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排序方式: 共有278条查询结果,搜索用时 250 毫秒
181.
We study heterotic asymmetric orbifold models. By utilizing the lattice engineering technique, we classify (22,6)-dimensional Narain lattices with right-moving non-Abelian group factors which can be starting points for Z3 asymmetric orbifold construction. We also calculate gauge symmetry breaking patterns. 相似文献
182.
Griffith MJ Sunahara K Wagner P Wagner K Wallace GG Officer DL Furube A Katoh R Mori S Mozer AJ 《Chemical communications (Cambridge, England)》2012,48(35):4145-4162
Porphyrin molecules offer immense potential as the light harvesting component of dye-sensitised nanocrystalline TiO(2) solar cells. Synthetic porphyrin dyes were amongst the first dyes trialled for sensitisation of inorganic semiconducting oxides. Today, they exhibit the best performance reported for dye-sensitised solar cells. Accompanying the significant performance improvement over the last two decades is a much improved understanding of efficiency-determining fundamental electron transfer steps, from charge photogeneration to recombination. In this feature article we highlight our recent discoveries of the influence of porphyrin molecule structure on efficiency determining electron transfer kinetics and device performance by systematically changing the molecular structure and observing electron injection and recombination kinetics using time-resolved optical and electrical probes. Despite our observation of ultrafast charge injection for all porphyrin dyes studied by transient absorption spectroscopy, the injection yield estimated using an internal standard remains below 100% and depends strongly on the molecular structure. The observed discrepancy between kinetic competition and the injection yield is attributed to non-injecting dyes, probably arising due to inhomogeneity. A very interesting sub-ns (0.5 ns to 100 ns) charge recombination channel between photo-injected electrons and porphyrin cations is observed, which is found to be more prominent in free-base porphyrin dyes with a conjugated linker. Charge recombination between the acceptor species in the redox containing electrolyte and injected electrons is shown to be an important limitation of most porphyrin-sensitised solar cells, accelerated by the presence of porphyrin molecules at the TiO(2)-electrolyte interface. This recombination reaction is strongly dependent on the porphyrin molecular structure. Bulky substituents, using a porphyrin dimer instead of a porphyrin monomer, a light soaking treatment of freshly prepared films and co-sensitization of TiO(2) with multiple dyes are shown to be successful strategies to improve electron lifetime. Finally, new developments unique to porphyrin dye-sensitised solar cells, including performance enhancements from a light exposure treatment of a zinc porphyrin dye, a significant performance improvement observed after co-sensitisation of TiO(2) with free-base and zinc porphyrin dyes and the use of porphyrin dimers with increased light harvesting in thin-film TiO(2) solar cells are described. 相似文献
183.
The mechanisms of [2?+?2?+?2] reactions of three ethynes and monosilaethylenes to form benzene and 1,3,5-trisilacyclohexane were studied by ab initio MO methods. The reaction mechanisms were analyzed by configuration interaction/localized molecular orbital/CASSCF calculations. Although the [2?+?2?+?2] reaction of ethyne is typically ??homologous?? concerted, that of monosilaethylene is polarized (ionic-cyclic) one-step reaction. In addition, the aromaticity along the intrinsic reaction coordinate pathway was studied using the index of deviation from aromaticity. Although the transition state of trimerization of ethyne does not have an aromatic nature for the ??- and ??-bonds formation system, the crossing point of the ??-bond formation and ??-bond breaking shows an aromatic nature. 相似文献
184.
Viscoelastic properties of poly(methyl methacrylate) with high glass transition temperature by lithium salt addition
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Azusa Miyagawa Viknasvarri Ayerdurai Shogo Nobukawa Masayuki Yamaguchi 《Journal of Polymer Science.Polymer Physics》2016,54(22):2388-2394
The effect of ion‐dipole interaction between lithium cations and oxygen atoms in poly(methyl methacrylate) (PMMA), which leads to the great enhancement of glass transition temperature (Tg), on the linear viscoelastic properties is studied using binary blends of PMMA and lithium trifluoromethanesulfonate (LiCF3SO3). The strong interaction at low temperature leads to the high modulus in the glassy region even near Tg. The interaction becomes weak as increasing the temperature. Consequently, the rheological terminal region is clearly detected without a marked enhancement of steady‐state compliance, although the zero‐shear viscosity increases by the LiCF3SO3 addition. The result indicates that the crosslinking due to the ion‐dipole interaction has a lifetime that decides the longest relaxation time. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2388–2394 相似文献
185.
186.
