全文获取类型
收费全文 | 1791篇 |
免费 | 21篇 |
国内免费 | 10篇 |
专业分类
化学 | 983篇 |
晶体学 | 11篇 |
力学 | 61篇 |
数学 | 228篇 |
物理学 | 539篇 |
出版年
2020年 | 15篇 |
2018年 | 13篇 |
2016年 | 14篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 87篇 |
2012年 | 81篇 |
2011年 | 87篇 |
2010年 | 56篇 |
2009年 | 23篇 |
2008年 | 53篇 |
2007年 | 78篇 |
2006年 | 54篇 |
2005年 | 59篇 |
2004年 | 61篇 |
2003年 | 56篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 52篇 |
1999年 | 31篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 38篇 |
1995年 | 30篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 36篇 |
1990年 | 27篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 41篇 |
1978年 | 24篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1975年 | 19篇 |
1974年 | 34篇 |
1973年 | 32篇 |
1972年 | 14篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1969年 | 16篇 |
排序方式: 共有1822条查询结果,搜索用时 15 毫秒
51.
S. Feng K. Halterman P.L. Overfelt J.M. Elson G.A. Lindsay M.J. Roberts 《Applied Physics A: Materials Science & Processing》2007,87(2):235-244
We present an overview of some of our work on transmission properties and mode characteristics of layered metamaterials and
their potential applications. In particular, we will show how layered metamaterials exhibit unusual transmission properties
and unconventional features of guided modes, such as resonance-induced transparency in multilayer structures and slope reversal
of dispersion curves in coupled waveguides.
PACS 78.67.-n; 73.21.Ac; 61.46.+w; 42.25.Bs; 42.82.Et 相似文献
52.
James B. Gerken Claire Badger Christopher Bisbee Sasha Gardner Yan Qi Víctor Durà Vilà John D. Roberts 《Journal of Physical Organic Chemistry》2008,21(3):193-197
Conformational preferences of glutaric, 3‐hydroxyglutaric and 3‐methylglutaric acid, and their mono‐ and dianions have been investigated with the aid of NMR spectroscopy. In contrast to succinic acid, glutaric acid displays essentially statistical conformational equilibria in polar and non‐polar solutions of high and low hydrogen‐bonding ability with no clear evidence for intramolecular hydrogen‐bonding interactions. The acid ionization constant ratios, K 1/K2, in D2O and DMSO of glutaric, 3‐hydroxyglutaric, and 3‐methylglutaric acids also indicate that intramolecular interactions are much less important than, or indeed insignificant, for shorter‐chain acids. FTIR studies on 3‐methylglutaric acid indicate some preference for either association with solvent or dimerization, depending on the solvent, rather than intramolecular hydrogen bonding. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
53.
Mohy S. Mansour Ayman M. Elbaz William L. Roberts Mohamed F. Zayed Mrinal Juddoo Bassem M. Akoush Alaa M. Khedr Hazem M. Al-Bulqini Assaad R. Masri 《Proceedings of the Combustion Institute》2021,38(2):2597-2606
Turbulent flames with compositionally inhomogeneous mixtures are common in many combustion systems. Turbulent jet flames with a circular nozzle burner were used earlier to study the impact of inhomogeneous mixtures, and these studies showed that the nozzle radius affects the flame stability. Accordingly, planar turbulent flames with inhomogeneous turbulent jet are created in a concentric flow slot burner (CFSB) to avoid this effect in the present study. The stability characteristics, the mixing field structure, and the flame front structure were measured, and the correlations between stability and the mixing field structure were investigated. The mixture fraction field was measured in non-reacting jets at the nozzle exit using highly resolved Rayleigh scattering technique, and the flame front was measured in some selected turbulent flames using high-speed Planar Laser-Induced Fluorescence (PLIF) of OH technique. The data show strong correlations between flame stability and the range of mixture fraction fluctuations. The flames are highly stabilized within a mixing field environment with the range of fluctuation in mixture fraction close to the range of the flammability limits. The mixing field structure is also illustrated and discussed using a mixing regime diagram and showed that the scatter of the data of the different cases is consistent with the classified mixing regimes. Lean flames are stabilized in the current slot burner. The flame front structure topology varies consistently from thin, small curvature at the low level of turbulence and higher equivalence ratio to more wrinkled, larger curvature, but a thicker structure at a higher level of turbulence and lower equivalence ratio. 相似文献
54.
