全文获取类型
收费全文 | 78篇 |
免费 | 3篇 |
专业分类
化学 | 64篇 |
数学 | 2篇 |
物理学 | 15篇 |
出版年
2021年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 8篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有81条查询结果,搜索用时 10 毫秒
1.
Birgitta Knopp Bernd Jung Franz-Josef Wortmann 《Macromolecular theory and simulations》1996,5(5):947-956
Molecular dynamic (MD) simulations based on two different force fields, CVFF and CFF91, were carried out in order to check their feasibility for the structural investigation of the wool intermediate filament (IF) monomeric unit. Selecting an ideal α-helix as start conformation, all MD-simulations with CVFF in vaccum show the α-helix to be unstable. Independently of the amino acid sequence of the α-helix, a new helical structure with a larger diameter arises during the MD-simulation, due to a shift of the intrahelical hydrogen bonds. However in simulations with surrounding water the α-helix remains stable throughout the simulations with the CVFF force field. In contrast to this, MD-simulations in vaccume based on the CFF91 force field are able to determine different stabilities for the α-helical start conformation of various IF-segments, that agree well with secondary structure predictions. The simulation results obtained with CFF91 in vacuum can like wise be verified using an explicit water environment. We found that higher partial charges attributed to the atoms of the amide groups that form the intrahelical hydrogen bonds are the reason for the superiority of the CFF91 force field. 相似文献
2.
We present a microscopic quantum theoretical analysis of the nanoscale superfluid properties of solvating clusters of para-H2 around the linear OCS molecule. Path-integral calculations with N=17 para-H2 molecules, constituting a full solvation shell, show the appearance of a significant superfluid response to rotation around the molecular axis at T=0.15 K. This low-temperature superfluid response is highly anisotropic and drops sharply as the temperature increases to T approximately 0.3 K. These calculations provide definitive theoretical evidence that an anisotropic superfluid state exists for molecular hydrogen in this microscopic solvation layer. 相似文献
3.
4.
We show that single electron tunneling devices such as the Cooper-pair box or double quantum dot can be sensitive to the zero-point fluctuation of a single trapping center hybridized with a Fermi sea. If the trap energy level is close to the Fermi sea and has linewidth gamma > k(B)T, its noise spectrum has an Ohmic Johnson-Nyquist form, whereas for gamma < k(B)T the noise has a Lorentzian form expected from the semiclassical limit. Trap levels above the Fermi level are shown to lead to steps in the noise spectrum that can be used to probe their energetics, allowing the identification of individual trapping centers coupled to the device. 相似文献
5.
Optimal construction of quantum operations is a fundamental problem in the realization of quantum computation. We here introduce a newly discovered quantum gate, B, that can implement any arbitrary two-qubit quantum operation with minimal number of both two- and single-qubit gates. We show this by giving an analytic circuit that implements a generic nonlocal two-qubit operation from just two applications of the B gate. Realization of the B gate is illustrated with an example of charge-coupled superconducting qubits for which the B gate is seen to be generated in shorter time than the CNOT gate. 相似文献
6.
7.
8.
Parthey CG Matveev A Alnis J Bernhardt B Beyer A Holzwarth R Maistrou A Pohl R Predehl K Udem T Wilken T Kolachevsky N Abgrall M Rovera D Salomon C Laurent P Hänsch TW 《Physical review letters》2011,107(20):203001
We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10) Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb. 相似文献
9.
Contribution of electron and confocal microscopy in the study of Leishmania-macrophage interactions.
Promastigotes of the protozoan parasite genus Leishmania are inoculated into a mammalian host when an infected sand fly takes a bloodmeal. Following their opsonization by complement, promastigotes are phagocytosed by macrophages. There, promastigotes differentiate into amastigotes, the form of the parasite that replicates in the phagolysosomal compartments of host macrophages. Although the mechanisms by which promastigotes survive the microbicidal consequence of phagocytosis remain, for the most part, to be elucidated, evidence indicates that glycoconjugates play a role in this process. One such glycoconjugate is lipophosphoglycan, an abundant promastigote surface glycolipid. Using quantitative electron and confocal laser scanning microscopy approaches, evidence was provided that L. donovani promastigotes inhibit phagolysosome biogenesis in a lipophosphoglycan-dependent manner. This inhibition correlates with an accumulation of periphagosomal F-actin, which may potentially form a physical barrier that prevents L. donovani promastigote-containing phagosomes from interacting with endocytic vacuoles. Inhibition of phagosome maturation may constitute a strategy to provide an environment propitious to the promastigote-to-amastigote differentiation. 相似文献
10.
We present a theoretical analysis of the electronic absorption spectra of tetracene in (4)He droplets based on many-body quantum simulations. Using the path integral ground state approach, we calculate one- and two-body reduced density matrices of the most strongly localized He atoms near the molecule surface and use these to investigate the helium ground-state quantum coherence and correlations when tetracene is in its electronic ground and excited states. We identify a trio of quasi-one-dimensional, strongly localized atoms adsorbed along the long axis of the molecule that show some quantum coherence among themselves but far less with the remaining solvating helium. We evaluate the single-particle natural orbitals of the localized He atoms by diagonalization of the one-body density matrix and use these to construct single- and many-particle solvating helium basis states with which the zero-phonon spectral features of the tetracene-(4)He(N) absorption spectrum are then calculated. The absorption spectrum resulting from the three-body density matrix for the strongly bound trio of helium atoms is in very good agreement with the experimental data, accounting quantitatively for the anomalous splitting of the zero-phonon line [Hartmann, M.; Lindinger, A.; Toennies, J. P.; Vilesov, A. F. Chem. Phys. 1998, 239, 139; Krasnokutski, S.; Rouillé, G.; Huisken, F. Chem. Phys. Lett. 2005, 406, 386]. Our results indicate that the combination of strong localization and the quasi-one-dimensional nature of trios of helium atoms adsorbed along the long axis of tetracene leads to a quantum coherent, yet highly correlated ground state for the helium density closest to the molecule. The spectroscopic analysis shows that this feature accounts quantitatively for the anomalous splittings and hitherto unexplained fine structure observed in the absorption spectra of tetracene and suggests that it may be responsible for the corresponding zero-phonon splittings in other quasi-one-dimensional planar aromatic molecules. 相似文献