全文获取类型
收费全文 | 4429篇 |
免费 | 153篇 |
国内免费 | 3篇 |
专业分类
化学 | 2819篇 |
晶体学 | 40篇 |
力学 | 176篇 |
数学 | 675篇 |
物理学 | 875篇 |
出版年
2023年 | 30篇 |
2022年 | 36篇 |
2021年 | 52篇 |
2020年 | 89篇 |
2019年 | 78篇 |
2018年 | 82篇 |
2017年 | 75篇 |
2016年 | 167篇 |
2015年 | 109篇 |
2014年 | 149篇 |
2013年 | 368篇 |
2012年 | 216篇 |
2011年 | 212篇 |
2010年 | 156篇 |
2009年 | 131篇 |
2008年 | 159篇 |
2007年 | 156篇 |
2006年 | 159篇 |
2005年 | 139篇 |
2004年 | 136篇 |
2003年 | 89篇 |
2002年 | 122篇 |
2001年 | 79篇 |
2000年 | 52篇 |
1999年 | 60篇 |
1998年 | 58篇 |
1997年 | 52篇 |
1996年 | 38篇 |
1995年 | 59篇 |
1994年 | 52篇 |
1993年 | 52篇 |
1992年 | 49篇 |
1991年 | 30篇 |
1990年 | 37篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 44篇 |
1986年 | 34篇 |
1985年 | 47篇 |
1984年 | 54篇 |
1982年 | 49篇 |
1981年 | 36篇 |
1980年 | 45篇 |
1979年 | 35篇 |
1978年 | 37篇 |
1977年 | 48篇 |
1976年 | 50篇 |
1975年 | 40篇 |
1974年 | 28篇 |
1973年 | 35篇 |
排序方式: 共有4585条查询结果,搜索用时 46 毫秒
1.
2.
Ludmila C. Fidale Sarah Köhler Martin H.G. Prechtl Thomas Heinze Omar A. El Seoud 《Cellulose (London, England)》2006,13(5):581-592
The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of νOH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on. 相似文献
3.
4.
Thomas Pautzsch Elisabeth Klemm 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):2911-2919
Poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3a ), poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐4,4′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3b ), and poly{bis(2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3c ) were synthesized by the Suzuki coupling reaction. The alternating structure of the copolymers was confirmed by 1H and 13C NMR and elemental analysis. The polymers showed, by ultraviolet–visible, the π–π* absorption of the polymer backbone (320–380 nm) and at a lower energy attributed to the d–π* metal‐to‐ligand charge‐transfer absorption (450 nm for linear 3a and 480 nm for angular 3b ). The polymers were characterized by a monomodal molecular weight distribution. The degree of polymerization was approximately 8 for polymer 3b and 28 for polymer 3d . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2911–2919, 2004 相似文献
5.
Thomas Pautzsch Lars Blankenburg Elisabeth Klemm 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):722-732
A series of novel π-conjugated polymers containing ruthenium bipyridine complexes was synthesized by a cross-coupling reaction and characterized. These polymers exhibit absorption maxima around 330–350 nm (π-π*) and 460–500 nm metal-to-ligand charge transfer (MLCT), respectively. They are soluble in common organic solvents, and all polymers can be converted into transparent films. We investigated the influence of different donating and acceptor diethynylarenes of the ultraviolet-visible spectra. The oxidation potential, which was measured by cyclic- and square-wave voltametry, showed a typical Ru2+/3+ exhibited at 1.25 V versus the saturated calomel electrode. The polymers were further characterized with photoluminescence measurements. When excited at 442 nm ( 11a ), the polymer exhibited an emission peak at 690 nm. This peak was attributed to the MLCT states. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 722–732, 2004 相似文献
6.
7.
We present some classical solutions to a gauge theory based on quadratically nonlinear Lie algebras without a central term. We observe that instanton-like and meron-like solutions force the internal fields to behave like solitons. 相似文献
8.
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
9.
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
10.
E. I. Ölmez D. Kut A. N. Bilge I. Ölmez 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):227-231
In ambient air, arsenic to selenium ratio (As/Se) is generally found to be less than 1, except in areas influenced by specific
point sources, such as Cu smelters. However, the annual average of this ratio is found to be much higher than unity in Turkey.
This finding is rather unique and may provide a marker for air masses influenced by the coal-related emissions in Turkey.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献