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981.
Johannes Schöneberg Alexander Weismann Richard Berndt 《Applied Physics A: Materials Science & Processing》2013,111(1):285-288
Nickel islands are grown on W(110) at elevated temperatures. Islands with a thickness of two layers are investigated with scanning tunneling microscopy. Spectroscopic measurements reveal that nanometer sized areas of the islands exhibit distinctly different apparent heights and dI/dVspectra. Spin polarized and paramagnetic band structure calculations indicate that the spectral features are due to fcc(111) and bcc(110) orientations of the Ni film, respectively. 相似文献
982.
983.
984.
985.
H. P. Lang V. Thommen-Geiser C. Bolm M. Felder J. Frommer R. Wiesendanger H. Werner R. Schlögl A. Zahab P. Bernier G. Gerth D. Anselmetti H. -J. Güntherodt 《Applied Physics A: Materials Science & Processing》1993,56(3):197-205
Fullerene powder mixtures with different C60/C70 ratios have been analyzed by a variety of techniques, and results have been compared. The fullerence mixtures have been characterized as solutions in n-hexane by high-pressure liquid chromatography (HPLC) and UV-VIS spectroscopy. Thin films of fullerenes on Au(111) have been prepared from the mixtures by sublimation. The sublimation process has been studied by simultaneous thermogravimetric and differential thermal analyses. Thin fullerene films on Au(111) have been investigated by scanning tunneling microscopy (STM). The STM images show primarily two types of ballshaped molecules arranged in a lattice with hexagonal symmetry (fcc(111) face, nearest neighbour distance: 1 nm). The two species differ in diameter. STM images of films made of mixtures of different C60/C70 ratios show that C70 molecules display a larger apparent diameter (0.8 nm) and corrugation than C60 molecules (0.7 nm). The C60/C70 ratios obtained by counting the corresponding molecular species in the STM images of the thin films are compared to the C60/C70 ratios determined by HPLC on hexane solutions of the mixtures. The observed differences might be explained by different rates of sublimation for the two species. The STM images reveal film defects (vacancies and boundaries) and dynamic processes (displacement of C70 molecules and vacancies). In films prepared to have a C60 coverage of less than one monolayer, stable structural units of the C60(111) surface consisting of three or seven C60 molecules are revealed by STM. Occasionally, substructure within individual fullerene molecules is observed. 相似文献
986.
S. Niese K. Krogner C. -D. Werner B. Gleisberg 《Journal of Radioanalytical and Nuclear Chemistry》1993,169(1):81-92
Mantle-derived magmatites from the Saxonian Granulite Massif have been investigated by instrumental und radiochemical NAA. Pd, Ir and Pt were separated after irradiation by extraction with DDTC and DBDTO. Cs was precipitated by sodium tetraphenyl borate, the REE were isolated by cation exchange and the activation products of thorium and uranium by extraction with TOPO. The Lower-Riphean and Upper-Riphean magmatites contain sequences of partial melting and fractionated crystallization. They start from ultramafic garnet serpentinites with the composition of primary earth mantle. The contents of platinum group elements in garnet serpentinites amount to about 1% those of Cl chondrites. In depleted serpentinites, which are residues of partial melting, the concentration of Pd is reduced by a factor of 4.5. 相似文献
987.
988.
2H NMR spectra of copper acetate monohydrate [Cu(CD3CO2)2]·H2O, hexamethylbenzene-d18 and acetone-d6 were analyzed to characterize methyl group rotations between their classical and quantum mechanical limits. The temperature dependent spectra show the three different possible developments of the lineshapes. Hexamethylbenzene is typical of compounds with small but resolvable tunnelling frequencies. Characteristic splittings in the spectra of copper acetate monohydrate reveal the temperature dependence of tunnelling frequencies that are slightly larger than the quadrupole coupling constant. While the tunnelling frequency of acetone is already too large to be specified from2H NMR lineshape analysis at temperatures low enough that quantum effects influence the spectra, the temperature dependent spectra deviate characteristically from those found for classical rotation. Additionally to these experimental results, we outline how from an NMR point of view mixed classical and quantum rotations can be described by a single complex frequency. 相似文献
989.
The polycondensation of p-aminobenzoic acid by the use of triphenylphospine and hexachloroethane is described. One way to obtain a mixed solution of rigid rod and flexible coil polymers is the polycondensation of the rigid chains in a solution of a flexible polymer matrix. Results on matrix polycondensation of poly(p-benzamide) in solutions of poly(methyl methacrylate), poly(methyl methacrylate-co-styrene), polystyrene and polyacrylonitrile are reported. It is shown that there exists an interrelation between the phase behavior of the mixed polymer solutions and the influence of the matrix polymer on the synthesis of poly(1.4.-benzamide). The ternary phase diagrams of the rigid rod/flexible coil polymer solutions were determined. 相似文献
990.
Werner M. Seiler 《Acta Appl Math》1995,41(1-3):311-322
The computation of a number of arbitrary functions in the general solution is briefly reviewed. The results are used to study normal systems and their symmetry reduction. We discuss the treatment of gauge systems, especially the analysis of gauge fixing conditions. As examples, the Yang-Mills equations with the Lorentz gauge and Einstein's vacuum field equations with harmonic coordinates are considered. 相似文献