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721.
Takanori Shibata Mayu Miyoshi Toshifumi Uchiyama Kohei Endo Nobuaki Miura Kenji Monde 《Tetrahedron》2012,68(12):2679-2686
An enantioselective intramolecular [2+2+2] cycloaddition of 2-aminophenol-tethered triynes and diyne-nitriles proceeded using the chiral Rh catalysts, and tripodal cyclophanes and pyridinophanes with a long ansa chain (up to [16]pyridinophane) were obtained in acceptable yield with high to almost perfect ee. In the reaction of triynes, we elucidated that the oxygen atom at the alkyne terminus is essential for the excellent enantioselectivity. For the construction of cage-type molecule, the choice of rigid tether, which connects 1,6-diyne moiety with a side carbon chain having alkyne or cyano group on its terminus, was important, and 8-amino-2-naphthol moiety was also a preferable tether. 相似文献
722.
Yagi I Mikami K Ebina K Okamura M Uosaki K 《The journal of physical chemistry. B》2006,110(29):14192-14197
Ultrafast photoexcited carrier dynamics in CdS nanoparticles prepared by an AOT/n-heptane reversed micelle system were investigated by a femtosecond visible-pump/mid-IR probe technique. A mid-IR probe beam was found to mainly probe the ultrafast dynamics of photoexcited electrons in the conduction band. Dispersions of CdS nanoparticles with 8 different mean diameters from 2.9 to 4.1 nm were prepared by tuning the mole ratio between water and AOT (W = [H(2)O]/[AOT]) in the reversed micelle systems. The excited state lifetime strongly depended on the mean size of CdS nanoparticles with a maximum around a mean diameter of 3.5 nm. This result was explained by considering the balance between the carrier recombination rates via surface states and those via interior states. The relationship between the excited state lifetime and the size of CdS nanoparticles was drastically changed when the surface was terminated by thiol molecules. 相似文献
723.
Carboxylic acid-terminated monolayers on crystalline silicon surfaces can be readily modified with biological macromolecules for the fabrication of semiconductor-based biosensing devices. They were prepared by acid-catalyzed hydrolysis of alkoxycarbonyl (ester)-terminated monolayers and studied by vibrational sum frequency generation (SFG) spectroscopy. The C-H vibration region of the SFG spectra consists of strong methyl bands with significant contributions from methylene stretching modes, indicating that these monolayers are generally ordered but with considerable gauche defects in the alkyl chains in comparison with n-alkyl monolayers. After hydrolysis, the methylene stretching modes prevail, with "residues" of the methyl bands, indicating incomplete hydrolysis and disruption of the monolayer structure. This work demonstrates that SFG is capable of providing quantitative information on structure-reactivity correlations in organic monolayers. 相似文献
724.
725.
By the treatment of 0.3 molar amount of NbCl5 and LiAlH4, o-arylated alpha,alpha,alpha-trifluorotoluenes afforded fluorene derivatives in good yields. C-F bonds of the CF3 group and the neighboring ortho C-H bond were doubly activated to give the coupling products. 相似文献
726.
727.
Ezoe Y Moriyama T Ogawa T Kakiuchi T Mitsuishi I Mitsuda K Aoki T Morishita K Nakajima K 《Optics letters》2012,37(5):779-781
Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost. 相似文献
728.
Dr. Daichi Kato Dr. Peng Song Dr. Hiroki Ubukata Haruki Taguro Dr. Cédric Tassel Dr. Kohei Miyazaki Prof. Takeshi Abe Dr. Kousuke Nakano Prof. Kenta Hongo Prof. Ryo Maezono Prof. Hiroshi Kageyama 《Angewandte Chemie (International ed. in English)》2023,62(30):e202301416
Mixed-anion compounds have attracted growing attentions, but their synthesis is challenging, making a rational search desirable. Here, we explored LaF3-LaX3 (X=Cl, Br, I) system using ab initio structure searches based on evolutionary algorithms, and predicted LaF2X and LaFX2 (X=Br, I), which are respectively isostructural with LaHBr2 and YH2I, consisting of layered La-F blocks with single and double ordered honeycomb lattices, separated by van der Waals gaps. We successfully synthesized these compounds: LaF2Br and LaFI2 crystallize in the predicted structure, while LaF2I is similar to the predicted one but with different layer stacking. LaF2I exhibits fluoride ion conductivity comparable to that of non-doped LaF3, and has the potential to show better ionic conductivity upon appropriate doping, given the theoretically lower diffusion energy barrier and the presence of soft iodine anions. This study shows the structure prediction using evolutionary algorithms will accelerate the discovery of mixed-anion compounds in future, in particular those with an ordered anion arrangement. 相似文献
729.
Kohei Goto Toshiyuki Akiike Yasutake Inoue Minoru Matsubara 《Macromolecular Symposia》2003,199(1):321-332
We successfully prepared a series of thermally stable polyimides (PIs) with low dielectric constant (k) by introducing bulky diphenyl fluorenylidene moieties in backbone. The lowest k was found to be 2.77 among non-fluorinated PIs and 2.35 among fluorinated ones. In order to prove the lowest limit of k in PIs, we prepared soluble and thermally stable polyarylenes (PArs) without polar imide linkage with the same aromatic moieties by coupling polymerization. The lowest k was 2.7 without fluorine (F) and 2.2 with F atom, which showed also promising for low k materials. From these results, PIs we prepared were estimated to the lowest k values among PIs. On the basis of statistics on these results, we could express contour lines of k as a function of imide concentration and F content with high correlation factor (r= 0.96) in PIs and PArs. 相似文献
730.
Dr. Masafumi Minoshima Taro Umeno Kohei Kadooka Margaux Roux Namiko Yamada Prof. Dr. Kazuya Kikuchi 《Angewandte Chemie (International ed. in English)》2023,62(18):e202301704
To understand the function of protein in live cells, real-time monitoring of protein dynamics and sensing of their surrounding environment are important methods. Fluorescent labeling tools are thus needed that possess fast labeling kinetics, high efficiency, and long-term stability. We developed a versatile chemical protein-labeling tool based on fluorophore-conjugated diazabicyclooctane β-lactamase inhibitors (BLIs) and wild-type TEM-1 β-lactamase protein tag. The fluorescent probes efficiently formed a stable carbamoylated complex with β-lactamase, and the labeled proteins were visualized over a long period of time in live cells. Moreover, use of an α-fluorinated carboxylate ester-based BLI prodrug enabled the probe to permeate cell membranes and stably label intracellular proteins after unexpected spontaneous ester hydrolysis. Lastly, combining the labeling tool with a pH-activatable fluorescent probe allowed visual monitoring of lysosomal protein translocation during autophagy. 相似文献