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631.
Cox NM Harding LP Jones JE Pope SJ Rice CR Adams H 《Dalton transactions (Cambridge, England : 2003)》2012,41(5):1568-1573
A new method for assessing the topology of metallosupramolecular assemblies using pyrene-appended ligands is reported. Two potentially tetradentate ligands containing one (L(1)) and two (L(2)) terminal pyrene moieties were synthesised and their complexes with Cu(+) and Cd(2+) were characterised. Photophysical measurements demonstrate that in [Cu(2)(L(1))(2)](2+), [CdL(1)](2+) and [Cu(2)(L(2))(2)](2+) the emission spectra are dominated by monomeric emission but in the cadmium complex of L(2) (where the pyrene units are in close proximity) a quenching of the luminescence coupled with weak emission at 540 nm is indicative of excimer formation. 相似文献
632.
633.
Kazuki Fukushima Daniel J. Coady Gavin O. Jones Hamid A. Almegren Abdullah M. Alabdulrahman Fares D. Alsewailem Hans W. Horn Julia E. Rice James L. Hedrick 《Journal of polymer science. Part A, Polymer chemistry》2013,51(7):1606-1611
This article describes studies on the catalytic activity of several nitrogen‐based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine‐based catalyst 1,5,7‐triazabicyclo‐[4,4,0]‐dec‐5‐ene (TBD) in the presence of short chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies prove that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pKa of the bases. For glycolysis with excess short‐chain alkanediols, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono‐alcohols and longer‐chain diols. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
634.
Glenn H. Miller William C. Rice Anthony M. Stephens III Joan V. Brennan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8-9):1211-1219
The structures of polymers formed when alkali metals are placed in the vapor phase above isoprene monomer, both in the presence and absence of carbon dioxide, were investigated. In the absence of carbon dioxide, the polymers were all gel-like and soluble. In the presence of carbon dioxide, however, insoluble popcorn polymers were formed. The structures of the soluble polymers varied from primarily cis in the case of lithium to trans for sodium and potassium initiation. In the presence of carbon dioxide the three alkali metals produced polymers having similar structures, predominantly trans. In the absence of carbon dioxide most of the polymerization proceeds anionically with the majority of the free radical sites of the initially formed radical anion being removed by a transfer reaction or by dianion formation. The presence of carbon dioxide, however, leads to the formation of car boxy late ions that prevent anionic polymerization. Then, due to the structural orientation of the radical anion on the surface, free-radical polymerization occurs, leading to microgelation and popcorn polymerization. This results from cross-linking caused by mechanical rupture of the growing chains. 相似文献
635.
636.
Mingjian Yuan Andrew H. Rice Christine K. Luscombe 《Journal of polymer science. Part A, Polymer chemistry》2011,49(3):701-711
The synthesis of four alternating copolymers using benzo[2,1‐b;3,4‐b′]dithiophene (BDP) as the common donor unit is presented. Before the synthesis, theoretical calculations that we performed predicted that the incorporation of BDP, which consists of fused dithiophene units with a benzene ring, into these polymers would produce a low‐lying highest occupied molecular orbital (HOMO) energy level. Low‐lying HOMO levels are desirable to produce high open circuit voltages (VOC) in organic bulk heterojunction (BHJ) photovoltaic devices. The polymers' structural characterization, as well as the preliminary results of their performance in BHJ devices, using (6,6)‐phenyl C61‐butyric acid methyl ester as the electron acceptor, is presented. The VOC values follow the expected trend: increasing with decreasing HOMO level of the polymer. High VOC values of 0.81 and 0.82 V have been obtained from two polymers: PBDPBT and PBDPDPP. The initial power conversion efficiency achieved in these unoptimized devices was 1.11% because of relatively low JSC values. The variation observed in the JSC values between the four polymers is discussed. Device performance is expected to increase with optimization of processing conditions for the devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
637.
Elastic reciprocity and geometric symmetry are used to constrain the expressions for stresses due to introduction of line dislocations near a half-space surface. Specifically, a relationship is shown to exist between the changes induced by dislocations of orthogonal Burgers vectors (normal and parallel to the free surface). These results are used to address inconsistencies of solutions in the literature. 相似文献