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91.
Krzysztof Brzezinski Ryszard Lazny Aneta Nodzewska Katarzyna Sidorowicz 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(3):303-306
The title compounds, C21H22BrNO2, are isomeric 8‐benzyl‐2‐[(4‐bromophenyl)(hydroxy)methyl]‐8‐azabicyclo[3.2.1]octan‐3‐ones. Compound (I), the (±)‐exo,syn‐(1RS,2SR,5SR,9SR) isomer, crystallizes in the hexagonal space group R, while compounds (II) [the (+)‐exo,anti‐(1R,2S,5S,9R) isomer] and (III) [the (±)‐exo,anti‐(1RS,2SR,5SR,9RS) isomer] crystallize in the orthorhombic space groups P212121 and Pna21, respectively. The absolute configuration was determined for enantiomerically pure (II). For the noncentrosymmetric crystal of (III), its absolute structure was established. In the crystal structures of (I) and (II), an intramolecular hydrogen bond is formed between the hydroxy group and the heterocyclic N atom. In the crystal structure of racemic (III), hydrogen‐bonded chains of molecules are formed via intermolecular O—H...O interactions. Additionally, face‐to‐edge π–π interactions are present in the crystal structures of (I) and (II). In all three structures, the piperidinone rings adopt chair conformations and the N‐benzyl substituents occupy the equatorial positions. 相似文献
92.
Piotr Przybylski Maria Mauszynska Bogumi Brzezinski 《Journal of Molecular Structure》2005,750(1-3):152-157
The Schiff base of racemic gossypol with allylamine (GSBAL) has been studied by FT-IR, 1H and 13C NMR spectroscopy as well as by the PM5 semiempirical method. The spectroscopic methods have shown that GSBAL Schiff base exists in chloroform solution as enamine–enamine tautomer. The structure of GSBAL and the hydrogen bonds within this structure have been calculated to show that the allyl groups are out-of-planes of naphthalene rings. The strongest intramolecular hydrogen bond within the structure of GSBAL is formed between O7H–N16 atoms and it belongs to the medium strong bonds. The other hydrogen bonds, although very weak, play a very important role in stabilising the GSBAL enamine–enamine structure. 相似文献
93.
94.
Grzegorz Schroeder Nataliya Lyapchenko Piotr Przybylski Bogumil Brzezinski Tomasz Kozik Agnieszka Burzynska Pawe Kafarski 《Journal of Molecular Structure》2005,750(1-3):142-151
Four N-(2-pyridyl)aminomethyldiphoshonic acids have been synthesized and the formation of the complexes between them and alkali cations were studied by the electrospray ionization mass spectrometry (ESI MS). The ESI spectra have evidenced formation of various types of complexes of the acids and monovalent cations, directly related to the formation of respective mono- and disalts of the acids. The main fragmentation path of the acids and their complexes is realized by the elimination of H2O or H3PO3 molecules. The structures of the acids and their complexes with monovalent cations have been calculated by the PM5 method. The structure and the stabilization role of the intramolecular hydrogen bonds for the complexes are discussed. 相似文献
95.
For stationary, barotropic fluids in Newtonian gravity we give simple criteria on the equation of state and the “law of motion” which guarantee finite or infinite extent of the fluid region (providing a priori estimates for the corresponding stationary Newton–Euler system). Under more restrictive conditions, we can also exclude the presence of “hollow” configurations. Our main result, which does not assume axial symmetry, uses the virial theorem as the key ingredient and generalises a known result in the static case. In the axially symmetric case stronger results are obtained and examples are discussed. 相似文献
96.
Piotr Łobacz Patryk Jasik Józef E. Sienkiewicz 《Central European Journal of Physics》2013,11(9):1107-1114
Semi-empirical adiabatic potential energy curves of highly excited states of the KRb molecule are calculated as a function of the internuclear distance R over a wide range from 3 to 150 a 0. The diatomic molecule is treated as an effective two-electron system by using the large core pseudopotentials and core polarization potentials. All calculations are performed by using the nonrelativistic CASSCF/MRCI method with accurate basis set functions. The spectroscopic constants of the calculated electronic states agree well with experimental data, including the recent ones from Lee et al., and with available theoretical results. 相似文献
97.
