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281.
Microwave spectra of the trans and gauche isomers of ethyl fluorosilane and their eleven isotopically substituted species have been measured. The rs structures of the two isomers were determined from the observed moments of inertia. The molecular structures found for the two isomers in the present study are compared with those of analogous molecules. Dipole moments of the two isomers were determined by Stark-effect measurements and are also compared with those of analogous molecules. The energy difference between the trans and gauche isomers was obtained from the relative intensity measurements of the spectra and the barrier to internal rotation of the methyl group for the gauche isomer was obtained from the A—E splittings of the spectra in the first excited methyl torsional state. The V3 value was 2775 ± 25 cal mol?1. 相似文献
282.
283.
Taichi Abe Kazuteru Shinozaki Noriaki Ikeda Takayoshi Suzuki 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):m456-m458
In the title compound, [Pt(C18H15N2)Cl], the PtII centre adopts a distorted square‐planar coordination geometry due to the pincer‐type monoanionic N–C–N tridentate ligand. The planar complexes stack viaπ–π interactions to form two‐dimensional accumulated sheets. This packing pattern is in contrast to that in related pincer‐type N–C–N complexes, which exhibit a one‐dimensional columnar stacking. 相似文献
284.
Tadashi Saito Taichi Miura Atsushi Shinohara Junichiro Shintai Eugene Taniguchi Michiaki Furukawa Kazuhiro Takesako Nobutsugu Imanishi Hisakazu Muramatsu Yoshio Yoshimura Hiroshi Baba Hidekazu Doe 《Hyperfine Interactions》1994,84(1):193-198
Atomic capture probabilities of negative pions in some metal hydrides were measured. The capture by a hydrogen atom was detected by means of a pair of the annihilation rays of 0 which had been produced by the charge-exchange reaction of – with the capturing hydrogen nucleus (proton). This method ensures a high sensitivity and reliability of the measurements. The probabilities obtained were in agreement with previous measurements except for palladium hydride, which showed a much smaller probability than that given in the literature. The atomic capture of – is well described in the framework of the large mesic molecular model, in which the proportionality constant reflects the chemical states of the capturing atoms and also the neighboring ones. 相似文献
285.
Atsushi Shinohara Toshiharu Muroyama Junichirou Shintai Eugene Taniguchi Tadashi Saito Taichi Miura Nobutsugu Imanishi Yoshio Yoshimura Michiaki Furukawa 《Hyperfine Interactions》1994,84(1):569-574
The transfer of negative pions captured by hydrogen to heavier atoms has been investigated in a series of alcohols by measuring both 2 rays from 0 decay and pionic X rays. Capture rates for the pionic hydrogen of different chemical states in the molecule were determined from a comparison between the data for the ordinary compound and the deuterated one. The external transfer in the condensed phase was revealed by the dependence of the capture rate of hydrogen on the number of carbon atoms in the alkyl group. The influence of the chemical structure on the transfer process is discussed with respect to the large difference between the relative transfer rates,
C=1.5±0.2 and
O = 4.5±0.4, corresponding to carbon and oxygen, respectively. 相似文献
286.
Taichi Sugai 《Tetrahedron letters》2007,48(16):2931-2934
Alkyl groups at aromatic nucleus and alcohols were found to be photo-oxidized to the corresponding carboxylic acid in the presence of catalytic allylbromide. 相似文献
287.
A titanium BINOLate catalyzed asymmetric 1,3-dipolar cycloaddition reaction between alpha-substituted acroleins and alkyl diazoacetates has been developed. With this methodology in hand, chiral 2-pyrazolines containing a quaternary stereogenic center were obtained in high to excellent enantioselectivities (up to 95% ee). The synthetic utility of the optically enriched 2-pyrazoline thus obtained was demonstrated in the short synthesis of manzacidin A. 相似文献
288.
A convergent synthesis of kwakhurin (5), a characteristic estrogen-like isoflavone of Pueraria mirifica(Leguminosae), is described. Isoflavone skeleton 31 was constructed by Suzuki-Miyaura coupling of 3-bromochromone 26 (AC-ring) and arylboronic acid 30 (B-ring) in the presence of TBAB as an additive. Microwave-assisted coupling was also examined, but did not improve the yield. Baeyer-Villiger oxidation, followed by propargylation and reduction afforded 1,1-dimethylallyl ether 37. 6'-Prenylisoflavone 34 was obtained in high yield by Claisen rearrangement of 37 in N,N-diethylaniline. On the other hand, 1,3-rearrangement of prenyl ether 33 with clay gave 34 in poor yield. Successive methylation of 34 and deprotection yielded the target kwakhurin (5) in 12% overall yield from 2,4-dihydroxybenzaldehyde (23). 相似文献
289.
For an orbifold M we define a new homology group, called t-singular homology group t-Hq(M) by using singular simplicies intersecting ‘transversely’ with ΣM. The rightness of this homology group is ensured by the facts that the 1-dimensional homology group t-H1(M) is isomorphic to the abelianization of the orbifold fundamental group π1(M,x0). If M is a manifold, t-Hq(M) coincides with the usual singular homology group. We prove that it is a ‘b-homotopy’ invariant of orbifolds and develop many algebraic tools for the calculations. Consequently we calculate the t-singular homology groups of several orbifolds. 相似文献
290.
[reaction: see text] A diastereoselective tandem Stille-oxa-electrocyclization reaction provides access to the core of the diterpenoid natural product saudin. Additionally, this new reaction sequence was extended to the convergent preparation of related polycyclic pyran systems. 相似文献