全文获取类型
收费全文 | 1233篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
化学 | 919篇 |
晶体学 | 18篇 |
力学 | 20篇 |
数学 | 108篇 |
物理学 | 197篇 |
出版年
2023年 | 6篇 |
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 45篇 |
2012年 | 58篇 |
2011年 | 74篇 |
2010年 | 37篇 |
2009年 | 40篇 |
2008年 | 75篇 |
2007年 | 85篇 |
2006年 | 83篇 |
2005年 | 67篇 |
2004年 | 77篇 |
2003年 | 43篇 |
2002年 | 70篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 18篇 |
1996年 | 30篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1992年 | 5篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 19篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 13篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有1262条查询结果,搜索用时 15 毫秒
161.
D. P. E. Dickson R. K. Pollard B. Borch-Iohnsen R. J. Ward T. J. Peters 《Hyperfine Interactions》1988,42(1-4):889-892
Mössbauer spectra obtained from the haemosiderin isolated from ironoverloaded horse and reindeer spleen and liver show superparamagnetic behaviour with a much lower transition temperature than haemosiderin from iron-overloaded human spleen. These data clearly indicate the existence of different forms of haemosiderin, which are primarily distinguishable by Mössbauer spectroscopy. 相似文献
162.
V.K. Sankaranarayanan Q.A. Pankhurst D.P.E. Dickson C.E. Johnson 《Journal of magnetism and magnetic materials》1994,130(1-3):288-292
Ultrafine particles of lithium ferrite have been prepared at the unusually low temperatures of 240 and 455°C by a citrate precursor method. The materials obtained after annealing at temperatures between 455 and 700°C consist of ordered lithium ferrite as shown by the characteristics infrared absorptions, the X-ray diffraction superstructure reflections, and the 4.2 K Mössbauer spectra. The values of magnetization obtained are somewhat low, due to the presence of small quantities of an -Fe2O3 phase, which can also be observed in the X-ray diffraction and the Mössbauer spectra. 相似文献
163.
164.
A cubic triangle-free graph has a bipartite subgraph with at least 4/5 of the original edges. Examples show that this is a best possible result. 相似文献
165.
Aija Zirnis Joseph K. Suzuki Donald E. Dickson Robert A. Laitar Albert A. Manian 《Journal of heterocyclic chemistry》1977,14(1):107-112
The synthesis of 7-hydroxy, 8-hydroxy and 7,8-dihydroxy prochlorperazines (3a) and per-phenazines (3b) is reported. The parent ehlorophenothiazines were prepared analogously to previously reported chlorpromazine (3e) metabolite syntheses. The prochlorperazine side chain was introduced in one step using 1-(3-chloropropyl)-4-methylpiperazine and the perphenazine side chain in two steps, first reaction with 1-bromo-3-chloropropane followed by reaction with 1-piperazineethanol. The methoxymethyleneoxy O-proteetive groups were removed under mild conditions using methanolic hydrogen chloride. The preparations of 7-hydroxydesmethylprochlorperazine and 7-hydroxychlorpromazine quaternary methyl iodide are also reported. 相似文献
166.
Soldier termites of three species of (Isoptera: Nasutitermitinae) contain macrocyclic lactones possessing from 22 to 36 carbon atoms and novel C24 and C26 α- and β-hydroxy macrolides as the primary components of their cephalic secretions. 相似文献
167.
Xray and spectral data are presented for two new tetracyclic diterpenes isolated from a termite soldier defensive secretion. 相似文献
168.
George W. Gokel Harold M. Gerdes David E. Miles John M. Hufnal Glenn A. Zerby 《Tetrahedron letters》1979,20(36):3375-3378
The title heterocycle is used as a carbonyl anion equivalent in the preparation of aldehydes and α-silyl ketones; the key step is the thermal demasking of the heterocycle by loss of isobutylene and sulfur dioxide. 相似文献
169.
170.
A convergent two-step process is described for the synthesis of ene-1,5-diols that provides for union of two carbonyl electrophiles via a formal pentenyl dianion equivalent. 相似文献