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201.
Marta Barbadillo Elena Casero Maria Dolores Petit-Domínguez Félix Pariente Encarnación Lorenzo Luis Vázquez 《Journal of Sol-Gel Science and Technology》2011,58(2):452-462
We have studied, by scanning electron and atomic force (AFM) microscopies, how each step involved in the building process
of massive carbon-based sol–gel enzymatic biosensors changes and determines the resulting surface morphology and nano-mechanical
properties. The biosensor, selected as a model, is developed by the entrapment of glucose oxidase (GOx), a redox mediator
and a material conferring conductivity (graphite powder, C) into a polymeric tridimensional network generated by sol–gel technology
using tetraethoxysilane (TEOS) as precursor. The smooth TEOS morphology is formed by an irregular nanoporous network, which
is very adequate for enzyme encapsulation. Upon addition of carbon powder to the system (TEOS/C), the surface morphology changes
but it is still rather irregular since carbon powder micro-grains are found scattered on it. This morphology results in a
rather rough surface at the micro- scale whereas at the nano- scale both atomically flat graphitic and nanoporous TEOS domains
are found. In contrast, the final biosensing device surface is quite homogeneous and composed by flat platelets separated
by deep crevices. On top of most of these platelets there is a soft, as assessed by AFM force indentation experiments, layer
of globular structures whose dimensions are compatible with GOx molecules. The final device surface architecture results to
be open and accessible both at the micro and nano scales, which turns it as adequate to enhance both the accessibility of
the analytes to entrapped proteins and the mass-transfer rates. Finally, in order to show the applicability of the studied
biosensor, its response was evaluated towards varying glucose concentrations, displaying a clear electrocatalytic activity. 相似文献
202.
Density and viscosity were determined for the binary mixtures containing the ionic liquid 1-butyl-3-methylimidazolium thiocyanate
([BMIM][SCN]) and 1-alcohols (1-butanol, 1-pentanol and 1-hexanol) at six temperatures (298.15, 308.15, 318.15, 328.15, 338.15
and 348.15) K and ambient pressure. The density and viscosity correlation for these systems was tested by an empirical second-order
polynomial and by the Vogel-Fucher-Tammann equation in wide ranges of temperatures. Excess molar volumes were described by
the Redlich-Kister polynomial expansions. The density and viscosity variations with composition were described by polynomials.
A qualitative analysis of the trend of the properties with solvent and temperature was performed. The obtained results indicate
that ionic liquid interactions with 1-alcohols are strongly dependent on the special trend of packing of this ionic liquid
into hydroxylic solvents. As previously observed, an increase of the 1-alcohol carbon-chain length leads to lower interactions
on mixing.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
203.
204.
205.
Alexandra Muñoz‐Bonilla Gema Marcelo Cintia Casado Francisco J. Teran Marta Fernández‐García 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5087-5096
In this article, magnetite nanoparticles (MNPs) coated with glycopolymer bearing glucose moieties were designed with optimal structural, colloidal, and magnetic properties for biomedical applications. MNPs with an average size of 17 ± 2 nm were synthesized by thermal decomposition process and then their surfaces were modified with active vinyl groups. Two different monomers were immobilized onto the surfaces: dopamine methacrylamide, a monomer with properties inspired on mussels adhesive capacity, or unprotected glycomonomer, 2‐{[(D ‐glucosamin‐2N‐yl)carbonyl]‐oxy}ethyl methacrylate. Afterward, the glycomonomer were polymerized at the interface of both vinyl functionalized MNPs by conventional radical polymerization. The resultant hybrid NPs were water dispersible presenting good stability in aqueous solution for long time periods. Moreover, the high density of carbohydrates at the surface of the magnetic NPs could confer targeting properties to the system as demonstrated by studies of their binding interactions with lectins, where the binding activity is higher as the glycopolymer content augments. The magnetic and magneto‐thermal properties of the synthesized hybrid NPs were evaluated. The magnetization curves reveal superparamagnetic features at 300 K, with high values of saturation magnetization. Furthermore, the hybrid glycoparticles show suitable heat dissipation power when exposed to alternating magnetic field conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
206.
207.
