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排序方式: 共有450条查询结果,搜索用时 15 毫秒
441.
When the esters of arylboronic acids with 2,2-dimethylpropan-1,3-diol were treated with a catalytic amount of [Rh(OH)(cod)]2 in the presence of 1,3-bis(diphenylphosphino)propane and CsF in dioxane at 60 degrees C under carbon dioxide atmosphere, the benzoic acid derivatives were obtained in good yields. Reactions of alkenylboronic esters also proceeded under similar conditions to give alpha,beta-unsaturated carboxylic acids. As these boronic esters are now easily available through coupling or direct borylation reactions, this method would be a useful method for the preparation of various functionalized aryl- and alkenyl-carboxylic acids. 相似文献
442.
Eileen Hao Yu Yoko Himuro Madoka Takai Kazuhiko Ishihara 《Applied biochemistry and biotechnology》2010,160(4):1094-1101
In this study, the feasibility of introducing redox property to an amphiphilic phospholipid polymer (PMBN) was investigated.
The active ester group in the side chain of the polymer was used to react with pyrroloquinoline quinine (PQQ). Redox peaks
that corresponded to PQQ redox potentials were observed after the modification. Glucose oxidase was immobilized to the modified
polymer. Electrochemical oxidation of glucose was carried out with the polymer electrode. The oxidation current increased
with elevating glucose concentration indicating electron transfer established between the electrode and enzyme. It suggests
that by modification, PMBN is possible to use for enzyme electrode for bioelectronics. 相似文献
443.
Yoichiro Kuninobu Dr. Atsushi Kawata Mitsumi Nishi Salprima Yudha S. Jingjin Chen Kazuhiko Takai Prof. Dr. 《化学:亚洲杂志》2009,4(9):1424-1433
Treatment of alkynes with cyclic and acyclic 1,3‐dicarbonyl compounds in the presence of a catalytic amount of a rhenium or manganese complex gives ring‐expanded and carbon‐chain extension products, respectively. In these reactions, alkynes insert into a non‐strained carbon–carbon single bond of 1,3‐dicarbonyl compounds. The ring‐expansion reaction is also promoted by the addition of 4‐Å molecular sieves instead of a catalytic amount of an isocyanide. 相似文献
444.
H. Sugimura H. Shiroyama O. Takai N. Nakagiri 《Applied Physics A: Materials Science & Processing》2001,72(8):S285-S289
Frictional properties of organosilane self-assembled monolayers (SAMs) and hydrated silicon oxide (SiOH) surfaces on a single sample substrate were studied; the frictional force difference between the surfaces was measured by employing one as a standard. Using a lateral force microscope (LFM), differential frictional force microscopic data were obtained by measuring the difference in the friction forces of the two surfaces with respect to the vertical load force applied to the LFM probe. The SAMs were prepared from n-octadecyltrimethoxysilane [ODS, H3C(CH2)17Si(OCH3)3], n-(6-aminohexyl) aminopropyltrimethoxysilane [AHAPS, H2N(CH2)6NH(CH2)3Si(OCH3)3], 3,3,3-trifluoropropyltrimethoxysilane [FAS3, F3C(CH2)2Si(OCH3)3] and heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane [FAS17, F3C(CF2)7(CH2)2Si(OCH3)3] by chemical vapor deposition. In the vertical force range of 0 to 600 nN, the SAMs showed no damage at all, and frictional force on the SAM surfaces increased linearly with the vertical force. The order of the frictional force magnitudes determined with the SiOH-terminated probe was SiOH > AHAPS > FAS3 > FAS17 > ODS. In addition, the frictional force difference did not become zero even at a vertical force of 0 nN, that is, the frictional differences could even be imaged by LFM through probe-sample adhesion. 相似文献
445.
Ho-Hi Lee Kouji Kimura Takatomo Takai Hitoshi Senda Akio kuwae Kazuhiko Hanai 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1999,55(14):2877
Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state 13C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm−1 region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the C=O stretching band is split by the crystal field for both polymorphs. 相似文献
446.
447.
Partly as a result of the high solution viscosity of bacterial cellulose, carboxymethylcellulose (CMC) derived from this material exhibits shear-thinning and thixotropic properties. With suitable sample treatment, the CMC solution shows gel-like rheology suggesting the presence of a three-dimensional network. This behavior is consistent with heterogeneous substitution of the carboxymethyl functionality on the polymer chains. For comparison, bacterial cellulose is also degraded by either acid or ultrasound to reduce its molecular weight and converted to CMC. The flow behavior of the resulting CMC solutions is nearly Newtonian with slight shear thinning but no thixotropy, suggesting that the carboxymethylation reaction is almost random. 相似文献
448.
Implementing chemical reactivity into synthetic supramolecular polymers based on π-conjugated molecules has been of great interest to create functional materials with spatiotemporal dynamic properties. However, the development of an in situ chemical reaction within supramolecular polymers is still in its infancy, because one needs to design optimal π-conjugated monomers having excellent reactivity under mild conditions possibly without byproducts or a catalyst. Herein we report the synthesis of a supramolecular polymer based on ethynyl core-substituted naphthalenediimide (S-NDI2) molecules that react with various amines quantitatively in a nonpolar solvent, without a catalyst, at 298 K. Most interestingly, the in situ reaction of the S-NDI2 supramolecular polymer with a linear aliphatic diamine proceeded much faster than the homogeneous reaction of a monomeric naphthalenediimide with the same diamine, affording diamine-linked S-NDI2 oligomers and polymers. The acceleration of in situ hydroamination was presumably due to rapid intra-supramolecular cross-linking between ethynyl and amino groups fixed in close proximity within the supramolecular polymer. Such intra-supramolecular cross-linking did not occur efficiently with an incompatible diamine. The systematic kinetic studies of in situ catalyst-free hydroamination within supramolecular polymers provide us with a useful, facile and versatile tool kit for designing dynamic supramolecular polymeric materials based on electron-deficient π-conjugated monomers.A supramolecular polymer based on ethynyl core-substituted naphthalenediimides reacted with various amines quantitatively without a catalyst, exhibiting unconventional reaction kinetics and products. 相似文献
449.
450.