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351.
352.
Binding of Scandium Ions to Metalloporphyrin–Flavin Complexes for Long‐Lived Charge Separation 下载免费PDF全文
Prof. Dr. Takahiko Kojima Ryosuke Kobayashi Dr. Tomoya Ishizuka Shinya Yamakawa Dr. Hiroaki Kotani Dr. Tatsuaki Nakanishi Dr. Kei Ohkubo Dr. Yoshihito Shiota Prof. Dr. Kazunari Yoshizawa Prof. Dr. Shunichi Fukuzumi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15518-15532
A porphyrin–flavin‐linked dyad and its zinc and palladium complexes (MPor?Fl: 2 ?M, M=2 H, Zn, and Pd) were newly synthesized and the X‐ray crystal structure of 2 ?Pd was determined. The photodynamics of 2 ?M were examined by femto‐ and nanosecond laser flash photolysis measurements. Photoinduced electron transfer (ET) in 2 ?H2 occurred from the singlet excited state of the porphyrin moiety (H2Por) to the flavin (Fl) moiety to produce the singlet charge‐separated (CS) state 1(H2Por.+?Fl.?), which decayed through back ET (BET) to form 3[H2Por]*?Fl with rate constants of 1.2×1010 and 1.2×109 s?1, respectively. Similarly, photoinduced ET in 2 ?Pd afforded the singlet CS state, which decayed through BET to form 3[PdPor]*?Fl with rate constants of 2.1×1011 and 6.0×1010 s?1, respectively. The rate constant of photoinduced ET and BET of 2 ?M were related to the ET and BET driving forces by using the Marcus theory of ET. One and two Sc3+ ions bind to the flavin moiety to form the Fl?Sc3+ and Fl?(Sc3+)2 complexes with binding constants of K1=2.2×105 M ?1 and K2=1.8×103 M ?1, respectively. Other metal ions, such as Y3+, Zn2+, and Mg2+, form only 1:1 complexes with flavin. In contrast to 2 ?M and the 1:1 complexes with metal ions, which afforded the short‐lived singlet CS state, photoinduced ET in 2 ?Pd???Sc3+ complexes afforded the triplet CS state (3[PdPor.+?Fl.??(Sc3+)2]), which exhibited a remarkably long lifetime of τ=110 ms (kBET=9.1 s?1). 相似文献
353.
Coordination‐Driven Macrocyclization for Locking of Photo‐ and Thermal cis→trans Isomerization of Azobenzene 下载免费PDF全文
Dr. Masaki Yamamura Koji Yamakawa Yuki Okazaki Prof. Dr. Tatsuya Nabeshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16258-16265
Both trans and cis isomers of azobenzene‐linked bis‐terpyridine ligand L1 were incorporated in rigid macrocycles linked by FeII(tpy)2 (tpy: terpyridine) units. The complex of the longer trans‐ L1 is dinuclear [(trans‐ L1 )2 ? FeII2], whereas the complex of the shorter cis‐ L1 is mononuclear [cis‐ L1? FeII]. The complex cis‐ L1? FeII was not only thermally stable but also photochemically inactive. These results indicate a perfectly locked state of cis‐azobenzene. The stable macrocyclic structure of cis‐ L1? FeII causes locking of the isomerization. To the best of our knowledge, this is first example of dual locking of photo‐ and thermal isomerization of cis‐azobenzene. 相似文献
354.
The Source of “Fairy Rings”: 2‐Azahypoxanthine and its Metabolite Found in a Novel Purine Metabolic Pathway in Plants 下载免费PDF全文
Dr. Jae‐Hoon Choi Dr. Toshiyuki Ohnishi Yasuhiro Yamakawa Shogo Takeda Shuhei Sekiguchi Waki Maruyama Kimiko Yamashita Dr. Tomohiro Suzuki Prof. Dr. Akio Morita Dr. Takashi Ikka Prof. Dr. Reiko Motohashi Dr. Yoshikazu Kiriiwa Dr. Hiroyuki Tobina Tatsuo Asai Dr. Shinji Tokuyama Dr. Hirofumi Hirai Dr. Nobuhiro Yasuda Dr. Keiichi Noguchi Dr. Tomohiro Asakawa Dr. Shimpei Sugiyama Prof. Dr. Toshiyuki Kan Prof. Dr. Hirokazu Kawagishi 《Angewandte Chemie (International ed. in English)》2014,53(6):1552-1555
Rings or arcs of fungus‐stimulated plant growth occur worldwide; these are commonly referred to as “fairy rings”. In 2010, we discovered 2‐azahypoxanthine (AHX), a compound responsible for the fairy‐ring phenomenon caused by fungus; AHX stimulated the growth of all the plants tested. Herein, we reveal the isolation and structure determination of a common metabolite of AHX in plants, 2‐aza‐8‐oxohypoxanthine (AOH). AHX is chemically synthesized from 5‐aminoimidazole‐4‐carboxamide (AICA), and AHX can be converted into AOH by xanthine oxidase. AICA is one of the members of the purine metabolic pathway in animals, plants, and microorganisms. However, further metabolism of AICA remains elusive. Based on these results and facts, we hypothesized that plants themselves produce AHX and AOH through a pathway similar to the chemical synthesis. Herein, we demonstrate the existence of endogenous AHX and AOH and a novel purine pathway to produce them in plants. 相似文献
355.
