全文获取类型
收费全文 | 122篇 |
免费 | 4篇 |
专业分类
化学 | 102篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 3篇 |
物理学 | 10篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有126条查询结果,搜索用时 15 毫秒
1.
Oxime-based salen-type tetradentate ligands with high stability against imine metathesis reaction 总被引:2,自引:0,他引:2
Akine S Taniguchi T Dong W Masubuchi S Nabeshima T 《The Journal of organic chemistry》2005,70(5):1704-1711
Although salen and its analogues are versatile chelate ligands in inorganic and organometallic chemistry, synthesis of unsymmetrical salen derivatives consisting of two different salicylideneimine moieties is difficult because of the C=N bond recombination. To develop stable analogues of salen-type ligands, we synthesized a series of new ligands salamo (=1,2-bis(salicylideneaminooxy)ethane) on the basis of O-alkyl oxime instead of the imine moiety. Eight salamo ligands 1a-h were prepared in 64-88% yields as colorless crystals from the corresponding salicylaldehydes 2a-h. The crystal structure of 1a-c suggests that the oxime-OH form is more predominant than the keto-NH form. The reaction of 2a-e with excess 1,2-bis(aminooxy)ethane gave monooximes 3a-e in 59-86%, which further reacted with a different salicylaldehyde to afford unsymmetrical salamo ligands 4-8 as stable crystals in 51-70%. No reaction took place when a mixture of salamo derivatives 1a and 1b was treated at 40 degrees C in H2O/MeCN (5:95). However, the metathesis reaction of salen derivatives 9a and 9b completed in 2 h to give a statistical mixture. Monooxime 3b was much more stable than monoimine 11 which is difficult to be isolated. These results indicate the extremely high stability of the salamo derivatives 1 and precursors 3. 相似文献
2.
The bis(dibutylstannylene) derivative of 1,2-cyclohexylidene-myo-inositol reacted with (S)-O-acetylmandeloyl chloride and diphosphate tetraesters to give 3,6-dimandelate and 3-phosphate, respectively. Using the stannylene methodology for the optical resolution and regioselective phosphorylation of the ketal, a concise synthesis of phosphatidylinositol with the natural configuration was accomplished. 相似文献
3.
M. Seto Yu. Maeda T. Matsuyama H. Yamaoka H. Sakai S. Masubuchi S. Kazama 《Hyperfine Interactions》1992,68(1-4):213-216
A nonconjugated conducting polymer (1,4-rans-polyisoprene) at different iodine doping levels has been studied with the 27.7-keV Mössbauer resonance of129I. At the light doping level, almost all iodines are covalently bonding to the carbon atoms, breaking the double bonds of the main chain. At the medium doping level, other iodine species are found, which are idendified as anion species, l?, l 3 ? and l 3 ? .At the heavy doping level, polyiodide anions, l 3 ? and l 5 ? , increase as compared to the covalently bonding iodine atoms and addtionally molecular iodine l2 exists. 相似文献
4.
Ando M Takizawa M Suwabe S Yamato S Shimada K 《European journal of mass spectrometry (Chichester, England)》2003,9(6):619-622
Analysis of selenium in biological samples is very important and numerous analytical methods for the element have been developed. One of the most convenient and widely used methods for routine determination of serum selenium is a fluorometric method using 2,3-diaminonaphthalene (DAN); however, this method lacks specificity. We observed that 4,5-benzopiazselenol (BPS), a selenium derivative of DAN, is ionized with electron capture in an atmospheric pressure chemical ionization (APCI) interface, and subsequently established a method for determining total human serum selenium by means of liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. All pretreatment procedures were carried out in a single test tube to minimize selenium loss. The recovery of organic or inorganic selenium spiked to human serum was 97-103%.The detection limit of BPS was equivalent to 0.2 ng of selenium and the lower quantitative limit of serum selenium was 10 ng mL(-1). The coefficient of variation of standard concentrations in control serum samples was 4.5%. The purity of the observed peak obtained from serum samples was confirmed using the ion cluster technique. 相似文献
5.
Masayuki Kirihara Takuya Noguchi Nobuhiro Okajima Sayuri Naito Yuki Ishizuka Aiko Harano Hiroyuki Tsukiji Ryu Takizawa 《Tetrahedron》2012,68(5):1515-1520
The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions. 相似文献
6.
7.
A new total synthesis of the neuronal cell-protecting carbazole alkaloid carbazomadurin A is described. The key step was an allene-mediated electrocyclic reaction involving an indole [b]-bond for the construction of a highly substituted carbazole ring. The E-alkenyl side chain at the C1 position of carbazole was introduced between O-triflate and alkenyl pinacol borate using the Suzuki-Miyaura reaction. SEM groups were cleaved with TBAF and the formyl group was reduced to provide carbazomadurin A. 相似文献
8.
Caesaljaponins A and B: New Cassane‐Type Furanoditerpenoids from the Seeds of Caesalpinia decapetala var. japonica
下载免费PDF全文
![点击此处可从《Helvetica chimica acta》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Two new cassane‐type furanoditerpenoids, designated caesaljaponin A and caesaljaponin B ( 1 and 2 , resp.), were isolated from seeds of Caesalpinia decapetala var. japonica. The structures were elucidated by spectroscopic data, and the absolute configuration of 1 was determined by X‐ray crystallographic analysis using the anomalous scattering of CuKα radiation. 相似文献
9.
Hiroshi Kimura Koichiro Aikawa Yuichi Masubuchi Jun-ichi Takimoto K. Koyama Keiji Minagawa 《Rheologica Acta》1998,37(1):54-60
The mechanism of the electrorheological (ER) effect in two types of liquid crystalline polymer (LCP)/dimethylsiloxane (DMS)
blends was investigated by rheological measurements and by structure observation under electric field and shear flow. The
results show that the phase structures of these immiscible blends can be categorized into slipping (low viscosity) and non-slipping
(high viscosity) states. In the non-slipping state, higher viscosity LCP domains connect the electrodes. In the slipping state,
on the other hand, LCP domains do not connect the electrodes and the shear is mainly confined in the lower viscosity DMS domains.
The ER effect (electrically induced viscosity increase) originates from the electrically induced slipping to non-slipping
transition. In one of the blends, the ER effect occurs only at high shear rate, since this blend is in non-slipping state
even under no field if the shear rate is low.
Received: 29 April 1997 Accepted: 3 November 1997 相似文献
10.
Masubuchi M Toyota T Yamada M Seki M 《Chemical communications (Cambridge, England)》2011,47(29):8433-8435
Molecular self-assemblies exhibiting automatic motions have received much attention as potential artificial models of living organisms. We have developed a microfluidic picolitre nozzle-array device to form multilamellar lipid tubes (MLTs) under fluidic shear stress, which transformed into different two patterns (yarn-balls and double-helixes) and also exhibited unique self-actuation behaviors. 相似文献