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101.
Samori S Tojo S Fujitsuka M Yang SW Ho TI Yang JS Majima T 《The journal of physical chemistry. B》2006,110(26):13296-13303
Emission from several 1-(arylethynyl)pyrenes with a substituent on the aryl group (REPy, R = phenyl (PEPy), 4-dimethylaminophenyl (NPEPy), 4-isopropoxyphenyl (OPEPy), 2-quinonyl (QEPy), and 9-(10-cyanoanthracenyl) (AEPy)) was studied with time-resolved fluorescence measurements during pulse radiolysis in benzene. NPEPy and AEPy showed only monomer emission, while PEPy, OPEPy, and QEPy showed both monomer and excimer emissions during pulse radiolysis. In addition, REPy's also showed long-lived emissions with very weak intensities in the absence of oxygen, which were assigned to the "P-type" delayed fluorescence derived from the triplet-triplet annihilation. The formation of REPy's in the singlet excited state (1REPy*) can be interpreted as the charge recombination between the REPy radical cation and anion (REPy*+ and REPy*-, respectively), which are initially generated from the radiolytic reaction in benzene. Both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of PEPy are localized on the 1-pyrenyl (Py) moiety, while the HOMO of REPy's with an electron donating or withdrawing substituent on the benzene ring (R(D)EPy such as NPEPy and OPEPy or R(A)EPy such as QEPy and AEPy) is mainly localized on the donor moieties (R(D) or Py) and the LUMO on the acceptor ones (Py or R(A), respectively). Therefore, it is suggested that the one-electron oxidation and reduction of REPy's can occur from the donor and acceptor moieties, respectively. This scheme reasonably explains the relationship between the annihilation enthalpy changes (-Delta H' degrees) for the charge recombination of REPy*+ and REPy*- and the singlet excitation energies (E'(S1) of the REPy's. The results are compared with those in electrogenerated chemiluminescence. 相似文献
102.
Tachikawa T Takai Y Tojo S Fujitsuka M Irie H Hashimoto K Majima T 《The journal of physical chemistry. B》2006,110(26):13158-13165
The photocatalytic degradation processes of ethylene glycol (EG) during the UV or visible light irradiation of pure anatase and nitrogen (N)-doped TiO2 powders (TiO(2-x)N(x), x = 0, 0.002, 0.003, and 0.007) were investigated using time-resolved diffuse reflectance (TDR) and solid-state NMR spectroscopies. The TDR spectra and time traces observed for the charge carriers indicated that the scavenging of photogenerated holes (h+) by EG occurred during the 355-nm laser photolysis of the N-doped TiO2 powders, while no direct oxidation reaction of EG by h+ occurred during the 460-nm laser photolysis, although the charge carriers were sufficiently generated upon excitation. The solid-state magic-angle spinning (MAS) NMR measurements revealed that EG is preferentially chemisorbed on the surface of the N-doped TiO2 powders, in contrast to the pure TiO2, and degrades under visible light irradiation. 相似文献
103.
Tokiyoshi Matsuda Mamoru Furuta Takahiro Hiramatsu Hiroshi Furuta Chaoyang Li Takashi Hirao 《Applied Surface Science》2010,256(21):6350-2485
Thermal stability of sputter deposited ZnO thin films was evaluated by thermal desorption spectroscopy (TDS). Desorption of Zn was mainly observed from the films deposited at low O2/Ar gas ratio and low RF power. In contrast, O2 desorption was mainly observed from the films deposited at high O2/Ar gas ratio and high RF power. The amount of desorbed O2 from the film increased with increasing the O2/Ar gas flow ratio and the RF power. Furthermore, the desorption temperature of O2 increased with increasing the RF power during the deposition. Thermal stability of the ZnO films was controlled not only by the O2/Ar gas flow ratio, but also applied RF power to the target. 相似文献
104.
Tachikawa T Tojo S Fujitsuka M Sekino T Majima T 《The journal of physical chemistry. B》2006,110(29):14055-14059
The photocatalytic one-electron oxidation reaction of an aromatic compound during UV light irradiation of titania nanotubes and nanoparticles was investigated using time-resolved diffuse reflectance spectroscopy. Remarkably long-lived radical cations of the aromatic compound and trapped electrons were observed for the nanotubes when compared to those for nanoparticles. The influences of the morphology on the one-electron oxidation process of an aromatic compound adsorbed on the surface were discussed in terms of the charge recombination dynamics between the radical cation and electrons in TiO2. 相似文献
105.
