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51.
52.
New mono- and bis[4-(3-hydroxy-2-methyl-4-quinolinoyloxy)-2,2,6,6-tetramethylpiperidin-1-oxyl](meso-tetraphenylporphyrinato)yttrium(III) complexes have been synthesized, and the properties of the excited states generated by photoexcitation of porphyrin were studied by time-resolved (TR) and pulsed two-dimensional electron paramagnetic resonance (EPR) spectroscopy. A TR-EPR spectrum was observed in the quartet (S=3/2) or quintet (S=2) states generated from interactions of one or two radicals with the photoexcited triplet state of the porphyrin. The zero-field splitting D values of these states were analyzed in terms of those of the triplet and the radical-triplet pair. The spin states of the excited states were definitely assigned by measuring the mutation frequencies with pulsed EPR. 相似文献
53.
54.
Hidefumi Yoshii Aya Sakane Daisuke Kawamura Tze Loon Neoh Hayato Kajiwara Takeshi Furuta 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):591-596
The release kinetics of (−)-menthol from chewing gum was investigated using various encapsulated powder of (−)-menthol. The
apparatus of flavor release of chewing gum was made with a glass container of mashing homogenizer. Flavor release behavior
could be correlated with Avrami’s equation. Chewing gum containing (−)-menthol/γ-CD complex powder had longer retention of
(−)-menthol compared with the β-CD complex powder and the (−)-menthol encapsulated in modified starches. The activation energies
of (−)-menthol release from chewing gum were 106 kJ/mol for γ-CD complex and 74 kJ/mol for (−)-menthol/β-CD complex powder
and emulsified (−)-menthol encapsulated in HI-CAP, respectively. 相似文献
55.
56.
Chotika Viriyarattanasak Motoo Shiro Shigeru Munekawa Felix Franks Satomi Ikeda Kazuhito Kajiwara 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):954-958
Raffinose [or O‐α‐D‐galactopyranosyl‐(1→6)‐α‐D‐glucopyranosyl‐(1→2)‐β‐D‐fructofuranoside] pentahydrate, C18H32O16·5H2O, (I), and three lower hydrates, namely the 4.433‐, (II), 4.289‐, (III), and 4.127‐hydrated, (IV), forms, obtained in the course of the dehydration of (I), have been studied. The unit cells in the space group P212121 are of similar dimensions for all the crystals. The conformation of the raffinose molecules remains almost the same across the four crystal structures. The raffinose molecules are linked into a three‐dimensional hydrogen‐bonded network involving all the –OH groups, the ring and glycosidic O atoms, and the water molecules. Six water sites were identified in the structures of (II), (III) and (IV), of which W1, W4 and W6 (W = water) are partially occupied with their populations coupled. W1, W4 and one of the –OH groups of the galactose ring form an infinite hydrogen‐bonding chain around a 21 axis parallel to the a axis (denoted chain A), and W6 and the same –OH group form a similar chain (chain A′) disordered with chain A. The occupancy ratio of chain A to chain A′ for N‐hydrates (N is a hydration number between 4 and 5) is (N− 4):(5 −N). The transformation of chain A to chain A′ as part of the dehydration process has little effect on the rest of the structure. Thus, the dehydration proceeds without significant impact on the crystal structure. 相似文献
57.
Sachi Morinaga Takashi Nishiyama Takashi Kajiwara Kunihito Nagayama 《Applied Physics A: Materials Science & Processing》2010,101(4):743-746
A compositionally graded thin film of FeSi2 was fabricated by a gravity-assisted pulsed laser ablation (GAPLA) system. By this method, a compositionally graded structure
was successfully produced under a gravity field of 5400 G. We demonstrate that the atomic fraction of Fe, the heavier component
of the thin film measured by scanning electron microscope/energy dispersive X-ray (SEM-EDX), showed increasing spatial distribution
with the direction of gravity. We found that optimal laser fluence exists to give a thin film having the largest possible
spatial compositional gradient. We found that surface energy density on the substrate surface is the key parameter to control
the composition distribution. Furthermore, the ratio of Fe/Si of the film did not match that of the target. This result shows
that the Si component is selectively etched during the film-forming process. Relatively high laser fluence as well as a very
narrow space between the target and the substrate are essential to etch the film once it is deposited, in order to re-ionize
and etch Si selectively while gravity accelerates both Fe and Si particles to the direction of gravity. We hypothesize that
this process accounts for both the change in the stoichiometry and the formation of composition distribution. 相似文献
58.
Yuji Utsunomiya Takashi Kajiwara Takashi Nishiyama Kunihito Nagayama Shiro Kubota Motonao Nakahara 《Applied Physics A: Materials Science & Processing》2010,101(1):137-141
The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally
investigated. A supersonic liquid jet is observed at the liquid–air interface. The liquid surface layer is driven by a plasma
plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG
laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed
constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at
an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid
jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser
ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source
and high-resolution film are required to observe the detailed structure of a liquid jet. 相似文献
59.
Takashi Kajiwara Takashi Nishiyama Sachi Morinaga Kunihito Nagayama 《Applied Physics A: Materials Science & Processing》2010,101(4):739-742
We carried out the thin film deposition of iron silicide by pulsed laser ablation (PLA) on a sapphire substrate, which was
placed on a high-speed rotating titanium disk. The deposited thin film exhibited a continuous composition gradient. We investigated
how the continuous composition gradient was attained, because the strength of the gravity field in our experiment was far
below that in the experiment on bulk crystalline compounds. In the present study, we obtain the spatial distribution of several
species in the PLA plume of FeSi2 by using an intensified charge-coupled device (ICCD) camera. 相似文献
60.
Kajiwara Y Santander PJ Roessner CA Pérez LM Scott AI 《Journal of the American Chemical Society》2006,128(30):9971-9978
Two new cobalt corrinoid intermediates, cobalt-precorrin 5A and cobalt-precorrin 5B, have been synthesized with the aid of overexpressed enzymes of the vitamin B(12) pathway of Salmonella entericaserovar typhimurium. These compounds were made in several regioselectively (13)C-labeled forms, and their structures have been established by multidimensional NMR spectroscopy. The addition of CbiF to the enzymes known to synthesize cobalt-precorrin 4 resulted in the formation of cobalt-precorrin 5A, and the inclusion of CbiG with CbiF produced cobalt-precorrin 5B, which has allowed us to define the role of these enzymes in the anaerobic biosynthetic pathway. CbiF is the C-11 methylase, and CbiG, an enzyme which shows homology with CobE of the aerobic pathway, is the gene product responsible for the opening of the ring A delta-lactone and extrusion of the "C(2)" unit. The discovery of these long-sought intermediates paves the way for defining the final stages of the anaerobic pathway. It is of considerable evolutionary interest that nature uses two distinct pathways to vitamin B(12), both conserved over several billion years and featuring completely different mechanisms for ring-contraction of the porphyrinoid to the corrinoid ring system. Thus the aerobic pathway utilizes molecular oxygen to trigger the events at C-20 leading to contraction and expulsion of the "C(2)" unit as acetic acid from a metal-free intermediate, whereas the anaerobic route features internal delivery of oxygen from a carboxylic acid terminus to C-20 followed by extrusion of the "C(2)" unit as acetaldehyde, using cobalt complexes as substrates. 相似文献