全文获取类型
收费全文 | 998篇 |
免费 | 21篇 |
国内免费 | 6篇 |
专业分类
化学 | 514篇 |
晶体学 | 2篇 |
力学 | 72篇 |
数学 | 225篇 |
物理学 | 212篇 |
出版年
2023年 | 8篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 20篇 |
2019年 | 24篇 |
2018年 | 19篇 |
2017年 | 21篇 |
2016年 | 53篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 52篇 |
2012年 | 68篇 |
2011年 | 87篇 |
2010年 | 49篇 |
2009年 | 43篇 |
2008年 | 60篇 |
2007年 | 69篇 |
2006年 | 45篇 |
2005年 | 41篇 |
2004年 | 40篇 |
2003年 | 42篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有1025条查询结果,搜索用时 15 毫秒
41.
42.
Valeria van Axel Castelli Antonella Dalla Cort Luigi Mandolini Valentina Pinto David N. Reinhoudt Fabrizio Ribaudo 《Supramolecular chemistry》2013,25(2-3):211-219
The complexation of the salophen-uranyl metallocleft 2 and of its half-cleft analogue 3 with enones and other carbonyl compounds was assessed in chloroform by UV-Vis titration and, occasionally, by FT-IR measurements. Complexes with receptors 2 and 3 are in all cases more stable than those with the control unsubstituted uranyl-salophen 1 , showing that in addition to the primary binding force provided by coordination of the carbonyl oxygen to the uranium, a significant driving force for complexation, typically in the range of 2-3 kcal/mol, results from van der Waals interactions of the guest with the aromatic walls. Replacement of the phenyl group in 3 with larger aromatic residues to give 4 and 5 , led to enhanced complex stabilities, due to more extended contact surfaces between host and guest. 相似文献
43.
44.
Murat Güney Selçuk Eşsiz Arif Daştan Metin Balci Ottorino De Lucchi Ertan Şahin Fabrizio Fabris 《Helvetica chimica acta》2013,96(5):941-950
Stereoisomerically pure endo‐ and exo‐7‐halo‐7‐(trimethylstannyl)benzonorcar‐3‐enes (=endo‐ and exo‐(1‐halo‐1a,2,7,7a‐tetrahydro‐1H‐cyclopropa[b]naphthalen‐1‐yl)trimethylstannane) 4 and 6 were selectively obtained by lithium? tin or magnesium? tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene‐2‐carboxylate (CuTC) produced in both cases the corresponding CS‐symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn‐ 1 , a single diastereoisomer (Schemes 5 and 6). The structure of syn‐ 1 was undoubtedly elucidated by X‐ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7). 相似文献
45.
The selective and efficient acetylation of the hemiacetal hydroxyl in the equilibrium mixture between RCl2C(OAll)OH and AllOH/RCl2CHO was achieved using the acylating system Ac2O/Et3N/dimethylaminopyridine (DMAP).
46.
47.
Giacomo Fiorin Fabrizio Marinelli José D. Faraldo-Gómez 《Journal of computational chemistry》2020,41(5):449-459
We report a methodology to calculate the free energy of a shape transformation in a lipid membrane directly from a molecular dynamics simulation. The bilayer need not be homogeneous or symmetric and can be atomically detailed or coarse grained. The method is based on a collective variable that quantifies the similarity between the membrane and a set of predefined density distributions. Enhanced sampling of this “Multi-Map” variable re-shapes the bilayer and permits the derivation of the corresponding potential of mean force. Calculated energies thus reflect the dynamic interplay of atoms and molecules, rather than postulated effects. Evaluation of deformations of different shape, amplitude, and range demonstrates that the macroscopic bending modulus assumed by the Helfrich–Canham model is increasingly unsuitable below the 100-Å scale. In this range of major biological significance, direct free-energy calculations reveal a much greater plasticity. We also quantify the stiffening effect of cholesterol on bilayers of different composition and compare with experiments. Lastly, we illustrate how this approach facilitates analysis of other solvent reorganization processes, such as hydrophobic hydration. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
48.
Massimo Tosolini Teresa Gianferrara Giuliana Mion Luca Dovigo Fabrizio Mancin 《Supramolecular chemistry》2020,32(2):91-105
ABSTRACTA new family of conjugates between the Hoechst minor groove binder and the TACN metal ion ligand connected through hydrophobic alkyl or more hydrophilic oxyethyl linkers of different length has been prepared. The linkers are connected to the convex side of the Hoechst skeleton thus forcing the TACN ligand to exit the minor groove and interact with the phosphate backbone of DNA. The conjugates preserve the binding mode of Hoechst with an affinity influenced by the nature of the linker, the more hydrophobic being the more efficient. Coordination of Cu(II) or Zn(II) poorly affect these parameters. Nevertheless, the Zn(II) complex bearing a C6 linear alkyl linker induced a modest but reproducible acceleration of the hydrolytic cleavage of DNA which can be ascribed to the ability of the conjugate to deliver the hydrolytic subunit close to the DNA phosphodiester bonds. 相似文献
49.
50.
Remilekun O. Lawal Fabrizio Donnarumma Kermit K. Murray 《Journal of mass spectrometry : JMS》2019,54(3):281-287
A 193‐nm wavelength deep ultraviolet laser was used for ambient laser ablation electrospray ionization mass spectrometry of biological samples. A pulsed ArF excimer laser was used to ablate solid samples, and the resulting plume of the desorbed material merged with charged electrospray droplets to form ions that were detected with a quadrupole time‐of‐flight mass spectrometer. Solutions containing peptide and protein standards up to 66‐kDa molecular weight were deposited on a metal target, dried, and analyzed. No fragmentation was observed from peptides and proteins as well as from the more easily fragmented vitamin B12 molecule. The mass spectra contained peaks from multiply charged ions that were identical to conventional electrospray. Deep UV laser ablation of tissue allowed detection of lipids from untreated tissue. The mechanism of ionization is postulated to involve absorption of laser energy by a fraction of the analyte molecules that act as a sacrificial matrix or by residual water in the sample. 相似文献