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991.
The title compound, [Fe(C44H8F20N4)]·2C6H6, contains a four‐coordinated FeII atom, which lies on a center of symmetry. The porphyrin macrocycle is planar, and the Fe—N bond distances are in the range 1.9891 (13)–1.9982 (13) Å. The spin state of the FeII atom is intermediate (S = 1), as confirmed by NMR spectroscopy. The asymmetric unit contains two half benzene mol­ecules, each lying about an independent inversion centre; one of the benzene rings is located just below (and by inversion symmetry, another is just above) the Fe atom, where it interacts weakly with the porphyrin ring.  相似文献   
992.
This paper introduces explicit conditions for some natural family of polynomials to define Pisot or Salem numbers, and reviews related topics as well as their references.  相似文献   
993.
Several peptides with hypocholesterinemic properties were investigated in order to reveal structure-activity relationships. The semi-empirical AM1 method and molecular dynamics were used to determine common structural properties of these peptides. A mathematical model of the structure-activity relationship was obtained. According to this model, a hydrophobic part of these peptides is a required structural element for their biological activity. The proline acts as a key component in these compounds. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 367–372, July–August, 2005.  相似文献   
994.
The copolymers that are composed of poly(fluorene) (PF), poly(p‐phenylene), and Poly(p‐phenylenevinylene) as backbone and a large 4′‐(N,N′‐diphenylamino)diphenyl or 4′‐(N,N′‐diphenylamino)phenyl as pendent group were synthesized by the nickel(0)‐mediated polycoupling. The composition of the obtained copolymers was confirmed by H NMR. All the copolymers possessed a high weight‐average molecular weight and good solubility in common organic solvents. As the content of triphenyl amine pendants increases, the copolymers showed increased thermal stability due to increased glass transition temperature and increased hole injection ability because of decreased onset of the oxidation potential. In the photoluminescence spectra of copolymers, poly (BDAV30co‐DHF70) and poly(BDAPV30co‐DHF70) showed efficient energy transfer. indium tin oxide/poly(styrene sulfonate)‐doped poly(3,4‐ethylene dioxythiophene)/poly (BDAV30co‐DHF70)/LiF/Al device showed maximum brightness of 2267 cd/m2 and efficiency of 0.80 cd/A, with turn‐on voltage at 9.1 V. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 172–182, 2006  相似文献   
995.
Si1−xMnx diluted magnetic semiconductor (DMS) bulks were formed by using an implantation and annealing method. Energy dispersive X-ray fluorescence, transmission electron microscopy (TEM), and double-crystal rocking X-ray diffraction (DCRXD) measurements showed that the grown materials were Si1−xMnx crystalline bulks. Hall effect measurements showed that annealed Si1−xMnx bulks were p-type semiconductors. The magnetization curve as a function of the magnetic field clearly showed that the ferromagnetism in the annealed Si1−xMnx bulks originated from the interaction between interstitial and substitutional Mn+ ions, which was confirmed by the DCRXD measurements. The magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature was approximately 75 K. The present results can help to improve understanding of the formation mechanism of ferromagnetism in Si1−xMnx DMS bulks.  相似文献   
996.
We describe the synthesis and characterization of a weakly cross‐linked poly(methacrylic acid‐co‐ethyl acrylate) alkali‐swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate‐co‐butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH4‐ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632–5642, 2005  相似文献   
997.
The liquid crystalline properties of two series of non-symmetric liquid crystal dimers consisting of cholesterol and Schiff base moieties interconnected by ω-oxyalkanoyl spacers of varying length are compared: one series (SBOC- n ) carry the octyloxy tail on the Schiff base mesogen, and the other (SBOF- n ) a perfluoroheptylmethyloxy tail. In general, compounds with the fluorinated alkoxy tail exhibited mesophases over a much wider temperature range than those with the alkoxy tail. The latter series favoured the formation of more diverse mesophases than the former. SBOC-4, -5 and -7, and SBOF-4, -5 and -10 formed the chiral smectic C phase.  相似文献   
998.
This paper suggests and demonstrates a novel flow measurement technique: tunable AC thermal anemometry, that allows simple integration, robust measurement and extremely high accuracy. The principle and simple theoretical analysis of the technique are presented. To find the optimal condition at which the phase lag becomes most sensitive to the flow speed change, the phase lag was measured scanning the heating frequency from 1 to 100 Hz, while the flow speed of ethanol was increased stepwise from 0 to 40 mm/s. The sensitivity of the phase lag depended on the heating frequency and the flow speed. It was possible to measure the average flow speed of 0.7 mm/s with the resolution of 0.1 mm/s at 4 Hz.  相似文献   
999.
1000.
It has recently been shown that thin polymer films in the nanometer thickness range exhibit anomalous swelling maxima in supercritical CO2 (Sc‐Co2) in the vicinity of the critical point of CO2. The adsorption isotherm of CO2 on carbon black, silica surfaces, porous zeolites, and other surfaces, is known to exhibit anomalous maxima under similar CO2 conditions. It is believed that because CO2 possesses a low cohesive energy density, there would be an excess amount of CO2 at the surfaces of these materials and hence the CO2/polymer interface. This might cause excess CO2 in the polymer films near the free surface, and hence the swelling anomaly. In addition, an excess of CO2 would reside at the polymer/substrate and polymer/CO2 interfaces for entropic reasons. These interfacial effects, as have been suggested, should account for an overall excess of CO2 in a thin polymer film compared to the bulk, and would be responsible for the anomalous swelling. In this study, we use in situ spectroscopic ellipsometry to investigate the role of interfaces on the anomalous swelling of polymer thin films of varying initial thicknesses, h0, exposed to Sc‐CO2. We examined three homopolymers, poly(1,1′‐dihydroperflurooctyl methacrylate) (PFOMA), polystyrene (PS), poly(ethylene oxide) (PEO), that exhibit very different interactions with Sc‐CO2, and the diblock copolymer of PS‐b‐PFOMA. We show that the anomalous swelling cannot be solely explained by the excess adsorption of CO2 at interfaces. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1313–1324, 2007  相似文献   
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