全文获取类型
收费全文 | 155726篇 |
免费 | 1698篇 |
国内免费 | 421篇 |
专业分类
化学 | 86600篇 |
晶体学 | 2464篇 |
力学 | 6209篇 |
综合类 | 3篇 |
数学 | 14738篇 |
物理学 | 47831篇 |
出版年
2021年 | 1100篇 |
2020年 | 1278篇 |
2019年 | 1364篇 |
2018年 | 1708篇 |
2017年 | 1766篇 |
2016年 | 2723篇 |
2015年 | 1687篇 |
2014年 | 2509篇 |
2013年 | 6356篇 |
2012年 | 5254篇 |
2011年 | 6430篇 |
2010年 | 4421篇 |
2009年 | 4421篇 |
2008年 | 6145篇 |
2007年 | 5942篇 |
2006年 | 5818篇 |
2005年 | 5330篇 |
2004年 | 4833篇 |
2003年 | 4427篇 |
2002年 | 4308篇 |
2001年 | 5660篇 |
2000年 | 4121篇 |
1999年 | 3182篇 |
1998年 | 2241篇 |
1997年 | 2328篇 |
1996年 | 2201篇 |
1995年 | 2060篇 |
1994年 | 2054篇 |
1993年 | 1828篇 |
1992年 | 2323篇 |
1991年 | 2398篇 |
1990年 | 2229篇 |
1989年 | 2203篇 |
1988年 | 2186篇 |
1987年 | 2169篇 |
1986年 | 2003篇 |
1985年 | 2504篇 |
1984年 | 2497篇 |
1983年 | 2016篇 |
1982年 | 2043篇 |
1981年 | 1870篇 |
1980年 | 1838篇 |
1979年 | 2136篇 |
1978年 | 2188篇 |
1977年 | 2133篇 |
1976年 | 2050篇 |
1975年 | 1924篇 |
1974年 | 1920篇 |
1973年 | 1953篇 |
1972年 | 1277篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Hellweg T. Schemmel S. Rother G. Brlet A. Eckerlebe H. Findenegg G.H. 《The European physical journal. E, Soft matter》2003,12(1):1-4
The European Physical Journal E - The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D2O) in a mesoporous silica glass (CPG-10-75) of... 相似文献
172.
We investigate the dynamics of the Λ system driven by two resonant laser fields in presence of dissipation for coupling strengths where the rotating‐wave approximation starts to break down. This regime is characterised by Rabi frequencies being approximately equal or smaller than the field frequencies. A systematic procedure to obtain an expansion for the solution of the Bloch evolution equations of the system is presented. The lowest contribution results to be the well‐known rotating‐wave approximation. The method is based on a semi‐classical treatment of the problem, and its predictions are interpreted fully quantum mechanically. The theory is illustrated by a detailed study of the disappearance of coherent population trapping as the intensities of the fields increase. 相似文献
173.
The crystal structure, magnetic and magnetotransport properties of the variation of B′-site transition metal in Sr2FeMO6 (M=Mo, W) with double perovskites structure have been investigated systematically. Measurements of magnetization vs. temperature at H=5 T show that Sr2FeMoO6 is a ferromagnet and Sr2FeWO6 is an antiferromagnet with TN∼35 K. Additionally, the large magnetoresistance ratio (MR) of ∼22% (H=3 T) at room temperature (RT) was observed in the Sr2FeWO6 compound. However, the Sr2FeMoO6 compound did not show any significant MR even at high fields and RT (MR∼1%; H=3 T and 300 K). The implications of these findings are supported by band structure calculations to explain the interaction between the 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions. 相似文献
174.
I. M. Kolthoff S. R. Cooper V. J. Tulane F. Reimers H. A. J. Pieters K. Höppner V. H. Matula C. B. Macek W. N. Skworzow J. S. Schepelewa F. Čuta K. Kámen S. Cohen R. E. Oesper D. S. Narayanamurthi T. R. Seshadri H. M. State A. W. Kirssanow W. M. Tscherkassow D. M. Mukherjee T. Akiyama Y. Mine S. Yabe Y. Volmar M. Déribéré 《Analytical and bioanalytical chemistry》1937,111(5-6):192-197
175.
A method has been developed for the determination of melengestrol acetate in bovine tissues at lower levels than previously reported. Liquid-liquid extraction of tissue homogenates provided crude clean-up while final isolation, screening, and quantification was done on-line with an automated, normal-phase, coupled-column high-performance liquid chromatographic system. The chromatographic system included phenyl and silica analytical columns for the purposes of isolation and final separation, respectively. These columns provided a large difference in selectivity when operated under normal-phase conditions which allowed for the efficient isolation of melengestrol acetate from the complex tissue extracts. Mobile phases were composed of hexane and dichloromethane modified with methanol and water. Transfer and enrichment of the analyte from the primary phenyl column to the silica column was via a short (12 mm x 4 mm I.D.) silica column. Regeneration and equilibration of the phenyl column was performed after the injection of each tissue extract and was accomplished simultaneously while analytical separation occurred on the final silica column. Routing of the mobile phases and regeneration solvent was performed with automated switching valves. The total time required for each analysis was 12 min. Quantification is demonstrated using external standards with UV detection at 287 nm. The overall recovery of the method was 86% with a coefficient of variation of 9.84% at the 10 ppb [the American billion (10(9] is used in this article] level in bovine liver extracts. 相似文献
176.
G. Tóth 《Journal of Radioanalytical and Nuclear Chemistry》1989,137(4):259-264
The distribution of mono- poly- and unlabelled protein molecules in the radiolabelling mixture was calculated from probability point of view as a function of the radioiodine/protein ratio. 相似文献
177.
178.
T.S. Khlebnicova V.G. Isakova A.V. Baranovsky E.V. Borisov F.A. Lakhvich 《Journal of fluorine chemistry》2006,127(12):1564-1569
A one-pot synthesis of 2-perfluoroalkanoylcyclohexane-1,3-diones via C-acylation of cyclohexane-1,3-diones with N-perfluoroacylimidazole as an acylating agent is reported. A reaction was examined with isolated N-trifluoroacetylimidazole and with N-perfluoroacylimidazoles generated in situ from perfluorocarboxylic acid anhydrides or perfluorocarboxylic acids. 相似文献
179.
180.