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101.
102.
Peter Heiling Helmut Hönig Klaus Hummel 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):575-579
Empirical force field calculations are used to interpret the occurrence of cyclopentenyl compounds in the course of metathesis degradation of partially isomerized modified poly(1-butenylenes). 相似文献
103.
Wolfgang Hummel 《Monatshefte für Chemie / Chemical Monthly》2008,35(3):459-480
Equilibrium thermodynamics is one of the pillars which support safety analyses of repositories for radioactive waste. The
research summarized in this review deals with approaches to resolve the problems related to thermodynamic equilibrium constants
and solubility of solid phases in the field of radioactive waste management. The results have been obtained at the Paul Scherrer Institut between 1995 and 2005 and comprise the scientific basis of the author’s habilitation thesis in the field of nuclear
environmental chemistry. The topics are grouped according to three different levels of problem solving strategies: (1) Critical
and comprehensive reviews of the available literature, which are necessary in order to establish a reliable chemical thermodynamic
database that fulfils the requirements for rigorous modeling of the behavior of the actinides and fission products in the
environment. (2) In many case studies involving inorganic and simple organic ligands a serious lack of reliable thermodynamic
data is encountered. There, a new modeling approach to estimate the effects of these missing data was applied. This so called
“backdoor approach” begins with the question, “What total concentration of a ligand is necessary to significantly influence
the speciation, and hence the solubility, of a given trace metal?” (3) In the field of natural organics, mainly humic and
fulvic acids, we face an ill-defined problem concerning the molecular structure of the ligands. There, a pragmatic approach
for performance assessment purposes was applied, the “conservative roof” approach, which does not aim to accurately model
all experimental data, but allows estimates of maximum effects on metal complexation by humic substances to be calculated. 相似文献
104.
105.
Felix Hummel Thomas Gruber Andreas Grüneis 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(11):235
In this article we explore methods to reduce the computational cost in many-electron wave function expansions including explicit correlation and compact one-electron basis sets for the virtual orbitals. These methods are applied to the calculation of the interlayer binding energy of the h-BN bilayer system. We summarize the optimized interlayer distances as well as their binding energies for various stacking faults on different levels of theory including second-order Møller-Plesset perturbation theory and the random phase approximation. Furthermore, we investigate the asymptotic behavior of the binding energy at large interlayer separation and find that it decays as D-4 in agreement with theoretical predictions, where D is the interlayer distance. 相似文献
106.
Jeffrey A. Boerth Joshua R. Hummel Prof. Dr. Jonathan A. Ellman 《Angewandte Chemie (International ed. in English)》2016,55(41):12650-12654
A highly stereoselective three‐component C(sp2)?H bond addition across alkene and polarized π‐bonds is reported for which CoIII catalysis was shown to be much more effective than RhIII. The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp2)?H bonds undergo the three‐component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five‐membered lactones. Additionally, the first asymmetric reactions with CoIII‐catalyzed C?H functionalization are demonstrated with three‐component C?H bond addition cascades employing N‐tert‐butanesulfinyl imines. These examples represent the first transition metal catalyzed C?H bond additions to N‐tert‐butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines. 相似文献
107.
Thomas Geiger Simon Schundelmeier Thorsten Hummel Dr. Markus Ströbele Dr. Wolfgang Leis Prof. Dr. Michael Seitz Clemens Zeiser Luca Moretti Dr. Margherita Maiuri Prof. Dr. Giulio Cerullo Jun.-Prof. Dr. Katharina Broch Jörn Vahland Prof. Dr. Karl Leo Dr. Cäcilia Maichle-Mössmer Prof. Dr. Bernd Speiser Prof. Dr. Holger F. Bettinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3420-3434
The properties as well as solid-state structures, singlet fission, and organic field-effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10 , 1,4,9,10: 11 , 2,3,9,10: 12 ) are compared herein. The novel compounds 10 and 11 were synthesized in high purity from the corresponding 6,13-etheno-bridged precursors by reaction with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer 10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers π–π stacking. Although the energy of the first electric dipole-allowed optical transition varies only within 370 cm−1 (0.05 eV) for the neutral compounds, this amounts to roughly 1600 cm−1 (0.20 eV) for radical cations and 1300 cm−1 (0.16 eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet-fission time constants (91±11, 73±3 fs, respectively) that are shorter than for pentacene (112±9 fs). OFET devices constructed from 11 and 12 show close to ideal thin-film transistor (TFT) characteristics with electron mobilities of 2×10−3 and 6×10−2 cm2 V−1 s−1, respectively. 相似文献
108.
Davis FA Gaddiraju NV Theddu N Hummel JR Kondaveeti SK Zdilla MJ 《The Journal of organic chemistry》2012,77(5):2345-2359
The first examples of cocaine analogues having substituents (methyl, ethyl, n-propyl, n-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al(O(t)Bu)(3) the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]isoxazolidines was discovered. 相似文献
109.
N Fischer K Hüll TM Klapötke J Stierstorfer G Laus M Hummel C Froschauer K Wurst H Schottenberger 《Dalton transactions (Cambridge, England : 2003)》2012,41(36):11201-11211
A modification of the synthesis of sodium 5,5'-azotetrazolate pentahydrate, described by Thiele in 1898, yields the unknown and unexpected corresponding 5N-oxido derivative sodium 5,5'-azoxybistetrazolate pentahydrate (Na(2)zTO·5H(2)O, ). Purification was achieved by recrystallization based on the better solubility of Na(2)zTO·5H(2)O in water. Different nitrogen-rich salts, such as the diammonium (), the dihydroxylammonium (), the bis-diaminoguanidinium (), the bis-triaminoguanidinium () and the diaminouronium salt (), have been prepared using metathesis reactions starting from barium 5,5'-azoxybistetrazolate pentahydrate () and ammonium, hydroxylammonium, diaminoguanidinium or diaminouronium sulfate and triaminoguanidinium chloride, respectively. The nitrogen rich azoxy-derivatives were characterized using NMR, IR and Raman spectroscopy, mass spectrometry and elemental analysis. Additionally the solid state structures of , , and were determined by single crystal X-ray diffraction. The heats of formation of and and their corresponding azo-tetrazolate derivatives were calculated by the atomization method based on CBS-4M enthalpies. With these values and the crystal densities, several detonation parameters such as the detonation velocity, detonation pressure and specific impulse were calculated (EXPLO5) and compared. The sensitivities towards shock (BAM drophammer), friction (BAM friction tester) and electrostatic discharge of the described compounds were determined. 相似文献
110.