Yuhki OhtsukaTetsu Yamakawa 《Tetrahedron》2011,67(12):2323-2331
Direct ethoxycarbonyldifluoromethylation of aromatic compounds by BrCF2CO2Et was investigated using Fenton reagent in dimethylsulfoxide. Various five-membered hetero-aromatic compounds, benzene derivatives and uracil having ethoxycarbonyldifluoromethyl group were obtained catalytically with the combination of ferrocene and H2O2 at room temperature. The ethoxycarbonyldifluoromethylation occurred at the position predicted by the trend of the electrophilic substitution of aromatic compounds. When para-substituted aniline derivatives were used as a substrate, the one-pot synthesis of 3,3-difluoro-2,3-dihydroindole-2-one derivatives was achieved through the ethoxycarbonyldifluoromethylation at the ortho-position to the amino group and the consecutive intramolecular amidation of the amino group and the adjacent ethoxycarbonyldifluoromethyl group. 相似文献
356.
Dr. Tomoyuki Ikai Dr. Kosuke Oki Shoya Yamakawa Prof. Eiji Yashima 《Angewandte Chemie (International ed. in English)》2023,62(18):e202301836
Enantiopure [6]helicene containing an embedded seven-membered ring and carbo[7]helicene (>99 % ee) with opposite helicity were simultaneously and quantitatively (>99 %) synthesized with a perfect stereospecificity through stepwise acid-promoted intramolecular alkyne annulations of doubly axial-chiral cyclization precursors. The helical handedness of the [6]- and [7]helicenes was fully stereocontrolled by the doubly axial chirality of the precursors as a result of complete axial-to-helical chirality transfer. The cyclizations proceeded in a stepwise manner; the first six-membered ring formation was followed by the kinetically controlled seven- or six-membered ring formation with or without helix-inversion of a [4]helicene intermediate generated during the first cyclization step, thus quantitatively producing enantiopure circularly polarized luminescent [6]- and [7]helicenes with opposite helicity. 相似文献
357.
Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics 总被引:2,自引:0,他引:2
We propose here a new method for continuous concentration and classification of particles in microfluidic devices, named hydrodynamic filtration. When a particle is flowing in a microchannel, the center position of the particle cannot be present in a certain distance from sidewalls, which is equal to the particle radius. The proposed method utilizes this fact, and is performed using a microchannel having multiple side branch channels. By withdrawing a small amount of liquid repeatedly from the main stream through the side channels, particles are concentrated and aligned onto the sidewalls. Then the concentrated and aligned particles can be collected according to size through other side channels (selection channels) in the downstream of the microchannel. Therefore, continuous introduction of a particle suspension into the microchannel enables both particle concentration and classification at the same time. In this method, the flow profile inside a precisely fabricated microchannel determines the size limit of the filtered substances. So the filtration can be performed even when the channel widths are much larger than the particle size, without the problem of channel clogging. In this study, concentrations of polymer microspheres with diameters of 1-3 microm were increased 20-50-fold, and they were collected independently according to size. In addition, selective enrichment of leukocytes from blood was successfully performed. 相似文献
358.
Otsuki J Nagamine E Kondo T Iwasaki K Asakawa M Miyake K 《Journal of the American Chemical Society》2005,127(29):10400-10405
Monolayer arrays of a series of meso-tetra-substituted porphyrins containing octadecyloxy and carboxyl (or pyridyl) groups were prepared on the highly oriented pyrolytic graphite surface at the liquid/solid interface. It was found by means of scanning tunneling microscopy that some porphyrins from this family assemble into various patterns. Specifically, slightly undulated rows are obtained from 5,10,15-tris(4-octadecyloxyphenyl)-20-(4-pyridyl)porphyrin. Meanwhile, rows with more pronounced kinks result from 5-(4-carboxyphenyl)-10,15,20-tris(4-octadecyloxyphenyl)porphyrin. The occurrence of the kinks is dependent on the arrangement of surrounding porphyrin molecules and is determined by intricate interplay between directional hydrogen-bonding interactions and packing forces, including molecule-molecule and molecule-substrate interactions. A double-layer structure is obtained from 5,10-bis(4-carboxyphenyl)-15,20-bis(4-octadecyloxyphenyl)porphyrin, probably through cyclic hydrogen bond formation. This work proves the concept that programmed surface patterning is possible by using porphyrins incorporating directional intermolecular interaction sites. 相似文献
359.
We describe the moduli spaces of meromorphic connections on trivial holomorphic vector bundles over the Riemann sphere with at most one (unramified) irregular singularity and arbitrary number of simple poles as Nakajima's quiver varieties. This result enables us to solve partially the additive irregular Deligne–Simpson problem. 相似文献