全文获取类型
收费全文 | 322篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 257篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 8篇 |
物理学 | 72篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 19篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 22篇 |
2017年 | 17篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 18篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有344条查询结果,搜索用时 15 毫秒
101.
Flaminia Cesare Marincola Ada Virno Antonio Randazzo Francesca Mocci Giuseppe Saba Adolfo Lai 《Magnetic resonance in chemistry : MRC》2009,47(12):1036-1042
A comparative study of the competitive cation exchange between the alkali metal ions K+, Rb+, and Cs+ and the Na+ ions bound to the dimeric quadruplex [d(G4T4G4)]2 was performed in aqueous solution by a combined use of the 23Na and 1H NMR spectroscopy. The titration data confirm the different binding affinities of these ions for the G‐quadruplex and, in particular, major differences in the behavior of Cs+ as compared to the other ions were found. Accordingly, Cs+ competes with Na+ only for the binding sites at the quadruplex surface (primarily phosphate groups), while K+ and Rb+ are also able to replace sodium ions located inside the quadruplex. Furthermore, the 1H NMR results relative to the CsCl titration evidence a close approach of Cs+ ions to the phosphate groups in the narrow groove of [d(G4T4G4)]2. Based on a three‐site exchange model, the 23Na NMR relaxation data lead to an estimate of the relative binding affinity of Cs+ versus Na+ for the quadruplex surface of 0.5 at 298 K. Comparing this value to those reported in the literature for the surface of the G‐quadruplex formed by 5′‐guanosinemonophosphate and for the surface of double‐helical DNA suggests that topology factors may have an important influence on the cation affinity for the phosphate groups on DNA. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
102.
Shin Y Saba M Pasquini TA Ketterle W Pritchard DE Leanhardt AE 《Physical review letters》2004,92(5):050405
A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein condensates coherently split by deforming an optical single-well potential into a double-well potential. The relative phase between the two condensates was determined from the spatial phase of the matter wave interference pattern formed upon releasing the condensates from the separated potential wells. Coherent phase evolution was observed for condensates held separated by 13 microm for up to 5 ms and was controlled by applying ac Stark shift potentials to either of the two separated condensates. 相似文献
103.
Kundermann S Saba M Ciuti C Guillet T Oesterle U Staehli JL Deveaud B 《Physical review letters》2003,91(10):107402
In a pump-probe experiment, we have been able to control, with phase-locked probe pulses, the ultrafast nonlinear optical emission of a semiconductor microcavity, arising from polariton parametric amplification. This evidences the coherence of the polariton population near k=0, even for delays much longer than the pulse width. The control of a large population at k=0 is possible although the probe pulses are much weaker than the large polarization they control. With rising pump power the dynamics of the scattering get faster. Just above threshold the parametric scattering process shows unexpected long coherence times, whereas when pump power is risen the contrast decays due to a significant pump reservoir depletion. The weak pulses at normal incidence control the whole angular emission pattern of the microcavity. 相似文献
104.
Gary Chartrand Elzbieta B. Jarrett Farrokh Saba Ebrahim Salehi Ping Zhang 《Czechoslovak Mathematical Journal》2001,51(2):351-361
For a nontrivial connected graph F, the F-degree of a vertex in a graph G is the number of copies of F in G containing . A graph G is F-continuous (or F-degree continuous) if the F-degrees of every two adjacent vertices of G differ by at most 1. All P3-continuous graphs are determined. It is observed that if G is a nontrivial connected graph that is F-continuous for all nontrivial connected graphs F, then either G is regular or G is a path. In the case of a 2-connected graph F, however, there always exists a regular graph that is not F-continuous. It is also shown that for every graph H and every 2-connected graph F, there exists an F-continuous graph G containing H as an induced subgraph. 相似文献
105.
Archana Gupta Parag Agarwal Saba Bee Poonam Tandon V. D. Gupta 《Polymer Science Series A》2011,53(5):375-384
Polyvinylidene fluoride (PVDF) is a polymer of industrial importance, mainly due to its piezoelectric and pyroelectric properties.
