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101.
A novel fluorescence quenching method for the determination of cationic surfactants (CS), specifically cetyltrimethylammonium
bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and cetylpyridinium chloride (CPC), has been developed using water-soluble
luminescent CdTe quantum dots (QDs) modified with thioglycolic acid (TGA). The possible interference from heavy and transition
metals (HTM) has been efficiently eliminated through simple sample treatment with mercapto cotton made in-house. Under optimum
conditions, the extent of fluorescence quenching of CdTe QDs is linearly proportional to the concentration of CS from 2.0 × 10−7 to 7.0 × 10−6 mol L−1 with a detection limit of 5.0 × 10−8 mol L−1. The relative standard deviation for 1.0 × 10−6 mol L−1 CTAB is 2.5% (n = 6). The proposed method exhibits high sensitivity and selectivity and furthermore avoided the use of toxic organic solvents
and tedious solvent extraction procedures. It has been applied to the determination of trace CS in natural river water and
commodity samples with satisfactory results.
Potential interference from heavy and transition metals is eliminated during photoluminescence detection of CS through simple
sample pre-treatment with mercapto cotton 相似文献
102.
Hong-Ting Sheng 《Journal of organometallic chemistry》2007,692(5):1118-1124
The first cationic samarium phenoxide complex, [(ArO)2Sm(DME)2][BPh4] · THF (ArO = 2,6-di-tert-butyl-4-metyl-phenoxide) (1), has been synthesized by one-electron oxidation reaction of (ArO)2Sm(THF)3 with AgBPh4 in high yield and structurally characterized. The complex 1 can be used as a single-component catalyst for the ring-opening polymerization of ε-caprolactone (ε-CL) with high activity. The activity of the complex 1 is much higher than that of the parent neutral complex (ArO)3Sm(THF)2, and is comparable to that of the divalent complex (ArO)2Sm(THF)3. A coordination-insertion polymerization mechanism was supposed according to the end-group analysis. 相似文献
103.
在阳离子表面活性剂CTMAB水溶液中,对二甲氨基苯甲酸(DMABOA)的分子内扭转电荷转移(TICT)荧光带随着胶束的形成而显着蓝移,同时伴随着TICT荧光带与正常荧光带强度比Ia/Ib和总荧光强度If的增大;而阴离子表面活性剂SLS胶束的形成并未引起TICT荧光带位置和Ia/Ib的变化,仅使If提高(较在CTMAB胶束中的小).实验发现在胶束疏水核中的TICT行为与纯有机溶剂中不同,DMABOA与CTMAB胶束的疏水相互作用和静电作用是协同的。 相似文献
104.
Cationic polymerizations of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride (TMSCl) incombination with TiCl_4 were carried out in n-hexane at 30℃. The yield of polymer was greatly increased bythe addition of TMSCl, indicating that the TMSCl/TiCl_4 combination is an efficient initiating system for PDcationic polymerization. However, the introduction of TMSCl gave rise to a drop in the molecular weight ofthe polymer. Kinetic results demonstrated that the polymerization initiated by TMSCl/TiCl_4 is 4.5 times fasterthan that induced by TiCl_4 alone. Various ethers were used to mediate the TMSCl/TiCl_4 initiating system.Adding diphenyl ether could increase both the yield and molecular weight of the polymer. Structural evidenceillustrates that the polymerization is indeed initiated by TiCl_4 in combination with HCl resulting fromhydrolysis by adventitious water. 相似文献
105.
The mixing fraction of didodecyldimethylammonium bromide (DDAB) in dodecyltrimethylammonium bromide + DDAB to produce a lamellar
liquid crystal (L
α) abruptly decreases upon addition of a small amount of m-xylene, whereas the mixing fraction becomes constant at high m-xylene content. Similar results were obtained in saturated hydrocarbon systems. It is considered that oil molecules in the
surfactant palisade layer increases the effective cross-sectional area per surfactant head group, as, whereas as is constant if the oil molecules are solubilized in the core of the liquid crystal. The volume fraction of penetrating oil
in the total solubilized oil is defined as a penetration parameter, Pe, which is calculated from small-angle X-ray scattering
data. Pe is high in the m-xylene system, whereas it is low in the n-decane system. Even in the same oil system, Pe decreases dramatically with increasing solubilization. Hence, most of the
oil added penetrates into a palisade layer at an early stage of oil addition. This causes a change in the mixing fraction
of surfactant in the L
α phase. Thereafter the oil is solubilized in the core of the bilayer with further addition of oil.
Received: 20 April 1998 Accepted: 16 July 1998 相似文献
106.
