全文获取类型
收费全文 | 165740篇 |
免费 | 14840篇 |
国内免费 | 9932篇 |
专业分类
电工技术 | 12454篇 |
技术理论 | 14篇 |
综合类 | 15462篇 |
化学工业 | 14257篇 |
金属工艺 | 4967篇 |
机械仪表 | 9404篇 |
建筑科学 | 17562篇 |
矿业工程 | 4759篇 |
能源动力 | 6522篇 |
轻工业 | 10974篇 |
水利工程 | 4515篇 |
石油天然气 | 8261篇 |
武器工业 | 2134篇 |
无线电 | 11859篇 |
一般工业技术 | 11926篇 |
冶金工业 | 7064篇 |
原子能技术 | 1107篇 |
自动化技术 | 47271篇 |
出版年
2024年 | 632篇 |
2023年 | 2272篇 |
2022年 | 3765篇 |
2021年 | 4778篇 |
2020年 | 5126篇 |
2019年 | 4512篇 |
2018年 | 4296篇 |
2017年 | 5157篇 |
2016年 | 5900篇 |
2015年 | 6078篇 |
2014年 | 10264篇 |
2013年 | 10609篇 |
2012年 | 11252篇 |
2011年 | 12293篇 |
2010年 | 9269篇 |
2009年 | 9842篇 |
2008年 | 9353篇 |
2007年 | 11166篇 |
2006年 | 9809篇 |
2005年 | 8613篇 |
2004年 | 7044篇 |
2003年 | 6399篇 |
2002年 | 5198篇 |
2001年 | 4318篇 |
2000年 | 3657篇 |
1999年 | 2980篇 |
1998年 | 2332篇 |
1997年 | 2079篇 |
1996年 | 1864篇 |
1995年 | 1561篇 |
1994年 | 1272篇 |
1993年 | 1062篇 |
1992年 | 821篇 |
1991年 | 710篇 |
1990年 | 542篇 |
1989年 | 505篇 |
1988年 | 372篇 |
1987年 | 291篇 |
1986年 | 248篇 |
1985年 | 306篇 |
1984年 | 304篇 |
1983年 | 284篇 |
1982年 | 234篇 |
1981年 | 174篇 |
1980年 | 147篇 |
1979年 | 129篇 |
1978年 | 86篇 |
1977年 | 93篇 |
1976年 | 41篇 |
1963年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
101.
102.
Spherical LiNi1/3Co1/3Mn1/3O2 cathode particles were resynthesized by a carbonate co-precipitation method using spent lithium-ion batteries (LIBs) as a raw material. The physical characteristics of the Ni1/3Co1/3Mn1/3CO3 precursor, the (Ni1/3Co1/3Mn1/3)3O4 intermediate, and the regenerated LiNi1/3Co1/3Mn1/3O2 cathode material were investigated by laser particle-size analysis, scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), thermogravimetry–differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 was studied by continuous charge–discharge cycling and cyclic voltammetry. The results indicate that the regenerated Ni1/3Co1/3Mn1/3CO3 precursor comprises uniform spherical particles with a narrow particle-size distribution. The regenerated LiNi1/3Co1/3Mn1/3O2 comprises spherical particles similar to those of the Ni1/3Co1/3Mn1/3CO3 precursor, but with a narrower particle-size distribution. Moreover, it has a well-ordered layered structure and a low degree of cation mixing. The regenerated LiNi1/3Co1/3Mn1/3O2 shows an initial discharge capacity of 163.5 mA h g?1 at 0.1 C, between 2.7 and 4.3 V; the discharge capacity at 1 C is 135.1 mA h g?1, and the capacity retention ratio is 94.1% after 50 cycles. Even at the high rate of 5 C, LiNi1/3Co1/3Mn1/3O2 delivers the high capacity of 112.6 mA h g?1. These results demonstrate that the electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 is comparable to that of a cathode synthesized from fresh materials by carbonate co-precipitation. 相似文献
103.
