全文获取类型
收费全文 | 560012篇 |
免费 | 15121篇 |
国内免费 | 5934篇 |
专业分类
电工技术 | 14152篇 |
技术理论 | 11篇 |
综合类 | 6979篇 |
化学工业 | 84744篇 |
金属工艺 | 22600篇 |
机械仪表 | 19397篇 |
建筑科学 | 20475篇 |
矿业工程 | 3988篇 |
能源动力 | 15376篇 |
轻工业 | 54430篇 |
水利工程 | 5220篇 |
石油天然气 | 9119篇 |
武器工业 | 699篇 |
无线电 | 70938篇 |
一般工业技术 | 95164篇 |
冶金工业 | 96324篇 |
原子能技术 | 7711篇 |
自动化技术 | 53740篇 |
出版年
2022年 | 4061篇 |
2021年 | 6919篇 |
2020年 | 5170篇 |
2019年 | 5315篇 |
2018年 | 7282篇 |
2017年 | 7633篇 |
2016年 | 7723篇 |
2015年 | 7450篇 |
2014年 | 10956篇 |
2013年 | 26954篇 |
2012年 | 17392篇 |
2011年 | 22693篇 |
2010年 | 18499篇 |
2009年 | 19940篇 |
2008年 | 20807篇 |
2007年 | 20375篇 |
2006年 | 19618篇 |
2005年 | 17844篇 |
2004年 | 15662篇 |
2003年 | 15175篇 |
2002年 | 14317篇 |
2001年 | 14731篇 |
2000年 | 13640篇 |
1999年 | 15327篇 |
1998年 | 33366篇 |
1997年 | 23717篇 |
1996年 | 18401篇 |
1995年 | 13990篇 |
1994年 | 12184篇 |
1993年 | 11606篇 |
1992年 | 8320篇 |
1991年 | 7801篇 |
1990年 | 7117篇 |
1989年 | 6795篇 |
1988年 | 6562篇 |
1987年 | 5386篇 |
1986年 | 5171篇 |
1985年 | 6253篇 |
1984年 | 5558篇 |
1983年 | 5015篇 |
1982年 | 4670篇 |
1981年 | 4716篇 |
1980年 | 4379篇 |
1979年 | 4041篇 |
1978年 | 3849篇 |
1977年 | 4705篇 |
1976年 | 6547篇 |
1975年 | 3256篇 |
1974年 | 3063篇 |
1973年 | 3116篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
1.
Pengfei Liang Jie Zhu Di Wu Hui Peng Xiaolian Chao Zupei Yang 《Journal of the American Ceramic Society》2021,104(6):2702-2710
Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO2-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag+/Nb5+ co-doped (Ag1/4Nb3/4)xTi1−xO2 (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 103 and 1.6 × 104 at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics. 相似文献
2.
Journal of Materials Science - 相似文献
3.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
4.
5.
6.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
7.
8.
Qian Wu Xiangmei Liu Bo Li Lei Tan Yong Han Zhaoyang Li Yanqin Liang Zhenduo Cui Shengli Zhu Shuilin Wu Yufeng Zheng 《材料科学技术学报》2021,67(8):70-79
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection. 相似文献
9.
Shannon Lee Scott L. Carnahan Georgiy Akopov Philip Yox Lin-Lin Wang Aaron J. Rossini Kui Wu Kirill Kovnir 《Advanced functional materials》2021,31(16):2010293
Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi4P4 and IrSi3P3 are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and 29Si and 31P magic angle spinning NMR. In agreement with previous report RuSi4P4 crystallizes in NCS space group P1, while IrSi3P3 is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi4P4 and IrSi3P3 to be wide bandgap (Eg) semiconductors, Eg = 1.9 and 1.8 eV, respectively. RuSi4P4 and IrSi3P3 outperform the current state-of-the-art infrared SHG material, AgGaS2, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi4P4 and IrSi3P3 are promising candidates for longer wavelength NLO materials. 相似文献
10.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献