全文获取类型
收费全文 | 420178篇 |
免费 | 13340篇 |
国内免费 | 4534篇 |
专业分类
电工技术 | 11066篇 |
技术理论 | 6篇 |
综合类 | 5127篇 |
化学工业 | 65296篇 |
金属工艺 | 16147篇 |
机械仪表 | 14681篇 |
建筑科学 | 14041篇 |
矿业工程 | 3227篇 |
能源动力 | 11800篇 |
轻工业 | 39555篇 |
水利工程 | 3755篇 |
石油天然气 | 7678篇 |
武器工业 | 480篇 |
无线电 | 53402篇 |
一般工业技术 | 73981篇 |
冶金工业 | 73095篇 |
原子能技术 | 5181篇 |
自动化技术 | 39534篇 |
出版年
2023年 | 2434篇 |
2022年 | 3720篇 |
2021年 | 5783篇 |
2020年 | 4482篇 |
2019年 | 4581篇 |
2018年 | 6113篇 |
2017年 | 6214篇 |
2016年 | 6320篇 |
2015年 | 6242篇 |
2014年 | 8893篇 |
2013年 | 20898篇 |
2012年 | 13335篇 |
2011年 | 17520篇 |
2010年 | 14507篇 |
2009年 | 15806篇 |
2008年 | 15896篇 |
2007年 | 15808篇 |
2006年 | 14991篇 |
2005年 | 13624篇 |
2004年 | 12036篇 |
2003年 | 11580篇 |
2002年 | 10545篇 |
2001年 | 10965篇 |
2000年 | 10248篇 |
1999年 | 11374篇 |
1998年 | 26527篇 |
1997年 | 18227篇 |
1996年 | 14234篇 |
1995年 | 10543篇 |
1994年 | 9140篇 |
1993年 | 8823篇 |
1992年 | 6000篇 |
1991年 | 5629篇 |
1990年 | 5240篇 |
1989年 | 4896篇 |
1988年 | 4593篇 |
1987年 | 3615篇 |
1986年 | 3519篇 |
1985年 | 4165篇 |
1984年 | 3691篇 |
1983年 | 3360篇 |
1982年 | 3116篇 |
1981年 | 3173篇 |
1980年 | 2857篇 |
1979年 | 2629篇 |
1978年 | 2346篇 |
1977年 | 2796篇 |
1976年 | 3756篇 |
1975年 | 2037篇 |
1973年 | 2134篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Materials Science - 相似文献
2.
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
3.
4.
5.
Peng Wang Yan Li Yujiao Qu Baowei Wang Jingxin Sun Chunwei Miao Ming Huang He Huang Congxiang Zhang 《International Journal of Food Science & Technology》2022,57(6):3428-3439
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP. 相似文献
6.
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
7.
Journal of Porous Materials - Co3O4 has been widely investigated as a promising candidate anode material for lithium-ion batteries. We report on the porous Co3O4 column synthesized via a simple... 相似文献
8.
Prof. Andrea Baier Dr. Anne Kokel Dr. William Horton Ewa Gizińska Dr. Garima Pandey Prof. Ryszard Szyszka Prof. Béla Török Prof. Marianna Török 《ChemMedChem》2021,16(12):1927-1932
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays. 相似文献
9.
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
10.
Xiaoyan Dong Xu Li Xiuli Chen Hongyun Chen Congcong Sun Junpeng Shi Feihong Pang Huanfu Zhou 《Ceramics International》2021,47(3):3079-3088
Dielectric capacitors with decent energy storage and fast charge-discharge performances are essential in advanced pulsed power systems. In this study, novel ceramics (1-x)NaNbO3-xBi(Ni2/3Nb1/3)O3(xBNN, x = 0.05, 0.1, 0.15 and 0.20) with high energy storage capability, large power density and ultrafast discharge speed were designed and prepared. The impedance analysis proves that the introducing an appropriate amount of Bi(Ni0·5Nb0.5)O3 boosts the insulation ability, thus obtaining a high breakdown strength (Eb) of 440 kV/cm in xBNN ceramics. A high energy storage density (Wtotal) of 4.09 J/cm3, recoverable energy storage density (Wrec) of 3.31 J/cm3, and efficiency (η) of 80.9% were attained in the 0.15BNN ceramics. Furthermore, frequency and temperature stability (fluctuations of Wrec ≤ 0.4% over 5–100 Hz and Wrec ≤ 12.3% over 20–120 °C) were also observed. The 0.15BNN ceramics exhibited a large power density (19 MW/cm3) and ultrafast discharge time (~37 ns) over the range of ambient temperature to 120 °C. These enhanced performances may be attributed to the improved breakdown strength and relaxor behavior through the incorporation of BNN. In conclusion, these findings indicate that 0.15BNN ceramics may serve as promising materials for pulsed power systems. 相似文献