全文获取类型
收费全文 | 2404篇 |
免费 | 264篇 |
国内免费 | 102篇 |
专业分类
电工技术 | 86篇 |
综合类 | 320篇 |
化学工业 | 153篇 |
金属工艺 | 156篇 |
机械仪表 | 537篇 |
建筑科学 | 264篇 |
矿业工程 | 67篇 |
能源动力 | 69篇 |
轻工业 | 62篇 |
水利工程 | 49篇 |
石油天然气 | 51篇 |
武器工业 | 57篇 |
无线电 | 158篇 |
一般工业技术 | 526篇 |
冶金工业 | 31篇 |
原子能技术 | 38篇 |
自动化技术 | 146篇 |
出版年
2024年 | 10篇 |
2023年 | 28篇 |
2022年 | 55篇 |
2021年 | 60篇 |
2020年 | 76篇 |
2019年 | 67篇 |
2018年 | 65篇 |
2017年 | 70篇 |
2016年 | 84篇 |
2015年 | 102篇 |
2014年 | 147篇 |
2013年 | 162篇 |
2012年 | 196篇 |
2011年 | 170篇 |
2010年 | 129篇 |
2009年 | 135篇 |
2008年 | 99篇 |
2007年 | 151篇 |
2006年 | 145篇 |
2005年 | 114篇 |
2004年 | 101篇 |
2003年 | 96篇 |
2002年 | 71篇 |
2001年 | 59篇 |
2000年 | 56篇 |
1999年 | 50篇 |
1998年 | 48篇 |
1997年 | 39篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1992年 | 21篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2770条查询结果,搜索用时 15 毫秒
41.
The article is concerned with the analysis of panel flutter of heated circular clamped cylindrical shells made of functionally graded (FG) material, which are subject to a simultaneous action of the external supersonic gas flow and the internal flow of ideal compressible fluid. The effective properties of the material change throughout the thickness of the shell according to a power law and depend on temperature. The aerodynamic pressure is calculated based on the quasi-static aerodynamic theory. The behavior of the fluid is described in the framework of the potential theory. A mathematical formulation of the dynamic problem for elastic structure is developed based on the classical theory of shells and the principle of virtual displacements. Based on the results of numerical simulation the influence of different consistencies of the examined FG materials, thermal load, and internal flow velocity on the boundary of aeroelastic stability is analyzed. 相似文献
42.
In this paper, the axial-flux permanent magnet driver is modeled and analyzed in a simple and novel way under three-dimensional cylindrical coordinates. The inherent three-dimensional characteristics of the device are comprehensively considered, and the governing equations are solved by simplifying the boundary conditions. The axial magnetization of the sector-shaped permanent magnets is accurately described in an algebraic form by the parameters, which makes the physical meaning more explicit than the purely mathematical expression in general series forms. The parameters of the Bessel function are determined simply and the magnetic field distribution of permanent magnets and the air-gap is solved. Furthermore, the field solutions are completely analytical, which provides convenience and satisfactory accuracy for modeling a series of electromagnetic performance parameters, such as the axial electromagnetic force density, axial electromagnetic force, and electromagnetic torque. The correctness and accuracy of the analytical models are fully verified by three-dimensional finite element simulations and a 15 kW prototype and the results of calculations, simulations, and experiments under three methods are highly consistent. The influence of several design parameters on magnetic field distribution and performance is studied and discussed. The results indicate that the modeling method proposed in this paper can calculate the magnetic field distribution and performance accurately and rapidly, which affords an important reference for the design and optimization of axial-flux permanent magnet drivers. 相似文献
43.
电机三维温度场新的有限元计算模型 总被引:13,自引:6,他引:7
提出了一种新的适合于电机温度场计算的圆柱坐标系下的有限元模型。通过数值计算结果与解析计算结果的实例对比,证明了本方法的正确性与有效性。最后应用本文提出的模型,对SF125-96/1560型发电机的定子铁芯三维温度场进行了计算,并与实测结果作了比较,计算精度满足工程计算的要求。 相似文献
44.
A dual‐polarized X‐band conformal array antenna is presented for unmanned aerial vehicles with polarimetric radars/sensors. Starting from the planar structure, the array antenna consisted of sixteen 2 × 2 subarrays is conformal to the cylinders with various curvature radii to fit the payload box of the airborne vehicle. The return losses are almost constant even if the curvature radius changes. Measured radiation patterns are compared with various curvatures at the same frequencies. The array can be easily placed on the aircraft payload or fuselage due to its ultra thin thickness, ultra lightweight, and conformal structure, which has potential airborne applications in polarimetric radar surveillance, remote sensing, and wireless communications. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. 相似文献
45.
针对常用的矿仓物位测量方式受粉尘和堆矿死角因素的影响而存在矿仓物位测量不准确的问题,提出了一种新型的矿仓物位测量方案。该方案选择重锤物位计消除粉尘干扰、采用多点布局求取均值的方法消除堆矿死角干扰。实际应用表明,该方案解决了粉尘和堆矿死角对物位测量的影响,降低了矿仓岗位人员的劳动强度。 相似文献
46.
Tri‐band composite cylindrical dielectric resonator antenna with hybrid mode excitation and cross‐polarization suppression
下载免费PDF全文
![点击此处可从《国际射频与微波计算机辅助工程杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This communication investigates composite cylindrical dielectric resonator antenna (CDRA) for various wireless applications. Three important features of proposed antenna design are (i) realization of two different hybrid modes, that is, HEM11δ and HEM12δ mode in CDRA with the help of modified annular ring printed line (work as both magnetic dipole and electric dipole), both the hybrid modes support broadside radiation characteristics (ii) suppression of HEM21δ mode, in order to reduce the cross‐polarization level in H‐plane of other hybrid modes (HEM11δ and HEM12δ mode) by an amount of 8‐10 dB (iii) creation of triple‐band attribute using the concept of composite antenna. The proposed antenna design has been fabricated and practically tested. Simulated outcomes show good agreement with measured outcomes. It works in three frequency bands, that is, 2.25‐2.79 GHz, 3.1‐4.0 GHz, and 5.05‐5.6 GHz. The designed antenna structure is appropriate for WLAN and WiMAX applications. 相似文献
47.
为了使基于投影的真三维显示获得径向均匀亮度,并提高有效体素数量,提出一种体素化和均匀化方法.针对体素中轴亮度高和外围亮度低的问题,分析了现有体素采样方法导致体素数量损失过多的原因;然后以二维平面填充算法替代三维体素采样,提出基于径向范围填充的体素化方法,以及基于抖动技术的均匀化方法,以修正了柱空间内体素亮度失真.实验结果证明,文中方法保留了约60%的体显示分辨率,有效体素数量达到2亿个,真三维显示样机能够在室内光环境下显示清晰且均匀的全角度立体影像. 相似文献
48.
49.
50.
套缸式高空作业车摆臂机构机构综合分析 总被引:2,自引:0,他引:2
为选择机构的合理结构形式、运动副类型、数目及合理的尺寸搭配,对一种高空作业车摆臂机构进行分析.在已知连杆铰接点的起始位置、连架杆的对应转角及机架长度的平面综合连杆机构的各设计变量间关系的条件下,根据给定的运动学或动力学要求,进行了机构综合.对六杆运动链连杆类配方案进行选择,组合生成六连杆4种形式,在此基础上再生运动链,形成新的机构形式,给出机构多种可能的构型,完成摆臂机构的型综合.对不同方案进行比较,得出了满足运动学及动力学要求的最优解. 相似文献