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61.
Techniques for coupling mass spectrometry (MS) to thermogravimetry (TG) have been previously described. A total condensation method is best suited for identification of off-gases at various weight loss steps. For continuous monitoring of evolved components during the weight loss process, a glass-tee interface has been found effective in most applications. The present paper describes a glass tubing-tee interface used in conjunction with a sampler to provide great versatility. Both enrichment and recovery are improved without mass discrimination. The thermogravimetric analyzer can be operated under vacuum or with a gas flow. Examples will be given to illustrate the use of this technique for either qualitative or quantitative analysis of a variety of materials. 相似文献
62.
63.
Hydrodynamic experiments have been carried out with upflow of air-water mixtures through vertical seven-rod clusters at atmospheric pressure. Results obtained from measurements of flow characteristics, including pressure drops, local velocity and voidage distribution, are discussed in terms of relations developed for two-phase flow in round tubes. Effects on the flow characteristics of spacer elements and bowing of a cluster are also discussed. 相似文献
64.
W. H. Beattie 《国际化学动力学杂志》1972,4(4):463-477
The self-radiolysis of CO2 in excess tritium (3H2) has been studied at pressures of 0.1 to 1.0 atm, temperatures of ?80° to +100°C, and in the presence of added H2O, He, or Ar. The primary products of decomposition are CO and 3H2O. Secondary products are C3H4, C23H4, and a white polymer. The rates of disappearance of CO2 and formation of products and G-;values were measured. The disappearance of CO2 initially obeys first-order kinetics, then slows down with time at a rate depending upon the initial pressure of 3H2. The initial rates are proportional to pressures of CO2 and 3H2. They are independent of temperature, decreased by addition of H2O vapor, and increased by addition of He or Ar. The proposed mechanism of decomposition of CO2 and formation of products involves ionization of CO2 followed by dissociative recombination forming CO and O. Then the O reacts with a hydrogen-containing species forming OH and H2O, and a back reaction forms CO2 from CO and OH. 相似文献
65.
A flashlamp-pumped tunable dye laser has been used to investigate the a-X band system of PbO. Spectra with resolution adequate for rotational analysis were obtained by exciting a-X photoluminescence with the laser operating at a bandwidth of 0.2 cm?1. The (3,1) and (4,1) bands have been rotationally analyzed, providing the rotational constants B3 = 0.2389 ± 0.0002 cm?1 and B4 = 0.2374 ± 0.0002 cm?1 for the a state. Observation of P, Q, and R branch structure confirms the assignment of the a state as a Hund's case (c), state of PbO. Calculated combination defects having positive algebraic sign support the presence of a b(0?) state approximately 350 cm?1 above the a(1) state. 相似文献
66.
D. W. Beattie 《The Journal of the Operational Research Society》1969,20(4):429-435
Some practical experiences in collaborating with a marketing department in deciding whether or not to test-market before launching a new product. The benefits derived from the use of elementary decision-tree theory are described. 相似文献
67.
The ability of thermal evolution techniques for polymer characterization is greatly enhanced when spectroscopic methods are combined, thus allowing identification of the off-gases. This work describes a thermal evolution—differential trapping—mass spectrometric technique for analysis of polymer systems. The technique involves heating the sample under controlled temperature and pressure conditions, condensing the evolved gases in traps maintained at various temperatures, continuously monitoring the pressure changes at strategic locations, and analyzing the selectivity trapped volatiles by mass spectrometry. Both qualitative and quantitative aspects of the technique will be discussed. 相似文献
68.
69.
70.
Summary.
New approaches for computing tight lower
bounds to the eigenvalues of a class of
semibounded self-adjoint operators are
presented that require comparatively
little a priori spectral information and permit the
effective use of (among others) finite-element trial functions.
A variant of the method of intermediate problems making use
of operator decompositions having the form
is
reviewed and then developed into a new framework based on
recent inertia results in the Weinstein-Aronszajn theory. This
framework provides greater flexibility in analysis and permits
the formulation of a final computational task involving
sparse, well-structured matrices. Although our derivation is
based on an intermediate problem formulation, our results
may be specialized to obtain either the Temple-Lehmann
method or Weinberger's matrix method.
Received December 12, 1992 / Revised version
received October 5, 1994 相似文献