全文获取类型
收费全文 | 38903篇 |
免费 | 3178篇 |
国内免费 | 1757篇 |
专业分类
电工技术 | 1221篇 |
综合类 | 3225篇 |
化学工业 | 3731篇 |
金属工艺 | 3806篇 |
机械仪表 | 1878篇 |
建筑科学 | 9192篇 |
矿业工程 | 2090篇 |
能源动力 | 1237篇 |
轻工业 | 1166篇 |
水利工程 | 1521篇 |
石油天然气 | 1115篇 |
武器工业 | 267篇 |
无线电 | 3835篇 |
一般工业技术 | 5557篇 |
冶金工业 | 2423篇 |
原子能技术 | 352篇 |
自动化技术 | 1222篇 |
出版年
2024年 | 37篇 |
2023年 | 376篇 |
2022年 | 672篇 |
2021年 | 876篇 |
2020年 | 958篇 |
2019年 | 692篇 |
2018年 | 771篇 |
2017年 | 1030篇 |
2016年 | 1143篇 |
2015年 | 1221篇 |
2014年 | 2256篇 |
2013年 | 2111篇 |
2012年 | 2762篇 |
2011年 | 3138篇 |
2010年 | 2371篇 |
2009年 | 2477篇 |
2008年 | 2273篇 |
2007年 | 2881篇 |
2006年 | 2575篇 |
2005年 | 2271篇 |
2004年 | 1820篇 |
2003年 | 1599篇 |
2002年 | 1390篇 |
2001年 | 1192篇 |
2000年 | 1055篇 |
1999年 | 780篇 |
1998年 | 593篇 |
1997年 | 488篇 |
1996年 | 386篇 |
1995年 | 354篇 |
1994年 | 301篇 |
1993年 | 241篇 |
1992年 | 177篇 |
1991年 | 126篇 |
1990年 | 85篇 |
1989年 | 89篇 |
1988年 | 57篇 |
1987年 | 37篇 |
1986年 | 31篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
3.
Understanding on the hydrogen detection of plasma sprayed tin oxide/tungsten oxide (SnO2/WO3) sensor
《International Journal of Hydrogen Energy》2022,47(33):15120-15131
The plasma spray technique was well proven in producing metal oxide based gas sensors in the last two decades using different powder feedstocks. However, limited research was made to fabricate hydrogen gas sensor from tin oxide layer coated over tungsten oxide layer. This paper attempts to interpret the hydrogen gas sensing performances of plasma sprayed coating derived by depositing tin oxide layer over tungsten oxide (SnO2/WO3) layer. Plasma sprayed SnO2/WO3 sensor showed maximum response of 90% at 150 °C in contrast to stand-alone WO3 (89% at 350 °C) and stand-alone SnO2 (89% at 250 °C). The lower operating temperature of SnO2/WO3 sensor without compromising gas response was attributed to the WO3–SnO2 hetero-junction. SnO2/WO3 sensor showed selective sensing towards hydrogen with respect to carbon monoxide and methane gases. This sensor also possessed repeatable characteristics after 39 days from the initial measurement. In a nut-shell, plasma spayed SnO2/WO3 sensor showed stability of base resistance, repeatability after successive response and recovery cycles, selective sensing towards 500 ppm H2 with significant magnitude of gas response of 90%, response time of 35 s and recovery time of 269 s at a temperature of 150 °C. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(6):4062-4074
In this work, coupling effects of water content, temperature, oxygen density, and polytetrafluoroethylene (PTFE) loading on oxygen transport through an ionomer thin film on a platinum surface in a catalyst layer of a proton exchange membrane (PEM) fuel cell are investigated using molecular dynamics approach. Taguchi orthogonal algorithm is employed to comprehensively analyze the coupling effects in a limited number of cases. It is found that the effect of operation temperature is the weakest among the four factors, which has the smallest effect index 14.4. Coupling effects including the PTFE loadings on the oxygen transfer through the ionomer thin film is uncovered. Less PTFE loadings should be beneficial for the oxygen transfer. The chemical potential gradient is considered as the major driven force for the oxygen transport through the ionomer thin film, and oxygen density is the dominating factor, significantly affecting the chemical potential in the thin film. 相似文献
5.
6.
在总结前人钨中空位及其团簇的能量学和动力学行为的研究成果基础上,采用第一性原理方法系统计算了钨中空位及其团簇的结合能和扩散能垒。研究发现,交换关联泛函PW91和PBE较PBEsol、AM05和LDA更适合用于计算钨空位的能量学性质。基于第一性原理计算结果对文献中单空位形成能、双空位作用性质等争议性问题进行了讨论,并对钨经验势进行了评估。研究结果表明,钨中孤立单空位间总是相互排斥,而空位团簇(Vn>3)对单空位具有很强的吸引作用,其结合能随着所含空位个数增多呈现波动性增大的趋势。空位团簇稳定结构可通过最小化Wigner-Seitz表面积来确定,其结合能与Vn与Vn-1之间的Wigner-Seitz面积之差呈正比。 相似文献
7.
8.
Ioanna Mela Chetan Poudel Miguel Anaya Géraud Delport Kyle Frohna Stuart Macpherson Tiarnan A. S. Doherty Anna Scheeder Samuel D. Stranks Clemens F. Kaminski 《Advanced functional materials》2021,31(23):2100293
Halide perovskites are a versatile class of semiconductors employed for high performance emerging optoelectronic devices, including flexoelectric systems, yet the influence of their ionic nature on their mechanical behavior is still to be understood. Here, a combination of atomic-force, optical, and compositional X-ray microscopy techniques is employed to shed light on the mechanical properties of halide perovskite films at the nanoscale. Mechanical domains within and between morphological grains, enclosed by mechanical boundaries of higher Young's Modulus (YM) than the bulk parent material, are revealed. These mechanical boundaries are associated with the presence of bromide-rich clusters as visualized by nano-X-ray fluorescence mapping. Stiffer regions are specifically selectively modified upon light soaking the sample, resulting in an overall homogenization of the mechanical properties toward the bulk YM. This behavior is attributed to light-induced ion migration processes that homogenize the local chemical distribution, which is accompanied by photobrightening of the photoluminescence within the same region. This work highlights critical links between mechanical, chemical, and optoelectronic characteristics in this family of perovskites, and demonstrates the potential of combinational imaging studies to understand and design halide perovskite films for emerging applications such as photoflexoelectricity. 相似文献
9.
10.