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991.
Kun-Rung Lin Li-Chung Kuo Man-kit Leung Kuo-Huang Hsieh 《European Polymer Journal》2007,43(10):4279-4288
Polymeric light-emitting diodes (PLEDs) using high-performance hole-transport polyurethanes (PUs) have been fabricated. The PUs were prepared from the condensation polymerization of (E, E)-1,4-bis(2-hydroxystyryl)benzene, an oligo para-phenylene-(E)-vinylene (OPV) unit, with toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane 4,4′-diisocyanate (H12MDI), respectively. The condensation polymerization was end-capped with 4-tert-butylphenol as the terminal group. The PLED having the PU layer inserted between PEDOT:PSS (HIL) and MEH-PPV (EML) demonstrated superior current efficiency and low turn-on voltage when comparing to the reference devices of ITO/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm) as well as ITO/PEDOT:PSS(30 nm)/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm). In particularly, the best device performance was realized with the PU of OPV-IPDI as the hole-transport layer, resulting 53 times and 2.72 times of current efficiency enhancement as well as 1.5 V and 1 V voltage reduction of the turn-on voltage, respectively, when compared against the reference devices. Besides, our experiments also showed that the PU polymer could also be applied for flexible PLED with similar performance enhancement. Based on the promising results, we concluded that OPV-IPDI was a good hole-transport material for light-emitting diode application. 相似文献
992.
Mao Z Huang JS Che CM Zhu N Leung SK Zhou ZY 《Journal of the American Chemical Society》2005,127(13):4562-4563
Treatment of [Cu2(dcpm)2]Y2 (dcpm = bis(dicyclohexylphosphino)methane, Y = ClO4-, BF4-, PF6-, CF3SO3-) with refluxing MeOH in the presence of KOH afforded hydride complexes [Cu3(dcpm)3(mu3-H)]Y2 (1) in about 85% yield. Refluxing [Cu2(dcpm)2](PF6)2 with MeOH in the presence of NH3.H2O and air gave a carboxylate complex [Cu2(dcpm)2(O2CCH2OH)]PF6 (2) in 40% yield. All of the complexes 1 and 2 have been characterized by X-ray crystallography. The Cu3 cores in 1 are almost perfectly shielded by the dcpm ligands. Intense photoluminescence was observed for 1 both in the solid state and in solution. 相似文献
993.
C. L. Choy K. W. Kwok W. P. Leung Felix P. Lau 《Journal of Polymer Science.Polymer Physics》1994,32(8):1389-1397
The effects of crystallinity, orientation, and short-fiber filler on the thermal diffusivity D and thermal conductivity K of poly (ether ether ketone) (PEEK) have been studied. Below the glass transition, D increases by less than 10% as the crystallinity increases from 0 to 0.3. For amorphous PEEK, there is an abrupt drop in D at the glass transition (Tg ? 420 K). The drop is less prominent for the 30% crystalline sample and occurs at 20 K higher. At a draw ratio of 2.5, the axial thermal conductivity is 2.3 times higher while the transverse thermal conductivity is 30% lower than that of the unoriented material. For an injection-molded bar of carbon fiber reinforced PEEK, the variation of D with position along the width or thickness direction is found to correlate well with the fiber orientation. By regarding the injection-molded bar as a multidirectional laminate comprising a large number of unidirectional plies, the thermal conductivities along the longitudinal and transverse direction are calculated and found to agree closely with the experimental data. © 1994 John Wiley & Sons, Inc. 相似文献
994.
The determination of the relaxation of electrons in atomic gases continues to be an important physical problem. The main interest is the determination of the time scale for the thermalization of electrons in different moderators and the nature of the timedependent electron energy distribution. The theoretical basis for the study of electron thermalization is the determination of the electron distribution function from a solution of the Lorentz–Fokker–Planck equation. The present paper considers a detailed comparison of different numerical methods of solution of the Lorentz–Fokker–Planck equation for the electron distribution function. The methods include a pseudospectral method referred to as the Quadrature Discretization Method (QDM) which is based on nonstandard polynomial basis sets, a finitedifference method, and a Lagrange interpolation method. The Fokker–Planck equation can be transformed to a Schrödinger equation, and methods developed for the solution of either equation apply to the other. 相似文献
995.
We present (29)Si, (27)Al, and (67)Zn NMR evidence to show that silicate ions in alkaline solution form complexes with zinc(II) (present as zincate, Zn(OH)(3)(-) or Zn(OH)(4)(2-)) and, concomitantly, with aluminate (Al(OH)(4)(-)). Zincate reacts with monomeric silicate at pH 14-15 to form [(HO)O(2)Si-O-Zn(OH)(3)](4-) and with dimeric silicate to produce [HO-SiO(2)-O-SiO(2)-O-Zn(OH)(3)](6-). The exchange of Si between these free and Zn-bound sites is immeasurably fast on the (29)Si NMR time scale. The cyclic silicate trimer reacts relatively slowly and incompletely with zincate to form [(HO)(3)Zn{(SiO(3))(3)}](7-). The concentration of the cyclic trimer becomes further depleted because zincate scavenges the silicate monomer and dimer, with which the cyclic trimer is in equilibrium on the time scale of sample preparation. Identification of these zincate-silicate complexes is supported by quantum chemical theoretical calculations. Aluminate and zincate, when present together, compete roughly equally for a deficiency of silicate to form [(HO)(3)ZnOSiO(2)OH](4-) and [(HO)(3)AlOSiO(2)OH](3-) which exchange (29)Si at a fast but measurable rate. 相似文献
996.
