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391.
Poly(N‐isopropylacrylamide) (PNIPAAm)‐based microspheres were prepared by precipitation and dispersion polymerization. The effects of several reaction parameters, such as the type and concentration of the crosslinker (N,N′‐methylenebisacrylamide or ethylene dimethacrylate), medium polarity, concentration of the monomer and initiator, and polymerization temperature, on the properties were examined. The hydrogel microspheres were characterized in terms of their chemical structure, size and size distribution, and morphological and temperature‐induced swelling properties. A decrease in the particle size was observed with increasing polarity of the reaction medium or increasing concentration of poly(N‐vinylpyrrolidone) as a stabilizer in the dispersion polymerization. The higher the content was of the crosslinking agent, the lower the swelling ratio was. Too much crosslinker gave unstable dispersions. Although the solvency of the precipitation polymerization mixture controlled the PNIPAAm microsphere size in the range of 0.2–1 μm, a micrometer range was obtained in the Shellvis 50 and Kraton G 1650 stabilized dispersion polymerizations of N‐isopropylacrylamide in toluene/heptane. Typically, the particles had fairly narrow size distributions. Copolymerization with the functional glycidyl methacrylate monomer afforded microspheres with reactive oxirane groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 968–982, 2006 相似文献
392.
Eduard Feireisl Danielle Hilhorst Hana Petzeltová Peter Takáč 《Journal of Evolution Equations》2016,16(1):1-19
We consider a simple model describing the motion of a two-component mixture through a porous medium. We discuss well posedness of the associated initial-boundary value problem, in particular, with respect to the choice of boundary and far-field conditions. The existence of global-in-time solutions is proved in the ideal case when the fluid occupies the whole physical space. Finally, similar results are obtained also for the boundary value problems in the simplified 1-D geometry. 相似文献
393.
Hana Fourou Ali Zazoua Mohamed Braiek 《International journal of environmental analytical chemistry》2016,96(9):872-885
The focus of this article is the development and optimisation of a simple, sensitive, selective biosensor for the detection of heavy metals, through inhibition of β-galactosidase (β-gal) from Aspergillus oryzae after its immobilisation on an electrochemical transducer by cross-linking with glutaraldehyde. The inhibition of β-gal by Cd(II) and Cr(VI) was demonstrated by the decrease of β-gal activity monitored by the conductometric signal. Under optimal conditions, the developed voltammetric and impedimetric biosensor, based on the specific interaction of metallic ions with beta-galactosidase that increases the electron transfer of the redox probe, presented a wide range of linearity. Detection limits of 3.12 × 10–10 M (91.7 ng/L) were obtained, using both techniques, for Cr(VI). For Cd(II) detection limits were 2.85 × 10–8 M (6.95 µg/L) using EIS and 3.22 × 10–11 M (7.61 ng/L) using square wave voltammetry (SWV). 相似文献
394.
Luca Demonti Hana Tabikh Dr. Nathalie Saffon-Merceron Dr. Noel Nebra 《欧洲无机化学杂志》2023,26(19):e202300348
The synthesis of Naumann's AgI/AgIII mixed valence salt [AgI]+[AgIII(CF3)4]− ( Ag-1 ) is revisited. Ag-1 is now safely available in half gram scale upon 2e− oxidation of AgF in presence of CF3SiMe3 and ambient air. In addition to its unprecedented crystallographic characterization, the use of Ag-1 to build the novel AgI/AgIII salts [ Ag (bpy)2] -1 , [ Ag (18-crown-6)2] -1 , [ Ag -crypt-222] -1 and [ Ag (PCy3)2] -1 is herein reported, alongside their characterization by NMR, single crystal X-ray diffraction (Sc-XRD) and elemental analysis (EA). The utility of the currently affordable Ag-1 in gold(I) catalysis was demonstrated by the excellent catalytic activity displayed by [{ Au (PPh3)}2(μ-Cl)] -1 and [ Au (PPh3)] -1 in the 5-exo-dig cyclization of N-propargylbenzamide ( 2 ). These cationic AuI catalysts are accessible from (PPh3)AuCl and Ag-1 , and outperform the activity of the well-known benchmark catalyst (PPh3)AuNTf2. 相似文献
395.
