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41.
Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Vologouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Watts T Webb R Wenzel H Wester WC Wicklund AB Wicklund E Williams HH Wilson P 《Physical review letters》2000,84(8):1663-1668
We have studied the production of B hadrons in 1.8-TeV pp[over ˉ] collisions. We present measurements of the fragmentation fractions, f_{u}, f_{d}, f_{s}, and f_{baryon}, of produced b quarks that yield B^{+}, B^{0}, B_{s}^{0}, and Λ[over ˉ]_{b}^{0} hadrons. Reconstruction of five electron-charm final states yields f_{s}/( f_{u}+f_{d})=0.213±0.068 and f_{baryon}/( f_{u}+f_{d})=0.118±0.042, assuming f_{u}=f_{d}. If all B hadrons produced in pp[over ˉ] collisions cascade to one of these four hadrons, we determine f_{u}=f_{d}=0.375±0.023, f_{s}=0.160±0.044, and f_{baryon}=0.090±0.029. If we do not assume f_{u}=f_{d}, we find f_{d}/f_{u}=0.84±0.16. 相似文献
42.
43.
Krohn S Lange M Grieser M Knoll L Kreckel H Levin J Repnow R Schwalm D Wester R Witte P Wolf A Zajfman D 《Physical review letters》2001,86(18):4005-4008
The dissociative recombination of LiH+ ions with low-energy electrons is observed at a storage ring and the final states are analyzed using fragment imaging and field ionization techniques. The rate coefficient is found to be larger than its estimated value used in astrophysical models. Mostly the highest energetically possible Rydberg states of the lithium atom are populated by the reaction, indicating a common trend for molecular recombination via the noncrossing mode. 相似文献
44.
Olga Fedorova Olga Kuznetsova Maria Stepanova Victor Maleev Yuri Belokon Hans-Juergen Wester Raisa Krasikova 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(2):505-512
Due to favourable in vivo characteristics, its high specificity and the longer half-life of 18F (109.8 min) allowing for remote-site delivery, O-(2-[18F]fluoroethyl)-l-tyrosine ([18F]FET) has gained increased importance for molecular imaging of cerebral tumors. Consequently, the development of simple and efficient production strategies for [18F]FET could be an important step to further improve the cost-effective availability of [18F]FET in the clinical environment. In the present study [18F]FET was synthesized via direct nucleophilic synthesis using an earlier developed chiral precursor, the NiII complex of an alkylated (S)-tyrosine Schiff base, Ni-(S)-BPB-(S)-Tyr-OCH2CH2OTs. The purification method has been developed via solid phase extraction thereby omitting cumbersome HPLC purification. The suggested SPE purification using combination of reverse phase and strong cation exchange cartridges provided [18F]FET in high chemical, radiochemical and enantiomeric purity and 35 % radiochemical yield (decay-corrected, 45 min synthesis time). The method was successfully automated using a commercially available synthesis module, Scintomics Hotboxone. Based on the current results, the proposed production route appears to be well suited for transfer into an automated cassette-type radiosynthesizers without using HPLC. 相似文献
45.
Franziska Dahlmann Dennis F. Dinu Dr. Pavol Jusko Christine Lochmann Thomas Gstir Aravindh N. Marimuthu Prof. Dr. Klaus R. Liedl Prof. Dr. Sandra Brünken Prof. Dr. Roland Wester 《Chemphyschem》2023,24(15):e202300262
We present infrared predissociation spectra of C2N−(H2) and C 3N−(H2) in the 300–1850 cm−1 range. Measurements were performed using the FELion cryogenic ion trap end user station at the Free Electron Lasers for Infrared eXperiments (FELIX) laboratory. For C2N−(H2), we detected the CCN bending and CC−N stretching vibrations. For the C3N−(H2) system, we detected the CCN bending, the CC−CN stretching, and multiple overtones and/or combination bands. The assignment and interpretation of the presented experimental spectra is validated by calculations of anharmonic spectra within the vibrational configuration interaction (VCI) approach, based on potential energy surfaces calculated at explicitly correlated coupled cluster theory (CCSD(T)-F12/cc-pVTZ−F12). The H2 tag acts as an innocent spectator, not significantly affecting the C2,3N− bending and stretching mode positions. The recorded infrared predissociation spectra can thus be used as a proxy for the vibrational spectra of the bare anions. 相似文献
46.
J. Levin U. Hechtfischer L. Knoll M. Lange G. Saathoff R. Wester A. Wolf D. Schwalm D. Zajfman 《Hyperfine Interactions》2000,127(1-4):267-270
When infrared active molecular ions are stored in a heavy ion storage ring, a fast beam of vibrationally and rotationally
relaxed molecules can be obtained. This opens up new opportunities for various experimental studies in molecular ion physics,
particularly those involved with spectroscopy and dissociation dynamics of excited states. The analysis of such experiments
is facilitated by the fact that the information on the initial states is able to identify and, therefore, eliminate them from
the assignment problem. Moreover, when the intensity of the measured transitions is monitored as a function of storage time,
the dependence of these processes on the degree of internal relaxation is revealed. We demonstrate these general principles
by application to near threshold dissociation spectroscopy of the OH+ molecular ion. The structure of quasibound levels near the dissociation limit of OH+ and its dissociation energy are deduced.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
47.
A common approach for comparing the structures of biomolecules or solid bodies is to translate and rotate one structure with respect to the other to minimize the pointwise root-mean-square deviation (RMSD). We present a new, robust numerical algorithm that computes the RMSD between two molecules or all the mutual RMSDs of a list of molecules and, if desired, the corresponding rotation matrix in a minimal number of operations as compared to previous algorithms. The RMSD gradient can also be computed. We address the problem of symmetry, both in alignment (possible alternative alignments due to indistinguishable atoms) as well as geometry. In the latter case, it is possible to have degenerate superposition. A necessary condition is optimal superimposability to one's mirror image. Double (respectively, triple) degeneracy results in a one- (respectively, two)-parameter family of rotations leaving the superposition invariant. The software, frmsd , is freely available at http://www.ams.stonybrook.edu/~coutsias/codes/frmsd.tgz . © 2019 Wiley Periodicals, Inc. 相似文献
48.
G. Ooms C. Poelma P. Poesio MJ.B.M. Pourquie J. Westerweel 《International Journal of Multiphase Flow》2008
In an earlier publication some of the authors presented a theoretical model for the calculation of the influence of particle inertia and gravity on the turbulence in a stationary particle-laden flow. In the present publication the model is extended for application to a decaying suspension. Also a comparison is given between predictions made with the model and experimental data (own data and data reported in the literature) on a decaying turbulent flow with particles in a water tunnel or in a wind tunnel. For most of the experiments a prediction with reasonable accuracy and an interpretation is possible by means of the model. 相似文献
49.
50.
In this study, we report on the radical [18F]fluoroarylation of different olefins using 4-[18F]fluorobenzenediazonium ions to provide a new route to radiopharmaceuticals containing a deactivated, 4-[18F]fluoro substituted phenyl group. This new methodology was shown to be well suited for the synthesis of 18F-labelled stilbenes. Stilbene 7 is now accessible within 80 min in 30-45% overall radiochemical yield starting from [18F]fluoride. 相似文献