全文获取类型
收费全文 | 3102篇 |
免费 | 362篇 |
国内免费 | 225篇 |
专业分类
电工技术 | 124篇 |
综合类 | 155篇 |
化学工业 | 437篇 |
金属工艺 | 138篇 |
机械仪表 | 106篇 |
建筑科学 | 4篇 |
矿业工程 | 11篇 |
能源动力 | 41篇 |
轻工业 | 353篇 |
水利工程 | 5篇 |
石油天然气 | 20篇 |
武器工业 | 13篇 |
无线电 | 1650篇 |
一般工业技术 | 491篇 |
冶金工业 | 52篇 |
原子能技术 | 33篇 |
自动化技术 | 56篇 |
出版年
2024年 | 18篇 |
2023年 | 112篇 |
2022年 | 62篇 |
2021年 | 123篇 |
2020年 | 115篇 |
2019年 | 100篇 |
2018年 | 67篇 |
2017年 | 102篇 |
2016年 | 118篇 |
2015年 | 99篇 |
2014年 | 163篇 |
2013年 | 159篇 |
2012年 | 284篇 |
2011年 | 261篇 |
2010年 | 155篇 |
2009年 | 159篇 |
2008年 | 207篇 |
2007年 | 229篇 |
2006年 | 203篇 |
2005年 | 155篇 |
2004年 | 141篇 |
2003年 | 90篇 |
2002年 | 66篇 |
2001年 | 55篇 |
2000年 | 68篇 |
1999年 | 39篇 |
1998年 | 48篇 |
1997年 | 48篇 |
1996年 | 35篇 |
1995年 | 24篇 |
1994年 | 41篇 |
1993年 | 20篇 |
1992年 | 30篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有3689条查询结果,搜索用时 15 毫秒
1.
2.
O. Khamman 《Materials Letters》2007,61(3):639-643
The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase nickel niobate (NiNb2O6) powders. The formation of the NiNb2O6 phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that the minor phases of unreacted NiO and Nb2O5 precursors and the Ni4Nb2O9 phase tend to form together with the columbite NiNb2O6 phase, depending on calcination conditions. More importantly, it is seen that optimization of calcination conditions can lead to a single-phase NiNb2O6 in an orthorhombic phase. 相似文献
3.
R. Wongmaneerung W. Chaisan O. Khamman R. Yimnirun S. Ananta 《Ceramics International》2008,34(4):813-817
The potential of the vibro-milling technique as a simple method to obtain usable quantities of single-phase electroceramic powders with nanosized particles was examined. A detailed study considering the role of both milling time and firing condition on phase formation and particle size of the final product was performed. The calcination temperature for the formation of the desired phase was lower when longer milling times have been applied. More importantly, by employing an appropriate choice of the milling time and calcination condition, high purity electroceramic nanopowders have been successfully prepared with a simple solid-state reaction method. 相似文献
4.
本文在文献[1]和[2]的基础上,考虑动态靶目标是受载结构的影响,综合考虑大气吸收、散射、湍流及热畸变效应对激光传输的影响,计算了连续激光引起高空中动态靶目标的破坏阈值。 相似文献
5.
Methyl groups from chain scission and H-crosslinks have been identified by solid-state nuclear magnetic resonance in amorphous ethylene-propylene copolymers containing 23 and 36 mole % propylene after γ-irradiation to 10 MGy at 30°C. G (scission) and G (crosslink) values determined from the n.m.r. spectra and by extraction are in agreement, which suggests that the crosslinks are not clustered. This may differ from the situation in polyethylene where there is a substantial crystalline content. G(S). G(X) and the ratio G(S)/G(X) increase with increasing propylene content of the copolymers. 相似文献
6.
7.
The paper reviews recent results obtained with diode lasers used in external hybrid cavities with frequency selective feedback.
Such cavities attract continuing interest for several reasons. They generate a tunable single laser mode with very low linewidths
(usually a few tens of kilohertz). Very wide discrete tunable ranges over 100 nm for Fabry-Perot type and over 200 nm for
quantum well lasers are achieved. They can be made to oscillate in a tunable mode having the desired polarization state,TE orTM and, in some cases, simultaneously atTE andTM. This is done by designing a cavity that increases strongly theTM/TE intensity ratio and by using coatings on one laser facet that greatly lower bothTE andTM reflectivities. High-speed polarization switching in the gigahertz range is possible by inserting passive or active polarization
selecting elements in the cavity. For all these reasons hybrid external cavities are attractive for applications in optical
metrology, spectroscopy and optical communications. Moreover, the external cavity configuration allows the study of physical
mechanisms in the laser diode by inducing on purpose phenomena that would have been otherwise impossible to achieve with free-running
lasers. 相似文献
8.
本文对高功率板条固体激光器研究的进展和应用前景作了综合评述。结合作者部分工作,对板条激光器的热效应、聚光器和光学谐振腔等关键问题和技术进行了物理分析。 相似文献
9.
10.