全文获取类型
收费全文 | 269384篇 |
免费 | 5164篇 |
国内免费 | 1632篇 |
专业分类
电工技术 | 5628篇 |
技术理论 | 6篇 |
综合类 | 2195篇 |
化学工业 | 44200篇 |
金属工艺 | 11192篇 |
机械仪表 | 9188篇 |
建筑科学 | 7682篇 |
矿业工程 | 2177篇 |
能源动力 | 5943篇 |
轻工业 | 26466篇 |
水利工程 | 2963篇 |
石油天然气 | 7020篇 |
武器工业 | 191篇 |
无线电 | 28156篇 |
一般工业技术 | 48380篇 |
冶金工业 | 46846篇 |
原子能技术 | 6332篇 |
自动化技术 | 21615篇 |
出版年
2021年 | 3130篇 |
2020年 | 2260篇 |
2019年 | 2677篇 |
2018年 | 4239篇 |
2017年 | 4251篇 |
2016年 | 4501篇 |
2015年 | 3221篇 |
2014年 | 5230篇 |
2013年 | 11808篇 |
2012年 | 7806篇 |
2011年 | 10210篇 |
2010年 | 8268篇 |
2009年 | 8898篇 |
2008年 | 9160篇 |
2007年 | 9126篇 |
2006年 | 8296篇 |
2005年 | 7320篇 |
2004年 | 6782篇 |
2003年 | 6590篇 |
2002年 | 6725篇 |
2001年 | 6578篇 |
2000年 | 6171篇 |
1999年 | 6161篇 |
1998年 | 13277篇 |
1997年 | 9464篇 |
1996年 | 7371篇 |
1995年 | 5747篇 |
1994年 | 5102篇 |
1993年 | 4885篇 |
1992年 | 3871篇 |
1991年 | 3538篇 |
1990年 | 3708篇 |
1989年 | 3573篇 |
1988年 | 3373篇 |
1987年 | 2943篇 |
1986年 | 2983篇 |
1985年 | 3396篇 |
1984年 | 3248篇 |
1983年 | 2917篇 |
1982年 | 2758篇 |
1981年 | 2840篇 |
1980年 | 2728篇 |
1979年 | 2636篇 |
1978年 | 2688篇 |
1977年 | 2952篇 |
1976年 | 3817篇 |
1975年 | 2371篇 |
1974年 | 2245篇 |
1973年 | 2380篇 |
1972年 | 1974篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
4.
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
5.
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
6.
Julio E. Trevino Swati Mohan Alexandra E. Salinas Emilia Cueva Karen Lozano 《应用聚合物科学杂志》2021,138(28):50665
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some. 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.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 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.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献