全文获取类型
收费全文 | 7322篇 |
免费 | 376篇 |
国内免费 | 357篇 |
专业分类
电工技术 | 37篇 |
技术理论 | 1篇 |
综合类 | 111篇 |
化学工业 | 2672篇 |
金属工艺 | 974篇 |
机械仪表 | 138篇 |
建筑科学 | 89篇 |
矿业工程 | 31篇 |
能源动力 | 731篇 |
轻工业 | 145篇 |
水利工程 | 6篇 |
石油天然气 | 24篇 |
武器工业 | 44篇 |
无线电 | 635篇 |
一般工业技术 | 1659篇 |
冶金工业 | 476篇 |
原子能技术 | 133篇 |
自动化技术 | 149篇 |
出版年
2024年 | 13篇 |
2023年 | 473篇 |
2022年 | 255篇 |
2021年 | 235篇 |
2020年 | 427篇 |
2019年 | 447篇 |
2018年 | 206篇 |
2017年 | 456篇 |
2016年 | 397篇 |
2015年 | 381篇 |
2014年 | 508篇 |
2013年 | 484篇 |
2012年 | 424篇 |
2011年 | 377篇 |
2010年 | 301篇 |
2009年 | 383篇 |
2008年 | 169篇 |
2007年 | 369篇 |
2006年 | 342篇 |
2005年 | 175篇 |
2004年 | 117篇 |
2003年 | 145篇 |
2002年 | 162篇 |
2001年 | 136篇 |
2000年 | 104篇 |
1999年 | 120篇 |
1998年 | 47篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 24篇 |
1991年 | 39篇 |
1990年 | 50篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1981年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1969年 | 8篇 |
1968年 | 5篇 |
1965年 | 8篇 |
1964年 | 3篇 |
排序方式: 共有8055条查询结果,搜索用时 15 毫秒
2.
3.
Zhencai Li Dacheng Zhou Lars R. Jensen Jianbei Qiu Yanfei Zhang Yuanzheng Yue 《Journal of the American Ceramic Society》2021,104(9):4471-4478
The transparent Er3+-Yb3+-doped fluoro-aluminosilicate glass-ceramic (GC) was prepared by melt-quenching. The crystal phase, morphology, and up-conversion (UC) luminescence of as-produced GC were characterized by X-ray diffraction, scanning electron microscopy, and fluorescence spectrophotometry, respectively. The results show that BaYF5 nanocrystals were uniformly distributed in the glass matrix of the as-produced GC. When the as-produced GC was subjected to heat treatment, the crystallinity was increased, but the crystal identity remains unchanged. Such heat-treatment doubled the intensity of the UC luminescence, and this enhancement was ascribed to the increased incorporation of both Er3+ and Yb3+ ions into the lower phonon energy environment of BaYF5 nanocrystals. Furthermore, the heat-treated GC was stable against further crystallization, and consequently its UC luminescence was stable at the application temperature. The heat-treated GC was found to possess an outstanding temperature-sensing capability. 相似文献
4.
Zhou Songqing Liang Jianjun Hu Huawen Xiao Hanning Li Guiyu 《Journal of Materials Science》2022,57(11):6249-6265
Journal of Materials Science - The unsatisfactory high-temperature performance of commonly used silicon carbide (SiC)-based ceramics calls for a novel approach for their reinforcement. We present... 相似文献
5.
《Journal of the European Ceramic Society》2022,42(2):453-461
A few compositions of the system Sr2Mn1-xSnxO4 (x = 0.0, 0.3, 0.5) were synthesized in the air by the solid-state ceramic route. A change in the sign (positive to negative) of the permittivity above a particular temperature (TC) is observed at all the measured frequencies. The negative permittivity was analyzed by the Drude-Lorentz model. It was found that negative permittivity is caused by the plasma oscillations of thermally excited free charge carriers. Analysis of XPS spectra confirmed the presence of mixed-valence states of both Mn (Mn4+ and Mn3+) and Sn (Sn4+ and Sn2+) ions. The UV–vis.-IR spectroscopy results indicated generation of a large number of defect states in the forbidden bandgap region of Sr2MnO4 on the substitution of Sn at Mn site. Synthesized samples are promising metamaterials for radio frequency (10 Hz -2 MHz) region applications due to the high-temperature plasmonic behavior. 相似文献
7.
