全文获取类型
收费全文 | 43257篇 |
免费 | 5303篇 |
国内免费 | 2001篇 |
专业分类
电工技术 | 11251篇 |
技术理论 | 3篇 |
综合类 | 2851篇 |
化学工业 | 4376篇 |
金属工艺 | 2467篇 |
机械仪表 | 1397篇 |
建筑科学 | 5567篇 |
矿业工程 | 1718篇 |
能源动力 | 1129篇 |
轻工业 | 1468篇 |
水利工程 | 1928篇 |
石油天然气 | 1848篇 |
武器工业 | 223篇 |
无线电 | 3411篇 |
一般工业技术 | 2730篇 |
冶金工业 | 1562篇 |
原子能技术 | 407篇 |
自动化技术 | 6225篇 |
出版年
2024年 | 147篇 |
2023年 | 420篇 |
2022年 | 935篇 |
2021年 | 1172篇 |
2020年 | 1225篇 |
2019年 | 1122篇 |
2018年 | 1002篇 |
2017年 | 1314篇 |
2016年 | 1476篇 |
2015年 | 1693篇 |
2014年 | 3233篇 |
2013年 | 2283篇 |
2012年 | 3242篇 |
2011年 | 3498篇 |
2010年 | 2701篇 |
2009年 | 2747篇 |
2008年 | 2506篇 |
2007年 | 3044篇 |
2006年 | 2889篇 |
2005年 | 2444篇 |
2004年 | 1996篇 |
2003年 | 1928篇 |
2002年 | 1677篇 |
2001年 | 1545篇 |
2000年 | 1230篇 |
1999年 | 907篇 |
1998年 | 573篇 |
1997年 | 404篇 |
1996年 | 324篇 |
1995年 | 269篇 |
1994年 | 157篇 |
1993年 | 100篇 |
1992年 | 80篇 |
1991年 | 48篇 |
1990年 | 40篇 |
1989年 | 37篇 |
1988年 | 48篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 22篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 2篇 |
1975年 | 4篇 |
1963年 | 1篇 |
1958年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Ya Gu Quanmin Zhu Hassan Nouri 《International Journal of Adaptive Control and Signal Processing》2022,36(1):138-154
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results. 相似文献
3.
4.
基于神经网络和遗传算法的锭子弹性管性能优化 总被引:1,自引:0,他引:1
为得到减振弹性管对下锭胆的支承弹性和锭子高速运动下的稳定性等性能的最优匹配效率,依据减振弹性管的等效抗弯刚度及底部等效刚度系数公式,利用MatLab数值分析软件构建弹性管抗弯刚度和底部挠度数学模型。首先,结合Isight优化软件基于径向基神经网络构建其近似模型,且使精度达到可接受水平,并以模型的关键结构参数弹性模量、螺距、槽宽、壁厚为设计变量,结合遗传算法对弹性管抗弯刚度和底部挠度进行多目标优化设计,得到Pareto最优解集和Pareto前沿图,确定出减振弹性管结构工艺参数的优化方案。通过对优化数据进行分析发现,该方案在保证减振弹性管弹性的同时,其底部振幅明显减弱。 相似文献
5.
The existing analytical average bit error rate (ABER) expression of conventional generalised spatial modulation (CGSM) does not agree well with the Monte Carlo simulation results in the low signal‐to‐noise ratio (SNR) region. Hence, the first contribution of this paper is to derive a new and easy way to evaluate analytical ABER expression that improves the validation of the simulation results at low SNRs. Secondly, a novel system termed CGSM with enhanced spectral efficiency (CGSM‐ESE) is presented. This system is realised by applying a rotation angle to one of the two active transmit antennas. As a result, the overall spectral efficiency is increased by 1 bit/s/Hz when compared with the equivalent CGSM system. In order to validate the simulation results of CGSM‐ESE, the third contribution is to derive an analytical ABER expression. Finally, to improve the ABER performance of CGSM‐ESE, three link adaptation algorithms are developed. By assuming full knowledge of the channel at the receiver, the proposed algorithms select a subset of channel gain vector (CGV) pairs based on the Euclidean distance between all CGV pairs, CGV splitting, CGV amplitudes, or a combination of these. 相似文献
6.
冯鹏一 《信息通信技术与政策》2020,(1):12-15
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。 相似文献
7.
8.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015 相似文献
9.
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
10.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献