全文获取类型
收费全文 | 112篇 |
免费 | 0篇 |
专业分类
化学 | 44篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 61篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 11篇 |
2005年 | 2篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有112条查询结果,搜索用时 15 毫秒
11.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
12.
Bongiovanni C Ferri T Poscia A Varalli M Santucci R Desideri A 《Bioelectrochemistry (Amsterdam, Netherlands)》2001,54(1):17-22
This paper describes an electrochemical biosensor for free cholesterol monitoring. The sensor is a multienzymatic electrodic system in which horseradish peroxidase and cholesterol oxidase are simultaneously immobilized within a polymeric film, on the surface of a pyrolitic graphite electrode. From voltammetric and amperometric (flow-injection) data obtained, the efficiency, reproducibility and stability of the system are discussed. Results obtained, of interest for basic and applied biochemistry, represent a first step for construction of a mediator-free biosensor with potentialities for a successful application in the biosensor area. 相似文献
13.
14.
15.
A new method is proposed here for measuring the optical constants of solids. The method is based on measuring the change of the derivative of reflectance with the angle of incidence Θ of p-polarized light for different Θ around the pseudo-Brewster angle. The accuracy of the method has been checked by determining the optical constants of some transparent and opaque materials. The method seems very sensitive to the presence of thin oxide layers and it is also expected to be useful in determining oxide thicknesses. 相似文献
16.
Summary By means of a new experimental technique based on a non-steady-state method,i.e. on the propagation properties of thermal waves, we have measured the thermal diffusivityD of a copper wire by changing properly its boundary conditions in order to ascertain whether the values ofD were independent of the surface heat losses. Temperature oscillations at the fixed frequency of 0.0121 Hz were excited at
one end of the specimen which was in nitrogen atmosphere at different pressures ranging from ∼10−2 mTorr to 220 mTorr. The temperatures of the far end of the specimen and the walls of the container had the same constant
value of 0°C, while the temperature gradient between the average value of the oscillating temperatures and this constant temperature
was changed from 2°C to 12°C for each pressure by adjusting the heater power. By operating in this way it was possible to
change either the heat losses due to conduction and convection or those due to radiation. The major cause of error came from
the uncertainty in the measurements of the phase shift between the thermal oscillations detected at the two fixed points of
the specimen which introduces in the evaluation ofD an error of about 2%. The experimental values obtained for the thermal diffusivity in these different boundary conditions
were in any case comprised within this uncertainty sinceD=(1.17±0.02) cm2s−1, in good agreement with the literature. The results so far obtained show that the experimental method has the great advantage
of giving the thermal diffusivity and, therefore, the thermal conductivity of a solid without the necessity of taking particular
care in insulating the specimen.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.
This research was supported by the Consiglio Nazionale delle Ricerche, Rome (Italy).
Some preliminary results were presented at the ?LXVII Congresso della Società Italiana di Fisica?, Pisa, October 1981. 相似文献
Riassunto Utilizzando una tecnica sperimentale che consente di determinare in fili metallici sia la diffusività termicaD sia il coefficienteμ di perdita superficiale mediante la misura diretta del ritardo di fase e dell'attenuazione di un'onda termica tra due punti fissi del campione, ci si è proposti di analizzare alcuni risultati ottenuti recentemente in un campione di rame, variando opportuamente le condizioni al contorno. In particolare, ci si è voluti assicurare che la diffusività termica non risultasse dipendente dal valore del coefficiente di perdita superficiale. Le misure sono state eseguite alla frequenza fissa di 0.0121 Hz in atmosfera di azoto, a pressioni diverse comprese tra ∼10−2 mTorr e 220 mTorr. L'estremità lontana del campione e le pareti del contenitore erano tenuti costantemente alla stessa temperatura (0°C), mentre il gradiente termico era sistematicamente variato tra 2°C e 12°C, in corrispondenza di ciascuna pressione. Operando in questo modo, si potevano variare opportunamente sia la conduzione sia l'irraggiamento del calore dalla superficie laterale del campione nel mezzo circostante. In queste misure, la causa predominante di errore viene dalla misura dello sfasamento delle due onde, che introduce nella valutazione diD un'incertezza del 2%. I valori sperimentali ottenuti nelle diverse condizioni prima ricordate risultano, in ogni caso, compresi entro i limiti di questa incertezza, poichéD=(1.17±0.02) cm2/s, in ottimo accordo con i dati della letteratura. Questo risultato dimostra pertanto che la diffusività termica, determinata con questo metodo dinamico, risulta effettivamente indipendente dalla quantità di calore transmesso dal campione nel mezzo circostante, consentendo pertanto piú agevoli determinazioni della conducibilità termica dei solidi, noti la densità ed il calore specifico.
