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91.
Molecular structure dependences of the coefficients of molecular packing (Kp) and the intrinsic birefringence (Δn0) were investigated for aromatic polyimides (PIs) using a method based on the modified Lorentz–Lorenz equation and the Vuks equation. This method needs only average refractive indices and polarizability tensors ( ) for PI repeating units. αˆ was calculated using the density functional theory at the B3LYP/6-31+G(d) theory level that was confirmed as optimal for PI repeating units. Because bent or kinked structures in main chain hinder the ordering of polymer chains, Kp decreases in cases that ether linkages are introduced in the main chain and that kinked-structured dianhydrides are used. Introduction of side groups, trifluoromethyl ( CF3) groups in particular, also causes decreases in Kp. On the other hand, the estimated values of Δn0 are proportional to the calculated anisotropy in αˆ (Δα/Vvdw), thus Δn0 can be well predicted by computation. The values of Δα/Vvdw are decreased not only by bent structures in the main chain (e.g., ether linkage), presence of side groups, but also by large fractions of imide rings in the polymer structures. The estimated values of Δn0 range from 0.338 to 0.470, which are much larger than the reported ones for optically transparent conventional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2354–2366, 2004 相似文献
92.
Using the in situ measurements of the surface potential built across the evaporated liquid crystalline 4-n-pentyl-4'-cyanobiphenyl (5CB) films on metal electrodes with different work functions, we studied the cooperative molecular field effect (CMFE) that assists carrier injection from electrodes and the induced orientational reordering in evaporated liquid crystalline molecules on metals. The surface potential increased, and then became constant after the 5CB monomolecular layer was formed. It was shown that the CMFE accompanying orientational reordering accounts for the metal work function dependence of the surface potential. Finally, the orientational reordering is discussed in terms of the anchoring energy. 相似文献
93.
Shirakawa M Fujita N Tani T Kaneko K Ojima M Fujii A Ozaki M Shinkai S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(15):4155-4162
8-quinolinol/copper(II)-, palladium(II)-, and platinum(II)-chelate-based organogelators (1 M) and their nongelling reference compounds (2 M) were synthesized. Complexes 1 M could gelate various organic solvents at very low concentrations. Electron microscope measurements gave visual images of well-developed fibrous structures characteristic of low-molecular-weight organogels. UV/Vis and FTIR spectroscopy revealed that the good gelation ability of 1 M arises from the pi-pi interactions of the chelate moieties and the hydrogen-bond interactions among the amide groups. Very interestingly, field emission performances of the nanofibers prepared from the 1 M gels are evidently different depending on the electronic states of the three kinds of central metals. In addition, the 1 Pt gel shows unique thermo- and solvatochromism of visible and phosphorescent color in response to a sol-gel phase transition. Furthermore, the 1 Pt gel possesses an attractive ability to inhibit dioxygen quenching of excited triplet states, which increases the phosphorescence quantum yield of this gel. This effect is attributed to the isolation effect of the phosphorescent chelate moiety from the dioxygen-containing solution phase. 相似文献
94.
95.
M. Fukushima H. Tamate S. Sato S. Terui T. Mitsugashira 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(3):595-599
The normal concentration levels of trace metals in several kinds of tissues of even-toed ungulates have been determined by
instrumental neutron activation analysis, photon activation analysis, and flame atomic absorption spectrometry. In the present
work the concentrations of 13 elements (Ag, Br, Ca, Co, Cu, Fe, Mg, Mn, Mo, Na, Rb, Se, and Zn) were analyzed. 相似文献
96.
Potential of digital holography in particle measurement 总被引:14,自引:0,他引:14
This paper describes the potential power of digital holography in particle measurement and its expected development in the near future. In digital holography, image reconstruction is carried out numerically on a computer using observed hologram patterns and some quantitative information can be derived from the reconstructed images. In this paper, the basic concept and procedure of digital in-line holography are shown mainly for particle depth measurement and the performance test results obtained in numerical simulations and experiments are demonstrated to examine the potential of the present method. 相似文献
97.
98.
Sumino Y Kitahata H Shinohara Y Yamada NL Seto H 《Langmuir : the ACS journal of surfaces and colloids》2012,28(7):3378-3384
The motion of an oil-water interface that mimics biological motility was investigated in a Hele-Shaw-like cell where elastic surfactant aggregates were formed at the oil-water interface. With the interfacial motion, millimeter-scale pillar structures composed of the aggregates were formed. The pillars grew downward in the aqueous phase, and the separations between pillars were roughly equal. Small-angle X-ray scattering using a microbeam X-ray revealed that these aggregates had nanometer-scale lamellar structures whose orientation correlated well with their location in the pillar structure. It is suggested that these hierarchical spatial structures are tailored by the spontaneous interfacial motion. 相似文献
99.
100.
Masuda K Sakiyama N Tanaka R Noguchi K Tanaka K 《Journal of the American Chemical Society》2011,133(18):6918-6921
It has been established that a cationic rhodium(I)/(R)-H(8)-BINAP or (R)-Segphos complex catalyzes two modes of enantioselective cyclizations of γ-alkynylaldehydes with acyl phosphonates via C-P or C-H bond cleavage. The ligands of the Rh(I) complexes and the substitutents of both γ-alkynylaldehydes and acyl phosphonates control these two different pathways. 相似文献