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991.
Mark W. Simon Jeffrey R. Rozak Steven L. Suib Jeffrey Harrison Mahmoud Kablauoi 《Research on Chemical Intermediates》2000,26(6):529-548
Pure hydrocarbon plasmas have been generated at low pressures with good efficiency using methane as a reactant. Hydrocarbon
plasma discharges containing high energy, free radical, and ionized intermediates were analyzed in situ using emission spectroscopy. Emission spectra were correlated with analytical data obtained from resultant product mixtures
and literature assignments of emission bands in order to identify these intermediates. Stabilization of atmospheric methane
plasmas using argon as a diluent has also been demonstrated in this study. Emission spectroscopy has also been used to identify
reaction intermediates formed in plasmas at high pressures. Distinct differences in plasma discharges have been observed as
a function of pressure, power, and methane concentrations at the molecular level using in situ spectroscopic techniques. 相似文献
992.
Jeffrey C. Bryan Tatiana G. Levitskaia 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(12):1457-1459
The title compound, C32H32O8·3C2H4Cl2, illustrates how tetrabenzo-24-crown-8 may be solvated by a common solvent-extraction diluent, 1,2-dichloroethane (DCE). Two molecules of DCE occupy the crown cavity, forming weak hydrogen bonds to the ether O atoms and the crown arene rings, while the crown adopts its most commonly observed binding conformation. The asymmetric unit is composed of two molecules of tetrabenzo-24-crown-8 and six molecules of DCE. 相似文献
993.
Arthur Maki Thomas A. Blake Robert L. Sams Nicolae Vulpanovici Jeffrey Barber Engelene T.H. Chrysostom Tony Masiello Joseph W. Nibler Alfons Weber 《Journal of Molecular Spectroscopy》2001,210(2)
New measurements are reported for the infrared spectrum of sulfur trioxide, 32S16O3, with resolutions ranging from 0.0015 cm−1 to 0.0025 cm−1. Rovibrational constants have been measured for the fundamentals ν2, ν3, and ν4 and the overtone band 2ν3. Comparisons are made with the earlier high-resolution measurements on SO3, and the high correlation among some of the constants related to the Coriolis coupling of the ν2 and ν4 levels is discussed in order to understand the areas of disagreement with the earlier work. Splittings of some of the levels are observed and the splitting constant for K=3 of the ground state is determined for the first time. Other observed splittings include the K=1 levels of 2ν3 (l=2), the K=2 levels of ν3 and ν4, and the K=3 levels of ν2. The analysis shows that there are level crossings between the l=0 and l=2 states of 2ν3 that allow one to determine the separation of the subband centers for these two states even though access to the l=0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q3, that causes the splitting of the l3=±1, k=±1 levels of ν3 also couples the l3=0 and 2 states of 2ν3. 相似文献
994.
Ian T. Foster Jeffrey L. Tilson Albert F. Wagner Ron L. Shepard Robert J. Harrison Rick A. Kendall Rik J. Littlefield 《Journal of computational chemistry》1996,17(1):109-123
Several parallel algorithms for Fock matrix construction are described. The algorithms calculate only the unique integrals, distribute the Fock and density matrices over the processors of a massively parallel computer, use blocking techniques to construct the distributed data structures, and use clustering techniques on each processor to maximize data reuse. Algorithms based on both square and row-blocked distributions of the Fock and density matrices are described and evaluated. Variants of the algorithms are discussed that use either triple-sort or canonical ordering of integrals, and dynamic or static task clustering schemes. The algorithms are shown to adapt to screening, with communication volume scaling down with computation costs. Modeling techniques are used to characterize algorithm performance. Given the characteristics of existing massively parallel computers, all the algorithms are shown to be highly efficient for problems of moderate size. The algorithms using the row-blocked data distribution are the most efficient. © 1996 by John Wiley & Sons, Inc. 相似文献
995.
