全文获取类型
收费全文 | 307篇 |
免费 | 12篇 |
专业分类
化学 | 239篇 |
晶体学 | 1篇 |
力学 | 14篇 |
数学 | 16篇 |
物理学 | 49篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 21篇 |
2012年 | 34篇 |
2011年 | 37篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 24篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 6 毫秒
61.
Dr. Joice Thomas Dr. Liliana Dobrzańska Prof. Luc Van Meervelt Prof. Mario Alfredo Quevedo Prof. Krzysztof Woźniak Marcin Stachowicz Prof. Mario Smet Prof. Wouter Maes Prof. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):979-987
A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert‐butyl ester groups. Single‐crystal X‐ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy‐substituted macrocycle undergoes a single‐crystal‐to‐single‐crystal transformation during which the molecular structure changes its conformation from 1,3‐alternate (loaded with THF/water) to 1,2‐alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles. 相似文献
62.
Wouter Zijl 《国际流体数值方法杂志》1988,8(5):599-612
A formulation based on three scalar functions or potentials is applied to analyse the Navier-Stokes and Boussinesq equations in three dimensions. In this formulation an explicit expression for the pressure exists, the so-called generalized Bernoulli equation. Therefore the scalar functions formulation may be considered as a generalization of the well-known potential flow and Bernoulli theory for irrotational fluid motion. The many advantages of this formulation applied to three-dimensional Navier-Stokes and Boussinesq flow will be discussed, and a numerical example is given as an illustration. 相似文献
63.
Martin Berkheij Claudia Sewing Jan Willem Terpstra Wouter I. Iwema Bakker Jan H. van Maarseveen 《Tetrahedron letters》2005,46(14):2369-2371
A novel efficient synthetic route towards the pharmaceutically relevant 2-substituted piperazine class is described. The key step involves α-lithiation of N-Boc piperazines, followed by reaction with several electrophiles. To obtain high yields, in some cases transmetallation to copper after the lithiation step is required. 相似文献
64.
The development of a miniaturized ammonia sensor made using microsystem technology is described. Gas is sampled in a sampler comprising two opposite channels separated by a gas permeable, water repellent polypropylene membrane. Subsequently, the acid sample solution is pumped into a selector where an alkaline solution is added to ionize all sampled ambient acid gasses, resulting in an enhanced selectivity. In the selector, the ammonia can diffuse through a second membrane into a purified water stream where an electrolyte conductivity sensor quantifies the resulting ammonium concentration. The realized system is shown to be selective enough not to be influenced by normal ambient carbon dioxide concentrations. Experiments with a gas flow of 3 ml/min, containing ammonia concentrations ranging from 9.8 to 0.3 ppm in a nitrogen carrier flow, into a 15 μl/min sample solution flow and finally into a 5 μl/min purified water stream have been carried out and show that the system is sensitive to ammonia concentration below 1 ppm. 相似文献
65.
Delanoye SN Herrebout WA van der Veken BJ 《The journal of physical chemistry. A》2005,109(43):9836-9843
Complexation enthalpies of the complexes of the haloforms HCCl(n)F(3-)(n) (n = 0-3) with dimethyl ether, oxirane, and acetone have been determined in liquid krypton and/or liquid argon using infrared spectroscopy. The same quantities were derived starting from ab initio complexation energies, calculated at the MP2=FULL/aug-cc-VTZ level, and by correcting these energies for thermodynamic and solvent contributions. The two sets of data are compared and discussed. 相似文献
66.
67.
Tribenzotriquinacene Receptors for C60 Fullerene Rotors: Towards C3 Symmetrical Chiral Stators for Unidirectionally Operating Nanoratchets 下载免费PDF全文
Dr. Björn Bredenkötter Dr. Maciej Grzywa Dr. Mohammad Alaghemandi Dr. Rochus Schmid Prof. Dr. Wouter Herrebout Prof. Dr. Patrick Bultinck Prof. Dr. Dirk Volkmer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):9100-9110
The synthesis of a stereochemically pure concave tribenzotriquinacene receptor ( 7 ) for C60 fullerene, possessing C3 point group symmetry, by threefold condensation of C2‐symmetric 1,2‐diketone synthons ( 5 ) and a hexaaminotribenzotriquinacene core ( 6 ) is described. The chiral diketone was synthesized in a five‐step reaction sequence starting from C2h‐symmetric 2,6‐di‐tert‐butylanthracene. The highly diastereo‐discriminating Diels–Alder reaction of 2,6‐di‐tert‐butylanthracene with fumaric acid di(?)menthyl ester, catalyzed by aluminium chloride, is the relevant stereochemistry introducing step. The structure of the fullerene receptor was verified by 1H and 13C NMR spectroscopy, mass spectrometry and single crystal X‐ray diffraction. VCD and ECD spectra were recorded, which were corroborated by ab initio DFT calculations, establishing the chiral nature of 7 with about 99.7 % ee, based on the ee (99.9 %) of the chiral synthon ( 1 ). The absolute configuration of 7 could thus be established as all‐S [(2S,7S,16S,21S,30S,35S)‐( 7 )]. Spectroscopic titration experiments reveal that the host forms 1:1 complexes with either pure fullerene (C60) or fullerene derivatives, such as rotor 1′‐(4‐nitrophenyl)‐3′‐(4‐N,N‐dimethylaminophenyl)‐pyrazolino[4′,5′:1,2][60]fullerene ( R ). The complex stability constants of the complexes dissolved in CHCl3/CS2 (1:1 vol. %) are K([ C60 ? 7 ])=319(±156) M ?1 and K([ R ? 7 ])=110(±50) M ?1. With molecular dynamics simulations using a first‐principles parameterized force field the asymmetry of the rotational potential for [ R ? 7 ] was shown, demonstrating the potential suitability of receptor 7 to act as a stator in a unidirectionally operating nanoratchet. 相似文献
68.
Kamalika Sen Wouter A. P. Breeman H. Th. Wolterbeek 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):683-687
The present article describes the probable speciation of 68Ga radionuclide just before labeling to DOTA peptides for PET imaging. The 68Ga eluted from an anion exchange column after its purification was analyzed for its elemental composition and pH at several
stages. Neutron activation analysis of the eluted fractions yields the concentrations of Na and Cl, pH measurements indicate
the concentration of free H+ ions in the medium and specific activity calculations indicate the concentration of 68Ga in the solution. Using all these information we get the idea of speciation of no carrier added Ga in the eluted fractions
from CHEAQS programme. The estimations indicate that Ga is mostly present as GaCl2+ in the total MiliQ eluate. However, just before labeling of DOTA the pH of the Ga-containing eluate is adjusted to ~3.5 using
HEPES buffer and at that condition Ga remains as Ga3+ species which is responsible for a successful and efficient labeling. The MilliQ eluate collected before actual labeling
was estimated for trace elements using inductively coupled plasma atomic emission spectrometry was found to contain a few
ppb of Al, Co, Pd and Pt that did not interfere in the actual labeling. A clear idea about the prerequisite of 68Ga species before labeling to a peptide might be of special interest for its judicious application as a radiopharmaceutical. 相似文献
69.
Bogdan I. Florea Martijn Verdoes Nan Li Wouter A. van der Linden Paul P. Geurink Hans van den Elst Tanja Hofmann Arnoud de Ru Peter A. van Veelen Keiji Tanaka Katsuhiro Sasaki Shigeo Murata Hans den Dulk Jaap Brouwer Ferry A. Ossendorp Alexei F. Kisselev Herman S. Overkleeft 《Chemistry & biology》2010,17(8):795-801
70.