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11.
Kurimoto S Kashiwada Y Morris-Natschke SL Lee KH Takaishi Y 《Chemical & pharmaceutical bulletin》2011,59(10):1303-1306
Three new steroids dyscusins A-C (1-3), including a stigmastane-type sterol and two pregnanes, together with two known steroids were isolated from the leaves of Dysoxylum cumingianum (Meliaceae). Their structures were elucidated on the basis of extensive spectroscopic analyses. In a cytotoxicity assay, compound 1 showed ten-fold enhanced cytotoxicity against multi-drug resistant cancer cells (KB-C2) in the presence of 2.5 μM colchicine as compared with the absence of colchicine. This notable finding indicated that 1 possessed a multi-drug resistant reversal effect. 相似文献
12.
Shin-ichiro Kurimoto Yurika Iinuma Junichi Kobayashi Takaaki Kubota 《Tetrahedron letters》2018,59(51):4496-4499
A new 12-membered macrolide, symbiodinolactone A, was isolated from the culture broth of symbiotic marine dinoflagellate Symbiodinium sp. The gross structure of symbiodinolactone A was elucidated by spectroscopic analyses, and the relative configuration was elucidated by the J-based configuration analysis and density-functional theory calculations. Symbiodinolactone A is the new 12-membered macrolide possessing an E double bond between C-4 and C-5, a branched methyl group at C-7, and a 1,2,3-trihydroxybutyl group at C-11. Symbiodinolactone A is the first usual size macrolide and the first non-nitrogen-containing macrolide from dinoflagellate Symbiodinium sp. Symbiodinolactone A might be generated by the unexplained dinoflagellate polyketide biosynthetic machinery. 相似文献
13.
The trityl group is an important and useful protecting group for primary hydroxy groups on carbohydrates. However, during deprotection, neighboring acetyl groups can easily migrate to the deprotected hydroxy groups. Hence, deprotection of trityl groups was optimized using a microreactor with regard to flow rate, reagent concentration, reaction time, and substrate concentration. The optimized microflow reaction conditions inhibited migration and could be applied to large-scale reactions and other substrates. 相似文献
14.
Motoyoshi Nakano Yudai Ishimur Riki Hott Daiki Hebiguchi Toshiaki Nagat Fuminori Misaizu 《化学物理学报》2019,32(2):193-199
本文通过离子迁移质谱法研究了氧化钠团簇阳离子(NanOm+,n≤11)的稳定结构. 质谱结果表明化学计量组成Na(Na2O)(n-1)/2+ (n=3、5、7、9和11)系列是稳定的,并且NaO(Na2O)(n-1)/2+ (n=5、7、9和11)系列作为二级稳定系列. 为了获得这些团簇离子的结构,通过离子迁移率测量实验测定离子和氦缓冲气体之间的碰撞截面. 同时计算了这些组合物优化结构的理论碰撞截面. 结果表明,Na(Na2O)(n-1)/2+和NaO(Na2O)(n-1)/2+的结构除了n=9之外,其它具有相似结构框架. Na(Na2O)(n-1)/2+所有的化合键位于钠和氧之间. 另一方面,NaO(Na2O)(n-1)/2+中除了Na-O键之外,还存在一个O-O氧键,表明NaO(Na2O)(n-1)/2+具有过氧化物离子(O22-)作为Na(Na2O)(n-1)/2+的氧化物离子(O2-) 的替代物. Na(Na2O)(n-1)/2+和NaO(Na2O)(n-1)/2+两种稳定系列都是闭壳组合物. 这些闭壳特征对氧化钠簇阳离子的稳定性具有强烈影响. 相似文献
15.
Yojiro Ishino Naoki Hayashi Ili Fatimah Bt Abd Razak Takahiro Kato Yudai Kurimoto Yu Saiki 《Flow, Turbulence and Combustion》2016,96(3):819-835
In order to provide a suitable technique for 3D observation of high speed turbulent flames, non-scanning 3D-CT(Computer Tomography) technique using a multi-directional quantitative schlieren system with flash light source, is proposed for instantaneous density distribution of unsteady premixed flames. This “schlieren 3D-CT” is based on (i)simultaneous acquisition of flash-light schlieren images taken from numerous directions, and (ii) 3D-CT reconstruction of the images by an appropriate CT algorithm. In this paper, first, as a preliminary research, 3D-CT reconstruction of non-axisymmetric steady flame is made with a single-directional quantitative schlieren system. Next, with custom-made 20 directional schlieren camera, instantaneous density distributions of a high-speed turbulent flames of nozzle exit velocities of 8.0 and 10.0 m/s has been CT-reconstructed. The 3D-views of the reconstructed flame front shape clearly give the information of the flame structure with fine scale corrugations. Based on the distributions, area-enlargement rates of the flame front area are derived, and investigated. 相似文献
16.
