全文获取类型
收费全文 | 207206篇 |
免费 | 12863篇 |
国内免费 | 7379篇 |
专业分类
电工技术 | 9896篇 |
技术理论 | 11篇 |
综合类 | 11486篇 |
化学工业 | 30432篇 |
金属工艺 | 11801篇 |
机械仪表 | 11111篇 |
建筑科学 | 12774篇 |
矿业工程 | 4653篇 |
能源动力 | 4674篇 |
轻工业 | 12037篇 |
水利工程 | 3970篇 |
石油天然气 | 7790篇 |
武器工业 | 1423篇 |
无线电 | 23543篇 |
一般工业技术 | 29612篇 |
冶金工业 | 8251篇 |
原子能技术 | 1813篇 |
自动化技术 | 42171篇 |
出版年
2024年 | 598篇 |
2023年 | 2120篇 |
2022年 | 4029篇 |
2021年 | 5609篇 |
2020年 | 4197篇 |
2019年 | 3385篇 |
2018年 | 17756篇 |
2017年 | 17280篇 |
2016年 | 13503篇 |
2015年 | 5889篇 |
2014年 | 6952篇 |
2013年 | 8042篇 |
2012年 | 12197篇 |
2011年 | 18814篇 |
2010年 | 16731篇 |
2009年 | 13594篇 |
2008年 | 14605篇 |
2007年 | 15070篇 |
2006年 | 7321篇 |
2005年 | 7339篇 |
2004年 | 5203篇 |
2003年 | 4382篇 |
2002年 | 3434篇 |
2001年 | 2764篇 |
2000年 | 2817篇 |
1999年 | 2601篇 |
1998年 | 1898篇 |
1997年 | 1614篇 |
1996年 | 1477篇 |
1995年 | 1289篇 |
1994年 | 1010篇 |
1993年 | 753篇 |
1992年 | 615篇 |
1991年 | 459篇 |
1990年 | 396篇 |
1989年 | 280篇 |
1988年 | 236篇 |
1987年 | 143篇 |
1986年 | 138篇 |
1985年 | 74篇 |
1984年 | 52篇 |
1982年 | 45篇 |
1968年 | 43篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1959年 | 45篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Revisiting the medical and social models of disability, this study adopted the integrated biopsychosocial approach to examine experiences of 25 mobility‐impaired respondents in Singapore with using mobile phones. We found that mobile phones provided respondents a greater degree of mobility, a sense of control, and opportunities to escape the stigma of disability, thus challenging the boundaries between the able‐bodied and the disabled. Mobile phone appropriation allowed the management of personal identities and social networks, leading to a sense of empowerment. However, mobile phone usage might act as a double‐edged sword for disabled people, creating mobile dependencies and a spatial narrowing of social connections. Theoretical and practical implications are discussed. 相似文献
992.
针对复杂工业系统动态非线性故障检测过程精度低和计算量大的问题,提出了一种改进的动态核主元分析故障检测方法,该方法首先利用不可区分度剔除相关程度较小或者不相关变量,减少数据量,然后通过观测值扩展对筛选后的新数据构建增广矩阵,并对矩阵使用核主元分析提取变量数据的非线性空间相关特征,最后通过监测T 2和SPE 两种统计量诊断出系统发生故障及识别故障变量。仿真实验证明,该方法能对风力发电机故障进行有效监测和诊断,与KPCA方法相比,改进的动态核主元分析方法对微小故障更为敏感。 相似文献
993.
An efficient multiobjective differential evolution algorithm for array synthesis is proposed in this article. By introducing novel strategies in the generalized differential evolution (GDE3), the proposed algorithm can generate a better converged and distributed Pareto front than the standard GDE3. Five typical benchmark functions are optimized by the proposed improved GDE3 (IGDE) to verify its effectiveness. Furthermore, the proposed algorithm is applied in two‐pattern synthesis problems, including an unequal spaced linear array and a conformal array. The superior performance of the proposed IGDE demonstrates that it is an efficient and competitive algorithm in the function optimization, pattern synthesis, and other electromagnetic problems. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:161–169, 2014. 相似文献
994.
995.
Commutative Encryption and Watermarking (CEW) is a technology combined with encryption and watermarking, which is used for providing comprehensive security protection for multimedia information. This paper presents a novel CEW scheme based on orthogonal decomposition. Different from current CEW, the proposed CEW not only achieves the integration of encryption and watermarking in the final data but also has no specific restrictions in selecting encryption and watermarking algorithms. Therefore, the proposed CEW possesses higher security and applicability. Experimental results demonstrate that the proposed CEW can keep the performances of selected encryption and watermarking algorithm and show more robustness than other current CEW schemes. 相似文献
996.
This paper aims to optimize the content-aware prioritization of scalable video multicast, which is coupled with multipath streaming and network coding based routing. It constructs multiple layer distribution meshes for the scalable video stream to minimize the total video distortion at all the receivers, determines the base layer meshes with minimum costs to maintain application-layer QoS and the layer synchronization of SVC streaming, and improves the network throughput by encouraging path-overlapping transmissions and thus allowing bandwidth sharing among different receivers for the same video layer by utilizing network coding. The targeted problem is formulated into a minimization programming in which the quality variation between layers, the transmission cost of the base layer, as well as the efficient resource utilization are jointly considered. By decomposition and dual approach, the global convex problem is solved by a two-level decentralized iterative algorithm. The implementation of the distributed algorithm is discussed with regard to the communication overhead, and the convergence performance is validated by numerical experiments. Packet-level simulations demonstrate that the proposed algorithm could approximately achieve the maximum flow rates determined by Max-Flow Min-Cut Theorem and benefit the overall received video quality. 相似文献
997.
Marwa A. Abd El-Fattah Moawad I. Dessouky Alaa M. Abbas Salaheldin M. Diab El-Sayed M. El-Rabaie Waleed Al-Nuaimy Saleh A. Alshebeili Fathi E. Abd El-samie 《International Journal of Speech Technology》2014,17(1):53-64
This paper proposes an adaptive Wiener filtering method for speech enhancement. This method depends on the adaptation of the filter transfer function from sample to sample based on the speech signal statistics; the local mean and the local variance. It is implemented in the time domain rather than in the frequency domain to accommodate for the time-varying nature of the speech signals. The proposed method is compared to the traditional frequency-domain Wiener filtering, spectral subtraction and wavelet denoising methods using different speech quality metrics. The simulation results reveal the superiority of the proposed Wiener filtering method in the case of Additive White Gaussian Noise (AWGN) as well as colored noise. 相似文献
998.
999.
随着社会的快速发展,建筑工程施工随处可见,工程规模也越来越大.因此,开展有效的建筑工程施工管理是十分重要的.通过分析实际建筑施工管理中遇到的问题,提出了相应的解决措施. 相似文献
1000.
针对扫描的人脑组织MR图像边缘分辨率低、模糊性大的特点,本文提出了一种基于模糊Markov随机场和Gaussian曲线相结合的MR图像最佳阈值分割方法。该方法通过对图像的像素邻域属性的统计将模糊论引入其中,建立模糊Markov随机场,并利用Gaussian曲线对二维直方图最佳一维投影进行拟合,确定出图像中各脑组织的二维阈值点,在二维直方图上实现对脑组织的分割。通过实验表明,本算法能够有效提高脑组织的分辨率,对噪声的鲁棒性、结果区域的连通性相对于一维Otsu和二维Otsu算法都有了很大的提高。 相似文献