全文获取类型
收费全文 | 478832篇 |
免费 | 47894篇 |
国内免费 | 29348篇 |
专业分类
电工技术 | 83728篇 |
技术理论 | 29篇 |
综合类 | 53104篇 |
化学工业 | 32902篇 |
金属工艺 | 17222篇 |
机械仪表 | 36485篇 |
建筑科学 | 41966篇 |
矿业工程 | 18956篇 |
能源动力 | 21235篇 |
轻工业 | 16478篇 |
水利工程 | 16154篇 |
石油天然气 | 15773篇 |
武器工业 | 6789篇 |
无线电 | 46040篇 |
一般工业技术 | 35835篇 |
冶金工业 | 15119篇 |
原子能技术 | 6561篇 |
自动化技术 | 91698篇 |
出版年
2024年 | 1355篇 |
2023年 | 5479篇 |
2022年 | 10545篇 |
2021年 | 12782篇 |
2020年 | 14068篇 |
2019年 | 11330篇 |
2018年 | 10444篇 |
2017年 | 14037篇 |
2016年 | 16117篇 |
2015年 | 18132篇 |
2014年 | 31250篇 |
2013年 | 27783篇 |
2012年 | 37238篇 |
2011年 | 38869篇 |
2010年 | 29280篇 |
2009年 | 29742篇 |
2008年 | 28950篇 |
2007年 | 35539篇 |
2006年 | 31358篇 |
2005年 | 27131篇 |
2004年 | 22246篇 |
2003年 | 19308篇 |
2002年 | 15234篇 |
2001年 | 12807篇 |
2000年 | 10771篇 |
1999年 | 8636篇 |
1998年 | 6620篇 |
1997年 | 5501篇 |
1996年 | 4716篇 |
1995年 | 4073篇 |
1994年 | 3419篇 |
1993年 | 2374篇 |
1992年 | 2043篇 |
1991年 | 1456篇 |
1990年 | 1193篇 |
1989年 | 1086篇 |
1988年 | 760篇 |
1987年 | 431篇 |
1986年 | 315篇 |
1985年 | 230篇 |
1984年 | 226篇 |
1983年 | 180篇 |
1982年 | 173篇 |
1981年 | 146篇 |
1980年 | 103篇 |
1979年 | 104篇 |
1978年 | 69篇 |
1977年 | 54篇 |
1976年 | 45篇 |
1959年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Aishwarya
Srivastava Siddhant Aggarwal Amy Apon Edward Duffy Ken Kennedy Andre Luckow Brandon Posey Marcin Ziolkowski 《Software》2020,50(6):868-898
We investigate the challenges of building an end-to-end cloud pipeline for real-time intelligent visual inspection system for use in automotive manufacturing. Current methods of visual detection in automotive assembly are highly labor intensive, and thus prone to errors. An automated process is sought that can operate within the real-time constraints of the assembly line and can reduce errors. Components of the cloud pipeline include capture of a large set of high-definition images from a camera setup at the assembly location, transfer and storage of the images as needed, execution of object detection, and notification to a human operator when a fault is detected. The end-to-end execution must complete within a fixed time frame before the next car arrives in the assembly line. In this article, we report the design, development, and experimental evaluation of the tradeoffs of performance, accuracy, and scalability for a cloud system. 相似文献
102.
Kevin J. Hanley 《International journal for numerical methods in engineering》2020,121(21):4865-4877
An algorithm is presented for discrete element method simulations of energy-conserving systems of frictionless, spherical particles in a reversed-time frame. This algorithm is verified, within the limits of round-off error, through implementation in the LAMMPS code. Mechanisms for energy dissipation such as interparticle friction, damping, rotational resistance, particle crushing, or bond breakage cannot be incorporated into this algorithm without causing time irreversibility. This theoretical development is applied to critical-state soil mechanics as an exemplar. It is shown that the convergence of soil samples, which differ only in terms of their initial void ratio, to the same critical state requires the presence of shear forces and frictional dissipation within the soil system. 相似文献
103.
Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas. 相似文献
104.
105.
106.
Serena Finco Daria Battini Xavier Delorme Alessandro Persona Fabio Sgarbossa 《国际生产研究杂志》2020,58(4):1255-1270
Ergonomic aspects have a crucial role in manual assembly systems. They impact on the workers’ health, final product quality and productivity. For these reasons, there is the necessity to integrate them into the assembly line balancing phase as, whereas, only time and cost variables are considered. In this study, human energy expenditures are considered as ergonomic aspects and we integrate them, for the first time, into the assembly line balancing problem type 2 through the rest allowance evaluation. We consider as an objective function the minimization of the smoothness index. Firstly, a new optimal method based on mixed integer linear programming and a new linearization methodology are proposed. Then, a heuristic approach is introduced. To complete the study, a computational experimentation is presented to validate the mathematical model and to compare the methodologies proposed in terms of computational time, complexity and solution. Additionally, we provide a detailed analysis of the impact that rest allowance evaluation can have on productivity comparing the results obtained, taking into account the rest allowance integration before, during and after the assembly balancing process. 相似文献
107.
Optimal power flow with generation reallocation is a suitable method for better utilization of the existing system. In recent years, Flexible AC Transmission System (FACTS) devices, have led to the development of controllers that provide controllability and flexibility for power transmission. Out of the FACTS devices unified power flow controller (UPFC) is a versatile device, capable of controlling the power system parameters like voltage magnitude, phase angle and line impedance individually or simultaneously. The main aim of this paper is to minimize real power losses in a power system using BAT search algorithm without and with the presence of UPFC. Minimization of real power losses is done by considering the power generated by generator buses, voltage magnitudes at generator buses and reactive power injection from reactive power compensators. The proposed BAT algorithm based Optimal Power Flow (OPF) has been tested on a 5 bus test system and modified IEEE 30 bus system without and with UPFC. The results of the system with and without UPFC are compared in terms of active power losses in the transmission line using BAT algorithm. The obtained results are also compared with Genetic algorithm (GA). 相似文献
108.
109.
This study proposes that a novel integrated circuit (IC) and system design for renewable energy inverters can harvest renewable energy to power direct current (DC) and alternating current (AC) loads. In addition, an intelligent synthesis and management tool is developed to design the proposed system and to judge the system’s operational maintenance decisions. Finally, a renewable energy inverter’s information is posted to an online system. Users can obtain the proposed system’s information at any time and place. The accurate and superior performance of the proposed IC and system is confirmed by computer simulations and experimental results. 相似文献
110.
This paper introduces a simultaneous process optimization and heat integration approach, which can be used directly with the rigorous models in process simulators. In this approach, the overall process is optimized utilizing external derivative-free optimizers, which interact directly with the process simulation. The heat integration subproblem is formulated as an LP model and solved simultaneously during optimization of the flowsheet to update the minimum utility and heat exchanger area targets. A piecewise linear approximation for the composite curve is applied to obtain more accurate heat integration results. This paper describes the application of this simultaneous approach for three cases: a recycle process, a separation process and a power plant with carbon capture. Case study results indicate that this simultaneous approach is relatively easy to implement and achieves higher profit and lower operating cost and, in the case of the power plant example, higher net efficiency than the sequential approach. 相似文献