全文获取类型
收费全文 | 4253篇 |
免费 | 547篇 |
国内免费 | 355篇 |
专业分类
电工技术 | 334篇 |
综合类 | 312篇 |
化学工业 | 788篇 |
金属工艺 | 134篇 |
机械仪表 | 100篇 |
建筑科学 | 427篇 |
矿业工程 | 513篇 |
能源动力 | 182篇 |
轻工业 | 175篇 |
水利工程 | 74篇 |
石油天然气 | 182篇 |
武器工业 | 663篇 |
无线电 | 57篇 |
一般工业技术 | 790篇 |
冶金工业 | 136篇 |
原子能技术 | 99篇 |
自动化技术 | 189篇 |
出版年
2024年 | 7篇 |
2023年 | 39篇 |
2022年 | 191篇 |
2021年 | 128篇 |
2020年 | 112篇 |
2019年 | 86篇 |
2018年 | 70篇 |
2017年 | 159篇 |
2016年 | 148篇 |
2015年 | 150篇 |
2014年 | 285篇 |
2013年 | 279篇 |
2012年 | 349篇 |
2011年 | 379篇 |
2010年 | 326篇 |
2009年 | 296篇 |
2008年 | 235篇 |
2007年 | 317篇 |
2006年 | 299篇 |
2005年 | 252篇 |
2004年 | 195篇 |
2003年 | 185篇 |
2002年 | 135篇 |
2001年 | 121篇 |
2000年 | 75篇 |
1999年 | 83篇 |
1998年 | 55篇 |
1997年 | 32篇 |
1996年 | 35篇 |
1995年 | 36篇 |
1994年 | 33篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1979年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有5155条查询结果,搜索用时 359 毫秒
61.
In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentration and geometry. Flame and pressure transducers were used to track the explosion front velocity. The flame speed (Sf) showed a slight downward trend while the methane concentration varied from 10% to 3% in the experimental channel. The peak overpressure (Pmax) dropped dramatically when com-pared with normal conditions. As well, the values of Pmax and Sf decreased when the methane concentration dropped from 8% to 6%. The flame speed in the channel, connected to a cylinder with a length varying from 0.5 to 2 m, was greater than that in the normal channel. The peak overpressure was also higher than that under normal conditions because of a higher flame speed and stronger pressure piling up. The values of Pmax and Sf increased with an increase in cylinder length. The research results indicate that damage caused by explosions can be reduced by decreasing the gas concentration, which should be immediately detected in roadways with large cross-sections because of the possibility of greater destruction caused by more serious explosions. 相似文献
62.
为了研究冲击爆炸作用下舰船防护结构的破坏情况,将该结构简化为多层板架结构,借助于有限元程序LS-DYNA中的ALE算法,同时考虑穿甲和爆炸的作用,对其在穿甲后爆炸荷载作用下的非线性动态响应过程进行仿真分析,描述了钢板的破口形状、破口半径及板上单元等效应力随时间变化的情况,并与舷外接触爆炸对结构的破坏情况进行比较.结果表明穿甲后爆炸能对舰体内部造成破坏,因此它是一种比较理想的反舰攻击方式. 相似文献
63.
Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit (LEL) and Upper Explosion-Limit (UEL) of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of H2 increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines. 相似文献
64.
王秀丽 《安徽建筑工业学院学报》2009,17(1)
爆炸是引起建筑物连续性倒塌的主要原因.由于爆炸事件的频繁发生,对爆炸荷载下建筑结构的反应和破坏模式的研究已经成为热点.过去几十年很多学者对爆炸荷载下建筑结构及其构件的反应和破坏模式进行了研究.本文以大量系统的文献为依据,综合分析了爆炸荷载的特点,框架结构对爆炸荷载的反应,及其结构构件在爆炸荷载下的破坏模式.为以后建筑结构的设计提供了一定的依据. 相似文献
65.
66.
Methane absorption and application of mixed organic aggregate prepared from Span80 and alkaline salt
The water-based materials for mine gas absorption and explosion suppression were prepared, in which the mixed organic aggregate
of Span80 and alkaline salt can be used as methane absorbent. Methane was used as a model of mine gas, and the absorptions
of methane with different complex materials were studied using head space gas chromatography. Then the state of aqueous material
was characterized with laser light scattering instrument and the effects of different complex materials on explosion suppression
were preliminarily studied in explosion chamber which can simulate mine gas explosion. The research results showed that complex
material could absorb methane and there was some correlation between the mean diameter of organic aggregate in aqueous material
and the absorption effect. Additionally, the aqueous material could suppress the methane explosion to some degree. The material
can absorb mine gas in atomization condition, therefore, degrease mine gas concentration and influence the distribution of
mine gas in the space, and then suppress the mine gas explosion to some extent. 相似文献
67.
The L, H and C curves in P-T phase are proposed to describe the minimal, maximal and critical characteristics of ignition time of H2/O2 combustion system, respectively. The features of H2/O2(Air) combustion system, including explosion or not as well as the time delay to achieve its explosion status, can be well
shown by explosion limits and these proposed curves. These curves can be described by 1.2k
1=k
s
[Ms], (k
11/k
10+1)k
1=k
s
[Ms], and 2k
1=k
s
[Ms], respectively, which provide a physical explanation for these curves and give another way to establish them. Based on the
contour of ignition time, the Z-type explosion limits can be explained by thermal explosion theory. Furthermore, the ignition
distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system, which is very
reasonable. 相似文献
68.
电热爆炸喷涂法制备TiC涂层的特性分析 总被引:1,自引:0,他引:1
采用电热爆炸定向喷涂工艺在镍合金基体上制备TiC涂层,借助光学显微镜、显微硬度计分别对涂层显微组织、涂层硬度进行了测试。利用图像分析软件对涂层的晶粒尺寸进行了测量。结果表明,电热爆炸定向喷涂制备的涂层组织晶粒明显细化,涂层组织为典型的快速凝固组织。涂层组织比原始喷涂材料镍合金组织细小、均匀;TiC涂层中大晶粒所占涂层面积为93.6%,小晶粒所占面积为6.4%;大晶粒的弦长平均值为500 nm左右,小晶粒的弦长平均值为81 nm左右;表层有些孔隙;涂层硬度均明显高于基体材料镍合金的硬度,其最高硬度达到了582.5 HV。 相似文献
69.
采用20L球形爆炸装置研究了煤尘粒径、浓度、点火能量对煤尘爆炸最大压力、爆炸最大压力上升速率的影响。研究结果表明,在煤尘粒径一定的条件下,随着煤尘浓度的增大,爆炸最大压力及爆炸最大压力上升速率先增大后减小,煤尘浓度在400~480g/m3之间取得爆炸最大压力最大值0.94MPa、爆炸最大压力上升速率最大值28.79MPa/s;在煤尘浓度一定的条件下,爆炸最大压力不随煤尘粒径的减小而单调变化,爆炸最大压力上升速率随煤尘粒径的减小而逐渐增大;随着点火能量的增大,爆炸最大压力及爆炸最大压力上升速率明显增加。 相似文献
70.