全文获取类型
收费全文 | 473篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 386篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 37篇 |
物理学 | 49篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 23篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 33篇 |
2011年 | 43篇 |
2010年 | 33篇 |
2009年 | 37篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 21篇 |
2005年 | 28篇 |
2004年 | 23篇 |
2003年 | 9篇 |
2002年 | 17篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有484条查询结果,搜索用时 15 毫秒
101.
Ecaterina Stela Dragan Marcela Mihai Simona Schwarz 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):213-221
Three ionic/nonionic random copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) or methyl methacrylate (MM), were used in the preparation of some polyelectrolyte complex dispersions (PCD) with two strong polycations of integral type, poly(diallyldimethylammonium chloride) (PDADMAC), and an ionene type polycation, containing 95 mol% N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA5). The novelty of the paper is that PCDs with a high colloidal stability, both before and after the complex stoichiometry, were obtained even with hydrophilic/hydrophobic polyanions, with a high titrant addition rate (TAR), a less explored parameter, which allows a fine control of PCDs aggregation level, in salt-free aqueous solutions. The characteristics of PCDs were also correlated with the polyanion average charge density and the structure of the nonionic comonomer, at a constant TAR, the polyanion with the lowest charge density leading to the highest turbidities and the lowest colloidal stabilities. A mechanism of the PCDs colloidal stabilization as a function of TAR was suggested in the paper. 相似文献
102.
Edwin A. Hernndez-Caraballo Marcela Burguera Jos L. Burguera 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2159-2165
A method for the determination of total selenium in serum samples by graphite furnace atomic absorption spectrometry was evaluated. The method involved direct introduction of 1:5 diluted serum samples (1% v/v NH4OH+0.05% w/v Triton X-100®) into transversely heated graphite tubes, and the use of 10 μg Pd+3 μg Mg(NO3)2 as chemical modifier. Optimization of the modifier mass and the atomization temperature was conducted by simultaneously varying such parameters and evaluating both the integrated absorbance and the peak height/peak area ratio. The latter allowed the selection of compromise conditions rendering good sensitivity and adequate analyte peak profiles. A characteristic mass of 49 pg and a detection limit (3s) of 6 μg 1−1 Se, corresponding to 30 μg l−1 Se in the serum sample, were obtained. The analyte addition technique was used for calibration. The accuracy was assessed by the determination of total selenium in Seronorm™ Trace Elements Serum Batch 116 (Nycomed Pharma AS). The method was applied for the determination of total selenium in ten serum samples taken from individuals with no known physical affection. The selenium concentration ranged between 79 and 147 μg l−1, with a mean value of 114±22 μg l−1. 相似文献
103.
Klepárník K Voráčová I Lišková M Přikryl J Hezinová V Foret F 《Electrophoresis》2011,32(10):1217-1223
Water-soluble CdTe quantum dots (QDs) and their conjugates with antibodies and antigenes were prepared by optimized procedures for applications in CE immunoassays. The QD size of 3.5 nm, excitation spectrum in the range of 300-500 nm, the maximum wavelength of the emission spectrum at 610 nm, quantum yield of 0.25 and luminescence lifetimes in the range of 3.6-43 ns were determined. The 0.1 M solution of TRIS/TAPS (pH 8.3) was found to be the optimum buffer for the separation of the antiovalbumin-ovalbumin immunocomplex from the free conjugates of QDs. 相似文献
104.
Angel Leiva César Saldías Alejandro Toro-Labbé Marcela Urzúa Deodato Radic 《European Polymer Journal》2009,45(11):3035-8627
Block copolymers have been extensively used in the synthesis of many types of nanoparticles, where generally are considered as stabilizer and protective agent. In this work a double function of the biodegradable triblock copolymer poly(N-vinyl-2-pyrrolidone)-b-poly(ε-caprolactone)-b-poly(N-vinyl-2-pyrrolidone), (PVP-PCL-PVP) in the gold nanoparticle-copolymer synthesis is reported.Gold-copolymer composed nanoparticles were synthesized using the triblock copolymer (PVP-PCL-PVP) and potassium tetrachloro aurate (III), both in aqueous solution. The copolymer work as both, reductant and stabilizer agent. The obtained nanoparticles were characterized by FT-IR, dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The shape and the size of the obtained nanoparticles are dependent on the copolymer/salt of gold concentration ratio used in the synthesis.To complement the experimental results about the copolymer role in the nanoparticles synthesis, computational tools were used to characterize the reactivity of the reactant species. 相似文献
105.
Abdullah Chandra Sekhar Talari Marcela A. Garcia Martinez Zanyar Movasaghi Shazza Rehman 《应用光谱学评论》2017,52(5):456-506
This article reviews some of the recent advances on FTIR spectroscopy in areas related to natural tissues and cell biology. It is an update on our previously published review on the applications of spectroscopic methods employed for the analysis of biological molecules, and summarizes some of the most widely used peak frequencies and their assignments. The aim of this review is to update and consolidate our previously published spectral database, which will help researchers in defining the chemical structure of the biological tissues introducing most of the important peaks present in the natural tissues more precisely and accurately. In spite of applying different methods, there seems to be a considerable similarity in defining the peaks of identical areas of the FTIR spectra. As a result, it is believed that preparing a unique collection of the frequencies encountered in FTIR spectroscopic studies can provide substantial help for future studies. In this article, we have included recent studies that have been reported since previous publication that will be of considerable assistance and added value to those who are focusing their research on defining chemical pathway to the progression of different diseases. 相似文献
106.
