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排序方式: 共有167条查询结果,搜索用时 187 毫秒
101.
Mishima O 《Physical review letters》2000,85(2):334-336
According to the liquid-liquid critical-point hypothesis about water, two liquid waters exist at low temperatures and are supposed to be merged at a critical point. The low-temperature metastable melting curves of D2O ices have been measured. It is found that the melting curve of D2O ice III is smoothly curved around 25 MPa and 238 K, whereas the melting curve of D2O ice IV undergoes an abrupt change of slope at 100 MPa and 220 K. This is consistent with the existence of a liquid-liquid critical point in the region between the melting curve of D2O ice III and the melting curve of D2O ice IV. 相似文献
102.
Nagaya K Lu HF Mineo H Mishima K Hayashi M Lin SH 《The Journal of chemical physics》2007,126(2):024304
Combining our generalized Keldysh theory [Sov. Phys. JETP 20, 1307 (1965)] with the molecular orbital theory, the authors theoretically study tunneling ionizations of neutral benzene in intense linearly polarized Ti:sapphire laser fields (800 nm). They consider the ionizations from the highest occupied molecular orbitals (HOMOs) of the ground electronic state. The double degeneracy of the HOMOs is properly taken into account. In the theory, molecular ionizations consist of the individual ionizations from each atom and the quantum interferences between them. The theory reproduces the experimental data well. The authors also show that the polarization dependence of the ionization rates is strongly influenced by the quantum interferences. 相似文献
103.
Both isomeric enols on ring carbonyl (5b) and on amide carbonyl (6b) derived from N-p-methoxyphenyl-2-carbamido-1,3-indandione (4b) were isolated, and their X-ray structures were determined. X-ray diffraction of the N-o,p-dimethoxy analogue indicated a disorder ascribed to the presence of a 6:4 mixture of 5c and 6c. Calculation (B3LYP/6-31+G*) gave good agreement with observed geometries. The calculated energies indicated that enols 6 are more stable by <1 kcal/mol than enols 5 and much more stable than amides 4. 相似文献
104.
Than S Maeda H Irie M Itoh S Kikukawa K Mishima M 《The journal of physical chemistry. A》2007,111(27):5988-5994
Free energy changes (DeltaG degrees , copper cation basicity) for the reaction L(2)Cu(+) = Cu(+) + 2L were obtained in the gas phase for substituted pyridines based on the measurement of ligand-exchange equilibria in a Fourier transform ion cyclotron resonance (FT-ICR) spectrometer. For 3- and 4-substituted pyridines, the relative copper cation basicities (DeltaCCB[L(2)Cu(+)]) were linearly correlated with the corresponding gas-phase proton basicities (DeltaGB) with a slope of 1.01. On the basis of a linear relationship between the calculated copper cation basicities of dimeric and monomeric complexes at MP2/6-311+G(2p,2d)//B3LYP/6-311G*, DeltaCCB[L(2)Cu(+)](calcd) = 1.54DeltaCCB[LCu(+)](calcd), the substituent effect on the DeltaCCB for the first ligand was estimated to be 0.66 times smaller than the corresponding DeltaGB. A comparison with the corresponding results for other Lewis cation basicity of the pyridine system showed that the magnitude of the substituent effect decreases in the order H(+) (1.00) > Me(3)Si(+) (0.95) > Cl(+) (0.83) > Cu(+) (0.66) > Li(+) (0.47). This change was associated with the natural charges at the Lewis cation moiety and the natural atomic orbital (NAO) bond order of the M+-N bond of the complex ion, indicating the decrease in covalent character of the M(+)-N bond in this order. Furthermore, when a variety of neutral bases such as amines, carbonyl compounds, and ethers were included in a comparison between CCB[L(2)Cu(+)] and GB, it was found that there is a good linear relationship with significant deviations of small molecules and bulky tributylamine, which is attributed to their different steric environment at the binding sites from others, while there is no simple linear relationship with the lithium cation basicities (LCB). The similarity of the substituent effect between CCB[L(2)Cu(+)] and GB reflects the covalent character in the Cu(+) interaction. In conclusion, although the ionic (ion-dipole interaction) nature of the Cu(+) interaction results in a smaller substituent effect than that for the protonation, the covalent nature also plays an important role in the Cu(+) interaction with neutral molecules. 相似文献
105.
