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951.
952.
Christian Haase 《Tetrahedron》2009,65(23):4530-3950
The acid-mediated reaction of amines with γ-alkylidenebutenolides, readily available by cyclization of 1,3-bis(silyloxy)-1,3-butadienes with oxalyl chloride, allows a convenient synthesis of a variety of 5-alkylidene-2,5-dihydropyrrol-2-ones. The configuration of the exocyclic double bond of the products depends on the substitution pattern of the products. 相似文献
953.
Christian Zillober 《Numerical Algorithms》2001,27(3):265-289
The method of moving asymptotes (MMA) and its globally convergent extension SCP (sequential convex programming) are known to work well for certain problems arising in structural optimization. In this paper, the methods are extended for a general mathematical programming framework and a new scheme to update certain penalty parameters is defined, which leads to a considerable improvement in the performance. Properties of the approximation functions are outlined in detail. All convergence results of the traditional methods are preserved. 相似文献
954.
955.
956.
Christian Slugovc Eva Rüba Roland Schmid Karl Kirchner Kurt Mereiter 《Monatshefte für Chemie / Chemical Monthly》2000,131(12):1241-1251
Summary. This article gives an overview of recent chemistry based on the tris-acetonitrile complex [RuCp(CH3CN)3]+. Due to the labile nature of the CH3CN ligands, substitution reactions are a dominant feature of this complex. Important derivatives are the highly reactive complexes
[RuCp(PR
3)(CH3CN)2]+ which are a source of the 14e− fragment [RuCp(PR
3)]+. These species are catalytically active in the redox isomerization of allyl alcohols to give aldehydes and ketones. Furthermore,
the cationic complex [RuCp(κ1(P),η2-PPh2CH2CH2CH*CH2)(CH3CN)]PF6 derived from the reaction of [RuCp(CH3CN)3]+ with PPh2CH2CH2CH*CH2 is a model compound for studying coupling reactions of olefins and acetylenes. In addition, [RuCp(CH3CN)3]+ is a valuable precursor for the synthesis of configurationally stable chiral three-legged piano-stool ruthenium complexes.
These are currently being intensively investigated as Lewis acid catalysts in asymmetric synthesis.
Received May 31, 2000. Accepted June 13, 2000 相似文献
957.
A model of the Lu-Hamilton kind is applied to the study of critical behavior of the magnetized solar atmosphere. The main novelty is that its driving is done via sources undergoing a diffusion. This mimics the effect of a virtual turbulent substrate forcing the system. The system exhibits power-law statistics not only in the size of the flares, but also in the distribution of the waiting times. 相似文献
958.
Andreas Winter Christian Friebe Manuela Chiper Martin D. Hager Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(16):4083-4098
A series of main‐chain metallopolymers ( P1–P10 ) was prepared by the self‐assembly of rigid‐linear π‐conjugated bis(terpyridine) monomers ( 1–10 ) with ZnII ions and was fully characterized. The polymerization was additionally confirmed by UV/vis titration experiments. A strong increase in viscosities (around 1.6 times) relative to those of the monomer solutions was found. The thermal stability of P1–P10 compared with that of 1–10 was enhanced as a result of the metallopolymerization. The electro‐optical properties of the materials were investigated in detail. Tuning of the electrochemical and photophysical properties was enabled; thus, bright purple to green photoluminescent (PL) emission (PL quantum yields of 0.12–0.81) for P1–P10 was observed in solution with the emission color strongly depending on the nature of the π‐conjugated bis(terpyridine) system. Thin homogeneous films of P6 were prepared by solution processing, that is, spin‐coating and inkjet‐printing, and exhibited intense yellow PL emission in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4083–4098, 2009 相似文献
959.
Cláudia M. Morais Valérie Montouillout Michael Deschamps Dinu Iuga Franck Fayon Filipe A. A. Paz João Rocha Christian Fernandez Dominique Massiot 《Magnetic resonance in chemistry : MRC》2009,47(11):942-947
From one‐ to two‐ and three‐dimensional MAS NMR solid‐state experiments involving 31P and 27Al, we show that the structure of microporous alumino‐phosphate AlPO4‐40 contains at least four times more sites than expected, and we attribute two types of AlIV sites. The newly described 27Al‐31P MQ‐HMQC opens new possibilities of describing details of three‐dimensional bounded networks. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
960.
Six different calixarene-bonded phases were characterized by analyzing 36 and 26 solutes at pH 3 and 7, respectively. Dolan and Snyder's multiple term linear equation was used to correlate retention factors k' to parameters of the solutes and columns. The column parameters have been related to molecular properties of the stationary phases and new suggestions were made for the interpretation of steric selectivity. Ionic and polar interactions have been found dependent on pH value, while steric interactions are less dependent and hydrophobic interactions remain unchanged. Distinct differences of the supported interactions were confirmed between the calixarene-bonded and the common alkyl-bonded silicas. By use of the parameters, values of k' can be estimated with an average deviation of 2.50 and 7.92% at low and neutral pH-value, respectively. 相似文献