全文获取类型
收费全文 | 1723篇 |
免费 | 39篇 |
国内免费 | 8篇 |
专业分类
化学 | 1359篇 |
晶体学 | 7篇 |
力学 | 26篇 |
数学 | 122篇 |
物理学 | 256篇 |
出版年
2023年 | 9篇 |
2021年 | 8篇 |
2020年 | 21篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 28篇 |
2015年 | 32篇 |
2014年 | 34篇 |
2013年 | 91篇 |
2012年 | 100篇 |
2011年 | 121篇 |
2010年 | 66篇 |
2009年 | 78篇 |
2008年 | 77篇 |
2007年 | 92篇 |
2006年 | 115篇 |
2005年 | 95篇 |
2004年 | 82篇 |
2003年 | 71篇 |
2002年 | 78篇 |
2001年 | 28篇 |
2000年 | 34篇 |
1999年 | 32篇 |
1998年 | 22篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 18篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 26篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 36篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 22篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有1770条查询结果,搜索用时 31 毫秒
971.
972.
Mitsuhiro Okuda Masaki Takeguchi Motohiro Tagaya Toru Tonegawa Ayako Hashimoto Nobutaka Hanagata Toshiyuki Ikoma 《Micron (Oxford, England : 1993)》2009,40(5-6):665-668
Elemental distribution of calcium, phosphorus, oxygen, and carbon in a single collagen fibril obtained from tilapia fish scales was identified with an electron energy-loss spectroscopy and an energy-filtered transmission electron microscopy, for the first time. The carbon intensity profile of the single collagen fibril showed the specific D-periodic pattern at 67 nm of type I collagen fibrils. The calcium L2,3-edge and oxygen K-edge peak positions were detected at 347/350 eV and 137 eV, respectively, and these positions were identical to those of hydroxyapatite. Calcium, phosphorus, and oxygen were present in the hole zones as the amorphous phase, while carbon was present in the overlap zone. Our results indicated that the hole zones preferentially attract calcium and phosphate ions and thus serve as possible nucleation sites for mineralization. 相似文献
973.
K. Kawashima M. Kriener M. Ishii Y. Maeno J. Akimitsu 《Physica C: Superconductivity and its Applications》2008,468(6):464-470
We report normal-state and superconducting properties of the clathrate-type silver-oxide Ag6O8AgHF2. We present electrical resistivity, DC- and AC-susceptibility and specific-heat measurements of single crystalline Ag6O8AgHF2. In the normal state, Ag6O8AgHF2 exhibits metallic conductivity and a phase transition near 110 K, possibly a structural phase transition as observed in the related compound Ag6O8AgNO3. The onset of superconductivity of our samples is observed around 1.2–1.5 K, and the H–T phase diagram is determined for the first time. The upper critical field Hc2(0) is estimated to be about 2000–2200 Oe and the coherence length ξGL(0) to be 40 nm. 相似文献
974.
The surface structure of the alkali-leached single-phase Ni3Al powder was investigated by X-ray diffraction, BET (Brunauer-Emmett-Teller) surface area analysis, electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction. It was found that fine Ni particles of several nm in diameter were formed on the outer surface layer of the Ni3Al powder after the alkali leaching process. The surface of the Ni particles was covered with a thin layer of Ni oxides and hydroxide, Ni2O3, NiO and Ni(OH)2, and these Ni oxides and hydroxide can be easily reduced by hydrogen to the metallic nickel that is catalytically active. The inside of the Ni3Al powder remained as the original Ni3Al ordered structure after alkali leaching. Having heat resistant properties, the Ni3Al phase can serve as a support of the fine Ni particles and provide the structural and thermal stabilities to the fine Ni particles. 相似文献
975.
Yusuke Takara Koji FujiwaraYoshiyuki Ishihara Toshiyuki Todaka 《Journal of magnetism and magnetic materials》2008
A single sheet tester (SST) for audio frequency of 400 Hz–10 kHz was made experimentally and the magnetizing winding can get the nearly uniform distribution of flux density of a specimen in the longitudinal direction at the frequency up to 10 kHz. The flux densities at various positions of strips measured by the Epstein method were detected by search coils wound on strips at 400 Hz and 1.0 T. They have large discrepancy. However, the magnetic properties obtained from both methods have a little discrepancy. Although the uniformity of flux distribution in the Epstein frame is not sufficient, the average is fairly effective because the magnetic properties can be assumed to be locally linear within the small deviation of flux density. 相似文献
976.
977.
Liquid-crystalline stereoregular polyketone prepared from a mesogenic vinylarene and carbon monoxide
Yasutoyo Kawashima Kyoko Nozaki Tamejiro Hiyama Masafumi Yoshio Kiyoshi Kanie Takashi Kato 《Journal of polymer science. Part A, Polymer chemistry》2003,41(22):3556-3563
Isotactic and syndiotactic polyketones were synthesized by the alternating copolymerizations of a mesogenic vinylarene, 4-cyano-4′-[8-(4-vinylphenyl)octyl-1-oxy]biphenyl, with carbon monoxide, and this revealed the influence of backbone tacticity on their thermal properties. The isotactic polyketone was an amorphous polymer that did not show any mesophase, whereas the syndiotactic polyketone exhibited liquid crystallinity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3556–3563, 2003 相似文献
978.
979.
Shoichi Ichinose Chiaki Itoh Toshiyuki Minamikawa Kimio Miura Tsunetoshi Watanabe 《Nuclear Physics B》1985,260(1):113-124
On the basis of the background field method, extended one-loop counterterm formulae are derived, and a method to get the two-loop double-pole counter lagrangian is given. As an example, the double-pole divergences of ξ2X3 counterterms are obtained. 相似文献