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81.
Complexes of the Alkali Metal Tetraphenylborates with Macrocyclic Crown Ethers Alkali metal tetraphenylborates, MB(C6H5)4 (M = Li to Cs), react in tetrahydrofuran with macrocyclic crown ethers to give complexes of the general formula MB(C6H5)4(crown)m(THF)n. Suitable single crystals for X‐ray structure analysis were grown from a solvent mixture of tetrahydrofuran and n‐hexane. The salt like complexes [Li(12‐crown‐4)(thf)][B(C6H5)4] ( 1 ), [Na(15‐crown‐5)(thf)][B(C6H5)4] ( 2 ), and [Cs(18‐crown‐6)2][B(C6H5)4] · THF ( 6 ), the mononuclear molecular complexes [KB(C6H5)4(18‐crown‐6)(thf)] ( 3 ), [RbB(C6H5)4(18‐crown‐6)] ( 4 ), and [CsB(C6H5)4(18‐crown‐6)] · THF ( 5 ), and the compound [CsB(C6H5)4(18‐crown‐6)]2[Cs(18‐crown‐6)2][B(C6H5)4] ( 7 ), which contains a binuclear molecule ([CsB(C6H5)4(18‐crown‐6)]2) beside a [Cs(18‐crown‐6)2]+ cation and a [B(C6H5)4]? anion, are described. All compounds are charactarized by infrared spectra, elemental analysis, NMR‐spectroscopy, and X‐ray single crystal structure analysis. 相似文献
82.
Structures of Polar Magnesium Organyls: Synthesis and Structure of Base Adducts of Bis(cyclopentadienyl)magnesium Eight donor‐acceptor complexes of bis(cyclopentadienyl)magnesium ( 1 ) with N‐ and O‐donor Lewis bases have been synthesized and characterized by X‐ray structure analysis. With acetonitrile, dimethoxyethane, diethyleneglycoldimethylether, dioxane, and tetramethylethylenediamine simple 1:1 adducts are formed ( 2 – 6 ). In some cases a change of the hapticity of one cyclopentadienylring from η5 to η2 or η1 is observed ( 4 – 6 ). In the adduct with pentamethyldiethylenetriamine ( 7 ) one C5H5‐ring is removed from the magnesium atom forming the cation [Mg(C5H5)(PMDTA)]+ and an uncoordinated five‐ring anion. With the crown ether 15‐crown‐5 the two ionic Mg compounds 8 and 9 are formed which have a [Mg(15‐crown‐5)L2]2+‐cation [L = pyridine, THF] and two uncoordinated cyclopentadienyl anions. Cyclopentadienyl‐methyl‐magnesium reacts with 15‐crown‐5 to the salt [Mg(CH3)(15‐crown‐5)]+ C5H5? ( 10 ) which has also a free cyclopentadienyl anion. 相似文献
83.
Pb(18‐crown‐6)Cl2 and Hg(18‐crown‐6)I2 are obtained as transparent colourless crystals of needle and hexagonal shape, respectively, by isothermal evaporation of their dichloromethane solutions. Pb(18‐crown‐6)Cl2 crystallizes with the trigonal crystal system [ , no. 148, a = b = 1176.3(2), c = 1191.8(3) pm, V = 1428.2(5) 106·pm3, Z = 3] whereas Hg(18‐crown‐6)I2 crystallizes with the orthorhombic crystal system (Pnma, no. 62, a = 1613.9(2) pm, b = 2822.2(5) pm, c = 841.3(1) pm, V = 3832(1)106·pm3, Z = 8). Both compounds are characterized by linear MX2 (HgI2 or PbCl2) molecular units which are encrypted by the crown ether. In both cases, the divalent metal ion resides in the middle of the crown ether resulting in a hexagonal bipyramidal coordination environment for the metal cations. The molecular symmetry comes close to D3d. Hg(18‐crown‐6)I2 and Pb(18‐crown‐6)Cl2 differ in the way the single MX2@18‐crown‐6 units are packed. Whereas the Hg(18‐crown‐6)I2 molecules are arranged in a (distorted) cubic closest packing, the Pb(18‐crown‐6)Cl2 molecules adopt a hexagonal closest packing. 相似文献
84.
