全文获取类型
收费全文 | 345篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 205篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 35篇 |
物理学 | 117篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 19篇 |
2012年 | 26篇 |
2011年 | 21篇 |
2010年 | 20篇 |
2009年 | 31篇 |
2008年 | 28篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有360条查询结果,搜索用时 15 毫秒
41.
Nano titanium dioxide (nTiO2), generally considered to be toxicologically inert, is manufactured in large quantities and extensively applied in consumer products. The small size and large surface area endow them with an active group or intrinsic toxicity. Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of (bio) chemical applications. One of the great advantages of this technique is its ability to provide information on the concentration, structure and interaction of biochemical molecules in their microenvironments within intact cells and tissues, non-destructively. Zebrafish (Danio rerio), one of the most important vertebrate model organisms used in developmental biology, are increasingly used in biomedical research, particularly as a model of human disease. In the present work, an attempt is made to study the effect of titanium dioxide, both nano and bulk, on the microenvironment of the liver tissues of Zebrafish using FT-Raman spectroscopy. The results of the present study suggest that TiO2 exposure demonstrate a marked influence on the microenvironments of the liver tissues of Zebrafish. A shift to a higher wavenumber and an increase in the intensity of the band at ∼1087 cm−1 in the TiO2 exposed tissues suggest that some of the conformational changes resulting from the alkali recovery process takes place due to TiO2 exposure. The decreased intensity ratio (I3220/I3400) observed in the titanium-exposed tissues suggests a decreased water domain size, which could be interpreted in terms of weaker hydrogen-bonded molecular species of water in the TiO2 exposed tissues. The observed shift of COO− bands to higher frequencies shows the disruption of salt bridges as a result of a change in the oppositely charged partners and due to the enhanced random coil conformation. The variation in the intensity ratio of the tyrosyl doublet (I858/I825) indicates variation in the hydrogen bonding of the phenolic hydroxyl group due to TiO2 exposure. The results further suggest that the microenvironments are greatly altered due to titanium nano exposure when compared to titanium bulk. In conclusion, the results indicate that FT-Raman spectroscopy might be a useful tool for rapid assessment of nano particle biological interactions. 相似文献
42.
Reinhardt A Williamson AJ Doye JP Carrete J Varela LM Louis AA 《The Journal of chemical physics》2011,134(10):104905
In patchy particle systems where there is a competition between the self-assembly of finite clusters and liquid-vapor phase separation, re-entrant phase behavior can be observed, with the system passing from a monomeric vapor phase to a region of liquid-vapor phase coexistence and then to a vapor phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of re-entrance. However, for the most physically reasonable parameter values of the model, this behavior is restricted to a certain range of density, with phase separation still persisting at high densities. 相似文献
43.
By means of in situ IR spectroscopy we investigate the effect of dissolved alkali cations on the electro-oxidation of ethylene glycol on platinum in alkaline media. The results revealed that the increase in the oxidation currents (Li(+) < Na(+) < K(+)) is reflected in the increase in the ratio between carbonate and oxalate produced. 相似文献
44.
It is shown that charged fluid distributions, matched to the Reissner-Nordström metric, may posses finite self-energy in the point particle limit if negative energy densities are allowed and the appropriate definition of bare mass is used. Several models are analyzed to illustrate the point.On leave at: Area de Fisica Teorica, Facultad de Ciencias, Universidad de Salamanca, Salamanca 37008, Spain. 相似文献
45.
46.
R. Aguiar F. Sánchez C. Ferrater M. Varela 《Applied Physics A: Materials Science & Processing》1997,65(4-5):429-436
3 (100) single crystal substrates have been investigated. Poorly absorbed KrF irradiation leads to localized, deep, and unstable
damage on the crystal surfaces. By contrast ArF has been found to induce well-localized roughness and microcracks on LaAlO3(100) surfaces at fluences between 0.2 and 1.8 J/cm2. The material emission threshold was estimated at around 0.5 J/cm2 and cracks appeared above 1.4 J/cm2. The substrate surface state determines YBa2Cu3O7-x film growth, leading to morphological changes that have been related to a decrease in adatom mobility on the substrate. The
most striking feature is the drastic reduction in YBa2Cu3O7-x outgrowth density inside the irradiated areas. Irradiation has little effect on film crystalline properties. The main effect
on the electrical properties can be restricted to a decrease of critical current density up to a factor of 104, but such an important decrease is only observed in the most intensively irradiated substrates.
