全文获取类型
收费全文 | 1096篇 |
免费 | 200篇 |
国内免费 | 73篇 |
专业分类
电工技术 | 31篇 |
综合类 | 111篇 |
化学工业 | 74篇 |
金属工艺 | 26篇 |
机械仪表 | 88篇 |
建筑科学 | 68篇 |
矿业工程 | 6篇 |
能源动力 | 11篇 |
轻工业 | 30篇 |
水利工程 | 38篇 |
石油天然气 | 20篇 |
武器工业 | 6篇 |
无线电 | 323篇 |
一般工业技术 | 174篇 |
冶金工业 | 18篇 |
原子能技术 | 5篇 |
自动化技术 | 340篇 |
出版年
2024年 | 1篇 |
2023年 | 32篇 |
2022年 | 26篇 |
2021年 | 33篇 |
2020年 | 56篇 |
2019年 | 64篇 |
2018年 | 45篇 |
2017年 | 62篇 |
2016年 | 47篇 |
2015年 | 67篇 |
2014年 | 74篇 |
2013年 | 81篇 |
2012年 | 84篇 |
2011年 | 76篇 |
2010年 | 70篇 |
2009年 | 49篇 |
2008年 | 51篇 |
2007年 | 79篇 |
2006年 | 59篇 |
2005年 | 45篇 |
2004年 | 57篇 |
2003年 | 40篇 |
2002年 | 36篇 |
2001年 | 25篇 |
2000年 | 13篇 |
1999年 | 23篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1369条查询结果,搜索用时 15 毫秒
1.
Yuping Ji Kaixin Song Shiyu Zhang Zhilun Lu Ge Wang Linhao Li Di Zhou Dawei Wang Ian M. Reaney 《Journal of the European Ceramic Society》2021,41(1):424-429
Dense (1-x)wt%CaSnSiO5-xwt%K2MoO4 (CSSO-KMO) composite ceramics were fabricated by the cold sintering process at 180 °C under 400 MPa for 60 min. X-ray diffraction, Energy dispersive X-ray and Raman spectroscopy confirmed that CSSO and KMO coexisted without intermediate phases. As KMO weight fraction increased, relative permittivity (εr) and temperature coefficient of resonant frequency (τf) decreased and the microwave quality factor (Q×f, where f is resonant frequency) increased. Near-zero τf (-0.5 ppm/°C) was obtained for 65 wt%CSSO-35 wt%KMO with εr ~ 9.2 and Q×f ~ 6240 GHz. No chemical reaction between ceramic composites and silver was observed, demonstrating potential for cofiring with Ag-paste. A prototype antenna was fabricated from 65 wt%CSSO-35 wt%KMO composite ceramic with a bandwidth of 144 MHz @ -10 dB, a gain of 5.7 dBi and a total efficiency of 88.4 % at 5.2 GHz, suitable for 5 G mobile communication systems. 相似文献
2.
An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic. 相似文献
3.
In this paper, a compact asymmetric coplanar waveguide (CPW) feed with split-ring resonator (SRR) is proposed to resonate at dual-band operations for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The asymmetric CPW-fed SRR patch (ACSP) antenna consists of a meander line, square-shaped split ring, and CPW ground plane. The proposed ACSP antenna resonates at two operating frequencies, namely, 2.48 GHz (2.4–2.74 GHz) and 3.49 GHz (3.25–3.64 GHz) with reflection coefficients (S11) of −16.65 dB and −32.67 dB, respectively. The measured results agree closely with the simulation results of the proposed antenna. 相似文献
4.
5.
6.
Ramaprasad Srinivasan B. Dattaguru Gajbir Singh 《International Journal for Computational Methods in Engineering Science and Mechanics》2021,22(1):60-80
Abstract An efficient 4-noded membrane element tolerant and insensitive to mesh distortion is developed using kinematically coupling the in-plane displacements which satisfy the equilibrium equations in Cartesian coordinates and results in material-dependent coupled field interpolation functions making the element free from volumetric and shear locking. The proposed formulation provides a preliminary concept for the satisfaction of natural boundary conditions which is used to satisfy the strong patch test. The proposed element, passed several benchmark problems from the literature, compared well with elasticity solutions, passed the weak patch test and the inf-sup test for both compressible and incompressible cases. 相似文献
7.
通过对巴嘎榨岛状多年冻土的成因分析,并结合钻探,物探,测温等综合勘探的技术,查明了该段多年冻土的工程地质条件,为铁路设计和施工提供了科学依据。 相似文献
8.
9.
10.
本文首次以福州市建成区为研究范围,综合利用G IS、遥感数据和实测调绘数据,构建了高精度城市绿地斑块数据库,采用景观生态学的研究方法,分析福州市城市绿地的景观现状格局以及与城市建设、人居环境等之间的关系,并对城市绿地规划和建设提出了一些建议。 相似文献