全文获取类型
收费全文 | 221篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
化学 | 175篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 7篇 |
物理学 | 38篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 15 毫秒
81.
82.
Matsumoto S Batmunkh E Akazome M Takata Y Tamano M 《Organic & biomolecular chemistry》2011,9(17):5941-5944
Reaction of 1,2-di(imidazolyl)benzene treated with n-BuLi proceeded to give diimidazo[1,2-a:2',1'-c]quinoxaline in the presence of iodine or Pd(PPh(3))(4). Blue fluorescence was observed from 3,10-diarylated diimidazoquinoxalines with high quantum yield. They were also applied to organic light-emitting devices as emitters, in which the diphenyl derivative emits a nearly pure blue light. 相似文献
83.
Yamashige R Kimoto M Mitsui T Yokoyama S Hirao I 《Organic & biomolecular chemistry》2011,9(21):7504-7509
We developed intramolecular dual fluorophore-quencher base analogues for site-specific incorporation into DNA by an unnatural base pair replication system. An unnatural base pair between 7-(2-thienyl)-imidazo[4,5-b]pyridine (Ds) and 2-nitro-4-propynylpyrrole (Px) exhibits high fidelity in PCR amplification, and the 2-nitropyrrole moiety of Px acts as a quencher. Deoxyribonucleoside triphosphates of Px linked with a fluorophore (Cy3, Cy5 or FAM) were chemically synthesized, and the fluorescent properties and the enzymatic incorporation of the fluorophore-linked dPxTPs into DNA were examined in PCR amplification. The fluorophore-linked dPxTPs were site-specifically incorporated by PCR into DNA, opposite Ds in templates, with high selectivity. Furthermore, we found that the fluorescence of the triphosphates was partially quenched, but increased upon their incorporation into DNA. These dual fluorophore-quencher base analogues would be useful for site-specific DNA labeling and for monitoring the amplification products of target nucleic acid molecules with a specific sequence. We have demonstrated the utility of the fluorophore-linked Px substrates and the Ds-Px pairing in real-time quantitative PCR for target DNA molecule detection. 相似文献
84.
85.
86.
Michiko Narazaki Yoko Kanazawa Sachiko Koike Koichi Ando Hiroo Ikehira 《Magnetic resonance imaging》2013
17O magnetic resonance imaging (MRI) using a conventional pulse sequence was explored as a method of quantitative imaging towards regional oxygen consumption rate measurement for tumor evaluation in mice. At 7 T, fast imaging with steady state (FISP) was the best among gradient echo, fast spin echo and FISP for the purpose. The distribution of natural abundance H217O in mice was visualized under spatial resolution of 2.5 × 2.5 mm2 by FISP in 10 min. The signal intensity by FISP showed a linear relationship with 17O quantity both in phantom and mice. Following the injection of 5% 17O enriched saline, 17O re-distribution was monitored in temporal resolution down to 5 sec with an image quality sufficient to distinguish each organ. The image of labeled water produced from inhaled 17O2 gas was also obtained. The present method provides quantitative 17O images under sufficient temporal and spatial resolution for the evaluation of oxygen consumption rate in each organ. Experiments using various model compounds of R-OH type clarified that the signal contribution of body constituents other than water in the present in vivo17O FISP image was negligible. 相似文献
87.
Pekka Pyykkö Prof. Michiko Atsumi Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12770-12779
The previous systems of triple‐bond and single‐bond self‐consistent, additive covalent radii, R(AB)=r(A)+ r(B), are completed with a fit for σ2π2 double‐bonds.The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same, self‐consistent fit. Many of the calculated primary data came from E?CH2 and H? E?CH2 models. Homonuclear LE?EL, formaldehyde‐type Group 14–Group 16 and open‐shell, X 3 Σ Group‐16 dimer data are included. The standard deviation for the 316 included data points is 3 pm. 相似文献
88.
Florian Eweiner Shunsuke Senda Klaus Bergander Dr. Christian Mück‐Lichtenfeld Dr. Stefan Grimme Prof. Dr. Roland Fröhlich Dr. Michiko Aoyama Hiroyuki Kawaguchi Prof. Dr. Yasuhiro Ohki Dr. Tsuyoshi Matsumoto Dr. Gerald Kehr Dr. Kazuyuki Tatsumi Prof. Dr. Gerhard Erker Prof. Dr. 《化学:亚洲杂志》2009,4(12):1830-1833
Treatment of the salt [PPh4]+[Cp*W(S)3]? ( 6 ) with allyl bromide gave the neutral complex [Cp*W(S)2S‐CH2‐CH?CH2] ( 7 ). The product 7 was characterized by an X‐ray crystal structure analysis. Complex 7 features dynamic NMR spectra that indicate a rapid allyl automerization process. From the analysis of the temperature‐dependent NMR spectra a Gibbs activation energy of ΔG≠ (278 K)≈13.7±0.1 kcal mol?1 was obtained [ΔH≠≈10.4±0.1 kcal mol?1; ΔS≠≈?11.4 cal mol?1 K?1]. The DFT calculation identified an energetically unfavorable four‐membered transition state of the “forbidden” reaction and a favorable six‐membered transition state of the “Cope‐type” allyl rearrangement process at this transition‐metal complex core. 相似文献
89.
Yuki Odanaka Takuya Kanemitsu Kanako Iwasaki Yukiko Mochizuki Michiko Miyazaki Kazuhiro Nagata Masaru Kato Takashi Itoh 《Tetrahedron》2019,75(2):209-219
A highly enantioselective construction of an all-carbon quaternary stereogenic center at the α-position of malonic diesters has been achieved by Michael addition using phase-transfer catalysis. The reaction of α-monosubstituted malonates with acrylates in the presence of N-(9-anthracenylmethyl)quininium chloride as a phase-transfer catalyst afforded the corresponding α,α-disubstituted malonic diesters in high chemical yields (up to >95% yield) with high enantioselectivities (up to 95% ee). Furthermore, the product was amenable to chemoselective transformation and could be successfully converted to the corresponding α,α-disubstituted amino acid derivatives through Curtius rearrangement. 相似文献
90.
Toyofumi Nakanishi Akira Shimizu Nobuhiko Okamoto Arnd Ingendoh Michiko Kanai 《Journal of the American Society for Mass Spectrometry》1995,6(9):854-859
Serum transferrin precipitated with specific antisera was analyzed by matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI/TOF-MS) and electrospray ionization-mass spectrometry (ESI-MS). When analyzed by MALDI, transferrin showed signal peaks that clearly could be separated from ions of IgG present in the immunoprecipitate. By ESI-MS, when the immunoprecipitates were loaded through a microcapillary polymeric reversed-phase column connected to the electrospray ionization probe, the mass spectra of transferrin were observed with a high signal-to-noise ratio and good resolution. By MALDI/TOF-MS, the observed molecular weight of normal transferrin was ~ 1.2 ku smaller when analyzed in the reflectron mode than in the linear mode. The observed molecular weight of transferrin treated with sialidase was approximately the same in both modes. A comparison between the results obtained in both modes may help to estimate the number of sialic acids on the protein molecule. A transferrin isoform with a molecular weight of ~2.2 ku less than the normal species was identified in the serum of patients with a carbohydrate-deficient glycoprotein syndrome as well as in heavy alcohol consumers. 相似文献