全文获取类型
收费全文 | 536123篇 |
免费 | 4511篇 |
国内免费 | 1801篇 |
专业分类
化学 | 269839篇 |
晶体学 | 7777篇 |
力学 | 26804篇 |
综合类 | 11篇 |
数学 | 84098篇 |
物理学 | 153906篇 |
出版年
2020年 | 3547篇 |
2019年 | 3993篇 |
2018年 | 14940篇 |
2017年 | 14712篇 |
2016年 | 13384篇 |
2015年 | 5653篇 |
2014年 | 7774篇 |
2013年 | 20300篇 |
2012年 | 18200篇 |
2011年 | 27792篇 |
2010年 | 17712篇 |
2009年 | 17798篇 |
2008年 | 22695篇 |
2007年 | 24888篇 |
2006年 | 15805篇 |
2005年 | 15509篇 |
2004年 | 14390篇 |
2003年 | 13483篇 |
2002年 | 12533篇 |
2001年 | 13117篇 |
2000年 | 10095篇 |
1999年 | 7831篇 |
1998年 | 6808篇 |
1997年 | 6746篇 |
1996年 | 6429篇 |
1995年 | 5919篇 |
1994年 | 5880篇 |
1993年 | 5704篇 |
1992年 | 6307篇 |
1991年 | 6312篇 |
1990年 | 6067篇 |
1989年 | 5980篇 |
1988年 | 6121篇 |
1987年 | 5922篇 |
1986年 | 5652篇 |
1985年 | 7550篇 |
1984年 | 7996篇 |
1983年 | 6650篇 |
1982年 | 7044篇 |
1981年 | 6906篇 |
1980年 | 6787篇 |
1979年 | 6792篇 |
1978年 | 7194篇 |
1977年 | 7051篇 |
1976年 | 7253篇 |
1975年 | 6619篇 |
1974年 | 6763篇 |
1973年 | 7218篇 |
1972年 | 4788篇 |
1971年 | 3870篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Mustafa Çelebier Ertan Şahin Nilgün Ancın Nurşen Altuntaş Öztaş Selma Gül Öztaş 《应用有机金属化学》2007,21(10):viii-viii
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
103.
104.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
105.
R. Centore P. Riccio S. Fusco A. Carella A. Quatela S. Schutzmann F. Stella F. De Matteis 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2719-2725
We have prepared new polyesters containing quadratic, nonlinear optical (NLO) active chromophores covalently incorporated into the main chain. In these polymers, the sequence of the chromophore units along the main chain is rigorously head to tail. All the polyesters are processable, both in the melt and in solution. For one polyester, a full second‐order NLO characterization has been performed. An out‐of‐resonance d33 coefficient of 21 pm/V at 1368 nm has been measured. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2719–2725, 2007 相似文献
106.
The microstructure evolution of decagonal quasicrystals in Al72Ni12Co16 alloy was investigated by the electromagnetic melting and cyclic superheating method. Single-phase decagonal quasicrystals have been obtained when the undercoolings were larger than 60 K. The decagonal quasicrystals formed at various undercoolings show different microstructural morphologies. Furthermore, grain refinement was found near the undercooling of 120 K. Based on current thermodynamic and dendrite growth theories, a dimensionless superheating parameter was adopted to explain the effect of processing conditions on the microstructure of Al72Ni12Co16 alloy. The result indicate that the fine equiaxied microstructure of decagonal quasicrystal (D-phase) formed near on undercooling of 120 K originates from the break-up of dendrites. 相似文献
107.
Daria E. Lonsdale Geoffrey Johnston‐Hall Amanda Fawcett Craig A. Bell Carl N. Urbani Michael R. Whittaker Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3620-3625
In this work, we propose that retardation in vinyl acetate polymerization rate in the presence of toluene is due to degradative chain transfer. The transfer constant to toluene (Ctrs) determined using the Mayo method is equal to 3.8 × 10?3, which is remarkably similar to the value calculated from the rate data, assuming degradative chain transfer (2.7 × 10?3). Simulations, including chain‐length‐dependent termination, were carried out to compare our degradative chain transfer model with experimental results. The conversion–time profiles showed excellent agreement between experiment and simulation. Good agreement was found for the Mn data as a function of conversion. The experimental and simulation data strongly support the postulate that degradative chain transfer is the dominant kinetic mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3620–3625, 2007 相似文献
108.
109.
Bahattin Gümgüm Nermin Biricik Feyyaz Durap Ismail Özdemir Nevin Gürbüz Wee Han Ang Paul J. Dyson 《应用有机金属化学》2007,21(8):711-715
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
110.