全文获取类型
收费全文 | 293篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 125篇 |
力学 | 10篇 |
数学 | 83篇 |
物理学 | 80篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 7篇 |
2013年 | 43篇 |
2012年 | 11篇 |
2011年 | 18篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1965年 | 2篇 |
1943年 | 2篇 |
1940年 | 2篇 |
1933年 | 2篇 |
1918年 | 2篇 |
1916年 | 1篇 |
1902年 | 1篇 |
1898年 | 1篇 |
1893年 | 1篇 |
排序方式: 共有298条查询结果,搜索用时 484 毫秒
61.
Coarse-grained (lattice-) models have a long tradition in aiding efforts to decipher the physical or biological complexity of proteins. Despite the simplicity of these models, however, numerical simulations are often computationally very demanding and the quest for efficient algorithms is as old as the models themselves. Expanding on our previous work [T. Wu?st and D. P. Landau, Phys. Rev. Lett. 102, 178101 (2009)], we present a complete picture of a Monte Carlo method based on Wang-Landau sampling in combination with efficient trial moves (pull, bond-rebridging, and pivot moves) which is particularly suited to the study of models such as the hydrophobic-polar (HP) lattice model of protein folding. With this generic and fully blind Monte Carlo procedure, all currently known putative ground states for the most difficult benchmark HP sequences could be found. For most sequences we could also determine the entire energy density of states and, together with suitably designed structural observables, explore the thermodynamics and intricate folding behavior in the virtually inaccessible low-temperature regime. We analyze the differences between random and protein-like heteropolymers for sequence lengths up to 500 residues. Our approach is powerful both in terms of robustness and speed, yet flexible and simple enough for the study of many related problems in protein folding. 相似文献
62.
Mass spectra were recorded for one-colour resonance enhanced multiphoton ionization (REMPI) of H(i)Br (i = 79, 81) for the two-photon resonance excitation region 79,040-80,300 cm(-1) to obtain two-dimensional REMPI data. The data were analysed in terms of rotational line positions, intensities, and line-widths. Quantitative analysis of the data relevant to near-resonance interactions between the F(1)Δ(2)(v' = 1) and V(1)Σ(+)(v' = m + 7) states gives interaction strengths, fractional state mixing, and parameters relevant to dissociation of the F state. Qualitative analysis further reveals the nature of state interactions between ion-pair states and the E(1)Σ(+) (v' = 1) and H(1)Σ(+)(v' = 0) Rydberg states in terms of relative strengths and J' dependences. Large variety in line-widths, depending on electronic states and J' quantum numbers, is indicative of number of different predissociation channels. The relationship between line-widths, line-shifts, and signal intensities reveals dissociation mechanisms involving ion-pair to Rydberg state interactions prior to direct or indirect predissociations of Rydberg states. Quantum interference effects are found to be important. Moreover, observed bromine atom (2 + 1) REMPI signals support the importance of Rydberg state predissociation channels. A band system, not previously observed in REMPI, was observed and assigned to the k(3)Π(0)(v' = 0) ←← X transition with band origin 80,038 cm(-1) and rotational parameter B(v('))=7.238 cm(-1). 相似文献
63.
L. Reeve T. Swinden W. W. Stevenson G. E. Speight H. A. Sloman F. Willems N. Gray M. C. Sanders S. N. Schkotowa H. Kempf K. Abresch G. J. Weinberg R. Stumper P. Mettelock F. Wüst J. Duhr P. Klinger W. Koch H. Schottky H. Hiltenkamp H. J. Wiester I. Wada und R. Ishii 《Fresenius' Journal of Analytical Chemistry》1943,126(10):385-390
Ohne Zusammenfassung 相似文献
64.
65.
66.
This work presents an attempt to define the qualitative and quantitative changes in microstructural parameters of Fe-Cr-Co alloy microstructure depending on the parameters of heat isothermal high-temperature aging and magnetic treatments. Two alloys of nominally similar Cr and Co contents, but containing differing impurities, were tested for the determination of the influence of impurities on the values of Br, Hc and (BH)max. High-temperature aging was carried out by two methods: (i) an isothermal process and (ii) continuous cooling in an external magnetic field; values of their magnetic properties were compared. Changes in particle size of the ferromagnetic phase 1 as well as its surface content, specific surface and structure anisotropy coefficient were defined for the material as function of the temperature of isothermal high-temperature aging. The results obtained enabled discussion of individual influence of microstructural parameters during magnetic hardening of Fe-Cr-Co type alloys. Results from TEM examinations show that microstructural parameters are sensitive functions of isothermal heat-magnetic treatment and in this process a very precise control of its parameters is required. On the grounds of investigations performed, magnetic aging with continuous cooling is found to be the most favourable treatment, since owing to the wider range of the admissible parameters of treatment it allows for higher tolerance as regards the technological parameters. 相似文献
67.