Film thickness dependence of protein adsorption from blood serum and plasma onto poly(sulfobetaine)-grafted surfaces 总被引:1,自引:0,他引:1
Yang W Chen S Cheng G Vaisocherová H Xue H Li W Zhang J Jiang S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(17):9211-9214
In this work, we investigate protein adsorption from single protein solutions and complex media such as 100% blood serum and plasma onto poly(sulfobetaine methacrylate) (polySBMA)-grafted surfaces via atom transfer radical polymerization (ATRP) at varying film thicknesses. It is interesting to observe that protein adsorption exhibits a minimum at a medium film thickness. Results show that the surface with 62 nm polySBMA brushes presents the best nonfouling character in 100% blood serum and plasma although all of these surfaces are highly resistant to nonspecific protein adsorption from single fibrinogen and lysozyme solutions. Surface resistance to 100% blood serum or plasma is necessary for many applications from blood-contacting devices to drug delivery. This work provides a new in vitro evaluation standard for the application of biomaterials in vivo. 相似文献
396.
Viñas C Laromaine A Teixidor F Horáková H Langauf A Vespalec R Mata I Molins E 《Dalton transactions (Cambridge, England : 2003)》2007,(31):3369-3377
The structurally chiral [7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)](-), [](-), anion was prepared by a partial degradation reaction of 1-(2'-pyridyl)-1,2-closo-C(2)B(10)H(11). From this anion a protonated specie, H[7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)] , and a tetramethylammonium salt, [NMe(4)][7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)], [NMe(4)][] can be obtained. The (1)H{(11)B} DNMR study on in the temperature range from 298 to 203 K identified the weakly basic nitrogen atom in the pyridine ring as the proton accepting site in solid state and low temperature and revealed pronounced weakening of the nitrogen-proton interaction while the temperature increases. Capillary electrophoresis and X-ray diffraction confirmed the pyridine nitrogen atom as the proton binding site. Separation of the electrophoretically pure racemic [7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)](-) ion into two peaks by the chiral selector beta-cyclodextrine has been achieved. 相似文献
397.
Cahová H Pohl R Bednárová L Nováková K Cvacka J Hocek M 《Organic & biomolecular chemistry》2008,6(20):3657-3660
dATP derivatives bearing Br, Me or Ph groups in position 8 were prepared and tested as substrates for DNA polymerases to show that 8-Br-dATP and 8-Me-dATP were efficiently incorporated, while 8-Ph-dATP was a poor substrate due to its bulky Ph group. 相似文献
398.
Preparation and properties of magnetic nano- and microsized particles for biological and environmental separations 总被引:1,自引:0,他引:1
The paper presents a critical overview on magnetic nanoparticles and microspheres used as separation media in different fields of chemistry, biochemistry, biology, and environment protection. The preparation of most widely used magnetic iron oxides in appropriate form, their coating or encapsulation in polymer microspheres, and functionalization is discussed in the first part. In the second part, new developments in the main application areas of magnetic composite particles for separation and catalytical purposes are briefly described. They cover separations and isolations of toxic inorganic and organic ions, proteins, and other biopolymers, cells, and microorganisms. Only selected number of relevant papers could be included due to the restricted extent of the review. 相似文献
399.
400.
Hana Macková Vladimír Proks Daniel Horák Jan Kučka Miroslava Trchová 《Journal of polymer science. Part A, Polymer chemistry》2011,49(22):4820-4829
Magnetic poly(N‐propargylacrylamide) (PPRAAm) microspheres were prepared by the precipitation polymerization of N‐propargylacrylamide (PRAAm) in a toluene/propan‐2‐ol medium in the presence of magnetic nanoparticles (oleic acid‐coated Fe3O4). The effects of several polymerization parameters, including the polarity of the medium, polymerization temperature, the concentration of monomer, and the amount of magnetite (Fe3O4) in the polymerization feed, were examined. The microspheres were characterized in terms of their morphology, size, particle‐size distribution, and iron content using transmission and scanning electron microscopies (TEM and SEM) and atomic absorption spectroscopy (AAS). A medium polarity was identified in which magnetic particles with a narrow size distribution were formed. As expected, oleic acid‐coated Fe3O4 nanoparticles contributed to the stabilization of the polymerized magnetic microspheres. Alkyne groups in magnetic PPRAAm microspheres were detected by infrared spectroscopy. Magnetic PPRAAm microspheres were successfully used as the anchor to enable a “click” reaction with an azido‐end‐functionalized model peptide (radiolabeled azidopentanoyl‐GGGRGDSGGGY(125I)‐NH2) and 4‐azidophenylalanine using a Cu(I)‐catalyzed 1,3‐dipolar azide‐alkyne cycloaddition reaction in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献