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排序方式: 共有867条查询结果,搜索用时 31 毫秒
831.
Fangjie Zhu Dr. Tatsuya Nishimura Dr. Takeshi Sakamoto Dr. Hidekazu Tomono Dr. Hiroki Nada Prof. Dr. Yasushi Okumura Prof. Dr. Hirotsugu Kikuchi Prof. Dr. Takashi Kato 《化学:亚洲杂志》2013,8(12):3002-3009
Thin‐film growth of aragonite CaCO3 on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg2+ into a supersaturated solution of CaCO3. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg2+ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg2+. Molecular dynamics simulation of the CaCO3 precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg2+. The role for ionic additives in the crystallization of CaCO3 on organic templates obtained in this study may provide useful information for the development of functional hybrid materials. 相似文献
832.
Miyabi Hiyama Hidefumi Akiyama Toshimitsu Mochizuki Kenta Yamada Nobuaki Koga 《Photochemistry and photobiology》2014,90(4):820-828
The whole pathways for photoluminescence, which include absorption, relaxation and emission, of firefly luciferin in aqueous solutions of different pH values with different photoexcitation energies were theoretically investigated by considering protonation/deprotonation. It is experimentally known that the color of fluorescence changes from green to red with a decrease in the photoexcitation energy. We confirmed with the theoretical analysis that the peak energy shift in the fluorescence spectra with varying photoenergies is due to a change in photoluminescence pathway. When the photoexcitation energy is decreased, the red emission from a monoanion form of firefly luciferin with carboxylate and phenolate groups and N‐protonated thiazoline ring occurs irrespective of the pH values. However, because the species abundant in the solution and those excited by the photon depend on the solution pH, the pathway leading to the monoanion form changes with the solution pH. 相似文献
833.
Rudi Agus Setiawan Hiromasa Nishikiori Nobuaki Tanaka Tsuneo Fujii 《Photochemistry and photobiology》2014,90(5):1004-1011
The titania and dye‐dispersing titania electrodes were prepared by a nitric acid‐catalyzed sol‐gel process. The dye‐dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo‐cyclic voltammetry (Photo‐CV) and photoelectric measurements of the dye‐dispersing titania electrodes were conducted to clarify the factors changing the conduction band edge of the titania and the open‐circuit voltage (Voc) of the electrodes. The remaining nitrate ions caused a negative shift of conduction band edge of the titania of the dye‐dispersing titania. The conduction band edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye‐titania complex formation on the titania particle surface. The effect of the dye‐titania complex formation on the shift in the titania conduction band edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone‐like groups of the dye. The shift in the titania conduction band edge corresponded to the change in the Voc value. 相似文献
834.
Matsumori N Kasai Y Oishi T Murata M Nomura K 《Journal of the American Chemical Society》2008,130(14):4757-4766
6-F-cholesterol was reported to exhibit biological and interfacial properties similar to unmodified cholesterol. We have also found that 6-F-cholesterol mimicked the cholesterol activity observed in the systems of amphotericin B and lipid rafts. However, to use 6-F-cholesterol as a molecular probe to explore molecular recognition in membranes, it is indispensable to have detailed knowledge of the dynamic and orientation properties of the molecule in membrane environments. In this paper, we present the molecular orientation of 6-F-cholesterol (30 mol %) in dimyristoylphosphatidylcholine (DMPC) bilayers revealed by combined use of 19F chemical shift anisotropy (CSA), 2H NMR, and C-F rotational echo double resonance (REDOR) experiments. The axis of rotation of 6-F-cholesterol was shown to be in a similar direction to that of cholesterol in DMPC bilayers, which is almost parallel to the long axis of the molecular frame. The molecular order parameter of 6-F-cholesterol was determined to be ca. 0.85, which is within the range of reported values of cholesterol. These findings suggest that the dynamic properties of 6-F-cholesterol in DMPC are quite similar to those of unmodified cholesterol; therefore, the introduction of a fluorine atom at C6 has virtually no effect on cholesterol dynamics in membranes. In addition, this study demonstrates the practical utility of theoretical calculations for determining the 19F CSA principal axes, which would be extremely difficult to obtain experimentally. The combined use of quantum calculations and solid-state 19F NMR will make it possible to apply the orientation information of 19F CSA tensors to membrane systems. 相似文献
835.
Yatsuhashi T Ichikawa S Shigematsu Y Nakashima N 《Journal of the American Chemical Society》2008,130(46):15264-15265
The five and possibly seven-photon fluorescence was observed for organic molecules in solution for the first time. A high-intensity laser enabled us to measure the properties of the high and any-order processes, and the emission could be directly visualized by the eye. These results showed that the common two-photon microscope could be upgraded to the higher order multiphoton microscope by choosing suitable excitation wavelengths. The multiphoton absorption cross sections differed by a factor of 10(33) as the order of the multiphoton process increased. 相似文献
836.
