全文获取类型
收费全文 | 141285篇 |
免费 | 13543篇 |
国内免费 | 8489篇 |
专业分类
电工技术 | 10323篇 |
技术理论 | 3篇 |
综合类 | 12779篇 |
化学工业 | 20659篇 |
金属工艺 | 8553篇 |
机械仪表 | 9426篇 |
建筑科学 | 10236篇 |
矿业工程 | 3821篇 |
能源动力 | 4147篇 |
轻工业 | 11094篇 |
水利工程 | 3312篇 |
石油天然气 | 6179篇 |
武器工业 | 1547篇 |
无线电 | 16890篇 |
一般工业技术 | 14597篇 |
冶金工业 | 6272篇 |
原子能技术 | 1847篇 |
自动化技术 | 21632篇 |
出版年
2024年 | 478篇 |
2023年 | 1586篇 |
2022年 | 3262篇 |
2021年 | 4700篇 |
2020年 | 3605篇 |
2019年 | 2976篇 |
2018年 | 3277篇 |
2017年 | 3951篇 |
2016年 | 3819篇 |
2015年 | 5372篇 |
2014年 | 7091篇 |
2013年 | 8382篇 |
2012年 | 10333篇 |
2011年 | 10958篇 |
2010年 | 10426篇 |
2009年 | 10152篇 |
2008年 | 10033篇 |
2007年 | 9556篇 |
2006年 | 9043篇 |
2005年 | 7530篇 |
2004年 | 6014篇 |
2003年 | 5460篇 |
2002年 | 6149篇 |
2001年 | 5364篇 |
2000年 | 3486篇 |
1999年 | 2495篇 |
1998年 | 1509篇 |
1997年 | 1293篇 |
1996年 | 1121篇 |
1995年 | 937篇 |
1994年 | 698篇 |
1993年 | 498篇 |
1992年 | 382篇 |
1991年 | 301篇 |
1990年 | 255篇 |
1989年 | 172篇 |
1988年 | 142篇 |
1987年 | 114篇 |
1986年 | 56篇 |
1985年 | 57篇 |
1984年 | 52篇 |
1983年 | 42篇 |
1982年 | 28篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 19篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1959年 | 12篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Jong-Hwan Kim Yeon-Chan Hong Sung-Jun Lee Keh-Kun Choi 《Industrial Electronics, IEEE Transactions on》1989,36(3):361-364
A direct adaptive control scheme is proposed for nonminimum-phase systems in which controller parameters are estimated from the recursive least-squares algorithm and additional auxiliary parameters are obtained from the proposed polynomial identity. A local convergence is guaranteed without any extra condition. Integral action is incorporated into the adaptive controller to eliminate the steady-state error and to satisfy a condition of the unique solution for the polynomial identity. The control law used in this scheme is based on the set-point-on-I-only proportional-integral-derivative (PID) structure 相似文献
102.
Yong Xia Rongming Lin 《International journal for numerical methods in engineering》2004,59(1):153-172
Order reduction is a computationally efficient method to estimate some lowest eigenvalues and the corresponding eigenvectors of large structural systems by reducing the order of the original model to a smaller one. But its accuracy is limited to a small range of frequencies that depends on the selection of the retained degrees of freedom. This paper proposes a new iterative order reduction (IOR) technique to obtain accurately the eigensolutions of large structural systems. The technique retains all the inertia terms associated with the removed degrees of freedom. This hence leads to the reduced mass matrix being in an iterated form and the reduced stiffness matrix constant. From these mass and stiffness matrices, the eigensolutions of the reduced system can be obtained iteratively. On convergence the reduced system reproduces the eigensolutions of the original structure. A proof of the convergence property is also presented. Applications of the method to a practical GARTEUR structure as well as a plate have demonstrated that the proposed method is comparable to the commonly used Subspace Iteration method in terms of numerical accuracy. Moreover, it has been found that the proposed method is computationally more efficient than the Subspace Iteration method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
103.
104.
移动代理计算模式较传统的分布式计算模式有明显的优势,而伴随它有诸多安全问题出现,这使得它没有得到十分广泛的应用。本文针对代理自身的安全问题,分析了代理可能受到的攻击,并提出了一个安全方案。 相似文献
105.
我国风机盘管技术现状分析 总被引:2,自引:2,他引:0
介绍了近年来我国在风机盘管技术领域的最新成果,在结构形式、强化传热、提高室内空气品质、降低噪音和提高自动控制水平等方面的技术进展情况,分析了目前风机盘管中存在的问题,并对今后的发展方向进行了展望。 相似文献
106.
Yong Bae Park Keum Cheol Hwang Ikmo Park 《Microwave and Wireless Components Letters, IEEE》2008,18(3):152-154
A tapered coaxial tip in a parallel plate waveguide is investigated. A boundary-value problem of electromagnetic scattering from a tapered coaxial monopole is solved rigorously based on the Fourier transform, eigenfunction expansion, and mode matching. Scattering parameters are represented in a series and computed to understand the behavior of the scattering in terms of the coaxial tip geometry. 相似文献
107.
根据某雷达系统对测量信号的快速传输要求,提出采用滑动帧的处理方法并在FPGA中实现,克服了传统帧处理难以满足快速传输要求的不足。阐述了滑动帧结构的构造思想,详述了滑动帧结构的特点及具体功能模块的实现。根据实际应用需求构造了滑动帧结构处理器,试验和应用结果表明设计可行有效,能充分满足实时数据传输的要求。 相似文献
108.
Xiaojun Xie Yonghong Cheng Hong Wang Qian Wang Xiaolin Chen Caixin Sun 《Ceramics International》2008,34(4):689-693
In the ideal A2B2O6O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi1.5ZnNb1.5−xTaxO7 (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores. 相似文献
109.
110.