全文获取类型
收费全文 | 11907篇 |
免费 | 312篇 |
国内免费 | 29篇 |
专业分类
化学 | 8531篇 |
晶体学 | 100篇 |
力学 | 128篇 |
数学 | 1544篇 |
物理学 | 1945篇 |
出版年
2020年 | 112篇 |
2019年 | 108篇 |
2016年 | 204篇 |
2015年 | 212篇 |
2014年 | 183篇 |
2013年 | 396篇 |
2012年 | 378篇 |
2011年 | 486篇 |
2010年 | 292篇 |
2009年 | 274篇 |
2008年 | 435篇 |
2007年 | 434篇 |
2006年 | 409篇 |
2005年 | 445篇 |
2004年 | 414篇 |
2003年 | 356篇 |
2002年 | 319篇 |
2001年 | 225篇 |
2000年 | 216篇 |
1999年 | 169篇 |
1998年 | 150篇 |
1997年 | 172篇 |
1996年 | 214篇 |
1995年 | 186篇 |
1994年 | 193篇 |
1993年 | 184篇 |
1992年 | 170篇 |
1991年 | 164篇 |
1990年 | 142篇 |
1989年 | 155篇 |
1988年 | 169篇 |
1987年 | 169篇 |
1986年 | 168篇 |
1985年 | 196篇 |
1984年 | 170篇 |
1983年 | 157篇 |
1982年 | 164篇 |
1981年 | 160篇 |
1980年 | 149篇 |
1979年 | 142篇 |
1978年 | 139篇 |
1977年 | 141篇 |
1976年 | 140篇 |
1975年 | 119篇 |
1974年 | 152篇 |
1973年 | 128篇 |
1961年 | 145篇 |
1960年 | 204篇 |
1959年 | 111篇 |
1958年 | 120篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Klaus Beyermann 《Fresenius' Journal of Analytical Chemistry》1961,183(2):91-107
Zusammenfassung Es wird gezeigt, daß mit Hilfe von Fuchsin eine colorimetrische Bestimmung von Rhenium in Mengen von 1–10 g mit einer Standardabweichung von 0,1 g möglich ist. Ein Abtrennungsverfahren, bestehend aus Sublimation des Rheniums und dessen Extraktion mit Tetraphenylarsoniumchlorid gestattet die Anwendung der colorimetrischen Methode zur Erfassung von Rheniumgehalten von 10–1 bis 10–4% in Mineralien und technischen Produkten.Herrn Prof. Geilmann und Herrn Prof. Bock danke ich für anregende Diskussionen. Herrn Prof. Strassmann und Herrn Dr. Herrmann bin ich für die Erlaubnis zur Benutzung der Hilfsmittel der radiochemischen Abteilung und für gegebene Ratschläge zu Dank verpflichtet. 相似文献
192.
Grotjahn DB Van S Combs D Lev DA Schneider C Incarvito CD Lam KC Rossi G Rheingold AL Rideout M Meyer C Hernandez G Mejorado L 《Inorganic chemistry》2003,42(10):3347-3355
Inter- and intramolecular hydrogen bonding of an N-H group in pyrazole complexes was studied using ligands with two different groups at pyrazole C-3 and C-5. At C-5, groups such as methyl, i-propyl, phenyl, or tert-butyl were present. At C-3, side chains L-CH(2)- and L-CH(2)CH(2)- (L = thioether or phosphine) ensured formation of chelates to a cis-dichloropalladium(II) fragment through side-chain atom L and the pyrazole nitrogen closest to the side chain. The significance of the ligands is that by placing a ligating side chain on a ring carbon (C-3), rather than on a ring nitrogen, the ring nitrogen not bound to the metal and its attached proton are available for hydrogen bonding. As desired, seven chelate complexes examined by X-ray diffraction all showed intramolecular hydrogen bonding between the pyrazole N-H and a chloride ligand in the cis position. In addition, however, intermolecular hydrogen bonding could be controlled by the substituent at C-5: complexes with either a methyl at C-5 or no substituent there showed significant intermolecular hydrogen bonding interactions, which were completely avoided by placing a tert-butyl group at C-5. The acidity of two complexes in acetonitrile solutions was estimated to be closer to that of pyridinium ion than those of imidazolium or triethylammonium ions. 相似文献
193.
