全文获取类型
收费全文 | 24381篇 |
免费 | 3341篇 |
国内免费 | 1904篇 |
专业分类
电工技术 | 2915篇 |
综合类 | 3145篇 |
化学工业 | 1483篇 |
金属工艺 | 1060篇 |
机械仪表 | 1973篇 |
建筑科学 | 2601篇 |
矿业工程 | 1115篇 |
能源动力 | 942篇 |
轻工业 | 1354篇 |
水利工程 | 848篇 |
石油天然气 | 1360篇 |
武器工业 | 472篇 |
无线电 | 2584篇 |
一般工业技术 | 2114篇 |
冶金工业 | 766篇 |
原子能技术 | 311篇 |
自动化技术 | 4583篇 |
出版年
2024年 | 60篇 |
2023年 | 376篇 |
2022年 | 752篇 |
2021年 | 859篇 |
2020年 | 852篇 |
2019年 | 750篇 |
2018年 | 689篇 |
2017年 | 893篇 |
2016年 | 916篇 |
2015年 | 1039篇 |
2014年 | 1471篇 |
2013年 | 1365篇 |
2012年 | 1808篇 |
2011年 | 2013篇 |
2010年 | 1539篇 |
2009年 | 1656篇 |
2008年 | 1608篇 |
2007年 | 1975篇 |
2006年 | 1692篇 |
2005年 | 1357篇 |
2004年 | 1088篇 |
2003年 | 912篇 |
2002年 | 696篇 |
2001年 | 622篇 |
2000年 | 545篇 |
1999年 | 385篇 |
1998年 | 324篇 |
1997年 | 294篇 |
1996年 | 211篇 |
1995年 | 204篇 |
1994年 | 152篇 |
1993年 | 114篇 |
1992年 | 110篇 |
1991年 | 81篇 |
1990年 | 46篇 |
1989年 | 52篇 |
1988年 | 40篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 12篇 |
1976年 | 2篇 |
1959年 | 7篇 |
1957年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath. In this paper, the phase shift characteristics of electromagnetic wave propagation in plasma were investigated. Firstly, the impact factors of phase shift including electron density,collision frequency and incident frequency were discussed. Then, the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics. In a real case, the plasma sheath around the hypersonic vehicle will affect and even break down the communication. Based on the hypersonic vehicle model, we studied the electromagnetic wave phase shift under different flight altitude, speed, and attack angle. The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle. Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma. 相似文献
3.
《Ceramics International》2022,48(20):29601-29613
Sliding wear behaviors of atmospheric plasma-sprayed Yttria Stabilized Zirconia (YSZ) coating mated with four metallic or ceramic counterparts (Si3N4, Al2O3, GCr15 and ZrO2) were investigated. It has been found that YSZ coatings in contact with Si3N4 and GCr15 show better tribological performances than the other cases, which is due to the formation of the tribolayer mainly consisting of Si3N4 and Fe2O3 respectively on the worn surfaces. In the case of YSZ coating-Al2O3 and YSZ coating-ZrO2 tribopairs, the wear debris are more irregular and larger in size, resulting in severe abrasive wear and brittle fracture of debris particles. In particular, the specific wear rate of YSZ coating sliding against GCr15 is negative due to the significant material transfer of the tribo-oxide layer, while that of YSZ coating sliding against ZrO2 is the highest. Amorphization of the wear particles appears in the four cases due to the repeated mechanical action. It has been demonstrated that the wear of YSZ coating deteriorates with the increased flash temperature between the contact surfaces during rubbing process. 相似文献
4.
5.
针对在传统的客户流失预测数据预处理中,使用one-hot编码处理离散属性导致数据维度增加及数据过于稀疏的问题,提出了两种基于多层感知机的改进后的客户流失预测模型。其主要思想是分别使用堆叠自编码器和实体嵌入两种方法对多层感知机进行改进,通过将离散属性的高维编码数据向低维空间映射,有效地减少了one-hot编码产生的稀疏数据,增加了离散属性值之间的关联度。在对两份公开的数据集进行交叉验证后的实验结果表明,改进后的模型既有效地提高了预测的准确度,又维持了传统多层感知机模型在并行化计算方面的优势。 相似文献
6.
LUO Jin-ling LIU Luo-ren 《广东电脑与电讯》2020,1(4):11-13
In view of the problems in the construction of characteristic professional groups in higher vocational colleges, the professional group of "intelligent manufacturing" is taken as the research object, and the "platform + module" suitable for the development
of the industry will be constructed according to the content of the vocational ability planning courses of the post group. The curriculum system establishes the framework of professional groups, and explores and forms a strategic study to optimize and integrate professional group resources. 相似文献
7.
E. Nahvifard 《Journal of Modern Optics》2020,67(6):475-480
ABSTRACTIn this paper, we study detection of the state non-classicality for a quantum harmonic oscillator by a qubit in the presence of dissipation effects. We show that dissipation can enhance the effectiveness of the method in case of using the corrected form of the related nonclassicality witness. Such an improvement is attributed to the fact that dissipation leads to probing a surface, instead of a curve, of the complex plane for non-classicality condition on normally-ordered characteristic function. 相似文献
8.
利用Gleeble-3500热模拟试验机研究了低活化马氏体钢在变形温度为850~950 ℃、应变速率为0.001~1 s-1条件下的热变形行为。建立了流变应力本构方程,并评估了该方程的预测能力。绘制了低活化马氏体钢在不同应变下的热加工图。结果表明:在较高的应变速率条件下,该材料主要发生动态回复,在较高变形温度和较低应变速率下具有明显的动态再结晶特征;本构方程的预测结果与实验结果符合良好;变形温度870~930 ℃、应变速率0.001~0.01 s-1和变形温度920~950 ℃、应变速率0.3~1 s-1分别是真应变为0.4和0.6下最优的热加工区域。 相似文献
9.
10.
结合翼型泛函集成理论与叶片截面刚度矩阵数学计算模型,提出了风力机中等厚度翼型气动性能与结构刚度特性的一体化设计方法,实现了翼型气动性能与叶片截面刚度特性的同时提高。对考虑叶片截面铺层参数变化设计的WQ-B300翼型与DU97-W-300翼型进行了气动性能与结构刚度特性对比分析,结果表明:相比于DU97-W-300翼型,WQ-B300翼型的气动性能与叶片截面刚度性能均有显著提高,其挥舞刚度和摆振刚度分别提高了6.2%和8.4%,验证了该设计方法的可行性,给风力机中等厚度及大厚度翼型设计提供了一种思路。 相似文献