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91.
Dr. Xavier Deraet Dr. Jan Turek Prof. Mercedes Alonso Prof. Frederik Tielens Prof. Bert M. Weckhuysen Prof. Monica Calatayud Prof. Frank De Proft 《Chemphyschem》2023,24(6):e202200785
The rapidly growing interest for new heterogeneous catalytic systems providing high atomic efficiency along with high stability and reactivity triggered an impressive progress in the field of single-atom catalysis. Nevertheless, unravelling the factors governing the interaction strength between the support and the adsorbed metal atoms remains a major challenge. Based on periodic density functional theory (DFT) calculations, this paper provides insight into the adsorption of single late transition metals on a defect-free anatase surface. The obtained adsorption energies fluctuate, with the exception of Pd, between −3.11 and −3.80 eV and are indicative of a strong interaction. Depending on the considered transition metal, we could attribute the strength of this interaction with the support to i) an electron transfer towards anatase (Ru, Rh, Ni), ii) s-d orbital hybridisation effects (Pt), or iii) a synergistic effect between both factors (Fe, Co, Os, Ir). The driving forces behind the adsorption were also found to be strongly related to Klechkowsky's rule for orbital filling. In contrast, the deviating behaviour of Pd is most likely associated with the lower dissociation enthalpy of the Pd−O bond. Additionally, the reactivity of these systems was evaluated using the Fermi weighted density of states approach. The resulting softness values can be clearly related to the electron configuration of the catalytic systems as well as with the net charge on the transition metal. Finally, these indices were used to construct a model that predicts the adsorption strength of CO on these anatase-supported d-metal atoms. The values obtained from this regression model show, within a 95 % probability interval, a correlation of 84 % with the explicitly calculated CO adsorption energies. 相似文献
92.
Gaon I Turek TC Weller VA Edelstein RL Singh SK Distefano MD 《The Journal of organic chemistry》1996,61(22):7738-7745
Farnesyl pyrophosphate (FPP) is involved in a large number of cellular processes including the prenylation of transforming mutants of Ras proteins implicated in cancer. Photoactive analogs could provide useful information about enzyme active sites that bind farnesyl pyrophosphate; however, the availability of such compounds is extremely limited. Molecules that incorporate benzophenone moieties are attractive photoaffinity labeling reagents because of their useful photochemical properties. Here, the syntheses of two compounds, 3a and 3b, containing para- and meta-substituted benzoylbenzoates are described. Compounds 3a and 3b are competitive inhibitors (with respect to FPP) of yeast protein farnesyltransferase (PFTase) with K(i) values of 910 and 380 nM, respectively. Both compounds inactivate PFTase upon photolysis, resulting in as much as 44% inactivation of enzyme activity. Photolysis of PFTase in the presence of [(32)P]3a or of [(32)P]3b results in preferential labeling of the beta subunit, suggesting that this subunit is involved in prenyl group recognition. These compounds should be valuable tools for studying enzymes that utilize FPP as a substrate. 相似文献
93.
A study of the alkylation of 3% Re2O7/60%Al2O3-40%SiO2 catalyst using tetraethyllead (Et4Pb)(TEL) shows that the reaction time and temperature affect the catalyst activity and selectivity in the methyl erucate metathesis
reaction.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
94.
The longstanding open problem of approximating all singular vertex couplings in a quantum graph is solved. We present a construction in which the edges are decoupled; an each pair of their endpoints is joined by an edge carrying a δ potential and a vector potential coupled to the “loose” edges by a δ coupling. It is shown that if the lengths of the connecting edges shrink to zero and the potentials are properly scaled, the limit can yield any prescribed singular vertex coupling, and moreover, that such an approximation converges in the norm-resolvent sense. 相似文献
95.
Maxim A. Olshanskii Andriy Sokolov Stefan Turek 《Journal of Mathematical Fluid Mechanics》2010,12(4):485-502
In this paper a projection method for the Navier–Stokes equations with Coriolis force is considered. This time-stepping algorithm
takes into account the Coriolis terms both on prediction and correction steps. We study the accuracy of its semi-discretized
form and show that the velocity is weakly first-order approximation and the pressure is weakly order
\frac12\frac{1}{2} approximation. 相似文献
96.
Transition metal complex catalyzed cocyclotrimerization of protected alkynylpurine ribonucleosides 1 with various diynes 2 gave rise to a series of 6-arylpurine nucleosides 3 that were further deprotected to free nucleosides 4. Generally, the best yields of cyclotrimerizations were obtained with a catalytic system Ni(cod)2/2PPh(3). On the other hand, CoBr(PPh(3))3 proved to be a superior catalyst for cyclotrimerization of 1 with dipropargyl ether 2g. In addition, Ni catalysis is also suitable for direct cyclotrimerization of unprotected alkynylpurine ribonucleosides 5 to the corresponding 6-arylpurinylribosides 4. 相似文献
97.
M. Králík K. Turek V. Vondrá?ek J. Krása A. Velyhan M. Scholz I.M. Ivanova-Stanik 《Radiation measurements》2010,45(10):1245-1249
Paper presents results of measurements of neutron spectra with Bonner spheres spectrometer around radiotherapeutic linac producing undesirable photoneutrons and around plasma focus device PF-1000 in which neutrons are generated in 2H + 2H → n + 3He reaction. In the Bonner spheres an active detector, proportional counter filled with 3He, was replaced by passive one to avoid overloading of the active detector during very short period of neutrons generation. For the measurements around linac track detectors with 10B radiator were used and around plasma focus device pairs of TLDs (6LiF and 7LiF). 相似文献
98.
99.
100.
The catalytic activity of samples such as PPy(H4SiW12O40), PPy(H5PMo10V2O40), PPy(H2Fe(III)PMo10V2O40), PPy(H3Cu(II)PMo10V2O40) has been examined in two different test reactions. The acid-base and oxidation-reduction properties were studied using the conversion of isopropyl alcohol to propene and acetone. Redox ability of catalysts was examined in the reaction of oxidation of allyl alcohol to glycidol. It was found that the activity of catalysts in the oxidation of allyl alcohol increases as the oxidation properties determined from the conversion of isopropyl alcohol increase. It was also observed that stronger oxidation-reduction properties of the catalyst result in a high rate of the consecutive reaction of glycidol to 3-hydroxypropanone.The phase composition of catalysts was determined by means of X-ray diffraction (XRD). 相似文献