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101.
Benten H Ohkita H Ito S Yamamoto M Sakumoto N Hori K Tohda Y Tani K Nakamura Y Nishimura J 《The journal of physical chemistry. B》2005,109(42):19681-19687
The photophysical properties of a series of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n = 3, 4, 5, 6) were studied as a model compound for a fully overlapped carbazole excimer. In these [3.3.n]Cz molecules, a plane angle of the two carbazole moieties changed systematically from nearly parallel to oblique, with increases in the length of the methylene chain n bridging at the 9-position of each carbazole ring. Absorption bands of [3.3.n]Cz showed the blue-shift and the splitting for (1)L(a) <-- (1)A and (1)L(b) <-- (1)A transition bands of the reference carbazole monomer, respectively. These spectral changes in [3.3.n]Cz were explained by Kasha's molecular exciton theory with the distance r and dihedral angle theta between the carbazole moieties in the ground state. In both liquid and glass matrixes, [3.3.n]Cz showed intramolecular excimer emission. The emission peak wavelength changed from 409 nm (n = 6) to 480 nm (n = 3) depending on r in the ground state. The dependence of the peak wavelength on r clearly showed that relative configurations of carbazole moieties in the ground state were preserved even in the excimer states. The smaller radiative rate of the excimer emission than the reference monomer was explained by the dimer symmetry of [3.3.n]Cz. 相似文献
102.
103.
A highly sensitive and accurate determination method for trace quantities of enantiomers of glufosinate (D,L-GLUF), a phosphorus-containing amino acid-type herbicide, has been studied. The present method is based on the change in the mole ratio of the enantiomeric isomers after spiking of a known amount of an isomer (L-GLUF). The chiral separation and detection were made by gamma-cyclodextrin modified capillary zone electrophoresis (gamma-CD-CZE) with fluorescence detection. Solid-phase extraction of D,L-GLUF with titania was investigated as the pre-separation method to eliminate coexisting materials such as inorganic salts and organic compounds in river water. A separated D,L-GLUF was labeled with dansyl chloride and subjected to the on-capillary concentration using large-volume sample stacking (LVSS) before gamma-CD-CZE. The detection limit of the present method was as low as 2.0 x 10(-9) M. The present method was successfully applied to a model sample containing 2.0 x 10(-7) M D,L-GLUF in river water. It was confirmed that trace quantities of D-and L-GLUF in environmental samples can be accurately determined without any calibration curves and comparison standards. 相似文献
104.
Trevor K. Ellis Hisanori Ueki Rohit Tiwari Vadim A. Soloshonok 《Tetrahedron: Asymmetry》2009,20(22):2629-2634
(S)-5-Oxo-N-phenyl-1-[(E)-3-phenylacryloyl]pyrrolidine-2-carboxamide, easily prepared from inexpensive and readily available, in both enantiomeric forms, glutamic/pyroglutamic acid was designed as an optimal type of chiral Michael acceptor for reactions with a series of nucleophilic glycine equivalents. A study of the corresponding Michael addition reactions revealed that the new generation of modular glycine derivatives, as a counterpart to the Michael acceptor, provides for operationally convenient preparation of β-phenyl pyroglutamic acids and related compounds with virtually complete chemical and stereochemical outcomes. 相似文献
105.
Kitagawa Y Sentoku Y Akamatsu S Sakamoto W Kodama R Tanaka KA Azumi K Norimatsu T Matsuoka T Fujita H Yoshida H 《Physical review letters》2004,92(20):205002
An ultraintense laser injected a 10 J of power at 1.053 microm in 0.5 ps into a glass capillary of 1 cm long and 60 microm in diameter and accelerated plasma electrons to 100 MeV. One- and two-dimensional particle codes describe wakefields with 10 GV/m gradient excited behind the laser pulse, which are guided by a plasma density channel far beyond the Rayleigh range. The blueshift of the laser spectrum supports that a plasma of 10(16) cm(-3) is inside the capillary. A bump at the high energy tail suggests the electron trapping in the wakefield. 相似文献
106.
Hashimoto A Suenaga K Urita K Shimada T Sugai T Bandow S Shinohara H Iijima S 《Physical review letters》2005,94(4):045504
Atomic correlation between adjacent graphene layers was elucidated for double-wall carbon nanotubes (DWNTs) through a chiral index assignment of two nested nanotubes by high-resolution transmission electron microscopy. Our analysis provides a rather constant diameter difference close to 0.75 nm but no chiral angle correlation between the constituent nanotubes in the concentric DWNTs. The local atomic correlation as a commensurate graphene stacking was repeatedly found in eccentric DWNTs and circumscribed nanotubes, which should lead to elastic deformation and bundling of nanotubes. 相似文献
107.
Yasuo Iwanami Takeshi Inagaki Hisanori Sakata 《Journal of mass spectrometry : JMS》1977,12(5):302-306
7-Phenacylxanthopterin and its para-substituted derivatives, which exist in the chelate rign form initially lose CO from pyrazine rings followed by a hydrogen atom. This ion can also be formed in the reverse order, but not for the 4-amino analogues. Fragmentation of the intramolecularly hydrogen bonded sidechain also occurs involving loss of a benzoyl or phenyl radical. Linear plots at 40 eV for the loss of the benzoyl radical were obtained for log (Z/Z0) against the Hammet σ constants not only for the fragmentation of the xanthopterins but also for that of the amino analogues. 相似文献
108.
109.
Prof. Hidetoshi Kawai Tatsuya Utamura Erina Motoi Tomoko Takahashi Hiroyoshi Sugino Manabu Tamura Prof. Masakazu Ohkita Prof. Kenshu Fujiwara Takao Saito Prof. Takashi Tsuji Prof. Takanori Suzuki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(14):4513-4524
The macrocyclization of 2,6‐diethynyl hydrindacenes ( 1 ) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle ( 2 ) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle ( 3 ) demonstrates a moderate degree of geometrical flexibility as a result of the five‐membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π‐conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups. 相似文献
110.
4,4′-bis(N-carbazolyl)tolan (BCT) and 4,4′-bis[N-(3,6-di-t-butyl)carbazolyl]tolan (BCT-t-Bu) were synthesized as π-expanded analogs of 4,4′-bis(N-carbazolyl)biphenyl. Their photophysical characteristics both in solution and films were thoroughly investigated. Interestingly, the phosphorescence spectrum of BCT was significantly medium-dependent, and the emission maximum was red-shifted by 131 nm from 489 nm in solution at 77 K to 620 nm in a deposited film at 5 K, suggesting the presence of strong intermolecular interactions in the film. BCT and BCT-t-Bu were found to be useful as host materials for fluorescence-based organic light emitting diodes (OLEDs). However, their low triplet energy levels in films negated their potential to act as hosts in phosphorescence-based OLEDs. 相似文献