This article presents a new approach for solving the Optimal Control Problem (OCP) of linear time-delay systems with a quadratic cost functional. The proposed method can also be used for designing optimal control time-delay systems with disturbance. In this study, the Variational Iteration Method (VIM) is employed to convert the original Time-Delay Optimal Control Problem (TDOCP) into a sequence of nonhomogeneous linear two-point boundary value problems (TPBVPs). The optimal control law obtained consists of an accurate linear feedback term and a nonlinear compensation term which is the limit of an adjoint vector sequence. The feedback term is determined by solving Riccati matrix differential equation. By using the finite-step iteration of a nonlinear compensation sequence, we can obtain a suboptimal control law. Finally, Illustrative examples are included to demonstrate the validity and applicability of the technique. 相似文献
104.
In recent years, the Industry 4.0 concept brings new demands and trends in different areas; one of them is distributing computational power to the cloud. This concept also introduced the Reference Architectural Model for Industry 4.0 (RAMI 4.0). The efficiency of data communications within the RAMI 4.0 model is a critical issue. Aiming to evaluate the efficiency of data communication in the Cloud Based Cyber-Physical Systems (CB-CPS), this study analyzes the periods and data amount required to communicate with individual hierarchy levels of the RAMI 4.0 model. The evaluation of the network properties of the communication protocols eligible for CB-CPS is presented. The network properties to different cloud providers and data centers’ locations have been measured and interpreted. To test the findings, an architecture for cloud control of laboratory model was proposed. It was found that the time of the day; the day of the week; and data center utilization have a negligible impact on latency. The most significant impact lies in the data center distance and the speed of the communication channel. Moreover, the communication protocol also has impact on the latency. The feasibility of controlling each level of RAMI 4.0 through cloud services was investigated. Experimental results showed that control is possible in many solutions, but these solutions mostly cannot depend just on cloud services. The intelligence on the edge of the network will play a significant role. The main contribution is a thorough evaluation of different cloud providers, locations, and communication protocols to provide recommendations sufficient for different levels of the RAMI 4.0 architecture. 相似文献
105.
Rui
Zhang Junmin Li Jianmin Jiao 《International Journal of Adaptive Control and Signal Processing》2020,34(7):919-936
This article investigates an adaptive fuzzy tracking control problem for a class of nontriangular form systems with asymmetric time-varying full state constraints. Unknown functions are approximated by the fuzzy logic systems. A domination approach is employed to tackle the nontriangular form structure. Time-varying asymmetric barrier Lyapunov functions (ABLFs) are adopted to ensure full-state constraints satisfaction. Based on the backstepping technique and time-varying ABLFs, an adaptive controller is proposed and guarantees that all the signals in the closed-loop system are ultimately bounded and the time-varying full state constraints are met. Simulation examples are presented to further demonstrate the effectiveness of the proposed approach. 相似文献
106.
107.
This study addresses the problem of choosing the most suitable probabilistic model selection criterion for unsupervised learning
of visual context of a dynamic scene using mixture models. A rectified Bayesian Information Criterion (BICr) and a Completed
Likelihood Akaike’s Information Criterion (CL-AIC) are formulated to estimate the optimal model order (complexity) for a given
visual scene. Both criteria are designed to overcome poor model selection by existing popular criteria when the data sample
size varies from small to large and the true mixture distribution kernel functions differ from the assumed ones. Extensive
experiments on learning visual context for dynamic scene modelling are carried out to demonstrate the effectiveness of BICr
and CL-AIC, compared to that of existing popular model selection criteria including BIC, AIC and Integrated Completed Likelihood
(ICL). Our study suggests that for learning visual context using a mixture model, BICr is the most appropriate criterion given
sparse data, while CL-AIC should be chosen given moderate or large data sample sizes. 相似文献
108.
109.
110.
Istvan S. N. Berkeley 《Minds and Machines》2006,16(4):471-478
Berkeley [Minds Machines 10 (2000) 1] described a methodology that showed the subsymbolic nature of an artificial neural network
system that had been trained on a logic problem, originally described by Bechtel and Abrahamsen [Connectionism and the mind.
Blackwells, Cambridge, MA, 1991]. It was also claimed in the conclusion of this paper that the evidence was suggestive that
the network might, in fact, count as a symbolic system. Dawson and Piercey [Minds Machines 11 (2001) 197] took issue with
this latter claim. They described some lesioning studies that they argued showed that Berkeley’s (2000) conclusions were premature.
In this paper, these lesioning studies are replicated and it is shown that the effects that Dawson and Piercey rely upon for
their argument are merely an artifact of a threshold function they chose to employ. When a threshold function much closer
to that deployed in the original studies is used, the significant effects disappear. 相似文献