全文获取类型
收费全文 | 16015篇 |
免费 | 2053篇 |
国内免费 | 1129篇 |
专业分类
电工技术 | 837篇 |
综合类 | 1117篇 |
化学工业 | 4963篇 |
金属工艺 | 1496篇 |
机械仪表 | 2028篇 |
建筑科学 | 285篇 |
矿业工程 | 202篇 |
能源动力 | 359篇 |
轻工业 | 245篇 |
水利工程 | 22篇 |
石油天然气 | 103篇 |
武器工业 | 264篇 |
无线电 | 2415篇 |
一般工业技术 | 2952篇 |
冶金工业 | 505篇 |
原子能技术 | 71篇 |
自动化技术 | 1333篇 |
出版年
2024年 | 85篇 |
2023年 | 424篇 |
2022年 | 485篇 |
2021年 | 570篇 |
2020年 | 664篇 |
2019年 | 593篇 |
2018年 | 582篇 |
2017年 | 686篇 |
2016年 | 650篇 |
2015年 | 630篇 |
2014年 | 797篇 |
2013年 | 825篇 |
2012年 | 923篇 |
2011年 | 1070篇 |
2010年 | 754篇 |
2009年 | 853篇 |
2008年 | 751篇 |
2007年 | 1154篇 |
2006年 | 1044篇 |
2005年 | 872篇 |
2004年 | 808篇 |
2003年 | 682篇 |
2002年 | 545篇 |
2001年 | 518篇 |
2000年 | 455篇 |
1999年 | 362篇 |
1998年 | 302篇 |
1997年 | 215篇 |
1996年 | 225篇 |
1995年 | 173篇 |
1994年 | 154篇 |
1993年 | 106篇 |
1992年 | 88篇 |
1991年 | 46篇 |
1990年 | 30篇 |
1989年 | 29篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper presents a new design of mobile micro manipulation system for robotic micro assembly where a compliant piezoelectric actuator based micro gripper is designed for handling the miniature parts and compensation of misalignment during peg-in-hole assembly is done because piezoelectric actuator has capability of producing the displacement in micron range and generates high force instantaneously. This adjusts the misalignment of peg during robotic micro assembly. The throughput/speed of mobile micro manipulation system is found for picking and placing the peg from one hole to next hole position. An analysis of piezoelectric actuator based micro gripper has been carried out where voltage is controlled through a proportional-derivative (PD) controller. By developing a prototype, it is demonstrated that compliant piezoelectric actuator based micro gripper is capable of handling the peg-in-hole assembly task in a mobile micro manipulation system. 相似文献
2.
AbstractBa0.95Ca0.05Ti1-xZrxO3 (BCTZO) ceramics were prepared by a solid state reaction method. The samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray absorption near edge structure (XANES). The ceramics exhibit a pure perovskite structure. The average grain size gradually decreases with increasing Zr concentration. XANES results indicate that the intensities of pre-edge peaks dropped with increasing Zr concentration. The BCTZO ceramic of x?=?0.05 has the optimum electrical properties with the maximum dielectric constant (ε'm), remanent polarization (2Pr), coercive electric field (2Ec) and piezoelectric charge constant (d33) of 7,244, 12.54 (μC/cm2), 5.29 (kV/cm) and 288 (pC/N), respectively. 相似文献
3.
The Er3+ doped oxyfluorogermanate glasses, with a composition containing Na element, were synthesized by the conventional melting–quenching technique. When Na element was introduced into the composition of oxyfluorogermanate glass, the crystals behavior was investigated in details. Depending on the annealing procedure supplied, thermal annealing of precursor glasses in the system GeO2/BaF2/AlF3/Na2O/NaF/ZnO/GdF3/ErF3 led to the precipitation of different crystal phase nanocrystals. It was confirmed the nanocrystals in GC600 is orthorhombic NaBaAlF6 which led to enhance obviously in the UC luminescence of Er3+. However, the nanocrystals in G585 led to decrease in the UC luminescence, which indicated few Er ions enter into the lattice of this nanocrystal phase. The reason of the decrease in UC emission intensity of GC585 was analyzed. 相似文献
4.
This paper mainly focuses on the development of pressure tracking control logic of electro-hydraulic actuators for vehicle application. This is done to improve and ensure the performance of a precise lower-level controller for evolving modern shift control logic. The required performance is obtained by hysteresis model-based feed-forward control and additional feedback control. The hysteresis and the time delay, which adversely affect pressure control, are well known nonlinear behaviors in electro-hydraulic actuators. In order to cope with the hysteresis, a novel hysteresis model is proposed based on a physical phenomenon. A mathematical model based on a characteristic curve obtained in preliminary experiments is presented using only one tuning parameter, and this model can be inverted easily to construct a feed-forward controller. In addition, a feedback controller is designed considering the stability margin of a time delay system. The feedback control inputs ensure compensation of the feed-forward errors caused by model error and uncertainty. The proposed controller is designed to lower computational cost considering applicability for production vehicles. As a result, the developed pressure controller is applied to a transmission control unit of a production vehicle and verified experimentally for various driving scenarios. 相似文献
5.
6.
Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the jointwere measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the SisN4/SisN4 joints were obtained bybrazing at 1373~1473 K f 相似文献
7.
8.
9.
在概括了自蔓延高温合成陶瓷内衬钢管的制备原理基础上,从降低陶瓷层孔隙率,减少陶瓷层裂纹和提高陶瓷层结合强度等方面,论述了提高自蔓延高温合成陶瓷内衬钢管性能的措施,对自蔓延高温合成陶瓷内衬钢管的应用现状及展望进行了评述。 相似文献
10.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献