全文获取类型
收费全文 | 93篇 |
免费 | 1篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 1篇 |
综合类 | 6篇 |
化学工业 | 4篇 |
金属工艺 | 4篇 |
机械仪表 | 8篇 |
建筑科学 | 11篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 2篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 16篇 |
冶金工业 | 3篇 |
原子能技术 | 22篇 |
自动化技术 | 16篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2016年 | 1篇 |
2014年 | 6篇 |
2013年 | 2篇 |
2012年 | 7篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有103条查询结果,搜索用时 203 毫秒
21.
Jarek P. Sabawa Aliaksandr S. Bandarenka 《International Journal of Hydrogen Energy》2021,46(29):15951-15964
Environmental influences, especially temperatures below the freezing point, can affect the performance and long-term stability of PEMFCs. Within the scope of this research, a completely new test procedure was developed to characterize PEMFC single cells with respect to their long-term stability at temperature cycles between 80 °C and ?10 °C. Using this procedure, the behavior of PEMFC single cells (active surface area of 43.6 cm2) with different cathode-ionomer-to-carbon (I/C) weight ratios (0.5/1.0/1.5) was evaluated. The generated in-situ measurement data clearly demonstrate that the performance of each PEMFC single cell changes individually as a function of the cathode I/C-ratio during the 120 stress cycles. While the MEA with an I/C ratio of 0.5 showed a power loss of ~1.49%, the MEAs with an I/C ratio of 1.0 and 1.5 showed a power loss of about ~7.75% and ~24.7%, respectively. The subsequent post-mortem ex-situ analyses clearly showed how the test procedure and the different I/C-ratios affected the changes in the catalyst layers (CL). The destructive mechanisms responsible for the changes can be divided into two categories: One part was driven by rapid enthalpy change leading to mechanical failure, and the other part, which led to the reduction of cathode CL thickness, was driven by rapid potential changes and potential shifts (overpotentials). This reduction in cathode CL thickness ultimately leads to an accumulation and excessive load of ionomer in the direction of GDL, resulting in a reduction in pore size, a shift in the core reaction area, and high O2 transport resistance. 相似文献
22.
23.
24.
A greenhouse experiment was conducted to elucidate the growth changes and tissues anatomical characteristics of giant reed
(Arundo donax L.), a perennial rhizomatous grass, which was cultivated for 70 d in soils contaminated with As, Cd and Pb. The results show
that giant reed rapidly grows with big biomass of shoots in contaminated soil, possessing strong metal-tolerance with limited
metal translocation from roots to shoots. When As, Cd and Pb concentrations in the soil are less than 254, 76.1 and 1 552
mg/kg, respectively, plant height and dried biomass are slightly reduced, the accumulation of As, Cd and Pb in shoots of giant
reed is low while metal concentration in roots is high, and the anatomical characteristics of stem tissues are thick and homogeneous
according to SEM images. However, plant height and dried biomass are significantly reduced and metal concentration in plant
shoots and roots are significantly increased (P<0.05), the stems images become heterogeneous and the secretion in vascular bundles increases significantly when As, Cd and
Pb concentrations in the soil exceed 334, 101 and 2 052 mg/kg, respectively. The giant reed is a promising, naturally occurring
plant with strong metal-tolerance, which can be cultivated in soils contaminated with multiple metals for ecoremediation purposes. 相似文献
25.
26.
p-type TlGaSeS single crystal was used to fabricate a Schottky device. Silver and carbon metals were used as the Ohmic and Schottky contacts, respectively. The device which displayed wide RF band at 13.200 and narrow band at 62.517 kHz with Q value of 1.4 and of 6.3 × 104, respectively, is characterized by means of current (I)–voltage (V), capacitance (C)–voltage characteristics as well as capacitance–frequency (f) characteristics. The device series resistance, ideality factor and barrier height are determined from the I–V curve as 35.8 MΩ, 1.2 and 0.74 eV, respectively. The apparent acceptor density and the build in voltage of the device increased with increasing ac signal frequency. The high Q value, observed at 62.517 kHz, indicated a much lower rate of energy loss relative to the stored energy of the device. The energy loss (Q−1) is much less than 0.001% of the stored value. The device was tested and found to remain at the same mode of resonance for several hours. It never switched or ceased unless it was tuned off. 相似文献
27.
June-O Song Hun Kang I.T. Ferguson Sung-Pyo Jung H.P. Lee Hyun-Gi Hong Takhee Lee Tae-Yeon Seong 《Solid-state electronics》2005,49(12):990
We report on the improvement of the electrical characteristics of GaN-based light-emitting diodes (LEDs) fabricated with Ag (1 nm)/indium tin oxide (ITO) (250 nm) p-type contacts by using Ni nanodots. As-deposited Ag/ITO contacts with and without the Ni nanodots give non-linear electrical behaviour. However, annealing the samples at 530–630 °C for 1 min in air results in ohmic behaviour. The reverse leakage current characteristics of near UV LEDs are much improved when the Ni nanodots are used. The output power (at 20 mA) of LEDs fabricated with the Ni nanodots is enhanced by a factor of 1.34 as compared with that of LEDs made without the Ni nanodots. 相似文献
28.
29.
Nonlocal boundary value problems at resonance for a higher order nonlinear differential equation with a p-Laplacian are considered in this paper. By using a new continuation theorem, some existence results are obtained for such boundary value problems. An explicit example is also given in this paper to illustrate the main results. 相似文献
30.
国内外学者从不同角度对"三化同步"进行了大量研究,本文从推进"三化同步"发展的理论与现实基础、必要性、存在的问题及长效机制方面进行了一个综述,为今后研究"三化同步"发展提供理论基础。 相似文献