全文获取类型
收费全文 | 539篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 428篇 |
晶体学 | 4篇 |
力学 | 7篇 |
数学 | 20篇 |
物理学 | 102篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 17篇 |
2016年 | 15篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 37篇 |
2012年 | 30篇 |
2011年 | 31篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 24篇 |
2007年 | 27篇 |
2006年 | 30篇 |
2005年 | 33篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1988年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1964年 | 2篇 |
1962年 | 2篇 |
1957年 | 2篇 |
1934年 | 3篇 |
排序方式: 共有561条查询结果,搜索用时 15 毫秒
511.
512.
513.
Subrahmanyam PB Sujith RI Ramakrishna M 《The Journal of the Acoustical Society of America》2003,114(2):686-696
An integral method is developed to solve the inverse problem of determining the oscillatory heat release distribution from the knowledge of the acoustic pressure field within a combustor. Unlike earlier approaches, in which the problem is formulated in terms of Fredholm integral equation, the inverse problem is reformulated in terms of Volterra integral equation. This reformulation, valid for low Mach numbers (M2 < 1), facilitates the recovery of heat release at all frequencies. The resulting Volterra integral equation is solved using both direct numerical method and implicit least-squares method. The results show that the implicit least-squares method is superior to the direct numerical method and yields accurate determination of heat release at all frequencies. 相似文献
514.
Total attenuation cross sections of copper and silver have been measured in the energy range 5 to 85 keV in a narrow beam
good geometry set up using X- andγ-rays emitted from radio isotopes, by employing a high resolution hyper pure germanium detector. From the measured values,
the photoeffect cross-sections have been derived by subtracting a small contribution of the sum of the theoretical coherent
and incoherent scattering cross sections. The photoeffect cross-sections so obtained are found to be in better agreement with
the unrenormalized values of Scofield [10]. These photoeffect cross-sections have been used to evaluate the dispersion corrections
(also called anomalous scattering factors)f
+ andf″ for the forward Rayleigh scattering amplitude by a numerical evaluation of the dispersion integral that relates them at the
energies at which the cross-sections have been measured. To thef
+ values so obtained, the relativistic corrections proposed by different investigators are included separately and the valuesf′ so obtained are compared with the available data and discussed. Possible conclusions are drawn from the present study. 相似文献
515.
The radical cations of 1,3-dioxacylohexane and 1,3-dioxacyclopentane have π-structures involving delocalisation within the [-OCH2O-]+ unit with high spin-density on the CH2 group, whilst, in complete contrast, the corresponding sulphur derivatives have a weak σ bond between the two sulphur atoms, the unpaired electron being in the σ* orbital with negligible spin-density on the CH2 group. 相似文献
516.
Joshwa D. Anthony Raj K. Seetharamiah Nagaraja M. Ramakrishna Udupa 《Transition Metal Chemistry》1986,11(5):176-178
Summary Iron-molybdenum heterometallic complexes, FeMoO2R4-(H2O) (R=8-quinolinolate, diethyldithiocarbamate, 4-morpholinyl-dithiocarbamate and piperidinyldithiocarbamate), have been prepared from iron(III) molybdate. T.l.c. and x-ray diffraction studies indicate that the complexes are discrete species. The complexes are non-electrolytes in dimethylformamide. Magnetic measurements suggest that the iron and molybdenum are in the III and V oxidation states, respectively, with octahedral geometry around each atom. I.r. spectral studies indicate the presence of MoO3+ and FeOMo bridges and the monoionic bidentate nature of the ligands. Electronic spectral and thermal decomposition studies on these complexes are reported. 相似文献
517.
518.
The extractive separation of zinc, cadmium and lead with mesityl oxide has been investigated as a function of iodide concentration and acidity. The recovery of these metals from the organic phase by back-extraction and the behaviour of other elements under the optimal conditions established for each metal ion have been examined. The method developed has been applied to the separation of these metals from rock samples before determination by spectrophotometry. 相似文献
519.
520.