全文获取类型
收费全文 | 1025篇 |
免费 | 14篇 |
国内免费 | 3篇 |
专业分类
化学 | 689篇 |
晶体学 | 11篇 |
力学 | 5篇 |
数学 | 75篇 |
物理学 | 262篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 11篇 |
2013年 | 49篇 |
2012年 | 26篇 |
2011年 | 70篇 |
2010年 | 30篇 |
2009年 | 36篇 |
2008年 | 57篇 |
2007年 | 53篇 |
2006年 | 29篇 |
2005年 | 48篇 |
2004年 | 45篇 |
2003年 | 47篇 |
2002年 | 38篇 |
2001年 | 31篇 |
2000年 | 23篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1996年 | 22篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 19篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 24篇 |
1978年 | 11篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1973年 | 8篇 |
1967年 | 4篇 |
排序方式: 共有1042条查询结果,搜索用时 78 毫秒
61.
62.
63.
Purification and magnetic properties of carbon nanotubes 总被引:7,自引:0,他引:7
S. Bandow S. Asaka X. Zhao Y. Ando 《Applied Physics A: Materials Science & Processing》1998,67(1):23-27
Received: 5 January 1998 相似文献
64.
Junji Yamauchi Takashi Ando Yasuhiro Akimoto Hisamatsu Nakano 《Fiber and Integrated Optics》1996,15(4):353-363
A wavelength filter consisting of single-mode and few-mode fibers is investigated numerically. A simple finite-difference beam-propagation method, in which a transparent boundary condition can be imposed, is developed for circularly symmetric waveguides. After confirming the validity of the numerical method by the mode-mismatch loss, we calculate the propagating field in the fiber wavelength filter, in which interference between LP01, and LP02 modes occurs. To improve the filtering operation, a depressed-index fiber is employed for the few-mode fiber. The effects of the radius and refractive index of the depressed section on the transmission power are revealed and discussed. Power is suppressed to less than 0.1% at 1.3 μm, while maintaining power transmission of more than 85% at 1.55 μm. It is also found that the filtering operation shifts to higher wavelengths as the input power is increased when we choose a self-focusing nonlinear material in the depressed section. 相似文献
65.
Ohne Zusammenfassung 相似文献
66.
67.
68.
We describe the efficient synthesis of DTPA-conjugated oligosaccharides composed of alpha- and/or beta-linked tri to monoglucosamines. Gd(iii) complex with DTPA-conjugated chitotriitol has been reported to be an effective MRI contrast agent. In order to elucidate the structure-property relationships, we planned to synthesize the DTPA-conjugated 2-amino-tri-, di-, and monosaccharides varying in configuration at the anomeric positions and the C2 position on the reducing end. Our strategy for the synthesis of the DTPA-conjugated oligosaccharides involves O-perbenzyl protected 2-amino-tri-, di-, and monosaccharides as key intermediates. The 2-aminoglycosides were prepared by non-selective glycosidation of 2-azido-2-deoxyglycosyl donors, followed by separation of two anomeric isomers. Although the synthesis involves separation of the stereoisomers, it circumvents not only the careful tuning of reaction conditions, but also the time-consuming preparation of glycosyl donors attached to different protecting groups. The protected 2-aminoglycosides were converted to the fully deprotected DTPA-conjugated tri- to monosaccharides by the same operation. MRI phantom study using the Gd(III) complexes of DTPA-conjugated oligosaccharides indicates that the number of the monosaccharide units was critical for enhancing the relative signal intensity of water protons per Gd, and various stereoisomers would be candidate scaffolds for MRI contrast agents. 相似文献
69.
Gamma-ray bursts (GRBs) are rare, powerful explosions displaying highly relativistic jets. It has been suggested that a significant fraction of the much more frequent core-collapse supernovae are accompanied by comparably energetic but mildly relativistic jets, which would indicate an underlying supernova-GRB connection. We calculate the neutrino spectra from the decays of pions and kaons produced in jets in supernovae, and show that the kaon contribution is dominant and provides a sharp break near 20 TeV, which is a sensitive probe of the conditions inside the jet. For a supernova at 10 Mpc, 30 events above 100 GeV are expected in a 10 s burst in the IceCube detector. 相似文献
70.
Although the Hall coefficient R(H) is an informative transport property of metals and semiconductors, its meaning in the cuprate superconductors has been ambiguous because of its unusual characteristics. Here we show that a systematic study of R(H) in La2-xSrxCuO4 single crystals over a wide doping range establishes a qualitative understanding of its peculiar evolution, which turns out to reflect a two-component nature of the electronic structure caused by an unusual development of the Fermi surface recently uncovered by photoemission experiments. 相似文献