全文获取类型
收费全文 | 205192篇 |
免费 | 4621篇 |
国内免费 | 1907篇 |
专业分类
电工技术 | 4637篇 |
技术理论 | 6篇 |
综合类 | 2037篇 |
化学工业 | 32916篇 |
金属工艺 | 9565篇 |
机械仪表 | 6900篇 |
建筑科学 | 6643篇 |
矿业工程 | 1661篇 |
能源动力 | 5461篇 |
轻工业 | 18025篇 |
水利工程 | 2191篇 |
石油天然气 | 5056篇 |
武器工业 | 161篇 |
无线电 | 22962篇 |
一般工业技术 | 36869篇 |
冶金工业 | 34599篇 |
原子能技术 | 4673篇 |
自动化技术 | 17358篇 |
出版年
2022年 | 1484篇 |
2021年 | 2338篇 |
2020年 | 1685篇 |
2019年 | 1906篇 |
2018年 | 2844篇 |
2017年 | 2898篇 |
2016年 | 2999篇 |
2015年 | 2549篇 |
2014年 | 4038篇 |
2013年 | 9392篇 |
2012年 | 6204篇 |
2011年 | 8268篇 |
2010年 | 6753篇 |
2009年 | 7545篇 |
2008年 | 7422篇 |
2007年 | 7240篇 |
2006年 | 6413篇 |
2005年 | 5956篇 |
2004年 | 5435篇 |
2003年 | 5131篇 |
2002年 | 5152篇 |
2001年 | 5143篇 |
2000年 | 4713篇 |
1999年 | 4912篇 |
1998年 | 11080篇 |
1997年 | 7955篇 |
1996年 | 6167篇 |
1995年 | 4704篇 |
1994年 | 3982篇 |
1993年 | 3825篇 |
1992年 | 2812篇 |
1991年 | 2689篇 |
1990年 | 2532篇 |
1989年 | 2535篇 |
1988年 | 2448篇 |
1987年 | 2174篇 |
1986年 | 2118篇 |
1985年 | 2391篇 |
1984年 | 2214篇 |
1983年 | 2038篇 |
1982年 | 1900篇 |
1981年 | 1963篇 |
1980年 | 1805篇 |
1979年 | 1828篇 |
1978年 | 1780篇 |
1977年 | 2112篇 |
1976年 | 2699篇 |
1975年 | 1560篇 |
1974年 | 1552篇 |
1973年 | 1611篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
3.
F.T. Munna Vidhya Selvanathan K. Sobayel Ghulam Muhammad Nilofar Asim Nowshad Amin Kamaruzzaman Sopian Md. Akhtaruzzaman 《Ceramics International》2021,47(8):11003-11009
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell. 相似文献
4.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
5.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
6.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
7.
Multimedia Tools and Applications - Since Noar and Shamir introduced visual cryptography scheme (VCS), the cheating problem of VCS has absorbed much attention of scholars. The current researches on... 相似文献
8.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
9.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
10.