S.M Roberts 《Journal of Mathematical Analysis and Applications》1983,97(1):245-265
The analytical and approximate soluions of ?y″ = yy′ are developed and compared, and the analytical solution is evaluated numerically. The analytical soluion has several interesting properties: (i) it possesses three different types of solutions, constant, exponential, and tangent; (ii) for a two-point boundary value problem it has an undecidability aspect relative to which solution type holds; (iii) for the tangent solution type an infinite number of solutions exist, both continuous and discontinuous; (iv) even with the analytical solution known, its numerical evaluation can still be difficult to generate. 相似文献
55.
Detlev Buchholz Sergio Doplicher Roberto Longo John E. Roberts 《Communications in Mathematical Physics》1993,155(1):123-134
We characterize the automorphisms of aC
*-algebra which extend to automorphisms of the crossed product by a compact group dual. The case where the inclusion is equipped with a group of automorphisms commuting with the dual action is also treated. These results are applied to the analysis of broken gauge symmetries in Quantum Field Theory to draw conclusions on the structure of the degenerate vacua on the field algebra.Dedicated to Huzihiro ArakiResearch supported by MURST and CNR, GNAFA 相似文献
56.
Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Whitmore J Wilson P Butler F Fu X Kalbfleisch G Lambrecht M Ross WR Skubic P Snow J Wang PL Wood M Bortoletto D Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Schaffner SF Shibata EI Shipsey IP Wang PN Battle M Ernst J Kroha H Roberts S Sparks K Thorndike EH Wang CH Dominick J Sanghera S Skwarnicki T Stoynowski R Artuso M He D Goldberg M Horwitz N Kennett R 《Physical review letters》1993,71(20):3259-3262
57.
Akchurin N Langland J Onel Y Bonner BE Corcoran MD Cranshaw J Nessi-Tedaldi F Nessi M Nguyen C Roberts JB Skeens J White JL Bravar A Giacomich R Penzo A Schiavon P Zanetti A Bystricky J Lehar F de Lesquen A van Rossum L Cossairt JD Read AL Derevschikov AA Matulenko YA Meschanin AP Nurushev SB Patalakha DI Rykov VL Solovyanov VL Vasiliev AN Grosnick DP Hill DA Laghai M Lopiano D Ohashi Y Shima T Spinka H Stanek RW Underwood DG Yokosawa A Funahashi H Goto Y Imai K Itow Y Makino S Masaike A 《Physical review D: Particles and fields》1993,48(7):3026-3036
58.
We demonstrate a high-power, narrowband pulsed source at 390 nm by two stages of frequency doubling in periodically poled MgO:LiNbO(3) and periodically poled KTiOPO(4) of an amplified, passively mode-locked fiber laser. With a frequency quadrupling efficiency of 5.5% and a 0.1 nm bandwidth, the 250 mW ultraviolet source is a suitable compact pump source for many entanglement-based quantum information processing tasks. 相似文献
59.
Jack I. Jones D. R. T. Roberts K. L. 《Zeitschrift fur Physik C Particles and Fields》1994,63(1):151-159
For some years there has been uncertainty over whether regularisation by dimensional reduction (DRED) is viable for non-supersymmetric theories. We resolve this issue by showing that DRED is entirely equivalent to standard dimensional regularisation (DREG), to all orders in perturbation theory and for a general renormalisable theory. The two regularisation schemes are related by an analytic redefinition of the couplings, under which the -functions calculated using DRED transform into those computed in DREG. TheS-matrix calculated using DRED is numerically equal to the DREG version, ensuring that both schemes give the same physics. 相似文献
60.
Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Butler F Fu X Kalbfleisch G Ross WR Skubic P Snow J Wang PL Wood M Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Payne D Shibata EI Shipsey IP Wang PN Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH Dominick J Lambrecht M Sanghera S Shelkov V Skwarnicki T Stroynowski R Volobouev I Wei G 《Physical review D: Particles and fields》1994,50(1):43-68