全文获取类型
收费全文 | 13288篇 |
免费 | 1476篇 |
国内免费 | 356篇 |
专业分类
电工技术 | 632篇 |
综合类 | 499篇 |
化学工业 | 2967篇 |
金属工艺 | 561篇 |
机械仪表 | 740篇 |
建筑科学 | 585篇 |
矿业工程 | 186篇 |
能源动力 | 622篇 |
轻工业 | 1329篇 |
水利工程 | 152篇 |
石油天然气 | 366篇 |
武器工业 | 64篇 |
无线电 | 1872篇 |
一般工业技术 | 2435篇 |
冶金工业 | 482篇 |
原子能技术 | 186篇 |
自动化技术 | 1442篇 |
出版年
2024年 | 28篇 |
2023年 | 172篇 |
2022年 | 348篇 |
2021年 | 488篇 |
2020年 | 386篇 |
2019年 | 445篇 |
2018年 | 445篇 |
2017年 | 483篇 |
2016年 | 581篇 |
2015年 | 530篇 |
2014年 | 806篇 |
2013年 | 912篇 |
2012年 | 961篇 |
2011年 | 1138篇 |
2010年 | 905篇 |
2009年 | 817篇 |
2008年 | 747篇 |
2007年 | 691篇 |
2006年 | 577篇 |
2005年 | 539篇 |
2004年 | 412篇 |
2003年 | 395篇 |
2002年 | 402篇 |
2001年 | 384篇 |
2000年 | 288篇 |
1999年 | 250篇 |
1998年 | 206篇 |
1997年 | 144篇 |
1996年 | 101篇 |
1995年 | 111篇 |
1994年 | 81篇 |
1993年 | 67篇 |
1992年 | 59篇 |
1991年 | 34篇 |
1990年 | 32篇 |
1989年 | 37篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Single-crystalline 3C-SiC nanowires have been synthesized in large scale through a one-step autoclave route by the reaction of SiCl4, (C5H5)2Fe and metallic Na at 500 °C. Electron microscopy investigations show that the nanowires have typical diameters of 15-50 nm, lengths up to several tens of micrometers and grow along the [111] direction. The possible growth mechanism of the nanowires is discussed. 相似文献
62.
Sanghyun Ju Jianye Li Pimparkar N. Alam M.A. Chang R.P.H. Janes D.B. 《Nanotechnology, IEEE Transactions on》2007,6(3):390-395
Nanorod field-effect transistors (FETs) that use multiple Mg-doped ZnO nanorods and a SiO2 gate insulator were fabricated and characterized. The use of multiple nanorods provides higher on-currents without significant degradation in threshold voltage shift and subthreshold slopes. It has been observed that the on-currents of the multiple ZnO nanorod FETs increase approximately linearly with the number of nanorods, with on-currents of ~1 muA per nanorod and little change in off-current (~4times10-12). The subthreshold slopes and on-off ratios typically improve as the number of nanorods within the device channel is increased, reflecting good uniformity of properties from nanorod to nanorod. It is expected that Mg dopants contribute to high n-type semiconductor characteristics during ZnO nanorod growth. For comparison, nonintentionally doped ZnO nanorod FETs are fabricated, and show low conductivity to compare with Mg-doped ZnO nanorods. In addition, temperature-dependent current-voltage characteristics of single ZnO nanorod FETs indicate that the activation energy of the drain current is very low (0.05-0.16 eV) at gate voltages both above and below threshold 相似文献
63.
This paper proposes a new LDMOSFET structure with a trenched sinker for high‐power RF amplifiers. Using a low‐temperature, deep‐trench technology, we succeeded in drastically shrinking the sinker area to one‐third the size of the conventional diffusion‐type structure. The RF performance of the proposed device with a channel width of 5 mm showed a small signal gain of 16.5 dB and a maximum peak power of 32 dBm with a power‐added efficiency of 25% at 2 GHz. Furthermore, the trench sinker, which was applied to the guard ring to suppress coupling between inductors, showed an excellent blocking performance below ?40 dB at a frequency of up to 20 GHz. These results confirm that the proposed trenched sinker should be an effective technology both as a compact sinker for RF power devices and as a guard ring against coupling. 相似文献
64.
We propose an efficient scheme for camera motion characterization in MPEG‐compressed video. The proposed scheme detects six types of basic camera motions through threshold‐based qualitative interpretation, in which fixed thresholds are applied to motion model parameters estimated from MPEG motion vectors (MVs). The efficiency and robustness of the scheme are validated by the experiment with real compressed video sequences. 相似文献
65.
Munhyoung Cho Chong Hyun Lee Soohong Kim Joohwan Chun 《AEUE-International Journal of Electronics and Communications》2004,58(4):299-301
In this paper, we propose a new robust code division multiple access (CDMA) receiver of which weight vector is obtained by projecting the effective spatio-temporal signature waveform onto the signal subspace of the data covariance matrix. We verified our proposed algorithm by the field measured data obtained with a custom-built wideband CDMA test-bed. It will be shown that the proposed algorithm is robust to the signal mismatch. 相似文献
66.
67.
68.
根据计算机的辅助分析,采用新的钢锭传搁、注后强制水冷却、垫铁脱模等工艺后,入炉钢锭的热焓已超过开坯轧制需要,利用普通均热炉代替钢锭保温车,可完全依靠到钢锭自身潜热与显热进行均热。对不同锭型与钢种采用经试验的最佳时间均热后再轧制,收与保温车均热钢锭直接轧制相同的效果。 相似文献
69.
Senior nursing students described their interactions with faculty in a journal writing assignment. These interactions were categorized by the ethical perspectives of justice, autonomy, beneficence, and caring. An ethical analysis of faculty-student interactions is a strategy that may help nursing faculty and students understand differing perceptions about their relationships. 相似文献
70.
A quartz microbalance technique has been used to study the growth of4He and H2 adsorbed on sodium. In contrast to cesium, adsorption of4He and H2 do occur on a sodium surface. 相似文献