全文获取类型
收费全文 | 177篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学 | 136篇 |
数学 | 12篇 |
物理学 | 31篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有179条查询结果,搜索用时 46 毫秒
1.
2.
T. Nagaishi S. Ishiyama M. Matsumoto S. Yoshinaga 《Journal of Thermal Analysis and Calorimetry》1984,29(1):121-129
The reactions between ammonium sulphate and three metal oxides (Cr2O3, MnO2 and Fe2O3) were studied. It was confirmed by X-ray diffraction and chemical analysis that stable reaction intermediates were formed consecutively in the course of the reactions.These were (NH4)3M(SO4)3 and NH4M(SO4)2 for Cr2O3 and Fe2O3 and (NH4)2Mn2(SO4)3 for MnO2. The thermal decompositions of these intermediates and of the metal sulphates were carried out. The contracting-volume equation was valid for the decomposition of all the intermediates. The Arrhenius parameters were determined.
Zusammenfassung Es wurden die Reaktionen zwischen Ammoniumsulfat und drei Metalloxiden (Cr2O3, MnO2 und Fe2O3) untersucht. Durch Röntgendiffraktion und chemische Analyse wurde bestätigt, dass im Verlaufe der Reaktion stabile Zwischenprodukte gebildet werden. Es handelt sich dabei um (NH4)3M(SO4)3 und NH4M(SO4)2 im Falle von Cr2O3 und Fe2O3 und um (NH4)2Mn2(SO4)3 im Falle von MnO2. Diese Zwischenprodukte und die Metallsulfate wurden thermisch zersetzt. Die Volumenkontraktionsgleichung war für die Zersetzung all dieser Zwischenprodukte gültig. Die Arrheniusparameter wurden bestimmt.
Cr2O3, MnO2 Fe2O3. , . , (NH4)3M(SO4)3 NH4M(SO4)2, (NH4)2Mn2(SO4)3. . . .相似文献
3.
Hirokazu Morisawa Takashi Utagawa Takeshi Miyoshi Fumihiro Yoshinaga Akihiro Yamazaki Koji Mitsugi 《Tetrahedron letters》1980,21(5):479-482
An enzymatic transarabinosylation between 2-chlorohypoxanthine and 1-β--arabinofuranosyluracil gave 9-β--arabinofuranosyl-2-chlorohypoxanthine which was chemically converted to 9-β--arabinofuranosylguanine and its derivatives. 相似文献
4.
Inorganic-organic hybrids have been synthesized by incorporation of the inorganic component of Ti(OC2H5)4 into the organic polymer of ethyl cellulose. The inorganic-organic hybrids did not dissolve in toluene used as a solvent for the starting materials. The ethanol was formed as a by-product of the alcoholysis condensation reaction between Ti(OC2H5)4 and ethyl cellulose. These results suggest that ethoxy groups of Ti(OC2H5)4 react with hydroxy groups of ethyl cellulose to form cross-linking bonds of –O–Ti–O–. The reaction of Ti(OC2H5)4 with ethyl cellulose was further investigated by Fourier transform infrared (FT-IR) spectroscopy. The FT-IR spectroscopic experiments revealed that the Ti–O bond state of Ti(OC2H5)4 was changed by refluxing a toluene solution of Ti(OC2H5)4 with ethyl cellulose. The inorganic-organic hybrids have an interesting dielectric property; their dielectric constant is higher than that of ethyl cellulose and that of a simple mixture of TiO2 and ethyl cellulose. 相似文献
5.
The chiral separation ability of unmodified and di- and trimethylated -, β- and γ-cyclodextrins (CDs) as chiral selectors in capillary zone electrophoresis was investigated in the presence of urea derivatives using twelve dansylamino acids as model solutes. The addition of these urea derivatives (unsubstituted, methyl-, ethyl- and 1,3-dimethylureas) produced dramatic enhancement in the enantioselectivity of unmodified β-CD but also reduced the enantioselectivities of the other CDs. 相似文献
6.
