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991.
An automated high-performance liquid chromatographic assay for the determination of an aldosterone antagonist (I) is described using column switching for direct injection of urine samples. After dilution with buffered internal standard solution, the sample was injected onto a clean-up column (17 X 4.6 mm I.D.), dry-packed with C18 reversed-phase material (particle size 30 micron). Polar urine components were removed by flushing the clean-up column with water. Retained substances, including I and the internal standard, were desorbed by backflush elution onto a 5-micron ODS-silica analytical column (125 X 4 mm I.D.), separated with water-methanol-tetrahydrofuran, and detected at 295 nm. After backflushing the analytical column and re-equilibrating the clean-up column, the system was ready for the next injection. The limit of quantification was ca. 100 ng/ml, using a 100-microliter specimen of diluted urine. The mean inter-assay precision of the method up to 25.6 micrograms/ml was 2%. Practicability and accuracy of the new method were demonstrated by the application to excretion studies performed with human volunteers. 相似文献
992.
U. Abram S. Abram J. Stach R. Kirmse 《Journal of Radioanalytical and Nuclear Chemistry》1986,100(2):325-333
Pertechnetate, TcO
4
–
, is reduced by thionyl chloride and phosphoryl chloride, respectively, to yield semistable Tc(VI) intermediates which can easily be detected by EPR spectroscopy. Spectra are recorded in liquid and frozen solutions. EPR data as well as chemical behaviour suggest the compounds obtained to be oxochloro complexes of technetium(VI). 相似文献
993.
A method for the determination of cadmium, copper, lead, and zinc in biological tissues using small volumes of digest is described. An aluminium heating block is used to digest samples and elements are determined by spike-height flame atomic absorption spectrometry. Interferences have been assessed and the sample decomposition procedure evaluated. 相似文献
994.
H. Brüggemeyer V. Pfeufer U. Nielsen J. -F. Wyart 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1986,1(3):269-281
Hyperfine constants of low lying levels of the configuration 4f 115d6s 2 in Er I have been measured for the only stable odd isotope,167Er, using high resolution laseratomic-beam spectroscopy. Hyperfine parameters were evaluated from the experimental data using the effective tensor operator formalism. For this purpose eigenfunctions have been determined from an analysis of the fine structure energies of Er I as well as from ab initio multiconfiguration Dirac-Fock calculations. With the latter method also ab initio hyperfine constants for the levels investigated were evaluated. A comparison of calculated fine structure energies, Landég J -factors and hyperfine constants with the experimental data allowed a test of the reliability of the fine structure and multiconfiguration Dirac-Fock wavefunctions. Effective nuclear electric quadrupole moments for167Er have been determined from the experimental hyperfine constants using both calculated relativistic electronic radial integrals and hyperfine parameters for the 4f and 5d electrons in the configuration 4f 115d6s 2 in Er I. From a comparison with the nuclear quadrupole moment measured in the mesic atom Sternheimer shielding factors are calculated. Configuration-interaction contributions to the radial integrals 〈r ?3〉 nl 01 of the 4f and 5d electrons have been determined. 相似文献
995.
U. I. Zhorszky 《Journal of mass spectrometry : JMS》1986,21(6):357-365
Bifunctional methoxonium ions \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} -\mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OH}({\rm b}) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} - \mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OCH}_3 ({\rm c}) $\end{document} (c) show as the main reactions those caused by functional group interaction, as has already been found for the analogous hydroxonium ions (g). Although there are similarities in the fragmentation behaviour of the isomeric ions b and g, their fragmentation pathways are different, proving b and g as distinct species. The dominant primary fragmentation for b and c is loss of CH3OH. The hydrogen migrations prior to this reaction have been established by deuterium labelling. The findings on the fragmentation behaviour of the bifunctional methoxonium ions have been extended to the general behaviour of hydroxy and alkoxy substituted alkoxonium ions. 相似文献
996.
I. A. Mostert P. Anker H. -B. Jenny U. Oesch W. E. Morf D. Ammann Prof. Dr. W. Simon 《Mikrochimica acta》1985,85(1-2):33-38
Summary Silicone rubber is a universal membrane matrix for neutral carrier based ion-selective electrodes. Carrier antibiotics as well as synthetic ionophores yield sensors with selectivities that are comparable or even higher than those of corresponding poly(vinyl chloride) (PVC) membrane systems. The permeability of silicone rubber membranes for gas molecules is about ten times higher than the permeability of PVC membranes. In contrast, the electrical conductivity is by a factor of 10–100 lower.
Auf neutralen Carriern beruhende Silikongummimembran-Elektroden mit Selektivität für H3O+, K+, NH4 + und Ca2+
Zusammenfassung In ionenselektiven Elektroden auf der Basis von neutralen Carriern läßt sich Silikongummi als universelle Membranmatrix einsetzen. Entsprechende Sensoren sind sowohl mit ionenselektiven Antibiotika als auch mit synthetischen Carriern realisiert worden. Ihre Selektivitäten übertreffen teilweise jene von entsprechenden PVC-Membranen. Die Permeabilität der Silikongummimembranen für Gasmolekel ist ungefähr zehnmal höher als jene von PVC-Membranen. Andererseits ist die elektrische Leitfähigkeit um einen Faktor 10–100 niedriger.相似文献
997.
998.
Exchange kinetics of some transition metal ions on tin(IV) arsenosilicate has been studied at various temperatures under particle diffusion controlled conditions. Various useful kinetic parameters such as self-diffusion coefficient (Do), energy of activation (Ea) and entropy of activation (S*) have been calculated and compared with other similar materials.
(IV) . , (DO), (Ea) (S*), .相似文献
999.
Lipid membranes composed of phosphatidyl choline and cholesterol were interfaced to polyacrylamine hydrogen by Langmuir—Blodgett thin-film deposition. The extent of lipid adsorption to the gel surface was critically dependent on the hydration of the polymer as determined by contact angle measurements. Some electrochemical transducers incorporating the deposited membrane/gel structure responded positively to phloretin and valinomycin. Limitations to the construction of this device are discussed. 相似文献
1000.