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排序方式: 共有103条查询结果,搜索用时 15 毫秒
11.
Ezhil Jothinathan Kim VanmeenselJef Vleugels Tamara KharlamovaVladislav Sadykov Svetlana PavlovaGeorgia Sourkouni Christian SzepanskiChristos Argirusis Omer Van der Biest 《Solid State Ionics》2011,192(1):419-423
Apatite type rare earth silicates are being extensively studied as electrolyte material for intermediate temperature solid oxide fuel cells (SOFC). In this paper we presents results on synthesis of Al and/or Fe-doped ATLS, the design of compatible anode materials, thermal expansion properties and co-sintering of half-cells from expansion matched materials using the advanced pulsed electric current sintering (PECS) technique. The issues related to the co-sintering of half cells have been addressed successfully by the combined use of nano powders and PECS. 相似文献
12.
Paradise CL Sarkar PR Razzak M De Brabander JK 《Organic & biomolecular chemistry》2011,9(11):4017-4020
Amino acid-derived propargylic amides are cyclised in a one-pot, Au(III)-catalysed operation to yield 5-bromomethyl oxazoles. These compounds are further elaborated to bis-heterocycles, dipeptide mimics and more. 相似文献
13.
Simon Backx Andreas Dejaegere Andreas Simoens Jef Van de Poel Dr. Dorota Krasowska Prof. Dr. Christian V. Stevens Prof. Dr. Sven Mangelinckx 《European journal of organic chemistry》2023,26(26):e202300172
Organophosphorus compounds such as phosphonamidates are gaining attention across different fields of chemistry, with interesting applications as pharmaceuticals, or pesticides. However, practical application of phosphonamidates is complicated by their difficult syntheses which often involve expensive or unstraightforward reagents and harsh conditions. To remedy these issues, we present a flexible, room temperature synthesis for novel P-alkylphosphonamidates without the need for intermediary purification. Commonly available phosphonates are first chlorinated by use of oxalyl chloride and phosphonylaminium salts are used to mediate the harsh reactivity of phosphonochloridates, giving rise to the desired products. We demonstrate the compatibility of our protocol with primary and secondary amines, as well as with different phosphonate esters. The proposed pathway also enables the synthesis of primary phosphonamidates using ammonium acetate as a cheap and safe alternative for ammonia. In future research, this protocol will also enable the synthesis of bioactive targets that are incompatible with current protocols. 相似文献
14.
B. Aronov M. de Berg A. F. van der Stappen P. Švestka and J. Vleugels 《Discrete and Computational Geometry》1999,22(4):505-525
We study the motion-planning problem for pairs and triples of robots operating in a shared workspace containing n obstacles. A standard way to solve such problems is to view the collection of robots as one composite robot, whose number
of degrees of freedom is d , the sum of the numbers of degrees of freedom of the individual robots. We show that it is sufficient to consider a constant
number of robot systems whose number of degrees of freedom is at most d-1 for pairs of robots, and d-2 for triples. (The result for a pair assumes that the sum of the number of degrees of freedom of the robots constituting
the pair reduces by at least one if the robots are required to stay in contact; for triples a similar assumption is made.
Moreover, for triples we need to assume that a solution with positive clearance exists.)
We use this to obtain an O(n
d
) time algorithm to solve the motion-planning problem for a pair of robots; this is one order of magnitude faster than what
the standard method would give. For a triple of robots the running time becomes O(n
d-1
) , which is two orders of magnitude faster than the standard method. We also apply our method to the case of a collection
of bounded-reach robots moving in a low-density environment. Here the running time of our algorithm becomes O(n log n) both for pairs and triples.
Received August 10, 1998, and in revised form February 17, 1999. 相似文献
15.
Sinkeldam RW Hoeben FJ Pouderoijen MJ De Cat I Zhang J Furukawa S De Feyter S Vekemans JA Meijer EW 《Journal of the American Chemical Society》2006,128(50):16113-16121
The ability of foldamers to adopt a secondary structure in solution has been exploited to organize peripheral functionality. Our previously reported poly(ureidophthalimide) foldamer proved to be an excellent scaffold for the chiral organization of peripherally positioned oligo(p-phenylenevinylene) (OPV) chromophores. Facile high-yielding synthesis gave access to the required OPV-decorated building blocks. A condensation polymerization provided polymers of sufficient length to allow construction of a helical architecture comprising several turns. Short and long chains were separated by chromatography. Circular dichroism studies in THF of the longer chains indicate the presence of helically arranged OPVs. However, such an effect is not observed in CHCl3. Remarkable are the measurements of the OPV foldamers in heptane. A bisignate Cotton effect is observed in heptane of a sample with a THF history. No Cotton effect is observed in heptane of a sample with a CHCl3 history. In this example of supramolecular synthesis, the solvent dictates the expression of supramolecular chirality in a secondary structure. The short-chain oligomeric fractions that are unable to create a full turn revealed on scanning tunneling microscopy analysis the presence of circular architectures at the graphite/1-phenyloctane interface. This is in full agreement with the proposed conformation of the decorated foldamers. 相似文献
16.