[reaction: see text] We describe an efficient template-directed photoligation of oligodeoxynucleotides (ODNs) using alpha-5-cyanovinyldeoxyuridine (alpha(C)U). An efficient photoligation was produced by photoirradiation of an ODN containing alpha(C)U at the 3' end with an ODN containing thymine at the 5' end in the presence of a template ODN. This photoligation method is a new and efficient way to synthesize branched ODNs. 相似文献
7.
Hashimoto T. Yoshinaga M. Ueda Y. Komazaki K. Asaoka K. Wang S. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):909-917
The phase transitions of Ba2-xSrxIn2O5 were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure
of Ba2-xSrxIn2O5 with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature.
The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted
perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba2-xSrxIn2O5 was established and existence of tricritical point at ~1100°C with x=0.4~0.5 was suggested.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Minoru Tanaka Masanobu Yoshinaga Satoshi Asano Yuko Yamashoji Yoshihiro Kawaguchi 《Fresenius' Journal of Analytical Chemistry》1992,343(12):896-900
Summary The enantiomeric separation ability of unmodified and methylated cyclodextrins (CDs) during capillary zone electrophoresis (CZE) was investigated using twelve dansylamino acids. Unmodified - and -CDs exhibited high enantioselectivities. -CD could scarcely separate the enantiomers before and after dimethylation, but obtained enantioselectivity after trimethylation. On the other hand, dimethylation of -CD removed much of its high enantioselectivity. Moreover, the chemical modifications produced a reverse in the migration order of the enantiomers. The inclusion of dansyl-DL-phenylalanine with CDs was evaluated using 600 MHz 1H NMR spectroscopy. 相似文献
9.
Summary The cross-linkings of the surface polymer layer on mono disperse, poly(maleic anhydride-styrene)-modified silica particles
by the reaction with diisocyanate were studied. The extent of cross-linking was estimated by the weight decrease by immersing
the particles in the buffer solution of pH 2.0, 4.0 and 9.0 at a room temperature for 24 h. The reaction of the polymer-modified
silica with 1,6-diisocyanatohexane afforded relatively stable composite particles which lost less than 5 wt% of the polymer
in aqueous solution in the pH range 2.0–9.0. The diisocyanate was a preferable cross-linker to 2,4-diisocyanatotoluene in
terms of stability in acidic or basic aqueous solution. The flexibility of the cross-linker molecule possibly plays an important
role in the cross-linking reaction. The carboxyl and amino groups were formed by treating the cross-linked composite particles
with diluted HCl solution; 5–6 and 0.5–1.1 μmol g-1, respectively. The cross-linked composite particles exhibited the characteristic property of ζ-potential, −44 to −47 mV and
−102 to −107 mV in a neutral aqueous solution and ethanol, respectively.
Received: 26 May 1997 Accepted: 4 August 1997 相似文献
10.
Mitsuru Kitamura Kenji KuboShogo Yoshinaga Hiroki MatsuzakiKantaro Ezaki Taisuke MatsuuraDaigo Matsuura Noriyuki FukuzumiKeiichiro Araki Masafumi Narasaki 《Tetrahedron letters》2014
A synthetic study of kosinostatin aglycone is reported. Synthesis of key intermediate lactone 3, which corresponds to the BCDE ring fragment, was accomplished, and the precursor BCD ring fragment 5 was synthesized via two routes. First, 5 was synthesized from 2,5-dimethoxybenzaldehyde 16 by the combination of typical known transformations including efficient application of non-aqueous OsO4 oxidation in the presence of PhB(OH)2. However the synthesis required 15 long steps, and its main difficulty was ortho-alkoxycarbonylmethylation of 1-naphthol. Next we attempted to apply our recently developed alkoxycarbonylmethylation of diazonaphthoquinone for the synthesis of 5, and 5 was successfully synthesized in 9 steps from the same starting compound 16. Finally, 5 was stereoselectively converted to lactone 3 via trifluoroacetic acid-mediated cyclization of the 3,4-epoxycylohexanecarboxylic acid derivative. 相似文献