Sergio Peris Bartosz Tylkowski Joan Carles Ronda Ricard Garcia‐Valls José Antonio Reina Marta Giamberini 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5426-5436
Two new polyethers, bearing azobenzene moiety in the side chain, were synthesized in excellent yields by means of anionic polymerization of 4‐glycidyloxyazobenzene and 4‐cyano‐4′‐glycidyloxyazobenzene (leading to azo‐P1 and azo‐P2 polymers, respectively) with the system polyiminophosphazene base t‐Bu‐P4/3,5‐di‐tert‐butylphenol as initiator. The polymers were characterized with respect to their molecular weights, structure, and calorimetric features. The polyether bearing cyanoazobenzene group in the side chain was found to exhibit nematic phase up to 200 °C. E–Z isomerization of both polymers in tetrahydrofuran solution, after irradiating with UV light at 364 nm for 15 min, was investigated by means of UV–visible absorption spectroscopy. In the case of glycidylic monomers as well as the resulting polymers, E–Z isomerization was also investigated by means of 1H NMR, by direct irradiation in the NMR probe in deuterated 1,1,2,2‐tetrachloroethane solution. By this technique, in the case of 4‐cyano‐4′‐glycidyloxyazobenzene, it was found that irradiation led to a photostationary state corresponding to an amount of Z isomer equal to 25%. For azo‐P1 polymer, Z–E or “reverse” isomerization was investigated at 60, 70, or 80 °C directly in the NMR probe; as expected, the process followed a first‐order rate law. The kinetic constants as well as the activation energy for the process were determined in this temperature range. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5426–5436, 2009 相似文献
208.
Marta Bugaj Piotr A. Baran Piotr Bernatowicz Patrycja Brożek Krystyna Kamieńska‐Trela Adam Krówczyński Bohdan Kamieński 《Magnetic resonance in chemistry : MRC》2009,47(10):830-842
A series of aryl‐substituted enaminoketones and their thio analogues in CDCl3 solution and in the solid state were studied by the use of high‐resolution 1H and 13C as well as 13C cross polarization magic angle spinning (CP MAS) NMR spectra in combination with gauge including atomic orbitals‐density functional theory (GIAO‐DFT) calculations performed at the B3PW91/6–311 + + G(d,p) level of theory using the B3PW91/6‐311 + + G(d,p)‐optimized geometries. The analysis of the 13C NMR spectra in solution was done by using the Incredible Natural Abundance DoublE QUAntum Transfer Experiment (INADEQUATE) technique, whereas trends observed in the 13C shielding constants, calculated for the compounds studied, were a great help in assigning most of the signals in the 13C CP MAS NMR spectra. It was established on the basis of the experimental and theoretical NMR data that both groups of compounds exist in the form of Z‐s‐Z‐s‐E isomers in CDCl3 solution as well as in the solid state, with the NH hydrogen atom involved in intramolecular hydrogen bonding. This conclusion is in agreement with the fact that some of the compounds studied reveal liquid‐crystalline properties. Three‐bond H, H and C, H coupling constants measured in solution played a crucial role in the structure elucidation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
209.
Marta Llorente Manuel Morán 《Journal of Mathematical Analysis and Applications》2007,334(2):1088-1095
We prove that if a self-similar set E in Rn with Hausdorff dimension s satisfies the strong separation condition, then the maximal values of the Hs-density on the class of arbitrary subsets of Rn and on the class of Euclidean balls are attained, and the inverses of these values give the exact values of the Hausdorff and spherical Hausdorff measure of E. We also show that a ball of minimal density exists, and the inverse density of this ball gives the exact packing measure of E. Lastly, we show that these elements of optimal densities allow us to construct an optimal almost covering of E by arbitrary subsets of Rn, an optimal almost covering of E by balls and an optimal packing of E. 相似文献
210.
In the paper, the computational complexity of several variants of the problem of isothermic DNA sequencing by hybridization, is analyzed. The isothermic sequencing is a recent method, in which isothermic oligonucleotide libraries are used during the hybridization with an unknown DNA fragment. The variants of the isothermic DNA sequencing problem with errors in the hybridization data, negative ones or positive ones, are proved to be strongly NP-hard. On the other hand, the polynomial time algorithm for the ideal case with no errors is proposed. 相似文献