全文获取类型
收费全文 | 183篇 |
免费 | 6篇 |
专业分类
化学 | 155篇 |
力学 | 2篇 |
数学 | 10篇 |
物理学 | 22篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1968年 | 1篇 |
1963年 | 3篇 |
1957年 | 1篇 |
1954年 | 1篇 |
1952年 | 1篇 |
1949年 | 1篇 |
1948年 | 2篇 |
1947年 | 7篇 |
1940年 | 1篇 |
1938年 | 2篇 |
排序方式: 共有189条查询结果,搜索用时 15 毫秒
81.
Baron A Herrero C Quaranta A Charlot MF Leibl W Vauzeilles B Aukauloo A 《Inorganic chemistry》2012,51(11):5985-5987
In this Communication, we present the synthesis and use of [Ru(bpy)(2)(bpy-CCH)](2+), a versatile synthon for the construction of more sophisticated dyads by means of click chemistry. The resulting chromophore-acceptor or -donor complexes have been studied by flash photolysis and are shown to undergo efficient electron transfer to/from the chromophore. Additionally, the photophysical and chemical properties of the original chromophore remain intact, making it a very useful component for the preparation of visible-light-active dyads. 相似文献
82.
Rodica Vladoiu Victor Ciupina Mirela Contulov Virginia Dinca Aurelia Mandes Vilma Bursikova 《Plasma Chemistry and Plasma Processing》2012,32(2):219-229
The aim of this contribution is to present the properties of the nanostructured hydrogenated carbon thin films and to study
their growth carried out in a special deposition technique based on Thermionic Vacuum Arc method. The Gaseous Thermionic Vacuum
Arc (G-TVA) technology is an original deposition method performed in a special configuration, consisting of a heated thermionic
cathode which provides an electron beam on the anode. The surface free energy was evaluated by contact angle and their optical
properties were studied by Filmetrics F20 spectrometry system. Structure of the film has been investigated by Raman spectroscopy
as well as the mechanical properties like hardness, wear resistance, film-substrate adhesion. The films showed two distinct
Raman characteristic peaks located at 1,350 cm−1 (D-line) and 1,550 cm−1 (G-line), broad for Si and very sharp for glass substrates. The G-TVA enables to prepare soft (hardness ~6 GPa) or hard (~24 GPa)
films. 相似文献
83.
Ashley Ringer McDonald Jessica A. Nash Paul S. Nerenberg K. Aurelia Ball Olaseni Sode Jonathon J. Foley IV Theresa L. Windus T. Daniel Crawford 《International journal of quantum chemistry》2020,120(20):e26359
The Molecular Sciences Software Institute (MolSSI) is an National Science Foundation (NSF) funded institute that focuses on improving software, education, and training in the computational molecular sciences. Through a collaboration with the Molecular Education and Research Consortium in Undergraduate computational chemistRY (MERCURY), the MolSSI has developed resources for undergraduate and other early career students to lay an educational foundation for the next generation of computational molecular scientists. The resources focus on introducing best practices in software engineering to students from the very start to make their software more useable, maintainable, and reproducible. 相似文献
84.
Small‐Molecule Recognition for Controlling Molecular Motion in Hydrogen‐Bond‐Assembled Rotaxanes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Alberto Martinez‐Cuezva Dr. Jose Berna Dr. Raul‐Angel Orenes Dr. Aurelia Pastor Prof. Dr. Mateo Alajarin 《Angewandte Chemie (International ed. in English)》2014,53(26):6762-6767
Di(acylamino)pyridines successfully template the formation of hydrogen‐bonded rotaxanes through five‐component clipping reactions. A solid‐state study showed the participation of the pyridine nitrogen atom in the stabilization of the mechanical bond between the thread and the benzylic amide macrocycle. The addition of external complementary binders to a series of interlocked bis(2,6‐di(acylamino)pyridines) promoted restraint of the back and forward ring motion. The original translation can be restored through a competitive recognition event by the addition of a preorganized bis(di(acylamino)pyridine) that forms stronger ADA–DAD complexes with the external binders. 相似文献
85.