Mitsuo Shoji Hiroshi Isobe Toru Saito Hirotaka Yabushita Kenichi Koizumi Yasutaka Kitagawa Shusuke Yamanaka Takashi Kawakami Mitsutaka Okumura Masayuki Hagiwara Kizashi Yamaguchi 《International journal of quantum chemistry》2008,108(4):631-650
A first principle investigation has been carried out for intermediate states of the catalytic cycle of a cytochrome P450. To elucidate the whole catalytic cycle of P450, the electronic and geometrical structures are investigated not only at each ground state but also at low‐lying energy levels. Using the natural orbital analysis, the nature of chemical bonds and magnetic interactions are investigated. The ground state of the Compound 1 ( cpd1 ) is calculated to be a doublet state, which is generated by the antiferromagnetic coupling between a triplet Fe(IV)?O moiety and a doublet ligand radical. We found that an excited doublet state of the cpd1 is composed of a singlet Fe(IV)?O and a doublet ligand radical. This excited state lies 20.8 kcal mol?1 above the ground spin state, which is a non‐negligible energy level as compared with the activation energy barrier of ΔE# = 26.6 kcal mol?1. The reaction path of the ground state of cpd1 is investigated on the basis of the model reaction: 3O(3p) + CH4. The computational results suggest that the reactions of P450 at the ground and excited states proceed through abstraction (3O‐model) and insertion (1O‐model) mechanisms, respectively. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
837.
Toru Saito Takashi Kawakami Shusuke Yamanaka Mitsutaka Okumura 《Molecular physics》2016,114(3-4):431-439
ABSTRACTIn this paper, we have investigated the catalytic mechanism of rat liver arginase using a quantum mechanics/molecular mechanics (QM/MM) approach. The enzyme catalyses the hydrolysis of L-arginine (L-Arg) to generate L-ornithine and urea. The reaction mechanism proposed by the previous experimental studies is well reproduced by the QM/MM computations. The explicit treatment of the protein environment suggests that Glu277 fulfil its role in stabilising and orienting L-Arg before nucleophilic attack by the bridging hydroxide in the first step. We have also found that the proton transfer step involving a hydrogen bond switch is the rate-limiting step. The activation energy is computed to be 9.0 and 5.9 kcal/mol at the UB3LYP-D3/CHARMM22 and UBHandHLYP-D3/CHARMM22 levels, which are comparable to the observed activation barrier of 7.2 kcal/mol. 相似文献
838.
Hiroshi Kominami Katutoshi Sumida Kazuto Yamamoto Nobuaki Kondo Keiji Hashimoto Yoshiya Kera 《Research on Chemical Intermediates》2008,34(5-7):587-601
Various metal chloride-modified titanium(IV) oxide (TiO2) (MCMT) samples were prepared by loading metal chloride on commercial TiO2 nanoparticles (Ishihara ST-01) having a large specific surface area and used for photoinduced oxidative removal of nitrogen oxides (NO x ) in air under irradiation of visible light and/or ultraviolet (UV) light. The NO x removal activity of MCMT samples under photoirradiation from a blue fluorescent lamp (BFL) with a UV cut filter decreased in the following order: RhCl3/ST-01>H2PtCl6/ST-01>RuCl3/ST-01>ST-01>IrCl4/ST-01>HAuCl4/ST-01, indicating that RhCl3. H2PtCl6 and RuCl3 fixed on TiO2 effectively worked as photosensitizers for NO x removal. NO x was almost quantitatively fixed as nitrate on RhCl3/ST-01 photoirradiated with BFL or blue light-emitting diodes. Under irradiation of both visible light and UV light from a white fluorescent lamp, RhCl3/ST-01 exhibited a higher level of removal of NO x and a much lower level of release of nitrogen dioxide than did bare ST-01, indicating that RhCl3/ST-01 effectively utilized both visible light and UV light and that two types of reaction (photosensitization by fixed RhCl3 and photocatalysis by TiO2) occurred over RhCl3/ST-01. 相似文献
839.
Suresh CH Vargheese AM Vijayalakshmi KP Mohan N Koga N 《Journal of computational chemistry》2008,29(11):1840-1849
Structural water molecule 301 found at the interface of HIV protease-inhibitor complexes function as a hydrogen bond (H-bond) donor to carbonyl groups of the inhibitor as well as H-bond acceptor to amide/amine groups of the flap region of the protease. In this study, six systems of HIV protease-inhibitor complexes were analyzed, which have the presence of this "conserved" structural water molecule using a two-layer QM/MM ONIOM method. The combination of QM/MM and QM method enabled the calculation of strain energies of the bound ligands as well as the determination of their binding energies in the ligand-water and ligand-water-protease complexes. Although the ligand experiences considerable strain in the protein bound structure, the H-bond interactions through the structural water overcomes this strain effect to give a net stability in the range of 16-24 kcal/mol. For instance, in 1HIV system, the strain energy of the ligand was 12.2 kcal/mol, whereas the binding energy associated with the structural water molecule was 20.8 kcal/mol. In most of the cases, the calculated binding energy of structural water molecule showed the same trend as that of the experimental binding free energy values. Further, the classical MD simulations carried out on 1HVL system with and without structural water 301 showed that this conserved water molecule enhances the H-bond dynamics occurring at the Asp-bound active site region of the protease-inhibitor system, and therefore it will have a direct influence on the mechanism of drug action. 相似文献
840.
K. Takamiya R. Okumura N. Abe Y. Nakano K. Miyata S. Fukutani A. Taniguchi H. Yamana 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(3):719-721
The new control system of pneumatic transportation apparatuses for neutron irradiation in Kyoto University Reactor (KUR) has
been developed based on the TCP/IP network for the purpose of integrated management of the apparatus. The control system is
comprised of PLCs, control PCs, database and web servers. Archiving logs of detailed information about irradiation enables
the secure operation and management of the irradiation system. The information stored in the server can be referred by remote
PCs and mobile phones through the internet. Combining the present facility with measurement and radiation management systems
it can realize advanced INAA methods and secure managements of radioisotopes. 相似文献