Reaction of dioxoruthenium(VI) porphyrins [Ru(VI)(Por)O2] with arylimine HN=CPh2 in dichloromethane afforded bis(methyleneamido)ruthenium(IV) porphyrins [Ru(IV)(Por)(N=CPh2)2] for Por = 4-Cl-TPP and TMP; (methyleneamido)hydroxoruthenium(IV) porphyrins [Ru(IV)(Por)(N=CPh2)(OH)] for Por = TPP and TTP; and bis(arylimine)ruthenium(II) porphyrins [Ru(II)(Por)(HN=CPh2)2] for Por = 3,5-Cl2TPP and 3,5-(CF3)2TPP. In dichloromethane solution exposed to air, complex [Ru(II)(3,5-Cl2TPP)(HN=CPh2)2] underwent oxidative deprotonation to form [Ru(IV)(3,5-Cl2TPP)(N=CPh2)2]. The new ruthenium porphyrins were identified by 1H NMR, UV-vis, IR, and mass spectroscopy, along with elemental analysis. X-ray crystal structure determinations of [Ru(IV)(4-Cl-TPP)(N=CPh2)2], [Ru(IV)(TPP)(N=CPh2)(OH)], and [Ru(II)(3,5-(CF3)2TPP)(HN=CPh2)2] revealed the Ru-N(methyleneamido) or Ru-N(arylimine) distances of 1.897(5) A (average), 1.808(4) A, and 2.044(2) A (average), respectively. 相似文献
997.
D. Y. Kwok A. Leung A. Li C. N. C. Lam R. Wu A. W. Neumann 《Colloid and polymer science》1998,276(6):459-469
Low-rate dynamic contact angles of 22 liquids on a poly(n-butyl methacrylate) (PnBMA) polymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 16 liquids yielded
non-constant contact angles, and/or dissolved the polymer on contact. From the experimental contact angles of the remaining
6 liquids, it is found that the liquid–vapor surface tension times cosine of the contact angle changes smoothly with the liquid–vapor
surface tension, i.e. γlv cos θ depends only on γlv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert
and non-inert (polar and non-polar) surfaces [34–37, 45–47]. The solid–vapor surface tension calculated from the equation-of-state
approach for solid-liquid interfacial tensions [14] is found to be 28.8 mJ/m2, with a 95% confidence limit of ±0.5 mJ/m2, from the experimental contact angles of the 6 liquids.
Received: 12 September 1997 Accepted: 22 January 1998 相似文献
998.
Chung-Yee Leung 《Applied physics. B, Lasers and optics》1982,27(4):201-205
The transmission of ultrashort pulses from a mode-locked Nd: glass laser in germanium of various thicknesses (3 to 8 m) has been measured as a function of incident irradiance. Transmission is seen to increase with irradiance level in all samples. The degree of enhancement is greater for the thcker samples. At high excitation levels, thinner samples show a peaking of transmission, which does not occur in a thick sample. Taking the sample as composed of thin elements, the parameters characterizing the photoexcited electron-hole plasma have been found by assuming homogeneous excitation within each element. Theoretical curves thus obtained give good quantitative account of the experimental results. Peaking of transmission is seen to due to a balance between absorption enhancement in the front portion of the sample and absorption reduction in the back. 相似文献
999.
Chun-Yip Leung Thomas C. W. Mak Henry N. C. Wong 《Journal of chemical crystallography》1996,26(3):227-230
A benzo-phenanthro-fused planar cyclooctatetraene derivative, namely, 5,6,15,16-tetradehydrobenzo[a]phenanthro[9, 10-e]cyclooctene (5) was synthesized in two steps from the known benzo[a]phenanthro[9, 10-e]cyclooctene (6). Compound5 crystallizes in space groupPbam witha=9.828(2),b=19.466(4),c=15.901(3) Å, and Z=8. X-Ray analysis (MoK radiation,R=0.060 for 1233 observed data) has shown that both independent molecules have the same planarC
2v
configuration with averaged bond lengths of 1.381(7) and 1.208(7) Å for the phenanthrene C6a–C14b bond and the acetylenic CC bond, respectively.1H and13C NMR spectral results of 5 and 5,6,15,16-tetrabromo-5,6,15,16-tetrahydrobenzo[a]phenanthro[9, 10-e]cyclooctene (7) are also presented. 相似文献
1000.
Sakumoto WK de Barbaro P Bodek A Budd HS Kim BJ Merritt FS Oreglia MJ Schellman H Schumm BA Bachmann KT Blair RE Foudas C King BJ Lefmann WC Leung WC Mishra SR Oltman E Quintas PZ Rabinowitz SA Sciulli F Seligman WG Shaevitz MH Bernstein RH Borcherding FO Fisk HE Lamm MJ Marsh W Merritt KW Rapidis PA Yovanovitch D Sandler PH Smith WH 《Physical review D: Particles and fields》1992,45(9):3042-3050