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981.
M. Baudler J. Dobbers Ch. P. Schner M. Borgardt D. Rackwitz U. M. Krause 《无机化学与普通化学杂志》1995,621(9):1459-1465
Contributions to the Chemistry of Phosphorus. 236. On Several Physical and Chemical Properties of Diphosphane(4) The density of diphosphane(4) has been measured between ?78°C and +18°C and the value d420 = 1.014 · 0.002 extrapolated. The refractive index of P2H4 was determined to be n20 = 1.66 ± 0.01. The surface tension at 0°C and ?50°C was measured to be σ = 34 and 42 dyn · cm?1, respectively. In the UV absorption spectrum, gaseous P2H4 exhibits a broad absorption band at λmax = 2 220 Å, in n-hexane solution, this band is shifted somewhat to shorter wave-lengths. The molar extinction coefficient was determined to be ? ≈? 900 1 · mol?1 · cm?1. As a result of photolytic decomposition, absorptions for PH3 and more phosphorus-rich hydrides also occur. The solubility behavior of P2H4 in various organic solvents and the stabilities of the resultant solutions have been investigated. At 0°C, the solubility of diphosphane(4) in water was found to be ± 035 ± 0.003 g P2H4/100 g solution and that of water in diphosphane(4) to be 43.2 ± 1.6 g H2O/100 g solution. The system diphosphane(4)/methanol also exhibits a miscibility anomaly. The IR spectra of liquid P2H4 and of its solutions in various solvents revealed, in accord with the results of nuclear magnetic resonance spectroscopy [7], that diphosphane(4) is practically not associated. Weak interactions through hydrogen bridging bonds occur with pyridine and methanol in which P2H4 serves as the proton donor and, in the latter case, also as proton acceptor. For the thermolysis of diphosphane(4), it has been found that the primary step comprises a disproportionation with inter-molecular elimination of PH3 and formation of triphosphane(5). With further progress of the thermolysis, in dependence on the reaction conditions, mixtures of various phosphanes of differing composition are formed. Photolysis gives rise to phosphane mixtures having similar compositions. With aqueous silver salt and iodine solutions, diphosphane(4) reacts as a reducing agent; with sodium hydroxide solution, it reacts by a slow disproportionation as well as by formation and degradation of the subsequently formed polyphosphides. On reaction with triphenylmethyl, triphenylmethane and a yellow solid of varying composition are formed. The reaction of diazomethane with diphosphane(4) leads to the preferential insertion of the carbene in the P? P bond and formation of methylenebis(phosphane). 相似文献
982.
Zusammenfassung Zwischen dem Aldehydproton und dem Fluoratom des 3-Nitro-5-fluor-salicylaldehyds gibt es eine stereospezifische Spin-Spin-Kopplung, mit deren Hilfe die Aldehydgruppenstellung der in chlorierten Kohlenwasserstoffen vorherrschenden Konformation bestimmt wird.
Mit 2 Abbildungen
Aus der Dissertation vonGotthard Krause, Univ. Bonn 1966 (D5). 相似文献
Hydrogen bonding and stereospecific long-range spin coupling in 3-nitro-5-fluoro-salicylaldehyde
The stereospecific nature of the long-range spin coupling between the aldehydic proton and the fluorine atom is used for determining the conformation of 3-nitro-5-fluoro-salicylaldehyde predominating in CCl4 and in CHCl3.
Mit 2 Abbildungen
Aus der Dissertation vonGotthard Krause, Univ. Bonn 1966 (D5). 相似文献
983.
984.
In the reaction of N,N-dialkyl-dichloromethaniminium chlorides 11 with 2-aminoacetophenones 12 , a general and simple route to heretofore unknown 5-aryl-substituted 2-(dialkylamino)-1,3-oxazolium salts 13 and 5-aryl-substituted 2-(dialkylamino)oxazoles 14 was found. From the 2-(dialkylamino)-1,3-oxazoles 14 , the corresponding oxazolium salts 13 were obtained after alkylation with (MeO)2SO2. The new oxazolium salts 13 were converted to 1-substituted 4-aryl-2-(dialkylamino)-1H-imidazoles 9 by treatment with NH4OAc. The possible use of these 1H-imidazoles as dye educts was explored. Analytical data, as well as AM1 calculations, reveal some remarkable differences between the structures of the neutral imidazoles 9 and their positively charged oxazolium precursors 13 . 相似文献
985.