Humic substances were analysed by atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) mass spectrometry in positive and negative modes. Using APCI the average m/z range of humic substances was reduced 5-fold compared to ESI. High-resolution time-of-flight mass spectrometry revealed the formation of multiply charged molecules in the ESI mode. Moreover, it was possible to obtain daughter ion mass spectra of humic substances by nanospray tandem mass spectrometry. The size-exclusion chromatography elution profile of humic substances was highly influenced by the pH of the analyte solution. By contrast, the pH had no significant influence on the observed mass spectra of humic substances. 相似文献
194.
Larry I. Amstutz Horst Meyer Samuel M. Myers
Robert L. Mills
《Journal of Physics and Chemistry of Solids》1969,30(12):2693-2697Measurements of T1 in the hep phase of H2, over the temperature range 2°–12°K and the ortho concentration range between 0.5 and 0.97 are presented. At temperatures below 10°K, the thermally activated self-diffusion is negligible and the mechanism for nuclear relaxation is that attributed by Moryia and Motizuki and by Harris to intramolecular dipolar interaction, modulated by intennolecular electric quadrupole-quadrupole (EQQ) interaction. The gaussian approximation for the correlation function was used by these authors to predict T1. From the comparison between experiment and theory, we determine the EQQ parameter Γ/kB to be 0.67°K. Above 10°K the effect of diffusion influences T1, and the experimental results for an 88 per cent ortho H2 sample up to the melting point suggest that the relaxation mechanisms resulting from EQQ interaction and diffusion are not independent of one another. 相似文献
195.
Klaus Hoechsmann 《Rendiconti del Circolo Matematico di Palermo》1995,44(1):5-20
Let ζ be a primitivesp-th root of unity for a primep>2, and consider the group Ω(ζ) of cyclotomic units in the ringR(ζ)=ℒ[ζ+ζ-1]. This paper deals with the image of Ω(ζ) in the unit group ofR(ζ)/qR(ζ), whereq is a prime ≠p. In particular, it obtains criteria for this image to be essentially everything, and a lower bound on the density of primesp (withq fixed) for which it cannot be. These results have a direct bearing on previous work about units in integral group rings for
cyclic groups of orderpq.
Work supported in part by an operating grant from NSERC (Canada). 相似文献
196.
Summary We prove that a
d
-action by automorphisms of a compact, abelian group is Bernoulli if and only if it has completely positive entropy. The key ingredients of the proof are the extension of certain notions of asymptotic block independence from -actions to
d
-action and their equivalence with Bernoullicity, and a surprisingly close link between one of these asymptotic block independence properties for
d
-actions by automorphisms of compact, abelian groups and the product formula for valuations on global fields.Oblatum 20-X-1994 相似文献
197.
Abe K Akagi T Anthony PL Antonov R Arnold RG Averett T Band HR Bauer JM Borel H Bosted PE Breton V Button-Shafer J Chen JP Chupp TE Clendenin J Comptour C Coulter KP Court G Crabb D Daoudi M Day D Dietrich FS Dunne J Dutz H Erbacher R Fellbaum J Feltham A Fonvieille H Frlez E Garvey D Gearhart R Gomez J Grenier P Griffioen KA Hoibraten S Hughes EW Hyde-Wright C Johnson JR Kawall D Klein A Kuhn SE Kuriki M Lindgren R Liu TJ Lombard-Nelsen RM Marroncle J Maruyama T Maruyama XK McCarthy J Meyer W 《Physical review letters》1995,74(3):346-350
198.
199.
200.