首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   158140篇
  免费   2424篇
  国内免费   673篇
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
  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.
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.
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.
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.
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.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号