全文获取类型
收费全文 | 92003篇 |
免费 | 15136篇 |
国内免费 | 10005篇 |
专业分类
电工技术 | 10162篇 |
技术理论 | 6篇 |
综合类 | 9909篇 |
化学工业 | 5961篇 |
金属工艺 | 2851篇 |
机械仪表 | 7380篇 |
建筑科学 | 3937篇 |
矿业工程 | 2430篇 |
能源动力 | 3431篇 |
轻工业 | 3481篇 |
水利工程 | 1903篇 |
石油天然气 | 2921篇 |
武器工业 | 1077篇 |
无线电 | 8547篇 |
一般工业技术 | 7255篇 |
冶金工业 | 3929篇 |
原子能技术 | 375篇 |
自动化技术 | 41589篇 |
出版年
2024年 | 453篇 |
2023年 | 3441篇 |
2022年 | 5878篇 |
2021年 | 6096篇 |
2020年 | 5805篇 |
2019年 | 4216篇 |
2018年 | 3288篇 |
2017年 | 3726篇 |
2016年 | 3994篇 |
2015年 | 4630篇 |
2014年 | 6761篇 |
2013年 | 6332篇 |
2012年 | 7381篇 |
2011年 | 7683篇 |
2010年 | 5438篇 |
2009年 | 5647篇 |
2008年 | 5208篇 |
2007年 | 5591篇 |
2006年 | 4721篇 |
2005年 | 3950篇 |
2004年 | 3124篇 |
2003年 | 2539篇 |
2002年 | 2116篇 |
2001年 | 1675篇 |
2000年 | 1345篇 |
1999年 | 949篇 |
1998年 | 869篇 |
1997年 | 733篇 |
1996年 | 611篇 |
1995年 | 533篇 |
1994年 | 425篇 |
1993年 | 356篇 |
1992年 | 289篇 |
1991年 | 211篇 |
1990年 | 196篇 |
1989年 | 167篇 |
1988年 | 97篇 |
1987年 | 57篇 |
1986年 | 75篇 |
1985年 | 39篇 |
1984年 | 41篇 |
1983年 | 35篇 |
1982年 | 29篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1965年 | 24篇 |
1964年 | 25篇 |
1963年 | 23篇 |
1957年 | 23篇 |
1955年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
This paper focuses on the configuration design of flexure hinges with a prescribed compliance matrix and preset rotational center position. A new method for the topology optimization of flexure hinges is proposed based on the adaptive spring model and stress constraint. The hinge optimization model is formulated by maximizing the bending displacement with a spring while optimizing the compliance matrix to a prescribed value. To avoid numerical instability, an artificial spring is used as an auxiliary calculation, and a new strategy is developed for adaptively adjusting the spring stiffness according to the prescribed compliance matrix. The maximum stress of flexure hinge is limited by using a normalized P-norm of the effective von Mises stress, and a position constraint of rotational center is proposed to predetermine the position of the rotational center. In addition, to reduce the error of the stress measurement, a simple but effective filtering method is presented to obtain a complete black-and-white design. Numerical examples are used to verify the proposed method. Topology results show that the obtained flexure hinges have the prescribed compliance matrix and preset rotational center position while also meeting the stress requirements. 相似文献
2.
Recently, a number of classification techniques have been introduced. However, processing large dataset in a reasonable time has become a major challenge. This made classification task more complex and expensive in calculation. Thus, the need for solutions to overcome these constraints such as field programmable gate arrays (FPGAs). In this paper, we give an overview of the various classification techniques. Then, we present the existing FPGA based implementation of these classification methods. After that, we investigate the confronted challenges and the optimizations strategies. Finally, we highlight the hardware accelerator architectures and tools for hardware design suggested to improve the FPGA implementation of classification methods. 相似文献
3.
Tracking-by-detection (TBD) is a significant framework for visual object tracking. However, current trackers are usually updated online based on random sampling with a probability distribution. The performance of the learning-based TBD trackers is limited by the lack of discriminative features, especially when the background is full of semantic distractors. We propose an attention-driven data augmentation method, in which a residual attention mechanism is integrated into the TBD tracking network as supplementary references to identify discriminative image features. A mask generating network is used to simulate changes in target appearances to obtain positive samples, where attention information and image features are combined to identify discriminative features. In addition, we propose a method for mining hard negative samples, which searches for semantic distractors with the response of the attention module. The experiments on the OTB2015, UAV123, and LaSOT benchmarks show that this method achieves competitive performance in terms of accuracy and robustness. 相似文献
4.