Employing a pairing-plus-quadrupole interaction hamiltonian and projecting out good angular momentum states from the cranked Hartree-Fock-Bogoliubov (CHFB) intrinsic wave functions the yrast spectra of 158Dy and 168Yb are calculated up to moderately high spins (Imax = 16) as to include the backbending region. Then the variation of pairing correlation, g-factor and rotational alignment of neutron spin as a function of total angular momentum is studied. The effect of particle number projection on the spin-projected CHFB wave functions is also investigated and is found to be unimportant for the calculation of g-factors. On the other hand, corrections of the excitation energies for number fluctuations in the CHFB wave functions are essential. Furthermore, looking at the distribution of the total projection quantum number K in various cranking wave functions we are able to throw some light on the K ≠ 0 nature of the aligned s-band.A variation-after-spin projection calculation strictly for the axial shape, without cranking, is also carried out for both the nuclei considered here. In the low-spin region this numerically “cheaper” scheme produces energy spectra similar to that of the CHFB method, and may thus be used to readjust the interaction parameters. 相似文献
68.
Summary LetT()=+F() be a transformation from the Wiener space to itself with the range ofF() assumed to be in the Cameron-Martin space. The absolute continuity and the density function associated withT is considered;T is assumed to be embedded in or defined through a parameterizationT
t
=+F
t
() andF
t
is assumed to be differentiable int. The paper deals first with the case where the range of thet-derivative ofF
t
() is also in the Cameron-Martin space and new representations for the Radon-Nikodym derivative and the Carleman-Fredholm determinant are derived. The case where thet-derivative ofF
t
is not in the Cameron-Martin space is considered next and results on the absolute continuity and the density function, under conditions which are considerably weaker than previously known conditions, are presented.The work of the second author was supported by the fund for promotion of research at the Technion 相似文献
69.
New multivariate approaches have been applied to high-performance liquid chromatography (HPLC) with multiwavelength photodiode-array (PDA) detection. Multivariate calibration techniques such as partial least squares (PLS), principal component regression (PCR), classical least squares (CLS), and inverse least squares (ILS) was subjected to HPLC data for simultaneous quantitative analysis of synthetic binary mixtures and a commercial tablet formulation containing hydrochlorothiazide (HCT) and losartan potassium (LST). The combined use of HPLC and multivariate calibrations has been denoted HPLC–CLS, HPLC–ILS, HPLC–PCR, and HPLC–PLS. Successful chromatographic separation of the two active compounds and enalapril maleate, used as internal standard (IS), was accomplished by means of a 4.6 mm i.d. × 250 mm, 5 m particle, Waters Symmetry C18 reversed-phase column and a mobile phase consisting of 60:40 acetate buffer (0.2 M, pH 4.8)–acetonitrile (v/v, 60:40). HPLC data based on the ratio of analyte peak areas to IS peak area were obtained by PDA detection at five-wavelengths (250, 255, 260, 265, and 270 nm). The HPLC–CLS, HPLC–ILS, HPLC–PCR, and HPLC–PLS calibration plots for hydrochlorothiazide and losartan potassium were constructed separately by using the peak-area ratios corresponding to the concentrations of each active compound. The HPLC multivariate calibrations obtained were tested for different synthetic mixtures containing HCT and LST in the presence of the IS. These multivariate chromatographic methods were also applied to a commercial pharmaceutical dosage form containing HCT and LST. The results obtained from the multivariate calibrations were compared with those obtained by use of another, classical HPLC method using single-wavelength detection.Revised: 29 September 2004 and 4 January 2005 相似文献
70.
Complex formation parameters of macrotetrolide antibiotics with alkali and alkaline earth metal cations are given. The stability constants for the complexes in methanol and ethanol at 30°, as determined by vapour pressure osmometry, and ΔH0, ΔG0, and ΔS0 for some interactions in methanol and ethanol at 25°, measured by microcalorimetry, are compared and discussed. 相似文献