Shogo Sakai 《Journal of Physical Organic Chemistry》2014,27(7):555-564
Stationary point structures (or stable structures) and the electronic states of polycyclic conjugated hydrocarbons are estimated by an extended combination method between two Kekulé structures (ECMK). The estimation by the ECMK required two postulation conditions. (i) Stationary point structures can be represented with one Kekulé structure or the combination of two Kekulé structures. (ii) Structures including element Kekulé structures of the structures with lower energy are not candidates for structures with higher energy. The structures and electronic states of 13 compounds composed of six‐cyclic and four‐cyclic rings were estimated by the ECMK, and corresponded to their geometries and the local aromaticity obtained by complete active space self‐consistent field molecular orbital and B3LYP methods. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
187.
Hara K Zhao ZG Cui Y Miyauchi M Miyashita M Mori S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(20):12730-12736
Nanoporous-walled tungsten oxide (WO(3)) nanotubes (NTs), which had a more positive conduction band edge level compared to that of TiO(2), were applied to various organic dyes for dye-sensitized solar cells (DSSCs). The dye-sensitized WO(3) NTs displayed photosensitization for the organic dyes whose lowest unoccupied molecular orbital (LUMO) level was relatively positive to the conventional TiO(2) electrode and, thus, not applicable for electron injection to the TiO(2) electrode. Electron transport time and electron lifetime for the WO(3) electrode in the DSSCs were investigated. In comparison to the DSSCs based on TiO(2), SnO(2), and In(2)O(3), the WO(3) DSSCs displayed the longest lifetime. On the other hand, non-diffusion-like electron transport may be an issue to apply WO(3) for the DSSCs. 相似文献
188.
Keiichi Motoyama Yoshimasa Mori Shogo Yamashita Yuya Hayashi Hirofumi Jono Yukio Ando Fumitoshi Hirayama Kaneto Uekama Hidetoshi Arima 《Journal of inclusion phenomena and macrocyclic chemistry》2011,70(3-4):333-338
The purpose of this study is to evaluate in vitro gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 3, G3) conjugates with ??-cyclodextrin (??-CDE (G3)) bearing lactose (Lac-??-CDE) with various degrees of substitution of the lactose moiety (DSL) as a novel hepatocyte-selective carrier. Lac-??-CDE (G3, DSL 1.2) was found to have much higher gene transfer activity than ??-CDE (G3), Lac-??-CDE (G2, DSL 2.6) and Lac-??-CDEs (G3, DSL 2.6, 4.1 and 6.1) in HepG2 cells, which are dependent on the expression of cell-surface asialoglycoprotein receptor (ASGP-R). Lac-??-CDE (G3, DSL 1.2) provided negligible cytotoxicity up to a charge ratio of 100 (carrier/pDNA) in HepG2 cells. These results suggest the potential use of Lac-??-CDE (G3, DSL 1.2) as a non-viral vector for gene delivery toward hepatocytes. 相似文献
189.
Takashi Kakue Mitsuo Kuwamura Yuki Shimozato Tatsuki Tahara Yasuhiro Awatsuji Kenzo Nishio Shogo Ura Toshihiro Kubota Osamu Matoba 《Optical Review》2011,18(1):180-183
We propose an in-line color digital holography that can suppress a 0th-order diffraction image and a conjugate image. This
technique reconstructs the image of an object from two holograms that are formed at two different distances from the object
for each primary color. We numerically simulated the proposed technique and confirmed that it enabled the reconstruction of
higher-quality images of an object than the Fresnel transform alone, which is the simplest reconstruction algorithm in digital
holography. The effectiveness of the proposed technique was also quantitatively shown by evaluating the reconstructed images
using root-mean-square errors. Thus, it was confirmed that the proposed technique was capable of recording and reconstructing
both three-dimensional information and color information of an object. 相似文献
190.
Ooyama Y Nagano T Inoue S Imae I Komaguchi K Ohshita J Harima Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):14837-14843
A new‐type of donor–acceptor π‐conjugated (D‐π‐A) fluorescent dyes NI3 – NI8 with a pyridine ring as electron‐withdrawing‐injecting anchoring group have been developed and their photovoltaic performances in dye‐sensitized solar cells (DSSCs) are investigated. The short‐circuit photocurrent densities and solar energy‐to‐electricity conversion yields of DSSCs based on NI3 – NI8 are greater than those for the conventional D‐π‐A dye sensitizers NI1 and NI2 with a carboxyl group as the electron‐withdrawing anchoring group. The IR spectra of NI3 – NI8 adsorbed on TiO2 indicate the formation of coordinate bonds between the pyridine ring of dyes NI3 – NI8 and the Lewis acid sites (exposed Tin+ cations) of the TiO2 surface. This work demonstrates that the pyridine rings of D‐π‐A dye sensitizers that form a coordinate bond with the Lewis acid site of a TiO2 surface are promising candidates as not only electron‐withdrawing anchoring group but also electron‐injecting group, rather than the carboxyl groups of the conventional D‐π‐A dye sensitizers that form an ester linkage with the Brønsted acid sites of the TiO2 surface. 相似文献