Xingchao Wang Yudai Huang Dianzeng Jia Zaiping Guo Duo Ni Ming Miao 《Journal of Solid State Electrochemistry》2012,16(1):17-24
Olivine LiFePO4/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared
by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure
and electrochemical properties of the samples were investigated. The results show that LiFePO4/C nanocomposite with oxalic acid (oxalic acid: Fe2+= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1
C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding
at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of
148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO4/C cathode materials can be exploited suitably for practical lithium-ion batteries. 相似文献
17.
Atsushi?NarumiEmail author Yudai?Kimura Seigou?Kawaguchi 《Colloid and polymer science》2012,290(4):379-384
The precipitation polymerizations of N-tert-butylacrylamide (NtBAM) in water are demonstrated; for example, the polymerization with potassium peroxodisulfate using a 15 g L−1 (118 mmol L−1) concentration of NtBAM in the feed ([NtBAM]0) was performed at 70 °C for 12 h, quantitatively producing poly(N-tert-butylacrylamide) particles with a number-average diameter (d
n) of 203 nm and a coefficient of variation (C
v) of 4.7%. The particle sizes were controlled in the d
ns range between 75 and 494 nm by changing the monomer feeds or adding an electrolyte such as NaCl. The solid contents in the
resulting aqueous latex solutions ranged from 0.1 to 1.5%, whereas it increased to 4.8% by applying a “shot-growth” technique.
The polymerization in water under a somewhat unique condition is described, which was started from a heterogeneous system
due to the presence of significantly large amounts of monomers ([NtBAM]0 = 50 g L−1). This also provided monodisperse latexes with the d
n of 370 nm in 96% yield, in which the solid content reached 4.9%. 相似文献
18.
Hongli Wu Yudai Huang Dianzeng Jia Zaiping Guo Ming Miao 《Journal of nanoparticle research》2012,14(1):713-7
Spinel Li4Ti5O12 nanoparticles were prepared via a high-temperature solid-state reaction by adding the prepared cellulose to an aqueous dispersion
of lithium salts and titanium dioxide. The precursors of Li4Ti5O12 were characterized by thermogravimetry and differential scanning calorimetry. The obtained Li4Ti5O12 nanoparticles were characterized using X-ray diffraction, transmission electron microscopy (TEM) and electrochemical measurements.
The TEM revealed that the Li4Ti5O12 prepared with cellulose is composed of nanoparticles with an average particle diameter of 20–30 nm. Galvanostatic battery
testing showed that nano-sized Li4Ti5O12 exhibit better electrochemical properties than submicro-sized Li4Ti5O12 do especially at high current rates, which can deliver a reversible discharge capacity of 131 mAh g−1 at the rate of 10 C, whereas that of the submicro-sized sample decreases to 25 mAh g−1 at the same rate (10 C). Its reversible capacity is maintained at ~172.2 mAh g−1 with the voltage range 1.0–3.0 V (vs. Li) at the current rate of 0.5 C for over 80 cycles. 相似文献
19.
S Kurimoto K Suzuki M Okasaka Y Kashiwada OK Kodzhimatov Y Takaishi 《Chemical & pharmaceutical bulletin》2012,60(7):913-919
Seven new sesquiterpene lactone glycosides (1-7) were isolated from the H2O-soluble fraction from the MeOH extract of the roots of Ferula varia. Their structures were elucidated by extensive spectroscopic analyses. The absolute configurations of compounds 1 and 2 were determined by modified Mosher's method. 相似文献
20.
(1,4,7,10-Tetraazacyclododecane) [diamine or (S)-alanine]-cobalt(III) complexes [diamine = ethylenediamine, 2-(aminomethyl)pyridine, (R)-1,2-propanediamine, (R,R)-1,2-diaminocyclohexane, trimethylenediamine and 2-methyl-1,3-diaminopropane] are prepared and characterized spectroscopically. The ligand field transitions occur at lower energies than those of the corresponding tetraamine analogues. Severe distortions caused by the too small size of the cyclic ligand are one of the origins. The distortions also exert influence upon circular dichroism spectra. 相似文献