全文获取类型
收费全文 | 54121篇 |
免费 | 6349篇 |
国内免费 | 2053篇 |
学科分类
工业技术 | 62523篇 |
出版年
2025年 | 436篇 |
2024年 | 2006篇 |
2023年 | 1931篇 |
2022年 | 2761篇 |
2021年 | 3713篇 |
2020年 | 2845篇 |
2019年 | 2168篇 |
2018年 | 1927篇 |
2017年 | 2115篇 |
2016年 | 1945篇 |
2015年 | 2524篇 |
2014年 | 2949篇 |
2013年 | 3316篇 |
2012年 | 3782篇 |
2011年 | 3872篇 |
2010年 | 3322篇 |
2009年 | 3125篇 |
2008年 | 3021篇 |
2007年 | 2720篇 |
2006年 | 2417篇 |
2005年 | 2130篇 |
2004年 | 1349篇 |
2003年 | 1021篇 |
2002年 | 919篇 |
2001年 | 786篇 |
2000年 | 713篇 |
1999年 | 609篇 |
1998年 | 399篇 |
1997年 | 351篇 |
1996年 | 315篇 |
1995年 | 242篇 |
1994年 | 205篇 |
1993年 | 122篇 |
1992年 | 106篇 |
1991年 | 78篇 |
1990年 | 56篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 25篇 |
1986年 | 32篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1959年 | 7篇 |
1953年 | 6篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
1.
郝建民 《导弹与航天运载技术》1997,(2)
推导证明了作为通信理论基石之一的采样定理及其公式存在着两个矛盾:内在不自洽性,即采样定理与其公式的推导前提条件相矛盾;采样定理在工程实际应用时的严重局限性 相似文献
2.
3.
A comprehensive study of P, As, and hybrid As/P nLDD junctions is presented in terms of performance, reliability, and manufacturability for the first time. It is found that As junctions limit the performance of deep submicron devices due to unacceptable hot-carrier reliability, whereas a hybrid junction (light dose P added to medium dose As) dramatically improves hot-carrier reliability while maintaining high performance and manufacturability. For Leff of 0.19 μm, using this hybrid junction in a manufacturing process, an inverter gate delay of 32 ps, dc hot carrier life time exceeding ten years, and off-state leakage below 30 pA/μm at 2.9 V have been achieved 相似文献
4.
It has been shown that coherent optical fiber receivers with a two-filter structure (TFS) consisting of a wide-band IF filter and a narrow-band postdetection filter are less susceptible to the influence of phase noise. However, the expanded IF bandwidth required to achieve optimum sensitivity performance is large, particularly in multichannel FSK systems. Forward error control coding can relax the laser linewidth requirement and improve receiver sensitivity. In this paper a multichannel asynchronous FSK scheme equipped with (31, k) Reed-Solomon codes is used to verify the coding benefit. A systematic error probability analysis is developed and a stable and accurate performance evaluation procedure is provided. The sensitivity penalties due to the combined phase noise and interchannel crosstalk for both coded and uncoded systems are calculated for comparison. The results show that the performance reduction due to phase noise can be largely alleviated by choosing a proper code rate and an optimum value of the expanded IF bandwidth 相似文献
5.
Trintinalia L.C. Bhalla R. Hao Ling 《Antennas and Propagation, IEEE Transactions on》1997,45(11):1664-1668
We present a scattering center extraction algorithm to parameterize the backscattered data from complex targets collected over large angular apertures. This parameterization is based on a scattering center model of the target, but includes an aspect-dependent amplitude function for each scattering center. A two-dimensional (2-D) adaptive Gaussian representation (AGR) algorithm is used to extract the position and the amplitude function associated with each scattering center. The algorithm is tested with data generated by the Xpatch radar simulation code as well as chamber measurement data. The results show that a very good compression ratio can be achieved, resulting in a compact scattering center model of the target. Once such model is available, we can easily reconstruct range profiles and ISAR images at any aspect on the same plane with good accuracy 相似文献
6.
Machine Learning - Research showed that deep learning models are vulnerable to membership inference attacks, which aim to determine if an example is in the training set of the model. We propose a... 相似文献
7.
Li Hongjian Wei Yaojun Xiong Yu Ma Enjie Tian Wenhong 《The Journal of supercomputing》2021,77(10):11575-11596
The Journal of Supercomputing - With the fast growth of big data applications, it has brought about a huge increase in the energy consumption for big data processing in Cloud data centers. In this... 相似文献
8.
Hao Ruiyang Lu Bingyu Cheng Ying Li Xiu Huang Biqing 《Journal of Intelligent Manufacturing》2021,32(7):1833-1843
Journal of Intelligent Manufacturing - With the advance in Industry 4.0, smart industrial monitoring has been proposed to timely discover faults and defects in industrial processes. Steel is widely... 相似文献
9.
心理资本前因变量研究 总被引:5,自引:0,他引:5
郝明亮 《重庆科技学院学报(社会科学版)》2010,(11):93-95
采用心理资本问卷对分别属于医药、建筑、水利工程、电信、通讯运营和服务行业的6家企业的员工进行了调查.根据对回收的283份有效问卷的统计分析,认为员工的性别、受教育程度和所在企业的性质对员工心理资本不会产生显著性影响,而员工年龄的影响显著,50岁以上员工的总体心理资本水平高于其他年龄段员工. 相似文献
10.
Wen Juan Zeng Hao Wang Yuzhu Liu Shurong Xue Yiming 《Multimedia Tools and Applications》2021,80(2):2517-2536
Multimedia Tools and Applications - Speech is one of the essential ways of communication. The study of speech steganography provides great value in information security. To improve imperceptibility... 相似文献