全文获取类型
收费全文 | 200716篇 |
免费 | 18943篇 |
国内免费 | 14091篇 |
专业分类
电工技术 | 33737篇 |
技术理论 | 7篇 |
综合类 | 20727篇 |
化学工业 | 10716篇 |
金属工艺 | 7240篇 |
机械仪表 | 18038篇 |
建筑科学 | 16251篇 |
矿业工程 | 7615篇 |
能源动力 | 5563篇 |
轻工业 | 5575篇 |
水利工程 | 6567篇 |
石油天然气 | 6307篇 |
武器工业 | 3028篇 |
无线电 | 16587篇 |
一般工业技术 | 10765篇 |
冶金工业 | 8282篇 |
原子能技术 | 1410篇 |
自动化技术 | 55335篇 |
出版年
2024年 | 863篇 |
2023年 | 2309篇 |
2022年 | 3764篇 |
2021年 | 4704篇 |
2020年 | 5679篇 |
2019年 | 4615篇 |
2018年 | 4125篇 |
2017年 | 5990篇 |
2016年 | 6617篇 |
2015年 | 7217篇 |
2014年 | 13253篇 |
2013年 | 11946篇 |
2012年 | 14747篇 |
2011年 | 15655篇 |
2010年 | 11875篇 |
2009年 | 12232篇 |
2008年 | 12186篇 |
2007年 | 14896篇 |
2006年 | 13185篇 |
2005年 | 11518篇 |
2004年 | 9609篇 |
2003年 | 8429篇 |
2002年 | 6820篇 |
2001年 | 5682篇 |
2000年 | 4950篇 |
1999年 | 3988篇 |
1998年 | 3019篇 |
1997年 | 2736篇 |
1996年 | 2193篇 |
1995年 | 1789篇 |
1994年 | 1551篇 |
1993年 | 1104篇 |
1992年 | 913篇 |
1991年 | 712篇 |
1990年 | 557篇 |
1989年 | 486篇 |
1988年 | 352篇 |
1987年 | 212篇 |
1986年 | 136篇 |
1985年 | 136篇 |
1984年 | 197篇 |
1983年 | 150篇 |
1982年 | 138篇 |
1981年 | 107篇 |
1980年 | 76篇 |
1979年 | 79篇 |
1978年 | 56篇 |
1977年 | 59篇 |
1964年 | 15篇 |
1959年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
61.
Mostafa Dellahi Hattab Maker Guillermo Botella Enrique Alameda-Hernandez Azeddine Mouhsen 《International Journal of Circuit Theory and Applications》2020,48(6):887-905
The three-phase four-wire shunt active power filter (SAPF) was developed to suppress the harmonic currents generated by nonlinear loads, and for the compensation of unbalanced nonlinear load currents, reactive power, and the harmonic neutral current. In this work, we consider instantaneous reactive power theory (PQ theory) for reference current identification based on the following two algorithms: the classic low-pass filter (LPF) and the second-order generalized integrator (SOGI) filter. Furthermore, since an important process in SAPF control is the regulation of the DC bus voltage at the capacitor, a new controller based on the Lyapunov function is also proposed. A complete simulation of the resultant active filtering system confirms its validity, which uses the SOGI filter to extract the reference currents from the distorted line currents, compared with the traditional PQ theory based on LPF. In addition, the simulation performed also demonstrates the superiority of the proposed approach, for DC bus voltage control based on the Lyapunov function, compared with the traditional proportional-integral (PI) controller. Both novel approaches contribute towards an improvement in the overall performance of the system, which consists of a small rise and settling time, a very low or nonexistent overshoot, and the minimization of the total harmonic distortion (THD). 相似文献
62.
Thermal comfort is an important factor for the design of buildings. Although it has been well recognized that many physiological parameters are linked to the state of thermal comfort or discomfort of humans, how to use physiological signal to judge the state of thermal comfort has not been well studied. In this paper, the feasibility of continuously determining feelings of personal thermal comfort was discussed by using electroencephalogram (EEG) signals in private space. In the study, 22 subjects were exposed to thermally comfortable and uncomfortably hot environments, and their EEG signals were recorded. Spectral power features of the EEG signals were extracted, and an ensemble learning method using linear discriminant analysis or support vector machine as a sub-classifier was used to build the discriminant model. The results show that an average discriminate accuracy of 87.9% can be obtained within a detection window of 60 seconds. This study indicates that it is feasible to distinguish whether a person feels comfortable or too hot in their private space by multi-channel EEG signals without interruption and suggests possibility for further applications in neuroergonomics. 相似文献
63.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
64.
Traditional maximum power point tracking (MPPT) methods can hardly find global maximum power point (MPP) because output characteristics curve of photovoltaic (PV) array may have multi local maximum power points in irregular shadow, and thus easily fall into the local maximum power point. To address this drawback, Considering that sliding mode variable structure (SMVS) control strategy have such advantages as simple structure, fast response and strong robustness, and P&O method have the advantages of simple principle and convenient implementation, so a new algorithm combining SMVS control method and P&O method is proposed, besides, PI controller is applied to reduce system chattering caused by switching sliding surface. It is applied to MPPT control of PV array in irregular shadow to solve the problem of multi-peak optimization in partial shadow. In order to verity the rationality of the proposed algorithm, the experimental circuit is built, which achieves MPPT control by means of the proposed algorithm and P&O method. The experimental results show that compared with the traditional P&O algorithm, the proposed algorithm can fast track the global MPP, tracking speed increases by 60% and the relative error decreased by 20%. Moreover, the system becomes more stable near the MPP, the fluctuations of output power is greatly reduced, and thus make full use of solar energy. 相似文献
65.
66.
67.
Jianhuai Dong Zhixuan Dong 《International Journal of Adaptive Control and Signal Processing》2020,34(10):1466-1482
This article studies the optimal filtering and control for wireless networked control systems (WNCSs). In WNCSs, packets may be lost in both control and feedback channels and user datagram protocol is usually used to improve the performance of the real-time control. Relevant literature indicates that the conventional optimal filtering for such a system cannot be applied in practice due to the complex calculation with Gaussian mixtures. This paper proposes a novel scheme to realize the optimal filtering and the linear quadratic Gaussian control for WNCSs, in which the controlled node performs a local estimation and the remote-control node performs the final estimation and control, and a synchronization of two estimators is guaranteed by a communication mechanism. An optimal filtering algorithm is developed, the stability condition of the filtering error covariance is obtained, optimal finite-horizon and infinite-horizon control are derived, and the stability of the closed-loop control system is proved. Numerical simulations show the validity and feasibility of the theoretical results. 相似文献
68.
Application of high‐temperature Fenton oxidation for the treatment of sulfonation plant wastewater
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
69.
针对传统的小区内开环功率控制算法通常以提升本小区的吞吐量性能为目标,忽略了当前小区用户对邻小区用户同频干扰的问题,为提升边缘用户性能的同时兼顾系统整体性能,提出了一种LTE系统小区间上行联合功率控制(UJPC)算法。该算法采用单基站三扇区为系统模型,以最优化系统吞吐量比例公平函数为目标,首先根据最小信干噪比(SINR)约束值和用户最大发射功率这两个约束条件得到相应的数学优化模型,然后采用连续凸近似的方法求解优化问题得出各个基站所管辖的小区内所有用户的最优发射功率。仿真结果表明,与基准的开环功控方案相比,联合功控方案在保证系统平均频谱利用率的情况下能够较大幅度地提高小区边缘频谱利用率,其最佳性能增益能达到50%。 相似文献
70.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献