全文获取类型
收费全文 | 52912篇 |
免费 | 8740篇 |
国内免费 | 5243篇 |
专业分类
电工技术 | 5672篇 |
技术理论 | 2篇 |
综合类 | 4531篇 |
化学工业 | 3166篇 |
金属工艺 | 1037篇 |
机械仪表 | 3603篇 |
建筑科学 | 2120篇 |
矿业工程 | 1059篇 |
能源动力 | 1008篇 |
轻工业 | 4401篇 |
水利工程 | 494篇 |
石油天然气 | 1207篇 |
武器工业 | 773篇 |
无线电 | 11210篇 |
一般工业技术 | 3332篇 |
冶金工业 | 968篇 |
原子能技术 | 482篇 |
自动化技术 | 21830篇 |
出版年
2024年 | 545篇 |
2023年 | 1521篇 |
2022年 | 2516篇 |
2021年 | 2713篇 |
2020年 | 2608篇 |
2019年 | 2032篇 |
2018年 | 1741篇 |
2017年 | 2247篇 |
2016年 | 2385篇 |
2015年 | 2709篇 |
2014年 | 4224篇 |
2013年 | 3564篇 |
2012年 | 4429篇 |
2011年 | 4660篇 |
2010年 | 3493篇 |
2009年 | 3430篇 |
2008年 | 3446篇 |
2007年 | 3777篇 |
2006年 | 3082篇 |
2005年 | 2587篇 |
2004年 | 2000篇 |
2003年 | 1617篇 |
2002年 | 1211篇 |
2001年 | 879篇 |
2000年 | 725篇 |
1999年 | 548篇 |
1998年 | 436篇 |
1997年 | 324篇 |
1996年 | 303篇 |
1995年 | 230篇 |
1994年 | 158篇 |
1993年 | 127篇 |
1992年 | 118篇 |
1991年 | 100篇 |
1990年 | 83篇 |
1989年 | 42篇 |
1988年 | 49篇 |
1987年 | 26篇 |
1986年 | 31篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Barrett Lisa Feldman; Quigley Karen S.; Bliss-Moreau Eliza; Aronson Keith R. 《Canadian Metallurgical Quarterly》2004,87(5):684
People differ in the extent to which they emphasize feelings of activation or deactivation in their verbal reports of experienced emotion, termed arousal focus (AF). Two multimethod studies indicate that AF is linked to heightened interoceptive sensitivity (as measured by performance on a heartbeat detection task). People who were more sensitive to their heartbeats emphasized feelings of activation and deactivation when reporting their experiences of emotion over time more than did those who were less sensitive. This relationship was not accounted for by several other variables, including simple language effects. Implications for the role of interoception in experienced emotion and the validity of self-reported emotion are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
33.
34.
European intercomparison on electron spin resonance identification of irradiated foodstuffs 总被引:1,自引:0,他引:1
J. RAFFI † M. H. STEVENSON M. KENT J. M. THIERY J.-J. BELLIARDO 《International Journal of Food Science & Technology》1992,27(2):111-124
The results of a co-trial organized by the Community Bureau of Reference on the use of Electron Spin Resonance spectroscopy for the identification of irradiated food in 21 laboratories are presented. The trial was qualitative on beef and trout bones, sardine scales, pistachio nut shells, dried grapes, and papaya, and quantitative on poultry bones. There was no difficulty in identifying irradiated meat bones, dried grapes, and papaya. In the case of fish bones there is a need for further kinetic study on different species. Identification of irradiation in pistachio nuts is more complicated and additional research is needed before further trials. All laboratories were able to distinguish between chicken bones irradiated at 1 to 3 kGy or 7 to 10 kGy although there was a partial overlap between the results. 相似文献
35.
