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排序方式: 共有424条查询结果,搜索用时 390 毫秒
91.
Yang Y Weng Z Muratsugu S Ishiguro N Ohkoshi S Tada M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(4):1142-1153
A catalyst surface with an active metal site, a shape-selective reaction space, and an NH(2) binding site for o-fluorobenzophenone was designed and prepared by the molecular imprinting of a supported metal complex on a SiO(2) surface. A ligand of a SiO(2)-supported Ru complex that has a similar shape to the product of o-fluorobenzophenone hydrogenation was used as a template. An NH(2) binding site for o-fluorobenzophenone was spatially arranged on the wall of a molecularly imprinted cavity with a similar shape to the template. The structures of the SiO(2)-supported and molecularly imprinted Ru catalysts were characterized in a step-by-step manner by means of solid-state magic angle spinning (MAS) NMR, XPS, UV/Vis, N(2) adsorption, XRF, and Ru K-edge EXAFS. The molecularly imprinted Ru catalyst exhibited excellent shape selectivity for the transfer hydrogenation of benzophenone derivatives. It was found that the NH(2) binding site on the wall of the molecularly imprinted cavity enhanced the adsorption of o-fluorobenzophenone, of which the reduction product was imprinted, whereas there was no positive effect in the case of o-methylbenzophenone, which cannot interact with the NH(2) binding site through hydrogen bonding. 相似文献
92.
We studied the effects of pH on the pressure–temperature dependence of coil–collapse transition for aqueous solutions of
copolymers of N-isopropylacrylamide and acrylic acid (Ac). At low pressures, the transition temperature (T
tr) increased with pressure, but T
tr decrease with increasing pressure at pressures higher than 50–100 MPa. By increasing the pH, the transition contour shifted
to a higher temperature. When the Ac content was increased, the effects of pH became more evident. From a calorimetric study
at atmospheric pressure, ΔH
tr was found to become smaller by increasing the portion of the ionized residues in the copolymer. The ratio to the van't Hoff
enthalpy changes became larger with an increase in pH, which indicated that the production of charge decreased the cooperative
domain size.
Received: 19 July 1999 /Accepted in revised form: 7 September 1999 相似文献
93.
Isanu Nagata Kazuhiro Tamura Kaoru Tada Fumihiro Nishikawa 《Journal of solution chemistry》2000,29(9):815-835
An association model is presented to describe vapor–liquid equilibria,liquid–liquid equilibria, and excess enthalpies of binary and ternary liquid solutionscontaining alcohols, aniline, and/or acetonitrile using the concepts of linearself-association of associated components and of solvation between unlike molecules.Calculated results also show that the model works well in representing thethermodynamic properties for alcohol + aniline, alcohol + acetonitrile, andalcohol + alcohol mixtures. 相似文献
94.
Joo-Hyong Noh Shigehiko Hasegawa Tatsuya Suzuki Taro Arakawa Kunio Tada Hajime Asahi 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):482
The five-layer asymmetric coupled quantum well (FACQW) is a new potential-tailored quantum well that is promising for ultra-fast and ultra-low-voltage optical modulators and switches. FACQW samples were grown by the migration-enhanced epitaxy (MEE) and the conventional molecular beam epitaxy methods with steep and flat heterointerfaces in the monolayer accuracy. They were characterized with the cross-sectional scanning tunneling microscopy (STM). In the cross-sectional STM image, double-stripe structures with different contrast were observed. The stripe area corresponds to the FACQW (about 10 nm wide), sandwiched with the AlGaAs barrier layers (15 nm wide). A dark line observed at the middle of the FACQW stripe area corresponds to the 3-monolayer-thick AlAs layer. The cross-sectional STM images of the high-quality heterointerface FACQW structures were successfully observed for the samples grown by the MEE method. More detailed studies of this kind of cross-sectional STM observations will be very effective to obtain the optimized growth conditions for fine and complicated ultra-thin structures. 相似文献
95.
Yuichiro Tada Masakatsu Ueno Noriaki Tsuchihashi Kiyoshi Shimizu 《Journal of solution chemistry》1994,23(9):973-987
The limiting molar conductances ° of potassium deuteroxide KOD in D2O and potassium hydroxide KOH in H2O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD– (OH–) and a D3O+ (H3O+) ion. The excess conductances of the OD– ion in D2O and the OH– ion in H2O,
E
0
(OD-) and
E
0
(OH-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances,
E
0
(D+) and
E
0
(H+). However, the temperature effect on the excess conductance is larger for the OD–(OH–) ion than for the D3O+ (H3O+) ion but the pressure effect is much smaller for the OD– (OH–) ion than for the D3O+ (H3O+) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD– (OH–) ion than for the D3O+ (H3O+) ion. Concerning the isotope effect, the value of
E
0
(OH-)/
E
0
(OD-) deviates considerably from
at each temperature and pressure in contrast with that of
E
0
(H+)/
E
0
(D+), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD– (OH–) or the D3O+ (H3O+) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D2O and H2O, and their variations with temperature, pressure, and isotope. 相似文献
96.
97.
Hiroaki Tada Tetsuji Ishida Ayako Takao Seishiro Ito Sudip Mukhopadhyay Tomoki Akita Koji Tanaka Hisayoshi Kobayashi 《Chemphyschem》2005,6(8):1537-1543
TiO2 particles loaded with silver nanoparticles with a mean diameter of 1.5 nm exhibit a high photocatalytic activity (84 % conversion after 1 h irradiation) for the reduction of nitrobenzene to aniline with 100 % selectivity in the presence of CH3OH (concentration=100 mM). High-resolution transmission electron microscopic studies of Pt-photodeposited Ag/TiO2 demonstrate that the Ag nanoparticles act as reduction sites in the photocatalytic reaction. Both spectroscopic measurements and density functional theory (DFT) calculations reveal that nitrobenzene is selectively adsorbed onto the Ag surfaces of Ag/TiO2 via partial electron transfer from Ag to nitrobenzene, whereas the interaction between aniline and Ag/TiO2 is weak. The kinetic analysis indicates that the recombination between the electrons flowing into the Ag nanoparticle and the holes left in the TiO2 valence band is significantly suppressed, particularly in the presence of CH3OH. The high activity and selectivity in the present Ag/TiO2-photocatalyzed reduction are rationalized in terms of the charge separation efficiency, the selective adsorption of the reactants on the catalyst surfaces, and the restriction of the product readsorption. 相似文献
98.
n-type organic field-effect transistors with very high electron mobility based on thiazole oligomers with trifluoromethylphenyl groups 总被引:1,自引:0,他引:1
Ando S Murakami R Nishida J Tada H Inoue Y Tokito S Yamashita Y 《Journal of the American Chemical Society》2005,127(43):14996-14997
Novel thiazole oligomers and thiazole/thiophene co-oligomers with trifluoromethylphenyl groups were developed as n-type semiconductors for OFETs. They showed excellent n-type performances with high electron mobilities. A 5,5'-bithiazole with trifluoromethylphenyl groups forms a closely packed two-dimensional columnar structure leading to a high performance n-type FET. The electron mobility was enhanced to 1.83 cm2/Vs on the OTS-treated substrate. 相似文献
99.
100.
Synthesis of 8-hydroxypurine nucleosides 总被引:4,自引:0,他引:4