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91.
粘度法研究壳聚糖对外加盐的敏感性 总被引:11,自引:0,他引:11
聚电解质的特性粘度对外加盐的响应是反映聚电解质对外加盐敏感性的一个重要特征,通过分别测定壳聚糖在不同小分子强电解质(NaCl、KCl、CaCl2、BaCl2)和相同小分子强电解质(NaCl)但不同离子强度的稀溶液粘度,得到:(1)壳聚糖特性粘度与外加盐的离子强度的平方根的倒数成正比;(2)不同小分子强电解质中阳离子对壳聚糖特性粘度的影响次序是Na+>K+>Ba2+>Ca2+.同时,测算了壳聚糖在不同外加盐浓度中的Mark Houwink方程参数α,发现其值皆大于05,得到了壳聚糖分子链的僵硬性参数B的值为0074,揭示了壳聚糖具有较大的分子链刚性和抗盐性能. 相似文献
92.
93.
The primary goal with this work is to create electrically conductive cellulose fibres, this has been done to explore possible new applications for fibre based material. This research uses various methods to create polyelectrolyte multilayers (PEMs) on bleached softwood fibres and on SiO2 model surfaces, by sequentially treating these materials with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) and poly(allyl amine) (PAH). Paper sheets were then produced from the PEM-modified pulp and evaluated in terms of tensile strength, adsorbed amount of polymer, and electrical conductivity. To evaluate the influence of fibre charge on the measured paper properties, pulps of two different initial fibre charge densities were prepared via carboxymethylation. Because of the bluish colour of PEDOT:PSS, the build-up of PEM could be easily followed, since the fibres grew increasingly darker blue throughout the modification sequence. The conductivity of the fibre network increased by 2−3 orders of magnitude when the pulp of a higher fibre charge density was used. This suggests that it is more important to create a fibrous network with a high fibre-fibre joint strength and a large total joined area in the sheet rather than to maximize the adsorbed amount of PEDOT:PSS. A difference in conductivity could also be noted depending on the polyelectrolyte adsorbed in the outer layer, PAH lowered the conductivity compared to PEDOT:PSS. Evaluating the mechanical properties revealed that the use of PEDOT:PSS reduces the tensile strength of the paper. When five double layers had been adsorbed onto the carboxymethylated sample in which PEDOT:PSS formed the outer layer, calculations indicated a 25% decrease in tensile strength compared to that of reference material without PEMs. ESEM studies indicate that PEM treatment produces a significantly changed and somewhat smoother fibre surface. 相似文献
94.
Ultrathin multilayer films of the wheel-shaped molybdenum polyoxometalate cluster (Mo38)n and poly(allylamine hydrochloride)(PAH) have been prepared by the layer-by-layer (LbL) self-assembly method. The ((Mo38)n/PAH)m multilayer films have been characterized by X-ray photoelectron spectra (XPS) and atomic force microscopy (AFM). UV-VIS measurements reveal regular film growth with each (Mo38)n adsorption. The electrochemistry behavior of the film at room temperature was investigated. 相似文献
95.
聚电解质中电活性物质氧化还原反应机理的现场显微红外光谱电化学研究 总被引:1,自引:0,他引:1
用现场显微红外光谱电化学方法研究了几种电活性物质,包括无机盐、有机物、无机聚合物微粒在聚电解质中的氧化还原反应及其机理。 相似文献
96.
The shear flow of dilute polyelectrolyte solutions bounded by either neutral or repulsive walls is modeled using a nonlinear
dumbbell with conformation-dependent friction. Assuming that the configurational probability density function depends on the
internal coordinates (r) and the distance of the center of mass of the molecule to the walls, coupled differential equations for the tensor moments
<rr> are obtained. Coulombic repulsion between beads is considered to simulate the charge repulsion between ionized sites distributed
along the backbone of a real polyelectrolyte. The repulsive interaction between the polyelectrolyte molecule and the charged
walls is that of the DLVO model and the molecule is considered to be a charged sphere. Numerical solutions for the components
of the tensor <rr> are worked out with the preaverage approach, and only when neutral walls considered are exact solutions obtained. Viscosity
results show that in the limit of very wide channels, the corresponding viscosity in the bulk is obtained. The wall repulsion
on the charged molecules produces migration of molecules towards the center of the channel resulting in a depleted layer with
lower viscosity next to the walls. The calculated slip phenomenon using the method employed by Grisafi and Brunn is dependent
on the beads repulsion and the shear rate. The slip velocity obtained with the Mooney method shows similarities with available
experimental results for polyelectrolyte solutions. Birefringence calculations are performed in narrow and wide channels for
different bead repulsions, with interesting results for both flexible and rigid molecules.
Received: 26 September 1998 Accepted in revised form: 11 March 1999 相似文献
97.
本文采用原子转移自由基聚合法(ATRP), 设计合成了具有双温度响应性质的新型糖聚合物, 并对其在水溶液中的胶束化行为进行了动态光散射研究. 结果表明, 该系列糖聚合物具有双温度响应区间, 并且在水中形成表面呈正电性的胶束, 因此可望将其作为带负电的生物大分子(如单链DNA等)的新型载体. 相似文献
98.
Subrata Kundu Hong Liang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,330(2-3):143-150
‘Aggregates’ of monodispersed gold nanoparticles were synthesized for the first time in large quantities. Those particles were made in presence or in absence of gold seed in a polyelectrolyte solution using microwave heating for about 30–60 s. The average diameters of the particles calculated from TEM and SEM analysis were 22 ± 2 nm. Our analysis found that the polyelectrolyte acted as a reducing as well as a stabilizing agent. It controlled the growth of particles by aligning them on the polymeric chain and the nanoparticles were subsequently self-assembled to form an ‘aggregate’ structure. The synthetic procedure is very fast and the particles are stable for at least 6 months under ambient conditions. 相似文献
99.
Correlations between structural properties and phase behavior of polyelectrolyte solutions were discussed along the line of the work reported by Châtellier and Joanny [Joanny JF, Châtellier X. J Phys France II 1996;6:1669]. A multicomponent system made of polyions, salt ions and counterions was considered under poor solvent conditions. Unlike this reference, partial structure factors were derived from the celebrated Zimm’s formula written in the matrix form including the effects of finite chain length. These effects were found to generate significant shifts in phase diagrams and qualitative changes in structural properties. The presence of a charged solid surface was briefly discussed. Here also, the phase diagram was found to shift with an increasing amount as the polyion chain length decreased. 相似文献
100.
John Erik Wong Akhilesh Krishnakumar Gaharwar Detlef Müller-Schulte Dhirendra Bahadur Walter Richtering 《Journal of magnetism and magnetic materials》2007
We describe the surface modification of magnetic nanoparticles (MNPs), the coverage of poly(N-isopropylacrylamide) (PNiPAM) microgel with the MNPs and the inductive heating of these carriers. PNiPAM surface itself was modified using the layer-by-layer (LbL) assembly of polyelectrolytes to facilitate the deposition of surface-modified MNPs. One advantage of this concept is it allows the tuning of the magnetic and thermoresponsive properties of individual components (nanoparticles and microgels) separately before assembling them. Characterisations of the hybrid core–shell are discussed. In particular, it is shown that (i) each layer is successfully deposited and, more importantly, (ii) the coated microgel retains its thermoresponsive and magnetic behaviour. 相似文献