全文获取类型
收费全文 | 2402篇 |
免费 | 70篇 |
国内免费 | 2篇 |
专业分类
化学 | 1377篇 |
晶体学 | 25篇 |
力学 | 66篇 |
数学 | 209篇 |
物理学 | 797篇 |
出版年
2021年 | 17篇 |
2020年 | 20篇 |
2019年 | 20篇 |
2016年 | 65篇 |
2015年 | 42篇 |
2014年 | 38篇 |
2013年 | 92篇 |
2012年 | 69篇 |
2011年 | 85篇 |
2010年 | 71篇 |
2009年 | 58篇 |
2008年 | 95篇 |
2007年 | 99篇 |
2006年 | 91篇 |
2005年 | 59篇 |
2004年 | 63篇 |
2003年 | 51篇 |
2002年 | 57篇 |
2001年 | 66篇 |
2000年 | 55篇 |
1999年 | 53篇 |
1998年 | 28篇 |
1997年 | 31篇 |
1996年 | 39篇 |
1995年 | 38篇 |
1994年 | 32篇 |
1993年 | 36篇 |
1992年 | 55篇 |
1991年 | 30篇 |
1990年 | 49篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 23篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 34篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 44篇 |
1979年 | 36篇 |
1978年 | 27篇 |
1977年 | 40篇 |
1976年 | 24篇 |
1975年 | 29篇 |
1974年 | 22篇 |
1973年 | 22篇 |
1971年 | 22篇 |
1967年 | 26篇 |
1966年 | 21篇 |
排序方式: 共有2474条查询结果,搜索用时 609 毫秒
51.
52.
53.
54.
55.
V. K. Panday J. S. Becker H. -J. Dietze 《Fresenius' Journal of Analytical Chemistry》1995,352(3-4):327-334
Bis(2-ethyl hexyl)-orthophosphoric acid in toluene has been used to extract scandium selectively from an aqueous phase containing nearly thirty elements at various concentrations. The trace elements (Li, Mg, Al, Mn, Co, Ni, Cu, Zn, Ga, Sr, Y, Cd, In, Sb, Ba, REE, Hf, Pt, Tl, Pb, Bi and u) have been determined quantitatively in the aqueous phase using inductively coupled plasma mass spectrometry (ICP-MS). The recoveries have been quantitative for most of the analytes studied and ICP-MS has been found suitable for the determination of trace quantities of these elements in the aqueous extract. The procedure has been applied to the quantitative ultra-trace analysis of rare earth elements (REE) and other trace impurities in high purity scandium metal (4N) using ICP-MS and ID-ICP-MS techniques.Presented in part at the 2nd Regensburger Symposium Massenspektrometrische Verfahren der Elementspurenanalyse, 6.-8.10.93, Regensburg, Germany 相似文献
56.
Normal-phase high-performance liquid chromatograms of retinal, retinol and retinyl palmitate isomers using n-heptane-tert.-butyl methyl ether as mobile phase are presented. Methods for the synthesis of various isomers of these retinoids are described. This enables one to produce standard chromatograms and to select various isomers for cochromatography and the identification of the various peaks under study. Assignment of the peaks is based on chromatograms published previously in this journal. For the main isomers it is possible to get baseline separation of the commonly occurring isomeric forms in a reasonably short analysis time. 相似文献
57.
Graham R. Underwood Brajeswar Paul M. Alice Becker 《Journal of heterocyclic chemistry》1976,13(6):1229-1232
Pyridoxol, protected by acetylation of the hydroxyl groups, has been converted to its N-oxide which upon reaction with perfluoroacetie anhydride yields a 2-nor-2-hydroxymethylpyridoxol derivative as an intermediate. This compound undergoes acyl migration from the 3-position. Protection of the pyridoxol hydroxyls by benzylalion followed by the same treatment yields the unrearranged α2-hydroxy derivative. This compound has been converted to a series of α2-substituted pyridoxols (X = -Cl, -Br, -OCOCH3, -OCH3, -OC2H5). 相似文献
58.
Baltrusaitis RM Becker JJ Blaylock GT Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V Coward DH Cui H Del Papa C Dorfan DE Duncan AL Einsweiler KF Eisenstein BI Fabrizio R Gladding G Grancagnolo F Hamilton RP Hauser J Heusch CA Hitlin DG Köpke L Mockett PM Moss L Mozley RF Nappi A Odian A Partridge R Perrier J Plaetzer SA Richman JD Roehrig JR Russell JJ Sadrozinski HF Scarlatella M Schalk TL Schindler RH Seiden A Sleeman JC Spadafora AL Thaler JJ Toki W Unno Y Villa F Wattenberg A 《Physical review letters》1985,55(17):1723-1726
59.
A unique matrix system consisting mostly of 4-nitrophenol has shown to be very effective for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of large DNA oligomers when a cooled sample stage was used to prevent the sublimation of this matrix under vacuum. Using this 4-nitrophenol matrix with UV laser desorption, detection of picomole quantities of DNA oligomers containing up to approximately 800 nucleotides was routinely achieved. The effectiveness of this matrix was further demonstrated by the observation of a double-stranded DNA oligomer larger than 1000 base pairs, seen as a denatured single-stranded species, with a molecular ion mass exceeding 300 000 Da. The potential applications of 4-nitrophenol as a matrix for DNA sizing are discussed. 相似文献
60.