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排序方式: 共有226条查询结果,搜索用时 15 毫秒
1.
Structural and electronic properties of a new BEDT-TTF based radical cation salt, α-(BEDT-TTF)2CsCd(SCN)4, are presented. In the measurements of the electrical resistivity and the magnetic susceptibility, this new α-type salt shows metallic behavior down to low temperature. Measurements of the resistivity under in-plane c-axial strain reveal a newly observed insulating phase, suggesting that α-(BEDT-TTF)2CsCd(SCN)4 is placed near an insulating phase which might have close relationships with a superconducting phase realized in α-type salts. 相似文献
2.
Yoshitane Imai Kakuhiro Kawaguchi Tomohiro Sato Michiya Fujiki Yoshio Matsubara 《Tetrahedron letters》2007,48(16):2927-2930
By using (1R,2R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state. 相似文献
3.
Some molecules with a molecular skeleton similar to that of stilbenes and azobenzenes show orientational disorder in the crystals. If the disorder is dynamic, a conformational interconversion takes place through a pedal motion. In this study X-ray diffraction analyses of (E)-stilbene (1) and azobenzene (2) were carried out at various temperatures. We succeeded in observing thermodynamic nonequilibrium states that were generated by fast freezing of the conformational interconversion at low temperatures. The populations of the two conformers in crystals of 1 at 90 K varied with the cooling rate. Flash cooling of a crystal of 2 from room temperature to 90 K made it possible to observe the minor unstable conformer that does not exist in the equilibrium state at the same temperature. 相似文献
4.
[reaction: see text] The origin of exclusive exo-stereochemistry in the alkylation of Meyers-type enolate 2 has been studied. It was found that the intramolecular complex with a strong Li...O(ring) interaction (the O-complex) may be responsible as the major enolate species in tetrahydrofuran (THF). The transition state of the O-complex leading to exo-stereochemistry is found to be the most favorable process in THF. 相似文献
5.
The development of solid strong base catalysts utilizable in green but acidic medium of scCO2 is reviewed. The strong base sites on mesoporous alumina and sulfated mesoporous alumina that had been generated by severe treatment at 773 K under vacuum (10?4 Torr) were not neutralized by the compressed Lewis acidic molecules of CO2, promoting a representative strong base-catalyzed reaction of the Tishchenko reaction as well as a typical base-catalyzed reaction of the Knoevenagel reaction in scCO2. Infrared spectroscopy of the adsorbed pyrrole, temperature-programmed desorption of CO2, and the poisoning by a very weak Brönsted acid of methanol have revealed that the average strengths of the base sites on mesoporous alumina and sulfated mesoporous alumina are weaker than that on conventional γ-alumina like JRC-ALO-4, but that they have a small number of strong base sites which function even in scCO2 medium. It was found that the addition of a slight amount of THF cosolvent into scCO2 remarkably accelerates the Tishchenko reaction over sulfated mesoporous alumina; the reaction rate in the scCO2–THF medium was 1.5-fold and 2-fold faster than those in ordinary organic solvents such as benzene and THF and that in pure scCO2, respectively. The unique structures of mesoporous alumina and sulfated mesoporous alumina have been fully characterized by N2 adsorption–desorption measurements and XRD analyses. 相似文献
6.
Iwaoka M Komatsu H Katsuda T Tomoda S 《Journal of the American Chemical Society》2004,126(16):5309-5317
To investigate the nature of nonbonded Se...O interactions, three series of 2-substituted benzeneselenenyl derivatives [2-(CHO)C6H4SeX (1), 2-(CH2OH)C6H4SeX, (2), 2-(CH2OiPr)C6H4SeX (3); X = Cl, Br, CN, SPh, SeAr, Me] were synthesized. The 17O NMR absorption observed for 17O-enriched aldehydes 1 appeared upfield relative to benzaldehyde (PhCHO), while the opposite downfield shifts relative to benzyl alcohol (PhCH2OH) were observed for 17O-enriched alcohols 2 and ethers 3. The magnitude of both the upfield and the downfield shifts became larger as the electron-withdrawing ability of a substituent X increased. Quantum chemical calculations at the B3LYP level revealed that for all model compounds the most stable conformer has an intramolecular nonbonded Se.O interaction. Thus, the relative 17O NMR chemical shifts (DeltadeltaO) for 1-3 would reflect the strengths of the Se...O interactions. The natural bond orbital (NBO) analysis demonstrated that the stabilization energy due to an nO --> sigma Se-X orbital interaction (ESe...O) correlates with the Se...O atomic distance on a single curve irrespective of the type of the O atom. On the other hand, the atoms in molecules (AIM) analysis showed that the nonbonded Se...O interactions can be characterized by the presence of a bond critical point, the total energy density (HSe...O) of which decreases with strengthening of the interaction. The results suggested that Se...O interactions have a dominant covalent character rather than an electrostatic one. 相似文献
7.
Prof. Shingo Saito Toshiki Sakamoto Naoki Tanaka Ryo Watanabe Takuya Kamimura Kazuki Ota Kathryn R. Riley Keitaro Yoshimoto Yuiko Tasaki-Handa Masami Shibukawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10058-10067
In DNA aptamer selection, existing methods do not discriminate aptamer sequences based on their binding affinity and function and the reproducibility of the selection is often poor, even for the selection of well-known aptamers like those that bind the commonly used model protein thrombin. In the present study, a novel single-round selection method (SR-CE selection) was developed by combining capillary electrophoresis (CE) with next generation sequencing. Using SR-CE selection, a successful semi-quantitative and semi-comprehensive aptamer selection for thrombin was demonstrated with high reproducibility for the first time. Selection rules based on dissociation equilibria and kinetics were devised to obtain families of analogous sequences. Selected sequences of the same family were shown to bind thrombin with high affinity. Furthermore, data acquired from SR-CE selection was mined by creating sub-libraries that were categorized by the functionality of the aptamers (e. g., pre-organized aptamers versus structure-induced aptamers). Using this approach, a novel fluorescent molecular recognition sensor for thrombin with nanomolar detection limits was discovered. Thus, in this proof-of-concept report, we have demonstrated the potential of a “DNA Aptaomics” approach to systematically design functional aptamers as well as to obtain high affinity aptamers. 相似文献
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10.
Shimizu Y Shiokawa N Yamamoto N Kozuma M Kuga T Deng L Hagley EW 《Physical review letters》2002,89(23):233001
Propagation of a light pulse through a high-Q optical microcavity containing a few cold atoms (N<10) in its cavity mode is investigated experimentally. With less than ten cold rubidium atoms launched into an optical microcavity, up to 170 ns propagation lead time ("superluminal"), and 440 ns propagation delay time (subluminal) are observed. Comparison of the experimental data with numerical simulations as well as future experiments are discussed. 相似文献