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91.
Hanneke M. L. Lambermont‐Thijs Richard Hoogenboom Charles‐André Fustin Cécile Bomal‐D'Haese Jean‐François Gohy Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(2):515-522
The solution properties of random and block copolymers based on 2‐ethyl‐2‐oxazoline (EtOx) and 2‐nonyl‐2‐oxazoline (NonOx) were investigated in binary solvent mixtures ranging from pure water to pure ethanol. The solubility phase diagrams for the random and block copolymers revealed solubility (after heating), insolubility, dispersions, micellization as well as lower critical solution temperature (LCST) and upper critical solution temperature behavior. The random and block copolymers containing over 60 mol % pNonOx were found to be solubilized in ethanol upon heating, whereas the dissolution temperature of the block copolymers was found to be much higher than for the random copolymers due to the higher extent of crystallinity. Furthermore, the block copolymer containing 10 mol % pNonOx exhibited a LCST in aqueous solution at 68.7 °C, whereas the LCST for the random copolymer was found to be only 20.8 °C based on the formation of hydrophobic microdomains in the block copolymer. The random copolymer displayed a small increase in LCST up to a solvent mixture of 9 wt % EtOH, whereas further increase of ethanol led to a decrease in LCST, which is probably due to the “water‐breaking” effect causing an increased attraction between ethanol and the hydrophobic part of the copolymer. In addition, the EtOx‐NonOx block copolymers revealed the formation of micelles and dynamic light scattering demonstrated that the micellar size is increasing with increasing the ethanol content due to the enhanced solubility of EtOx. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 515–522, 2009 相似文献
92.
The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique. 相似文献
93.
José Bonilla-Cruz Carlos Guerrero-Sánchez Ulrich S. Schubert Enrique Saldívar-Guerra 《European Polymer Journal》2010,46(2):298-4769
High-throughput experimentation was used for the functionalization of polybutadiene and polyisoprene with several kinds of nitroxide moieties at 135 °C, as well as for kinetic investigations of the controlled free radical grafting of styrene and maleic anhydride onto the functionalized polydienes at 125 °C. The functionalized polymers were analyzed by GPC, 1H NMR and FT-IR and the control of the grafting process was assessed by kinetic measurements and GPC analysis. The best control in the molecular weight of the grafts was observed for the polydienes functionalized with 4-oxo-TEMPO. TEMPO functionalization did not render sufficient nitroxide moieties to achieve controlled grafting, while polydienes functionalized with other 4-hydroxy TEMPO derivatives exhibited some level of grafting control at early reaction times, which was lost in later stages of the polymerization reaction. SG1 apparently decomposed at the tested reaction temperatures, as polydienes functionalized with SG1 did not show any level of control during the grafting process. 相似文献
94.
G. Schubert R. Basner H. Kersten H. Fehske 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(3):431-440
Equilibrating gravitation by electric forces, microparticles can be confined in the plasma sheath above suitably biased local electrodes. Their position depends on the detailed structure of the plasma sheath and on the charge that the particles acquire in the surrounding plasma, that is by the electron and ion currents towards it. Bias switching experiments reveal how the charge and equilibrium position of the microparticle change upon altered sheath conditions. Above a critical bias, the particle is subject to an additional downward acceleration that cannot be explained solely by gravity and ion drag. This acceleration can be attributed to a positive charging of the particle induced by extreme out-of-equilibrium conditions of the plasma sheath in its surroundings: locally the plasma sheath can be completely deprived of electrons by means of the bias. We observe similar particle behaviors also in the afterglow of the discharge for a persisting bias voltage on the electrode: damped oscillation into a new equilibrium or (accelerated) fall according to the bias. The observed particle dynamics in locally tailored plasma sheath environments directly monitors changes in electric field structures and plasma density profiles. 相似文献
95.
T. Stuchinskaya N. Kundo L. Gogina U. Schubert A. Lorenz V. Maizlish 《Journal of molecular catalysis. A, Chemical》1999,140(3):128-240
The catalytic activity of cobalt(II) 2,9,16,23-tetrasulphophthalocyanine and cobalt(II) 2,9,16,23-tetra(chlorosulphonyl)phthalocyanine covalently bonded to a TiO2 matrix by sol–gel processing was investigated for sulfide and ethanethiol (CH3CH2SH) liquid-phase oxidation. A comparison of the kinetic data as well as the state of active component by using electron spectroscopy in dependence on precursors was carried out. Kinetic data shows that the most stable and active catalysts for ethanethiol oxidation are both CoPc(SO3H)4 and CoPc(SO2Cl)4 in TiO2 from Ti(OiPr)4, whereas in the case of Na2S oxidation in neutral medium the activity of the former is higher. 相似文献
96.
97.
Dr. Michael Jäger Dr. Helmar Görls Dr. Wolfgang Günther Prof. Dr. Ulrich S. Schubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(6):2150-2157
A new modular approach based on Pd‐catalyzed C? C bond formation is presented for the assembly of a benzannulated azocine scaffold, the key intermediate in the synthesis of functionalized azadibenzocyclooctynes (aza‐DIBOs). The intramolecular ring‐closing Heck coupling was investigated by variation of the C? X bond. The reaction rate is limited by the initial oxidative addition step and the regiochemistry strongly depends on the auxiliary phosphine. Under optimized conditions, the 8‐endo regioisomer was obtained in 71 % yield over two steps (with no protecting group chemistry) or in one pot, inclusive of C? N bond formation. The practical generation of the octyne triple bond of a prototypical N‐benzoyl aza‐DIBO, without the need for chromatographic purification, is also described. The structural features, including those of the ring‐strained cyclic octyne, were elucidated by NMR spectroscopy and X‐ray crystallographic analysis. The high reactivity of the N‐benzoyl aza‐DIBO synthesized is demonstrated in a strain‐promoted azide–alkyne cycloaddition reaction with an alkyl azide (k=0.38 M ?1 s?1). 相似文献
98.
99.
100.
ESPI solution for non-contacting MEMS-on-wafer testing 总被引:6,自引:0,他引:6
Petra Aswendt Claus-Dieter Schmidt Dirk Zielke Steffen Schubert 《Optics and Lasers in Engineering》2003,40(5-6):501-515
Rapid progress in the field of micro-electro-mechanical systems (MEMS) makes the development of appropriate measuring and testing means timely. Characterizing the mechanical properties of MEMS structures at a very early stage of manufacturing is a challenging task for quality assurance in this field. The paper describes a new solution that is based upon the vibration analysis of the microparts. The nanometer amplitudes are detected by advanced electronic speckle pattern interferometry (ESPI). A specific signal processing technique has been applied to make the solution robust. Comprehensive numerical simulations provide the theoretical base for the HNDT concept. A laboratory system for 4″ wafer has been built, and extensive tests show that such key properties as e.g. the thickness of springs or membranes can be determined exactly. Automated frequency scanning and corresponding digital image processing open the way to reliable and fast industrial systems for MEMS testing on wafer level. 相似文献