全文获取类型
收费全文 | 114738篇 |
免费 | 19964篇 |
国内免费 | 4557篇 |
专业分类
电工技术 | 7000篇 |
技术理论 | 2篇 |
综合类 | 6014篇 |
化学工业 | 27337篇 |
金属工艺 | 5279篇 |
机械仪表 | 6035篇 |
建筑科学 | 7159篇 |
矿业工程 | 2220篇 |
能源动力 | 3363篇 |
轻工业 | 12161篇 |
水利工程 | 2177篇 |
石油天然气 | 3513篇 |
武器工业 | 1016篇 |
无线电 | 15786篇 |
一般工业技术 | 19146篇 |
冶金工业 | 4293篇 |
原子能技术 | 974篇 |
自动化技术 | 15784篇 |
出版年
2024年 | 276篇 |
2023年 | 937篇 |
2022年 | 1957篇 |
2021年 | 3068篇 |
2020年 | 3483篇 |
2019年 | 4669篇 |
2018年 | 4861篇 |
2017年 | 5589篇 |
2016年 | 5907篇 |
2015年 | 6863篇 |
2014年 | 7756篇 |
2013年 | 9548篇 |
2012年 | 8565篇 |
2011年 | 8503篇 |
2010年 | 8423篇 |
2009年 | 8085篇 |
2008年 | 7576篇 |
2007年 | 7052篇 |
2006年 | 6358篇 |
2005年 | 5285篇 |
2004年 | 4380篇 |
2003年 | 4111篇 |
2002年 | 4200篇 |
2001年 | 3679篇 |
2000年 | 2662篇 |
1999年 | 1615篇 |
1998年 | 805篇 |
1997年 | 681篇 |
1996年 | 552篇 |
1995年 | 405篇 |
1994年 | 315篇 |
1993年 | 235篇 |
1992年 | 157篇 |
1991年 | 129篇 |
1990年 | 110篇 |
1989年 | 87篇 |
1988年 | 63篇 |
1987年 | 63篇 |
1986年 | 37篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 27篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
W. Lim C. K. Wang 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):568-572
The one-dimensional (1D) position-sensitive superheated-liquid-droplet dosimeter (SLDD) has been fabricated and tested in the laboratory. The 1D SLDD is fabricated from a 9.525-mm OD, 6.35-mm ID, 20-cm long, Plexiglas-walled tube filled with a mixture of superheated-liquid Freon droplets and host medium glycerol. Washer-shaped piezoelectric acoustic transducers are positioned at both ends of the tube; they determine the number and positions of the acoustic events when the superheated-liquid droplets evaporate upon neutron irradiation. The SLDD is irradiated with the 137Cs and 60Co γ-sources, as well as 252Cf neutron source to test for its radiation response and spatial resolution. The SLDD based on the Freon-134a superheated-liquid droplets operating at 20°C and 1 atm is found to be ideal for measuring absorbed neutron dose. This study also proves that the positions of the radiation-induced nucleation acoustic events can be linearly determined from the differences in the transmission times received by the acoustic transducers on the 1D SLDD. The spatial resolution of the neutron depth-dose is 1 mm due the finite response time (1 μs) of the piezoelectric acoustic transducers. 相似文献
33.
34.
The effect of high oxide field stress is studied using capacitance-time (C-t) measurements of MOS capacitors. The stress results in parallel shifts of the C-t curve along the time axis. The flatband voltage shift ΔVFB obtained from the initial deep depletion capacitance C(t=0+) follows the same trend as that from the high-frequency C-V characteristics. However, the discrepancy between the two flatband voltages becomes larger as the stress increases due to the effect of interface charges on C-t characteristics. The flatband voltage difference is converted to interface trap density, showing a steady increase of interface trap density with stress, similar to that from low-frequency C-V measurements 相似文献
35.
Ki Hyun Kim Yong Hoon Kang Byoungho Lee 《Photonics Technology Letters, IEEE》1997,9(12):1610-1612
A photorefractive volume hologram was recorded and probed using light diffracted from a tapered optical fiber as a reference beam. A single-mode fiber (SMF) was chemically etched and tapered to give a complicated beam pattern, and it is shown that the tapered optical fiber can be utilized to increase the storage density of the volume hologram. Spatial selectivity of the volume hologram with this method was increased by two times compared to the normal SMF referencing, which is due to the fact that the complicated beam pattern has little correlation with its shifted version 相似文献
36.
制作压力传感器时,在二氧化硅层上淀积多晶硅膜,既可利用优良的机械特性,又可保证压敏电阻与衬底间具有良好的绝缘性,由此可大大提高器件的温度特性。介绍了一种多晶硅压力传感器的原理和设计。实验结果表明,这类传感器具有灵敏度好,精度高等特点,电路工作范围为0-250℃,且具有良好的温度稳定性。 相似文献
37.
38.
Delay-dependent state estimation for delayed neural networks 总被引:3,自引:0,他引:3
Yong He Qing-Guo Wang Min Wu Chong Lin 《Neural Networks, IEEE Transactions on》2006,17(4):1077-1081
In this letter, the delay-dependent state estimation problem for neural networks with time-varying delay is investigated. A delay-dependent criterion is established to estimate the neuron states through available output measurements such that the dynamics of the estimation error is globally exponentially stable. The proposed method is based on the free-weighting matrix approach and is applicable to the case that the derivative of a time-varying delay takes any value. An algorithm is presented to compute the state estimator. Finally, a numerical example is given to demonstrate the effectiveness of this approach and the improvement over existing ones. 相似文献
39.
40.