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22.
Martín-Rodríguez M Nájera C Sansano JM de Cózar A Cossío FP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14224-14233
The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(S(a))-Binap-Au(tfa)}(2)] (Binap=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap-Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation. 相似文献
23.
Fuentes de Arriba Á Turiel MG Simón L Sanz F Boyero JF Muñiz FM Morán JR Alcázar V 《Organic & biomolecular chemistry》2011,9(24):8321-8327
Carbazole-based receptors functionalized with two sulfonamide groups have been synthesized and their properties as anion receptors have been evaluated. The receptor with bis(trifluoromethyl)aniline groups has shown a very high affinity for halide ions, especially remarkable as only two hydrogen bonds are formed in the complexes. (1)H NMR and fluorescence titrations have been carried out and binding constants up to 7.9 × 10(6) M(-1) have been reached. X-ray structures have been obtained and a modelling study has shown the possible reasons for the large affinity of these compounds for halide anions. 相似文献
24.
Berthe J Garcia JM Ocando E Kato T Saffon-Merceron N De Cózar A Cossío FP Baceiredo A 《Journal of the American Chemical Society》2011,133(40):15930-15933
The synthesis of the first isolable C-phosphino-Ge-aminogermyne, stabilized by a phosphine ligand, has been achieved. X-ray diffraction analysis indicates a quite long Ge-C bond whose length is between that of a single and a double bond but consistent with the theoretically predicted values for a germyne bearing π-donating substituents. The isomerization of this germyne derivative affords a new stable N-heterocyclic germylene through migration of the original phosphine ligand from germanium to the carbon center. 相似文献
25.
26.
Y. Rojas Martínez G. A. Pérez Alcázar H. Bustos Rodríguez D. Oyola Lozano 《Hyperfine Interactions》2005,161(1-4):191-195
In this work we report a comparative study of the magnetic and structural properties of Fe50Al50 alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation.
The Fe50Al50 sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy
phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball
mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic
sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that
prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make
more efficient the milling process. 相似文献
27.
New Insights into the Reactivity of Cisplatin with Free and Restrained Nucleophiles: Microsolvation Effects and Base Selectivity in Cisplatin–DNA Interactions
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Dr. Abel de Cózar Dr. Olatz Larrañaga Prof. Dr. F. Matthias Bickelhaupt Dr. Eider San Sebastián Elisabeth Ortega‐Carrasco Dr. Jean‐Didier Maréchal Prof. Agustí Lledós Prof. Dr. Fernando P. Cossío 《Chemphyschem》2016,17(23):3932-3947
The reactivity of cisplatin towards different nucleophiles has been studied by using density functional theory (DFT). Water was considered first to analyze the factors that govern the transformation of cisplatin into more electrophilic aquated species by using an activation‐strain model. It was found that the selectivity and reactivity of cisplatin is a delicate trade‐off between strain and interaction energies and that the second chloride is a worse leaving group than the first. When similar studies were carried out with imidazole, guanine (G), and adenine (A), it was found that in general the second nucleophilic substitution reactions have lower activation barriers than the first ones. Finally, simulations of the structural restrictions imposed by the DNA scaffold in intra‐ and interstrand processes showed that the geometries of the reaction products are nonoptimal with respect to the unrestrained A and G nucleophiles, although the energetic cost is not considerable under physiological conditions, which thus permits nucleophilic substitution reactions that lead to highly distorted DNA. 相似文献
28.
In order to study the structural and magnetic behaviour of FexMn0.70?xAl0.30 (0.40≤x≤0.70) alloys prepared by mechanical alloying, Mössbauer spectroscopy and X‐ray diffraction techniques have been employed. All the alloys were prepared in 24 h and, in addition, for x=0.45 milling times of 4, 8, 12, 16 and 24 h were considered. X‐ray diffraction showed that all samples exhibit bcc‐type reflections. A slight decrease in grain size and a slight increase in lattice parameter with increasing Mn content were observed. For x=0.45, an increase in grain size with milling time has been evidenced. For this composition and 4 h of milling, the more intensive peak (1?1?0) was fitted with three peaks corresponding to that of Mn, Fe and the alloy, respectively. For 12 h milling only bcc peaks of the alloy were obtained. As the Fe concentration was increased beyond x=0.50, a phase change from paramagnetic to ferromagnetic, as well as an increment in the mean hyperfine field with x, was detected. For x=0.45 and 4 h of milling we registered the presence of both a single line, corresponding to the alloy, and a hyperfine field distribution with peaks in 27.5 and 23 T, as well as peaks at lesser fields. These peaks are associated to Fe sites with two or more Al and/or Mn atoms as next neighbours. These results are in agreement with those obtained by X‐ray diffraction. 相似文献
29.
H. D. Colorado J. S. Trujillo Hernandez G. A. Pérez Alcázar Alberto Bolaños 《Hyperfine Interactions》2014,224(1-3):171-178
In this work the Cu0.91Fe0.09O nanocrystalline system was prepared via the co-precipitation method. Using Mössbauer Spectrometry, X-Ray Diffraction, Vibrating Sample Magnetometry, Thermogravimetry and Differential Scanning Calorimetry, we study the magnetic behavior, and the structural and calorimetric properties of this system. X-ray diffraction shows only the presence of the CuO structural monoclinic phase, suggesting that Cu atoms are substituted by Fe ones. This hypothesis was confirmed by Mössbauer spectrometry at room temperature, because it shows that the spectrum is formed by two doublets, which correspond to Fe?+?2 and Fe?+?3 sites. Hysteresis cycles obtained by vibrating sample magnetometry detect a soft ferromagnetic behavior at room temperature with coercive fields between 8 and 20 Oe. At T = 20 K the sample shows a hard-magnetic behavior. The thermogravimetry results show a Néel temperature (T N > 440 °C). The differential scanning calorimetry curve show two endothermic peaks in the 90–120 °C range. 相似文献
30.
Reboredo S Reyes E Vicario JL Badía D Carrillo L de Cózar A Cossío FP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7179-7188
The catalytic enantioselective [3+2] cycloaddition between azomethine ylides and α,β-unsaturated aldehydes catalyzed by α,α-diphenylprolinol has been studied in detail. In particular, the reaction has been extended to the use of 2-alkenylidene aminomalonates generated in situ as azomethine ylide precursors. These reactions lead to the formation of pyrrolidines containing a 5-alkenyl side chain with potential for chemical manipulation. Moreover, a detailed and concise computational study has been carried out to understand the exact nature of the mechanism of this reaction and especially the consequences derived from the incorporation of the chiral secondary amine catalyst on the reaction pathway. 相似文献