全文获取类型
收费全文 | 22512篇 |
免费 | 2341篇 |
国内免费 | 1795篇 |
专业分类
电工技术 | 1485篇 |
技术理论 | 1篇 |
综合类 | 3231篇 |
化学工业 | 1092篇 |
金属工艺 | 279篇 |
机械仪表 | 1440篇 |
建筑科学 | 1693篇 |
矿业工程 | 469篇 |
能源动力 | 496篇 |
轻工业 | 1026篇 |
水利工程 | 576篇 |
石油天然气 | 444篇 |
武器工业 | 187篇 |
无线电 | 1806篇 |
一般工业技术 | 2372篇 |
冶金工业 | 814篇 |
原子能技术 | 136篇 |
自动化技术 | 9101篇 |
出版年
2024年 | 26篇 |
2023年 | 191篇 |
2022年 | 336篇 |
2021年 | 454篇 |
2020年 | 593篇 |
2019年 | 586篇 |
2018年 | 523篇 |
2017年 | 753篇 |
2016年 | 873篇 |
2015年 | 898篇 |
2014年 | 1593篇 |
2013年 | 1579篇 |
2012年 | 1866篇 |
2011年 | 1702篇 |
2010年 | 1412篇 |
2009年 | 1588篇 |
2008年 | 1515篇 |
2007年 | 1633篇 |
2006年 | 1351篇 |
2005年 | 1186篇 |
2004年 | 917篇 |
2003年 | 813篇 |
2002年 | 639篇 |
2001年 | 616篇 |
2000年 | 483篇 |
1999年 | 398篇 |
1998年 | 306篇 |
1997年 | 249篇 |
1996年 | 206篇 |
1995年 | 225篇 |
1994年 | 185篇 |
1993年 | 154篇 |
1992年 | 121篇 |
1991年 | 103篇 |
1990年 | 108篇 |
1989年 | 101篇 |
1988年 | 73篇 |
1987年 | 45篇 |
1986年 | 36篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1963年 | 9篇 |
1961年 | 8篇 |
1957年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
3.
Xufen Xie Yingying Shang Jieyu Zhu Ningfang Liao Wenmin Wu Jing Liang Chaoqun Fu 《Color research and application》2021,46(1):65-74
Reconstruction of spectral information based on multi‐channel image system is a significant problem in color reproduction, detection, and recognition. A spectral radiance reconstruction from trichromatic digital camera responses is researched in this article. The mapping relationship between the trichromatic imaging system response and the incident spectral radiance is analyzed. Then, in order to remove the ill‐posedness of the problem, a regularized constraint solution model of spectral radiance reconstruction matrix is established. And the spectral radiance can be reconstructed by spectral radiance reconstruction matrices and trichromatic imaging system response. Finally, the spectral radiance reconstruction matrix is estimated by the system radiometric calibration experiment. The input radiance is offered by a LCD display. A 3‐factor and 9‐level orthogonal test is designed for the calibration experiment, and a test set of 24 colors is used for precision analysis. The results show that the average relative mean error of our method is 8.69%, it is lower than that of Wiener filtering method by 2.84%. The method can reconstruct spectral radiance information effectively. 相似文献
4.
针对货运车辆在配送调度过程中产生大量碳排放的问题,建立模型将多种影响碳排放量的因素协同优化。模型中考虑了不同载重量的异质车队,两个节点之间有多条道路的柔性路径,以及车辆重量随卸货而减少的动态负载等因素,以碳排放量、行驶时间和行驶路程为优化目标,并加入了节点需求时间窗、根据速度变化划分路段、交接和卸货时间的约束。提出了一种混合蚁群算法,利用蚁群算法信息素强度更新方式保持群体记忆性,利用粒子群算法的快速收敛特性增加计算效率。通过随机数值算例的仿真优化与对比分析,验证了算法和模型的有效性。 相似文献
5.
This paper presents a control design for the one‐phase Stefan problem under actuator delay via a backstepping method. The Stefan problem represents a liquid‐solid phase change phenomenon which describes the time evolution of a material's temperature profile and the interface position. The actuator delay is modeled by a first‐order hyperbolic partial differential equation (PDE), resulting in a cascaded transport‐diffusion PDE system defined on a time‐varying spatial domain described by an ordinary differential equation (ODE). Two nonlinear backstepping transformations are utilized for the control design. The setpoint restriction is given to guarantee a physical constraint on the proposed controller for the melting process. This constraint ensures the exponential convergence of the moving interface to a setpoint and the exponential stability of the temperature equilibrium profile and the delayed controller in the norm. Furthermore, robustness analysis with respect to the delay mismatch between the plant and the controller is studied, which provides analogous results to the exact compensation by restricting the control gain. 相似文献
6.
This article is concerned with the polynomial filtering problem for a class of nonlinear stochastic systems governed by the Itô differential equation. The system under investigation involves polynomial nonlinearities, unknown‐but‐bounded disturbances, and state‐ and disturbance‐dependent noises ((x,d)‐dependent noises for short). By expanding the polynomial nonlinear functions in Taylor series around the state estimate, a new polynomial filter design method is developed with hope to reduce the conservatism of the existing results. In virtue of stochastic analysis and inequality technique, sufficient conditions in terms of parameter‐dependent linear matrix inequalities (PDLMIs) are derived to guarantee that the estimation error system is input‐to‐state stable in probability. Moreover, the desired polynomial matrix can be obtained by solving the PDLMIs via the sum‐of‐squares approach. The effectiveness and applicability of the proposed method are illustrated by two numerical examples with one concerning the permanent magnet synchronous motor. 相似文献
7.
In this article, an analytical technique is introduced to obtain the excitation coefficients of uniformly spaced linear antenna arrays in order to achieve a desired array factor. By integration of the prescribed array factor, the array factor dependency to the progressive phase shift is eliminated. A new system of linear equations is consequently obtained whose solution represents the excitation coefficients of the array. Some examples are presented to verify the accuracy of the introduced method. The performance of this strategy is compared with those obtained by the other well‐known techniques such as Woodward‐Lawson and Fourier transform. It is shown that the presented method estimates the desired array pattern with a very good precision. 相似文献
8.
ABSTRACT Incomplete pairwise comparison matrices offer a natural way of expressing preferences in decision-making processes. Although ordinal information is crucial, there is a bias in the literature: cardinal models dominate. Ordinal models usually yield nonunique solutions; therefore, an approach blending ordinal and cardinal information is needed. In this work, we consider two cascading problems: first, we compute ordinal preferences, maximizing an index that combines ordinal and cardinal information; then, we obtain a cardinal ranking by enforcing ordinal constraints. Notably, we provide a sufficient condition (that is likely to be satisfied in practical cases) for the first problem to admit a unique solution and we develop a provably polynomial-time algorithm to compute it. The effectiveness of the proposed method is analyzed and compared with respect to other approaches and criteria at the state of the art. 相似文献
9.
The airline industry is a representative industry with high cost and low profitability. Therefore, airlines should carefully plan their schedules to ensure that overall profit is maximized. We review the literature on airline planning and scheduling and focus on mathematical formulations and solution methodologies. Our research framework is anchored on three major problems in the airline scheduling, namely, fleet assignment, aircraft routing, and crew scheduling. General formulation, widely used solution approaches, and important extensions are presented for each problem and integrated problems. We conclude the review by identifying promising areas for further research. 相似文献
10.