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121.
David S. Weinberg M. Lisa Manier Mark D. Richardson Frederick G. Haibach Tina S. Rogers 《Journal of separation science》1992,15(10):641-654
Nine organosulfur compounds present in an aged garlic extract and two isoflavonoids and one triterpenoid present in a licorice root extract powder have been identified and quantified. Quantification involved solvent extraction and gas chromatographic – mass spectrometric analysis (garlic extract) or hydrolysis, solvent extraction, and liquid chromatographic analysis (licorice root extract powder). Although the garlic extract proved to be unstable and the concentration of the organosulfur compounds varied with time, one analysis of the extract gave the following results: methyl disulfide (0.607 μg/g), methyl trisulfide (0.181 μg/g), allyl sulfide (2.02 μg/g), allyl disulfide (0.784 μg/g), allyl trisulfide (0.795 μg/g), allyl methyl sulfide (1.64 μg/g), allyl methyl disulfide (0.411 μg/g), allyl methyl trisulfide (0.695 μg/g), and ethyl 2-propenesulfinate (11.4 μg/g). The analysis of the licorice root extract powder gave the following results: formononetin (1.92 mg/g), isoliquiritigenin (9.61 mg/g), and 18β-glycyrrhetinic acid (43.9 mg/g). Methods were successfully developed to quantify the same compounds in the serum of test animals which had consumed feed spiked with garlic extract or licorice root extract powder. Only the 18β-glycyrrhetinic acid could be detected in the sera of such animals, however. An effort was also made to determine serum levels of prostaglandin E2 to correlate its inhibition with levels of the dietary components, but the prostaglandin E2 levels were too low to measure. 相似文献
122.
L. Reeve T. Swinden W. W. Stevenson G. E. Speight H. A. Sloman F. Willems N. Gray M. C. Sanders S. N. Schkotowa H. Kempf K. Abresch G. J. Weinberg R. Stumper P. Mettelock F. Wüst J. Duhr P. Klinger W. Koch H. Schottky H. Hiltenkamp H. J. Wiester I. Wada und R. Ishii 《Fresenius' Journal of Analytical Chemistry》1943,126(10):385-390
Ohne Zusammenfassung 相似文献
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Ravi K Kukkadapu Hong Li Gary L Smith Jun-Sik Jeoung Michael C Weinberg 《Journal of Non》2003,317(3):301-318
Local environments of ferric and ferrous irons were systematically studied with Mössbauer (at liquid helium temperature) and ultraviolet-visible-near infrared spectroscopic methods for various 18Na2O-72SiO2 glasses doped with 0.5 mol% Fe2O3. These were prepared at temperatures of 1300-1600 °C in ambient air or at 1500 °C under reducing conditions with oxygen partial pressures from 12.3 to 0.27×10−7 atmospheres. The Mössbauer spectroscopic method identified three types of local environments, which were represented by the Fe3+ sextet, the Fe3+ doublet, and the Fe2+ doublet. The Fe3+ sextet ions were assigned to ‘isolated’ octahedral ions. Under reducing conditions, the octahedral Fe3+ ions were readily converted into octahedral ferrous ions. The Fe3+ doublet exists both in octahedral and tetrahedral environment, mainly as tetrahedral sites in the reduced samples. The tetrahedral ions were found stable against reduction to ferrous ions. The Fe2+ doublet sites existed in octahedral coordination. Combining results from both spectroscopic studies, the 1120- and 2020-nm optical bands were assigned to octahedral ferrous ions with a different degree of distortion rather than different coordinations. Further, we assigned the 375-nm band to the transition of octahedral ferric ions that are sensitive to the change of oxygen partial pressure in glass melting and 415-, 435-, and 485-nm bands to the transitions of the tetrahedral ferric ions that are insensitive to oxidation states of the melt. The effect of ferric and ferrous ions with different coordination environments on the glass immiscibility was elucidated. 相似文献
126.
J. Steiger D.A. Church G. Weinberg B.R. Beck J. McDonald D. Schneider 《Hyperfine Interactions》1997,108(1-3):115-119
Electron transfer from H2 to Th79+ was studied in a cryogenic Penning trap by non-destructively observing the sequential development with time of the charge
state of one or a few stored particles. The ratio of the true double capture cross section to the total capture cross section
was found to be 0.21 ± 0.11 at a mean center-of-mass energy near 6 eV.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
127.
Scanning tunneling microscopy and temperature-programmed desorption have been used to investigate the chemistry of water on Si(111)-(7 × 7) substrates which were misoriented 2° toward the [
10] direction. Upon room temperature exposure to water, the adatoms of the (7 × 7) unit cell are still evident even after high exposures, implying that major modifications of the substrate do not occur. At high coverages, the distribution of reacted adatoms shifts from one controlled by dissociative adsorption across the adatom-rest atom pair to a statistical distribution based on the availability of dangling bonds. Desorption of the oxide layer which remains after water adsorption and the desorption of hydrogen have also been characterized. The oxide desorption occurs along well-defined wavefronts which originate at step edges and advance in directions consistent with the underlying substrate symmetry, primarily the [
2] direction (i.e. the wave vector points in the [
2] direction). In regions of the surface where the oxide has desorbed, the (7 × 7) unit cell can be seen clearly. Vacancies resulting from the loss of surface silicon atoms (via the etching) coalesce into islands in the clean regions of the terraces, but unlike desorption of oxide layers from Si(100), the desorption does not occur from the boundaries of these vacancy islands. 相似文献
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