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151.
152.
Chen W Zhang HL Xu H Tok ES Loh KP Wee AT 《The journal of physical chemistry. B》2006,110(43):21873-21881
A SiC nanomesh is used as a nanotemplate to direct the epitaxy of C60 molecules. The epitaxial growth of C60 molecules on SiC nanomesh at room temperature is investigated by in situ scanning tunneling microscopy, revealing a typical Stranski-Krastanov mode (i.e., for the first one or two monolayers, it is a layer-by-layer growth or 2-D nucleation mode; at higher thicknesses, it changes to island growth or a 3-D nucleation mode). At submonolayer (0.04 and 0.2 ML) coverage, C60 molecules tend to aggregate to form single-layer C60 islands that mainly decorate terrace edges, leaving the uncovered SiC nanomesh almost free of C60 molecules. At 1 ML C60 coverage, a complete wetting layer of hexagonally close-packed C60 molecules forms on top of the SiC nanomesh. At higher coverage from 4.5 ML onward, the C60 stacking adopts a (111) oriented face-centered-cubic (fcc) structure. Strong bright and dim molecular contrasts have been observed on the first layer of C60 molecules, which are proposed to originate from electronic effects in a single-layer C60 island or the different coupling of C60 molecules to SiC nanomesh. These STM molecular contrast patterns completely disappear on the second and all the subsequent C60 layers. It is also found that the nanomesh can be fully recovered by annealing the C60/SiC nanomesh sample at 200 degrees C for 20 min. 相似文献
153.
Hepatitis C virus (HCV) is a pathogen that is of great medical significance in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Although the HCV proteins have been intensively investigated over the past decade, the biochemical functions of the NS4B protein are still largely unknown. To investigate NS4B as a potential causative agent of liver disease, transgenic mice expressing the NS4B protein in liver tissue were produced. The transgenic animals were phenotypically similar to their normal littermates for up to 18 months of age. Our results suggest that the HCV NS4B protein is not directly cytopathic or oncogenic in our transgenic mice model. 相似文献
154.
155.
Jeon SM Jung SJ Kim HD Lim do K Lee H Kim S 《The journal of physical chemistry. B》2006,110(43):21728-21734
We have studied the adsorption and decomposition of thiophene (C4H4S) on Ge(100) using scanning tunneling microscopy (STM), high-resolution core-level photoemission spectroscopy (HRPES), and density functional theory (DFT) calculation. Analysis of S 2p core-level spectra reveals three adsorption geometries, which we assign to a Ge-S dative bonding state, a [4 + 2] cycloaddition bonding state, and a decomposed bonding state (desulfurization reaction product). Furthermore, we found that the number ratio of the three adsorption geometries depended on the molecular coverage and the annealing temperature. At low coverages, the kinetically favorable dative bonding state is initially formed at room temperature. As the molecular coverage increases, thermodynamically stable [4 + 2] cycloaddition reaction products are additionally produced. In addition, we found that as the surface temperature increased, the [4 + 2] cycloaddition reaction product either possibly desorbed as molecular thiophene or decomposed to form a metallocycle-like species (C4H4Ge2) and a sulfide (Ge2S). We systematically elucidate the changes in the bonding states of adsorbed thiophene on Ge(100) according to the thiophene coverage and annealing temperature. 相似文献
156.
In this paper, properties of certain real-valued mappings Δ on binary systems X which satisfy versions of the triangle inequality are investigated. For example, via a quotient construction using Ker Δ
= {x: Δ(x) = 0} it is shown that X/Ker Δ is a d-algebra if X is a d-algebra. In addition fuzzy versions of these triangular norms and their properties are considered as well. Finally boundedness
conditions on Δ and a concept of magnitude are both introduced and some consequences are derived. 相似文献
157.
158.
Polar oxide substrates for graphene growth: A first-principles investigation of graphene on MgO(111)
Kyung-Ah Min Jinwoo Park Junga Ryou Suklyun Hong Aloysius Soon 《Current Applied Physics》2013,13(5):803-807
Given the recent excitement over the truly two-dimensional carbon “super” material – graphene, there is now much effort and focus on the various possibilities of engineering the band gap of graphene for its device applications. One possible and promising route will be to grow graphene directly on some non-metallic substrates. In this paper, we address the atomic and electronic structure of various graphene structures on the polar MgO(111) using first-principles density-functional theory (DFT) calculations. We find that graphene generally interacts strongly with the O-terminated polar oxide surface, forming strong chemical bonds, inferred from both energetics and detailed density-of-states analysis. We compare our theoretical findings with available experimental results, offering a possible direction for future band gap engineering of graphene on such oxide substrates. 相似文献
159.
Oleg L. Tok Kamil Lang Ale Ri
ka Josef Cva
ka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1668-1672
Despite the apparent diversity of the protocols developed for the synthesis of helicenes, they essentially follow the same strategy: the closure of one, or several, internal rings in a key step. Herein, we report the synthesis of a new family of the heterohelicenes consisting of fused silacyclopentadiene rings formed via a facile and novel process. The treatment of oligo(alkynilydenesilylene) precursors of type H2C=CH?(SiMe2?C≡C)n?R (n=3–7), bearing a vinyl group on the terminal silicon atom, with 9‐borabicyclononane leads first to 1,2‐hydroboration of the terminal double bond which then continues with a cascade of intramolecular 1,1‐carboboration reactions accompanied with the closure of a new silole ring after each step affording the target silahelicenes with, currently, up to seven condensed silole rings and with excellent yields. According XRD analysis, the seven fused silole rings of the heptacyclic compound 11 b form an almost complete turn of a helix. The presented one‐pot sequence of reactions is the first example of ring‐by‐ring knitting of a helical framework starting from easily available linear precursors. 相似文献
160.
Kehr SC Cebula M Mieth O Härtling T Seidel J Grafström S Eng LM Winnerl S Stehr D Helm M 《Physical review letters》2008,100(25):256403
We demonstrate the imaging of ferroelectric domains in BaTiO3, using an infrared-emitting free-electron laser as a tunable optical source for scattering scanning near-field optical microscopy and spectroscopy. When the laser is tuned into the spectral vicinity of a phonon resonance, ferroelectric domains can be resolved due to the anisotropy of the dielectric properties of the material. Slight detuning of the wavelength gives rise to a contrast reversal clearly evidencing the resonant character of the excitation. The near-field domain contrast shows that the orientation of the dielectric tensor with respect to the sample surface has a clear influence on the near-field signal. 相似文献