全文获取类型
收费全文 | 29015篇 |
免费 | 4980篇 |
国内免费 | 4220篇 |
专业分类
化学 | 21244篇 |
晶体学 | 461篇 |
力学 | 2008篇 |
综合类 | 279篇 |
数学 | 3312篇 |
物理学 | 10911篇 |
出版年
2024年 | 54篇 |
2023年 | 495篇 |
2022年 | 826篇 |
2021年 | 946篇 |
2020年 | 1050篇 |
2019年 | 1086篇 |
2018年 | 970篇 |
2017年 | 979篇 |
2016年 | 1452篇 |
2015年 | 1386篇 |
2014年 | 1686篇 |
2013年 | 2137篇 |
2012年 | 2629篇 |
2011年 | 2654篇 |
2010年 | 1875篇 |
2009年 | 1878篇 |
2008年 | 2114篇 |
2007年 | 1904篇 |
2006年 | 1793篇 |
2005年 | 1489篇 |
2004年 | 1205篇 |
2003年 | 996篇 |
2002年 | 1101篇 |
2001年 | 941篇 |
2000年 | 703篇 |
1999年 | 637篇 |
1998年 | 478篇 |
1997年 | 368篇 |
1996年 | 390篇 |
1995年 | 365篇 |
1994年 | 270篇 |
1993年 | 228篇 |
1992年 | 194篇 |
1991年 | 189篇 |
1990年 | 165篇 |
1989年 | 136篇 |
1988年 | 106篇 |
1987年 | 87篇 |
1986年 | 69篇 |
1985年 | 56篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1957年 | 7篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
42.
针对VO2薄膜在微测辐射热计上的应用,采用射频反应溅射法,在室温下制备氧化钒薄膜;研究了氧分压对薄膜沉积速率、电学性质及成分的影响.通过调节氧分压,先获得成分接近VO2的非晶化薄膜,再在400℃空气中氧化退火,便可制得高电阻温度系数,低电阻率的VO2薄膜,电阻温度系数约为-4%/℃,薄膜方块电阻为R□为100—300kΩ;薄膜在室温下沉积,400℃下退火的制备方法与微机电加工(micro electromechanic
关键词:
二氧化钒
电阻温度系数
氧分压
射频反应溅射法 相似文献
43.
High index of refraction via quantum interference in a three-level system of Er^3+-doped yttrium aluminium garnet crystal
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A simple three-level system is proposed to produce high index of refraction with zero absorption in an Er^3+-doped yttrium aluminium garnet (YAG) crystal, which is achieved for a probe field between the excited state 4I13/2 and ground state 4I15/2 by adjusting a strong coherent driving field between the upper excited state 4I11/2 and 4I15/2. It is found that the changes of the frequency of the coherent driving field and the concentration of Er^3+ ions in the YAG crystal can maximize the index of refraction accompanied by vanishing absorption. This result could be useful for the dispersion compensation in fibre communication, laser particle acceleration, high precision magnetometry and so on. 相似文献
44.
45.
Jian Shen Huizhong Zeng Zhihong Wang Shengbo Lu Huidong Huang Jingsong Liu 《Applied Surface Science》2006,252(22):8018-8021
Polycrystalline Pb(Zr0.55Ti0.45)O3 thin film was deposited on Pt/Ti/SiO2/Si(1 0 0) by radio-frequency-magnetron sputtering method, and the writing of charge bits on the surface of PZT thin film was studied by Kelvin probe force microscopy. It is found that the surface potential of the negative charge bits are higher than those of the corresponding positive ones. When ferroelectric polarization switching occurs, the potential difference becomes even more remarkable. A qualitative model was proposed to explain the origin of the asymmetric charge writing. It is demonstrated that the internal field in the interface layer, which is near the ferroelectric/electrode interface in ferroelectric film, is likely to be the cause for the occurrence of this phenomenon. 相似文献
46.
Junxiang Zhang Yabin Dong Haihong Wang Jiangrui Gao 《量子光学学报》2006,12(B08):74-74
The quantum coherence effects of the transition Fe = 2←→Fg = 3 depending on the polarization of the coupling and probe beam are observed in a Cs vapor cell. The splitting of electromagnetically induced transparency (EIT) window is observed when the degeneracy of two-level system is broken using a magnetic field. It is also shown that the splitted transparency points of two of three windows are shifted with the intensity of magnetic field ( i. e. Zeeman splitting in the upper and lower levels ) increasing. On the contrary, when we fix the intensity of magnetic field, and increase the Rabi frequency of the coupling beam, the splitted transparency peaks become wider. A qualitative agreement between experiment and theory is found. 相似文献
47.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
49.
设函数f(w)为凸区域D内的单叶解析函数,对于2≤n≤8和所有w∈D,本文得到估计式|f(n)(w)/f'(w)|的精确上界.这个结果推广了一些已知的结论. 相似文献
50.
溴酸钾-亚甲蓝催化光度法测定硝酸盐和亚硝酸盐 总被引:16,自引:1,他引:15
用镉柱将NO-3 还原为NO-2 ,利用在磷酸介质中NO-2 对溴酸钾氧化亚甲蓝这一褪色反应具有强烈的催化作用而建立了同时测定痕量硝酸盐和亚硝酸盐的新方法。本方法简便、快速、灵敏 ,对亚硝酸盐和硝酸盐测定的线性范围分别为 0~ 2 0 0 μg·L-1和 0 0 0 3~ 310 μg·L-1,用于测定各种水样中痕量NO-2 和NO-3 的含量均获得满意结果 相似文献