全文获取类型
收费全文 | 239254篇 |
免费 | 22907篇 |
国内免费 | 16030篇 |
专业分类
电工技术 | 35440篇 |
技术理论 | 24篇 |
综合类 | 27310篇 |
化学工业 | 10868篇 |
金属工艺 | 7759篇 |
机械仪表 | 19259篇 |
建筑科学 | 19086篇 |
矿业工程 | 8979篇 |
能源动力 | 8369篇 |
轻工业 | 4962篇 |
水利工程 | 6566篇 |
石油天然气 | 6730篇 |
武器工业 | 3874篇 |
无线电 | 23908篇 |
一般工业技术 | 12653篇 |
冶金工业 | 8524篇 |
原子能技术 | 2314篇 |
自动化技术 | 71566篇 |
出版年
2024年 | 556篇 |
2023年 | 3690篇 |
2022年 | 6475篇 |
2021年 | 7627篇 |
2020年 | 7464篇 |
2019年 | 5307篇 |
2018年 | 4528篇 |
2017年 | 5919篇 |
2016年 | 6977篇 |
2015年 | 8032篇 |
2014年 | 14933篇 |
2013年 | 12686篇 |
2012年 | 17264篇 |
2011年 | 18519篇 |
2010年 | 14130篇 |
2009年 | 14182篇 |
2008年 | 14519篇 |
2007年 | 18157篇 |
2006年 | 16293篇 |
2005年 | 14612篇 |
2004年 | 11944篇 |
2003年 | 10750篇 |
2002年 | 8245篇 |
2001年 | 6846篇 |
2000年 | 5621篇 |
1999年 | 4527篇 |
1998年 | 3433篇 |
1997年 | 2774篇 |
1996年 | 2481篇 |
1995年 | 2126篇 |
1994年 | 1743篇 |
1993年 | 1213篇 |
1992年 | 1024篇 |
1991年 | 718篇 |
1990年 | 590篇 |
1989年 | 498篇 |
1988年 | 351篇 |
1987年 | 210篇 |
1986年 | 151篇 |
1985年 | 127篇 |
1984年 | 111篇 |
1983年 | 99篇 |
1982年 | 76篇 |
1981年 | 72篇 |
1980年 | 57篇 |
1979年 | 54篇 |
1978年 | 37篇 |
1977年 | 35篇 |
1964年 | 31篇 |
1959年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
三维异质异构集成技术是实现电子信息系统向着微型化、高效能、高整合、低功耗及低成本方向发展的最重要方法,也是决定信息化平台中微电子和微纳系统领域未来发展的一项核心高技术。文章详细介绍了毫米波频段三维异质异构集成技术的优势、近年来的发展趋势以及面临的挑战。利用硅基MEMS 光敏复合薄膜多层布线工艺可实现异质芯片的低损耗互连,同时三维集成高性能封装滤波器、高辐射效率封装天线等无源元件,还能很好地处理布线间的电磁兼容和芯片间的屏蔽问题。最后介绍了一款新型毫米波三维异质异构集成雷达及其在远距离生命体征探测方面的应用。 相似文献
22.
23.
24.
为缓解我国水、能源和粮食资源紧张问题,促进资源可持续利用,构建水-能源-粮食系统,利用耦合协调度模型对我国的30个省(自治区、直辖市)进行测算,并利用空间杜宾模型分析主要影响因素。结果表明:2003—2017年,我国能源、粮食评价[JP]指数高于水资源评价指数,系统综合评价指数逐年递增;大部分省份耦合协调度处于初级协调水平且呈现逐年上升的态势,个别省份耦合协调度濒临失调;耦合协调度空间自相关性较强,虽有明显波动,但是呈现逐年加强的态势;影响耦合协调度的主要因素有从业人口数、固定资产投资额、人均生产总值、人口总数、[JP]文盲人口占比、工业污染排放、城镇化。 相似文献
25.
