全文获取类型
收费全文 | 49471篇 |
免费 | 4446篇 |
国内免费 | 3472篇 |
学科分类
工业技术 | 57389篇 |
出版年
2024年 | 103篇 |
2023年 | 667篇 |
2022年 | 598篇 |
2021年 | 1024篇 |
2020年 | 1325篇 |
2019年 | 1247篇 |
2018年 | 1179篇 |
2017年 | 1662篇 |
2016年 | 1840篇 |
2015年 | 1722篇 |
2014年 | 3222篇 |
2013年 | 4080篇 |
2012年 | 2851篇 |
2011年 | 3341篇 |
2010年 | 2430篇 |
2009年 | 2951篇 |
2008年 | 2839篇 |
2007年 | 2955篇 |
2006年 | 2565篇 |
2005年 | 2376篇 |
2004年 | 1980篇 |
2003年 | 1865篇 |
2002年 | 1668篇 |
2001年 | 1371篇 |
2000年 | 1310篇 |
1999年 | 1125篇 |
1998年 | 910篇 |
1997年 | 808篇 |
1996年 | 747篇 |
1995年 | 620篇 |
1994年 | 533篇 |
1993年 | 520篇 |
1992年 | 385篇 |
1991年 | 367篇 |
1990年 | 284篇 |
1989年 | 230篇 |
1988年 | 198篇 |
1987年 | 170篇 |
1986年 | 140篇 |
1985年 | 186篇 |
1984年 | 193篇 |
1983年 | 171篇 |
1982年 | 151篇 |
1981年 | 98篇 |
1980年 | 73篇 |
1979年 | 89篇 |
1978年 | 61篇 |
1977年 | 68篇 |
1976年 | 20篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
针对阳煤五矿广场变电站的高压开关老化问题,为了保证安全性,采用了GIS气体的高压绝缘开关进行了改造。在改造后,变电站的安全性得到了显著提高,设备运行可以节省成本200多万元。 相似文献
42.
Control of self-assembling systems at the micro- and nano-scale provides new opportunities for the engineering of novel materials in a bottom-up fashion. These systems have several challenges associated with control including high-dimensional and stochastic nonlinear dynamics, limited sensors for real-time measurements, limited actuation for control, and kinetic trapping of the system in undesirable configurations. Three main strategies for addressing these challenges are described, which include particle design (active self-assembly), open-loop control, and closed-loop (feedback) control. The strategies are illustrated using a variety of examples such as the design of patchy and Janus particles, the toggling of magnetic fields to induce the crystallization of paramagnetic colloids, and high-throughput crystallization of organic compounds in nanoliter droplets. An outlook of the future research directions and the necessary technological advancements for control of micro- and nano-scale self-assembly is provided. 相似文献
43.
The objective of this paper is to review and document the mine fleet management systems’ models and algorithms. The purpose is to understand the algorithms behind the fleet management systems and the proposed academic solutions in this area to identify any gaps in the current literature and to open up opportunities to establish research questions that need to be addressed in an integrated simulation and optimisation operational planning research framework. In this paper, we review industrial fleet management systems and the main academic algorithms behind such systems. The fleet management systems are divided into three subsequently related problems to review: shortest path, production optimisation and real-time dispatching. Finally, the limitations of current algorithms for fleet management systems are documented in terms of mining practice feasibility and optimality of the solution on large-scale problems. The results of this literature review enable us to evaluate the logical links between major components of an integrated simulation and optimisation operational planning framework with current theory of fleet management systems. 相似文献
44.
45.
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
46.
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
47.
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
48.
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
49.
A system is frequently represented by transfer functions in an input–output characterization. However, such a system (under mild assumptions) can also be represented by transfer functions in a port characterization, frequently referred to as a chain-scattering representation. Due to its cascade properties, the chain-scattering representation is used throughout many fields of engineering. This paper studies the relationship between poles and zeros of input–output and chain-scattering representations of the same system. 相似文献
50.
中国大陆PCB产业自动化的现况与未来 总被引:1,自引:1,他引:0
从中国大陆PCB发展的现况分析实行设备自动化连线为企业所创造的价值。设备自动化连线是中国大陆PCB必须面临的改革出路。 相似文献