Piotr Ostalczyk Dariusz W. Brzezinski Piotr Duch Maciej Łaski Dominik Sankowski 《Central European Journal of Physics》2013,11(6):750-759
In this paper, the discrete differentiation order functions of the variable, fractional-order PD controller (VFOPD) are considered. In the proposed VFOPD controller, a variable, fractional-order backward difference is applied to perform closed-loop, system error, discrete-time differentiation. The controller orders functions which may be related to the controller input or output signal or an input and output signal. An example of the VFOPD controller is applied to the robot arm closed-loop control due to system changes in moment of inertia. The close-loop system step responses are presented. 相似文献
98.
Solutions of salts of the diols o-xylidenedicarbinol, o-xylidenetetraethyldicarbinol and o-xylidenetetrahexyldicarbinol were studied by IR and NMR spectroscopy. Within this series the IR continuum caused by intramolecular OH…O? ? ?O…HO bonds vanishes, a band at 1950 cm?1 being observed. Thus occurence of the continuum requires interaction of the hydrogen bonds with great proton polarizability with their solvent environments. 相似文献
99.
Przybylski P Schilf W Kamienski B Brzezinski B Bartl F 《Magnetic resonance in chemistry : MRC》2008,46(6):534-544
New Schiff bases and new hydrazones were synthesized and studied by (13)C and (15)N CP/MAS spectroscopy and by (1)H--(1)H COSY, (1)H--(13)C HMBC, (1)H--(13)C HSQC, (1)H--(15)N HMQC and (1)H--(15)N HSQC correlations. The CP/MAS investigation of gossypol has demonstrated that in the solid state it exists exclusively in the aldehyde-aldehyde tautomeric form. In contrast, CP/MAS studies of hydrazones and Schiff bases reveal that these compounds occur in the solid state in the N-imine-N-imine and enamine-enamine tautomeric forms, respectively. It is shown that the (13)C resonances of C-6, C-7 and C-11 carbon atoms are suitable for distinguishing between the tautomeric forms of aza-derivatives of gossypol in the solid state. Furthermore, we have proved that the (15)N CP/MAS spectra can be used to identify these tautomeric forms. 相似文献
100.
Piotr Przybylski Krystian Pyta Małgorzata Ratajczak-Sitarz Andrzej Katrusiak Bogumił Brzezinski 《Structural chemistry》2008,19(6):983-995
Crystals of the Schiff base derivative of gossypol with allylamine (GSBAL) were grown and subsequently examined by X-ray diffraction and FT-IR methods. The crystal space group is C2/c with a = 16.057(1) Å, b = 14.112(1) Å, c = 27.185(2) Å, β = 99.371(5)? and Z = 8. In the crystal, GSBAL exists in the enamine–enamine tautomeric form. The FT-IR spectral features of the crystals are in agreement with the X-ray data indicating that both parts of the molecule are similarly intramolecular hydrogen-bonded but different intermolecular hydrogen-bonded, although the molecule is symmetrically substituted. On the basis of the electrospray ionization mass spectrometry (ESI MS) experiments, it has been shown for the first time that Schiff base of gossypol forms complexes with the perchlorate anion and metal cations simultaneously. The ESI MS spectra of the 1:1:1 mixtures of GSBAL:GOS:M+, in the positive and negative ion detection mode, have indicated the preferential formation of the 1:1 complexes of GSBAL with M+ (Li, Na or K) and ClO4 ? over the respective complexes forming between GOS and the metal cation or the anion. The PM5 semiempirical calculations have allowed visualization of the most energetically favourable structures of these two types of GSBAL complexes. 相似文献