Daniel Kogelnig Anna Regelsberger Anja Stojanovic Franz Jirsa Regina Krachler Bernhard K. Keppler 《Monatshefte für Chemie / Chemical Monthly》2011,253(3):769-772
Abstract
Extraction of Zn(II) from aqueous solution using polymer inclusion membranes based on poly(vinyl chloride) containing the phosphonium-based ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos? IL 101) is described. Zn(II) could efficiently be extracted from 5 M hydrochloric acid solution with membranes containing 30 wt% Cyphos IL 101, whereas back-extraction was successfully achieved with 1 M sulfuric acid. Prepared membranes were evaluated in terms of stability in air as well as in terms of leaching of the ionic liquid from the membranes in aqueous solution. 相似文献85.
86.
The haptotropic migration of Cr(CO)3, Mo(CO)3 and W(CO)3 moieties on a substituted phenanthrene has been studied theoretically using gradient-corrected density functional theory. The stationary points (minima and transition states) on the energy hypersurface characterizing the migrating process of the metal fragment over the aromatic system have been located. Furthermore, the energetic and structural differences between complexes of the three metals Cr, Mo and W and the effect of a high substitution of one arene ring on the reaction energy profile have been analyzed. The possibility to design a molecular switch based on the substituent pair R = O−/OH is investigated. It is concluded that the Mo and W complexes undergo a haptotropic migration more easily than the corresponding Cr system. 相似文献
87.
Schweizer E Hoffmann-Röder A Olsen JA Seiler P Obst-Sander U Wagner B Kansy M Banner DW Diederich F 《Organic & biomolecular chemistry》2006,4(12):2364-2375
Two series of tricyclic inhibitors of the serine protease thrombin, imides (+/-)-1-(+/-)-8 and lactams (+/-)-9-(+/-)-13, were analysed to evaluate contributions of orthogonal multipolar interactions with the backbone C=O moiety of Asn98 to the free enthalpy of protein-ligand complexation. The lactam derivatives are much more potent and more selective inhibitors (K(i) values between 0.065 and 0.005 microM, selectivity for thrombin over trypsin between 361- and 1609-fold) than the imide compounds (Ki values between 0.057 and 23.7 microM, selectivity for thrombin over trypsin between 3- and 67-fold). The increase in potency and selectivity is explained by the favorable occupancy of the P-pocket of thrombin by the additional isopropyl substituent in the lactam derivatives. The nature of the substituent on the benzyl ring filling the D pocket strongly influences binding potency in the imide series, with Ki values increasing in the sequence: F < OCH2O < Cl < H < OMe < OH < N(pyr)< Br. This sequence can be explained by both steric fit and the occurrence of orthogonal multipolar interactions with the backbone C[double bond, length as m-dash]O moiety of Asn98. In contrast, the substituent on the benzyl ring hardly affects the ligand potency in the lactam series. This discrepancy was clarified by the comparison of X-ray structures solved for co-crystals of thrombin with imide and lactam ligands. Whereas the benzyl substituents in the imide inhibitors are sufficiently close (< or =3.5 Angstroms) to the C=O group of Asn98 to allow for attractive orthogonal multipolar interactions, the distances in the lactam series are too large (> or =4 Angstroms) for attractive dipolar contacts to be effective. 相似文献
88.
Parvin Zare Maria Mahrova Emilia Tojo Anja Stojanovic Wolfgang H. Binder 《Journal of polymer science. Part A, Polymer chemistry》2013,51(1):190-202
A facile synthetic route for the preparation of dicationic ethylene glycol based‐ionic liquids (ILs) via the azide/alkyne “click” reaction is presented. The copper(I) catalyzed, microwave‐assisted azide/alkyne “click” reaction between diazido‐ethylene glycols and the corresponding alkyne containing IL‐head group enables a simple preparation of different sets of poly(ethylene glycol)‐based ILs. Beside tetra‐ and hexa(ethylene glycol)‐based ILs, also oligomeric (Mn = 400 g/mol) and polymeric ILs (Mn up to 1550 g/mol) could be prepared in good yield and with full conversion of the ionic head group. The prepared ILs were extensively characterized via NMR spectroscopy and ESI‐time‐of‐flight (TOF) mass spectroscopy, revealing the formation of multiply charged ions in the negative mode. Thermal stability proved to be exceptionally high (up to 300 °C) together with low glass‐transition temperatures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
89.
90.