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151.
J. Ashman B. Badelek G. Baum J. Beaufays C. P. Bee C. Benchouk I. G. Bird S. C. Brown M. C. Caputo H. W. K. Cheung et al. 《Zeitschrift fur Physik C Particles and Fields》1993,57(2):211-218
Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function,F
2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.Supported by Bundesministerium für Forschung und Technologie 相似文献
152.
First measurement of the left-right cross section asymmetry in Z boson production by e+e- collisions
Abe K Abt I Acton PD Adolphsen CE Agnew G Alber C Alzofon DF Antilogus P Arroyo C Ash WW Ashford V Astbury A Aston D Au Y Axen DA Bacchetta N Baird KG Baker W Baltay C Band HR Baranko G Bardon O Barrera F Battiston R Bazarko AO Bean A Beer G Belcinski RJ Bell RA Ben-David R Benvenuti AC Berger R Berridge SC Bethke S Biasini M Bienz T Bilei GM Bird F Bisello D Blaylock G Blumberg R Bogart JR Bolton T Bougerolle S Bower GR Boyce RF Brau JE Breidenbach M Browder TE Bugg WM Burgess B Burke D 《Physical review letters》1993,70(17):2515-2520
153.
Abe F Albrow MG Amidei D Antos J Anway-Wiese C Apollinari G Areti H Atac M Auchincloss P Azfar F Azzi P Bacchetta N Badgett W Bailey MW Bao J de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Bartalini P Bauer G Baumann T Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Benjamin D Benlloch J Bensinger J Benton D Beretvas A Berge JP Bertolucci S Bhatti A Biery K Binkley M Bird F Bisello D Blair RE Blocker C Bodek A Bokhari W Bolognesi V Bortoletto D Boswell C Boulos T Brandenburg G 《Physical review letters》1995,74(6):850-854
154.
We present a new global optimization approach for solving exactly or inexactly constrained distance geometry problems. Distance geometry problems are concerned with determining spatial structures from measurements of internal distances. They arise in the structural interpretation of nuclear magnetic resonance data and in the prediction of protein structure. These problems can be naturally formulated as global optimization problems which generally are large and difficult. The global optimization method that we present is related to our previous stochastic/perturbation global optimization methods for finding minimum energy configurations, but has several key differences that are important to its success. Our computational results show that the method readily solves a set of artificial problems introduced by Moré and Wu that have up to 343 atoms. On a set of considerably more difficult protein fragment problems introduced by Hendrickson, the method solves all the problems with up to 377 atoms exactly, and finds nearly exact solution for all the remaining problems which have up to 777 atoms. These preliminary results indicate that this approach has very good promise for helping to solve distance geometry problems. 相似文献
155.
The treatment of l, 2, 3, 4, 4a, 9b-hexahydro-3, 8-dihydroxy-7-methoxy-9b-(2'-methoxyethyl)dibenzofuran with chloroform and aqueous potassium hydroxide under conventional Reimer-Tiemann reaction conditions resulted in the replacement of the 7-methoxyl group by a carbaldehyde one. A choice between alternative pathways for this novel displacement has been facilitated by examination of the behaviour of the corresponding 7-trideuteromethoxy compound. Dichlorocarbene attack at position 7 rather than at the unsubstituted position 9 is shown to be due to steric encumbrance at the latter site. 相似文献
156.
A method is presented for calculating electron-hole pair excitation due to an incident atom or molecule interacting with a metal surface. Energy loss is described using an ab initio approach that obtains a position-dependent friction coefficient for an adsorbate moving near a metal surface from a total energy pseudopotential calculation. A semiclassical forced oscillator model is constructed to describe excitation of the electron gas due to the incident molecule. This approach is applied to H and D atoms incident on a Cu(111) surface, and we obtain theoretical estimates of the "chemicurrents" measured by Nienhaus et al. [Phys. Rev. Lett. 82, 446 (1999)] for these atoms incident on the surface of a Schottky diode. 相似文献
157.
Lynas JF Martin SL Walker B Baxter AD Bird J Bhogal R Montana JG Owen DA 《Combinatorial chemistry & high throughput screening》2000,3(1):37-41
A series of N-alpha-mercaptoacetyl containing dipeptides have been prepared on solid-phase supports as putative matrix metalloprotease (MMP) inhibitors. Inhibitor design was based on a positional scanning approach of the amino acids present within a template molecule, previously shown to be an MMP inhibitor with good pharmacological characteristics. This study is the first step in a unique programme, designed to expand the repertoire of molecular templates which can be chosen as starting points for the development of more focused parallel and/or combinatorial libraries of MMP inhibitors as a means to accelerate the lead discovery process. This paper reports the success of such an approach in the development of agents with activity against a number of pathologically important MMPs. After screening of these positional scanning libraries, we have obtained important SAR information, in particular, pharmacophores with the ability to impart selectivity for particular MMP species. 相似文献
158.
Measured binding energies were found to vary with the choice of reference binding energies used in instrument calibration. Inadequate linearity of the spectrometer energy scale was eliminated as a source of the error. Primary calibration methods were considered, and tried. The instrument was finally set up by the two X-ray wavelength method, using Al Kα and the Ag Lα,β radiations. Subsequent re-determination of electron binding energies for noble metals and copper showed differences from previously adopted values that would be important in calibration work. 相似文献
159.
160.
The fluid forces resulting from wave interaction with large submerged structures may be calculated using numerical procedures based on the solution of the associated boundary-value problem. In this paper, the analysis of wave interaction with a fixed submerged object of arbitrary cross-section and infinite length using a two-dimensional boundary value formation based on linear diffraction theory is summarized. Subsequently, the application of the boundary element method to obtain a solution is presented. The numerical considerations are emphasized with particular reference to computational efficiency. Numerical results are presented in the form of dimensionless wave force plots for various structural shapes. In the case of a bottom-seated half cylinder, for which there exists a closed-form solution, comparisons are made between results generated using both boundary element and equivalent finite element approaches. In the case of a submerged cylinder, comparisons are made between boundary element derived values and experimental results. The boundary element results compare well with both the closed-form solution and the experimental values. 相似文献