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181.
Until now the reactions of organic peroxy radicals (RO2) with alkenes in the gas phase have been essentially studied at high temperature (T ≥ 360 K) and in the context of combustion processes, while considered negligible in the Earth''s atmosphere. In this work, the reactions of methyl-, 1-pentyl- and acetylperoxy radicals (CH3O2, C5H11O2, and CH3C(O)O2, respectively) with 2-methyl-2-butene, 2,3-dimethyl-2-butene and for the first time the atmospherically relevant isoprene, α-pinene, and limonene were studied at room temperature (298 ± 5 K). Monitoring directly the radicals with chemical ionization mass spectrometry led to rate coefficients larger than expected from previous combustion studies but following similar trends in terms of alkenes, with (in molecule−1 cm3 s−1) = 10−18 to 10−17 × 2/2 and = 10−14 to 10−13 × 5/5. While these reactions would be negligible for CH3O2 and aliphatic RO2 at room temperature, this might not be the case for acyl-, and perhaps hydroxy-, allyl- and other substituted RO2. Combining our results with the Structure–Activity Relationship (SAR) predicts kII(298 K) ∼10−14 molecule−1 cm3 s−1 for hydroxy- and allyl-RO2 from isoprene oxidation, potentially accounting for up to 14% of their sinks in biogenic-rich regions of the atmosphere and much more in laboratory studies.The reactions of organic peroxy radicals with alkenes, overlooked until now, could be more significant than expected for some RO2 in the atmosphere. 相似文献
182.
The aim of this study was to develop a chromatographic method, as a substitute for enzyme-linked immunosorbent assays, for the rapid and simultaneous detection of IgG, insulin, and transferrin present in a cell culture medium. Conjoint liquid chromatography (conjoint LC) using monolithic disks was applied for this purpose. An anion-exchange disk was combined with a Protein G affinity disk in a preparative HPLC system. IgG bound to the Protein G disk, whereas transferrin and insulin were captured on the quaternary ammonium (QA) disk. Using this method, it was possible to simultaneously determine the concentrations of IgG, transferrin, and insulin in the cell culture medium. Thus, conjoint LC could be used for the rapid and simultaneous detection of different proteins present in a cell culture medium. 相似文献
183.
Fabienne Chouraqui 《Geometriae Dedicata》2009,138(1):173-192
Every tame, prime and alternating knot is equivalent to a tame, prime and alternating knot in regular position, with a common
projection. In this work, we show that the Dehn presentation of the knot group of a tame, prime, alternating knot, with a
regular and common projection has a finite and complete rewriting system. Although there are rules in the rewriting system
with left-hand side a generator and which increase the length of the words we show that the system is terminating.
相似文献
184.
Geoffrey Schwertz Andrea Zanetti Marllon Nascimento de Oliveira Mario Andrès Gomez Fernandez Fabienne Dioury Janine Cossy Zacharias Amara 《Tetrahedron》2019,75(6):743-748
Amorphadiene is a natural product involved in the biosynthesis of the antimalarial drug artemisinin. A convenient four-step synthesis of amorphadiene, starting from commercially available dihydroartemisinic acid, is reported. The targeted molecule is isolated with an overall yield of 85% on a multi-gram scale in four steps with only one chromatography. 相似文献
185.
Julien MH de Vaulx C Mayaffre H Berthier C Horvatić M Simonet V Wooldridge J Balakrishnan G Lees MR Chen DP Lin CT Lejay P 《Physical review letters》2008,100(9):096405
From 59Co and 23Na NMR, we demonstrate the impact of the Na+ vacancy ordering on the cobalt electronic states in Na0.75CoO2: at long time scales, there is neither a disproportionation into 75% Co3+ and 25% Co4+ states, nor a mixed-valence metal with a uniform Co3.25+ state. Instead, the system adopts an intermediate configuration in which 30% of the lattice sites form an ordered pattern of localized Co3+ states. Above 180 K, an anomalous mobility of specific Na+ sites is found to coexist with this electronic texture, suggesting that the formation of the latter may contribute to stabilizing the Na+ ordering. Control of the ion doping in these materials thus appears to be crucial for fine-tuning of their thermoelectric properties. 相似文献
186.
Koutroulakis G Mitrović VF Horvatić M Berthier C Lapertot G Flouquet J 《Physical review letters》2008,101(4):047004
We report 115In nuclear magnetic resonance (NMR) measurements in CeCoIn5 at low temperature (T approximately 70 mK) as a function of the magnetic field (H0) from 2 to 13.5 T applied perpendicular to the c axis. A NMR line shift reveals that below 10 T the spin susceptibility increases as sqrt[H0]. We associate this with an increase of the density of states due to the Zeeman and Doppler-shifted quasiparticles extended outside the vortex cores in a d-wave superconductor. Above 10 T a new superconducting state is stabilized, possibly the modulated phase predicted by Fulde, Ferrell, Larkin, and Ovchinnikov. This phase is clearly identified by a strong and linear increase of the NMR shift with the field, before a jump at the first order transition to the normal state. 相似文献
187.
Yunus Zorlu Ümit İşci İlker Ün Ufuk Kumru Fabienne Dumoulin Vefa Ahsen 《Structural chemistry》2013,24(4):1027-1038
Phthalonitriles disubstituted by alkylsulfanyl moieties of different bulkiness (tert-butyl, adamantly, cyclohexyl and hexyl) and in 4,5- or 3,6-positions, respectively, set A and set B, have been prepared for comparative structural analyses. Miscellaneous parameters such as melting points and related polarity of the compounds are summarized. Substituents position and bulkiness effects on NMR and IR spectroscopy as well as refined X-ray structural data were examined. 相似文献
188.
Jean M. J. Tronchet Guido Zosimo-Landolfo Fabienne Villedon-Denaide Mirna Balkadjian Daniel Cabrini Françoise Barbalat-Rey 《Journal of carbohydrate chemistry》2013,32(6):823-835
ABSTRACT Cyclopentylidene ketals, moderately more acid-labile than their isopropylidene analogs, offer an alternative to the latter blocking groups. They have been shown to resist a large variety of reaction conditions commonly encountered in carbohydrate chemistry. 相似文献
189.
Palladium-catalyzed copper-free Sonogashira cross-coupling reactions were performed on a protected and unprotected monoiodotriglycerol substituted Zn(II) phthalocyanine with various alkynes in organic and aqueous medium. From the silyl protected alkyne derivative, a protected homo coupled dimeric product was also prepared using Glaser coupling. All products were purified by reverse phase HPLC and the assigned structures were confirmed by mass and UV-vis spectroscopy. 相似文献
190.