全文获取类型
收费全文 | 737篇 |
免费 | 51篇 |
国内免费 | 6篇 |
专业分类
化学 | 587篇 |
晶体学 | 17篇 |
力学 | 8篇 |
数学 | 25篇 |
物理学 | 157篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 48篇 |
2012年 | 35篇 |
2011年 | 47篇 |
2010年 | 28篇 |
2009年 | 21篇 |
2008年 | 42篇 |
2007年 | 25篇 |
2006年 | 30篇 |
2005年 | 38篇 |
2004年 | 27篇 |
2003年 | 29篇 |
2002年 | 34篇 |
2001年 | 35篇 |
2000年 | 27篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 18篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1986年 | 2篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1968年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有794条查询结果,搜索用时 46 毫秒
751.
Kobayashi J Nakamura M Mori Y Yamashita Y Kobayashi S 《Journal of the American Chemical Society》2004,126(30):9192-9193
We have developed an efficient method for the asymmetric synthesis of anti-beta-hydroxy-alpha-amino acid derivatives based on highly enantio- and diastereoselective aldol reactions of the silicon enolate derived from N-trifluoroacetylglycinate with aldehydes using a chiral zirconium catalyst. The resulting N-trifluoroacetyl group is easily cleaved under either acidic or basic conditions and can be used directly as a protecting group for further transformations. 相似文献
752.
In terms of beable algebras Halvorson and Clifton [International Journal of Theoretical Physics 38 (1999) 2441–2484] generalized the uniqueness theorem (Studies in History and Philosophy of Modern Physics 27 (1996) 181–219] which characterizes interpretations of quantum mechanics by preferred observables. We examine whether dispersion-free
states on beable algebras in the generalized uniqueness theorem can be regarded as truth-value assignments in the case where
a preferred observable is the set of all spectral projections of a density operator, and in the case where a preferred observable
is the set of all spectral projections of the position operator as well. 相似文献
753.
Increase of photoluminescence (PL) from fullerenes (C60 and C70)-doped poly(alkyl methacrylate), such as poly(ethyl methacrylate) (PEMA), poly(isopropyl methacrylate) (PiPMA) and poly(isobutyl methacrylate) (PiBMA), have been studied under laser irradiation with wavelength of in air. After laser irradiation, PL peaks of all fullerenes doped-polymers are broadened and blue-shifted. This PL increase depends on the fullerene concentrations. By comparing with fullerenes-doped PMMA, fullerenes-doped PEMA have the greatest PL increase among the four kinds of polymers, including PEMA, PiPMA, PiBMA and PMMA. PL intensity of C70-doped polymers increases much more quickly than the corresponded C60-doped polymers at the initial stage of laser irradiation. Great change on their UV-visible absorption spectra before and after laser irradiation indicate some great variation on chemical structure of fullerene molecules dispersed in polymer matrix under laser irradiation. This great PL increase may be attributed to formation of fullerene oxide-polymer and oxidized fullerene-polymer adducts due to laser-induced photochemical reactions among fullerene, oxygen and polymer. 相似文献
754.
Hyunsuk Moon Yuichiro Taguchi 《Proceedings of the American Mathematical Society》2001,129(9):2529-2534
It is proved that, for a number field and a prime number , there exist only finitely many isomorphism classes of continuous semisimple Galois representations of into of fixed dimension and bounded Artin conductor outside which have solvable images. Some auxiliary results are also proved.
755.
The efficiencies of contamination source, defined in ISO Report 7506-1, were experimentally determined for such materials as flooring, polyethylene, smear-tested filter paper and stainless steel plate. 5 nuclides of 147Pm, 60Co, 137Cs, 204Tl and 90Sr-Y were used to study beta-ray energy dependence of the efficiency, and 241Am as alpha-ray emitter. The charge-up effect in the measurement by a window-less 2 pi-proportional counter was evaluated to obtain reliable surface emission rate. The measured efficiencies for non-permeable materials, except for two cases, are more than 0.5 even for 147Pm. The ISO recommendations were shown to be conservative enough on the basis of present results. 相似文献
756.
757.
I. Ogawa T. Idehara A. Sakai K. Yoshida T. Tsuchida K. Kawahata A. Ejiri H. Iguchi K. Tanaka K. Matsuoka R. Akiyama M. Osakabe S. Okamura T. Minami C. Takahashi W. Kasparek 《International Journal of Infrared and Millimeter Waves》1998,19(5):727-736
Intense submillimeter wavelength radiation (f=354 GHz, P=110 W) from Gyrotron FU II is converted into a well-collimated, linearly-polarized beam by a quasi-optical transmission line consisting of a quasi-optical antenna and several mirrors. The observed focusing of the beam agrees with calculations based on the Huygens equation. We have used this intense beam to study low frequency density fluctuations by plasma scattering in Compact Helical System (CHS) plasmas at the National Institute for Fusion Science. 相似文献
758.
759.
Hong Hai Tomoo Miura Tomoyoshi Kobayashi Yuichiro Maéda Masao Miki 《Journal of fluorescence》2000,10(2):193
Contraction of vertebrate striated muscle is regulated by the strong Ca2+-dependent interaction among troponin (Tn), tropomyosin (Tm), and actin on the thin filament. Using fluorescence resonance energy transfer (FRET), the interactions between Tm and the Tn complex or between Tm and the Tn subunit, TnI or TnC, with or without other troponin subunits, were characterized in the presence or absence of F-actin and Ca2+ ions. Cys-190 of Tm was selectively labeled with the acceptor probe, 4-dimethylaminophenylazophenyl 4-maleimide. Troponin was selectively labeled at position 9 or 133 of TnI and position 98 of TnC with a donor probe, 5-(2-iodoacetylaminoethyl)aminonaphtha lene 1-sulfonic acid. FRET measurements indicate that the interaction between TnI and Tm alone is very weak, but that in the presence of F-actin, TnI binds to the proper binding site on Tm even in the absence of TnT. The distances between Cys-190 of Tm on F-actin and Cys-9 or Cys-133 of Tnl or Cys-98 of TnC in the reconstituted Tn were determined to be 52.8, 53.7, Å and 56.5 Å, respectively, in the absence of Ca2+, indicating that the Tnl—TnC complex, the globular portion of Tn, is located near Cys-190 of Tm on the reconstituted thin filaments. Upon binding of Ca2+ to TnC, these distances increased by 5.6 and 1.4 Å or decreased by 5.4 Å, respectively. These Ca2+-induced changes in Tn—Tm seem to occur only when F-actin is present, suggesting that the stable complex formation of TnI with the outer domain of F-actin upon removal of Ca2+ is a very important event during inhibition. 相似文献
760.
Minami T Okamoto H Ikeda S Tanaka R Ozawa F Yoshifuji M 《Angewandte Chemie (International ed. in English)》2001,40(23):4501-4503