全文获取类型
收费全文 | 257篇 |
免费 | 11篇 |
专业分类
化学 | 177篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 14篇 |
物理学 | 70篇 |
出版年
2023年 | 3篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 19篇 |
2012年 | 19篇 |
2011年 | 30篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1987年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
101.
Anions encapsulated by a uniform mode of anion-pi binding in isomorphous (4,4) nets formed from Ag(I) salts and bis(4-pyrimidylmethyl)sulfide appear to be structurally directing. 相似文献
102.
Henry MK Ramanathan C Hodges JS Ryan CA Ditty MJ Laflamme R Cory DG 《Physical review letters》2007,99(22):220501
We demonstrate coherent control of two logical qubits encoded in a decoherence free subspace (DFS) of four dipolar-coupled protons in an NMR quantum information processor. A pseudopure fiducial state is created in the DFS, and a unitary logical qubit entangling operator evolves the system to a logical Bell state. The four-spin molecule is partially aligned by a liquid crystal solvent, which introduces strong dipolar couplings among the spins. Although the system Hamiltonian is never fully specified, we demonstrate high fidelity control over the logical degrees of freedom. In fact, the DFS encoding leads to higher fidelity control than is available in the full four-spin Hilbert space. 相似文献
103.
Rapid quick,easy, cheap,effective, rugged,and safe extraction with novel phospholipid cleanup: A streamlined ultra high performance liquid chromatography with ultraviolet detection approach for screening polycyclic aromatic hydrocarbons in avian blood cells and plasma
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Anthony A. Provatas Alexander V. Yevdokimov Cory A. King Emma L. Gatley James D. Stuart David C. Evers Christopher R. Perkins 《Journal of separation science》2015,38(15):2677-2683
A streamlined method has been developed for the isolation and analysis of polycyclic aromatic hydrocarbons in avian blood cells and plasma utilizing quick, easy, cheap, effective, rugged, and safe extraction in combination with novel phospholipid cleanup technology. A variety of traditional extraction and cleanup techniques have been employed in the preparation and analysis of polycyclic aromatic hydrocarbonsin a variety of matrices; liquid–liquid partitioning, solid‐phase extractions, gel permeation chromatography, and column chromatography are all effective techniques, however they are laborious and time consuming processes that require large amounts of solvent. Using quick, easy, cheap, effective, rugged, and safe extraction coupled with phospholipid cleanup, samples can be quickly screened while maintaining high throughput and sensitivity. With a liquid chromatography approach, analysis times may be kept short at 16 min while maintaining high analyte recovery. Recoveries in quality control samples ranged from 70 to 109%, with average surrogate recoveries of 80.6 ± 1.10%. The result of using a quick, easy, cheap, effective, rugged, and safe extraction approach in conjunction with phospholipid cleanup is a methodology that significantly reduces sample preparation time and solvent use while maintaining high sensitivity and reproducibility. 相似文献
104.
Glen P. Junor Jan Lorkowski Dr. Cory M. Weinstein Dr. Rodolphe Jazzar Prof. Dr. Cezary Pietraszuk Prof. Dr. Guy Bertrand 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22212-22217
Selenium NMR has become a standard tool for scaling the π-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene–selenium 77Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale. 相似文献
105.
Ring crack initiation loads on glass, using spherical Tungsten carbide (WC) and glass (G) indenters, are measured and analysed. Our measurements demonstrate that environmental humidity plays a key role in determining the load to fracture; experiments conducted without controlling this variable cannot be used to obtain material properties. The role of friction is explicitly considered for dissimilar (WC–G) elastic contacts. For this material pair, the stresses at fracture are well described by a boundary lubrication value of friction coefficient. The fracture loads are used in a fracture-mechanics formulation to calculate crack sizes on glass surfaces. The ‘searched-area’ concept for dissimilar contacts is described, and used to provide crack density values for these surfaces. 相似文献
106.
Cory C. Pye 《Central European Journal of Chemistry》2011,9(4):567-571
A geometry and SCF convergence study of Hartree-Fock calculations using the 6-31G* basis set is carried out on the set of
all possible diatomic molecules formed from atoms with Z≤36. The utility of Hartree-Fock calculations using the smaller STO-3G
basis set to improve the convergence behavior is demonstrated.
相似文献
107.
108.
Giffin NA Makramalla M Hendsbee AD Robertson KN Sherren C Pye CC Masuda JD Clyburne JA 《Organic & biomolecular chemistry》2011,9(10):3672-3680
In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC(6)H(2)(CH(3))(3)](2)C···HO(NC(5)H(6)(CH(3))(4)), IMes···TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH(2)Ni-Pr(2)C(6)H(3)](2)CH···O(NC(5)H(6)(CH(3))(4)). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N-[2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph(3)PC(H)C(=O)O(NC(5)H(6)(CH(3))(4)). A full characterization of the product, including an X-ray crystal structure, is described. 相似文献
109.
Beuerle F Herrmann C Whalley AC Valente C Gamburd A Ratner MA Stoddart JF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(14):3868-3875
Toroidal carbon nanotubes (TCNTs), which have been evaluated for their potential applications in terahertz communication systems, provide a challenge of some magnitude from a purely scientific perspective. A design approach to TCNTs, as well as a classification scheme, is presented based on the definition of the six hollow sections that comprise the TCNT, slicing each of them to produce a (possibly creased) planar entity, and projecting that entity onto a graphene lattice. As a consequence of this folding approach, it is necessary to introduce five- and seven-membered rings as defect sites to allow the fusing together of the six segments into final symmetric TCNTs. This analysis permits the definition of a number of TCNT geometry families containing from 108 carbons up to much larger entities. Based on density functional theory (DFT) calculations, the energies of these structural candidates have been investigated and compared with [60]fullerene. The structures with the larger tube diameters are computed to be more stable than C(60) , whereas the smaller diameter ones are less stable, but may still be within synthetic reach. Computational studies reveal that, on account of the stiffness of the structures, the vibrational frequencies of characteristic low-frequency modes decrease more slowly with increasing ring diameter than do the lowest optical excitation energies. It was found that this particular trend is true for the "breathing mode" vibrations when the diameter of the tubes is small, but not for more flexible toroidal nanotubes with larger diameters. 相似文献
110.
Gassensmith JJ Erne PM Paxton WF Valente C Stoddart JF 《Langmuir : the ACS journal of surfaces and colloids》2011,27(4):1341-1345
The controlled growth of metal-organic frameworks (MOFs) over surfaces has been investigated using a variety of surface analytical techniques. The use of microcontact printing to prepare surfaces, patterned with regions capable of nucleating the growth of MOFs, has been explored by employing copper-catalyzed alkyne-azide cycloaddition (CuAAC) to pattern silicon wafers with carboxylic acids, a functional group that has been shown to nucleate the growth of MOFs on surfaces. Upon subjecting the patterned silicon surfaces to solvothermal conditions, MOF thin films were obtained and characterized subsequently by AFM, SEM, and grazing-incidence XRD (GIXRD). Large crystals (~0.5 mm) have also been nucleated, as indicated by the presence of a bas-relief of the original pattern on one surface of the crystal, suggesting that it is possible to transfer the template surface pattern onto a single crystal of a MOF. 相似文献