全文获取类型
收费全文 | 129篇 |
免费 | 0篇 |
专业分类
化学 | 71篇 |
晶体学 | 3篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 43篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 10 毫秒
111.
We report measurements on the electrical conductivity, optical absorption, electron spin resonance, Raman spectrum and electron diffraction of a set of a-Si films vaccum deposited at room temperature. As revealed by absorption at about 10 μm some of the films grown at deposition rates of about 0.4 Å/sec contain considerable amounts of oxygen. All the properties, except Raman spectra and electron diffraction, are found to vary strongly with the deposition rate and the background pressure during evaporation. Qualitatively, these variations show significant correlations. For instance, if the electrical conductivity is higher so is the spin density, the optical absorption and the low-frequency refractive index. Also, increasing oxygen content leads to lower conductivity. In addition, we have tried to establish a rough quantitative relation between the shift in the optical gap and the change in the spin density by connecting each of these changes to the variation in the low-frequency refractive index. The temperature dependence of the electrical conductivity was also measured and it was found that below about 150 K the data are consistent with recent theoretical predictions, i.e., log σ exhibits a ( dependence. 相似文献
112.
R. P. Bhagat 《Colloid and polymer science》2001,279(1):33-38
This article describes the adsorption of sodium dodecyl benzene sulfonate, an anionic surfactant, on a hematite surface and
that when the surface is preadsorbed with polyacrylamide. The adsorption of surfactant on a hematite surface has been studied
through equilibration and during kinetics measurements at three pH levels, viz. 4.0, 7.0, 8.9. The surfactant adsorbs strongly
on the hematite surface. The adsorption density at equilibrium as well as the rate of adsorption are dependent on the suspension
pH. The maximum adsorption density has been observed at pH 4, which reflects strong adsorption of negatively charged sulfonate
ions on the oppositely charged Fe2O3 surface (point of zero charge, 6.4). The adsorption density reaches its equilibrium value sooner in the case of an alkaline
suspension and later in the case of acidic pH. The polymer surfactant interaction has been noticed in the present study and
is also a function of pH. The hematite mineral when preadsorbed with the polymer draws fewer of the surfactant molecules at
lower surface coverage (during the initial period of the kinetics measurement) irrespective of the pH. When the adsorption
of the surfactant reaches a value which is near the equilibrium one, the pH effect is evident. In the case of acidic pH, the
surfactant adsorbs more on the hematite surface when preadsorbed with the polymer compared to the bare surface. In the case
of neutral or alkaline pH, however, the density of surfactant adsorption remains lower throughout the kinetics measurement
when the surface is preadsorbed with the flocculant compared to the bare surface. The particles also remain flocculated till
the end of the experiment, whereas at pH 4 the particles are deflocculated. In addition to pH, the electrostatic nature of
the adsorbent and the presence of anionic surfactant have an influence on the flocculation–deflocculation phenomena. The polymer–surfactant
interaction has been schematically represented. The surfactant is bound with polymeric chains as a combination of its monomeric
form as well as in the form of association in the case of acidic media and in competition with polymer in the case of alkaline
media.
Received: 18 April 2000/Accepted: 2 August 2000 相似文献
113.
Rao AV Bhagat SD Hirashima H Pajonk GM 《Journal of colloid and interface science》2006,300(1):279-285
The experimental results on the synthesis of flexible and superhydrophobic silica aerogels using methyltrimethoxysilane (MTMS) precursor by a two-step (acid-base) sol-gel process followed by the supercritical drying, are reported. The effects of various sol-gel parameters on the flexibility of the aerogels have been investigated. The aerogels of different densities were obtained by varying the molar ratio of MeOH/MTMS (S) from 14 to 35, with lower densities for larger S values. It has been observed that the Young's modulus (Y) decreased from 14.11 x 10(4) to 3.43 x 10(4) N/m(2) with the decrease in the density of the aerogels from 100 to 40 kg/m(3). Simultaneously, the aerogels are superhydrophobic with a contact angle as high as 164 degrees . The superhydrophobic aerogels are thermally stable up to a temperature of 530 K, above which they become hydrophilic. The aerogels have been characterized by bulk density, percentage volume shrinkage, and porosity measurements. The microstructures of the aerogels have been studied using the transmission electron microscopy (TEM). The Young's modulus of the aerogels has been determined by an uniaxial compression test. The variation of physical properties of the aerogels has been explained by taking into consideration the hydrolysis, condensation reactions, the resulting colloidal clusters and their network formation. 相似文献
114.
