全文获取类型
收费全文 | 4718篇 |
免费 | 325篇 |
国内免费 | 137篇 |
专业分类
电工技术 | 181篇 |
技术理论 | 1篇 |
综合类 | 110篇 |
化学工业 | 709篇 |
金属工艺 | 149篇 |
机械仪表 | 53篇 |
建筑科学 | 19篇 |
矿业工程 | 38篇 |
能源动力 | 587篇 |
轻工业 | 11篇 |
石油天然气 | 45篇 |
武器工业 | 6篇 |
无线电 | 1413篇 |
一般工业技术 | 1665篇 |
冶金工业 | 159篇 |
原子能技术 | 18篇 |
自动化技术 | 16篇 |
出版年
2025年 | 33篇 |
2024年 | 640篇 |
2023年 | 380篇 |
2022年 | 131篇 |
2021年 | 345篇 |
2020年 | 480篇 |
2019年 | 517篇 |
2018年 | 349篇 |
2017年 | 305篇 |
2016年 | 219篇 |
2015年 | 125篇 |
2014年 | 92篇 |
2013年 | 107篇 |
2012年 | 100篇 |
2011年 | 112篇 |
2010年 | 100篇 |
2009年 | 90篇 |
2008年 | 84篇 |
2007年 | 122篇 |
2006年 | 128篇 |
2005年 | 110篇 |
2004年 | 98篇 |
2003年 | 63篇 |
2002年 | 81篇 |
2001年 | 52篇 |
2000年 | 74篇 |
1999年 | 46篇 |
1998年 | 35篇 |
1997年 | 30篇 |
1996年 | 28篇 |
1995年 | 21篇 |
1994年 | 23篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有5180条查询结果,搜索用时 0 毫秒
1.
We study the effect of Josephson coupling between adjacent superconducting layers on the BCS energy spectrum. We find that the interference between the gap functions of two layers can lead to vanishing condensation energy for perpendicular momenta corresponding to the formation of standing waves. We therefore predict a conventional energy spectrum for large interlayer spacings, if the gap of the single layers has no nodes, and in all cases a gapless spectrum for small spacings. Within the experimental error, our numerical results account for the low-temperature dependence of the penetration depth reported in Nd1.85Ce0.15CuO4 and YBa2Cu3O6.9. 相似文献
2.
Oxygen nonstoichiometry in the distorted perovskite BaBiO3 has been studied by thermogravimetric analysis using controlled oxygen pressures. Three distinct regions of nonstoichiometry are observed with composition ranges which narrow as the temperature is lowered. Samples isolated from each region were shown by powder X-ray diffraction to retain the perovskite subcell but show different types of framework distortion. Low temperature reoxidation of the oxygen deficient phases is also described. 相似文献
3.
Preparation of Perovskite-Type Oxides La1-x Srx Fe1-y Coy O3 Using EDTA Sol-Gel Method 总被引:3,自引:0,他引:3
Two series of perovskite-type oxides with composition La1-xSrxFeO3 (x≤0.8)and La1-xSrxFe1-yCoyO3( x = 0.2;y = 0.2, 0.4 ) powder productions were synthesized by EDTA complexing sol-gel method. The products were characterized by XRD, TEM, SEM, BET method (N2 adsorption)and laser granularity analysis for different synthesis conditions to obtain the optimum conditions for the preparation process. Single-phased, uniform perovskite-type oxides with small particle size were obtained by EDTA sol-gel process with high stability and repeatability,and the process temperature is much lower than that of solid state reaction method. 相似文献
4.
Photocatalysts with perovskites for hydrogen production from aqueous solution were reviewed. Among the most of metal oxide photocatalysts, the family of ABO3 Perovskite-type oxide shows higher photocatalytie activity, especially alkaline earth titanate and alkali tantalate. Therein, sodium tantalate showed the highest activity for water splitting. The reasons for the high photocatalytic activity of ABO3 perovskties are considered to the diverse and flexible crystal structure. The photocatalytic activity of ABO3 perovskties can be improved by doping other element at A site, B site or O site and loading CO-catalysts such as NiO and Pt. In this paper, the mechanism of photocatalytic water splitting, the structure of ABO3 perovsktie, and Perovskite-type photocatalysts were reviewed. 相似文献
5.
研究了前驱体合成(又称铌铁矿合成)与传统的氧化物混合合成,对PMN-PNN-PZT四元系压电陶瓷性能的影响。结果表明,前驱体合成工艺能够在合成过程中避免焦绿石相的生成。并且相比较于氧化物混合合成的工艺,它能使得压电陶瓷的压电常数d33由475 pC/N提高到530 pC/N,机械品质因数Qm从96提高到185,介质损耗tanδ也从0.020降低到0.009。综合实验分析结果得出前驱体合成方法是一种更加优异的合成方法。 相似文献
6.
二维有机-无机杂化钙钛矿因在光伏、光电子等领域的巨大应用潜力而备受关注.此外,该类材料具有突出的结构可调性和材料稳定性,为功能性质的设计调控及器件应用提供了丰富的材料设计平台.然而,将多种物理通道的性质整合实现材料的多功能性仍具有挑战性,而对其进行快速有效的调节更是难上加难.迄今为止,尚未成功实现可调谐的光电多通道响应... 相似文献
7.
G. MurtazaIftikhar Ahmad B. AminA. Afaq M. MaqboolJ. Maqssod I. KhanM. Zahid 《Optical Materials》2011,33(3):553-557
Structural and optoelectronic properties of BaThO3 cubic perovskite are calculated using all electrons full potential linearized augmented plane wave (FP-LAPW) method. Wide and direct band gap, 5.7 eV, of the compound predicts that it can be effectively used in UV based optoelectronic devices. Different characteristic peaks in the wide UV range emerges mainly due to the transition of electrons between valance band state O-p and conduction band states Ba-d, Ba-f, Th-f and Th-d. 相似文献
8.
金属卤化物气体放电灯启动问题的探讨 总被引:6,自引:0,他引:6
本文介绍了分别改变灯内填充物含量即 NaI 和 ScI 含量的方法,探讨此变化与光源气体放电参数的关系,从而分析和研究金属卤化物灯的启动特性,从而寻求延长光源寿命的途径。 相似文献
9.
Perovskite Solar Cells: Smart Passivation Materials with a Liquid Metal Microcapsule as Self‐Healing Conductors for Sustainable and Flexible Perovskite Solar Cells (Adv. Funct. Mater. 22/2018)
下载免费PDF全文

10.
无电极放电灯的发展动态 总被引:7,自引:3,他引:7
无电极放电灯是新一代电光源,具有结构简单、无电极、高光效、高显色性能和长寿命等特性,已发展成为无电极荧光灯、无电极金属卤化物灯和微波硫灯等几种类型。本文主要介绍这些无电极放电灯的发光原理、放电类型、灯的结构、特性和发展动态。 相似文献