Gizele Rejane Baldo Lucas Döhler Adelia Grzybowski Marcela Tiboni Lucas Blitzkow Scremin Heidegrid Siebert Koop Mábio João Santana Luciano Morais Lião José Domingos Fontana 《Cellulose (London, England)》2014,21(4):3041-3053
The removal of residual dyes in coloured textile wastewaters is mandatory, and a significant portion of the dyes used are cationic. Textile factories mainly process cotton yarns, and 8 % of this virgin feedstock is lost as cotton dust waste (CDW). Using factorial experimental design, this dust was derivatised with monochloroacetic acid (MCAA) to produce a partially carboxymethylated cellulose (CM?-CDW) with NaOH, MCAA and isopropanol for the retention of Basic Blue 41 dye (BB 41) (column and batch), and biodegradability was investigated. The dye retention efficiency was examined with additional experiments varying the initial concentration, contact time and addition of salts. Heteronuclear multiple bonding correlation-nuclear magnetic resonance confirmed the covalent insertion of CM? groups in the cellulosic fibres. The selected matrix provided a dye sorption of 58.33 (column) and 64.50 mg/g (batch). The Langmuir isotherm was a good fit to the sorption data. The efficiency of uptake of BB 41 was predominantly dictated by the concentration of alkali in the matrix synthesis. Biodegradability by cellulases was similar when using uncharged and dye-charged matrices. The latter were fully regenerated by washing in dilute acid. Retention was proportional to the initial dye concentration and the contact time required to reach equilibrium, which was longer for higher dye concentrations. The addition of 10 mmol/l NaCl decreased BB 41 retention by 50 %. Therefore, CM?-CDW proved effective for the removal of the cationic dye BB 41 and thus represents an important alternative in the treatment of coloured textile effluents. 相似文献
107.
Durango-García CJ Jiménez-Halla JO López-Cardoso M Montiel-Palma V Muñoz-Hernández MA Merino G 《Dalton transactions (Cambridge, England : 2003)》2010,39(44):10588-10589
The iridum-gallyl complex MeIr(PCy(3))(2)(GaMe(2))(Cl*GaMe(3)) exhibits a short Ir-Ga bond length of 2.381(1)-2.389(2) ?. Theoretical calculations (ZORA BP86/TZ2P) support the presence of a Ir-Ga single bond but highlight a π orbital contribution. 相似文献
108.
Protein immobilization capacity and covalent binding coverage of pulsed plasma polymer surfaces 总被引:1,自引:0,他引:1
Yongbai Yin Daniel Bax David R. McKenzie Marcela M.M. Bilek 《Applied Surface Science》2010,256(16):4984-3733
Three carbon surfaces were deposited using pulsed plasma enhanced chemical vapour deposition method: a low and a high nitrogen-containing plasma polymer surfaces and a diamond-like carbon surface. The surfaces were analysed using both X-ray photoelectron spectroscopy (XPS) technique and the enzyme-linked immunosorbent assay (ELISA) method combining with sodium dodecyl sulphate (SDS) cleaning to investigate the capacity and covalent binding of the immobilized proteins. A good correlation was found on quantification of remaining protein after SDS cleaning using the ELISA method and the XPS technique. All surfaces had similar initial capacity of protein attachment but with large different resistance to SDS cleaning. The analysis showed that the high nitrogen-containing plasma polymer was the best biocompatible material due to its highest resistance to SDS cleaning, i.e. with the highest quantity (∼80%) of proteins bound covalently. 相似文献
109.
Menezes WG Camargo PH Oliveira MM Evans DJ Soares JF Zarbin AJ 《Journal of colloid and interface science》2006,299(1):291-296
In this work we present the utilization of the heterometallic alkoxide [FeCl{Ti(2)(OPr(i))(9)}] as the first sol-gel single-source precursor to achieve nanocomposites made of iron and titanium oxides incorporated into Porous Vycor Glass (PVG). The nanocomposites were prepared by the impregnation of the precursor in a PVG plate followed by hydrolysis reactions. Different samples were obtained by further thermal treatment of the hydrolyzed sample. The nanocomposites were characterized by UV-vis-NIR, Raman and EPR spectroscopies, XRD and TEM. The results indicate that the room-temperature hydrolyzed samples are formed by nanoparticles of FeOOH and brookite-TiO(2) embedded on a glassy matrix. After the heat treatment at temperatures above 900 degrees C, a pseudobrookite Fe(2)TiO(5) was formed. All samples present high transparency and homogeneity. The results showed here indicate that the sol-gel process using the single-source precursor [FeCl{Ti(2)(OPr(i))(9)}] should be a novel and efficient approach to the preparation of nanometric Fe/Ti oxides incorporated into a glassy matrix. 相似文献
110.
Cabrera WJ Kaempfe MA Urzúa MD Ríos HE 《Journal of colloid and interface science》2006,295(1):155-158
The effect of 1-decanol on the potentiometric response of three ion-selective electrodes to large cationic species is analyzed. The electrodes were constructed with plasticized PVC membranes. The results suggest that 1-decanol alters the ionic transport through the membrane/water interface to an extent that depends on the strength of the active ion pair. The water solubility of the cation, its molecular weight, and the size of the ion pair seem to be relevant factors in this type of behavior. The potentiometric selectivity coefficients are also dependent on the presence of 1-decanol in the membrane. These results are similar to those already described in ion-selective electrodes with membranes capable of sensing anionic benzene sulfonate-type systems. Thus, the effect of the alcohol appears to be general by affecting mainly the membrane surface polarity. 相似文献