Резюме С помощью новой экспериментальной техники, основанной на нестационарном методе, т.е. на свойствах распространения тепловых волн, мы измеряем коэффициент температуропроводностиD медного провода, посредством измения граничных условий, чтобы выяснить независимость величинD от поверхностных потерь тепла. Температурные осцилляции при фиксированной частоте 0.0121 Гц возбуждаются на одном конце образца, который помеЩен в атмосферу азота при различных давлениях в области от ∼10−2 мтор до 220 мтор. Температуры другого конца образца и стенок контейнера являются постояннюми 0°C, тогда как градиент температуры между средним значением осциллирующей темпертурой и этой постоянной температурой изменяется от 2°C до 12°C для каждого значения давления, за счет регулировки мощности нагревателя. Этот метод позволяет изменять тепловые потери, обусловленные либо проводимостью и конвекцией, либо излучением. Основная причина ошибок проистекает из неопределенности в измерениях фазового сдвига между тепловыми осцилляциями, заререгистрированными в двух фиксированных точках образца. Ошибка при измерении составляет около 2%. Экспериментальные значения, полученные для коэффициента температуропроводности при различных граничных условиях,D=(1.17±0.02) см−2с−1, хорошо согласуются с данными в литературе. Полученные результаты показывают, что предложенный экспериментальный метод обладает большим преимуществом при определении температуропроводности и, следовательно, теплопроводности твердых тел, не уделяя особого внимания изоляции образца.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.
This research was supported by the Consiglio Nazionale delle Ricerche, Rome (Italy).
Some preliminary results were presented at the ?LXVII Congresso della Società Italiana di Fisica?, Pisa, October 1981. 相似文献
17.
The 2(H)-pyran-2-one bearing electron-donating tert-butylcarbamate (BocNH-) group at the 5- position is a “chameleon” diene and undergoes efficient Diels–Alder cycloadditions with alkene dienophiles with both electron-rich and electron-deficient substituents. Cycloadditions afford the 5-substituted bicyclic lactone cycloadducts regardless of the electronic nature of the dienophile. However, cycloadditions with electronically matched electron-deficient dienophiles proceed faster than those with electronically mismatched electron-rich dienophiles. 相似文献
18.
A.R. Phani M. PassacantandoS. Santucci 《Journal of Physics and Chemistry of Solids》2002,63(3):383-392
Crack free, dense and transparent CdTiO3 thin films have been prepared by sol-gel technique using titanium butoxide and cadmium acetate. The formation of the CdTiO3 phase started from 500°C annealing temperature onwards. The complete orthorhombic structure of CdTiO3 was formed on Silicon (100) substrate at an annealing temperature of 600°C for 5 h. As the annealing temperature increased from 600 to 700°C, we have observed the cadmium silicate phase at the interface of Si and CdTiO3 phase. Structural, morphological and elemental evolution of these CdTiO3 thin films produced by sol-gel synthesis were characterised by grazing incidence X-ray diffraction (GIXRD), tapping mode atomic force microscopy (TMAFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) respectively. 相似文献
19.
Simeoni M De Luca C Picozzi S Santucci S Delley B 《The Journal of chemical physics》2005,122(21):214710
Density-functional all-electrons calculations within local-density approximation show that the two isoelectronic polymers poly(para-phenylene) and poly(para-borazylene) weakly interact with zigzag single-walled carbon nanotubes. The analysis of the electronic properties of the joint systems, both with the polymer inside and outside the nanotubes, reveals a physisorption process with small changes in band structures and densities of states with respect to the constituents. We evaluate the potential barrier arising between polymers and nanotubes. Finally, we remark a generic selectivity of poly(para-phenylene) with respect to the electronic behavior of nanotubes, leading to a change in the density of states of metallic tubules. 相似文献
20.