全文获取类型
收费全文 | 68054篇 |
免费 | 12334篇 |
国内免费 | 15187篇 |
专业分类
化学 | 26680篇 |
晶体学 | 1690篇 |
力学 | 3121篇 |
综合类 | 1557篇 |
数学 | 6510篇 |
物理学 | 19565篇 |
无线电 | 36452篇 |
出版年
2024年 | 381篇 |
2023年 | 1075篇 |
2022年 | 2645篇 |
2021年 | 2570篇 |
2020年 | 2203篇 |
2019年 | 2081篇 |
2018年 | 2109篇 |
2017年 | 2950篇 |
2016年 | 2262篇 |
2015年 | 3444篇 |
2014年 | 4158篇 |
2013年 | 5150篇 |
2012年 | 5449篇 |
2011年 | 5816篇 |
2010年 | 5736篇 |
2009年 | 5949篇 |
2008年 | 6339篇 |
2007年 | 5923篇 |
2006年 | 5720篇 |
2005年 | 4683篇 |
2004年 | 3684篇 |
2003年 | 2467篇 |
2002年 | 2456篇 |
2001年 | 2402篇 |
2000年 | 2474篇 |
1999年 | 1193篇 |
1998年 | 552篇 |
1997年 | 406篇 |
1996年 | 400篇 |
1995年 | 317篇 |
1994年 | 315篇 |
1993年 | 337篇 |
1992年 | 261篇 |
1991年 | 224篇 |
1990年 | 194篇 |
1989年 | 184篇 |
1988年 | 184篇 |
1987年 | 164篇 |
1986年 | 119篇 |
1985年 | 82篇 |
1984年 | 99篇 |
1983年 | 86篇 |
1982年 | 55篇 |
1981年 | 49篇 |
1980年 | 47篇 |
1979年 | 45篇 |
1978年 | 18篇 |
1971年 | 11篇 |
1965年 | 24篇 |
1959年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
LIU Shu-ping JIA Yue-hu 《半导体光子学与技术》2006,12(1):21-24
According to Maxwell's theory, the optical transmission characteristics in GeSi/Si superlattice nanocrystalline layer have been analyzed and calculated. The calculated result shows that when the total thickness L is 340 nm, the single mode lightwave can be transmitted only at periodic number M≥15.5. In addition, at the direction of transmission, when the transmission distance is larger than 500 μm, the lightwave intensity is decreased greatly. Based on the above parameters, the design and manufacture of GeSi/Si superlattice nanocrystalline photodetector are carried out. 相似文献
43.
44.
Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films 下载免费PDF全文
Helium-charged nanocrystalline titanium films have been deposited by HeAr magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60℃ to 350℃ while the other deposition'parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 20 angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening. 相似文献
45.
Total Dose Radiation Tolerance of Phase Change Memory Cell with GeSbTe Alloy 总被引:1,自引:0,他引:1 下载免费PDF全文
Phase change memory (PCM) cell array is fabricated by a standard complementary metal-oxide-semiconductor process and the subsequent special fabrication technique. A chalcogenide Ge2Sb2Te5 film in thickness 50hm deposited by rf magnetron sputtering is used as storage medium for the PCM cell. Large snap-back effect is observed in current-voltage characteristics, indicating the phase transition from an amorphous state (higher resistance state) to the crystalline state (lower resistance state). The resistance of amorphous state is two orders of magnitude larger than that of the crystalline state from the resistance measurement, and the threshold current needed for phase transition of our fabricated PCM cell array is very low (only several μA). An x-ray total dose radiation test is carried out on the PCM cell array and the results show that this kind of PCM cell has excellent total dose radiation tolerance with total dose up to 2 ×10^6 rad(Si), which makes it attractive for space-based applications. 相似文献
46.
47.
48.
49.
50.
Entangled states based on two coherent states 3π/2 out of phase with each other, i.e. |α〉 and e^iФ|-iα〉, as well as on a special state with a relative phase Ф = |α|^2, are constructed. By analysing the amount of entanglement it is evident that entangled states based on this special state can be used as an excellent resource for quantum teleportation. It is also revealed that these entangled states possess some nonclassical features. 相似文献