全文获取类型
收费全文 | 244629篇 |
免费 | 2589篇 |
国内免费 | 1656篇 |
专业分类
电工技术 | 4277篇 |
综合类 | 2475篇 |
化学工业 | 28663篇 |
金属工艺 | 15562篇 |
机械仪表 | 11760篇 |
建筑科学 | 5164篇 |
矿业工程 | 1440篇 |
能源动力 | 4791篇 |
轻工业 | 10203篇 |
水利工程 | 2706篇 |
石油天然气 | 2517篇 |
武器工业 | 15篇 |
无线电 | 30353篇 |
一般工业技术 | 53715篇 |
冶金工业 | 32958篇 |
原子能技术 | 2703篇 |
自动化技术 | 39572篇 |
出版年
2022年 | 499篇 |
2021年 | 810篇 |
2020年 | 630篇 |
2019年 | 788篇 |
2018年 | 21502篇 |
2017年 | 21156篇 |
2016年 | 14094篇 |
2015年 | 2020篇 |
2014年 | 1865篇 |
2013年 | 5164篇 |
2012年 | 7712篇 |
2011年 | 19658篇 |
2010年 | 17544篇 |
2009年 | 15086篇 |
2008年 | 15767篇 |
2007年 | 18619篇 |
2006年 | 3951篇 |
2005年 | 8010篇 |
2004年 | 6014篇 |
2003年 | 5562篇 |
2002年 | 3739篇 |
2001年 | 3144篇 |
2000年 | 2997篇 |
1999年 | 3165篇 |
1998年 | 9557篇 |
1997年 | 6241篇 |
1996年 | 4837篇 |
1995年 | 3211篇 |
1994年 | 2850篇 |
1993年 | 2786篇 |
1992年 | 1676篇 |
1991年 | 1656篇 |
1990年 | 1531篇 |
1989年 | 1336篇 |
1988年 | 1188篇 |
1987年 | 875篇 |
1986年 | 901篇 |
1985年 | 926篇 |
1984年 | 813篇 |
1983年 | 704篇 |
1982年 | 705篇 |
1981年 | 688篇 |
1980年 | 569篇 |
1979年 | 481篇 |
1978年 | 419篇 |
1977年 | 540篇 |
1976年 | 968篇 |
1975年 | 301篇 |
1974年 | 279篇 |
1973年 | 262篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
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
3.
Ozdemir Erdem Tevfik Kartal Ugur Dikici Tuncay Erol Mustafa Yurddaskal Metin 《Journal of Materials Science: Materials in Electronics》2021,32(23):27398-27408
Journal of Materials Science: Materials in Electronics - In this study, zinc oxide (ZnO) nanowires (NWs) were successfully produced on Zn plates through electrochemical anodization in potassium... 相似文献
4.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
5.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献
6.
Kamar M. S. Shalan A. S. Youssef W. M. Hussein A. E. M. Khawassek Y. M. Taha M. H. 《Radiochemistry》2022,64(2):244-256
Radiochemistry - Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones... 相似文献
7.
Alawiya Reslan Juliano G. Haddad Liadrine Moukendza Koundi Philippe Desprs Jean-Loup Bascands Gilles Gadea 《International journal of molecular sciences》2021,22(5)
Mosquito-borne Zika virus (ZIKV) became a real threat to human health due to the lack of vaccine and effective antiviral treatment. The virus has recently been responsible for a global outbreak leading to millions of infected cases. ZIKV complications were highlighted in adults with Guillain–Barré syndrome and in newborns with increasing numbers of congenital disorders ranging from mild developmental delays to fatal conditions. The ability of ZIKV to establish a long-term infection in diverse organs including the kidneys has been recently documented but the consequences of such a viral infection are still debated. Our study aimed to determine whether the efficiency of ZIKV growth in kidney cells relates to glucose concentration. Human kidney HK-2 cells were infected with different ZIKV strains in presence of normal and high glucose concentrations. Virological assays showed a decrease in viral replication without modifying entry steps (viral binding, internalization, fusion) under high glucose conditions. This decrease replication was associated with a lower virus progeny and increased cell viability when compared to ZIKV-infected HK-2 cells in normal glucose concentration. In conclusion, we showed for the first time that an elevated glucose level influences ZIKV replication level with an effect on kidney cell survival. 相似文献
8.
Telecommunication Systems - This paper proposes two algorithms for hybrid (Analog–Digital) beamforming in a single-user millimeter-wave (mm-wave) multi-input multi-output (MIMO) systems under... 相似文献
9.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
10.