全文获取类型
收费全文 | 560篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 329篇 |
晶体学 | 2篇 |
力学 | 8篇 |
数学 | 102篇 |
物理学 | 127篇 |
出版年
2020年 | 9篇 |
2019年 | 6篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2013年 | 23篇 |
2012年 | 11篇 |
2011年 | 9篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 20篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1958年 | 5篇 |
1895年 | 5篇 |
1890年 | 6篇 |
1886年 | 10篇 |
1882年 | 9篇 |
排序方式: 共有568条查询结果,搜索用时 6 毫秒
61.
62.
O. Kaspar Personne Schneider W. Lenz und E. Kock 《Fresenius' Journal of Analytical Chemistry》1882,21(1):294-295
Ohne Zusammenfassung 相似文献
63.
The van Cittert-Zernike theorem of classical optics is generalized to the situation of matter-wave optics. Applying a Green's function method the first- and second-order correlation functions of the matter field emitted from an incoherent source are calculated, and the results are compared to the case of electromagnetic waves. 相似文献
64.
We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux
lines in low T
c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line
lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends
to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the
destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has
employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo
technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing
μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation
of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors. 相似文献
65.
Leop Lenz 《Fresenius' Journal of Analytical Chemistry》1889,28(1):441-443
Ohne Zusammenfassung 相似文献
66.
Lars Lauterbach Hongxin Wang Marius Horch Leland B. Gee Yoshitaka Yoda Yoshihito Tanaka Ingo Zebger Oliver Lenz Stephen P. Cramer 《Chemical science》2015,6(2):1055-1060
Hydrogenases are complex metalloenzymes that catalyze the reversible splitting of molecular hydrogen into protons and electrons essentially without overpotential. The NAD+-reducing soluble hydrogenase (SH) from Ralstonia eutropha is capable of H2 conversion even in the presence of usually toxic dioxygen. The molecular details of the underlying reactions are largely unknown, mainly because of limited knowledge of the structure and function of the various metal cofactors present in the enzyme. Here, all iron-containing cofactors of the SH were investigated by 57Fe specific nuclear resonance vibrational spectroscopy (NRVS). Our data provide experimental evidence for one [2Fe2S] center and four [4Fe4S] clusters, which is consistent with the amino acid sequence composition. Only the [2Fe2S] cluster and one of the four [4Fe4S] clusters were reduced upon incubation of the SH with NADH. This finding explains the discrepancy between the large number of FeS clusters and the small amount of FeS cluster-related signals as detected by electron paramagnetic resonance spectroscopic analysis of several NAD+-reducing hydrogenases. For the first time, Fe–CO and Fe–CN modes derived from the [NiFe] active site could be distinguished by NRVS through selective 13C labeling of the CO ligand. This strategy also revealed the molecular coordinates that dominate the individual Fe–CO modes. The present approach explores the complex vibrational signature of the Fe–S clusters and the hydrogenase active site, thereby showing that NRVS represents a powerful tool for the elucidation of complex biocatalysts containing multiple cofactors. 相似文献
67.
Our work presents extensions of multi layered composite sphere models known from the literature to temperature-dependent elastic effects accompanied by curing. In particular, volumetric effective properties are obtained by homogenization for a representative unit cell (micro-RVE) on the heterogeneous microscale for thermo-chemo-mechanical coupling within linear elasticity. To this end, an analytical solution for an n-layered composite sphere model is derived. In a numerical study for a (3)-phase matrix it is demonstrated that the effective elastic and thermal properties lie within Voigt and Reuss bounds, whilst for the chemical part of the model an analogous result is obtained for the effective strains. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
68.
The water adsorption capacity of a dough consisting of wheat flour was increased linearly by the addition of water-insoluble hemicelluloses (xylane, mannane etc.) extracted from beech-wood pulp using soda lye (a by-product of viscose fiber production). The investigation of this finding by viscosity measurements revealed two reasons for the higher water uptake: 1) a higher kneading resistance of the dough, and 2) a gel-regeneration of the kneaded dough during the dough-rest.
Herrn Prof. Dr. Josef Schurz zum 60. Geburtstag gewidmet. 相似文献
69.
Methane hydrates with the three clathrate structures I, II, and H are studied by quantum-chemical methods. Hybrid density-functional theory B3LYP computations using periodic boundary conditions are combined with force-field methods for the thermal energy effects to calculate energetic, thermodynamic, and structural properties. The pressure dependencies for the crystal structures, lattice energies, and guest molecule interactions are derived. The quantum-chemical geometry optimizations predict too small cell volumes as compared to experimental data, but by including zero-point energy and thermal energy effects, we find the cell volumes increase and the correct densities are obtained. The phase transition from MH-I to ice Ih and methane was computed and found to occur at about 9.7 MPa. 相似文献
70.
A FLUORESCENCE IMAGING DEVICE FOR ENDOSCOPIC DETECTION OF EARLY STAGE CANCER – INSTRUMENTAL and EXPERIMENTAL STUDIES 总被引:1,自引:0,他引:1
R. Baumgartner H. Fisslinger D. Jocham H. Lenz L. Ruprecht H. Stepp E. Unsold 《Photochemistry and photobiology》1987,46(5):759-763
Abstract Visible detection of early stage cancer labelled with the fluorescing porphyrin mixture of dihematoporphyrin-ether and dihematoporphyrin-ester (DHE) is often limited by a high and inhomogeneously distributed level of autofluorescence. A new imaging method for reducing autofluo-rescence is described. The method uses alternating fluorescence excitation with laser light in the violet and blue spectral ranges. Subtraction of the corresponding fluorescence images results in contrast enhancement due to an effective reduction in the autofluorescence contribution. A prototype version of a highly sensitive fluorescence imaging device including a modified krypton ion laser, an image-intensified solid-state TV-camera, a digital image-processing system, and video recording and monitoring has been developed.
Experiments performed with this fluorescence imaging system on a tumorous dog bladder showed that a dose of 0.2 mg DHE kg−1 body wt, which is far below the dose administered for photodynamic therapy (2-5 mg kg− 'body wt), is sufficient to give a high-contrast fluorescence image. The corresponding excitation power density was about 1 W m−2 . Photobleaching of DHE was observed during fluorescence detection at excitation power densities exceeding 1 kW m−2 . At these high excitation levels DHE fades out nearly completely within 0.25 min. 相似文献
Experiments performed with this fluorescence imaging system on a tumorous dog bladder showed that a dose of 0.2 mg DHE kg