《Mechatronics》2022
A large-scale high-precision scan stage is important equipment in the industrial productions of micro-fabrication such as flat panel display (FPD) lithography systems. Designing controllers for multi-input multi-output (MIMO) systems is time-consuming and needs experience because of the interaction between each axis and many controller tuning parameters. The aim of this study is to develop a peak filter design method based on frequency response data to reduce repetitive disturbance. This data-based approach does not use the model and only uses the frequency response data of the controlled system and the disturbance spectrum calculated from the scanning error data (Contribution 1). The peak filter is designed by convex optimization and satisfies robust stability conditions for six-degree-of-freedom systems (Contribution 2). The control performance of the designed peak filter is experimentally demonstrated with an industrial MIMO large-scale high-precision scan stage in reducing the scanning error of the main stroke of the translation along the -axis (Contribution 3). 相似文献
26.
《International Journal of Hydrogen Energy》2022,47(67):29172-29183
To improve the safety of wet dust removal systems for processing magnesium-based alloys, a new method is proposed for preventing hydrogen generation. In this paper, hydrogen generation by Mg–Zn alloy dust was inhibited with six common metal corrosion inhibitors. The results showed that sodium dodecylbenzene sulfonate was the best hydrogen inhibitor, while CeCl3 enhanced hydrogen precipitation. The film-forming stability of sodium dodecylbenzene sulfonate was tested with different contents, temperatures, Cl? concentrations and perturbation rates. The results showed that this inhibitor formed stable protective films on the surfaces of Mg–Zn alloy particles, and adsorption followed the Langmuir adsorption model. 相似文献
27.
28.
《International Journal of Hydrogen Energy》2022,47(75):32303-32314
Membrane electrode assembly (MEA) is considered a key component of a proton exchange membrane fuel cell (PEMFC). However, developing a new MEA to meet desired properties, such as operation under low-humidity conditions without a humidifier, is a time- and cost-consuming process. This study employs a machine-learning-based approach using K-nearest neighbor (KNN) and neural networks (NN) in the MEA development process by identifying a suitable catalyst layer (CL) recipe in MEA. Minimum redundancy maximum relevance and principal component analysis were implemented to specify the most important predictor and reduce the data dimension. The number of predictors was found to play an essential role in the accuracy of the KNN and NN models although the predictors have self-correlations. The KNN model with a K of 7 was found to minimize the model loss with a loss of 11.9%. The NN model constructed by three corresponding hidden layers with nine, eight, and nine nodes can achieve the lowest error of 0.1293 for the Pt catalyst and 0.031 for PVA as a good additive blending in the CL of the MEA. However, even if the error is low, the prediction of PVA seems to be inaccurate, regardless of the model structure. Therefore, the KNN model is more appropriate for CL recipe prediction. 相似文献
29.
《International Journal of Hydrogen Energy》2022,47(84):35790-35809
PEMFC system is a complex new clean power system. Based on MATLAB/Simulink, this paper develops a system-level dynamic model of PEMFC, including the gas supply system, hydrogen supply system, hydrothermal management system, and electric stack. The neural network fits the electric stack model to the simulation data. The effects of different operating conditions on the PEMFC stack power and system efficiency are analyzed. Combining the power of the reactor and the system efficiency to define the integrated performance index, the particle swarm optimization (PSO) algorithm is introduced to optimize the power density and system efficiency of the PEMFC with multiple objectives. The final optimal operating point increases the power density and system efficiency by 1.33% and 12.8%, respectively, which maximizes the output performance and reduces the parasitic power. 相似文献
30.
Higher transmission rate is one of the technological features of prominently used wireless communication namely Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO–OFDM). One among an effective solution for channel estimation in wireless communication system, specifically in different environments is Deep Learning (DL) method. This research greatly utilizes channel estimator on the basis of Convolutional Neural Network Auto Encoder (CNNAE) classifier for MIMO-OFDM systems. A CNNAE classifier is one among Deep Learning (DL) algorithm, in which video signal is fed as input by allotting significant learnable weights and biases in various aspects/objects for video signal and capable of differentiating from one another. Improved performances are achieved by using CNNAE based channel estimation, in which extension is done for channel selection as well as achieve enhanced performances numerically, when compared with conventional estimators in quite a lot of scenarios. Considering reduction in number of parameters involved and re-usability of weights, CNNAE based channel estimation is quite suitable and properly fits to the video signal. CNNAE classifier weights updation are done with minimized Signal to Noise Ratio (SNR), Bit Error Rate (BER) and Mean Square Error (MSE). 相似文献