Detection of multiple cracks using frequency measurements 总被引:2,自引:0,他引:2
D.P. Patil 《Engineering Fracture Mechanics》2003,70(12):1553-1572
A method for detection of multiple open cracks in a slender Euler-Bernoulli beams is presented based on frequency measurements. The method is based on the approach given by Hu and Liang [J. Franklin Inst. 330 (5) (1993) 841], transverse vibration modelling through transfer matrix method and representation of a crack by rotational spring. The beam is virtually divided into a number of segments, which can be decided by the analyst, and each of them is considered to be associated with a damage parameter. The procedure gives a linear relationship explicitly between the changes in natural frequencies of the beam and the damage parameters. These parameters are determined from the knowledge of changes in the natural frequencies. After obtaining them, each is treated in turn to exactly pinpoint the crack location in the segment and determine its size. The forward, or natural frequency determination, problems are examined in the passing. The method is approximate, but it can handle segmented beams, any boundary conditions, intermediate spring or rigid supports, etc. It eliminates the need for any symbolic computation which is envisaged by Hu and Liang [J. Franklin Inst. 330 (5) (1993) 841] to obtain mode shapes of the corresponding uncracked beams. The proposed method gives a clear insight into the whole analysis. Case studies (numerical) are presented to demonstrate the method effectiveness for two simultaneous cracks of size 10% and more of section depth. The differences between the actual and predicted crack locations and sizes are less than 10% and 15% respectively. The numbers of segments into which the beam is virtually divided limits the maximum number of cracks that can be handled. The difference in the forward problem is less than 5%. 相似文献
36.
37.
Multi-User MIMO Mobile CDMA Uplink System Employing Turbo Coding and Joint Detection Through a Multipath Rayleigh Fading Channel 总被引:1,自引:1,他引:0
Yasmine A. Fahmy Hebat-Allah M. Mourad Emad K. Al-Hussaini 《Wireless Personal Communications》2006,38(3):325-341
In this paper, a generalized multiple-input multiple-output (MIMO) antenna system that can be fitted to the uplink of a wireless communication system is considered for the general case of multi-user. At the transmitter, the information bits are Turbo coded, then interleaved and passed through a serial-to-parallel converter. The channel is assumed bad urban suffering from multipath Rayleigh fading resulting in inter-symbol and multiple access interferences (ISI and MAI). At the front-end of the receiver, a number of receiving antennas are used followed by a joint multi-user estimator based on the Minimum Mean Square Error Block Linear Equalizer (MMSE-BLE).Computer simulations demonstrate a significant performance improvement in both single user and multi-user cases.This paper depends in parts on that presented at the 11th European Wireless Conference, Cyprus, Nicosia, pp. 187–192, April 2005.
Yasmine A. Fahmy was born in Guiza, Egypt, on June 4, 1976. She received the B.Sc., M.Sc. and Ph.D. degrees in Communication and Electronics engineering from Cairo University, Egypt on 1999, 2001 and 2005 respectively. She is presently an assistant professor at Cairo University, Egypt. Her current field of interest is wireless communication and channel estimation.
Hebat-Allah M. Mourad received her B.Sc., M. Sc. and Ph.D. degrees in electrical communication engineering from Cairo University, Egypt, in 1983, 1987 and 1994 respectively. Since 1983, she has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently associate professor there. Her research interests include optical fiber communications, mobile and satellite communications.
Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London, UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding engineering research. He has written several papers for technical international journals and conferences. His research interests include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is a senior member of IEEE. He is listed in Marquis Whos Who in the World and in the IBC (International Biographical Center, Cambridge) for outstanding people of the 20th century. 相似文献
38.
主要论述了采用图像边缘检测和图像跟踪算法对采集的关节镜图像进行图像处理和分析的过程。在图像处理的基础上,系统自动测量出指定目标的形状参数,实现了系统的测量要求。本研究为实现关节镜手术过程图像的保存和手术的准确性提供了可行的方法。 相似文献
39.
40.
Fault-based side channel cryptanalysis is very effective against symmetric and asymmetric encryption algorithms. Although straightforward hardware and time redundancy based concurrent error detection (CED) architectures can be used to thwart such attacks, they entail significant overhead (either area or performance). In this paper we investigate two systematic approaches to low-cost, low-latency CED for symmetric encryption algorithm RC6. The proposed techniques have been validated on FPGA implementations of RC6, one of the advanced encryption standard finalists. 相似文献