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121.
Organization of supramolecular assemblies of chromophores with precisely-controlled orientation and sequence remains challenging. Nucleic acids with complementary base sequences spontaneously form double-helical structures. Therefore, covalent attachment of chromophores to DNA or RNA can be used to control assembly and orientation of chromophores. In this perspective, we first review our recent work on the assemblies of fluorophores (pyrene and perylene) by using natural base pairs. The interaction between dyes can be strictly controlled by means of cluster and interstrand wedge motifs. We then discuss novel artificial base pairs that can suppress the interaction between fluorophores and nucleobases. We incorporated a cyclohexane moiety into DNA, and showed that these artificial base pairs suppressed the electron-hole transfer between fluorophores and nucleobases and enhanced the quantum yields of fluorophores. These base pairs can potentially be used to accumulate fluorophores inside DNA duplexes without decreasing quantum yields. 相似文献
122.
Asanuma H Hayashi H Zhao J Liang X Yamazawa A Kuramochi T Matsunaga D Aiba Y Kashida H Komiyama M 《Chemical communications (Cambridge, England)》2006,(48):5062-5064
By introducing an intercalator through D-threoninol to the 10-23 DNAzyme at the junction between its catalytic loop and the binding arm, the RNA cleavage activity was greatly improved. 相似文献
123.
Caffeic acid (CA) and its analogues such as rosmarinic acid are well known as antioxidative agents. Exposure to UVA is known to generate reactive oxygen species (ROS) such as singlet oxygen (1O2) and superoxide anion radical (*O2-) in the skin of animals, which in turn induces skin photodamage and photoaging. Because CA and its analogues quench 1O2, these compounds were topically applied to the abdominal skin of live hairless mice and were found to suppress ROS generation upon UVA exposure. Furthermore, the generation of UVA-induced ROS was also suppressed in the skin of mice that were orally given CA. In order to understand the mechanism by which CA blocks ROS production in UVA-exposed skin, the pharmacokinetics of CA upon oral administration to mice was followed and CA was found to efficiently distribute in the skin. These results suggest that skin damage by UVA-induced ROS generation is reduced by oral supplementation of CA, which has a scavenging and quenching activity against ROS. 相似文献
124.
Hiromu Ishihara 《Fresenius' Journal of Analytical Chemistry》1915,54(1):66-68
Ohne Zusammenfassung 相似文献
125.
126.
Hiromi Takiguchi Azusa Tsubata Makoto Miyata Tamao Odake Hiroki Hotta Tomonari Umemura Kin-ichi Tsunoda 《Analytical sciences》2006,22(7):1017-1019
A flow injection analysis system was built with a liquid core waveguide spectrophotometric detector using an 80 cm Teflon AF-1600 capillary tube (2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole/tetrafluoroethylene). The system was applied to determine nitrite ion in river water samples. The lower limit of detection for nitrite was 2.1 nmol dm(-3) (0.1 ng dm(-3) as NO(2)(-)) and the relative standard deviation of measurements was typically 0.56% (n = 5) at 0.21 micromol dm(-3). 相似文献
127.
A method has been devised to calculate the half-width of the phase contrast enhanced edge of an X-ray- image with incoherent X-rays. This method is based on changes in the wave fronts of X-rays after penetrating an object, and it takes into account the blur due to penumbra observed in practical radiographic imaging. The method closely predicted edge enhancement when images of a plastic fiber were produced with practical X-ray tubes (Cu, Mo, and W anodes with focus-diameters of 10,100, and 40 μ, respectively). Thus, the method shows promise in facilitating phase contrast X-ray imaging in both medical radiography and non-destructive inspection using incoherent X-rays from X-ray tubes with substantial focus-sizes. 相似文献
128.
Hiromu Kawakubo Tomoko Suzuki Kazutaka Nishino Futaba Hara Tomoyoshi Takano Yoshito Takebayashi 《合成通讯》2013,43(9):1068-1072
Diethyl azodicarboxylate (DEAD) is a well-known coupling reagent that can be readily synthesized from diethylhydrazodicarboxylate (DEHD). The bromination of commercially available ethyl allophanate (1) in CHCl3, followed by the Hofmann-type rearrangement reaction of the resulting N-brominated species 2 and 3 in C2H5OH in the presence of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), gave DEHD in good yield from a one-pot process. Interestingly, however, the bromination and Hofmann-type rearrangement reactions did not occur in the presence of N(C2H5)3. These results therefore suggest that this reaction is reliant upon a high level of reactivity during the bromination reaction to give 2 and 3, and that these N-brominated species require the presence of a strong and nonnucleophilic base to undergo the Hofmann-type rearrangement to give DEHD. 相似文献
129.
The polymerization of vinyl monomers initiated with the system of polyvinylferrocene (PVFc) and carbon tetrachloride (CCl4) was carried out in dark. Methyl methacrylate (MMA) and acrylonitrile (AN) could be polymerized, while styrene (St) was hardly polymerized under the conditions used. The polymerization proceeded through a free-radical mechanism and was concluded to be initiated by attack of vinyl monomer, having a polarized vinyl group, on the charge-transfer complex of PVFc/CCl4. In the polymerization of MMA, the initiating ability of PVFc was much larger than that of ferrocene (Fc-H) or poly(ferrocenylmethyl methacrylate) (PFMMA) and was comparable to that of polyferrocenylenemethylene (PFM). The overall activation energy was estimated to be 34.2 kJ/mole. 相似文献
130.
Prof. Ryo Ohtani Hiromu Matsunari Prof. Takafumi Yamamoto Prof. Koji Kimoto Prof. Masaaki Isobe Dr. Kotaro Fujii Prof. Masatomo Yashima Dr. Susumu Fujii Dr. Akihide Kuwabara Dr. Yuh Hijikata Prof. Shin-ichiro Noro Prof. Masaaki Ohba Prof. Hiroshi Kageyama Prof. Shinya Hayami 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19416-19421
Metal node design is crucial for obtaining structurally diverse coordination polymers (CPs) and metal–organic frameworks with desirable properties; however, FeII ions are exclusively six-coordinated. Herein, we present a cyanide-bridged three-dimensional (3D) CP, FePd(CN)4, bearing four-coordinate FeII ions, which is synthesized by thermal treatment of a two-dimensional (2D) six-coordinate FeII CP, Fe(H2O)2Pd(CN)4⋅4 H2O, to remove water molecules. Atomic-resolution transmission electron microscopy and powder X-ray and neutron diffraction measurements revealed that the FePd(CN)4 structure is composed of a two-fold interpenetrated PtS topology network, where the FeII center demonstrates an intermediate geometry between tetrahedral and square-planar coordination. This four-coordinate FeII center with the distorted geometry can act as a thermo-responsive flexible node in the PtS network. 相似文献