全文获取类型
收费全文 | 14907篇 |
免费 | 550篇 |
国内免费 | 43篇 |
专业分类
化学 | 10135篇 |
晶体学 | 232篇 |
力学 | 464篇 |
综合类 | 1篇 |
数学 | 1125篇 |
物理学 | 3543篇 |
出版年
2024年 | 71篇 |
2023年 | 169篇 |
2022年 | 442篇 |
2021年 | 430篇 |
2020年 | 472篇 |
2019年 | 529篇 |
2018年 | 497篇 |
2017年 | 466篇 |
2016年 | 671篇 |
2015年 | 483篇 |
2014年 | 775篇 |
2013年 | 1275篇 |
2012年 | 1113篇 |
2011年 | 1161篇 |
2010年 | 771篇 |
2009年 | 599篇 |
2008年 | 729篇 |
2007年 | 733篇 |
2006年 | 563篇 |
2005年 | 495篇 |
2004年 | 386篇 |
2003年 | 313篇 |
2002年 | 261篇 |
2001年 | 157篇 |
2000年 | 132篇 |
1999年 | 99篇 |
1998年 | 73篇 |
1997年 | 100篇 |
1996年 | 94篇 |
1995年 | 74篇 |
1994年 | 70篇 |
1993年 | 94篇 |
1992年 | 97篇 |
1991年 | 77篇 |
1990年 | 68篇 |
1989年 | 71篇 |
1988年 | 49篇 |
1987年 | 47篇 |
1986年 | 43篇 |
1985年 | 63篇 |
1984年 | 63篇 |
1983年 | 54篇 |
1982年 | 47篇 |
1981年 | 40篇 |
1980年 | 46篇 |
1979年 | 65篇 |
1978年 | 49篇 |
1977年 | 53篇 |
1976年 | 41篇 |
1975年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
D. Rekha K. Suvardhan K. S. Kumar G. R. K. Naidu P. Chiranjeevi 《Journal of Analytical Chemistry》2006,61(12):1177-1182
A simple, sensitive, and rapid flow-injection spectrophotometric method was developed for the determination of trace amounts
of selenium(IV). The method is based on the oxidation reaction of 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH)
by selenium(IV) followed by the coupling reaction with chromotropic acid (4.5-dihydroxy naphthalene-2.7-disulphonic acid)
in a basic medium (phosphate buffer, pH 10.5) to give a pink derivative with λmax 530 nm that is stable for more than 7 days at 35°C. The reaction and flow conditions of the full experimental design were
optimized. A detection limit (2s) of 0.25 μg/L Se(IV) was obtained at a sampling rate of 10 samples per hour. Beer’s law is
obeyed for a Se(IV) concentration range of 0.05–0.5 μg/mL at the wavelength of maximum absorption. The detailed study of various
interference ions indicates that the method is highly selective. The method was successfully applied to the determination
of traces of selenium(IV) in various water samples. The results obtained were in good agreement with those obtained by the
reported methods at the 95% confidence level.
The text was submitted by the authors in English. 相似文献
82.
The kinetics of substitution of aqua ligands fromcis-diaqua-bis(biguanide)cobalt(III) and chromium(III) ions by aspartic acid in EtOH–H2O media have been studied spectrophotometrically in the 30 to 45°C range. We propose the following rate law for the anation
相似文献
83.
Titanium oxide on silica-alumina support is described to be an efficient regenerable catalyst for alkylation of aromatic compounds with alkyl halides, alcohols and olefins, and the reaction is proposed to be initiated by the protonated metal active species present in the catalyst. 相似文献
84.
Raj Kumar 《Colloid and polymer science》1979,257(1):95-97
Summary Estimation of zeta potential from experimental data on electroosmotic and electrophoretic effects for Zeokarb 225 (Na+ form)/methanol-water system has been made and discussed. Results indicate that zeta potentials estimated from electroosmotic flux and electrophoretic mobility are not in agreement and vary with applied potential difference in a linear manner. Reasons for the variation of zeta potential with electrical field have been discussed. It has been argued that zeta potentials estimated from electroosmotic data are more reliable in comparison to the values obtained from electrophoretic data.With 2 figures and 2 tables 相似文献
85.
Arya P Couve-Bonnaire S Durieux P Laforce D Kumar R Leek DM 《Journal of combinatorial chemistry》2004,6(5):735-745
A solid-phase synthesis of tetrahydroquinoline-derived polycyclic 4, having a medium size ring with an enamide functionality, was achieved from tetrahydroquinoline derivative 3 in five steps with overall 40-45% yield. An enantiopure, tetrahydroquinoline-derived beta-amino ester, 1, was converted into compound 2 that has a free phenolic hydroxyl group as an anchoring site for solid-phase synthesis. The solid-phase worked well for this sequence, in which the synthesis of the unsaturated eight-membered enamide lactam was obtained by a ring-closing metathesis approach. Compound 4 is a novel, natural product-like polycyclic derivative that could further be utilized in library generation for developing small molecule chemical probes. 相似文献
86.
87.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Duboscq JE Elliott JR Escobar CO Gibney M Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Pinfold J Punkar G Purohit MV Santoro AF Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundia AB Witherell MS 《Physical review D: Particles and fields》1991,43(7):R2063-R2066
88.
Anjos JC Appel JA Bean A Bediaga I Bracker SB Browder TE Cremaldi LM Duboscq JE Elliot JR Escobar CO Gibney MC Hartner GF Karchin PE Kumar BR Lima JG Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Pinfold J Punkar G Purohit MV Ross WR Santoro AF Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundzia AB Witherell MS 《Physical review letters》1992,69(20):2892-2895
89.
90.
|