《Ceramics International》2022,48(17):24716-24724
Dielectric capacitors show great potential in superior energy storage devices. However, the energy density of these capacitors is still inadequate to meet the requirement of energy storage applications. In this study, the Bi0.5Na0.47Li0.03TiO3-xNaNbO3 (BNLT-xNN) ceramics were prepared via conventional solid-phase reaction. Results showed that NN can efficaciously enhance the breakdown strength (Eb) and the relaxation behavior of the BNLT ceramic because of the broken ferroelectric long-range order. When x = 0.3, the maximum Eb reached 350 kV/cm, at which the 0.7BNLT-0.3NN ceramic exhibited the high recoverable energy storage density (Wrec) of 4.83 J/cm3 and great efficiency (η) of 78.9%. The ceramic demonstrated good temperature stability at 20 °C-160 °C and excellent fatigue resistance. Additionally, the 0.7BNLT-0.3NN ceramic presented high power density (PD; ~77.58 MW/cm3), large current density (CD; ~861.99 A/cm2), and quite short discharge time (t0.9; ~0.090 μs). These results indicated that the 0.7BNLT-0.3NN material has excellent energy storage properties and various application prospects. 相似文献
8.
《Ceramics International》2022,48(12):17086-17094
The composition of polymer derived ceramics could be readily tuned through controlling the structure and element content of the polymer precursors, and investigation on the effect of the element on microstructure evolution is important to the design of advanced ceramics. In this article, the effect of carbon content in SiBCO polymer precursors was systematically investigated. The polymer network and thermal stability of polymer precursors and the carbon content of pyrolyzed SiBCO ceramic could be readily tuned by controlling the DVB amount used. Carbon contributed to the formation of graphitic carbon in SiBCxO ceramics and inhibited the growth of β–SiC and SiO2 crystals at 1600 °C, but lead to an increase in the graphitic carbon phase at 1800 °C. 相似文献
9.
《Journal of the European Ceramic Society》2022,42(13):5684-5690
In this work, Zn-Ni co-modified LiMg0.9Zn0.1-xNixPO4 (x = 0–0.1) microwave dielectric ceramics were fabricated using a solid state synthesis route. Rietveld refinement of the XRD data revealed that all ceramic samples have formed a single phase with olivine structure. SEM images showed that the samples have a dense microstructure, that agrees with the measured relative density of 97.73 %. Based on the complex chemical bond theory, Raman and infrared reflectance spectra, we postulate that εr is mainly affected by the ionic polarizability, lattice and bond energy, while P-O bond plays a decisive role in Q×f and τf value. Optimum properties of Q×f ~ 153,500 GHz, εr ~ 7.13 and τf ~ ?59 ppm/°C were achieved for the composition LiMg0.9Zn0.06Ni0.04PO4 sintered at 875 ℃ for 2 h. This set of properties makes these ceramics an excellent candidate for LTCC, wave-guide filters and antennas for 5 G/6 G communication applications. 相似文献
10.
《Ceramics International》2022,48(15):21502-21514
Based on the good osteogenic and angiogenic effects of silicon and magnesium elements, three types of micro-nano magnesium-containing silicates (MS), including akermanite (Ake, Ca2MgSi2O7), diopside (Dio, CaMgSi2O6) and forsterite (For, Mg2SiO4), were incorporated into calcium phosphate cement (CPC) to improve its osteogenic and angiogenic performances for clinical application. In this present work, the physicochemical properties, osteogenesis and angiogenesis of MS/CPCs (Ake/CPCs, Dio/CPCs and For/CPCs) were investigated systematically and comparatively. The results showed that all MS/CPCs had good biomineralization and significantly stimulated the osteogenic differentiation of mBMSCs and angiogenic differentiation of HUVECs, respectively. Besides, the stimulating effects were related to not only the category of MS, but also the content of MS. The For/CPCs had a good angiogenic property but their initial setting times were beyond 60 min. The Dio/CPCs showed the lowest biological performance among the three groups of MS/CPCs due to the lower ion release (Si and Mg). The Ake was the ideal modifier that could provide CPC with appropriate physicochemical properties, better osteogenesis and angiogenesis. Simultaneously, a higher addition (10 wt%) of akermanite resulted in the best potential to bone regeneration. Taken together, this research provides an effective approach to improve the overall performance of CPC, and 10Ake/CPC is of great promising prospect in bone repair. 相似文献