全文获取类型
收费全文 | 15342篇 |
免费 | 3817篇 |
国内免费 | 1411篇 |
专业分类
化学 | 9876篇 |
晶体学 | 205篇 |
力学 | 148篇 |
综合类 | 76篇 |
数学 | 105篇 |
物理学 | 10160篇 |
出版年
2024年 | 35篇 |
2023年 | 129篇 |
2022年 | 455篇 |
2021年 | 576篇 |
2020年 | 706篇 |
2019年 | 577篇 |
2018年 | 522篇 |
2017年 | 590篇 |
2016年 | 807篇 |
2015年 | 807篇 |
2014年 | 1146篇 |
2013年 | 1474篇 |
2012年 | 1066篇 |
2011年 | 1105篇 |
2010年 | 884篇 |
2009年 | 983篇 |
2008年 | 977篇 |
2007年 | 1097篇 |
2006年 | 959篇 |
2005年 | 739篇 |
2004年 | 626篇 |
2003年 | 601篇 |
2002年 | 497篇 |
2001年 | 448篇 |
2000年 | 420篇 |
1999年 | 347篇 |
1998年 | 310篇 |
1997年 | 290篇 |
1996年 | 226篇 |
1995年 | 191篇 |
1994年 | 174篇 |
1993年 | 138篇 |
1992年 | 107篇 |
1991年 | 81篇 |
1990年 | 87篇 |
1989年 | 61篇 |
1988年 | 58篇 |
1987年 | 51篇 |
1986年 | 44篇 |
1985年 | 35篇 |
1984年 | 43篇 |
1983年 | 9篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1970年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
991.
Shigeru Masuda 《Applied Surface Science》2010,256(13):4054-4064
A systematic understanding and controlling of gap states formed at the organic-metal interfaces is a key factor for fabricating functional organic-metal systems, as in case of heterojunctions in semiconductor devices. We report here the characterization of gap states near the Fermi level of metal substrate by metastable atom electron spectroscopy and first-principles density functional calculations. The gap states in organic-metal systems are classified into two types, i.e., chemisorption-induced gap states (CIGSs) and complex-based gap states (CBGSs). CIGSs can be further classified whether the metal wave function tails a short distance into the chemisorbed species with the exponential decay (damping type) or is exposed sufficiently to the chemisorbed species by mixing with the organic orbitals (propagating type). CIGSs observed in alkanethiolate and C60 on Pt(1 1 1) are their typical examples, respectively. As a consequence, alkanethiolate serves as a poor mediator of metal wave function, whereas C60 acts as a good mediator, which is responsible for tunneling mechanism and eventually electric conductivity in the relevant metal-organic-metal junctions. CBGSs are identified in bathocuproine films deposited on K-covered Au, where the K atoms migrate into the film to form an organic-metal complex. The CBGSs are distributed over the multilayer film, in contrast to the case of CIGS. With increasing film thickness, the CBGSs exhibit incommensurate energy shifts with the valence band top of the film, indicating that the Schottky-Mott model breaks down as evaluating charge transport in organic-metal systems. 相似文献
992.
993.
Structural Manipulation of Ruthenium(II) Polypyridine Nitrone Complexes to Generate Phosphorogenic Bioorthogonal Reagents for Selective Cellular Labeling
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tommy Siu‐Ming Tang Dr. Hua‐Wei Liu Prof. Kenneth Kam‐Wing Lo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9649-9659
We report a new class of ruthenium(II) polypyridine complexes functionalized with a nitrone group as phosphorogenic bioorthogonal probes. These complexes were very weakly emissive owing to rapid C=N isomerization of the nitrone moiety, but exhibited significant emission enhancement upon strain‐promoted alkyne–nitrone cycloaddition (SPANC) reaction with bicyclo[6.1.0]nonyne (BCN)‐modified substrates. The modification of nitrone with a dicationic ruthenium(II) polypyridine unit at the α‐C‐position and a phenyl ring at the N‐position led to remarkably accelerated reaction kinetics, which are substantially greater (up to ≈278 fold) than those of other acyclic nitrone–BCN systems. Interestingly, the complexes achieved specific cell membrane/cytosol staining upon specific labeling of an exogenous substrate, BCN‐modified decane (BCN‐C10), in live cells. Importantly, the in situ generation of the more lipophilic isoxazoline adduct in the cytoplasm resulted in increased cytotoxicity, highlighting a novel approach to apply the SPANC labeling technique in drug activation. 相似文献
994.
Pu Zhang Rongqiang Zhuang Zhide Guo Prof. Xinhui Su Prof. Xiaoyuan Chen Prof. Xianzhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16783-16786
A convenient and quantitative radioiodination method by copper‐mediated cross‐coupling of aryl boronic acids was developed. The mild labeling conditions, ready availability of the boronic acid substrate, simple operation, broad functional group tolerance and excellent radiochemical yield (RCY) make this a practical strategy for radioiodine labeling without further purification. 相似文献
995.
996.
Material structures and device structures of a 100-GHz InP based transferred-electron device are designed in this paper. In order to successfully fabricate the Gunn devices operating at 100 GHz, the InP substrate was entirely removed by mechanical thinning and wet etching. The Gunn device was connected to a tripler link and a high RF(radio frequency)output with power of 2 mW working at 300 GHz was obtained, which is high enough for applications in current military electronic systems. 相似文献
997.
C. Aymes‐Chodur S. Esnouf A. Le Moël 《Journal of Polymer Science.Polymer Physics》2001,39(13):1437-1448
The fluoropolymer poly(vinylidene fluoride) was irradiated with γ rays to induce a polystyrene (PS) radiation grafting via an indirect method. Electron spin resonance and Fourier transform infrared studies were performed to identify the species that initiated the PS grafting. Specific experiments were performed to prove separately the importance of each kind of radical. A localization of the radicals in this irradiated polymer is proposed, and a kinetic model of the grafting is given. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1437–1448, 2001 相似文献
998.
A. Coppa V. Foglietti E. Giovine A. Doria G.P. Gallerano E. Giovenale A. Cetronio C. Lanzieri M. Peroni F. Evangelisti 《Infrared Physics & Technology》2008,51(5):470-472
An active two dimensional near field imaging of a High Electron Mobility Transistor (HEMT) used as THz detector has been performed. The reflective imaging system developed at the ENEA FEL Facility in Frascati has been used to this purpose. This imaging technique has shown to be particularly powerful in resolving various coupling mechanisms of the incident radiation with the device. 相似文献
999.
Influence of Ⅴ/Ⅲ ratio on the structural and photoluminescence properties of In0.52AlAs/In0.53GaAs metamorphic high electron mobility transistor grown by molecular beam epitaxy
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A series of metamorphic high electron mobility transistors (MMHEMTs) with different Ⅴ/Ⅲ flux ratios are grown on CaAs (001) substrates by molecular beam epitaxy (MBE). The samples are analysed by using atomic force microscopy (AFM), Hall measurement, and low temperature photoluminescence (PL). The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square (RMS) roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/(V.s) and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed. 相似文献
1000.
The significant modifications to our recently constructed electron momentum spectrometer have been implemented. Compared with our previous report, the energy and the angle resolutions are significantly improved and reach △E = 0.45 eV, △θ = ±0.53° and △φ = ±0.84°, respectively. Moreover, the details of data reduction and the relation between azimuthal angle range and the sensitivity are discussed. 相似文献