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151.
Jessie Lorenzo Chao Ilja Grebenchtchikov Robert Kieffer Zinaida Vakhovskaya Ute Baumeister Carsten Tschierske 《Liquid crystals》2013,40(10):1095-1102
In single‐, double‐, and triple‐chain amphiphilic diols the CONH group was replaced by CON(CH3) in order to reduce the number of proton donor groups available for intermolecular hydrogen bonding. The resulting three new liquid crystalline diols were studied by DSC, X‐ray and dielectric measurements, and show the mesophases SmA, ColH2 or CubI2, depending on the number of decyloxy groups in the hydrophobic part of the molecule. The process of self‐assembly to different liquid crystalline phases is well seen in the dielectric spectrum and details of this process are discussed together with results from the X‐ray measurements. All the compounds show a high frequency dielectric absorption caused by the dynamics of the network of hydrogen bonds. An additional low frequency process related to the internal dynamics of the columns is seen only in the columnar phase. 相似文献
152.
Dr. Tristan Mes Dr. Seda Cantekin Dirk W. R. Balkenende Martijn M. M. Frissen Martijn A. J. Gillissen Bas F. M. De Waal Dr. Ilja K. Voets Prof. Dr. E. W. Meijer Dr. Anja R. A. Palmans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8642-8649
The amide bond is a versatile functional group and its directional hydrogen‐bonding capabilities are widely applied in, for example, supramolecular chemistry. The potential of the thioamide bond, in contrast, is virtually unexplored as a structuring moiety in hydrogen‐bonding‐based self‐assembling systems. We report herein the synthesis and characterisation of a new self‐assembling motif comprising thioamides to induce directional hydrogen bonding. N,N′,N′′‐Trialkylbenzene‐1,3,5‐tris(carbothioamide)s (thioBTAs) with either achiral or chiral side‐chains have been readily obtained by treating their amide‐based precursors with P2S5. The thioBTAs showed thermotropic liquid crystalline behaviour and a columnar mesophase was assigned. IR spectroscopy revealed that strong, three‐fold, intermolecular hydrogen‐bonding interactions stabilise the columnar structures. In apolar alkane solutions, thioBTAs self‐assemble into one‐dimensional, helical supramolecular polymers stabilised by three‐fold hydrogen bonding. Concentration‐ and temperature‐dependent self‐assembly studies performed by using a combination of UV and CD spectroscopy demonstrated a cooperative supramolecular polymerisation mechanism and a strong amplification of supramolecular chirality. The high dipole moment of the thioamide bond in combination with the anisotropic shape of the resulting cylindrical aggregate gives rise to sufficiently strong depolarised light scattering to enable depolarised dynamic light scattering (DDLS) experiments in dilute alkane solution. The rotational and translational diffusion coefficients, Dtrans and Drot, were obtained from the DDLS measurements, and the average length, L, and diameter, d, of the thioBTA aggregates were derived (L=490 nm and d=3.6 nm). These measured values are in good agreement with the value Lw=755 nm obtained from fitting the temperature‐dependent CD data by using a recently developed equilibrium model. This experimental verification validates our common practice for determining the length of BTA‐based supramolecular polymers from model fits to experimental CD data. The ability of thioamides to induce cooperative supramolecular polymerisation makes them effective and broadly applicable in supramolecular chemistry. 相似文献
153.
154.
Alexander Horn Ilja Mingareev Alexander Werth Martin Kachel Udo Brenk 《Applied Physics A: Materials Science & Processing》2008,93(1):171-175
Using ultrafast laser radiation glass substrates are welded with glass and silicon plates. The pump beam is focused by a microscope
objective with large NA=0.4 (beam diameter 4 μm) into the glass. After partial absorption of the optical energy, the glass
is heated and melted. Procedures for high-quality welding of glass–glass and glass–silicon substrates with high-repetition
ultra-fast laser radiation have been derived at the repetition rate 700 kHz. The dependencies of the dimension and geometry
of the welding seam on scan velocity, repetition rate and pulse energy have been investigated defining a process window. Adding
a noninterferometric technique for quantitative phase detection with the welding setup, the interaction zone of the welding
seam for the welding partners glass–glass is detected. A change in refractive index is induced by heating and compression
of the glass and has been detected by phase detection up to 2 μs after irradiation with 100 fs time resolution. 相似文献
155.
Mixed-Valence CuI/CuIII Metal–Organic Frameworks with Non-innocent Ligand for Multielectron Transfer
Shang-Yuan Fu Cheng-Han Chang Dr. Alexander S. Ivanov Dr. Ilja Popovs Dr. Jeng-Lung Chen Dr. Yen-Fa Liao Dr. Hsin-Kuan Liu Dr. Suman Chirra Prof. Dr. Yun-Wei Chiang Jui-Chin Lee Wei-Ling Liu Prof. Dr. Watchareeya Kaveevivitchai Prof. Dr. Teng-Hao Chen 《Angewandte Chemie (International ed. in English)》2023,62(50):e202312494
We report two novel three-dimensional copper-benzoquinoid metal–organic frameworks (MOFs), [Cu4L3]n and [Cu4L3 ⋅ Cu(iq)3]n (LH4=1,4-dicyano-2,3,5,6-tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed-valence metal and redox-non-innocent ligand L, which promotes through-bond charge transfer between Cu metal sites, allows better metal-ligand orbital overlap of the d-π conjugation, leading to strong long-range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly-covalent Cu(III), non-innocent ligand, and pore environments of these bench stable Cu(III)-containing frameworks on multielectron transfer and electrochemical properties. 相似文献
156.
Jonas F. Goebel Julian Löffler Zhongyi Zeng Jens Handelmann Albert Hermann Ilja Rodstein Dr. Tobias Gensch Prof. Dr. Viktoria H. Gessner Prof. Dr. Lukas J. Gooßen 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216160
Palladium-catalyzed couplings of silicon enolates with aryl electrophiles are of great synthetic utility, but often limited to expensive bromide substrates. A comparative experimental study confirmed that none of the established ligand systems allows to couple inexpensive aryl chlorides with α-trimethylsilyl alkylnitriles. In contrast, ylide functionalized phosphines (YPhos) led to encouraging results. A statistical model was developed that correlates the reaction yields with ligand features. It was employed to predict catalyst structures with superior performance. With this cheminformatics approach, YPhos ligands were tailored specifically to the demands of Hiyama couplings. The newly synthesized ligands displayed record-setting activities, enabling the elusive coupling of aryl chlorides with α-trimethylsilyl alkyl nitriles. The preparative utility of the catalyst system was demonstrated by the synthesis of pharmaceutically meaningful α-aryl alkylnitriles, α-arylcarbonyls and biaryls. 相似文献