986.
Manfred Knrgen Uwe Heuert Horst Schneider Dirk Kuckling Sven Richter Karl-Friedrich Arndt 《Macromolecular Symposia》1999,145(1):83-94
The kinetics of diffusion in polymers ranges from simple Fickian diffusion to higher order diffusion, such as Case II diffusion1-2). The conventional method for determining the characteristics of solvents into polymer matrices is by measuring the mass uptake of the polymer as the solvent penetrates the matrix. However, since such measurements perform observations at a macroscopic level, little information has been obtained relating to the nature of the solvent in the polymer matrix and the mechanisms of the processes that control the diffusion. Nuclear magnetic resonance (NMR) imaging (‘MRI’) has been used to observe the penetration of solvents into solid systems in realtime. The method provides a one- or more-dimensional image of the density and the mobility of the solvent in a material or of the network changes of the material itself due to the softening influence of the solvent. The first (imaging of the solvent) can be used for a quantitative measurement of the diffusion whereas the observation of the network gives information about the changing of the network (mobility, de-crystallization…) during the swelling process. For example the diffusion of organic solvents in some polymeric materials (natural rubber, water gels (PNIPAAm), and nematic diblock-copolymers) are investigated. 相似文献
987.
988.
Joachim Armbruster Stefan Grabowski Thomas Ruch Horst Prinzbach 《Angewandte Chemie (International ed. in English)》1998,37(16):2242-2245
Technical olefins and azodicarbonic ester are the starting materials for C2-symmetrical C16 and C12 1,4-diamino-2,3-diol building blocks (see structure), which are of interest for a variable access to potentially bioactive compounds (peptide mimetics, enzyme inhibitors). MOM = methoxymethyl. 相似文献
989.
Yue-Qing Zheng Horst Borrmann Yuri Grin Karl Peters Hans Georg von Schnering 《无机化学与普通化学杂志》1999,625(12):2115-2119
The reaction of W6Br12 with AgBr in evacuated silica tubes (temperature gradient 925 K/915 K) yielded brownish black octahedra of Ag[W6Br14] ( I ) and yellowish green platelets of Ag2[W6Br14] ( II ) both in the low temperature zone. ( I ) crystallizes cubically (Pn3 (no. 201); a = 13.355 Å, Z = 4) and ( II ) monoclinically (P21/c (no. 14); a = 9.384 Å, b = 15.383 Å, c = 9.522 Å, β = 117.34°, Z = 2). Both crystal structures contain isolated cluster anions, namely [(W6Bri8)Bra6]1– and [(W6Bri8)Bra6])]2–, respectively, with the mean distances and angles: ( I ) d(W–W) = 2.648 Å, d(W–Bri) = 2.617 Å, d(W–Bra) = 2.575 Å, d(Bri…Bri) = 3.700 Å, d(Bri…Bra) = 3.692 Å, ∠W–Bri–W = 60.78°. ( II ) d(W–W) = 2.633 Å, d(W–Bri) = 2.624 Å, d(W–Bra) = 2.613 Å, d(Bri…Bri) = 3.710 Å, d(Bri…Bra) = 3.707 Å, ∠W–Bri–W = 60.23°. The Ag+ cations are trigonal antiprismatically coordinated in ( I ) with d(Ag–Br) = 2.855 Å, but distorted trigonally planar in ( II ) with d(Ag–Br) = 2.588–2.672 Å. The structural details of hitherto known compounds with [W6Br14] anions will be discussed. 相似文献
990.
Martin Kantlehner Dirk Finsinger Jrg Meyer Patricia Schaffner Alfred Jonczyk Beate Diefenbach Berthold Nies Horst Kessler 《Angewandte Chemie (International ed. in English)》1999,38(4):560-562
Osteoblasts: yes, platelets: no! Bone implants have to be integrated with the surrounding tissue to allow a smooth and stable connection. A new procedure is shown which is based on covalent linking of a highly selective RGD peptide to a poly(methyl methacrylate) (PMMA) material (see picture). Osteoblasts very effectively bind to the treated surface and are stimulated to proliferate. 相似文献