分别以TiH2,ZrH2为原料,结合原位反应与脉冲电流辅助烧结制备了TiB2-SiC及ZrB2-SiC复相陶瓷.研究发现,所制备的复相陶瓷表现出一定的织构化现象,TiB2及ZrB2晶粒在反应烧结过程中其(001)面沿垂直压力和电流方向生长.金属氢化物粉体的粒径大小对复相陶瓷的致密化及微结构有较大影响:粒径越小越有利于陶瓷的致密化和硼化物晶粒的定向生长.由于金属硼化物的定向,复相陶瓷的机械性能表现出各向异性.TiB2-SiC复相陶瓷具有较高的断裂韧性,最高可达7.3 MPa·m1/2,而ZrB2-SiC复相陶瓷具有更高的抗弯强度(937 MPa). 相似文献
17.
Huys R Braeken D Jans D Stassen A Collaert N Wouters J Loo J Severi S Vleugels F Callewaert G Verstreken K Bartic C Eberle W 《Lab on a chip》2012,12(7):1274-1280
To cope with the growing needs in research towards the understanding of cellular function and network dynamics, advanced micro-electrode arrays (MEAs) based on integrated complementary metal oxide semiconductor (CMOS) circuits have been increasingly reported. Although such arrays contain a large number of sensors for recording and/or stimulation, the size of the electrodes on these chips are often larger than a typical mammalian cell. Therefore, true single-cell recording and stimulation remains challenging. Single-cell resolution can be obtained by decreasing the size of the electrodes, which inherently increases the characteristic impedance and noise. Here, we present an array of 16,384 active sensors monolithically integrated on chip, realized in 0.18 μm CMOS technology for recording and stimulation of individual cells. Successful recording of electrical activity of cardiac cells with the chip, validated with intracellular whole-cell patch clamp recordings are presented, illustrating single-cell readout capability. Further, by applying a single-electrode stimulation protocol, we could pace individual cardiac cells, demonstrating single-cell addressability. This novel electrode array could help pave the way towards solving complex interactions of mammalian cellular networks. 相似文献
18.
Van Rossom W Caers J Robeyns K Van Meervelt L Maes W Dehaen W 《The Journal of organic chemistry》2012,77(6):2791-2797
In pursuit of highly preorganized macrocyclic host molecules for the complexation of anions, a series of oxacalix[2]arene[2]pyrimidine-based bis(thio)ureido receptors were synthesized and fully characterized. The pincer-like 1,3-alternate conformation of the oxacalix[4]arene scaffold, essential for an efficient host-guest interaction, was visualized by single-crystal X-ray analysis and supported by variable-temperature NMR studies. The anion binding properties of the receptors were evaluated via (1)H NMR titration experiments, showing intermolecular interactions with H(2)PO(4)(-), AcO(-), BzO(-), and Cl(-) ions. The host molecule bearing 4-nitrophenyl substituents on the bisurea binding pocket showed association constants in the range of 200-400 M(-1) in the strongly competitive solvent mixture of DMSO/0.5% H(2)O. 相似文献
19.
Bart Vermang Emanuele Cornagliotti Victor Prajapati Joachim John Jef Poortmans Robert Mertens 《固体物理学:研究快报》2012,6(6):259-261
This Letter discusses an important difference between positively charged SiO2 and negatively charged Al2O3 rear‐passivated p‐type Si solar cells: their illumination level dependency. For positively charged SiO2 rear‐passivated p‐type Si solar cells, a loss in short circuit current (JSC) and open circuit voltage (VOC) as a function of illumination level is mainly caused by parasitic shunting and a decrease in surface recombination, respectively. Hence, the relative loss in cell conversion efficiency, JSC, and VOC as a function of the illumination level for SiO2 compared to Al2O3 rear‐passivated p‐type Si solar cells has been measured and discussed. Subsequently, an exponential decay fit of the loss in cell efficiency is applied in order to estimate the difference in the energy output for both cell types in three different territories: Belgium (EU), Seattle and Austin (US). The observed trends in the difference in energy output between both cells, as a function of time of the year and region, are as expected and discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Irina Cotiuga Francesco Picchioni Uday S. Agarwal Bastiaan B. P. Staal Jef A. J. M. Vekemans Piet J. Lemstra 《Macromolecular rapid communications》2006,27(4):242-246
Summary: We report the synthesis of well‐defined block copolymers by covalent coupling of hydroxy end‐functionalized polymers. Using the high volatility of the coupling agent phosgene as compared to the solvent, very high conversion (up to 96%) is obtained in a one‐pot reaction with as little as 10−5 moles of each of the reacting polymers, even without prior purification of the as‐received reagents. This has potential as an alternative to the currently practiced method of sequential living polymerization of constituent monomers, with the added advantage of direct knowledge and control over the length distribution of each block.