全文获取类型
收费全文 | 223篇 |
免费 | 22篇 |
专业分类
化学 | 201篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 4篇 |
物理学 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 17篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 15篇 |
2007年 | 19篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有245条查询结果,搜索用时 15 毫秒
151.
Polymerization of 2,5‐diaminoterephthalic acid‐type monomers for the synthesis of polyamides containing ladder unit 下载免费PDF全文
Akihiro Yokoyama Jinya Kuramochi Ryohei Kiyota Kazuki Kishimoto Kazuto Takaishi Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2017,55(14):2365-2372
To synthesize ladder‐type polyamides by construction of two amide bonds successively, 2,5‐diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide‐linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2365–2372 相似文献
152.
153.
Prof. Naokazu Kano Dr. Nathan J. O'Brien Dr. Ryohei Uematsu Dr. Romain Ramozzi Prof. Keiji Morokuma 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5976-5979
The first trihydroborate bearing a pentacoordinated phosphorus atom was synthesized as a new P−B bonded compound. Hydride abstraction of the trihydroborate gave an intermediary dihydroborane, which showed hydroboration reactivity and was trapped with pyridine whilst maintaining the P−B bond. The dihydroborane underwent a rearrangement, which involved a double ring expansion to compensate for the unbalanced coordination states of the phosphorus and boron atoms, to give a new fused bicyclic phosphine-boronate. 相似文献
154.
Carboxylate‐Driven Supramolecular Assemblies of Protonated meso‐Aryl‐Substituted Dipyrrolylpyrazoles 下载免费PDF全文
Prof. Hiromitsu Maeda Kengo Chigusa Dr. Ryohei Yamakado Dr. Tsuneaki Sakurai Prof. Shu Seki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9520-9527
Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4‐position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single‐crystal X‐ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge‐carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates. 相似文献
155.
Yoshimi Ohmae Atsushi Hirose Ryohei Sugita Keitaro Tanoi Tomoko M. Nakanishi 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):413-416
As an approach to increased production of rape seed oil from Brassica napus L., Arabidopsis thaliana, a species from the same Brassicaceae family, was used to investigate transport behavior and distribution of matter in the plant body. In this study, sucrose, an initial metabolic product of photosynthesis, labeled with carbon-14 was used. The sucrose was applied to A. thaliana via the surface of a rosette leaf. Using the real time radioisotope imaging system we developed and an imaging plate (IP), images of whole or part of the sample were obtained. The sucrose assimilation products were accumulated in maturing tissue such as flowers and fruits, and in a joint part. From the comparison among branches and stems, it was indicated that there were different patterns of demand and distribution of sucrose assimilation products depending on the tissue and its growing stage. This might be caused by either morphological reason such as diameter and location of the sieve tube, or genetic factors such as an activity of a membrane transport protein. Because of self-absorption of carpels, it was difficult to observe the accumulation of carbon-14 in the seeds inside the fruits; however, an IP image of a frozen section of a fruit revealed that carbon-14 transport to seeds was higher than that of carpels. These methods will help us gain insight into matter transport and strategies to improve the production of rape seed oil. 相似文献
156.
Tsuyoshi Ichiyanagi Mayumi FukunagaRyoya Tagashira Shie HayashiMasato Nanjo Ryohei Yamasaki 《Tetrahedron》2011,67(33):5964-5971
Methyl (7,8-di-O-benzoyl-4,5-O-isopropylidene-3-deoxy-d-manno-2-oct-ulopyranoside)onate was found to be a useful new intermediate in the synthesis of an inner-core oligosaccharide of lipooligosaccharides and lipopolysaccharides produced by gram-negative bacteria. This intermediate could be converted to the corresponding glycosyl fluoride and 4,5-diol acceptor with ease. Syntheses of dimeric Kdo, O-(sodium 3-deoxy-α-d-manno-2-octuropyranosylonate)-(2-4)-sodium (allyl 3-deoxy-α-d-manno-2-octuropyranoside)onate, and O-(sodium 3-deoxy-α-d-manno-2-octuropyranosylonate)-(2-8)-sodium (allyl 3-deoxy-α-d-manno-2-octuropyranoside)onate were successfully demonstrated. 相似文献
157.