Eri Mishima Shigeru Yamago 《Journal of polymer science. Part A, Polymer chemistry》2012,50(11):2254-2264
Random and alternating copolymerizations of acrylates, methacrylates, acrylonitorile, and acrylamides with vinyl ethers under organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization (TERP, SBRP, and BIRP, respectively) have been studied. Structurally well‐controlled random and alternating copolymers with controlled molecular weights and polydispersities were synthesized. The highly alternating copolymerization occurred in a combination of acrylates and vinyl ethers and acrylonitorile and vinyl ethers by using excess amount of vinyl ethers over acrylates and acrylonitorile. On the contrary, alternating copolymerization did not occur in a combination of acrylamides and vinyl ethers even excess amount of vinyl ethers were used. The reactivity of polymer‐end radicals to a vinyl ether was estimated by the theoretical calculations, and it was suggested that the energy level of singly occupied molecular orbital (SOMO) of polymer‐end radical species determined the reactivity. By combining living random and alternating copolymerization with living radical or living cationic polymerization, new block copolymers, such as (PBA‐alt‐PIBVE)‐block‐(PtBA‐co‐PIBVE), PBA‐block‐(PBA‐alt‐PIBVE), and (PTFEA‐alt‐PIBVE)‐block‐PIBVE, with controlled macromolecular structures were successfully synthesized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
106.
107.
Masako Yamada Yoshihisa Iwashita Masahiro Ichikawa Takanori Sugimoto Hiromu Tongu Hiroshi Fujisawa Hirohiko M. Shimizu Takashi Ino Kenji Mishima Kaoru Taketani Tamaki Yoshioka Suguru Muto Takahiro Morishima Takayuki Oku Jun-ichi Suzuki Takenao Shinohara Kenji Sakai Hiromi Sato Katsuya Hirota Yoshie Otake Yoshichika Seki Shinsuke Kawasaki Sachio Komamiya Yoshio Kamiya Hidetoshi Otono Satoru Yamashita Peter Geltenbort 《Physica B: Condensed Matter》2009,404(17):2646-2651
Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ=40 Å were focused by the PMSx at a focal length of about 0.5 m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure. 相似文献
108.
M. Fukuda T. Mishima N. Nakayama T. Masuda 《Applied physics. B, Lasers and optics》2010,100(2):377-382
The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring
CO2-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by
monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation
under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after
changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring
error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength
differ with the rate. 相似文献
109.
Yuichi Oshima Takehiro YoshidaKazutoshi Watanabe Tomoyoshi Mishima 《Journal of Crystal Growth》2010,312(24):3569-3573
We investigated the properties of Ge-doped, high-quality bulk GaN crystals with Ge concentrations up to 2.4×1019 cm−3. The Ge-doped crystals were fabricated by hydride vapor phase epitaxy with GeCl4 as the dopant source. Cathodoluminescence imaging revealed no increase in the dislocation density at even the highest Ge concentration, with values as low as 3.4×106 cm−2. The carrier concentration, as determined by Hall measurement, was almost identical to the combined concentration of Ge and unintentionally incorporated Si. The electron mobilities were 260 and 146 cm2 V−1 s−1 for n=3.3×1018 and 3.35×1019 cm−3, respectively; these values are markedly larger than those reported in the past for Ge-doped GaN thin films. The optical absorption coefficient was quite small below the band gap energy; it slightly increased with increase in Ge concentration. Thermal conductivity, estimated by the laser-flash method, was virtually independent of Ge concentration, maintaining an excellent value around 2.0 W cm−1 K−1. Thermal expansion coefficients along the a- and m-axes were approximately constant at 5.0×10−6 K−1 in the measured doping concentration range. 相似文献
110.
Pseudo-first-order rate constants (k(obsd)) for reactions of 4-nitrophenyl salicylate (7) with alkali metal ethoxides (EtOM, M = K, Na, and Li) in anhydrous ethanol have been measured spectrophotometrically. Interestingly, the k(obsd) value decreases significantly as the concentration of EtOM increases. Because the phenolic moiety of substrate 7 would be deprotonated and exist as an anionic form (i.e., 7(-)) under kinetic conditions, the ground-state stabilization of 7(-) through formation of a six-membered cyclic complex with M(+) (i.e., 8) is proposed to be responsible for the decreasing k(obsd) trend. The k(obsd) value at a given concentration of EtOK increases steeply upon addition of [18]crown-6 ether (18C6) up to [18C6]/[EtOK] = 1 in the reaction mixture and then remains relatively constant thereafter. In contrast, k(obsd) decreases upon addition of salts (e.g., LiClO(4) or KSCN) to the reaction mixture, which indicates that M(+) ions inhibit the reaction. However, in the presence of 18C6, the k(obsd) value is independent of the concentration of EtOK but remains constant, which indicates that the reaction proceeds through a unimolecular mechanism in the presence of the complexing agent. Although two conceivable unimolecular pathways (formation of ketene 9 and lactone 10) can account for the kinetic results, the reaction has been concluded to proceed via formation of ketene 9 as the reactive intermediate on the basis of theoretical calculations. 相似文献