
对常温常压下柴油舱组集中透气管中柴油蒸汽的燃爆危险性以及阻隔防爆技术的抑爆效能开展了实验研究。利用nac HX-3高速相机和CY-YD-205压力传感器记录燃爆传播过程和爆炸超压,阻隔防爆装置分别采用新型抑爆小球和普通波纹型阻火器。结果表明:常温常压下,一旦柴油油舱发生爆炸,爆炸火球可以通过透气管传播到相邻油舱,并引起二次爆炸,具有较大的危险性;普通波纹型阻火器在爆炸过程中阻火失效,而新型抑爆小球具有较好的抑爆效果;相对于光滑透气管工况,在点火舱上方安装抑爆小球后,被点火舱内的最大爆炸超压可以显著地从552.5 kPa降低到35.0 kPa;抑爆小球的中空多孔结构是其阻隔防爆的关键,多孔结构不仅可以增大比表面积、扩大热损失,而且还可以有效地分割削弱反应面。 相似文献
102.
为研究柔性障碍物对甲烷空气爆炸波的激励效应,采用双向拉伸聚丙烯(biaxially oriented polypropylene, BOPP)薄膜作为柔性障碍物将管道内甲烷空气预混气体与空气隔开,对比障碍物前后火焰、激波变化,分析膜状柔性障碍物激励效应的机理。实验结果表明:这种具有一定承压能力的柔性障碍物对甲烷爆炸波产生的激励效应不可忽视,在膜片破裂前产生多次激波反射过程,可诱导湍流火焰形成,促使膜前爆炸压力提高,膜片破裂后,火焰在伴流作用下传播速度突增,并加速逐渐逼近前驱冲击波,致使膜后爆炸压力大幅提高;激励效应可使膜片前后最大爆炸压力相差5倍,火焰速度相差7倍;另外在膜片位置2.5 m后增设一道膜片,可增强这种激励效应,而增加膜片的实质是使激波火焰相互作用的次数增加。 相似文献
103.
Meiyan Fu & Tiao Lu 《高等学校计算数学学报(英文版)》2021,14(4):1110-1135
A general one-fluid cavitation model is proposed for a family of Mie-Grüneisen equations of state (EOS), which can provide a wide application of cavitation flows, such as liquid-vapour transformation and underwater explosion. An
approximate Riemann problem and its approximate solver for the general cavitation
model are developed. The approximate solver, which provides the interface pressure
and normal velocity by an iterative method, is applied in computing the numerical
flux at the phase interface for our compressible multi-medium flow simulation on
Eulerian grids. Several numerical examples, including Riemann problems and underwater explosion applications, are presented to validate the cavitation model and
the corresponding approximate solver. 相似文献
104.
Wenjie Sui Shunqin Li Xiaodan Zhou Zishan Dou Rui Liu Tao Wu Hongyu Jia Guanhua Wang Min Zhang 《Molecules (Basel, Switzerland)》2021,26(13)
In this work, steam explosion (SE) was exploited as a potential hydrothermal-humification process of vegetable wastes to deconstruct their structure and accelerate their decomposition to prepare humified substances. Results indicated that the SE process led to the removal of hemicellulose, re-condensation of lignin, degradation of the cellulosic amorphous region, and the enhancement of thermal stability of broccoli wastes, which provided transformable substrates and a thermal-acidic reaction environment for humification. After SE treatment, total humic substances (HS), humic acids (HAs), and fulvic acids (FAs) contents of broccoli samples accounted for up to 198.3 g/kg, 42.3 g/kg, and 166.6 g/kg, and their purification were also facilitated. With the increment of SE severity, structural characteristics of HAs presented the loss of aliphatic compounds, carbohydrates, and carboxylic acids and the enrichment of aromatic structures and N-containing groups. Lignin substructures were proved to be the predominant aromatic structures and gluconoxylans were the main carbohydrates associated with lignin in HAs, both of their signals were enhanced by SE. Above results suggested that SE could promote the decomposition of easily biodegradable matters and further polycondensation, aromatization, and nitrogen-fixation reactions during humification, which were conducive to the formation of HAs. 相似文献
105.
Canard explosion and internal signal stochastic bi-resonance in the CO oxidation on platinum surface
ZHAO Gang HOU Zhonghuai & XIN Houwen Department of Chemical Physics University of Science Technology of China Hefei China Correspondence should be addressed to Xin Houwen 《中国科学B辑(英文版)》2006,49(2):133-139
Canard explosion means a dramatic change fromsmall amplitude quasi-harmonic oscillation to largeamplitude relaxation oscillation, accompanied by anexponential increase of period, of a limit cycle withina very narrow interval of a control parameter. Thisphenomenon was first found in the Van Der Pol equa-tions[1], and later has been found also in chemical[2]and biological[3] systems. Generally speaking, it is theresult of multi-time scales in the system, and can bedealt with singular perturbati… 相似文献
106.
The aerial pressure wave generated by the deflagration of a truly unconfined vapour cloud is known to be composed of a positive
(overpressure) part as the flame expands, followed by a negative (underpressure) part, when the deflagration vanishes. Basically,
this second part is ignored in safety predictions. The present study proposes an empirical method estimating the amplitude
and the duration of the negative part of the wave, provided the mixture, the size of the cloud and the maximum flame velocity
be known a priori, or estimated. This method is deduced from spherical piston flow model properties and results of small scale
experiments carried out for flame spatial velocities in the range 5 to 200 m/s.
Received 4 August 1995 / Accepted 12 December 1995 相似文献
107.
108.
109.
O. K. Sommersel D. Bjerketvedt S. O. Christensen O. Krest K. Vaagsaether 《Shock Waves》2008,18(4):291-297
This paper describes application of a background oriented schlieren technique in order to obtain quantitative measurements
of shock waves from explosions by processing high speed digital video recordings. The technique is illustrated by an analysis
of two explosions, a high explosive test and a hydrogen gas explosion test. The visualization of the shock front is utilized
to calculate the shock Mach number, leading to a predicted shock front pressure. For high explosives the method agreed quite
well with a standard curve for side-on shock pressures. In the case of the gas explosion test we can also show that the shock
front is non-spherical. It should be possible to develop this technique to investigate external blast waves and external explosions
from vented gas explosions in more details.
This paper is based on work that was presented at the 21th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Poitiers, France, July 23–27, 2007. 相似文献
110.
本文概述了瓦斯煤尘爆炸火焰光谱实验研究的重要性,我们在弱爆炸和探测器小视场角的条件下,利用自己研制的多波道仪,在一端开口的Φ200cm×2900cm大型管道里,得到了CH4、空气和煤尘的混合物在不同状态下,特征波长λ等于0.8875、1.000、1.505、2.801和4.346微米(μ)的绝对辐射强度及其有关的变化规律,对结果进行了分析讨论,并与国外实验结果进行了对比,根据测量λ=4.346μ绝对辐射强度和我们选择的黑体辐射模型,获得了爆炸火焰的温度,该项研究不仅在工业中具有重要意义,而且对燃烧和化学动力学的研究也具有参考价值。 相似文献