Received: 18 November 1996/Accepted: 12 June 1997 相似文献
47.
The nonohmic electrical features of (Ca1/4,Cu3/4)TiO3 perovskite ceramics, which have very strong gigantic dielectric is believed originate from potential barriers at the grain boundaries. In the present study, we used the admittance and impedance spectroscopy technique to investigate (Ca1/4,Cu3/4)TiO3 perovskite ceramics with low nonohmic electrical properties. The study was conducted under two different conditions: on as-sintered ceramics and on ceramics thermally treated in an oxygen-rich atmosphere. The results confirm that thermal treatment in oxygen-rich atmospheres influence the nonohmic properties. Annealing at oxygen-rich atmospheres improve the nonohmic behavior and annealing at oxygen-poor atmospheres decrease the nonohmic properties, a behavior already reported for common metal oxide nonohmic devices and here firstly evidenced for the (Ca1/4,Cu3/4)TiO3 perovskite related materials. The results show that oxygen also influences the capacitance values at low frequencies, a behavior that is indicative of the Schottky-type nature of the potential barrier. 相似文献
48.
M. C. Abreu M. Alimi C. Baglin A. Baldit G. P. Barreira M. Bedjidian P. Bordalo S. Borenstein J. Britz A. Bussiere P. Busson A. Casaca R. Cases J. Castor C. Charlot B. Chaurand D. Contardo E. Descroix A. Devaux J. Fargeix X. Felgeyrolles P. Force L. Fredj J. M. Gago C. Gerschel P. Gomes P. Gorodetzky J. Y. Grossiord A. Guichard J. P. Guillaud R. Haroutunian L. Kluberg L. Kraus G. Landaud I. Linck C. Louren?o A. Maio L. Peralta M. Pimenta J. R. Pizzi C. Racca S. Ramos A. Romana R. Salmeron A. Sinquin P. Sonderegger J. Varela NA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(1):129-133
The like-sign dimuons copiously recorded in the NA 38 experiment both inp-U and O?U reactions at 200 GeV/nucleon are interpreted as resulting from decays of π andK mesons in comparable proportions. The ++/?? ratio is large (?1.7) and ascribed to theK + being more copiously produced than theK ?. Both the average transverse momentum and the ++/?? ratio are comparable forp-U and O?U reactions, and both increase only slightly with the transverse energyE T . 相似文献
49.
J. M. Antelo F. Arce J. L. Armesto A. Garcia-Verdugo F. J. Penedo A. Varela 《国际化学动力学杂志》1985,17(11):1231-1245
The kinetics of the chlorination of various tertiary alcoholamines by hypochlorite have been studied in alkaline media. A reaction mechanism consistent with the experimental results is put forward, and a relationship is established between the rate constants and the polar parameter (Σσ*) of the substituents. 相似文献
50.
Varela H Beta C Bonnefont A Krischer K 《Physical chemistry chemical physics : PCCP》2005,7(12):2429-2439
We report experimental results on spatiotemporal pattern formation during the oscillatory hydrogen electrooxidation reaction on a Pt ring-electrode under negative (desynchronizing) global coupling (GC). Spatially one-dimensional profiles of the interfacial potential drop along the angular direction of the ring electrode are recorded by means of a potential probe. The dynamics is investigated as a function of two control parameters, the applied voltage U and the strength of the global coupling. The latter is adjusted either by varying the distance between the working electrode (WE) and the reference electrode (RE) or by inserting a negative impedance device in series with the WE. In the absence of global coupling, uniform oscillations were destabilized by migration coupling, and electrochemical turbulence developed at large values of U (H. Varela, C. Beta, A. Bonnefont and K. Krischer, Phys. Rev. Lett., 2005, 94, 174104; ). Already low global coupling strengths sufficed to suppress turbulence. Instead, regular two-phase clusters formed. At higher coupling strength, a second type of two-phase cluster was observed as well as two types of irregular cluster patterns, which were connected with an irregular motion of the cluster boundaries and the emergence and disappearance of clusters through splitting and merging of the boundaries, respectively. Upon increasing the coupling strength even further, five-phase clusters were stabilized and at the highest coupling strength applied the cluster patterns transformed into strongly modulated pulses. The two types of two-phase clusters and the five-phase clusters are analyzed employing several signal processing techniques. 相似文献