全文获取类型
收费全文 | 158140篇 |
免费 | 2424篇 |
国内免费 | 673篇 |
专业分类
电工技术 | 3236篇 |
综合类 | 196篇 |
化学工业 | 25508篇 |
金属工艺 | 6008篇 |
机械仪表 | 5340篇 |
建筑科学 | 4540篇 |
矿业工程 | 379篇 |
能源动力 | 4156篇 |
轻工业 | 17902篇 |
水利工程 | 1158篇 |
石油天然气 | 624篇 |
武器工业 | 5篇 |
无线电 | 21594篇 |
一般工业技术 | 30158篇 |
冶金工业 | 24157篇 |
原子能技术 | 2406篇 |
自动化技术 | 13870篇 |
出版年
2021年 | 986篇 |
2019年 | 1011篇 |
2018年 | 1300篇 |
2017年 | 1348篇 |
2016年 | 1511篇 |
2015年 | 1282篇 |
2014年 | 2107篇 |
2013年 | 7004篇 |
2012年 | 3627篇 |
2011年 | 5120篇 |
2010年 | 3932篇 |
2009年 | 4538篇 |
2008年 | 4978篇 |
2007年 | 5158篇 |
2006年 | 4617篇 |
2005年 | 4325篇 |
2004年 | 4197篇 |
2003年 | 4072篇 |
2002年 | 4094篇 |
2001年 | 4117篇 |
2000年 | 3859篇 |
1999年 | 3807篇 |
1998年 | 6824篇 |
1997年 | 5359篇 |
1996年 | 4535篇 |
1995年 | 3782篇 |
1994年 | 3418篇 |
1993年 | 3236篇 |
1992年 | 2815篇 |
1991年 | 2723篇 |
1990年 | 2652篇 |
1989年 | 2633篇 |
1988年 | 2469篇 |
1987年 | 2179篇 |
1986年 | 2130篇 |
1985年 | 2566篇 |
1984年 | 2329篇 |
1983年 | 2205篇 |
1982年 | 2072篇 |
1981年 | 1994篇 |
1980年 | 1864篇 |
1979年 | 1880篇 |
1978年 | 1772篇 |
1977年 | 2089篇 |
1976年 | 2572篇 |
1975年 | 1586篇 |
1974年 | 1430篇 |
1973年 | 1454篇 |
1972年 | 1196篇 |
1971年 | 1115篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Shin Hansub Sim Sungyong Kwon Hyukyoon Hwang Sangheum Lee Younho 《International Journal of Information Security》2022,21(1):25-36
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone... 相似文献
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.
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
4.
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
5.
Tuladhar Sanira Alsadoon Abeer Prasad P. W. C. Ali Akbas Ezaldeen Alrubaie Ahmad 《Multimedia Tools and Applications》2022,81(17):23845-23865
Multimedia Tools and Applications - Gastrointestinal stromal tumor is one of the critical tumors that doctors do not suggest to get frequent endoscopy, so there is a need for a diagnosis system... 相似文献
6.
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
7.
8.
9.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
10.