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101.
2 +? O2→H2O on polycrystalline Pt foils has been studied by detection of desorbing OH radicals using the Resonance Enhanced Multiphoton
Ionization, REMPI, technique. The measurements were performed at catalyst temperatures of 1000–1400 K and a total pressure
below 10-4 mbar. The studies of OH desorption by REMPI were achieved using a two-photon excitation D2Σ-–X2Π (1–0), followed by one-photon ionization. The ions were detected in a time-of-flight mass spectrometer, TOF-MS, in order
to avoid interference from non-resonantly ionized molecules. By applying TOF-MS, a simultaneous non-resonant ionization and
detection of H2, O2 and H2O was achieved. Recorded REMPI spectra were compared with spectra simulated using known molecular constants. The kinetics
of the reaction derived from the measurements were compared with what was obtained in earlier LIF detection of OH, performed
at higher total reactant pressure using the A–X transition. REMPI TOF-MS is shown to be a complement to LIF for reaction studies
below 5×10-4 mbar total pressure, where LIF is too insensitive for quantification. The reaction kinetics was found to be in agreement
with a theoretic model and previous LIF studies.
Received: 8 March 1996/Revised version: 4 October 1996 相似文献
102.
H. Andersson 《Accreditation and quality assurance》2002,7(6):228-233
When a test is performed in order to qualify a material or a product for a certain use, the result is generally compared with
an acceptance limit. The test result has an uncertainty which should be estimated and stated (e.g. in accordance with GUM).
Very often this is not the case. Further, discussions often arise on the issue of how the uncertainty shall be considered
in relationship to the acceptance limit. The intention of this note is to describe, in simple terms, the statistical background
and to give some recommendations. In short, there are two clean-cut, extreme situations. The first case is when the uncertainty
of the testing procedure is the dominating factor. Here it is found that the estimates of single laboratories cannot, generally,
be used for comparisons with acceptance limits. One should have standardised, well-verified estimates based on comprehensive
investigations of the method. It can also be concluded that comparisons between test results and acceptance limits have to
be made with regard to the actual circumstances, as, e.g. how the acceptance limit is related to the risk. In the second case,
the variation in the property of the material or product dominates and the uncertainty of the testing procedure is negligible.
When the results are non-quantitative (go – no go), statistical methods can be used to estimate the risk taken with a certain
sampling and acceptance strategy that a certain proportion of the batch to be delivered does not qualify. This should be considered
more often in standardisation of product test methods. When the results are quantitative, a statistical analysis should be
performed and the uncertainty should be compared with the acceptance limit as before, from the actual circumstances. When
effects of testing uncertainty and product variation are comparable a sound treatment requires extensive experimental work.
No short cuts can be made without loss of confidence!
Received: 17 August 2001 Accepted: 21 March 2002 相似文献
103.
C. G. Andersson 《Zeitschrift für Physik A Hadrons and Nuclei》1980,295(4):349-354
Different ways of treating the pairing interaction in the particle-rotor model are discussed and compared in a model which can be solved exactly. Special attention is paid to the interaction between the yrast and yrare bands as function of the shell filling. 相似文献
104.
The photochemical isomerization of 1,2-di(9-anthryl)ethane can be sensitized by biacetyl to proceed by intramolecular Diels-Alder reaction. The molecular geometry of dianthrylethanes affects their triplet state reactivity. 相似文献
105.
The paper introduces the framework, problems addressed, objective function, types of variables and so on for a model designed to facilitate the economic evaluation of master city plans. The model presented here has been used in a pilot study of the city of Västerås, Sweden. It consists of three main parts, data, results and method. Some conclusions are drawn. 相似文献
106.
Energies of high spin states are calculated with the use of an oblate deformed oscillator potential with the purpose of finding possible yrast traps or isomers. Pairing forces are included and different methods of solving the pairing Hamiltonian (including the exact solution) are compared. The stability of the oblate regime against gamma vibrations is investigated with use of the random phase approximation. Pairing forces are included also here. 相似文献
107.
G. Andersson M. Areskoug H.-Å. Gustafsson G. Hylten B. Schrøder E. Hagebø 《Physics letters. [Part B]》1976,64(4):421-423
The binary fission process in 159Tb and natAg induced by 600 MeV protons has been investigated yielding fission cross sections (1.9 and 1.0 mb, respectively) and mean values of the total kinetic energies (100 and 62 MeV, respectively). 相似文献
108.
109.
110.
The c(2 × 2) configuration of CO chemisorbed on Ni(100) has been examined by the dynamical LEED method of surface structure analysis. Experimental LEED intensity spectra of the (00), () (10) and (11) LEED beams measured at 175 K are compared with the corresponding calculated spectra for two different CO potential constructions and a number of trial structures. The best agreement was found for a structure where the CO molecules sit directly above the Ni atoms with vertical spacings between the Ni and C and the C and O layers of 1.80 ± 0.10 A and 0.95 ± 0.10 Å respectively. It is proposed that the CO molecule is tipped over at an angle of 34° ± 10° with respect to the surface normal so that the actual carbon-oxygen bond length is close to the figure 1.15 Å found in Ni(CO)4. 相似文献