This paper studies the focusing of high-frequency solutions of semilinear hyperbolic equations. In previous papers, we studied two opposite phenomena. First, the focusing of nonlinear waves can force the solutions to blow up, even before reaching the caustics. Second, for strongly dissipative equations, nonlinear oscillations can be completely absorbed when they reach the caustic set. In this paper, we study the intermediate case of equations with globally Lipschitz nonlinearities. The nonlinear oscillations persist after crossing the caustic set. The solutions are described using oscillatory integrals, which are associated with Lagrangian manifolds in the cotangent bundle. The equations of nonlinear geometric optics lift to these manifolds. In contrast to the linear case, the transport equations for amplitudes living above the same points of spacetime are coupled. © 1996 John Wiley & Sons, Inc. 相似文献
996.
Lee J. Silverberg Carlos Pacheco Debashish Sahu Peter Scholl Hany F. Sobhi Joshua T. Bachert Kaitlyn Bandholz Ryan V. Bendinsky Heather G. Bradley Baylee K. Colburn David J. Coyle Jonathon R. Dahl Megan Felty Ryan F. Fox Kyanna M. Gonzalez Jasra M. Islam Stacy E. Koperna Quentin J. Moyer Duncan J. Noble Melissa E. Ramirez Ziwei Yang 《Journal of heterocyclic chemistry》2020,57(4):1797-1805
A series of 11 novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-aryl-C-phenyl imines with thiosalicylic acid. This provides simple and ready access to N-aryl compounds in this family, which have been generally difficult to prepare. 相似文献
997.
Journal of Fourier Analysis and Applications - Analogues of Slepian vectors are defined for finite-dimensional Boolean hypercubes. These vectors are the most concentrated in neighborhoods of the... 相似文献
998.
Cheryl L. Eames Jeffrey E. Barrett Craig J. Cullen George Rutherford David Klanderman Douglas H. Clements Julie Sarama Douglas W. Van Dine 《School science and mathematics》2020,120(2):67-78
This study explored children’s area estimation performance. Two groups of fourth grade children completed area estimation tasks with rectangles ranging from 5 to 200 square units. A randomly assigned treatment group completed instructional sessions that involved a conceptual area measurement strategy along with numerical feedback. Children tended to underestimate areas of rectangles. Furthermore, rectangle size was related to performance such that estimation error and variability increased as rectangle size increased. The treatment group exhibited significantly improved area estimation performance in terms of accuracy, as well as reduced variability and instances of extreme responses. Area measurement estimation findings are related to a Hypothetical Learning Trajectory for area measurement. 相似文献
999.
Mélodie Ferrat Dr. Kenneth Dahl Dr. Magnus Schou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(34):8689-8693
Electrophilic 11C-labelled aroyl dimethylaminopyridinium salts, obtained by carbonylative cross-coupling of aryl halides with [11C]carbon monoxide, were prepared for the first time and shown to be valuable intermediates in the synthesis of primary [11C]benzamides. The methodology furnished a set of benzamide model compounds, including the two poly (ADP-ribose) polymerase (PARP) inhibitors niraparib and veliparib, in moderate to excellent radiochemical yields. In addition to providing a convenient and practical route to primary [11C]benzamides, the current method paves the way for future application of [11C]aroyl dimethylaminopyridinium halide salts in positron emission tomography (PET) tracer synthesis. 相似文献
1000.
Moritz K. Jackl Christopher P. Gordon Christophe Copéret Jeffrey W. Bode 《Helvetica chimica acta》2020,103(12):e2000179
A method for the synthesis of rigid nitroxide biradicals with various spatial orientations between the radical centers is reported. Diketones were employed as substrates for tin amine protocol (SnAP) reagents to provide the parent spirocyclic diamines. Oxidation by peroxyacids provided the corresponding nitroxide biradicals. A set of four different biradicals with various interelectron distances and torsion angles between the radical planes was synthesized using this method. The exact geometries were determined by X-ray crystallography and the biradicals were investigated by EPR spectroscopy and evaluated for their dynamic nuclear polarization (DNP) performance. 1H-DNP enhancements in the range of 1.2–2.1 at 14.1 Tesla (600 MHz spectrometer) were achieved. This synthetic methodology opens a promising alternative to access nitroxide biradicals with various torsional angles and inter radical distances. 相似文献