Hydrophilic magnetic polymer latexes. 1. Adsorption of magnetic iron oxide nanoparticles onto various cationic latexes 总被引:5,自引:0,他引:5
With a view to preparing monosized hydrophilic functional magnetic latex particles based on a two-step strategy using anionic
iron oxide and cationic polymer latexes, the adsorption step was systematically investigated for a better control of the subsequent
encapsulation step. The iron oxide nanoparticles were first obtained according to the classical precipitation method of ferric
and ferrous chloride salt using a concentrated sodium hydroxide solution, whereas the polystyrene (PS), P(S/N-isopropylacrylamide (NIPAM)) core–shell and PNIPAM latexes were produced via emulsion and precipitation polymerizations,
respectively. The polymer and inorganic colloids were then characterised. The adsorption of iron oxide nanoparticles onto
the three types of polymer latexes via electrostatic interaction was studied as a function of iron oxide particle concentration,
charge density and the cross-linking density of the hydrophilic layer. The maximum amounts of magnetic nanoparticles adsorbed
onto the various latexes were found to increase in the following order: PS < P(S/NIPAM) < P(NIPAM). This significant difference
is discussed by taking into account the charge distribution in the hydrogel layer and diffusion phenomena inside the cross-linked
hydrophilic shell.
Received: 28 December 1998 Accepted in revised form: 15 April 1999 相似文献
107.
The effects of complex formation between sodium dodecylsulfate (SDS) and the positively charged (3-(2-methylpropionamide)propyl)trimethyl-ammonium
chloride-acrylamide (MAPTAC-AM) copolymer have been studied in dilute and semidilute aqueous solution in the presence of 10 mM
NaCl. Two different charge densities of the copolymer have been used in the study: 0.31 and 0.66, corresponding to the proportion
of MAPTAC units. Dynamic light scattering (DLS) and rheometry (static low-shear and capillary viscometry) have been performed
on the systems at different charge ratios, i.e., SDS/MAPTAC molar ratios, r. Regarding the phase behavior, the maximum binding ratio prior to precipitation differs between the copolymers. A 1.0% w/v
solution of SDS/31% MAPTAC-AM is soluble at r = 0.4 , while an SDS/66% MAPTAC-AM solution of 1.0% w/v shows phase separation at this ratio. With excess surfactant, the
complex in the former system is resolubilized at r=2.0, whereas the latter system is still phase-separated at r=5.0. DLS results show that, for both copolymers, the hydrodynamic radius, R
h, of the single-chain copolymer-surfactant complex decreases as a function of r, but then increases slightly prior to phase separation. The corresponding hydrodynamic virial coefficient, k
D, changes in the same manner as R
h. The light-scattering data also show that the formation of larger structures is promoted as the polymer concentration is
increased from 0.2 to 1.0% w/v. This is shown by the increase in the relative aggregate-to-single coil peak areas in the relaxation
time distributions. Both systems have this common trend. The results from rheological measurements support the results from
DLS. A reduction in intrinsic viscosity, [η], is observed on increasing r up to phase separation. The major part of the static low-shear measurements showed Newtonian behavior for both systems at
different copolymer concentrations (27.6–138 mM), and at different r. These systems, partially ionic polymer/oppositely charged surfactant, present very interesting rheological behavior at relatively
high polymer concentrations and at low r values. Their behavior is similar to those of hydrophobically modified polyelectrolytes.
Received: 17 June 1998 Accepted: 12 August 1998 相似文献
108.
本文利用红外光解离光谱研究了一价钴阳离子与二氧化碳之间的相互作用. 通过密度泛函理论计算得到[Co(CO2)n]+团簇的几何结构,并且模拟了它们的振动光谱与实验数值进行比较. 研究结果表明,在[Co(CO2)n]+(n=2∽6)团簇中,钴阳离子通过电四极矩静电作用以端点结合的方式与二氧化碳中的氧原子结合在一起. 团簇的红外光谱都集中在二氧化碳反对称伸缩的波数附近,并且随着团簇尺寸的变化出现蓝移,最后把[Co(CO2)n]+的红外光解离光谱与稀有气体贴附的[Co(CO2)n]+-Ar的红外光解离光谱进行了比较. 相似文献
109.
2-Methacryloyloxy ethyl trimethyl ammonium chloride (TMA) is a potent polymeric plasma DNA (pDNA) carrier. The present study shows that TMA/pDNA polyplexes could be internalized into cells efficiently, but could not mediate gene transfection on its own. The transfection process of TMA/pDNA polyplexes is turned on only when ultrasound (US) was applied 4–8 h after incubating TMA/pDNA polyplexes with target cells (with a gene expression 1000 times that of the immediate US group). US is a widely used physical method for gene delivery; its transfection efficiency can be significantly enhanced when combined with cationic polymer vectors. Traditionally, US is given simultaneously with genetic materials, carriers and microbubbles to exert maximal efficacy. The unique on-off phenomenon of TMA/pDNA polyplexes, controlled by US exposure, was found to relate to the endosomal escape effect of US since the polyplexes colocalized well with the lysosome marker if no US was given or was given at inappropriate times. The proposed delivery system using US and TMA carriers has potential in many pharmaceutical applications requiring precise temporal and spatial release control. 相似文献
110.