全文获取类型
收费全文 | 181篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 96篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 27篇 |
物理学 | 57篇 |
出版年
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 14篇 |
2006年 | 16篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1967年 | 1篇 |
1958年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有185条查询结果,搜索用时 15 毫秒
91.
Y. Watanabe M. Abolhassani Y. Tojo Y. Suda K. Miyazawa Y. Igarashi K. Sakuma T. Ogawa K. Muramoto 《Journal of chromatography. A》2009,1216(48):8563-8566
Columns of phosphorylcholine (PC) immobilized on silica gel were shown to be useful for size exclusion chromatography (SEC) of proteins. The columns provided good separation of proteins in 50 mM sodium phosphate buffer (pH 6.9) containing 0.25 M NaCl, and there was a linear relationship between the retention times and the logarithmic values of the molecular weights with a correlation coefficient (R2) of 0.978–0.992. The columns were used in analyzing the subunit structures of the rhamnose-binding lectins CSL1, CSL2, and CSL3, isolated from chum salmon (Oncorhynchus keta) eggs. Although the lectins, which are a group of carbohydrate-binding and hydrophobic proteins, behaved anomalously in SEC with conventional matrices, they could be eluted from the immobilized PC columns without non-size-related retention, thereby allowing their molecular weights to be reliably estimated. 相似文献
92.
We report a beam-shaping technique that reconfigures the beams to improve the beam quality and enhance the power density for a ten-array high-power laser-diode stack by using two optical rectangular cubes and two stripe-mirror plates. The reshaped beam has threefold improvement in beam quality, and its power density is effectively enhanced. On the basis of this technique, we focus the beam of the high-power laser-diode stack to effectively end pump a high-power fiber laser. 相似文献
93.
SnO2 powders, doped with various 57Fe contents were prepared by a sol-gel method, and annealed finally at 500 °C and 650 °C. These samples were characterized by Mössbauer spectroscopy, vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) to investigate the relationship of magnetic properties, grain sizes, annealing temperatures and Mössbauer parameters. The particle sizes of SnO2 powders reduced to less than 100 nm with the increase of Fe contents up to 5%. Rutile SnO2 was the only phase obtained for all samples. Room temperature Mössbauer spectra suggest the presence of two different paramagnetic iron sites for all samples and one magnetically relaxed species for those samples with the lowest iron concentrations. The magnetization increased with the Fe content, but was reduced for the samples annealed at 650 °C perhaps due to a segregation of α-Fe2O3 doped with tin. 相似文献
94.
To each once-punctured-torus bundle, Tφ, over the circle with pseudo-Anosov monodromy φ, there are associated two tessellations of the complex plane: one, Δ(φ), is (the projection from ∞ of) the triangulation of a horosphere at ∞ induced by the canonical decomposition into ideal tetrahedra, and the other, CW(φ), is a fractal tessellation given by the Cannon-Thurston map of the fiber group switching back and forth between gray and white each time it passes through ∞. In this paper, we fully describe the relation between Δ(φ) and CW(φ). 相似文献
95.
The acoustic effects of stage risers, especially on the sound of lower string instruments, are numerically and experimentally analyzed. To discuss the effects of the vibration of riser’s boards due to the mechanical force from an instrument, a structural-acoustical coupling approach is applied based on the mode expansion and the boundary element technique. Measurement results of the mechanical force from real instruments are used in the numerical study. The vibration of the top board of a riser affects the sound field only around the natural frequencies of the board and the cavity of the riser. In contrast, the acoustic diffraction due to the riser affects the sound field in a wide frequency range. The riser’s sideboard that faces to receiving points increases the sound pressure levels because it reflects waves diffracted at the riser’s edge to the front. To verify the numerical results, the effects of acoustic diffraction due to risers are especially investigated in detail through a scale model experiment. 相似文献
96.