A comprehensive study of the normal modes and their dispersion in PVDF (β-form) has been reported in the reduced zone scheme
using Wilson’s GF matrix method as modified by Higgs. A Urey-Bradley force field has been used. The evaluation of normal modes and their dispersion
has been taken to logical conclusion by calculating the heat capacity as a function of temperature. The extent of agreement
with the experimental data supports the potential field. Characteristic features of the dispersion curves such as repulsion
and exchange of character have also been discussed. 相似文献
106.
Green and effective route for the synthesis of monodispersed palladium nanoparticles using herbal tea extract (Stachys lavandulifolia) as reductant,stabilizer and capping agent,and their application as homogeneous and reusable catalyst in Suzuki coupling reactions in water
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hojat Veisi Ramin Ghorbani‐Vaghei Saba Hemmati Majid Haji Aliani Turan Ozturk 《应用有机金属化学》2015,29(1):26-32
A simple and eco‐friendly procedure has been devised for the green synthesis of palladium nanoparticles, using the aqueous extract of herbal tea (Stachys lavandulifolia), a renewable and nontoxic natural phyto‐exudate. The water‐soluble components of the extract act as reducing agent and stabilizer. This green route does not require a surfactant or capping agent for the growth of palladium nanoparticles. The generated nanoparticles were analysed using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray analysis and inductively coupled plasma. The palladium nanoparticles having spherical shape and dimensions of between 5 and 7 nm were employed as a homogeneous catalyst for Suzuki coupling reactions conducted in water under mild conditions. Good yields of products, a facile work‐up, no evidence of leached palladium from the catalyst surface and smooth recovery of the catalysis by adding ethyl acetate, which could be reused at least eight times, confirm the very good efficiency of the catalytic reaction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
107.
Muhammad Danish Rabia Ayub Butt Saba Akbar Muhammad Ashfaq Graham Smith 《Journal of chemical crystallography》2016,46(10-12):421-428
108.
109.
In this work the Hawking-Unruh effect on the quantum entanglement of bosonic field in background of a spherically symmetric black hole of Gauss-Bonnet gravity is investigated beyond the single mode approximation. The entanglement decreases due to Hawking-Unruh effect. However, it has been shown that the dimensions of space time, Gauss-Bonnet term and the parameter β of initial entangled state would be influenced on this degradation. In our investigation, we consider the accelerated observer either near or far from the event horizon and inspect entanglement degradation for them. The mutual information of this bosonic system is also calculated in beyond the single mode approximation and we show that the mutual information will have different behavior when the Hawking temperature increases. 相似文献
110.
The effects of the type and content of comonomers on the rheological properties of acrylic copolymers in 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) were explored. According to the de Gennes scaling law for solution, comparison of intrinsic viscosity and scaling analysis of the exponent in the specific viscosity‐ and relaxation time‐concentration power law indicated that solution of both polyacrylonitrile (PAN) homo‐polymer and copolymer poly(acrylonitrile‐co‐methyl acrylate) (poly(AN‐co‐MA)) in [BMIM]Cl behave in the same manner as neutral polymer in a θ‐solvent. However, [BMIM]Cl acts as a more good solvent for poly(acrylonitrile‐co‐acrylamide) (poly(AN‐co‐AM)). The dissolution and unique rheological behavior of such solutions have been attributed to the interactions between copolymer chains and [BMIM]Cl. The interactions between nitrile group (?C≡N) and 1‐butyl‐3‐methylimidazolium cation ([BMIM]+) should interrupt and break the dipolar‐dipolar interactions of PAN resulting in the subsequent dissolution of the polymer in [BMIM]Cl. Such interactions between ?C≡N and [BMIM]+ ion are still dominated by the solvating ability of poly(AN‐co‐MA) in [BMIM]Cl, even though carbonyl group (C=O) in MA repeating unit could coordinate to cation of the ionic liquid. The salvation capacity of [BMIM]Cl for poly(AN‐co‐AM) can be evidently improved due to the extra hydrogen bond interactions between ?NH2 group of AM and anion of [BMIM]Cl. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献