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排序方式: 共有235条查询结果,搜索用时 15 毫秒
101.
Haruka Ohsato Kazuma Kawauchi Prof. Shigeyuki Yamada Prof. Tsutomu Konno 《Chemical record (New York, N.Y.)》2023,23(9):e202300080
Organic molecules with fluoroalkylene scaffolds, especially a tetrafluoroethylene (CF2CF2) moiety, in their molecular structures exhibit unique biological activities, or can be applied to functional materials such as liquid crystals and light-emitting materials. Although several methods for the syntheses of CF2CF2-containing organic molecules have been reported to date, they have been limited to methods using explosives and fluorinating agents. Therefore, there is an urgent need to develop simple and efficient approaches to synthesize CF2CF2-containing organic molecules from readily available fluorinated substrates using carbon-carbon bond formation reactions. This personal account summarizes the simple and efficient transformation of functional groups at both ends of 4-bromo-3,3,4,4-tetrafluorobut-1-ene and discusses its synthetic applications to biologically active fluorinated sugars and functional materials, such as liquid crystals and light-emitting molecules. 相似文献
102.
The zinc bilinone (ZnBL) dimers 4 and 5 bearing chiral aliphatic spacers ((2S,4S)-2,4-pentanedioxy and (3S,5S)-2,6-dimethyl-3,5-heptanedioxy for 4 and 5, respectively) were newly prepared, and their conformational distribution was investigated. The 1H NMR and circular dichroism spectra revealed that the present dimers predominantly adopted the homohelicity conformation (MM and PP for 4 and 5, respectively), although the reference monomers with the corresponding subunit structures exhibited poor helicity enrichment. The helical twisting powers of these ZnBL dimers for a nematic liquid crystal (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) were also investigated. With the dimers doped into MBBA, highly efficient chiral nematic induction was achieved. Especially, the dimer 5 exhibited the βM value of +1800 μm−1. 相似文献
103.
Shigeyuki Yamada 《Tetrahedron》2008,64(19):4215-4223
On treating perfluorocyclopentene with bis(tributylstannyl)cyanocuprate in THF at −78 °C for 1 h, perfluorocyclopentenylstannane was obtained in good yield. The reaction of the fluorinated vinylstannane with n-BuLi in THF at −78 °C for 1 h, followed by addition of carbonyl compounds, gave the corresponding allyl alcohols in good yields. On the other hand, Pd(0)-catalyzed cross-coupling reaction of perfluorocyclopentenylstannane with benzyl chloroformate in THF at reflux temperature for 2 h proceeded smoothly to form the decarbonated coupling product in high yield. 相似文献
104.
A system to perform post-column derivatization capillary electrochromatography (CEC) was developed for the first time. The system mainly included a 4-microm (O.D.) silica packed column (200 mm effective length x 0.1 mm inner diameter I.D.) with micro-magnetic particles (MMPs) frits, a T-junction connector, an in-line fluorescence detector and a high-voltage power supply. The system was evaluated by using histamine (HA) as a standard biogenic amine for this study. A 5 microM HA solution was loaded at the anodic site of the capillary column by applying 3 kV for 5s. Then, HA was electrophoretically eluted with a 20mM phosphate buffer (pH 7) by applying 3 kV, and was derivatized with 3mM o-phthalaldehyde (OPA)/N-acetylcysteine (NAC) in 100 mM borate (pH 10), which was continuously delivered through the reagent-loading capillary tube by gravity into the T-junction connector. HA derivative was finally detected with the in-line fluorescence detector (lambda(Ex)=340 nm, lambda(Em)=450 nm) at 9.7 min after sample loading. To test the utility of this system, it was next employed for its ability to detect the presence of HA and other kinds of biogenic amines, including cadaverine (Cad), spermidine (Spm) and tyramine (Tyr) in tuna-meat, once the validity of the method had been confirmed. 相似文献
105.
The ruthenium tetroxide (RuO(4)) oxidation of cyclic ene-carbamates resulted in the endo-cyclic carbon-carbon double bond cleavage to afford the corresponding omega-(N-formylamino)carboxylic acids in good yields. Substituted cyclic ene-carbamates derived from (3R)-3-hydroxypiperidine hydrochloride were converted into the N-Boc 4-aminobutyric acids by utilization of the RuO(4) oxidation as the key step, which were further transformed into (3R)-4-amino-3-hydroxybutyric acid, an important key intermediate for the synthesis of L-carnitine. 相似文献
106.
Horiuchi T Takahashi M Kikuchi J Yokoyama S Maeda H 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,174(1):34-42
A previous report by Kelly et al. [J. Am. Chem. Soc. 124 (2002) 12013] indicated that the ionic conductivity of aqueous solution produces a significant contribution to the sensitivity loss in high-resolution NMR equipped with a cryogenically cooled probe. The loss in a sample solution contains two contributions: one from the ionic conductivity and the other from the dielectric loss; the latter is especially important at high frequencies such as above 900 MHz. Here, we investigated the effect of the dielectric conductivity on the quality factor of a 930 MHz cryogenic probe model; in particular, it deals with the ionic aqueous solutions and organic solvents commonly used for NMR in biological research and the chemistry of natural compounds. The sample quality factor, Qs, at first increases with the real part of the relative dielectric permittivity epsilon' and then saturates. In the case of polar organic solvents, the transverse electric field on the sample decreases with epsilon', resulting in an increase of Qs. In the case of non-polar organic solvents, the dielectric conductivity is so small that the gradient of the increase is steep, resulting in much larger Qs though the epsilon' is small. The effect of the transverse electric field is negligible if the epsilon' becomes large, thus the loss for ionic aqueous solution is mainly governed by a loop current induced in the sample solution. As the induced electromotive force is independent of the epsilon', the Qs is saturated at high values of epsilon'. Based on the Qs obtained with the cryogenic probe model, the sensitivity for the cryogenic probe is expected to be as follows: the loss in sensitivity by loading water is more than 66%, i.e., the effect of the dielectric conductivity of water is remarkable at high frequencies; polar organic solvent suffers much larger losses, which is due to the enhancement of the effective sample resistance by the effect of epsilon'; a non-polar organic solvent is nearly free of the sensitivity loss as the dielectric conductivity is negligible; the reverse micelle behaves similarly. 相似文献
107.
Yamauchi T Mizutani T Wada K Horii S Furukawa H Masaoka S Chang HC Kitagawa S 《Chemical communications (Cambridge, England)》2005,(10):1309-1311
Bilindiones and biladienones carrying aryl groups at the meso positions were prepared using coupled oxidation reactions of iron tetraarylporphyrins in 20-63% yield. 相似文献
108.
109.
Nonomura Y Komura S Tsujii K 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9409-9411
Interfaces adsorbing solid particles have recently attracted great attentions in the field of materials science, because they are useful as templates of well-ordered particle arrays or of microstructured hollow spheres. The solid particles are adsorbed at the interfaces and form self-assembled structures when the particles have suitable wettability to both fluids. Here, we show theoretically how the microstructure on the particle surface affects their adsorption properties. The physical properties of the interface adsorbing a particle will be described with consideration for surface area magnification due to the microstructure. The microstructure on the surface changes drastically the wettability and the equilibrium position of the adsorbed particle and prevents the particle from adsorption at the interface. The range of the interfacial tensions at which the particle is adsorbed becomes narrower with the increase of the magnification. On the other hand, the particle which is partially covered with the microstructured surface is adsorbed firmly at the interface in an oriented state. We should consider not only the interfacial tensions but also the surface structure to control the adsorption behavior of the particle. 相似文献
110.