全文获取类型
收费全文 | 667篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 399篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 51篇 |
物理学 | 215篇 |
出版年
2020年 | 5篇 |
2019年 | 5篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2014年 | 6篇 |
2013年 | 16篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 24篇 |
2005年 | 18篇 |
2004年 | 20篇 |
2003年 | 12篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 20篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 15篇 |
1972年 | 6篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1894年 | 5篇 |
排序方式: 共有676条查询结果,搜索用时 15 毫秒
511.
For the solvolysis of Co(4-t-Bupy)4Cl2? ions in water + methanol and water + ethanol, log (rate constant) does not vary linearly with the reciprocal of the dielectric constant. The Gibbs free energy, the enthalpy, and the entropy of activation are insensitive to changes in the solvent composition in these mixtures, although a slight broad maximum in ΔH* and ΔS* probably exists at mole fractions of about 0.2 in water + ethanol. This contrasts with the extrema in ΔH* and ΔS* found with more hydrophobic alcohols used as cosolvents. However, the application of a Gibbs energy cycle to the solvolysis in water and in the mixtures shows that there is a differential effect of changes in solvent structure on the emergent solvated CoIII cation in the transition state and on Co(4-t-Bupy)4Cl2+ in the initial state. The stability of the former increases relative to that of the latter as the cosolvent content of the mixture rises. © 1995 John Wiley & Sons, Inc. 相似文献
512.
B. Foster P. Grossmann P.R. Lamb W.L. McDowell J. Wells R. Blokzijl G.F. Wolters R. Armenteros C. Dionisi Ph. Gavillet P.F. Loverre M. Mazzucato J.J. Engelen W. Kittel J.S.M. Vergeest R.T. Van De Walle 《Nuclear Physics B》1981,187(2):231-253
We report on the results of a partial-wave analysis of the 3π system produced by baryon exchange in the reaction K?p→Σ?π+π+π? at 4.2 GeV/c. We confirm the existence of an enhancement in the 1+S(?π) wave as previously established from a Dalitz plot analysis of the same data. The phase variation of this wave is found to be consistent with that expected for a resonance and thus the enhancement is identified with A1 production. No clear signal for this state is found in either the reaction K?p→Σ+π+π+π?π? or K?p→Λπ+π?π0. We also find production via baryon exchange of the A2 in all three reactions and the ω and (1975) in the third reaction. 相似文献
513.
514.
515.
516.
Ionization of atoms by the spatial gradient of the pondermotive potential in a focused laser beam is investigated. Rydberg ions, formed during the interaction of noble gas atoms with an intense laser pulse, are used to probe the gradient field. Rydberg ion species with higher ionization potentials are produced at locations where the gradient field is largest. The measured Rydberg ion yields differ dramatically from estimates that ignore gradient-field ionization, but are in good agreement with predictions that include the effect. 相似文献
517.
D.E. Wells 《Journal of chromatography. A》1980,190(2):504-505
518.
The chemical shifts and coupling constants for the ring protons of nine disubstituted naphthalenes (mainly halogenonitre compounds) in carbon tetrachloride solutions have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Substituent effects are essentially additive except when a strong π-donor group is in direct conjugation with a strong π-acceptor group. 相似文献
519.
Ikhsan J Angove MJ Wells JD Johnson BB 《Journal of colloid and interface science》2005,284(2):383-392
The sorption of 2-, 3-, and 4-aminopyridine on K-saturated Wyoming (SWy-K) and Texas (STx-K) and Ca-enriched Texas (STx-Ca) montmorillonite was measured at 25 degrees C with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as the background electrolyte. The aminopyridines adsorbed to montmorillonite at low pH, but not at high pH. Extended constant capacitance surface complexation models (ECCMs) and attenuated total reflectance-FTIR data indicate that aminopyridines sorb to the silica-like faces by cation exchange, forming outer-sphere complexes between aminopyridinium ions and permanent negatively charged surface sites (X(-)). X-ray diffraction data and sorption kinetics suggest that sorption occurs not only at external X(-) sites but also at those in the interlayer spaces. Differences in the sorption behaviors of 2-, 3-, and 4-aminopyridine result from differences in their pK(a)s. The extent of sorption of aminopyridines by the montmorillonite samples (SWy-K>STx-K>STx-Ca) results from the higher cation-exchange capacity of SWy-K, and from the fact that Ca(2+) is much more effective than K(+) in competing with protonated aminopyridines for the X(-) sites. 相似文献
520.
Yusof ZM Wells BO Valla T Fedorov AV Johnson PD Li Q Kendziora C Jian S Hinks DG 《Physical review letters》2002,88(16):167006
Results from the study of a highly overdoped (OD) Bi(2)Sr(2)CaCu(2)O(8+delta) with a T(c) = 51 K using angle-resolved photoemission spectroscopy are presented. We observe a sharp peak in the spectra near ( pi,0) that persists well above T(c), a nodal self-energy which approaches that seen for the Mo(110) surface state, and a more k-independent line shape at the Fermi surface than the lower-doped cuprates. This allows for a realistic comparison of the lifetime values to the experimental resistivity measurements. These observations point to the validity of the quasiparticle picture for the OD even in the normal state. 相似文献