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81.
Espinoza-Vergara Javier Pavez Jorge Gonzalez Evelyn Ramirez Cristián Páez Maritza Gulppi Miguel 《Journal of Solid State Electrochemistry》2019,23(12):3225-3229
Journal of Solid State Electrochemistry - Here we demonstrate that the metal ion excess after precipitating a sparingly soluble metal salt can be conveniently determined by a secondary... 相似文献
82.
Virgil Percec Anatoliy V. Popov Ernesto Ramirez‐Castillo Oliver Weichold 《Journal of polymer science. Part A, Polymer chemistry》2004,42(24):6364-6374
The accelerated single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H2O/tetrahydrofuran (THF) at 25 °C is reported. This process is catalyzed by sodium dithionite (Na2S2O4)‐sodium bicarbonate (NaHCO3). Electron transfer cocatalysts (ETC) 1,1′‐dialkyl‐4,4′‐bipyridinum dihalides or alkyl viologens were also employed in this polymerization. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight (Mn) = 2,000–12,000, no detectable amounts of structural defects, and both active chloroiodomethyl and inactive chloromethyl chain ends. The molecular weight distribution of PVC obtained is Mw/Mn = 1.5. The surface active agents afford the final polymers as a powder and provide an acceleration of the rate of polymerization. The role of ETC is to accelerate the single electron transfer (SET) step, whereas THF enhances the degenerative chain transfer (DT) step. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6364–6374, 2004 相似文献
83.
J. D. Uribe J. Osorio C. A. Barrero D. Giratá A. L. Morales A. Devia M. E. Gómez J. G. Ramirez J. R. Gancedo 《Hyperfine Interactions》2006,169(1-3):1355-1362
We have grown hematite (α–Fe 2 O 3) thin films on stainless steel and (001)-silicon single-crystal substrates by RF magnetron sputtering process in argon atmosphere at substrate temperatures from 400 to 800°C. Conversion Electron Mössbauer (CEM) spectra of the sample grown on stainless steel at 400°C exhibit values for hyperfine parameter characteristic of bulk hematite phase in the weak ferromagnetic state. Also, the relative line intensity ratio suggests that the magnetization vector of the polycrystalline film is aligned preferentially parallel to the surface. The X-ray diffraction (XRD) pattern of the polycrystalline thin film grown on steel substrates also corresponds to α–Fe 2 O 3. The samples were also analyzed by Atomic Force Microscopy (AFM), those grown on stainless steel reveal a morphology consisting of columnar grains with random orientation, given the inhomogeneity of the substrate surface. 相似文献
84.
James H. Yuan Amy C. Rogowski Jorge E. Ramirez 《Fresenius' Journal of Analytical Chemistry》1986,324(3-4):299-300
Conclusions PBI is a unique polymer for ion exchange/sorption or affinity chromatography. The excellent flow and ion exchange properties of PBI resins have been demonstrated by their applications for determinatiòn of urinary VMA and PBG. Furthermore, PBI was also applied successfully as an affinity chromatography medium for several enzymes with polymeric molecules as their substrates. These studies concluded that PBI polymer has versatile biochemical applications.
Biochemische Anwendung von Polybenzimidazol (PBI) als Ionenaustauscher und Sorbens相似文献
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do Nascimento PC Bohrer D Ramirez A Trevisan MG Tramontina J Rohlfes AL 《Talanta》2000,52(6):1047-1054
A method for the simultaneous voltammetric determination of free sulfide and volatile alkythiols (methanethiol/ethanethiol) existing as contaminant in parenteral nutrition (PN) solutions was developed. The volatile sulfides (dihydrogensulfide and alkylthiols) formed in the formulations were distilled over 45 min at 47°C in a purpose-made Conway cell. The analytes were quantified by differential pulse cathodic stripping voltametry (DPCSV) at the hanging mercury-drop electrode and determined, simultaneously as dihydrogensulfide and alkylthiols using a 60 s preconcentration time at −300 mV (versus Ag/AgCl, Cl− 3.0 mol l−1). The voltammetric signals were directly linear proportional to the sulfides concentrations in the PN solutions in the range 3–20 μmol l−1 and detection limits of about 2 μmol l−1 were calculated. Recoveries of sulfides from PN solutions in the range 90–110% were calculated using the method and nine commercial PN formulations were analyzed. Methanethiol and ethanethiol were quantified from their composite signals, and the mutual influence of the analytes on the DPCSV measurements is discussed. 相似文献
90.
The characteristics of the mixed-ligand iron(III)-fluoride-purpurin complex, including optimum conditions of formation and extraction into methyl isobutyl ketone are described. A procedure for determination of trace amounts of iron in fluoride medium (0.5M) with purpurin (1,2,4,-trihydroxy-anthraquinone) in methyl isobutyl ketone is given. The method is suitable for determining iron in the presence of large amounts of aluminium, cyanide, phosphate and nickel. 相似文献