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991.
Ruthenium Complexes of Tripodal Ligands with Pyridine and Triazole Arms: Subtle Tuning of Thermal,Electrochemical, and Photochemical Reactivity 下载免费PDF全文
Fritz Weisser Stephan Hohloch Sebastian Plebst Dr. David Schweinfurth Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):781-793
Electrochemical and photochemical bond‐activation steps are important for a variety of chemical transformations. We present here four new complexes, [Ru(Ln)(dmso)(Cl)]PF6 ( 1 – 4 ), where Ln is a tripodal amine ligand with 4?n pyridylmethyl arms and n?1 triazolylmethyl arms. Structural comparisons show that the triazoles bind closer to the Ru center than the pyridines. For L2, two isomers (with respect to the position of the triazole arm, equatorial or axial), trans‐ 2 sym and trans‐ 2 un, could be separated and compared. The increase in the number of the triazole arms in the ligand has almost no effect on the RuII/RuIII oxidation potentials, but it increases the stability of the Ru?Sdmso bond. Hence, the oxidation waves become more reversible from trans‐ 1 to trans‐ 4 , and whereas the dmso ligand readily dissociates from trans‐ 1 upon heating or irradiation with UV light, the Ru?S bond of trans‐ 4 remains perfectly stable under the same conditions. The strength of the Ru?S bond is not only influenced by the number of triazole arms but also by their position, as evidenced by the difference in redox behavior and reactivity of the two isomers, trans‐ 2 sym and trans‐ 2 un. A mechanistic picture for the electrochemical, thermal, and photochemical bond activation is discussed with data from NMR spectroscopy, cyclic voltammetry, and spectroelectrochemistry. 相似文献
992.
Stefan Büttner Alina Bunescu Sebastian Reimann T. H. Tam Dang Thomas Pundt Renske Klassen Andreas Schmidt Nazken K. Kelzhanova Zharylkasyn A. Abilov Tariel V. Ghochikyan Ashot S. Saghiyan Alexander Villinger Helmut Reinke Anke Spannenberg Peter Langer 《Helvetica chimica acta》2013,96(1):44-58
Functionalized 5‐alkyl‐3‐(trifluoromethyl)phenols were prepared by formal [3+3] cyclization of 1,3‐bis(silyloxy)buta‐1,3‐dienes with 1,1,1‐trifluoro‐4‐(silyloxy)alk‐3‐en‐2‐ones derived from 1,1,1‐trifluoroalkane‐2,4‐diones. The latter were prepared by condensation of the dianion of 1,1,1‐trifluoropentane‐2,4‐dione with alkyl halides. 相似文献
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995.
Sebastian Mendrek Aleksandra Mendrek Hans‐Jürgen Adler Wojciech Walach Andrzej Dworak Dirk Kuckling 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2488-2499
New, water soluble poly(glycidol) (PGl) macroinitiators for atom transfer radical polymerization (ATRP) were synthesized. This new class of macroinitiators were prepared in a three‐step process. First, series of well‐defined ω‐hydroxyl functional poly(glycidol acetal)s with different molecular weights was synthesized via anionic polymerization followed by quantitative termination of anionically growing active sites. End capping was achieved by treatment of living chain ends with water. The living nature of the system and termination reaction is discussed. In the second stage, monofunctional poly(glycidol acetal)s were functionalized by esterification with 2‐chloropropionyl chloride. Finally, selective deprotection (hydrolysis) of acetal protective groups was performed. As simultaneous partial cleavage of ester bond of attached ATRP moieties was unavoidable, the final functionality of macroinitiator calculated from 1H NMR varied in the range 85–95%. The obtained (2‐chloropropionyl) poly(glycidol) macroinitiator with DP = 55 and 90% functionality was successfully used in ATRP polymerization of N‐isopropylacrylamide (NIPAAm) at room temperature in the DMF/water mixture. Linear block copolymers with relatively narrow molecular weight distribution and controlled composition were obtained and characterized with 1H NMR and SEC‐MALLS measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2488–2499, 2008 相似文献
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We have investigated the dynamics of adiabatic electron transfer reactions at metal electrodes using a Hamiltonian suggested by Schmickler (J. Electroanal. Chem., 204 (1986) 31). We show that in the adiabatic limit the problem reduces to that of dynamics of a single variable, the shift of the ionic orbital caused by its interaction with the solvent. This variable is identified as the reaction co-ordinate for the problem and we show that in certain limits, it obeys a non-linear Volterra type integral equation, with a stochastic inhomogeneous term. For an inhomogenous term with the autocorrelation function decaying exponentially, this may be converted into a differential equation for Brownian motion. This equation can be analysed to obtain the rate, through the associated Fokker-Planck equation. The rate so obtained, has a correction to the pre-exponential factor obtained by Schmickler. A possible extension to inner sphere reactions is also discussed. 相似文献
998.
N. Erdmann V. Sebastian V.N. Fedoseyev M. Hannawald G. Huber T. Kautzsch K.-L. Kratz V.I. Mishin M. Nunnemann G. Passler N. Trautmann 《Applied physics. B, Lasers and optics》1998,66(4):431-433
1 =228.8 nm). Laser light with an average power of 2 mW was obtained after frequency tripling and was successfully used for
RIS test measurements on cadmium with a time-of-flight mass spectrometer. The eight stable Cd isotopes could be identified
unambiguously.
Received: 6 October 1997 相似文献
999.
We consider the exact null controllability problem for the semi- linear heat equation with dissipative nonlinearity in a bounded domain of Rn . The main result of the article asserts that if the nonlinearity is even mildly superlinear, then global null controllability in an arbitrarily short time fails; instead we provide sharp estimates for the controllability time in terms of the size of the initial data. 相似文献