Nanoporous metals can be fabricated by dealloying, which is one of the reactions that occur during the corrosion of alloys. Nanoporous gold has been widely investigated for several decades, and it has recently been found that other metals, such as platinum, palladium, nickel, and copper, can form nanoporous structures through the dealloying of binary alloys. This article mainly shows fabrication and properties of nanoporous palladium and nickel after introduction of nanoporous metals by referring to nanoporous gold as an example. It is necessary to select binary alloys with suitable elements, in which the dissolution of the less noble element and the aggregation of the nobler element at the solid/electrolyte interface are simultaneously allowed. Postprocessing by thermal or acid treatment alters the nanoporous structure. Various properties of nanoporous metals (including mechanical, catalytic, piezoelectric, hydrogenation, and magnetic ones) are different from those of bulk and nanocrystalline materials and nanoparticles because of their specific three-dimensional network structures consisting of nanosized pores and ligaments. Hydrogenation and magnetic properties are reviewed in terms of lattice strain at curved surfaces. These new metallic nanomaterials are now being investigated from the viewpoint of functional applications, and provide much room for study in various fields. 相似文献
106.
Nanoporous Ni specimens with ligament lengths of 10–210 nm and specific surface areas of 0.03–0.58 nm?1 were fabricated by the dealloying of Ni0.25Mn0.75 alloy and annealing at 473–873 K, and saturation magnetization investigated in terms of their size dependence. Saturation magnetization decreased with decreasing ligament length or increasing specific surface area. This trend is the same as that for nanoparticle Ni. However, the saturation magnetization of nanoporous Ni tends to be lower than that of the nanoparticle Ni when their specific surface areas are the same. It is suggested, therefore, that the surface effect due to a noncollinear arrangement is enhanced by the surface defects in the nanoporous Ni. 相似文献
107.
The change in intensity and frequency of O-H stretching band upon intramolecular hydrogen bonding was sufficiently examined for various proton acceptors of many alicyclic substances. The order of proton acceptors to bring about the intensity increase of constant degree is: Some discussions are given on these. 相似文献
108.
Kosuke Yasui Miharu Kamitani Mamoru Tobisu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14295-14299
Concerted nucleophilic aromatic substitution (CSNAr) has emerged as a powerful mechanistic manifold, in which nucleophilic aromatic substitution can proceed in one step without the need to form a Meisenheimer intermediate. However, all of the CSNAr reactions reported thus far require a stoichiometric strong base or activating reagent, and no catalytic variants have yet been reported. Herein, we report an N‐heterocyclic carbene (NHC)‐catalyzed intramolecular cyclization of acrylamides that contain a 2‐fluorophenyl group on the nitrogen through a CSNAr reaction. By using this catalytic method, it is possible to synthesize an array of quinolin‐2‐one derivatives, which are common structural motifs in pharmaceuticals and organic materials. DFT calculations unambiguously revealed that this reaction proceeds through the concerted nucleophilic aromatic substitution of aryl fluorides, in which a stereoelectronic σ (Cipso‐Cβ)→ σ*(Cipso‐F) interaction critically contributes to the stabilization of the transition state for the cyclization. 相似文献
109.
110.
Mamoru Furuta Takahiro Hiramatsu Tokiyoshi Matsuda Chaoyang Li Hiroshi Furuta Takashi Hirao 《Journal of Non》2008,354(17):1926-1931
Zinc oxide (ZnO) film was deposited on a glass substrate by rf magnetron sputtering with O2/Ar as working gases. Structural properties of the films were characterized by XRD. Average crystallite size in the films was strongly dependent on both the gas flow ratio of O2/Ar and rf-power at a constant deposition pressure. During the deposition, energetic species in the plasma were in situ monitored using optical emission spectroscopy. An inverse correlation was observed between the average crystallite size and the emission intensity ratio of IO∗/IAr. Bombardment of atomic oxygen to the growing surface played an important role in determining the average crystallite size in the films. The average crystallite size could be controlled by the emission intensity ratio of IO∗/IAr. 相似文献