全文获取类型
收费全文 | 280篇 |
免费 | 35篇 |
国内免费 | 2篇 |
专业分类
化学 | 229篇 |
晶体学 | 1篇 |
力学 | 6篇 |
综合类 | 4篇 |
数学 | 21篇 |
物理学 | 56篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 20篇 |
2011年 | 15篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有317条查询结果,搜索用时 15 毫秒
61.
We report on the structures and electro‐optical properties of epoxy/acrylic polymer‐dispersed liquid‐crystal (PDLC) films. A thermal stimulated current (TSC) analysis was used to investigate the physical structures of PDLC. In the TSC spectrum of PDLC, three relaxation peaks were observed: the glass transition of the liquid crystal, the glass transition of the polymer matrix, and the ρ transition. The ρ transition represents the discharge behavior of space charges, and its intensity increased as the curing time and content of the curing agent dicyandiamide (DICY) increased. The pre‐UV‐cured films with different DICY contents were thermally cured at 130 °C for various periods. The electro‐optical properties of PDLC, such as the contrast ratio and switching voltage, increased as the curing time of DICY, the content of DICY, or both increased. As the ambient temperature increased from 10 to 40 °C, the contrast ratio and switching voltage of PDLC gradually decreased. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 507–514, 2001 相似文献
62.
Androić D Armstrong DS Arvieux J Bailey SL Beck DH Beise EJ Benesch J Benmokhtar F Bimbot L Birchall J Bosted P Breuer H Capuano CL Chao YC Coppens A Davis CA Ellis C Flores G Franklin G Furget C Gaskell D Gericke MT Grames J Guillard G Hansknecht J Horn T Jones MK King PM Korsch W Kox S Lee L Liu J Lung A Mammei J Martin JW McKeown RD Micherdzinska A Mihovilovic M Mkrtchyan H Muether M Page SA Papavassiliou V Pate SF Phillips SK Pillot P Pitt ML Poelker M Quinn B Ramsay WD Real JS Roche J 《Physical review letters》2012,108(12):122002
The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Δ)- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d(Δ)- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A(γ)-=-5.2 to +5.2 ppm. The measurement performed in this work leads to A(γ)-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V(ud)/V(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering. 相似文献
63.
Fomin N Arrington J Asaturyan R Benmokhtar F Boeglin W Bosted P Bruell A Bukhari MH Christy ME Chudakov E Clasie B Connell SH Dalton MM Daniel A Day DB Dutta D Ent R El Fassi L Fenker H Filippone BW Garrow K Gaskell D Hill C Holt RJ Horn T Jones MK Jourdan J Kalantarians N Keppel CE Kiselev D Kotulla M Lindgren R Lung AF Malace S Markowitz P McKee P Meekins DG Mkrtchyan H Navasardyan T Niculescu G Opper AK Perdrisat C Potterveld DH Punjabi V Qian X Reimer PE Roche J Rodriguez VM Rondon O 《Physical review letters》2012,108(9):092502
We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate. 相似文献
64.
With an aim to develop environment friendly and inexpensive materials for electrochemical capacitor electrodes, nanocrystalline γ‐MnO2 with layered architecture of schist‐like structure was successfully synthesized by reducing mixed MnSO4×H2O and CTAMnO4 precursors in stoichiometric amounts through a hydrothermal process. The as‐prepared MnO2 was characterized by field emission scanning electron microscopy, X‐ray diffraction, and thermal gravimetric analysis. Also, cyclic voltammetry was employed to investigate the electrochemical properties of the products in neutral KCl aqueous solution, showing a higher enhanced capacitive performance than that of the sample without a coating of schist‐like γ‐MnO2, indicating that our MnO2‐based electrode provides a promising opportunity for high‐performance energy storage devices. 相似文献
65.
Dasu S de Barbaro P Bodek A Harada H Krasny MW Lang K Riordan EM Andivahis L Arnold R Benton D Bosted P deChambrier G Lung A Rock SE Szalata ZM Walker RC Filippone BW Jourdan J Milner R McKeown R Potterveld D Para A Dietrich F Van Bibber K Button-Shafer J Debebe B Hicks RS Gearhart R Whitlow LW Alster J 《Physical review D: Particles and fields》1994,49(11):5641-5670
66.
Density functional theory (DFT) calculations have been performed to elucidate the reaction mechanism of hydrosilylation of carbonyl compounds catalyzed by high-valent rhenium(V)-di-oxo complexes ReO2I(PR3)2 (R = Me, Ph). The calculations suggest that the most favorable mechanism involves the rate-determining dissociative [2 + 2] addition of the Si-H bond across a Re=O bond to form a Re(V) hydrido siloxy intermediate; this is followed by carbonyl coordination, reduction of the carbonyl, rearrangement, and final intramolecular nucleophilic attack from the alkoxy group to the silyl center (dissociative retro-[2 + 2] addition). It was also found that the additional oxo ligand in the ReO2I(PR3)2 complexes promotes the [2 + 2] addition across the rhenium-oxo bond both kinetically and thermodynamically, as compared to the neutral rhenium(V)-mono-oxo complex ReOCl3(PMe3)2. The effect of different silanes on the [2 + 2] addition barriers is also studied. 相似文献
67.
The automorphism group AutFn of a free group Fn of rank n acts on the product of n copies of a group G by substituting n elements of G into the words defining an automorphism of the free group. This gives rise to an antihomomorphism from AutFnto a permutation group. We determine this antihomomorphic image of AutFn when G is the semidirect product Zp x Zq 相似文献
68.
69.
Geert-Jan Boons Peter Grice Ray Leslie Steven V Ley Lam Lung Yeung 《Tetrahedron letters》1993,34(52):8523-8526
The reactivity of dispiroketal protected thioglycosides makes them useful new precursors for oligossaccharide synthesis as is illustrated by the preparation of a protected pentasaccharide unit common to the variant surface glycoprotein of Trypanosoma brucei. 相似文献
70.
Lung Kwang Pan Che Chung Wang Ying Ching Hsiao Kye Chyn Ho 《Optics & Laser Technology》2005,37(1):33-42
The use of an Nd:YAG laser for thin plate magnesium alloy butt welding was optimized using the Taguchi analytical methodology. The welding parameters governing the laser beam in thin plate butt welding were evaluated by measuring of the ultimate tension stress. The effectiveness of the Taguchi method lies in clarifying the factor that dominates complex interactions in laser welding. The factors can be the shielding gas, laser energy, convey speed of workpiece, point at which the laser is focused, pulse frequency, and pulse shape. Furthermore, 18 combinations of these six essential welding parameters were set and Taguchi's method followed exactly. The optimal result was confirmed with a superior ultimate tension stress of 169 MPa, 2.5 times larger to that from original set for laser welding. 相似文献