全文获取类型
收费全文 | 471篇 |
免费 | 6篇 |
专业分类
化学 | 307篇 |
晶体学 | 1篇 |
力学 | 13篇 |
数学 | 38篇 |
物理学 | 118篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 15篇 |
2011年 | 41篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 30篇 |
2007年 | 49篇 |
2006年 | 30篇 |
2005年 | 33篇 |
2004年 | 21篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1924年 | 1篇 |
排序方式: 共有477条查询结果,搜索用时 0 毫秒
81.
A nanoscale
multivalent platinum drug based on a poly(amidoamine) [PAMAM] dendrimer (generation
4.5, carboxylate surface) has been synthesized and fully characterized using
a variety of spectroscopic, chromatographic and thermal methods. Treatment
of the dendrimer with an aqueous solution containing an excess diaquo(cis-1,2-diaminocyclohexane)platinum(II) produces
a conjugate containing approximately forty (diaminocyclohexane)platinum(II)
moieties at the surface of the dendrimer. This material undergoes smooth two-stage
thermal decomposition to provide residual platinum oxide reflecting the platinum
loading in the drug. 相似文献
82.
83.
Andrew D. Burnett Dr. John Kendrick Dr. John E. Cunningham Dr. Michael D. Hargreaves Dr. Tasmin Munshi Dr. Howell G. M. Edwards Prof. Edmund H. Linfield Prof. A. Giles Davies Prof. 《Chemphyschem》2010,11(2):368-378
The terahertz frequency spectrum of pentaerythritol tetranitrate (PETN) is calculated using Discover 1 with the COMPASS 2 force field, CASTEP[3] and PWscf. 4 The calculations are compared to each other and to terahertz spectra (0.3–3 THz) of crystalline PETN recorded at 4 K. A number of analysis methods are used to characterise the calculated normal modes. 相似文献
84.
D P Egolf H C Howell K A Weaver D S Barker 《The Journal of the Acoustical Society of America》1985,78(5):1578-1587
Acoustic feedback in hearing aids has received little attention in the literature. Feedback occurs when stability conditions of the open-loop transfer function of an in situ hearing aid are violated. Solving the feedback problem will first require knowledge of the open-loop transfer function. Included in the open-loop transfer function is the acoustical path by which sound emanating from the earmold vent returns to the microphone (i.e., the feedback path). Reported herein are two different mathematical procedures for simulating transfer functions of the feedback path of an eyeglass-type hearing aid. In one procedure the vent exit was modeled as a point source of sound located on a flat plane, while it was treated as a point source on a sphere in the other. Results of laboratory experiments indicate that the mathematical models accurately predict those acoustic phenomena for which they were intended: point sources on plane and spherical baffles. Results of manikin experiments showed both models to be less accurate for simulating the feedback path around the human head. The maximum difference between experiment and theory was 6 dB at one frequency. Surprisingly, the flat-baffle model produced better agreement with experimental results than did the sphere model. 相似文献
85.
A.I. Shestakov J.A. Greenough L.H. Howell 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,90(1):1-28
We develop a scheme for the system coupling the radiation diffusion and matter energy balance equations. The method is based on fully implicit, first-order, backward Euler differencing; Picard-Newton iterations solve the nonlinear system. We show that iterating on the radiation energy density and the emission source is more robust. Since the Picard-Newton scheme may not converge for all initial conditions and time steps, pseudo-transient continuation (Ψtc) is introduced. The combined Ψtc-Picard-Newton scheme is analyzed. We derive conditions on the Ψtc parameter that guarantee physically meaningful iterates, e.g., positive energies. Successive Ψtc iterates are bounded and the radiation energy density and emission source tend to equilibrate. The scheme is incorporated into a multiply dimensioned, massively parallel, Eulerian, radiation-hydrodynamic computer program with automatic mesh refinement (AMR). Three examples are presented that exemplify the scheme's performance. (1) The Pomraning test problem that models radiation flow into cold matter. (2) A similar, but more realistic problem simulating the propagation of an ionization front into tenuous hydrogen gas with a Saha model for the equation-of-state. (3) A 2D axisymmetric (R,Z) simulation with real materials featuring jetting, radiatively driven, interacting shocks. 相似文献
86.
N. Howell Furman W. Le Roy Mc Cay A. Kling A. Lassieur F. Ibbotson L. Aitchison C. S. Marvel und O. Kamm 《Fresenius' Journal of Analytical Chemistry》1924,65(3-4):153-155
Ohne Zusammenfassung 相似文献
87.
88.
Absorption and emission spectra at room temperature and emission spectra atliquid nitrogen temperature are reported for thin solid films of free base octaethylporphin. The room temperature visible absorption spectrum resembles that of the solution, except all four peaks show a red shift of ≈ 12 nm and all except the farthest red are broadened. The Soret band in the near UV is greatly broadened in the film, and its peak absorbance is substantially reduced. The room-temperature emission of the films is quite similar to that of solution fluorescence, except for a red-shift of ≈ 10 nm. But at low temperature two new peaks appear at 657 and 672 nm. Their intensity as a function of temperature can be explained by a simple exciton trapping model. 相似文献
89.
In a previous paper, which appeared in two parts, Algorithm I was described. (See [1] and [2] for details). Algorithm II differs from Algorithm I in that the Chinese Remainder Theorem is not used whenever it is necessary to reconstruct a unique integer from its residue representation. Instead, the residue representation is converted to asymmetric residue representation and then the symmetric residue representation is converted to its associatedsymmetric mixed-radix representation, from which the unique integer can be reconstructed in an easy manner. This procedure has advantages over the procedure using the Chinese Remainder Theorem. 相似文献
90.