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991.
Magdalena Ratajczak Dorota Kaminska Eliza Matuszewska Elbieta Hoderna-Kedzia Jarosaw Rogacki Jan Matysiak 《Molecules (Basel, Switzerland)》2021,26(13)
Bee products have been known for centuries for their versatile healing properties. In recent decades they have become the subject of documented scientific research. This review aims to present and compare the impact of bee products and their components as antimicrobial agents. Honey, propolis, royal jelly and bee venom are bee products that have antibacterial properties. Sensitivity of bacteria to these products varies considerably between products and varieties of the same product depending on their origin. According to the type of bee product, different degrees of activity were observed against Gram-positive and Gram-negative bacteria, yeasts, molds and dermatophytes, as well as biofilm-forming microorganisms. Pseudomonas aeruginosa turned out to be the most resistant to bee products. An analysis of average minimum inhibitory concentration values for bee products showed that bee venom has the strongest bacterial effectiveness, while royal jelly showed the weakest antibacterial activity. The most challenging problems associated with using bee products for medical purposes are dosage and safety. The complexity and variability in composition of these products raise the need for their standardization before safe and predictable clinical uses can be achieved. 相似文献
992.
Anna Chachaj-Brekiesz Krzysztof Zborowski Joanna Zemła Katarzyna Makyła-Juzak 《Molecular physics》2013,111(24):3567-3577
Symmetrical triblock semifluorinated n-alkane, di(perfluorohexyl)hexane of the formula F(CF2)6(CH2)6(CF2)6F (abbreviated F6H6F6), has been synthesised and investigated at the air/water interface. Our results show for the first time that this unusual film-forming material, completely hydrophobic in nature and possessing no polar group, is capable of stable film formation at the free water surface. The surface pressure–area isotherm of the studied compound exhibited two regions: corresponding to monotonous pressure rise, followed by a pseudo-plateau region. Visualisation of film structure with Brewster angle microscope (BAM) proved the formation of domains within the pseudo-plateau region. A closer insight into the structure of these domains with atomic force microscope (AFM) proved their ordered, circular shape. The average area of F6H6F6 domain was found to depend on surface pressure value, as it is 4.98 ± 1.75 μm2 at π = 1.2 mN/m to 16.54 ± 0.31 μm2 at π = 1.7 mN/m. Following performed quantum-chemical calculations, it can be concluded that the observed surface aggregates from F6H6F6 are formed by linear conformers with shifted CF and CH parts. The calculated domain thickness is between 20 and 21 Å, which perfectly agrees with the experimental value estimated from AFM measurements (20.3 ± 1.4 Å). 相似文献
993.
We report on studies of changes in the emission spectra (excited at 808 nm) of the Yb-doped Ca4NdO(BO3)3 single crystals due to the photothermal effects caused by the pulsed Nd:YAG laser. Increase of the sample's surface temperature after laser treatment leads to significant enhancement of the 1040 to 1060 nm emission (ascribed to the Nd3+ 4F3/2 → 4I9/2, 4I11/2 transitions) and simultaneous decrease of the 975 to 1050 nm emission (corresponding to the Yb3+ 2F5/2 → 2F7/2 transition). We explain such an increase of the Nd3+ luminescence by thermally activated Yb3+ → Nd3+ energy transfer. 相似文献
994.
J. Równicka-Zubik A. Sułkowska M. Maciążek-Jurczyk L. Sułkowski W. W. Sułkowski 《光谱学快报》2013,46(7):520-529
Sulindac (SDC) is a nonsteroidal anti-inflammatory drug, useful in the treatment of chronic and acute inflammatory conditions. The binding of SDC to human serum albumin and bovine serum albumin was studied by fluorescence spectroscopy and the results compared with those obtained for human and bovine serum albumin destabilized with urea and guanidine hydrochloride. SDC interacts with serum albumin within the hydrophobic subdomain IIA and/or IB. The analysis of the binding constants shows that the studied albumins preserve their binding capacity in the presence of destabilizing/denaturating agents. The denaturation coefficient has been calculated to estimate the degree of denaturation of protein. 相似文献
995.
Abstract α,ω-Tertiary diamines react under high pressure with α,ω-di-iodo compounds to give cyclic or bicyclic bis-quaternary salts in almost quantitative yields. The role of high-pressure-induced changes in conformation of linear intermediates and the viscosity factor are discussed. 相似文献
996.
