全文获取类型
收费全文 | 8588篇 |
免费 | 1148篇 |
国内免费 | 589篇 |
专业分类
电工技术 | 1237篇 |
技术理论 | 2篇 |
综合类 | 916篇 |
化学工业 | 585篇 |
金属工艺 | 279篇 |
机械仪表 | 565篇 |
建筑科学 | 438篇 |
矿业工程 | 259篇 |
能源动力 | 352篇 |
轻工业 | 157篇 |
水利工程 | 349篇 |
石油天然气 | 248篇 |
武器工业 | 318篇 |
无线电 | 2182篇 |
一般工业技术 | 652篇 |
冶金工业 | 234篇 |
原子能技术 | 295篇 |
自动化技术 | 1257篇 |
出版年
2024年 | 37篇 |
2023年 | 119篇 |
2022年 | 239篇 |
2021年 | 303篇 |
2020年 | 306篇 |
2019年 | 260篇 |
2018年 | 228篇 |
2017年 | 339篇 |
2016年 | 382篇 |
2015年 | 453篇 |
2014年 | 579篇 |
2013年 | 657篇 |
2012年 | 623篇 |
2011年 | 646篇 |
2010年 | 520篇 |
2009年 | 522篇 |
2008年 | 447篇 |
2007年 | 610篇 |
2006年 | 497篇 |
2005年 | 393篇 |
2004年 | 344篇 |
2003年 | 290篇 |
2002年 | 244篇 |
2001年 | 236篇 |
2000年 | 184篇 |
1999年 | 161篇 |
1998年 | 118篇 |
1997年 | 105篇 |
1996年 | 84篇 |
1995年 | 84篇 |
1994年 | 55篇 |
1993年 | 47篇 |
1992年 | 45篇 |
1991年 | 33篇 |
1990年 | 33篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1957年 | 2篇 |
1955年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(91):38682-38689
A body-centered cubic equiatomic TiZrTaNbAl multi-principal element alloy (MPEA) with elemental fluctuations was investigated to further understand the relationship between the microstructure and hydrogen distribution. In this study, a composition dependence of the hydrogen distribution was observed in the TiZrTaNbAl MPEA. An inhomogeneous electron density distribution of the MPEA was revealed by advanced differential phase-contrast scanning electron microscopy (DPC-STEM) for the first time. The results showed that the electron density has a significant effect on the hydrogen distribution in TiZrTaNbAl MPEAs. This work provides new insight into the design of materials with high hydrogen storage capacity and high hydrogen embrittlement resistance. 相似文献
2.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
3.
4.
Very high resolution inverse synthetic aperture radar (ISAR) imaging of fast rotating targets is a complicated task. There may be insufficient pulses or may introduce migration through range cells (MTRC) during the coherent processing interval (CPI) when we use the conventional range Doppler (RD) ISAR technique. With compressed sensing (CS) technique, we can achieve the high-resolution ISAR imaging of a target with limited number of pulses. Sparse representation based method can achieve the super resolution ISAR imaging of a target with a short CPI, during which the target rotates only a small angle and the range migration of the scatterers is small. However, traditional CS-based ISAR imaging method generally faced with the problem of basis mismatch, which may degrade the ISAR image. To achieve the high resolution ISAR imaging of fast rotating targets, this paper proposed a pattern-coupled sparse Bayesian learning method for multiple measurement vectors, i.e. the PC-MSBL algorithm. A multi-channel pattern-coupled hierarchical Gaussian prior is proposed to model the pattern dependencies among neighboring range cells and correct the MTRC problem. The expectation-maximization (EM) algorithm is used to infer the maximum a posterior (MAP) estimate of the hyperparameters. Simulation results validate the effectiveness and superiority of the proposed algorithm. 相似文献
5.
Madhab Chandra Tripathy Debasmita Mondal Karabi Biswas Siddhartha Sen 《International Journal of Circuit Theory and Applications》2015,43(6):776-792
The present work reports the realization of an analog fractional‐order phase‐locked loop (FPLL) using a fractional capacitor. The expressions for bandwidth, capture range, and lock range of the FPLL have been derived analytically and then compared with the experimental observations using LM565 IC. It has been observed that bandwidth and capture range can be extended by using FPLL. It has also been found that FPLL can provide faster response and lower phase error at the time of switching compared to its integer‐order counterpart. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape. 相似文献
7.
墙体裂缝的成因及防治 总被引:2,自引:2,他引:0
介绍了墙体裂缝的种类,从地基不均匀下沉、温度变化等方面分析了引起墙体裂缝的原因,介绍了墙体裂缝的预防措施和治理措施,以有效控制墙体裂缝的危害程度。 相似文献
8.
连续波半主动雷达制导空空导弹截获跟踪距离计算 总被引:1,自引:1,他引:0
分析了连续波半主动雷达制导导弹导引头工作电磁环境和对武器系统攻击区的影响,建立了热噪声和杂波干扰环境下导引头截获距离方程,分析推导了直波泄漏干扰,地杂波干扰的计算公式,并在此基础上给出了导弹允许攻击区计算公式。 相似文献
9.
10.