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131.
Lev Babkov Galina Puchkovskaya Ekatherina Vedyaeva 《Molecular Crystals and Liquid Crystals》2013,570(1):795-799
Abstract The structural particularities of polymorphic modifications and cholesterol liquid crystal phase have been investigated by theoretical and experimental IR spectroscopy methods. The spectra were recorded in the interval of temperatures 293–523 K within the range of 600–3600 cm?1. The frequencies of normal modes and intensities in the IR spectra have been calculated for the alkyloxybenzoate of cholesterol conformers, which may be realized under certain temperatures. Comparison of results of theoretical modelling and recorded spectra confirmed suggestion about conformational mobility basically defined with changing of steroid kennel orientation comparatively stayed part of molecule in the different phase state. 相似文献
132.
133.
B. C. Sawyer B. K. Stuhl B. L. Lev J. Ye E. R. Hudson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):197-209
The transverse motion inside a Stark decelerator plays a large role in the total efficiency of deceleration. We differentiate
between two separate regimes of molecule loss during the slowing process. The first mechanism involves distributed loss due
to coupling of transverse and longitudinal motion, while the second is a result of the rapid decrease of the molecular velocity
within the final few stages. In this work, we describe these effects and present means for overcoming them. Solutions based
on modified switching time sequences with the existing decelerator geometry lead to a large gain of stable molecules in the
intermediate velocity regime, but fail to address the loss at very low final velocities. We propose a new decelerator design,
the quadrupole-guiding decelerator, which eliminates distributed loss due to transverse/longitudinal couplings throughout
the slowing process and also exhibits gain over normal deceleration to the lowest velocities. 相似文献
134.
Jeff M. VanRaden Brittany M. White Lev N. Zakharov Ramesh Jasti 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7419-7423
The unique optoelectronic properties and smooth, rigid pores of macrocycles with radially oriented π systems render them fascinating candidates for the design of novel mechanically interlocked molecules with new properties. Two high‐yielding strategies are used to prepare nanohoop [2]rotaxanes, which owing to the π‐rich macrocycle are highly emissive. Then, metal coordination, an intrinsic property afforded by the resulting mechanical bond, can lead to molecular shuttling as well as modulate the observed fluorescence in both organic and aqueous conditions. Inspired by these findings, a self‐immolative [2]rotaxane was then designed that self‐destructs in the presence of an analyte, eliciting a strong fluorescent turn‐on response, serving as proof‐of‐concept for a new type of molecular sensing material. More broadly, this work highlights the conceptual advantages of combining compact π‐rich macrocyclic frameworks with mechanical bonds formed via active‐template syntheses. 相似文献
135.
The molecular bases of Alzheimer disease and related neurodegenerative disorders are becoming better understood, but the means for definitive diagnosis and monitoring in vivo remain lacking. Near-infrared optical spectroscopy offers a potential solution. We acquired transmission and reflectance spectra of thin brain tissue slabs, from which we calculated wavelength-dependent absorption and reduced scattering coefficients from 470-1000 nm. The reduced scattering coefficients in the near infrared clearly differentiated Alzheimer from control specimens. Diffuse reflectance spectra of gross brain tissue in vitro confirmed this observation. These results suggest a means for diagnosing and monitoring Alzheimer disease in vivo, using near-infrared optical spectroscopy. 相似文献
136.
137.
Facile Separation,Spectroscopic Identification,and Electrochemical Properties of Higher Trifluoromethylated Derivatives of [70]Fullerene
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Maria P. Kosaya Alexey V. Rybalchenko Dr. Natalia S. Lukonina Olga N. Mazaleva Dr. Ilya N. Ioffe Dr. Vitaliy Yu. Markov Prof. Dr. Sergey I. Troyanov Prof. Dr. Lev N. Sidorov Dr. Nadezhda B. Tamm Dr. Alexey A. Goryunkov 《化学:亚洲杂志》2018,13(15):1920-1931
We survey the structure and electronic properties of the family of higher trifluoromethylated C70(CF3)n molecules with n=14, 16, 18, and 20. Twenty‐two available compounds, of which thirteen are newly obtained and characterized, demonstrate the broad diversity of π‐system topologies, which enabled us to study the interplay between the CF3 addition pattern and the electronic properties. UV/Vis spectroscopic and cyclic voltammetric studies demonstrate the importance of the exact addition pattern rather than the plain number of addends. Of particular interest is the skew pentagonal pyramid (SPP) addition pattern, which enables formation of closed‐shell cyclopentadienyl anions C70(CF3)n? 1 ? through CF3 detachment upon electron transfer. A detailed study of the process is presented for a SPP‐C70(CF3)16 where potentiostatic electrolysis at the second reduction potential gives C70(CF3)15? oxidizable to a persistent C70(CF3)15· radical. Together with the literature data for the lower C70(CF3)n compounds with n=2–12, the present results show good correlation between the experimental boundary level positions and the DFT predictions. The compounds turn out to be electron acceptor molecular semiconductors with experimental LUMO energies and HOMO–LUMO gaps within the ranges of ?4.3 to ?3.7 eV and 1.6 to 3.3 eV, respectively, depending on the shape of the conjugated fragments. The HOMO levels fall within the range of ?5.6 to ?6.9 eV and show linear correlation with the number of addends. 相似文献
138.
139.
A low molecular weight hydrogel which exhibits electroosmotic flow is described, and its use for separation and biocatalytic applications that require passage of a solvent stream through the gel is demonstrated. 相似文献
140.
Pitt MA Zakharov LN Vanka K Thompson WH Laird BB Johnson DW 《Chemical communications (Cambridge, England)》2008,(33):3936-3938
A combined crystallographic, DFT and NMR spectroscopic study of a flexible As(2)(3) assembly reveals temperature dependent conformational behavior in solution and a highly asymmetric structure stabilized by As-pi and edge-to-face aromatic interactions. 相似文献