全文获取类型
收费全文 | 9377篇 |
免费 | 1509篇 |
国内免费 | 1192篇 |
专业分类
化学 | 6900篇 |
晶体学 | 85篇 |
力学 | 585篇 |
综合类 | 82篇 |
数学 | 967篇 |
物理学 | 3459篇 |
出版年
2024年 | 32篇 |
2023年 | 175篇 |
2022年 | 287篇 |
2021年 | 306篇 |
2020年 | 323篇 |
2019年 | 322篇 |
2018年 | 250篇 |
2017年 | 245篇 |
2016年 | 408篇 |
2015年 | 358篇 |
2014年 | 543篇 |
2013年 | 638篇 |
2012年 | 768篇 |
2011年 | 824篇 |
2010年 | 570篇 |
2009年 | 555篇 |
2008年 | 660篇 |
2007年 | 546篇 |
2006年 | 474篇 |
2005年 | 490篇 |
2004年 | 354篇 |
2003年 | 334篇 |
2002年 | 349篇 |
2001年 | 289篇 |
2000年 | 245篇 |
1999年 | 210篇 |
1998年 | 193篇 |
1997年 | 166篇 |
1996年 | 164篇 |
1995年 | 126篇 |
1994年 | 147篇 |
1993年 | 103篇 |
1992年 | 118篇 |
1991年 | 100篇 |
1990年 | 76篇 |
1989年 | 77篇 |
1988年 | 43篇 |
1987年 | 26篇 |
1986年 | 37篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
131.
132.
Micellar electrokinetic capillary chromatography (MEKC) with aqueous organic solvent has been developed to separate polycyclic aromatic hydrocarbons (PAHs). Methanol, ethanol or propanol as an organic modifier was added to sodium dodecyl sulfate (SDS) micellar solution in order to increase the solubility of very hydrophobic solutes in mobile phase. Both methanol and ethanol can be used as co-solvents for the separation of PAHs. Use of ethanol resulted in a shorter analysis time than use of methanol. The separations of some PAHs were unsatisfactory using propanol although the analysis time was much shorter than with ethanol. The influence of ethanol content, SDS concentration and temperature on the separations was studied. Benzene and nine polycyclic aromatic hydrocarbons were successfully separated using 50 mM SDS-20 mM phosphate-5 mM borate, containing 40% (v/v) ethanol at 35 degrees C. The relative standard deviation (R.S.D.) of t(R) ranged from 0.5 to 1.5% for six repeat injections. 相似文献
133.
134.
Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Whitmore J Wilson P Butler F Fu X Kalbfleisch G Lambrecht M Ross WR Skubic P Snow J Wang PL Wood M Bortoletto D Brown DN Fast J McIlwain RL Miao T Miller DH Modesitt M Schaffner SF Shibata EI Shipsey IP Wang PN Battle M Ernst J Kroha H Roberts S Sparks K Thorndike EH Wang CH Dominick J Sanghera S Skwarnicki T Stoynowski R Artuso M He D Goldberg M Horwitz N Kennett R 《Physical review letters》1993,71(20):3259-3262
135.
Cinabro D Henderson S Kinoshita K Liu T Saulnier M Wilson R Yamamoto H Sadoff AJ Ammar R Ball S Baringer P Coppage D Copty N Davis R Hancock N Kelly M Kwak N Lam H Kubota Y Lattery M Nelson JK Patton S Perticone D Poling R Savinov V Schrenk S Wang R Alam MS Kim IJ Nemati B O'Neill JJ Romero V Severini H Sun CR Zoeller MM Crawford G Fulton R Fujino D Gan KK Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y Sung M White C Whitmore J Wilson P Butler F Fu X Kalbfleisch G Lambrecht M Ross WR 《Physical review letters》1993,70(24):3700-3704
136.
137.
偏最小二乘及双波长K系数光度法同时测定矿物中钛,铁 总被引:3,自引:0,他引:3
本文运用化学计量学中的偏最小二乘法及双波长K系数法实现了Ti、Fe的同时测定,方法用于铝钒土及钛铁矿中Ti、Fe同时测定,结果满意。 相似文献
138.
Novel chiral monodentate phosphorus ligands, SIPHOS, were conveniently synthesized from 1,1'-spirobiindane-7,7'-diol. The Rh complexes of SIPHOS can catalyze the hydrogenation of alpha-dehydroamino esters in mild conditions, providing alpha-amino acid derivatives in up to 99% ee. Enamides and beta-dehydroamino esters can also be hydrogenated in good to excellent enantioselectivities (up to 99% and 94% ee, respectively). The SIPHOS ligand with smaller alkyl groups on the N-atom afforded higher enantioselectivity. The X-ray analysis of single crystal showed that the structure of Rh/SIPHOS catalyst is [Rh(COD)((S)-SIPHOS-Me)(2)](+), which clarified the configuration of the catalyst with the monodentate chiral phosphorus ligand in Rh-catalyzed asymmetric hydrogenation. A positive nonlinear effect in the relationship of the optical purities of ligand and product was observed in the hydrogenation of dehydroamino acid derivatives. The kinetic study of hydrogenation showed that the reaction is zero order in the concentration of substrate and first order in the concentration of Rh catalyst and the hydrogenation pressure. The rate of hydrogenation decreased when the Rh/L ratio changed from 1:1 to 1:4. 相似文献
139.
The synthesis of norvancomycin (NVan)-capped silver nanoparticles (Ag@NVan) and their notable in vitro antibacterial activities against E. coli, a Gram-negative bacterial strain (GNB), are reported here. Mercaptoacetic acid-stabilized spherical silver nanoparticles
with a diameter of 16±4 nm are prepared by a simple chemical reaction. The formation process of the silver nanoparticles is
investigated by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). NVan is then grafted to the terminal
carboxyl of the mercaptoacetic acid in the presence of N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDAC). The TEM images of single bacteria treated with Ag@NVan show that plenty of Ag@NVan
aggregate in the cell wall of E. coli. A possible antibacterial mechanism is proposed that silver nanoparticles may help destroy the stability of the outer membrane
of E. coli, which makes NVan easier to bind to the nether part of the peptidoglycan structure. The antibacterial activities of silver
nanoparticles on their own, together with the rigid polyvalent interaction between Ag@NVan and cell wall, enables Ag@NVan
to be an effective inhibitor of GNB. This kind of bionanocomposites might be used as novel bactericidal materials and we also
provide an effective synthesis method for preparing functional bioconjugated nanoparticles here.
Supported by the National Natural Science Foundation of China (Grant No. 50373036) and Fok Ying Tung Education Foundation
(Grant No. J20040212) 相似文献
140.
A new thioether-rich ligand with a conjugated dienyne backbone and its fluorescent Ag(I) coordination networks have been synthesized and characterized by single crystal X-ray diffraction studies, which reveal that the supramolecular architectures of the networks contain assembled helicates with thioether sites. 相似文献