Chunhong Zhang Fangbin Liu Qianqian Geng Shuang Zhang Xiande Shen Ryohei Kakuchi Hideki Misaka Toyoji Kakuchi Toshifumi Satoh Ryosuke Sakai 《European Polymer Journal》2011,47(10):1923-1930
The living ring-opening polymerization of l-lactide was carried out by using organocatalyst to synthesize the molecular weight controlled poly(l-lactide) with an phenylacetylenyl end group (HCCPLLA), then the homopolymerization of HCCPLLA was performed by using two different rhodium catalysts. Low molecular weight poly-PLLA6-1 (Mw,SEC-MALLS = 46,700) was synthesized by using Rh(nbd)BPh4 as the catalyst, and higher molecular weight poly-PLLA6-2 (Mw,SEC-MALLS = 471,000) was synthesized by using the [Rh(nbd)Cl]2/Et3N catalyst system. Then high molecular weight poly-PLLA20, poly-PLLA29, and poly-PLLA68 were successfully synthesized by using the [Rh(nbd)Cl]2/Et3N catalyst system. The α values of the poly-PLLAs using [Rh(nbd)Cl]2/Et3N catalyst system were all in the range of 0.6–0.8, this means that these polymers possess linear flexible chain. It is concluded that [Rh(nbd)Cl]2/Et3N was more suitable for the synthesis of the cylindrical polymer brush, poly-PLLA with high molecular weight. The analyses of the CD spectra indicated that poly-PLLA possesses a predominantly one-handed helical conformation, temperature and solvents had significant influences on the helical structure of poly-PLLA. 相似文献
158.
Yaseen Ali Mosa MohamedFuyuhiko Inagaki Ryohei TakahashiChisato Mukai 《Tetrahedron》2011,67(29):5133-5141
A new approach for the synthesis of 2-vinylindole derivatives by 5-exo mode cyclization of 2-(3-silyloxymethylallenyl)anilines was developed. The starting allenylanilines were easily prepared by the Stille coupling of o-iodoaniline and allenylstannanes. The formed 2-vinylindole derivatives were transformed into several carbazole derivatives via the [4+2] cycloaddition reaction with suitable dienophiles. 相似文献
159.
Juno Kim Prof. Dr. Ryohei Kishi Dr. Eiichi Kayahara Dr. Woojae Kim Prof. Dr. Shigeru Yamago Prof. Dr. Masayoshi Nakano Prof. Dr. Dongho Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17137-17144
Upon photon absorption, π-conjugated organics are apt to undergo ultrafast structural reorganization via electron-vibrational coupling during non-adiabatic transitions. Ultrafast nuclear motions modulate local planarity and quinoid/benzenoid characters within conjugated backbones, which control primary events in the excited states, such as localization, energy transfer, and so on. Femtosecond broadband fluorescence upconversion measurements were conducted to investigate exciton self-trapping and delocalization in cycloparaphenylenes as ultrafast structural reorganizations are achieved via excited-state symmetry-dependent electron-vibrational coupling. By accessing two high-lying excited states, one-photon and two-photon allowed states, a clear discrepancy in the initial time-resolved fluorescence spectra and the temporal dynamics/spectral evolution of fluorescence spectra were monitored. Combined with quantum chemical calculations, a novel insight into the effect of the excited-state symmetry on ultrafast structural reorganization and exciton self-trapping in the emerging class of π-conjugated materials is provided. 相似文献
160.
Hanayo Kita Dr. Ryohei Yamakado Risa Fukuuchi Tatsuki Konishi Dr. Kenji Kamada Dr. Yohei Haketa Prof. Hiromitsu Maeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3404-3410
Two-photon absorption (TPA) dyes with intense fluorescence can be used to detect small chemical species and as sensors and bioimaging probes for specific analytes. Various TPA dyes responding to a number of external stimuli have been reported. Among them, biologically important anionic species have not been used as agents to control TPA properties because their direct electronic influences on the transition dipole moments of dyes are typically small. In this study, dipyrrolyldiketone BF2 complexes substituted with π-extended units exhibited efficient TPA properties that could be regulated by conformation changes induced by anion binding. The TPA intensity decreased to 1/5 of the original intensity upon anion binding, which was much larger than that observed for one-photon absorption. Anion detection was achieved by a change in the emission intensity of spatially resolved spots of two-photon-excited fluorescence (TPEF) in the sample. Experimental and theoretical studies were performed to understand the mechanism of the TPA property control and showed that the drastic changes in the transition dipole moments upon conformation changes between the straight and bending forms of the π-electronic systems caused the TPA and TPEF intensities drop. 相似文献