全文获取类型
收费全文 | 12708篇 |
免费 | 1189篇 |
国内免费 | 1078篇 |
专业分类
电工技术 | 458篇 |
综合类 | 649篇 |
化学工业 | 3438篇 |
金属工艺 | 1024篇 |
机械仪表 | 525篇 |
建筑科学 | 335篇 |
矿业工程 | 215篇 |
能源动力 | 746篇 |
轻工业 | 174篇 |
水利工程 | 68篇 |
石油天然气 | 190篇 |
武器工业 | 70篇 |
无线电 | 2626篇 |
一般工业技术 | 2492篇 |
冶金工业 | 1382篇 |
原子能技术 | 184篇 |
自动化技术 | 399篇 |
出版年
2024年 | 42篇 |
2023年 | 200篇 |
2022年 | 288篇 |
2021年 | 323篇 |
2020年 | 361篇 |
2019年 | 325篇 |
2018年 | 256篇 |
2017年 | 377篇 |
2016年 | 417篇 |
2015年 | 464篇 |
2014年 | 648篇 |
2013年 | 672篇 |
2012年 | 863篇 |
2011年 | 954篇 |
2010年 | 611篇 |
2009年 | 746篇 |
2008年 | 617篇 |
2007年 | 787篇 |
2006年 | 747篇 |
2005年 | 649篇 |
2004年 | 577篇 |
2003年 | 629篇 |
2002年 | 510篇 |
2001年 | 454篇 |
2000年 | 467篇 |
1999年 | 252篇 |
1998年 | 242篇 |
1997年 | 211篇 |
1996年 | 195篇 |
1995年 | 158篇 |
1994年 | 128篇 |
1993年 | 110篇 |
1992年 | 123篇 |
1991年 | 128篇 |
1990年 | 155篇 |
1989年 | 120篇 |
1988年 | 33篇 |
1987年 | 24篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
121.
122.
Dissolution Behaviors and Applications of Silicon Oxides and Nitrides in Transient Electronics 下载免费PDF全文
Seung‐Kyun Kang Suk‐Won Hwang Huanyu Cheng Sooyoun Yu Bong Hoon Kim Jae‐Hwan Kim Yonggang Huang John A. Rogers 《Advanced functional materials》2014,24(28):4427-4434
Silicon oxides and nitrides are key materials for dielectrics and encapsulation layers in a class of silicon‐based high performance electronics that has ability to completely dissolve in a controlled fashion with programmable rates, when submerged in bio‐fluids and/or relevant solutions. This type of technology, referred to as “transient electronics”, has potential applications in biomedical implants, environmental sensors, and other envisioned areas. The results presented here provide comprehensive studies of transient behaviors of thin films of silicon oxides and nitrides in diverse aqueous solutions at different pH scales and temperatures. The kinetics of hydrolysis of these materials depends not only on pH levels/ion concentrations of solutions and temperatures, but also on the morphology and chemistry of the films, as determined by the deposition methods and conditions. Encapsulation strategies with a combination of layers demonstrate enhancement of the lifetime of transient electronic devices, by reducing water/vapor permeation through the defects. 相似文献
123.
124.
Paul Sonntag Jan Haschke Sven Kühnapfel Tim Frijnts Daniel Amkreutz Bernd Rech 《Progress in Photovoltaics: Research and Applications》2016,24(5):716-724
We present an interdigitated back‐contact silicon heterojunction system designed for liquid‐phase crystallized thin‐film (~10 µm) silicon on glass. The preparation of the interdigitated emitter (a‐Si:H(p)) and absorber (a‐Si:H(n)) contact layers relies on the etch selectivity of doped amorphous silicon layers in alkaline solutions. The etch rates of a‐Si:H(n) and a‐Si:H(p) in 0.6% NaOH were determined and interdigitated back‐contact silicon heterojunction solar cells with two different metallizations, namely Al and ITO/Ag electrodes, were evaluated regarding electrical and optical properties. An additional random pyramid texture on the back side provides short‐circuit current density (jSC) of up to 30.3 mA/cm2 using the ITO/Ag metallization. The maximum efficiency of 10.5% is mainly limited by a low of fill factor of 57%. However, the high jSC, as well as VOC values of 633 mV and pseudo‐fill factors of 77%, underline the high potential of this approach. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
125.