Wojciech Paszkowicz Scott M. Woodley Paweł Piszora Bohdan Bojanowski Jarosław Piętosa Yngve Cerenius Stefan Carlson Christine Martin 《Applied Physics A: Materials Science & Processing》2013,112(4):839-845
Elastic properties of CaMnO3 are of primary importance in the science and technology of CaMnO3-based perovskites. From X-ray diffraction experiments performed at pressures up to 100 kbar using a diamond-anvil cell to hydrostatically compress our sample, a bulk modulus, K 0, of 1734(96) kbar was obtained after fitting parameters to the third-order Birch–Murnaghan equation of state. Mean field, semiclassical simulations predict, for the first time, the third-order equation-of-state parameters and show how the bulk modulus increases with pressure (the zero pressure value being 2062.1 kbar) and decreases with the extent of nonstoichiometry caused by the formation of oxygen vacancies. These trends are amplified for the shear modulus. A more accurate model that allows for the explicit reduction of Mn ions, or localization of excess electrons, yields qualitatively similar results. The experimental and calculated axial ratios show the same trends in their variation with rising pressure. 相似文献
997.
The anode supported cell for solid oxide fuel cell, as a modification of the traditional Ni-YSZ anode supported on electrolyte, is examined in this work. The materials obtained on the base of citric method are presented and investigated in this work. The materials consisted of 40 wt.% Ni/YSZ, 50 wt.% Ni/YSZ and 60 wt.% Ni/YSZ were obtained. The base Ni/YSZ materials are tested on the two ways: (a) aging tests and (b) sintering tests. All the materials after aging and sintering are tested by the impedance spectroscopy. The results of electrical conductivity for samples before and after aging show that only in the case of 40 wt.% Ni/YSZ, sample loses of metallic conductivity after 500 h of heating. The other samples reveal metallic conductivity even after long period of aging. The tests of sintering temperature show that this process does not affect significantly on electrical conductivity of the materials. 相似文献
998.
Małgorzata Norek Grzegorz Łuka Marek Godlewski Tomasz Płociński Marta Michalska-Domańska Wojciech J. Stępniowski 《Applied Physics A: Materials Science & Processing》2013,111(1):265-271
Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ~2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes. 相似文献
999.
Melania Bednarek Przemysaw Kubisa 《Journal of polymer science. Part A, Polymer chemistry》2005,43(17):3788-3796
The cationic copolymerization of ε‐caprolactone with ethylene oxide (EO) under the conditions of activated monomer polymerization, that is, with a low‐molecular‐weight diol as an initiator and BF3 etherate as a catalyst, was studied. To ensure the uniform composition of the resulting copolymers (telechelic oligodiols), the copolymerization was conducted with incremental feeding of the EO comonomer, which was more reactive in the cationic process. 1H NMR analysis of samples isolated at different stages of the copolymerization indicated that the average composition of the copolymer was indeed nearly constant over the course of the copolymerization. Matrix‐assisted laser desorption/ionization time‐of‐flight spectra of the products revealed, however, that for the same degree of polymerization, macromolecules containing different numbers of EO units were present. The observed distribution was compared with the distribution simulated under the assumption that the probability of incorporating a given unit depended only on the feed composition (nearly constant during the copolymerization). With this assumption, a good agreement between the observed and simulated spectra was obtained. This indicated that, even when the optimum conditions for the formation of a uniform copolymer were created, the individual macromolecules differed in composition because of the statistical character of the copolymerization. The results of differential scanning calorimetry analysis were compatible with such a conclusion; two melting peaks appeared on differential scanning calorimetry curves when a sample was heated immediately after fast cooling, and this may indicate the presence of different types of crystallites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3788–3796, 2005 相似文献
1000.
Stanis?aw Gawiejnowicz Wies?aw Kurc Lidia Pankowska 《Discrete Applied Mathematics》2006,154(15):2150-2166
In the paper a single machine time-dependent scheduling problem is considered. The processing time pj of each job is described by a function of the starting time t of the job, pj=1+αjt, where the job deterioration rate αj?0 for j=0,1,…,n and t?0. Jobs are nonpreemptable and independent, there are no ready times and no deadlines. The criterion of optimality of a schedule is the total completion time.First, the notion of a signature for a given sequence of job deterioration rates is introduced, two types of the signature are defined and their properties are shown. Next, on the basis of these properties a greedy polynomial-time approximation algorithm for the problem is formulated. This algorithm, starting from an initial sequence, iteratively constructs a new sequence concatenating the previous sequence with new elements, according to the sign of one of the signatures of this sequence.Finally, these results are applied to the problem with job deterioration rates which are consecutive natural numbers, αj=j for j=0,1,…,n. Arguments supporting the conjecture that in this case the greedy algorithm is optimal are presented. 相似文献