全文获取类型
收费全文 | 12306篇 |
免费 | 1971篇 |
国内免费 | 2307篇 |
专业分类
化学 | 9506篇 |
晶体学 | 147篇 |
力学 | 719篇 |
综合类 | 172篇 |
数学 | 1573篇 |
物理学 | 4467篇 |
出版年
2024年 | 36篇 |
2023年 | 272篇 |
2022年 | 493篇 |
2021年 | 519篇 |
2020年 | 556篇 |
2019年 | 550篇 |
2018年 | 451篇 |
2017年 | 466篇 |
2016年 | 638篇 |
2015年 | 667篇 |
2014年 | 713篇 |
2013年 | 983篇 |
2012年 | 954篇 |
2011年 | 1043篇 |
2010年 | 770篇 |
2009年 | 717篇 |
2008年 | 830篇 |
2007年 | 697篇 |
2006年 | 654篇 |
2005年 | 607篇 |
2004年 | 510篇 |
2003年 | 428篇 |
2002年 | 492篇 |
2001年 | 389篇 |
2000年 | 327篇 |
1999年 | 284篇 |
1998年 | 216篇 |
1997年 | 154篇 |
1996年 | 180篇 |
1995年 | 128篇 |
1994年 | 153篇 |
1993年 | 119篇 |
1992年 | 86篇 |
1991年 | 106篇 |
1990年 | 100篇 |
1989年 | 49篇 |
1988年 | 45篇 |
1987年 | 34篇 |
1986年 | 40篇 |
1985年 | 45篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1957年 | 3篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The first α‐diimine nickel(I) complex having a chloro bridge is reported. The centrosymmetric dinuclear structure of {[ArN?C(Me)C(Me)?NAr]NiCl}2[Ar?2,6?C6H3(i‐Pr)2] features two chelating α‐diimine ligands and two bridged chlorine atoms, so that a distorted tetrahedral N2Cl2 coordination geometry for nickel results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
2.
3.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
4.
Qi Wang Huaxiang Yang Zhiqiang Fan Hong Xu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1093-1099
Ethylisobutylaluminoxane (EBAO) and its analogues were synthesized by a reaction between an triethylaluminum (Et3Al)/triisobutylaluminum (i‐Bu3Al) mixture and 4‐fluorobenzeneboronic acid, phenylboronic acid, or n‐butaneboronic acid and subsequent hydrolysis with water. They were used as cocatalysts in ethylene polymerization catalyzed by an iron complex {[(ArN?C(Me))2C5H3N]FeCl2, where Ar is 2,6‐diisopropylphenyl}. Polyethylene with a high molecular weight and a narrow molecular weight distribution was prepared with modified EBAOs, and the performance of the iron complex at high polymerization temperatures was greatly improved. The activators for the iron complex also affected the polymerization activity and the molecular weight of the resultant polyethylene. It was suggested that the stereo and electronic effects of the substitute groups of aluminoxane contributed to the improved performance of the new activators. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1093–1099, 2004 相似文献
5.
Raymond Mackay Jie Zhang Qi Wu Yuzhuo Li 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):343-348
The longitudinal relaxation times (T1) of water in concentrated silica and alumina slurries were measured as a function of solids content. It was shown that the results could be fit very well with a two-phase fast-exchange model between free and surface-bound water. As expected, values of T1 for bound water were in the order of 20–2000 times lower than that for free water, indicating a higher effective viscosity of the surface-bound water. The strength of the interaction depended on the particular surface, and all of the aluminas examined interacted more strongly with water than the two silicas studied, which themselves differed considerably. The chemical mechanical polishing (CMP) removal rate of tantalum by silica slurries was shown to be directly correlated with the interaction parameters, derived from the NMR relation times rather than with total surface hydroxyl group concentration. 相似文献
6.
An equation to express ion exchange selectivity coefficient was derived and used for calculating that of PPY film with the results obtained by cyclic voltammetric measurement. PPY film was synthesized by electrochemical method in aqueous solution using K4Fe(CN)6 as supporting electrolyte, and the anions were doped into the film. Ion exchange behaviour of doped Fe (CN)63-/4- in the PPY film with Cl?, NO3? or F? ions in solution has been studied, and the corresponding ion exchange selectivity coefficients were determined. 相似文献
7.
8.
9.
Qi Sheng Liu Lian Dong Liu Jing Min Shi 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m58-m60
In the title centrosymmetric binuclear complex, [Cd2(C17H11N3O)4(H2O)2](ClO4)4, the CdII ion assumes a distorted octahedral geometry. There are π–π stacking interactions between the pyridine and 1,10‐phenanthroline ring systems of adjacent ligands at the same CdII centre. Intermolecular hydrogen bonds between the coordinated aqua ligand and the O atom of a keto group connect adjacent complex cations into extended chains. Hydrogen bonds also exist between the complex cations and the perchlorate anions. Compared with the fluorescence spectrum of the organic ligand, the complex displays strong fluorescent emission and an ipsochromic shift of the emission peaks, which may be attributed to the structural character. 相似文献
10.