Takahiro Natsume Tomoyasu Amano Yasuo Takehara Takashi Ichihara Kan Takeda Hajime Sakuma 《Magnetic resonance imaging》2009
Purpose
The objective of this study is to determine regional left ventricle (LV) function and temporal heterogeneity of LV wall contraction by analyzing regional time–volume curve (TVC) after Fourier fitting and to assess altered systolic and diastolic functions and temporal indices of myocardial contraction in infarcted segments in comparison with noninfarcted myocardium in patients with myocardial infarction (MI).Methods
Steady-state cine magnetic resonance (MR) and late gadolinium-enhanced (LGE) MR images were acquired using a 1.5-T MR system in 60 patients with MI. Regional LV function was determined by analyzing regional TVC in 16 segments. The fitted regional TVC was generated by Fourier curve fitting with five harmonics. Regional LV ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), time to end-systole and time to peak filling (TPF) were determined from TVC and the first derivative curve.Results
On LGE MR imaging (MRI), MI was observed in 307 of 960 segments (32.0%). Regional EF and PER averaged in LGE segments were 49.3±14.5% and 2.83±0.65 end-diastolic volume (EDV)/s, significantly lower than those in normal segments (66.7±11.9% and 3.63±0.60 EDV/s, P<.001 and P<.01, respectively). In addition, regional PFR, an index of diastolic function, was significantly reduced in LGE segments (1.94±0.54 vs. 2.86±0.68 EDV/s, P<.01). Time to end-systole and TPF were significantly greater in LGE segments (380.2±57.6 and 169.3±45.4 ms) than in normal segments (300.9±55.1 and 132.3±43.0 ms, P<.01 and P<.01, respectively).Conclusions
Analysis of regional TVC on cine MRI after Fourier fitting allows quantitative assessment of regional systolic and diastolic LV functions and temporal heterogeneity of LV wall contraction in patients with MI. 相似文献97.
Suzuki S Yamamura M Shimada M Umezawa T 《Chemical communications (Cambridge, England)》2004,(24):2838-2839
An enzyme preparation from the cultured cells of Cryptomeria japonica catalyses the formation of a heartwood norlignan, (E)-hinokiresinol, from two distinct phenylpropanoid monomers: 4-coumaroyl CoA and 4-coumaryl alcohol, and from a dimer: 4-coumaryl 4-coumarate. 相似文献
98.
Toru Ohmoto Osamu Saeki Kazuhiro Sakuma 《Transactions of the American Mathematical Society》2003,355(9):3825-3838
Let be a generic smooth map with corank one singularities between manifolds, and let be the singular point set of . We define the self-intersection class of using an incident class introduced by Rimányi but with twisted coefficients, and give a formula for in terms of characteristic classes of the manifolds. We then apply the formula to the existence problem of fold maps.
99.
T. Imahoko K. Takasago M. Kamata J. Sakuma T. Sumiyoshi H. Sekita M. Obara 《Applied physics. B, Lasers and optics》2007,89(2-3):217-222
We have developed a pulsed Yb:YAG thin disk green laser for pumping a 100 kHz and 10 W femtosecond laser. We optimized numerically
and experimentally the open duration of the acousto-optic (AO) Q-switcher and the internal SHG method, generating stable output
energy at a 100 kHz repetition rate. We demonstrated a 515 nm output power of over 80 W with a pulse-to-pulse stability of
less than 1% RMS with an LD power to green power conversion efficiency of 24%. With the developed green laser, we obtained
16 W of a Ti:sapphire laser in a cavity dumped mode.
PACS 42.55.Xi; 42.60.Gd; 42.60.By; 42.65.-k; 42.65.Re 相似文献
100.
A spin current perpendicular to the electric current is investigated around a Landau level filling factor nu=3 in a GaAs/AlGaAs two-dimensional electron system. Measurements of dynamic nuclear polarization in the vicinity of the edge of a specially designed Hall bar sample indicate that the direction of the spin current with respect to the Hall electric field reverses its polarity at nu=3, where the dissipative current carried by holes in the spin up Landau level is replaced with that by electrons in the spin down Landau level. 相似文献