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961.
962.
963.
Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Nafion-coated film electrodes of bulk-Pt and Pt nanoparticles dispersed on carbon black (Pt/CB) were investigated in 0.1 M HClO(4) solution at 30 to 110 degrees C by using a channel flow double electrode method. We have found that the apparent rate constants k(app) (per real Pt active surface area) for the ORR at bulk-Pt (with and without Nafion-coating) and Nafion-coated Pt/CB (19.3 and 46.7 wt % Pt, d(Pt) = 2.6 to 2.7 nm) thin-film electrodes were in beautiful agreement with each other in the operation conditions of polymer electrolyte fuel cells (PEFCs), i.e., 30-110 degrees C and ca. 0.7 to 0.8 V vs RHE. The H(2)O(2) yield was 0.6-1.0% at 0.7-0.8 V on all Nafion-coated Pt/CB and bulk-Pt and irrespective of Pt-loading level and temperature. Nafion coating was pointed out to be a major factor for the H(2)O(2) formation on Pt catalysts modifying the surface property, because H(2)O(2) production was not detected at the bulk-Pt electrode without Nafion coating. 相似文献
964.
This paper is concerned with the structure of the set of radially symmetric solutions for the equation
965.
Itoh T Fukutani K Hino M Ihara E Inoue K 《Journal of colloid and interface science》2009,330(2):292-297
The effects of polystyrene-b-poly(aminomethyl styrene) (PSn-b-PAMSm) stabilizers on the particle size (Dn) and size distribution (PSD) in dispersion polymerization of styrene were investigated. The block copolymers, PSn-b-PAMSm, were prepared as follows: (i) atom transfer radical polymerization (ATRP) of styrene (PS-Br), (ii) ATRP of vinylbenzylphthalimide with the PS-Br (PS-b-PVBP), and (iii) treatment of the PS-b-PVBP with hydrazine. When the dispersion polymerization of styrene proceeded at 60 °C in ethanol with PS19-b-PAMS130 stabilizer, spherical polystyrene particles with Dn=0.91 μm (PSD = 1.01) were obtained. The particle size was strongly affected by the copolymer composition. With an increase in PAMS block length from m=54 to 100 in PS17-b-PAMSm, particle diameter became smaller from 1.55 to 0.91 μm. On the other hand, an increase in the length from m=20 to 82 in PS34-b-PAMSms caused an increase in particle size from 0.35 to 0.70 μm. Titration of the particles suggests that 14–81% of stabilizers used in the polymerization system were attached on the polystyrene particle surfaces, depending on the composition of the block copolymers. Thus, for the dispersion polymerization of styrene, PSn-b-PAMSm block copolymers have both functions as a stabilizer during polymerization and surface-modification sites of polystyrene particles. 相似文献
966.
Shin-ichi Fukuzawa Eiji Shimizu Yuka Atsuumi Masatake Haga Kenichi Ogata 《Tetrahedron letters》2009,50(20):2374-1304
The cross-coupling reaction of benzoxazole with aryl thiols using the CuI/2,2′-bipyridine complex as a catalyst in DMF at 80 °C under oxygen produced the corresponding aryl thioethers in moderate to good yields. The coupling reaction with diaryl disulfide also occurred under similar oxidative conditions. 相似文献
967.
968.
Mitsuhiro Terakawa Eiji Toratani Tatsuya Shirakawa Minoru Obara 《Applied Physics A: Materials Science & Processing》2010,100(4):1041-1047
We describe a systematic investigation on void structures fabricated by femtosecond laser irradiation inside dielectric materials
for fabrication of a compact optical circuit. Void shapes fabricated in 5 different dielectric materials were compared and
the physical constants determining the void shape were discussed. A long void array is obtainable in a material which has
a low critical power for self-focusing. It was also indicated that the coefficient of thermal expansion is a dominant governing
factor to fabricate a precise void which has a clear boundary. Furthermore, we propose and design a Mach-Zehnder interferometer
in fused silica composed of optical waveguides and photonic crystals to verify practical application of a void array. Simulation
results of the optical propagation in a Mach-Zehnder interferometer indicated that the photonic crystals using a void array
have potential to fabricate compact optical circuits. 相似文献
969.
K. Sekimoto M. Takayama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(3):589-599
The change in the distribution pattern of negative ions HO–, NOx-_{x}^{-} and COx-_{x}^{-} observed on arbitrary point-to-plane electrode configuration has been investigated by varying the angle of needle to the
plane electrode, under atmospheric pressure corona discharge
conditions. The stationary inhomogeneous electric field distributions between the point-to-plane electrodes with arbitrary
needle angle were calculated. The experimental and theoretical results obtained suggested that the negative ion evolutions
progress along field lines established between
the electrodes with arbitrary configurations and the resulting terminal ion formation on a given field line is attributable
to the electric field strength on the needle tip surface where the field line arose. The NOx-_{x}^{-} and COx-_{x}^{-} ions were dominantly produced on the field lines arising from the needle tip apex region with the highest electric field
strength, while the field lines emanating from the tip peripheral regions with lower field strength resulted in the formation
of the HO– ion. 相似文献
970.
Neutralino dark matter is well motivated, but also suffers from two shortcomings: it requires gravity-mediated supersymmetry breaking, which generically violates flavor constraints, and its thermal relic density Omega is typically too large. We propose a simple solution to both problems: neutralinos freeze-out with Omega approximately 10-100, but then decay to approximately 1 GeV gravitinos, which are simultaneously light enough to satisfy flavor constraints and heavy enough to be all of dark matter. This scenario is naturally realized in high-scale gauge-mediation models, ameliorates small scale structure problems, and implies that "cosmologically excluded" models may, in fact, be cosmologically preferred. 相似文献