Corey Andrews Yiting Xu Michael Kirberger Jenny J. Yang 《International journal of molecular sciences》2021,22(1)
Calmodulin (CaM) is an important intracellular protein that binds Ca2+ and functions as a critical second messenger involved in numerous biological activities through extensive interactions with proteins and peptides. CaM’s ability to adapt to binding targets with different structures is related to the flexible central helix separating the N- and C-terminal lobes, which allows for conformational changes between extended and collapsed forms of the protein. CaM-binding targets are most often identified using prediction algorithms that utilize sequence and structural data to predict regions of peptides and proteins that can interact with CaM. In this review, we provide an overview of different CaM-binding proteins, the motifs through which they interact with CaM, and shared properties that make them good binding partners for CaM. Additionally, we discuss the historical and current methods for predicting CaM binding, and the similarities and differences between these methods and their relative success at prediction. As new CaM-binding proteins are identified and classified, we will gain a broader understanding of the biological processes regulated through changes in Ca2+ concentration through interactions with CaM. 相似文献
5.
Object detection performed by Autonomous Vehicles (AV)s is a crucial operation that comes ahead of various autonomous driving tasks, such as object tracking, trajectories estimation, and collision avoidance. Dynamic road elements (pedestrians, cyclists, vehicles) impose a greater challenge due to their continuously changing location and behaviour. This paper presents a comprehensive review of the state-of-the-art object detection technologies focusing on both the sensory systems and algorithms used. It begins with a brief introduction on the autonomous driving operations and challenges. Then, different sensory systems employed on existing AVs are elaborated while illustrating their advantages, limitations and applications. Also, sensory systems employed by different research are reviewed. Moreover, due to the significant role Deep Neural Networks (DNN)s are playing in object detection tasks, different DNN-based networks are also highlighted. Afterwards, previous research on dynamic objects detection performed by AVs are reviewed in tabular forms. Finally, a conclusion summarizes the outcomes of the review and suggests future work towards the development of vehicles with higher automation levels. 相似文献
6.
7.
A Quantitative Critical Thinking (QCT) software tool was developed in this study to facilitate students’ learning of quantitative critical thinking via repeated practice by chemical engineering students reading a core module called fluid-solid systems. The software tool generated detailed calculation steps to typical engineering design problems encountered in this module that contained weaknesses, flaws or even errors. Students utilized the software tool to practice identifying these weaknesses, flaws or errors in the design solutions and then present a better or correct design by applying the concepts and knowledge acquired in the module. Since the QCT software tool was built upon an existing design software tool that was able to generate the correct, detailed design calculation steps to design problems, students were able to check their own design calculations against those presented by the software tool during this second learning step, thereby engaging in and learning quantitative critical thinking via a repeated practice approach. The software tool was successful in enhancing the performance of second-year undergraduate students in solving a question that required quantitative critical thinking in the final examination of the module. The average percentage scores achieved by students for the question who reported higher frequencies of usage of the software were generally higher than those who reported lower frequencies of usage or did not utilize the software tool throughout the semester. 相似文献
8.
This study proposes a multiperiod mixed integer linear programming model for the management of a single municipal solid waste (MSW) treatment plant with sustainability as the objective. Discrete and continuous variables define the capacity selections for diverse MSW technologies, and the operation of the MSW network, respectively. The economic target is considered to maximize the net present value. The environmental impact is the minimization of a normalized environmental objective function (NEOF). The social target is the maximization of jobs. An interesting feature about the research work is the requirement of biodrying technologies for MSW moisture content control. Due to the conflicted nature among the sustainability components, a multiobjective optimization (MO) is carried out to find the Pareto optimal solutions. The MO results show that the Pareto optimal solutions vary around profit range of $4.9–8.5 billion, NEOF impact range of 3.2–3.6 units, and social benefit range of 2700–4828 jobs. 相似文献
9.
干法后处理技术是我国核燃料循环体系的重要发展方向,其中有发展前景的熔盐电解法在工业化过程中需要对元素进行准确地监测以保障安全运行。传统离线检测方法程序复杂、数据分析延迟,而在线监测方法因可以获得实时数据而备受瞩目。本文对近几年国内外熔盐电解法中不同元素的在线监测技术进行了总结,重点调研分析了电化学法中的循环伏安法、安培法、脉冲法以及光谱法中的荧光光谱法和紫外光谱法在各种元素的在线监测中的原理、特点和应用前景,以期对熔盐电解中在线监测技术的研发和实际应用提供理论支撑和技术参考。 相似文献
10.
Thomas R. Savage Fernando Almeida-Trasvina Ehecatl A. del-Rio Chanona Robin Smith Dondga Zhang 《American Institute of Chemical Engineers》2021,67(11):e17358
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems. 相似文献