全文获取类型
收费全文 | 1210篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
化学 | 810篇 |
晶体学 | 4篇 |
力学 | 55篇 |
数学 | 177篇 |
物理学 | 199篇 |
出版年
2023年 | 10篇 |
2022年 | 34篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 46篇 |
2015年 | 35篇 |
2014年 | 30篇 |
2013年 | 77篇 |
2012年 | 66篇 |
2011年 | 78篇 |
2010年 | 48篇 |
2009年 | 43篇 |
2008年 | 67篇 |
2007年 | 67篇 |
2006年 | 70篇 |
2005年 | 57篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 42篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1974年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有1245条查询结果,搜索用时 15 毫秒
61.
Navakhun K Gale PA Camiolo S Light ME Hursthouse MB 《Chemical communications (Cambridge, England)》2002,(18):2084-2085
The propensity of amine, ammonium and amide pendant arm 2,5-diamidopyrrole derivatives to act as anion receptors has been investigated; the anion-coordination ability of these species has been determined by 1H NMR titration techniques revealing a marked selectivity of the amine functionalised receptor for hydrogen sulfate anions. 相似文献
62.
A novel 2:1 (permethylated-beta-cyclodextrin)-fullerene conjugate has been synthesised; highly soluble in cold water with formation of aggregates, it displays a negative solubility coefficient and has a partition coefficient between octanol and water (Log P = 1.58) in the suitable range for biological studies. 相似文献
63.
We study clusters formed by water molecules possessing large enough tetrahedrality with respect to their nearest neighbors. Using Monte Carlo simulation of SPC/E water and Voronoi tessellation, we find that regions of lower density than the bulk are formed by accretion of molecules into clusters exceeding a minimum size. Clusters are predominantly linear objects and become less compact as they grow until they reach a size beyond which further accretion is not accompanied by a density decrease. The results suggest that the formation of "icelike" regions in liquid water is cooperative. 相似文献
64.
Salvatore Sessa 《Fuzzy Sets and Systems》1984,13(1):95-100
In this communication, we explicitly point out that the principal results of Liu 1982 basically deduced from the definition of binary operation ° on the set F(X) of all fuzzy subsets of X, also hold if one uses the weaker definition of product under triangular norm °t. Fuzzy ideals with respect to the triangular norms are also defined. 相似文献
65.
Alberto Andreussi Lucio Bianco Salvatore Ricciardelli 《European Journal of Operational Research》1981,8(4):345-354
The objective of this study is the development of a simulation model to assist in aircraft sequencing operations in the terminal area. After the definition of the main characteristics of the model, a general structure of a terminal area is considered with a variable number of feeder fixes and alternative paths from the fixes to the runways. The model is designed so as to evaluate different operating policies. A discrete events simulation philosophy, using Fortran as simulation language, is employed. Finally a model application to the Rome terminal area is illustrated. The results obtained show that the model, here presented, is general enough to simulate the terminal area behaviour of any airport. 相似文献
66.
Salvatore Pignataro Giovanni Marletta Orazio Puglisi Umberto Costantino Giulio Alberti 《Journal of Electron Spectroscopy and Related Phenomena》1982,25(1):49-57
Mg Kα ESCA spectra of several α-Zr(PO4)2M2 compounds (M = Li+, Na+, K+, Cs+) have been obtained. Satellite structure is observed at ~7–8 eV from the main P 2s peak (corresponding to ~15–16 eV from the main Zr 3d peak). The intensity of the satellite depends on the counter-ion intercalated. For a given counter-ion it is strongly increased by sputtering, the rate of increase being also dependent on the counter-ion. This observation is interpreted mainly in terms of electron-defect formation similar to that involved in the formation of colour centres by radiation damage, and subsequent charge-transfer shake-up of the trapped electrons to the electron-deficient phosphorus or Zr(IV) centres. 相似文献
67.
Carlo Anchisi Luciana Corda Antonio Maccioni Gianni Podda Salvatore Cabiddu 《Journal of heterocyclic chemistry》1977,14(8):1331-1336
The preparation and reaction of 1,3,2-benzodioxa- and 1,3,2-benzoxathiarsoles (IIa-b) are described. Spiran derivatives Va-c are obtained by treating IIa-b with Ia-b and triethylamine, while the reaction of IIa-b with sodium hydroxide, ethoxide and p-cresolate gives the compounds VIa-b, VIIa-b and VIIIa-b, that can evolve to Xa-b. Reaction of IIa-b with sodium p-toluenethio-late and n-butyllithium gave the compounds IXa-b and XIa-b respectively. The structure of the prepared compounds has been determined by elemental analysis and spectroscopic data. 相似文献
68.
69.
70.
Salvatore?AntociEmail author Dierck-Ekkehard?Liebscher Luigi?Mihich 《General Relativity and Gravitation》2005,37(7):1191-1203
When sources are added at their right-hand sides, and g(ik) is a priori assumed to be the metric, the equations of Einstein’s Hermitian theory of relativity were shown to allow for an exact solution that describes the general electrostatic field of n point charges. Moreover, the injunction of spherical symmetry of g(ik) in the infinitesimal neighbourhood of each of the charges was proved to yield the equilibrium conditions of the n charges in keeping with ordinary electrostatics. The tensor g(ik), however, cannot be the metric of the theory, since it enters neither the eikonal equation nor the equation of motion of uncharged test particles. A physically correct metric that rules both the behaviour of wave fronts and of uncharged matter is the one indicated by Hély.In the present paper it is shown how the electrostatic solution predicts the structure of the n charged particles and their mutual positions of electrostatic equilibrium when Hély’s physically correct metric is adopted. 相似文献