全文获取类型
收费全文 | 138458篇 |
免费 | 15941篇 |
国内免费 | 11199篇 |
专业分类
电工技术 | 12678篇 |
技术理论 | 2篇 |
综合类 | 14315篇 |
化学工业 | 16416篇 |
金属工艺 | 9608篇 |
机械仪表 | 10534篇 |
建筑科学 | 11725篇 |
矿业工程 | 5249篇 |
能源动力 | 3841篇 |
轻工业 | 12929篇 |
水利工程 | 4421篇 |
石油天然气 | 4952篇 |
武器工业 | 1952篇 |
无线电 | 15452篇 |
一般工业技术 | 12023篇 |
冶金工业 | 5358篇 |
原子能技术 | 2321篇 |
自动化技术 | 21822篇 |
出版年
2024年 | 686篇 |
2023年 | 1890篇 |
2022年 | 4848篇 |
2021年 | 6469篇 |
2020年 | 4587篇 |
2019年 | 3301篇 |
2018年 | 3645篇 |
2017年 | 4064篇 |
2016年 | 3602篇 |
2015年 | 5949篇 |
2014年 | 7679篇 |
2013年 | 9276篇 |
2012年 | 11576篇 |
2011年 | 11652篇 |
2010年 | 11293篇 |
2009年 | 10826篇 |
2008年 | 11380篇 |
2007年 | 11340篇 |
2006年 | 9903篇 |
2005年 | 8364篇 |
2004年 | 5975篇 |
2003年 | 3951篇 |
2002年 | 3668篇 |
2001年 | 3215篇 |
2000年 | 2571篇 |
1999年 | 1206篇 |
1998年 | 513篇 |
1997年 | 421篇 |
1996年 | 347篇 |
1995年 | 234篇 |
1994年 | 205篇 |
1993年 | 144篇 |
1992年 | 159篇 |
1991年 | 94篇 |
1990年 | 111篇 |
1989年 | 110篇 |
1988年 | 53篇 |
1987年 | 63篇 |
1986年 | 39篇 |
1985年 | 18篇 |
1984年 | 21篇 |
1983年 | 24篇 |
1982年 | 6篇 |
1981年 | 22篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1959年 | 23篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
31.
针对基于容积脉搏波(PPG)提取运动心率时,传统心率提取算法由于运动噪声干扰使测量结果误差大、实时性不好的问题,提出一种抗运动干扰的实时心率提取方法。该方法通过实时小波去噪,同时结合三轴加速度信号(ACC)对运动进行分类训练,计算各运动状态心率增益,对实时心率值进行补偿。实验结果表明,通过与同时采集的ECG信号计算出的实时心率进行对比,绝对误差率仅为1.2%左右。相比传统心率提取算法,该算法具有抗干扰性强,实时准确的特点。 相似文献
32.
Liyan Wen Gang Tao Bin Jiang 《International Journal of Adaptive Control and Signal Processing》2021,35(3):373-400
In this article, adaptive compensation designs are developed for nonlinear systems with uncertainties from the system functions and persistent actuator failures of characterizations that (i) some unknown system inputs are stuck at some unknown fixed or varying values at unknown time instants and (ii) the failure pattern always switches from one to another and the switching does not stop. Such a controlled plant is described by an uncertain time-varying nonlinear system, and some robust adaptive feedback linearization based failure compensation results are studied for closed-loop system stabilization and bounded output tracking for some specific conditions. To improve the tracking performance in the presence of persistent actuator failures, a new adaptive control scheme is developed, using the failure indicator function which contains the failure pattern and failure time in the formulation. Detailed stability and tracking performance are shown. Simulation results are shown to verify the effectiveness of the proposed adaptive actuator failure compensation method. 相似文献
33.
Rachana R. Borkute Sren Woelke Gang Pei Anca Dorhoi 《International journal of molecular sciences》2021,22(9)
Neutrophils readily infiltrate infection foci, phagocytose and usually destroy microbes. In tuberculosis (TB), a chronic pulmonary infection caused by Mycobacterium tuberculosis (Mtb), neutrophils harbor bacilli, are abundant in tissue lesions, and their abundances in blood correlate with poor disease outcomes in patients. The biology of these innate immune cells in TB is complex. Neutrophils have been assigned host-beneficial as well as deleterious roles. The short lifespan of neutrophils purified from blood poses challenges to cell biology studies, leaving intracellular biological processes and the precise consequences of Mtb–neutrophil interactions ill-defined. The phenotypic heterogeneity of neutrophils, and their propensity to engage in cellular cross-talk and to exert various functions during homeostasis and disease, have recently been reported, and such observations are newly emerging in TB. Here, we review the interactions of neutrophils with Mtb, including subcellular events and cell fate upon infection, and summarize the cross-talks between neutrophils and lung-residing and -recruited cells. We highlight the roles of neutrophils in TB pathophysiology, discussing recent findings from distinct models of pulmonary TB, and emphasize technical advances that could facilitate the discovery of novel neutrophil-related disease mechanisms and enrich our knowledge of TB pathogenesis. 相似文献
34.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
35.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
36.
基于ABAQUS的显式动力学分析方法研究 总被引:1,自引:0,他引:1
显式动力学(The Explicit Dynamic)是针对隐式求解器的一个补充,其分析方法对于求解广泛、各类非线性结构力学问题是一个非常有效的工具,显式方法中的单个增量步取决于模型的最高固有频率,与持续时间、载荷类型无关。ABAQUS/Explicit主要用于碰撞、接触以及失效分析。探讨了ABAQUS显式动力学的基本理论、求解的问题,对显示动力学分析方法中的求解算法、稳定时间极限和能量平衡问题进行研究,给出了显示动力学分析的一般性分析方法。通过案例验证了该方法的可行性,应用该方法可有效解决实际工业生产中的碰撞问题、复杂的接触问题以及复杂的后屈曲问题,可为显式动力学分析方法应用于工程实践奠定理论与方法基础。 相似文献
37.
The identification rate of UHF RFID system was restricted by multipath propagation effects.The system identification performance was studied considering the correlation coefficient between forward and reverse channels.Based on the generalized Rician fading channel model,the analytical expression of identification rate was derived under independent,full correlation and correlation cases.Compared with the existing analysis,the proposed uniform calculation formula of identification rate was for any correlation coefficient and kinds of channel conditions.The numerical computation and Monte-carlo simulations show that the influences of different correlation coefficients,channel conditions,sensitivity and distance on the identification rate. 相似文献
38.
39.
Wang Qibin Zhao Bo Ma Hongbo Chang Jiantao Mao Gang 《Journal of Mechanical Science and Technology》2019,33(6):2561-2571
Journal of Mechanical Science and Technology - Real-time monitoring and rapid evaluation of bearing operating conditions, especially for the reliability evaluation and remaining useful life (RUL)... 相似文献
40.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献