全文获取类型
收费全文 | 22441篇 |
免费 | 178篇 |
国内免费 | 97篇 |
专业分类
化学 | 11823篇 |
晶体学 | 418篇 |
力学 | 622篇 |
综合类 | 7篇 |
数学 | 1912篇 |
物理学 | 7934篇 |
出版年
2016年 | 265篇 |
2015年 | 194篇 |
2014年 | 300篇 |
2013年 | 883篇 |
2012年 | 613篇 |
2011年 | 680篇 |
2010年 | 496篇 |
2009年 | 496篇 |
2008年 | 661篇 |
2007年 | 738篇 |
2006年 | 673篇 |
2005年 | 617篇 |
2004年 | 545篇 |
2003年 | 502篇 |
2002年 | 510篇 |
2001年 | 716篇 |
2000年 | 548篇 |
1999年 | 452篇 |
1998年 | 366篇 |
1997年 | 350篇 |
1996年 | 322篇 |
1995年 | 401篇 |
1994年 | 371篇 |
1993年 | 334篇 |
1992年 | 367篇 |
1991年 | 402篇 |
1990年 | 372篇 |
1989年 | 376篇 |
1988年 | 348篇 |
1987年 | 355篇 |
1986年 | 349篇 |
1985年 | 427篇 |
1984年 | 435篇 |
1983年 | 325篇 |
1982年 | 342篇 |
1981年 | 371篇 |
1980年 | 338篇 |
1979年 | 345篇 |
1978年 | 354篇 |
1977年 | 324篇 |
1976年 | 343篇 |
1975年 | 301篇 |
1974年 | 300篇 |
1973年 | 309篇 |
1972年 | 195篇 |
1969年 | 165篇 |
1968年 | 196篇 |
1967年 | 337篇 |
1966年 | 292篇 |
1962年 | 176篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
C. Mattea N. Fatkullin E. Fischer U. Beginn E. Anoardo M. Kroutieva R. Kimmich 《Applied magnetic resonance》2004,27(3-4):371-381
Linear polyethylene oxides with molecular weightsM w of 1665 and 10170 confined in pores with variable diameters in a solid methacrylate matrix were studied by proton field-cycling nuclear magnetic resonance relaxometry. The pore diameter was varied in the range of 9–57 nm. In all cases, the spin-lattice relaxation time shows a frequency dependence close toT 1∞ v3/4 in the range ofv=3·10?1-2·101 MHz as predicted by the tube-reptation model. This protonT 1 dispersion essentially reproduces that found in a previous deuteron study (R. Kimmich, R.-O. Seitter, U. Beginn, M. Möller, N. Fatkullin: Chem. Phys. Lett. 307, 147, 1999). As a feature particularly characteristic for reptation, this finding suggests that reptation is the dominating chain dynamics mechanism under pore confinement in the corresponding time range. The absolute values of the spin-lattice relaxation times indicate that the diameter of the effective tubes in which reptation occurs is much smaller than the pore diameters on the time scale of spin-lattice relaxation experimens. An estimation leads to a valued *~0.5 nm. The impenetrability of the solid pore walls, the uncrossability of polymer chains (“excluded volume”) and the low value of the compressibility in polymer melts create the “corset effect” which reduces the lateral motions of polymer chains to a microscopic scale of only a few tenths of a nanometer. 相似文献
22.
U.S. NaziaA.K.M.A. Islam 《Solid State Communications》2003,125(1):37-40
The Eliashberg spectral density function is constructed for the superconducting compound BaxK1−xBiO3 with x=0.5, 0.6, 0.7. The functions, besides yielding some prominent structures, show widely spreading spectra that inhibit lattice instability by yielding not too large values of λ(<1.32). The resulting spectral functions show similar shape as other results, where available, and also successfully reproduce the observed critical temperature, isotope exponent, gap ratio and several other parameters. 相似文献
23.
24.
N. U. Aldiyarov K. K. Kadyrzhanov E. M. Yakushev V. S. Zhdanov 《Hyperfine Interactions》2005,164(1-4):67-72
The conditions for achievement of high resolving power of depth selective conversion electron Mössbauer spectroscopy method at a combined installation ‘electron spectrometer–nuclear gamma-resonance spectrometer’ have been obtained. There has been made a considerable step in development of the method at its realization at a magnetic sector electron spectrometer with double focusing, equipped with electron source (a sample under investigation) of large-area and position-sensitive detector. The paper presents a prospective symmetrical version of a magnetic sector electron spectrometer that allows realizing more completely possibilities of the method. It is noted that the proposed method is particularly valuable for investigations of nanosystems, nanostrutures that contain Mössbauer nuclei. 相似文献
25.
26.
We study conditions on the matrix mask of a vector subdivision scheme ensuring that certain polynomial input vectors yield polynomial output again. The conditions are in terms of a recurrence formula for the vectors which determine the structure of polynomial input with this property. From this recurrence, we obtain an algorithm to determine polynomial input of maximal degree. The algorithm can be used in the design of masks to achieve a high order of polynomial reproduction. 相似文献
27.
W M Niessen M A de Kraa E R Verheij P J Bergers G F La Vos U R Tjaden J van der Greef 《Rapid communications in mass spectrometry : RCM》1989,3(1):1-4
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL. 相似文献
28.
The transverse momentum spectra for pions observed by WA80 and NA35 collaborations are analysed within a fireball model with collective isentropic expansion and a realistic freeze-out criterion. By varing the initial state of the fireball, an excellent fit to the data is achieved for the whole measured range ofP T . Slight differences in the data for the spectral slopes from central and pheripheral collisions originate in our model from the difference in the size of the fireball and in the number of participating nucleons in central and peripheral collisions. Using additional information from two-pion correlations, we can extrapolate our model back from the freeze-out point (determined from the spectra) to the initial state; we find that an initial energy density of 1.5–2GGeV/fm3 is sufficient to explain the data from central O+Au collisions at 200A GeV. 相似文献
29.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust. 相似文献
30.
G. Giardina G. Fazio A. Lamberto A. I. Muminov A. K. Nasirov U. T. Yakhshiev R. Palamara R. Ruggeri 《Acta Physica Hungarica A》2004,19(1-2):101-108
We study the effect of the entrance channel and the shell structure of reacting massive nuclei on the fusion mechanism and the formation of evaporation residues of heavy and superheavy nuclei. In the framework of the combined dinuclear system concept and advanced statistical model, we analyze the reactions 32S+182W, 48Ti+166Er and 60Ni+154Sm leading to 214Th*, and the reactions 48Ca+248Cm and the 48Ca+249Cf leading to the 296116 and 297118 compound nuclei, respectively. 相似文献