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排序方式: 共有225条查询结果,搜索用时 9 毫秒
1.
A short and highly efficient approach was applied for the total synthesis of the gypsy moth sex pheromone (+)-disparlure and its enantiomer from isopropylidene D- and L-erythrose, using a common strategy. 相似文献
2.
Alexandros A. Skordos Ivana K. Partridge 《Journal of Polymer Science.Polymer Physics》2004,42(1):146-154
This article presents a new methodology for the quantitative determination of the progress of the curing reaction of a thermosetting resin, using the results of electrical impedance spectroscopy. The method is an extension of the use of the imaginary impedance maximum as a reaction progress indicator and is based on the demonstration of a close correlation between the reaction rate, as measured by conventional differential scanning calorimetry, and the rate of change of the value of the imaginary impedance spectrum maximum. Tests on a commercial aerospace epoxy resin under both isothermal and dynamic heating conditions with calorimetry and impedance spectroscopy have demonstrated the validity of the method and set the accuracy limits involved. This technique can be used as a real-time online control tool for thermoset composite manufacturing. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 146–154, 2004 相似文献
3.
A new synthetic approach toward 2-C-methyl-d-erythritol 4-phosphate (MEP), a key intermediate in the mevalonate-independent biosynthetic pathway for isoprenoids, and deuterated analogues of its precursor, 2-C-methyl-d-erythritol acetonide, is described. This procedure uses 2-C-methyl-d-erythrose acetonide as starting material and delivers, through a mono-protection strategy, the target compounds in a short way and in high yield. 相似文献
4.
Accessing the structural diversity of pyridone alkaloids: concise total synthesis of rac-citridone A
A unique route to the structural diversity of pyridone alkaloids is described based on the concept of a common synthetic strategy. Three different core structure analogues corresponding to akanthomycin, septoriamycin A, and citridone A have been prepared by using a highly selective and novel carbocyclization reaction. 相似文献
5.
Alexandros P. SiskosAlison M. Hill 《Tetrahedron letters》2003,44(4):789-792
Labeled glycerol is a widely used biochemical probe to investigate biosynthetic pathways. A highly efficient synthesis of [1-13C, 18O]- and [1-13C, 2H2]-glycerol is described in which the 13C label is introduced using cyanide. The 18O label was introduced by a Pinner synthesis and reduction of the ester 5 allowed incorporation of the 2H labels. 相似文献
6.
Alexandros G. Koutsioubas Nikolaos Spiliopoulos Dimitris L. Anastassopoulos Alexandros A. Vradis George D. Priftis 《Surface and interface analysis : SIA》2009,41(11):897-903
The formation process of n‐alkane phosphonic acid CH3 (CH2)n?1 PO(OH)2 (n = 10,12,14,18) self‐assembled monolayers (SAMs), deposited from ethanol solutions on aluminum oxide, has been monitored in situ using surface plasmon resonance (SPR) spectroscopy. In addition, the two‐solvent approach is used to obtain both film thickness and refractive index of the fully formed adsorbed layers. A densely packed adsorbed layer is formed only for the longest molecules with n = 18. The chain length and solution concentration dependence of formation kinetics are studied, and the existence of two distinct kinetic steps is revealed. Fittings of the experimental results with various kinetic models are performed. Our analysis suggests that during the first kinetic step, a transition from a lying‐down to a standing‐up phase takes place, and the growth of this standing‐up phase is governed by second‐order kinetics. The second slow kinetic step is described by a modified first‐order Langmuir law. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Alexandros Tzachristas Marilena E. Dasenaki Reza Aalizadeh Nikolaos S. Thomaidis Charalampos Proestos 《Molecules (Basel, Switzerland)》2021,26(10)
Wine metabolomics constitutes a powerful discipline towards wine authenticity assessment through the simultaneous exploration of multiple classes of compounds in the wine matrix. Over the last decades, wines from autochthonous Greek grape varieties have become increasingly popular among wine connoisseurs, attracting great interest for their authentication and chemical characterization. In this work, 46 red wine samples from Agiorgitiko and Xinomavro grape varieties were collected from wineries in two important winemaking regions of Greece during two consecutive vintages and analyzed using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QToF-MS). A targeted metabolomics methodology was developed, including the determination and quantification of 28 phenolic compounds from different classes (hydroxycinnamic acids, hydroxybenzoic acids, stilbenes and flavonoids). Moreover, 86 compounds were detected and tentatively identified via a robust suspect screening workflow using an in-house database of 420 wine related compounds. Supervised chemometric techniques were employed to build an accurate and robust model to discriminate between two varieties. 相似文献
8.
9.
We propose an adaptive way to improve noise reduction by local geometric projection. From the neighborhood of each candidate point in phase space, we identify the best subspace that the point will be orthogonally projected to. The signal subspace is formed by the most significant eigendirections of the neighborhood, while the less significant ones define the noise subspace. We provide a simple criterion to separate the most significant eigendirections from the less significant ones. This criterion is based on the maximum logarithmic difference between the neighborhood eigendirection lengths, and the assumption that there is at least one eigendirection that corresponds to the noise subspace. In this way, we take into account the special characteristics of each neighborhood and introduce a more successful noise reduction technique. Results are presented for a chaotic time series of the Henon map and Ikeda map, as well as on the Nasdaq Composite index. 相似文献
10.
Preparation of hydroxyapatite via microemulsion route 总被引:7,自引:0,他引:7
Koumoulidis GC Katsoulidis AP Ladavos AK Pomonis PJ Trapalis CC Sdoukos AT Vaimakis TC 《Journal of colloid and interface science》2003,259(2):254-260
Hydroxyapatite (HAp) was prepared using a microemulsion route in combination with the pH-shock wave method. The samples as received consisted of amorphous aggregated particles, which had remarkable mesoporosity with a narrow pore size distribution. After being heated at 650 degrees C, the A-type carbonate hydroxyapatite was crystallized at 635 degrees C in particles of similar size (40--120 nm) with no internal porosity. At a higher temperature (900 degrees C) a sintering process took place, resulting in network of a larger particles, consisting of HAp and beta-tricalcium phosphate (beta-TCP). The crystallization of HAp occurs at 635 degrees C with an activation energy of 62.7--72.2 kcalmol(-1). 相似文献