全文获取类型
收费全文 | 362篇 |
免费 | 7篇 |
专业分类
化学 | 121篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 56篇 |
物理学 | 78篇 |
无线电 | 96篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 17篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 11篇 |
2008年 | 18篇 |
2007年 | 14篇 |
2006年 | 8篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 30篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1934年 | 2篇 |
1886年 | 1篇 |
排序方式: 共有369条查询结果,搜索用时 62 毫秒
331.
D. Gihwala I. S. Giles C. Olivier M. Peisach 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(2):333-341
The prompt gamma-ray of 871 keV emitted during the bombardment of steels by 5 MeV alpha particles were used to determine nitrogen
by means of the reaction14N(α, pγ)17O. The method is non-destructive, rapid and experimentally simple. It has a sensitivity of about 7 μg·g−1. In the nitrogen concentration range of 101–102 μg·g−1 the relative precision of the method is about 3%. The accuracy of the method compares with that of other nuclear methods.
Presented at the 5th Symposium on Recent Developments in Activation Analysis, Oxford, 17–21 July, 1978. 相似文献
332.
Under simulated environmental (atmospheric) conditions, chloropicrin vapor was readily converted in light to phosgene, which remained stable, and nitrosyl chloride which was subsequently photolyzed to nitric oxide and chlorine; a portion of the nitric oxide was oxidized to nitrogen dioxide and dinitrogen tetroxide. The unexpected dependence of the reaction upon oxygen, the initial photoproducts, and the incorporation of 18O when the photolysis occurred in the presence of 18O2 suggest an intramolecular rearrangement involving a trioxazole N-oxide. 相似文献
333.
334.
Giles Auchmuty 《Numerische Mathematik》1992,61(1):1-6
Summary This paper describes upper and lowerp-norm error bounds for approximate solutions of the linear system of equationsAx=b. These bounds imply that the error is proportional to the quantity
wherer is the residual andq is the conjugate index top. The constant of proportionality is larger than 1 and lies in a specified range. Similar results are obtained for approximations toA
–1 and solutions of nonsingular linear equations on general spaces.Research was partially supported by NSF Grant DMS8901477 相似文献
335.
Ryf R. Su Y. Moller L. Chandrasekhar S. Xiang Liu Neilson D.T. Giles C.R. 《Lightwave Technology, Journal of》2005,23(1):54-61
This work presents a high-resolution (13.2 GHz) channel-blocking optical filter, suitable for use as a reconfigurable optical add/drop multiplexer (ROADM), which seamlessly supports data rates from 2.5 to 160 Gb/s. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating. The demonstrated device had an insertion loss of 9 dB, a loss ripple of 1.2 dB, and a group delay ripple of 15 ps. Data transmission through the device with various mixed data rate scenarios ranging from 2.5 to 160 Gb/s showed negligible penalty, except at 40 Gb/s where a maximum penalty of 1.5 dB was observed due to a phase coherence with the blocker filter ripple. 相似文献
336.
E. Mané J. Billowes K. Blaum P. Campbell B. Cheal P. Delahaye K. T. Flanagan D. H. Forest H. Franberg C. Geppert T. Giles A. Jokinen M. Kowalska R. Neugart G. Neyens W. N?rtersh?user I. Podadera G. Tungate P. Vingerhoets D. T. Yordanov 《The European Physical Journal A - Hadrons and Nuclei》2009,42(3):503-507
A gas-filled segmented linear Paul trap has been installed at the focal plane of the high-resolution separator (HRS) at CERN-ISOLDE. As well as providing beams with a reduced transverse emittance, this device is also able to accumulate the ions and release the sample in bunches with a well-defined time structure. This has recently permitted collinear laser spectroscopy with stable and radioactive bunched beams to be demonstrated at ISOLDE. Surface-ionized 39, 44, 46K and 85Rb beams were accelerated to 30keV, mass separated and injected into the trap for subsequent extraction and delivery to the laser setup. The ions were neutralized in a charge exchange cell and excited with a co-propagating laser. The small ion beam emittance allowed focussing in the ion-laser overlap region, which is essential to achieve the best experimental sensitivity. Fluorescent photons were detected by a photomultiplier tube as a frequency scan was taken. A gate (typically 7-12μs wide) was set on the photomultiplier signal to accept the fluorescent photons within the time window defined by the bunch. Thus, using accumulation times of 100ms, the dominant contribution to background due to continuous laser scattering could be reduced by a factor of up to 4×104 . 相似文献
337.
