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排序方式: 共有169条查询结果,搜索用时 828 毫秒
31.
Dr. Tatsuhiko Yoshino Shun Satake Prof. Dr. Shigeki Matsunaga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(33):7346-7357
Transition-metal-catalyzed C−H functionalization reactions with Cp*MIII catalysts (M=Co, Rh, Ir) have found a wide variety of applications in organic synthesis. Albeit the intrinsic difficulties in achieving catalytic stereocontrol using these catalysts due to their lack of additional coordination sites for external chiral ligands and the conformational flexibility of the Cp ligand, catalytic enantioselective C−H functionalization reactions using the Group 9 metal triad with Cp-type ligands have been intensively studied since 2012. In this minireview, the progress in these reactions according to the type of the chiral catalyst used are summarized and discussed. The development of chiral Cpx ligands the metal complexes thereof, artificial metalloenzymes, chiral carboxylate-assisted enantioselective C−H activations, enantioselective alkylations assisted by chiral carboxylic acids or chiral sulfonates, and chiral transient directing groups are discussed. 相似文献
32.
Tatsuhiko Saito 《Semigroup Forum》1988,37(1):37-43
Communicated by J. M. Howie 相似文献
33.
(±)-Isoagatholactone and (±)-12α-hydroxyspongia-13(16),14-dien , a fundamental skeleton of spongiadiol and its congeners, have been synthesized from (±)-labda-8(20),13-dien-15-oic acid . 相似文献
34.
7-Azaindole did not react with benzophenone on irradiation. However, irradiation of benzophenone in the presence of 1-acetyl-7-azaindole produced an oxetane by cycloaddition of the ketone to the 7-azaindole 2,3-double bond. The nmr and the mass spectra of the oxetane have also been studied in some detail. 相似文献
35.
36.
Palladium/monophosphine complexes catalyze trans-selective arylative, alkenylative, and alkylative cyclization reactions of alkynals and alkynones with organoboronic reagents. These reactions afford six-membered allylic alcohols with endo-tri- or tetrasubstituted olefin groups and/or five-membered counterparts with exo olefin groups. The ratios of these products are dramatically affected by alkyne substituents as well as the phosphine ligand. The remarkable trans-selectivity of the process results from the novel reaction mechanism involving oxidative addition without oxametallacycle formation. 相似文献
37.
Shiori Ogawa Swarup Chattopadhyay Yuya Tanaka Tatsuhiko Ohto Tomofumi Tada Hirokazu Tada Shintaro Fujii Tomoaki Nishino Munetaka Akita 《Chemical science》2021,12(32):10871
Control of charge carriers that transport through the molecular junctions is essential for thermoelectric materials. In general, the charge carrier depends on the dominant conduction orbitals and is dominantly determined by the terminal anchor groups. The present study discloses the synthesis, physical properties in solution, and single-molecule conductance of paddle-wheel diruthenium complexes 1R having diarylformamidinato supporting ligands (DArF: p-R-C6H4-NCHN-C6H4-R-p) and two axial thioanisylethynyl conducting anchor groups, revealing unique substituent effects with respect to the conduction orbitals. The complexes 1R with a few different aryl substituents (R = OMe, H, Cl, and CF3) were fully characterized by spectroscopic and crystallographic analyses. The single-molecule conductance determined by the scanning tunneling microscope break junction (STM-BJ) technique was in the 10−5 to 10−4G0 region, and the order of conductance was 1OMe > 1CF3 ≫ 1H ∼ 1Cl, which was not consistent with the Hammett substituent constants σ of R. Cyclic voltammetry revealed the narrow HOMO–LUMO gaps of 1R originating from the diruthenium motif, as further supported by the DFT study. The DFT-NEGF analysis of this unique result revealed that the dominant conductance routes changed from HOMO conductance (for 1OMe) to LUMO conductance (for 1CF3). The drastic change in the conductance properties originates from the intrinsic narrow HOMO–LUMO gaps.Dominant conduction orbitals of paddle-wheel organodiruthenium complexes can be facilely controlled by the substituents embedded in the amidinato ligands. 相似文献
38.
Hu W Jiang J Nakashima H Luo Y Kashimura Y Chen KQ Shuai Z Furukawa K Lu W Liu Y Zhu D Torimitsu K 《Physical review letters》2006,96(2):027801
A molecular junction of a poly(p-phenyleneethynylene)s derivative with thioacetate end groups (TA-PPE) was fabricated by self-assembling. Nanogap electrodes made by electroplating technique was used to couple thiol end groups of TA-PPE molecules. Room temperature current-voltage characteristics of the molecular junction exhibited highly periodic, repeatable, and identical stepwise features. First-principles calculations suggest that one possibility for the equidistant step is due to the opening of different conducting channels that corresponds to the unoccupied molecular orbitals of the polymer in the junction. It is interesting to see that an 18 nm long polymer is of quantized electronic structures and behaves like a quantum transport device. 相似文献
39.
We propose a microchannel device that employs a surface-supported self-spreading lipid bilayer membrane as a molecule carrying medium. The device has a micropattern structure fabricated on a SiO2 surface by photolithography, into which a self-spreading lipid bilayer membrane is introduced as the carrier medium. This system corresponds to a microchannel with a single lipid bilayer membrane height of approximately 5 nm, compared with conventional micro-fluidic channels that have a section height and width of at least several microm. The device is beneficial for detecting intermolecular interactions when molecules carried by the self-spreading lipid bilayer collide with each other in the microchannel. The validity of the device was confirmed by observing the fluorescence resonance energy transfer (FRET) between two dye molecules, coumarin and fluorescein. 相似文献
40.
Toshiaki Asakai Mariko Murayama Tatsuhiko Tanaka 《Accreditation and quality assurance》2007,12(3-4):151-155
The accuracy and uncertainty of the coulometric measurement results of reference materials for acidimetric titration were
examined in this study. The results for amidosulfuric acid and potassium hydrogen phthalate are presented. The uncertainty
was investigated by examining the dependency on the sample size and on the electrolysis current. Changes in the titration
parameters did not result in any significant effects on the titration results. Acidimetric standards with the certified value
linked to the SI were developed. In addition, the intercomparison of acidimetric standards was carried out by gravimetric
titration, and the relationship between our coulometric results was determined. Furthermore, due to recent internationalization,
not only the traceability to the SI but also the relationship and consistency of their analytical data have gained increasing
importance. Our results were validated using certified reference materials (CRMs) obtained from different National Metrology
Institutes (NMIs), and their relationships are presented.
Presented at -- “BERM-10” -- April 2006, Charleston, SC, USA. 相似文献