Kan‐Hua Lee Kenji Araki Li Wang Nobuaki Kojima Yoshio Ohshita Masafumi Yamaguchi 《Progress in Photovoltaics: Research and Applications》2016,24(10):1310-1318
The paper presents a quantitative approach to the investigation and comparison of the material qualities of III–V on silicon (III–V/Si) solar cells by using external radiative efficiencies. We use this analysis to predict the limiting efficiencies and evaluate the criteria of material quality in order to achieve high‐efficiency III–V/Si solar cells. This result yields several implications for the design of high‐efficiency III–V/Si solar cells. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
126.
127.
128.
Pavel L. Komarov Mihai G. Burzo Gunhan Kaytaz Peter E. Raad 《Microelectronics Journal》2003,34(12):1115-1118
The transient thermoreflectance method has been used to measure the thermal conductivity of natural silicon and isotopically-pure silicon-28 layers that are epitaxially grown on natural silicon substrates. The measurements were performed at room temperature for both a low level (1016) and a higher level (2×1019) of Boron doping of the epitaxial layers. The results indicate a gain of approximately 55% in the thermal conductivity of Si28 as compared to that of natural Si, at both low and higher levels of doping, and a loss of approximately 19% for both types of silicon due to the higher level of doping. 相似文献
129.
为提高薄膜电池对光的捕获能力, 将平面硅薄膜电池制 作成矩形空芯波导结构,对其太阳光注入方式、光捕获能力和光-电转换效能进行了理论和 实验探讨。基于 多层膜反射理论和波导反射模型对波导电池光捕获效果的预测表明,波导电池能够将入射光 限制在空芯结 构内多次反射和吸收,具有较平面电池更高的光捕获能力。测定了不同平行光束在不同入射角度 下平面和波导 电池的光捕获功率和光-电转换效能的结果表明,波导电池对入射光功率近似全部捕获,其 光-电功率转换效能 较对应的平面电池有3~5倍的提升。对不同截面尺寸和长度的单结空芯波导电池光捕获率 进行了计算,提 出从电池膜层结构和空芯几何尺寸参数优化硅薄膜矩形空芯波导电池的思路,通过优化有 望实现用小于多结平面电池外形尺寸的单结空芯波导电池达到更好的光捕获效果。 相似文献
130.
The BER theoretical model and properties of SiPM‐based receiver for OOK optical communication 下载免费PDF全文
Guoqing Zhang Lina Liu Changjun Zhu Anxiang Wang Xiang'an Yan 《International Journal of Communication Systems》2018,31(15)
The bit error rate (BER) theory of silicon photomultiplier (SiPM) based on‐off keying optical communication receiver, which introduces photon equivalent threshold is established. The optical crosstalk effect, the dark counts, the amplitude fluctuations of output pulses of SiPM, the baseline fluctuation, the shape of the incident light pulse, the adjacent symbol interference as well as the photon detection efficiency (PDE) are considered in the theory model. The numerical result shows that the average minimum optical power required is much smaller than that of the avalanche photodiode‐based receivers under the same conditions. The BER of SiPM‐based optical communication receiver is very sensitive to the PDE and optical crosstalk (OC) probability of SiPM. For the application of digital optical communication, a SiPM with high PDE but low OC probability and low dark count rate is a preference, under the premise that the output pulse is fast enough. For the state‐of‐the‐art SiPMs, the dark count rate is small enough to obtain adequate BER, and the OC effect is not a big limitation of the performance of SiPM‐based receiver. Moreover, the amplitude fluctuation and the baseline fluctuation of the SiPM‐based receiver are not bottlenecks of the performance in practice. 相似文献