E. D. Johnson G. V. Rogachev V. Z. Goldberg S. Brown D. Robson A. M. Crisp P. D. Cottle C. Fu J. Giles B. W. Green K. W. Kemper K. Lee B. T. Roeder R. E. Tribble 《The European Physical Journal A - Hadrons and Nuclei》2009,42(2):135-139
The structure of the 18O nucleus at excitation energies above the $ \alpha$ decay threshold was studied using 14C + $ \alpha$ resonance elastic scattering. A number of states with large $ \alpha$ reduced widths have been observed, indicating that the $ \alpha$ -cluster degree of freedom plays an important role in this N $ \ne$ Z nucleus. A 0+ state with an $ \alpha$ reduced width exceeding the single-particle limit was identified at an excitation energy of 9.9±0.3 MeV. We discuss evidence that states of this kind are common in light nuclei and give possible explanations of this feature. 相似文献
338.
Andrew T. Rhead Richard Butler Giles W. Hunt 《International Journal of Solids and Structures》2008,45(16):4349-4361
An analytical model for prediction of compressive fatigue threshold strains in composite plates with barely visible impact damage (BVID) is presented. The model represents the complex damage morphology as a single circular delamination at a critical level and calculates the strain at which thin-film buckling of the circular delaminated region occurs. The threshold strain is defined as the strain at which the strain energy release rate for the fracture of post-buckled delaminated plies along the delamination is equal to the critical Mode I value (G1C) for the resin. The model predicts the critical through-thickness level for delamination, the stability of delamination growth and also the sensitivity to experimental error in geometric measurements of the damage area. Results obtained using the model show an agreement of fatigue strain to within 4% of experimental values for four sets of data reported in the literature. 相似文献
339.
Mario M. Attard Giles W. Hunt 《International Journal of Solids and Structures》2008,45(14-15):4322-4339
Column constitutive relationships and buckling equations are derived using a consistent hyperelastic neo-Hookean formulation. It is shown that the Mandel stress tensor provides the most concise representation for stress components. The analogous definitions for uniaxial beam plane stress and plane strain for large deformations are established by examining the virtual work equations. Anticlastic transverse curvature of the beam cross-section is incorporated when plane stress or thick beam dimensions are assumed. Column buckling equations which allow for shear and axial deformations are derived using the positive definiteness of the second order work. The buckling equations agree with the equation derived by Haringx and are extended to incorporate anticlastic transverse curvature which is important for low slenderness, high buckling modes and with increasing width to thickness ratio. The work in this paper does not support the existence of a shear buckling mode for straight prismatic columns made of an isotropic material. 相似文献
340.
The macro-buckling equations for a sandwich column are developed. A layer-wise Timoshenko beam displacement approximation is assumed. The constitutive relationships and equilibrium equations for the core and face sheets are derived using a consistent hyperelastic neo-Hookean formulation. The derivations in this paper are consistent with that of Haringx’s and Reissner’s proposal for beam actions. The buckling formulation includes the axial deformation prior to buckling and the transverse shear deformation of the core and face sheets. The buckling equations derived agree with the equation of [Allen, H.G., 1969. Analysis and Design of Structural Sandwich Panels, Pergamon, Oxford] for thick faces but are also applicable to any ratio of face sheet to core thickness and material properties. The formulation is compared to experimental results for sandwich columns and shows good comparison except for very short columns. The formulation is also compared to the buckling experimental results for short rubber rods and also compared well. The formulation does not predict a shear buckling mode. 相似文献