全文获取类型
收费全文 | 4066篇 |
免费 | 98篇 |
国内免费 | 13篇 |
专业分类
化学 | 3054篇 |
晶体学 | 30篇 |
力学 | 68篇 |
数学 | 162篇 |
物理学 | 863篇 |
出版年
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 39篇 |
2019年 | 49篇 |
2018年 | 31篇 |
2017年 | 34篇 |
2016年 | 63篇 |
2015年 | 78篇 |
2014年 | 73篇 |
2013年 | 188篇 |
2012年 | 171篇 |
2011年 | 184篇 |
2010年 | 97篇 |
2009年 | 97篇 |
2008年 | 181篇 |
2007年 | 175篇 |
2006年 | 208篇 |
2005年 | 225篇 |
2004年 | 208篇 |
2003年 | 169篇 |
2002年 | 209篇 |
2001年 | 136篇 |
2000年 | 103篇 |
1999年 | 73篇 |
1998年 | 48篇 |
1997年 | 42篇 |
1996年 | 62篇 |
1995年 | 55篇 |
1994年 | 59篇 |
1993年 | 55篇 |
1992年 | 77篇 |
1991年 | 63篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 48篇 |
1985年 | 70篇 |
1984年 | 61篇 |
1983年 | 24篇 |
1982年 | 48篇 |
1981年 | 29篇 |
1980年 | 30篇 |
1979年 | 46篇 |
1978年 | 38篇 |
1977年 | 43篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1974年 | 30篇 |
1973年 | 34篇 |
排序方式: 共有4177条查询结果,搜索用时 15 毫秒
71.
We derive some rigorous results on the chiral phase transition in QCD and QCD-like theories with a large number of colors, N(c), based on the QCD inequalities and the large-N(c) orbifold equivalence. We show that critical phenomena and associated soft modes are forbidden in flavor-symmetric QCD at finite temperature T and finite but not so large quark chemical potential μ for any nonzero quark mass. In particular, the critical point in QCD at a finite baryon chemical potential μ(B)=N(c)μ is ruled out, if the coordinate (T, μ) is outside the pion condensed phase in the corresponding phase diagram of QCD at a finite isospin chemical potential μ(I)=2μ. 相似文献
72.
73.
74.
Patterson JR Barker A Briere RA Gibbons LK Makoff G Papadimitriou V Somalwar S Wah YW Winstein B Winston R Woods M Yamamoto H Swallow E Bock GJ Coleman R Enagonio J Hsiung YB Stanfield K Stefanski R Yamanaka T Blair G Gollin GD Karlsson M Okamitsu JK Tschirhart R Brisson JC Debu P Peyaud B Turlay R Vallage B 《Physical review letters》1990,64(13):1491-1494
75.
Brick DH Widgoff M Beilliere P Lutz P Narjoux JL Gelfand N Alyea ED Bloomer M Bober J Busza W Cole B Frank TA Fuess TA Grodzins L Hafen ES Haridas P Huang D Huang HZ Hulsizer R Kistiakowsky V Ledoux RJ Milstene C Noguchi S Oh SH Pless IA Steadman S Stoughton TB Suchorebrow V Tether S Trepagnier PC Wadsworth BF Wu Y Yamamoto RK Cohn HO Calligarich E Castoldi C Dolfini R Introzzi G Ratti S Badiak M DiMarco R Jacques PF Kalelkar M Plano RJ Stamer PE Brucker EB Koller EL Alexander G Grunhaus J 《Physical review D: Particles and fields》1990,41(3):765-773
76.
Photoluminescence (PL) properties of SiO2 films containing Si nanocrystals (nc-Si) and Er3+ (Yb3+) were studied. PL peaks attributable to the recombination of electron–hole pairs in nc-Si (1.5eV) and the intra-4f shell transition of Er3+ (0.81eV) (Yb3+ (1.26eV)) were observed simultaneously at room temperature. Correlation of the two peaks was studied as a function of nanocrystalline size. It was found that the intensity of the Er3+-related (Yb3+-related) peak increases drastically as the size of nc-Si decreases. Temperature dependence of PL spectra was studied. In the case of Yb-doped samples, temperature quenching of the PL became small as the size decreased, while in the case of Er-doped samples, no remarkable temperature dependence was observed. Two major features of the quantum size effects of nc-Si, i.e., the band-gap widening and the increase in the PL efficiency with decreasing the size, are thought to contribute to the improvement of room temperature PL efficiency of Er3+ (Yb3+). 相似文献
77.
Optical Review - This paper proposes a novel steganography method to show an aerial image that is formed with aerial imaging by retro-reflection by use of dual transparent balls made of acrylic... 相似文献
78.
Hiroaki Yamamoto Youji Kanie Masakazu Arakawa Keiji Taniguchi 《Applied Physics A: Materials Science & Processing》1990,50(6):577-581
The transmission coefficient and the resonance condition in the one-dimensional rectangular double-, triple-, quadruple-, and quintuple-barrier structures are derived theoretically under the assumption of the constant tunneling effective mass. It is found that the resonance energies are different from the eigenvalues in the quantum well due to coupling between wells in the multiple-barrier (much more than triple-barrier) structures. It is confirmed that the transmission spectrum is a Lorentzian near to energies of resonance. 相似文献
79.
Graphene oxide (GO) particles in aqueous dispersions can form liquid crystal (LC) phases at extremely low concentrations due to the extremely high aspect ratio of the flakes and noticeably, they possess an extremely large Kerr coefficient attractive for low power consumption electro‐optic devices. Reduced graphene does not easily form LC phases in water due to its hydrophobic nature but here we show that stable dispersions of reduced graphene oxide can be realized with surfactants and that they exhibit birefringence upon shearing as well as under application of electric fields. The performance of the system is largely superior to GO LC possessing longer time stability and drastically improved electro‐optic properties with an induced birefringence twice as large at the same field strength thanks to the almost recovery of graphene properties upon reduction. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
80.
A Si-based light emitter has long been the final key component for electronic and photonic integrated circuits on Si, because Si has an indirect band gap. Atomistic and electronic structures and energy gains of formation of possible nitrogen (N) and fluorine (F) complexes in Si have been researched from first-principles, in order to engineer the band structure of Si for light emission. The calculated results show that the substitutional nitrogen NS and bond center fluorine FBC pair complex has large stabilization energy, and that the pair-complex-doped Si has direct band gap, which is reduced with respect to that of Si. These results lead to the possibilities of doping-based engineering of Si optical properties with introduction of deep-level impurity and charge compensation. 相似文献