全文获取类型
收费全文 | 14648篇 |
免费 | 1045篇 |
国内免费 | 113篇 |
专业分类
电工技术 | 224篇 |
综合类 | 62篇 |
化学工业 | 3789篇 |
金属工艺 | 370篇 |
机械仪表 | 525篇 |
建筑科学 | 536篇 |
矿业工程 | 21篇 |
能源动力 | 1041篇 |
轻工业 | 1393篇 |
水利工程 | 193篇 |
石油天然气 | 229篇 |
武器工业 | 4篇 |
无线电 | 1523篇 |
一般工业技术 | 2756篇 |
冶金工业 | 559篇 |
原子能技术 | 96篇 |
自动化技术 | 2485篇 |
出版年
2024年 | 68篇 |
2023年 | 282篇 |
2022年 | 635篇 |
2021年 | 968篇 |
2020年 | 812篇 |
2019年 | 867篇 |
2018年 | 988篇 |
2017年 | 894篇 |
2016年 | 861篇 |
2015年 | 516篇 |
2014年 | 803篇 |
2013年 | 1461篇 |
2012年 | 963篇 |
2011年 | 1009篇 |
2010年 | 718篇 |
2009年 | 639篇 |
2008年 | 459篇 |
2007年 | 389篇 |
2006年 | 333篇 |
2005年 | 218篇 |
2004年 | 184篇 |
2003年 | 168篇 |
2002年 | 126篇 |
2001年 | 103篇 |
2000年 | 100篇 |
1999年 | 86篇 |
1998年 | 160篇 |
1997年 | 127篇 |
1996年 | 104篇 |
1995年 | 78篇 |
1994年 | 60篇 |
1993年 | 63篇 |
1992年 | 49篇 |
1991年 | 41篇 |
1990年 | 45篇 |
1989年 | 39篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 37篇 |
1985年 | 33篇 |
1984年 | 33篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 24篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Heiba Zein K. Mohamed Mohamed Bakr Farag Noura M. Badawi Ali 《Journal of Materials Science: Materials in Electronics》2022,33(13):10388-10398
Journal of Materials Science: Materials in Electronics - Nano Mn0.95M0.05S (M ≡ Cu, Mg) samples were produced using molten salt solid state reaction method. Rietveld analysis of X-ray... 相似文献
12.
13.
Tuladhar Sanira Alsadoon Abeer Prasad P. W. C. Ali Akbas Ezaldeen Alrubaie Ahmad 《Multimedia Tools and Applications》2022,81(17):23845-23865
Multimedia Tools and Applications - Gastrointestinal stromal tumor is one of the critical tumors that doctors do not suggest to get frequent endoscopy, so there is a need for a diagnosis system... 相似文献
14.
Iqbal Ahmad Syed Mujtaba Shah Muhammad Nadeem Zafar Muhammad Naeem Ashiq Wei Tang Uzma Jabeen 《Ceramics International》2021,47(3):3760-3771
Ferrites are materials of interest due to their broad applications in high technological devices and a lot of research has been focused to synthesize new ferrites. In this regard, an effort has been devoted to synthesize spinel Pr–Ni co-substituted strontium ferrites with a nominal formula of Sr1-xPrxFe2-yNiyO4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0). The cubic structure of pure and Pr–Ni co-substituted strontium ferrite samples calcinated at 1073 K for 3 h has been confirmed through X-ray diffraction (XRD). Average sizes of crystallites (18–25 nm) have been estimated from XRD analysis and nanometer particle sizes of synthesized ferrites have been further verified by scanning electron microscopy (SEM). SEM results have also shown that particles are mostly agglomerated and all the samples possess porosity. It has been observed that at 298 K, the values of resistivity (ρ) increase, while that of AC conductivity, dielectric loss, and dielectric constants decrease with increasing amounts of Pr3+ and Ni2+ ions. The values of dielectric parameters initially decrease with frequency and later become constant and can be explained on the basis of dielectric polarization. Electrochemical impedance spectroscopy (EIS) studies show that the charge transport phenomenon in ferrite materials is mainly controlled via grain boundaries. Overall, synthesized ferrite materials own enhanced resistivity values in the range of 1.38 × 109–1.94 × 109 Ω cm and minimum dielectric losses, which makes them suitable candidates for high frequency devices applications. 相似文献
15.
Water Resources Management - This work presents an analytical solution for the linearized Boussinesq equation describing the nature of well hydraulics in equilateral triangular-shaped unconfined... 相似文献
16.
Output feedback controller for polytopic systems exploiting the direct searching of the design space
This paper deals with the problem of designing a robust static output feedback controller for polytopic systems. The current research that tackled this problem is mainly based on LMI method, which is conservative by nature. In this paper, a novel approach is proposed, which considers the design space of the controller parameters and iteratively partitions the space to small simplexes. Then, by assessing the stability in each simplex, the solution space for design parameters is directly determined. It has been theoretically proved that, if there exists a feasible solution in the design space, the algorithm can find it. To validate the result of the proposed approach, comparative simulation examples are given to illustrate the performance of the design methodology as compared to those of previous approaches. 相似文献
17.
AbstractIndustry 4.0 aims at providing a digital representation of a production landscape, but the challenges in building, maintaining, optimizing, and evolving digital models in inter-organizational production chains have not been identified yet in a systematic manner. In this paper, various Industry 4.0 research and technical challenges are addressed, and their present scenario is discussed. Moreover, in this article, the novel concept of developing experience-based virtual models of engineering entities, process, and the factory is presented. These models of production units, processes, and procedures are accomplished by virtual engineering object (VEO), virtual engineering process (VEP), and virtual engineering factory (VEF), using the knowledge representation technique of Decisional DNA. This blend of the virtual and physical domains permits monitoring of systems and analysis of data to foresee problems before they occur, develop new opportunities, prevent downtime, and even plan for the future by using simulations. Furthermore, the proposed virtual model concept not only has the capability of Query Processing and Data Integration for Industrial Data but also real-time visualization of data stream processing. 相似文献
18.
19.
20.
Adaptive robust boundary control of shaft vibrations under perturbations with unknown upper bounds 下载免费PDF全文
This paper presents robust and adaptive boundary control designs to stabilize the two‐dimensional vibration of hybrid shaft model. The hybrid shaft is mathematically represented by a set of partial differential equations, governing the shaft vibrations, coupled to ordinary differential equations, describing rigid body spinning and dynamic boundary conditions. The control objective is to stabilize the transverse vibrations of the perturbed shaft while regulating the spinning rate. To achieve this, the paper first establishes robust boundary control laws that fulfil the control objective in the presence of modeling uncertainties and external disturbances operating over the shaft domain and boundary. Lyapunov‐based analyses show that the proposed robust control exponentially stabilizes the shaft with vanishing distributive perturbations, while assuring ultimately bounded vibrations in the case of nonvanishing perturbations. Then, adaptive control philosophy is utilized to achieve redesigned robust controllers that only use online adaptation of control gains without acquiring the knowledge of bounds on perturbations, as well as dynamic parameters. An advantage of this design is avoiding an overconservative robust control law, which may induce poor stability and chattering in tackling system perturbations with unknown upper bounds. Simulations through finite element method illustrate the results. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献