全文获取类型
| 收费全文 | 846582篇 |
| 免费 | 7514篇 |
| 国内免费 | 2490篇 |
专业分类
| 化学 | 436486篇 |
| 晶体学 | 12717篇 |
| 力学 | 41298篇 |
| 综合类 | 21篇 |
| 数学 | 110522篇 |
| 物理学 | 255542篇 |
出版年
| 2021年 | 7040篇 |
| 2020年 | 7599篇 |
| 2019年 | 8533篇 |
| 2018年 | 11281篇 |
| 2017年 | 11515篇 |
| 2016年 | 16376篇 |
| 2015年 | 9508篇 |
| 2014年 | 15518篇 |
| 2013年 | 37715篇 |
| 2012年 | 28319篇 |
| 2011年 | 34095篇 |
| 2010年 | 25055篇 |
| 2009年 | 24955篇 |
| 2008年 | 31715篇 |
| 2007年 | 31560篇 |
| 2006年 | 28991篇 |
| 2005年 | 25881篇 |
| 2004年 | 24053篇 |
| 2003年 | 21534篇 |
| 2002年 | 21351篇 |
| 2001年 | 23737篇 |
| 2000年 | 18356篇 |
| 1999年 | 14333篇 |
| 1998年 | 12149篇 |
| 1997年 | 12023篇 |
| 1996年 | 11412篇 |
| 1995年 | 10203篇 |
| 1994年 | 10101篇 |
| 1993年 | 9791篇 |
| 1992年 | 10683篇 |
| 1991年 | 11096篇 |
| 1990年 | 10688篇 |
| 1989年 | 10622篇 |
| 1988年 | 10149篇 |
| 1987年 | 10188篇 |
| 1986年 | 9689篇 |
| 1985年 | 12505篇 |
| 1984年 | 12887篇 |
| 1983年 | 10834篇 |
| 1982年 | 11250篇 |
| 1981年 | 10643篇 |
| 1980年 | 10327篇 |
| 1979年 | 11001篇 |
| 1978年 | 11513篇 |
| 1977年 | 11239篇 |
| 1976年 | 11134篇 |
| 1975年 | 10637篇 |
| 1974年 | 10477篇 |
| 1973年 | 10740篇 |
| 1972年 | 7686篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
1.
2.
3.
4.
Padavattan Govindaswamy Patrick J. Carroll Yurij A. Mozharivskyj Mohan Rao Kollipara 《Journal of Chemical Sciences》2006,118(4):319-326
The reaction of [{(η5-C5Me5)M(μ-Cl)Cl}2] {where M = Rh (1), Ir (2)} with functionalized phosphine viz., diphenyl-2-pyridylphosphine (PPh2Py) in dichloromethane solvent yield neutral ϰ1-P-coordinated rhodium and iridium complexes [(η5-C5Me5)RhCl2(κ1-P-PPh2Py)]3 and [(η5-C5Me5) IrCl2(ϰ1-P-PPh2Py)]4. Reaction of complexes 1 and 2 with the ligand PPh2Py in methanol under reflux give bis-substituted complexes such as [(η5-C5Me5)RhCl(ϰ1-P-PPh2Py)2]+
5 and [(η5-C5Me5)IrCl(ϰ1-P-PPh2Py)2]+
6, whereas stirring in methanol at room temperature gives P-, N-chelating complexes of the type [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+ 7 and [(η5-C5Me5)IrCl(ϰ2-P-N-PPh2Py)]+
8. Neutral ϰ1-P-coordinated complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3 and [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 easily undergo conversion to the cationic P-, N-chelating complexes [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+
7 and [(η5-C5Me5) IrCl(ϰ2-P, N-PPh2Py)]+
8 on stirring in methanol at room temperature. These complexes are characterized by FT-IR and FT-NMR spectroscopy as well as
analytical methods. The molecular structures of the representative complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3, [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 and hexafluorophosphate salt of complex [(η5-C5Me5)IrCl(ϰ2-P-PPh2Py)2]+
6 are established by single-crystal X-ray diffraction methods 相似文献
5.
6.
An optimal control model of exhaustible resources is used to clarify the long run relationship between mineral rent and depletion cost at the industry level. A standard first order condition of the time rate of change of rents is reformulated to reveal that rent data may be used to help forecast the rise in extraction costs resulting from resource depletion. This application of the theory of exhaustible resources is illustrated using historical mineral industry rent and extraction cost data. A forecast of U.S. coal extraction costs, following the method proposed in this paper, suggests that future rates of extraction cost increases will be similar to rates experienced in the past. 相似文献
7.
8.
9.
A. Sebbar 《Mathematische Zeitschrift》1989,201(4):561-581
Sans résumé 相似文献
10.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献