Miuţa R. Filip Aurelia Pop Ioana Perhaiţa Mărioara Moldovan Roxana Truşcă 《Central European Journal of Chemistry》2013,11(5):725-735
Thermal and catalytic degradation of polystyrene waste over two different samples of natural volcanic tuff catalyst comparative with Florisil catalyst has been carried out in order to establish the conversion degree into styrene monomer. The polystyrene waste (PS) was subjected to a thermal degradation process in the range of 380–500°C in presence of studied catalysts in a ratio of 1/10 in mass, catalyst/PS. The catalysts were characterized by N2 adsorption-desorption isotherms (BET), Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectrometry (FTIR). Influences of temperature and type of catalysts on the yields and on the distribution of end-products obtained by thermal and catalytic degradation of polystyrene waste have been studied. The maximum yields of liquid products were obtained at 460°C degradation temperature and were calculated between 83.45% and 90.11%. The liquid products were characterized by gas chromatography mass spectrometry (GC-MS) and FTIR analytical techniques. The GC-MS results showed that the liquid products contained styrene monomer up to 55.62%. The FTIR spectra of liquid products indicated the specific vibration bands of the functional groups of compounds of liquid products. The amounts of styrene monomer obtained were influenced by structural and textural properties of studied catalyst and the contribution on product distribution is discussed. 相似文献
86.
87.
88.
Carbohydrate‐modified cyclosiloxanes were synthesized by hydrosilylation reactions of protected allyl‐monosaccharides and subsequent deprotection with a gel‐type ion exchanger. They were characterized by 1H and 13C‐NMR, FT‐IR, GPC and surface tension measurements. These compounds, as well as other water soluble, carboxylate‐based siloxanes were tested as stabilizers in nanoparticle formulations, with polydimethylsiloxane (PDMS), poly(ε‐caprolactone) (PCL) and UDEL polysulfone (PSF) as polymer cores. Owing to their low critical micelle concentrations (cmc), small amounts of surfactants were required. The particle size and granulometric distribution were measured by dynamic light scattering (DLS). Electron microscopy confirmed the DLS results and revealed aggregation phenomena in dry state, depending on the polymer core. In the tested conditions, the glass transition temperature of the polymer seems to be the driving force for the stability of dry nanoparticles. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
89.
Iodine and the pincer complex [Pd(O,N,C-L)I], where L is the monoanionic ligand resulting from deprotonation of the acetyl group of the dimethylmonoketal of 2,6-diacetylpyridine, are in equilibrium at low temperatures with the palladium(IV) complex [Pd(O,N,C-L)I(3)], which can be isolated at -40 °C and characterized by (1)H NMR spectroscopy and X-ray diffraction studies, in spite of its great instability. When the same reaction is carried out at room temperature, a quantitative reductive elimination process occurs, giving L-I, which in the presence of water affords L'-I, resulting from hydrolysis of L-I. 相似文献
90.
2-Dimensional almost-Riemannian structures are generalized Riemannian structures on surfaces for which a local orthonormal frame is given by a Lie bracket generating pair of vector fields that can become collinear. Generically, there are three types of points: Riemannian points where the two vector fields are linearly independent, Grushin points where the two vector fields are collinear but their Lie bracket is not, and tangency points where the two vector fields and their Lie bracket are collinear and the missing direction is obtained with one more bracket.In this paper we consider the problem of finding normal forms and functional invariants at each type of point. We also require that functional invariants are “complete” in the sense that they permit to recognize locally isometric structures.The problem happens to be equivalent to the one of finding a smooth canonical parameterized curve passing through the point and being transversal to the distribution.For Riemannian points such that the gradient of the Gaussian curvature K is different from zero, we use the level set of K as support of the parameterized curve. For Riemannian points such that the gradient of the curvature vanishes (and under additional generic conditions), we use a curve which is found by looking for crests and valleys of the curvature. For Grushin points we use the set where the vector fields are parallel.Tangency points are the most complicated to deal with. The cut locus from the tangency point is not a good candidate as canonical parameterized curve since it is known to be non-smooth. Thus, we analyse the cut locus from the singular set and we prove that it is not smooth either. A good candidate appears to be a curve which is found by looking for crests and valleys of the Gaussian curvature. We prove that the support of such a curve is uniquely determined and has a canonical parametrization. 相似文献