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91.
Synchronization phenomena in coupled circadian oscillators of plant leaves were investigated experimentally using bioluminescence technology for a clock gene. Analyzing the phase of circadian oscillation, the phase-wave propagations and the phase delay caused by the vein network were observed. We describe these phase dynamics using a two-layer model with coupled Stuart-Landau equations. Global synchronization of circadian oscillators in the leaf is also investigated. 相似文献
92.
Total Synthesis,Stereochemical Reassignment,and Biological Evaluation of (−)‐Lyngbyaloside B
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Prof. Dr. Haruhiko Fuwa Yuta Okuaki Naoya Yamagata Prof. Dr. Makoto Sasaki 《Angewandte Chemie (International ed. in English)》2015,54(3):868-873
(?)‐Lyngbyaloside B is a 14‐membered macrolide glycoside isolated from the marine cyanobacterium Lyngbya sp. as a cytotoxic substance by Moore and co‐workers. The first total synthesis of (?)‐lyngbyaloside B and the reassignment of its stereostructure is described. The synthesis features an Abiko–Masamune aldol reaction, a vinylogous Mukaiyama aldol reaction, and a macrocyclization involving an acyl ketene intermediate for the construction of the macrocyclic backbone, which contains an acylated tertiary alcohol. The antiproliferative activity of selected compounds against a small panel of human cancer cell lines is also reported. 相似文献
93.
Ishiuchi S Asakawa T Mitsuda H Miyazaki M Chakraborty S Fujii M 《The journal of physical chemistry. A》2011,115(37):10363-10369
In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet-ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole-dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole-dipole interaction stabilizes specific conformers which are actually observed. 相似文献
94.
Total synthesis of (-)-brevenal: a streamlined strategy for practical synthesis of polycyclic ethers
We describe a streamlined strategy for the practical synthesis of trans-fused polycyclic ethers and its application to a concise total synthesis of (-)-brevenal, a new pentacyclic polyether natural product with intriguing biological activities. The B-, D-, and E-rings were constructed by TEMPO/PhI(OAc)(2)-mediated oxidative lactonization of the corresponding 1,6-diols, with minimal need for manipulation of oxygen functionalities. The B- and E-ring lactones were appropriately functionalized by Suzuki-Miyaura coupling of lactone-derived enol phosphates and subsequent stereoselective hydroboration. The A-ring was formed by our mixed thioacetalization methodology. The AB- and DE-ring fragments were assembled through Suzuki-Miyaura coupling, and the C-ring was forged in the same manner as that for the A-ring. More than two grams of the pentacyclic polyether core of (-)-brevenal have been synthesized by the synthetic route developed in this study. 相似文献
95.
Intramolecular oxa-conjugate cyclization (IOCC) of α,β-unsaturated carbonyl compounds, triggered by deprotonation with a base, represents a straightforward method for the synthesis of tetrahydropyrans. However, it has been known that stereochemical outcome of IOCC depends on the local structure of substrates and sometimes requires harsh reaction conditions and/or prolonged reaction times for selective formation of 2,6-cis-substituted tetrahydropyrans. These shortcomings limit the feasibility of IOCC in the context of complex natural product synthesis. In this paper, we describe Br?nsted acid-catalyzed IOCC of α,β-unsaturated ester surrogates (e.g., α,β-unsaturated thioesters, oxazolidinone imides, and pyrrole amides) under mild reaction conditions, which affords a series of synthetically versatile 2,6-cis-substituted tetrahydropyran derivatives with good to excellent stereoselectivity (dr from 7:1 to >20:1). These α,β-unsaturated carbonyl compounds were found to be more reactive than the corresponding oxoesters that are generally unreactive toward Br?nsted acid-catalyzed intramolecular oxa-conjugate additions. The product tetrahydropyrans could be transformed into various derivatives in an efficient manner, highlighting the usefulness of our methodology. 相似文献
96.
Haruhiko Ito Katsuaki Koshimura Saori Onitsuka Kohtaro Okada Tsuneo Suzuki Hiroki Akasaka Hidetoshi Saitoh 《Plasma Chemistry and Plasma Processing》2012,32(2):231-248
The dissociative excitation reaction of C2H2 with the electron-cyclotron resonance plasma of Ar was investigated based on the electrostatic-probe measurements and on
the optical emission spectroscopy of the CH(A2Δ–X2Π) transition. The density, n
e, and the temperature, T
e, of free electrons were controlled by adding H2O molecules externally into the reaction region, and the dependence of the CH(A2Δ–X2Π) emission intensity on the addition of H2O was observed to compare with the evaluated dependencies based on n
e and T
e. The mechanism of production of CH(A2Δ) was found, predominantly, to be the electron impact with the contribution of 10–20% of the electron-impact dissociation
of C2H radicals; the contribution of the ion–electron recombination was negligible. Hydrogenated amorphous carbon films were fabricated
using the same reaction system. The atomic compositions, Raman spectra, and the hardness of films were discussed in terms
of the variations of n
e and T
e upon the addition of H2O molecules. 相似文献
97.
Yoshiki K. Tanaka Stefan Friedrich Hiroyuki Fujioka Hans Geissel Ryugo S. Hayano Satoru Hirenzaki Kenta Itahashi Satoshi Itoh Daisuke Jido Volker Metag Hideko Nagahiro Mariana Nanova Takahiro Nishi Kota Okochi Haruhiko Outa Ken Suzuki Takatoshi Suzuki Helmut Weick 《Few-Body Systems》2013,54(7-10):1263-1266
We are going to perform an inclusive spectroscopy experiment of η′ mesic nuclei with the 12C(p,d) reaction to study in-medium properties of the η′ meson. In nuclear medium, the η′ meson mass may be reduced due to partial restoration of chiral symmetry. In case of sufficiently large mass reduction and small absorption width of η′ at normal nuclear density, peak structures of η′ mesic states in 11C will be observed near the η′ emission threshold even in an inclusive spectrum. The experiment will be carried out at GSI with proton beam supplied by SIS using FRS as a spectrometer. The detail of the experiment is described. 相似文献
98.
Abstract There has been much progress in the vibrational spectroscopic study of short-lived chemical species and electronic excited states in the last decade [1, 2]. Most of those studies employed Raman scattering method by recourse to the resonance enhancement associated with the transient electronic absorption. TR3 is now widely known aB standing for “Time-Resolved Resonance Raman” spectroscopy. 相似文献
99.
Haruhiko Ogasawara 《Computational Statistics》2013,28(6):2559-2583
Asymptotic cumulants of the Bayes modal estimators of item parameters using marginal likelihood in item response theory are derived up to the fourth order with added higher-order asymptotic variances under possible model misspecification. Among them, only the first asymptotic cumulant and the higher-order asymptotic variance for an estimator are different from those by maximum likelihood. Corresponding results for studentized Bayes estimators and asymptotically bias-corrected ones are also obtained. It was found that all the asymptotic cumulants of the bias-corrected Bayes estimator up to the fourth order and the higher-order asymptotic variance are identical to those by maximum likelihood with bias correction. Numerical illustrations are given with simulations in the case when the 2-parameter logistic model holds. In the numerical illustrations, the maximum likelihood and Bayes estimators are used, where the same independent log-normal priors are employed for discriminant parameters and the hierarchical model is adopted for the prior of difficulty parameters. 相似文献
100.
H Fuwa K Ishigai K Hashizume M Sasaki 《Journal of the American Chemical Society》2012,134(29):11984-11987
Total synthesis of gambieric acid A, a potent antifungal polycyclic ether metabolite, has been accomplished for the first time, which firmly established the complete stereostructure of this natural product. 相似文献