Bhagat Kavita Singh Jatinder V. Pagare Piyusha P. Kumar Nitish Sharma Anchal Kaur Gurinder Kinarivala Nihar Gandu Srinivasa Singh Harbinder Sharma Sahil Bedi Preet Mohinder S. 《Molecular diversity》2021,25(1):551-601
Molecular Diversity - GABA (γ-amino butyric acid) is an important inhibitory neurotransmitter in the central nervous system. Attenuation of GABAergic neurotransmission plays an important role... 相似文献
115.
Membranes for preconcentration of molecular iodine were developed by two different routes: (i) UV-grafting of 1-vinyl-2-pyrrolidone in the pores of microporous poly(propylene) host membrane (grafted membrane), and (ii) physical immobilization of preformed poly(vinylpyrrolidone) (PVP) in a plasticized cellulose triacetate matrix to form the polymer inclusion membrane (PVP-PIM). The UV-grafted PVP-membrane was found to be hydrophilic (water uptake capacity = 166 wt.%), while the PVP-PIM was found to be highly hydrophobic (≈2 wt.%). PVP-PIM was found to uptake only I2 from aqueous sample whereas I2 and I3− were sorbed in the grafted membrane. This selectivity of PVP-PIM towards I2 was attributed to its hydrophobicity that allows only neutral I2 to interact with PVP in the membrane matrix. Thus, the selective preconcentration and quantitative determination of I2 in aqueous sample was carried out using PVP-PIM. As PVP-PIM was optically transparent, the characteristic absorbance of PVP–I2 complex (λmax = 361 nm) could be used for quantitative determination of I2 in the membrane. The instrumental neutron activation analysis (INAA) of the I2-loaded PIM samples indicated that 82% could be sorbed into the PIM samples from the solution within 10 min of equilibration time. This membrane was applied to I2 determinations in the samples of 131I radiotracer. The concentration level of iodine species in these samples were in sub-ppb level. Therefore, these samples were ideal for testing the preconcentration efficiency of the membrane towards I2 by monitoring the radioactivity of 131I. The amounts of I2 in the aqueous samples were standardized by conventional solvent extraction of I2 with the chloroform for validating the preconcentration efficiency of PVP-PIM. The detection limit of I2 in aqueous samples by INAA hyphenated with PVP-PIM was found to be 0.3 ppb for a sample size of 25 mL. 相似文献
116.
In this paper, we introduce a new and simple method of patterning polydimethylsiloxane (PDMS) directly using benzophenone as a photoinitiator. The photodefinable PDMS mixture (photoPDMS) is positive-acting and only sensitive to light below 365 nm, permitting processing under normal ambient light. Features of the order of 100 microm, which are sufficiently small for most microfluidic applications, were successfully fabricated using this novel process. A parametric study of process parameters was performed to optimize the fabrication. As a demonstration, microfluidic channels of varying dimensions were successfully fabricated using this process and experimentally characterized using fluorescence microscopy. To further demonstrate photoPDMS potential, thin (<30 microm) free-standing films with through patterns were fabricated and successfully used as shadow masks. The photoPDMS process completely eliminates the need for a master, permits processing under normal ambient light conditions, and makes fabrication fast and simple. This process for rapid prototyping of low-cost, disposable LOCs can be accomplished without cleanroom facilities and thus can be employed for a wide range of applications. 相似文献
117.
118.
Field induced microwave absorption is recorded at low fields (<20mT) in a high Tc ceramic superconductor (Bi,Pb)---Sr---Ca---Cu---O, after cooling in zero field to 54,77 and 90 K at 9.9 GHz and to 77K at 36.4 GHz. The results are discussed in conjunction with the dc magnetization data obtained on the same sample. It is argued that the observed features do not follow the predictions of the flux flow model while they give qualitative evidence in support of the resistively shunted Josephson junction model. 相似文献
119.
We have studied the uniform mode ferromagnetic resonance in the amorphous systems Metglass 28226A, 2826B, 2826 over the temperature range 77–430 K. The data have been analysed in terms of the Gilbert Equation. The g-values are very similar to those of crystalline permalloy. The relaxation parameters λ, are of the order of 108 s?1 and exhibit an interesting temperature dependence. In particular, for is simply proportional to the static saturation magnetization Ms. The present results are compared with those obtained on crystalline samples of the 3-d transition metals and their alloys. 相似文献
120.
Hall effect measurements on the ferromagnetic amorphous materials, Metglas 2826 and 2826B, indicate that they are rather similar to crystalline soft magnetic materials. The extra-ordinary Hall coefficient Rs is found to be 1.4 × 104?2 (m3/As), where, ?, is the electrical resistivity, and is in reasonable agreement with the predictions of theory. On the other hand, though unexpected, the ordinary Hall coefficient in all the amorphous alloys we have studied turns out to be of the order of 7 × 10?10 (m3/As). 相似文献