全文获取类型
收费全文 | 16586篇 |
免费 | 2132篇 |
国内免费 | 1110篇 |
专业分类
电工技术 | 3744篇 |
技术理论 | 1篇 |
综合类 | 1446篇 |
化学工业 | 912篇 |
金属工艺 | 596篇 |
机械仪表 | 1204篇 |
建筑科学 | 1906篇 |
矿业工程 | 798篇 |
能源动力 | 577篇 |
轻工业 | 218篇 |
水利工程 | 462篇 |
石油天然气 | 702篇 |
武器工业 | 168篇 |
无线电 | 2325篇 |
一般工业技术 | 852篇 |
冶金工业 | 502篇 |
原子能技术 | 150篇 |
自动化技术 | 3265篇 |
出版年
2024年 | 91篇 |
2023年 | 214篇 |
2022年 | 436篇 |
2021年 | 562篇 |
2020年 | 617篇 |
2019年 | 437篇 |
2018年 | 424篇 |
2017年 | 600篇 |
2016年 | 600篇 |
2015年 | 744篇 |
2014年 | 1245篇 |
2013年 | 1158篇 |
2012年 | 1457篇 |
2011年 | 1440篇 |
2010年 | 1140篇 |
2009年 | 1115篇 |
2008年 | 1066篇 |
2007年 | 1273篇 |
2006年 | 1023篇 |
2005年 | 861篇 |
2004年 | 698篇 |
2003年 | 579篇 |
2002年 | 441篇 |
2001年 | 370篇 |
2000年 | 289篇 |
1999年 | 221篇 |
1998年 | 169篇 |
1997年 | 110篇 |
1996年 | 87篇 |
1995年 | 66篇 |
1994年 | 60篇 |
1993年 | 45篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 27篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
51.
应用独立分量分析(ICA)方法对海底管道缺陷漏磁法检测中电磁干扰的消除进行了研究,阐述了漏磁检测和负熵法ICA快速算法的原理,应用相应的分析工具研究了试验数据。结果表明,在试验室条件下该方法能很好地分离出缺陷信号和电磁干扰信号。 相似文献
52.
53.
针对配电网发生单相接地故障且分布式电源(distributed generations, DGs)大量接入后,配电网结构和运行方式复杂多变、故障后电气量不明显、故障特征弱等特点,提出一种基于改进局部均值分解(improved local mean decomposition, ILMD)和能量相对熵的主动配电网故障定位方法。首先,利用镜像延拓将信号在两端延拓,消除LMD存在的端点效应,同时,在信号中加入自适应噪声,克服LMD存在的模态混叠问题,对各区段暂态零序电流进行ILMD分解;然后对分解后所有乘积函数(product function, PF)的能量相对熵进行计算,所有PF分量的相对能量熵之和即为区段间的相对能量熵,通过所设置的定位判据,对故障区段进行判断。仿真结果表明,所提算法在10 kV小电流接地系统和改进的IEEE33节点系统中,在不同的仿真条件下故障定位结果准确率高,验证了所提方法的准确性。 相似文献
54.
55.
Experiment and simulation study of 3D magnetic field sensing for magnetic flux leakage defect characterisation 总被引:1,自引:0,他引:1
Magnetic flux leakage (MFL) testing is widely used to detect and characterise defects in pipelines, rail tracks and other structures. The measurement of the two field components perpendicular to the test surface and parallel to the applied field in MFL systems is well established. However, it is rarely effective when the shapes of the specimens and defects with respect to the applied field are arbitrary. In order to overcome the pitfalls of traditional MFL measurement, measurement of the three-dimensional (3D) magnetic field is proposed. The study is undertaken using extensive finite element analysis (FEA) focussing on the 3D distribution of magnetic fields for defect characterisation and employing a high sensitivity 3-axis magnetic field sensor in experimental study. Several MFL tests were undertaken on steel samples, including a section of rail track. The experimental and FEA test results show that data from not only the x- and z-axes but also y-axis can give comprehensive positional information about defects in terms of shape and orientation, being especially advantageous where the defect is aligned close to parallel to the applied field. The work concludes that 3D magnetic field sensing could be used to improve the defect characterisation capabilities of existing MFL systems, especially where defects have irregular geometries. 相似文献
56.
57.
电除尘器绝缘子的设计与选择 总被引:1,自引:0,他引:1
根据电除尘器绝缘子的功能、工况条件等特点,分别从材质、外形尺寸等方面介绍了设计和选择的注意事项。为用户合理地选择电除尘器绝缘子提供了帮助。 相似文献
58.
介绍自密封阀的密封原理及其在氨汽提尿素装置中的应用,对其长期运行中出现的泄漏及泄漏原因进行分析,根据不同的泄漏方式分别提出了现场维修的方法. 相似文献
59.
The vector form of the Ergun equation was used to numerically predict gas phase streamlines, residence time distributions, chemical conversions and pressure drops in the annulus of a side-outlet spouted bed with an internal draft tube. By varying the position of the side-outlet, it was demonstrated that there exists an optimum location for this outlet at which conversion is a maximum and which shows a greatly improved gas phase residence time distribution in the annulus compared with a conventional spouted bed unit. 相似文献
60.
This paper proposes a novel automatic method for the moment segmentation and peak detection analysis of heart sound (HS) pattern, with special attention to the characteristics of the envelopes of HS and considering the properties of the Hilbert transform (HT). The moment segmentation and peak location are accomplished in two steps. First, by applying the Viola integral waveform method in the time domain, the envelope (ET) of the HS signal is obtained with an emphasis on the first heart sound (S1) and the second heart sound (S2). Then, based on the characteristics of the ET and the properties of the HT of the convex and concave functions, a novel method, the short-time modified Hilbert transform (STMHT), is proposed to automatically locate the moment segmentation and peak points for the HS by the zero crossing points of the STMHT. A fast algorithm for calculating the STMHT of ET can be expressed by multiplying the ET by an equivalent window (WE). According to the range of heart beats and based on the numerical experiments and the important parameters of the STMHT, a moving window width of N = 1 s is validated for locating the moment segmentation and peak points for HS. The proposed moment segmentation and peak location procedure method is validated by sounds from Michigan HS database and sounds from clinical heart diseases, such as a ventricular septal defect (VSD), an aortic septal defect (ASD), Tetralogy of Fallot (TOF), rheumatic heart disease (RHD), and so on. As a result, for the sounds where S2 can be separated from S1, the average accuracies achieved for the peak of S1 (AP1), the peak of S2 (AP2), the moment segmentation points from S1 to S2 (AT12) and the cardiac cycle (ACC) are 98.53%, 98.31% and 98.36% and 97.37%, respectively. For the sounds where S1 cannot be separated from S2, the average accuracies achieved for the peak of S1 and S2 (AP12) and the cardiac cycle ACC are 100% and 96.69%. 相似文献