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71.
John J. Orlando Geoffrey S. Tyndall Eric C. Apel Daniel D. Riemer Suzanne E. Paulson 《国际化学动力学杂志》2003,35(8):334-353
Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10?10cm3 molecule?1 s?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10?10 cm3 molecule?1 s?1; k( MACR ) = (2.4 ± 0.3) × 10?10 cm3 molecule?1 s?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10?10 cm3 molecule?1 s?1; k(1‐butene) = (3.0 ± 0.4) × 10?10 cm3 molecule?1 s?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH2O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO2 (58 ± 5%), CH2O (47 ± 7%), CH3OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO2 (23 ± 2%), CH2O (18 ± 2%), and HCOCl (5%) from MACR ; CH2O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH3CHO (22 ± 3%), CO2 (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH2O (7.6 ± 1.1%), and CH3OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH2O (7 ± 1%), CO2 (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O2‐dependent. In the case of trans‐2‐butene, the observed O2‐dependence is the result of a competition between unimolecular decomposition of the CH3CH(Cl)? CH(O?)? CH3 radical and its reaction with O2, with kdecomp/kO2 = (1.6 ± 0.4) × 1019 molecule cm?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol?1. The variation of the product yields with O2 in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH2CH(O?)CH2CH3 and ?OCH2CHClCH2CH3. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003 相似文献
72.
F. Morales G. Castiglia P. P. Corso R. Daniele E. Fiordilino F. Persico G. Orlando 《Laser Physics》2008,18(5):592-597
The dynamics of hydrogen-like molecules is investigated beyond the usual fixed nuclei approximation. The nuclear motion introduces in the familiar spectrum of emitted radiation additional regular lines whose separation is essentially given by the vibrational frequency of nuclear motion. A wavelet analysis of the emitted spectrum shows that the intensity of the harmonic lines is modulated with the same period of the nuclear motion; this suggests the possibility of the real-time control of the nuclear dynamics. 相似文献
73.
A. R. W. McKellar James B. Burkholder John J. Orlando Carleton J. Howard 《Journal of Molecular Spectroscopy》1988,130(2)
The ν3 fundamental band of the formyl radical, HCO, in the 5.3-μm region has been observed at high resolution (0.0025 cm−1, unapodized) using a Fourier transform spectrometer. The HCO radicals were formed by the reaction of F atoms with H2CO in a fast-flow multiple-traversal absorption cell. A total of 298 lines were measured with an accuracy of about 0.0004 cm−1 and assigned to transitions with values of the rotational quantum numbers N and Ka up to 20 and 5, respectively. These data greatly improve the knowledge of the HCO ν3 line positions and (v1v2v3) = (001) vibrational state molecular parameters as compared to earlier laser magnetic resonance studies of this band, especially for higher values of N. The ν1 fundamental band of HCO was also observed and an analysis of these data agrees well with the recent study of Dane et al. [J. Chem. Phys. 88, 2121–2128 (1988)]. 相似文献
74.
The rate of electron-positron pair production in a weak external electric field at large values of e is computed. The method is extended to compute the rate of monopole-antimonopole pair production in a weak external magnetic field at large magnetic charge. 相似文献
75.
We have studied the interaction of low-energy (5–50 eV) electrons with nanoscale (10 ML) ice films by probing the yields and quantum-state distributions of the neutral dissociation products using laser resonance-enhanced multiphoton ionization spectroscopy. In particular, we have observed the electron-stimulated desorption (ESD) of D (2S), O (3P2) and O (1D2) from amorphous D2O films. These products are observed at threshold energies (relative to the vacuum level) between 6.5–7 eV and desorb with low kinetic energies (60–85 meV) which are independent of the incident electron energy. We associate the ESD of atomic fragments from ice with dissociation of Frenkel-type excitons of 4a1 character which are near the bottom of the ice conduction band. These excitons are created either directly or via electron-ion recombination. Changing the surface temperature from 88 to 145 K results in an increase in the thermal component of the time-of-flight (kinetic energy) distributions and an overall increase in the neutral fragment yield. We suggest that the change in neutral yield with substrate temperature results from a combination of: (1) increased electron-ion recombination; (2) exciton transport to the near-surface region; and (3) dissociation followed by inelastic scattering and desorption. 相似文献
76.
Orlando Alvarez I. M. Singer Bruno Zumino 《Communications in Mathematical Physics》1984,96(3):409-417
We discuss the use of the family's index theorem in the study of gravitational anomalies. The geometrical framework required to apply the family's index theorem is presented and the relation to gravitational anomalies is discussed. We show how physics necessitates the introduction of the notion oflocal cohomology which is distinct from the ordinary topological cohomology. The recent results of Alvarez-Gaumé and Witten are derived by using the family's index theorem.This work was supported in part by the National Science Foundation under Contracts PHY81-18547 and MCS80-23356; and by the Director, Office of High Energy and Nuclear Physics of the US Department of Energy under Contracts DE-AC03-76SF00098 and AT0380-ER10617Alfred P. Sloan Foundation Fellow 相似文献
77.
The low-energy spectrum of 1+ and 0? mesons in one-flavour QCS is investigated. It is shown that there exist two light pseudoscalar mesons, which are linear combinations of pure quark and pure glueball states. Simple relations implied by the axial anomaly for their decay constants are confirmed. The mass generation mechanism for the lightest pseudoscalar meson is identified as due to the mixing of the operators and , and the U(1) problem in this model is resolved. To establish these results, new functional methods are developed to determine the effective action for the appropriate fields in a low-energy approximation. A novel feature of our work is the introduction of a “symmetric” effective action, defined using a non-standard Legendre transform. The anomalous chiral Ward identities imply a simple invariance property for this functional, enabling it to be constructed in a particularly systematic way. Finally, the relation of our general results to the literature on effective lagrangians in the approximation is discussed. 相似文献
78.
Simple modification of a protein database for mass spectral identification of N-linked glycopeptides
Atwood JA Sahoo SS Alvarez-Manilla G Weatherly DB Kolli K Orlando R York WS 《Rapid communications in mass spectrometry : RCM》2005,19(21):3002-3006
We describe an algorithm which modifies a protein database such that during a database search deamidation is limited to asparagines strictly contained within the N-glycosylation consensus sequence. The modified database was evaluated using a dataset created from the shotgun proteomic analysis of N-linked glycopeptides from human blood serum. We demonstrate that the application of the modified database eliminates incorrect glycopeptide assignments, reduces the peptide false-discovery rate, and eliminates the need for manual validation of glycopeptide identifications. 相似文献
79.
80.
Claesson PM Kjellin M Rojas OJ Stubenrauch C 《Physical chemistry chemical physics : PCCP》2006,8(47):5501-5514
Short-range interactions between surfactant and lipid layers are of great importance in technical applications in complex fluids such as foams, dispersions and emulsions, as well as in the formulation and performance of dispersants, detergents and flocculants. It is also of utmost importance in biological systems where interactions between biomembranes influence a range of processes. The field of short-range interactions has been thoroughly investigated during the past 30 years, following the emergence of a number of techniques to measure interaction forces. Thus, our understanding has increased considerably and it is timely to summarize relevant knowledge accumulated in this area. In this review we focus on the nature of short-range interactions between non-ionic and zwitterionic surfactant and lipid layers exposing their polar groups to the surrounding medium. We discuss the complex interplay of short-range (van der Waals, hydration, steric and other) forces based on recent theoretical and experimental results. 相似文献