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11.
12.
Isobaric daughter ions formed from a common metastable ion have been analysed at high mass resolution. A three-dimensional representation is used to summarize the data for competitive CO and C2H4 losses and competitive CHO˙ and C2H5˙ losses from metastable molecular ions of cyclohexanone. 相似文献
13.
Eric E. Kingston James S. Shannon Michael J. Lacey 《Journal of mass spectrometry : JMS》1983,18(5):183-192
Rearrangements reported in the literature for positive ions formed by chemical ionization are briefly reviewed, with particular emphasis on illustrative examples of hydrogen and skeletal rearrangements. 相似文献
14.
Chung P Ajitanand NN Alexander JM Anderson M Best D Brady FP Case T Caskey W Cebra D Chance JL Cole B Crowe K Das A Draper JE Gilkes ML Gushue S Heffner M Hirsch AS Hjort EL Huo L Justice M Kaplan M Keane D Kintner JC Klay J Krofcheck D Lacey RA Lauret J Lisa MA Liu H Liu YM McGrath R Milosevich Z Odyniec G Olson DL Panitkin SY Pinkenburg C Porile NT Rai G Ritter HG Romero JL Scharenberg R Schroeder L Srivastava B Stone NT Symons TJ Wienold T Witt R Whitfield J Wood L Zhang WN;E Collaboration 《Physical review letters》2001,86(12):2533-2536
Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy. 相似文献
15.
Sun R Colin E Ajitanand NN Alexander JM Barton MA DeYoung PA Drake KL Elmaani A Gelderloos CJ Gualtieri EE Guinet D Hannuschke S Jaasma JA Kowalski L Lacey RA Lauret J Norbeck E Pak R Peaslee GF Stern M Stone NT Sundbeck SD Vander Molen AM Westfall GD Yang LB Yee J 《Physical review letters》2000,84(1):43-46
For central collisions of (17-115)A MeV 40Ar+Cu, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1-2 GeV. For such high deposition energies, statistical multifragmentation models predict much more extensive nuclear disassembly than is observed. 相似文献
16.
Cristian E. Lacey Alex G. Novoselov Michael E. Mueller 《Proceedings of the Combustion Institute》2021,38(2):2673-2680
Reduced-order manifold approaches to turbulent combustion modeling traditionally involve precomputation of manifold solutions and pretabulation of the thermochemical database versus a small number of manifold variables. However, additional manifold variables are required as the complexity of turbulent combustion processes increases through consideration of, for example, multi-modal, non-adiabatic, or non-isobaric combustion, or combustion featuring multiple and/or inhomogeneous inlets. This increase in the number of manifold variables comes with an increase in the computational cost of precomputing a greater number of manifold solutions, most of which are never actually utilized in a CFD calculation. The memory required to store the pretabulated high-dimensional thermochemical database also increases, practically limiting the complexity of manifold-based combustion models. In this work, a new In-Situ Adaptive Manifolds (ISAM) approach is developed that overcomes this limitation by combining ‘on-the-fly’ calculation of manifold solutions with In-Situ Adaptive Tabulation (ISAT), enabling the use of more complex manifold-based turbulent combustion models. The performance of ISAM is evaluated via LES of turbulent nonpremixed jet flames with both hydrogen and hydrocarbon fuels. A performance assessment indicates that the computational overhead associated with ISAM compared to pretabulation ranges from negligible up to a factor of two, with most of this overhead associated with convolution of the thermochemical state against a presumed subfilter PDF. In addition, the memory requirements of ISAM are more than two orders of magnitude less than conventional tabulation. These results demonstrate the potential for ISAM to accommodate significantly more complex manifold-based combustion models. 相似文献
17.
Bauer MD Sun Y Keough T Lacey MP 《Rapid communications in mass spectrometry : RCM》2000,14(10):924-929
We report the application of nanoelectrospray ionization tandem mass spectrometry (nES-MS/MS) and capillary LC/microelectrospray MS/MS (cLC/&mgr;ES-MS/MS) for sequencing sulfonic acid derivatized tryptic peptides. These derivatives were specifically prepared to facilitate low-energy charge-site-initiated fragmentation of C-terminal arginine-containing peptides, and to enhance the selective detection of a single series of y-type fragment ions. Both singly and doubly protonated peptides were analyzed by MS/MS and the results were compared with those from their derivatized counterparts. Model peptides and peptides from tryptic digests of gel-isolated proteins were analyzed. Derivatized singly protonated peptides fragment in the same way by nES-MS/MS as they do by post-source decay matrix-assisted laser desorption/ionization mass spectrometry (PSD-MALDI-MS). They produce fragment ion spectra dominated by y-ions, and the simplified spectra are readily interpreted de novo. Doubly protonated peptides fragment in much the same way as their non-derivatized doubly protonated counterparts. The fragmentation of doubly protonated derivatives is especially useful for sequencing peptides that possess a proline residue near the N-terminus of the molecule. The singly protonated forms of these proline-containing derivatives often show enhanced fragmentation on the N-terminal side of the proline and considerably reduced fragmentation on the C-terminal side. In addition, sulfonic acid derivatization increases the in-source fragmentation of arginine-containing peptides. This could be useful for sequence verification and sequence tagging for use in single stage mass spectrometry. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
18.
Tracy P. Houghton David N. Thompson J. Richard Hess Jeffrey A. Lacey Michael P. Wolcott Anke Schirp Karl Englund David Dostal Frank Loge 《Applied biochemistry and biotechnology》2004,113(1-3):71-93
Combining biologic pretreatment with storage is an innovative approach for improving feedstock characteristics and cost, but
the magnitude of responses of such systems to upsets is unknown. Unsterile wheat straw stems were upgraded for 12 wk with
Pleurotus ostreatus at constant temperature to estimate the variation in final compositions with variations in initial moisture and inoculum.
Degradation rates and conversions increased with both moisture and inoculum. A regression analysis indicated that system performance
was quite stable with respect to inoculum and moisture content after 6 wk of treatment. Scale-up by 150× indicated that system
stability and final straw composition are sensitive to inoculum source, history, and inoculation method. Comparative testing
of straw-thermoplastic composites produced from upgraded stems is under way. 相似文献
19.
X-ray diffraction has been used to study the nematic phases of the cis and trans isomers of an elongated molecule containing the cyclobutane group. It has been shown that these nematic phases consist of a mixture of single molecules and overlapping core dimers. It has been found that increasing the temperature of the cis isomer rapidly reduces the dimer population, whereas increasing the temperature of the trans isomer enhances the dimer population. This provides an explanation of the relatively high clearing temperature of the trans isomer. The different temperature dependences of the dimer population in the cis and trans isomers has been explained by a model involving inversion of the cylobutane group. 相似文献
20.
The plasma desorption (PD) mass spectra of several enzymes and proenzymes are reported. Chymotrypsin and chymotrypsinogen both yield usable PD mass spectra; however, the single-chain chymotrypsinogen exhibits better sensitivity and less fragmentation than the multi-chain chymotrypsin. Porcine pepsinogen contains 11 more basic residues (lysine and arginine) than porcine pepsin, but this does not lead to an increase in positive ion response. In fact, the additional basic residues may hinder response by increasing the strength of the interaction between the protein and the nitrocellulose surface. A series of subtilisins showed comparable PD mass spectrometric, response despite the fact that they differ considerably in primary sequence. Finally, PD mass spectrometry was used to correct the previously reported mass of a heat-stable protease, a value that we found to be in error by almost 5000 Da. 相似文献