全文获取类型
收费全文 | 419篇 |
免费 | 11篇 |
专业分类
化学 | 250篇 |
晶体学 | 4篇 |
力学 | 7篇 |
数学 | 18篇 |
物理学 | 151篇 |
出版年
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 18篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 27篇 |
2002年 | 13篇 |
2001年 | 23篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1968年 | 2篇 |
1939年 | 2篇 |
1931年 | 3篇 |
1926年 | 2篇 |
1924年 | 4篇 |
1922年 | 2篇 |
1921年 | 2篇 |
1919年 | 2篇 |
1917年 | 3篇 |
1916年 | 2篇 |
1915年 | 2篇 |
排序方式: 共有430条查询结果,搜索用时 406 毫秒
31.
32.
33.
34.
35.
Cyclometalated Iridium(III) and Rhodium(III) Complexes Containing Naphthyridine Ligands: Synthesis,Characterization and Biological Studies 下载免费PDF全文
The synthesis, crystal structure, and biological activity of new bis‐cyclometalated compounds [M(ptpy)2(4‐chloro‐2‐methyl‐1,8‐naphthyridine)]PF6 [M = Rh ( 1 ); M = Ir ( 2 ); ptpy = 2‐(p‐tolyl)pyridinato] and [M(ptpy)2(2‐methyl‐1,8‐naphthyridine)]PF6 [M = Rh ( 3 ); M = Ir ( 4 )] are described. The new compounds were prepared by the reaction of [{M(μ‐Cl)(ptpy)2}2] (M = Rh, Ir) with the corresponding naphthyridine ligands. The molecular structures of compounds 1 , 3 , and 4 were confirmed by single‐crystal X‐ray diffraction studies. 相似文献
36.
Thorsten Perl Bertram Bödeker Melanie Jünger Jürgen Nolte Wolfgang Vautz 《Analytical and bioanalytical chemistry》2010,397(6):2385-2394
Multicapillary column (MCC) ion mobility spectrometers (IMS) are increasingly in demand for medical diagnosis, biological
applications and process control. In a MCC-IMS, volatile compounds are differentiated by specific retention time and ion mobility
when rapid preseparation techniques are applied, e.g. for the analysis of complex and humid samples. Therefore, high accuracy
in the determination of both parameters is required for reliable identification of the signals. The retention time in the
MCC is the subject of the present investigation because, for such columns, small deviations in temperature and flow velocity
may cause significant changes in retention time. Therefore, a universal correction procedure would be a helpful tool to increase
the accuracy of the data obtained from a gas-chromatographic preseparation. Although the effect of the carrier gas flow velocity
and temperature on retention time is not linear, it could be demonstrated that a linear alignment can compensate for the changes
in retention time due to common minor deviations of both the carrier gas flow velocity and the column temperature around the
MCC-IMS standard operation conditions. Therefore, an effective linear alignment procedure for the correction of those deviations
has been developed from the analyses of defined gas mixtures under various experimental conditions. This procedure was then
applied to data sets generated from real breath analyses obtained in clinical studies using different instruments at different
measuring sites for validation. The variation in the retention time of known signals, especially for compounds with higher
retention times, was significantly improved. The alignment of the retention time—an indispensable procedure to achieve a more
precise identification of analytes—using the proposed method reduces the random error caused by small accidental deviations
in column temperature and flow velocity significantly. 相似文献
37.
We realize experimentally a true reflectionless potential, which facilitates nonresonant unity transmission for all incident waves and at the same time supports localized modes. We utilize arrays of evanescently coupled optical waveguides, where a particular modulation of the transverse waveguide separations provides a physical realization of reflectionless Ablowitz-Ladik soliton potentials. 相似文献
38.
Keil R Perez-Leija A Dreisow F Heinrich M Moya-Cessa H Nolte S Christodoulides DN Szameit A 《Physical review letters》2011,107(10):103601
Coherent states and their generalizations, displaced Fock states, are of fundamental importance to quantum optics. Here we present a direct observation of a classical analogue for the emergence of these states from the eigenstates of the harmonic oscillator. To this end, the light propagation in a Glauber-Fock waveguide lattice serves as equivalent for the displacement of Fock states in phase space. Theoretical calculations and analogue classical experiments show that the square-root distribution of the coupling parameter in such lattices supports a new family of intriguing quantum correlations not encountered in uniform arrays. Because of the broken shift invariance of the lattice, these correlations strongly depend on the transverse position. Consequently, quantum random walks with this extra degree of freedom may be realized in Glauber-Fock lattices. 相似文献
39.
Andreas Schwenke Philipp Wagener Stefan Nolte Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2011,104(1):77-82
The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied
during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary
liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed
nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser
wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease
of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental
wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without
plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by
Mie-scattering of dispersed nanoparticle clusters. 相似文献
40.
S. D?ring S. Richter A. Tünnermann S. Nolte 《Applied Physics A: Materials Science & Processing》2011,105(1):69-74
We report on the temporal evolution of the percussion drilling process in deep laser drilling. Ultrashort laser pulses at
1030 nm and a duration of 8 ps were used to machine silicon while simultaneously imaging the silhouette of the hole using
an illumination wavelength above the band edge. We investigate the influence of the processing parameters fluence and pulse
energy on the depth and shape of the hole demonstrating different phases of the drilling process. In the first phase, a tapered
hole is formed with highly reproducible shape and depth. In the following, the evolution of the hole shape is irregular and
imperfections like bulges, changes of the drilling direction and the formation of multiple hole ends occur. In the final phase,
the maximum depth stays constant while the volume still increases due to enlargement of the hole diameter and the possible
formation of multiple hole ends. Deviations from the ideal hole shape occur primarily in the lower part of the hole. Their
extent can be reduced by increasing the amount of applied pulse energy. Moreover, the pulse energy is chiefly determining
the maximum achievable hole depth, which is largely independent of the focusing conditions and corresponding fluence. 相似文献