全文获取类型
收费全文 | 387篇 |
免费 | 14篇 |
专业分类
化学 | 195篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 76篇 |
物理学 | 127篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 22篇 |
2011年 | 38篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 40篇 |
2006年 | 27篇 |
2005年 | 25篇 |
2004年 | 25篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 15 毫秒
101.
Dr. Peterson de Andrade Dr. Juan C. Muñoz-García Dr. Giulia Pergolizzi Valeria Gabrielli Dr. Sergey A. Nepogodiev Dr. Dinu Iuga László Fábián Rinat Nigmatullin Dr. Marcus A. Johns Dr. Robert Harniman Prof. Stephen J. Eichhorn Dr. Jesús Angulo Prof. Yaroslav Z. Khimyak Prof. Robert A. Field 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(4):1374-1382
Understanding the fine details of the self-assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft-matter materials with specific properties. Enzymatically synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self-assemble into particles resembling the antiparallel cellulose II crystalline packing. We have prepared and characterised a series of site-selectively fluorinated cellodextrins with different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. Bearing in mind the potential disruption of the hydrogen-bond network of cellulose II, we have prepared and characterised a multiply 6-fluorinated cellodextrin. In addition, a series of single site-selectively fluorinated cellodextrins was synthesised to assess the structural impact upon the addition of one fluorine atom per chain. The structural characterisation of these materials at different length scales, combining advanced NMR spectroscopy and microscopy methods, showed that a 6-fluorinated donor substrate yielded multiply 6-fluorinated cellodextrin chains that assembled into particles presenting morphological and crystallinity features, and intermolecular interactions, that are unprecedented for cellulose-like materials. 相似文献
102.
Vadym V. Levterov Dr. Yaroslav Panasyuk Valentyna O. Pivnytska Dr. Pavel K. Mykhailiuk 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7228-7234
A new generation of saturated benzene mimetics, 2-oxabicyclo[2.1.1]hexanes, was developed. These compounds were designed as analogues of bicyclo[1.1.1]pentane with an improved water solubility. Crystallographic analysis of 2-oxabicyclo[2.1.1]hexanes revealed that they occupy a novel chemical space, but, at the same time, resemble the motif of meta-disubstituted benzenes. 相似文献
103.
104.
Ermira Begu Yaroslav Shlyapnikov Andrej Stergarsek Peter Frkal Jože Kotnik 《International journal of environmental analytical chemistry》2016,96(7):609-626
Mercury in aqueous systems can be present in different chemical forms. Of these, dissolved elemental Hg(0) (DEM) is of great importance because it can readily be partitioned between air and water. Analytical methods used for determining DEM are conventionally based on removal of Hg(0) by purging, pre-concentration on gold and detection by either cold vapour atomic absorption (CV-AAS) or atomic fluorescence spectrophotometry (CV-AFS). At present, there is no agreed protocol for the measurement of DEM in aqueous samples. A new method is described here, which is based on continuous stripping of DEM by mercury-free nitrogen in a flow injection mode and detection by CV-AAS. The partitioning of DEM between aqueous and gas phases is largely dependent on the composition of the former. Moreover, calibration using the standard addition method is not possible due to the reactivity of DEM introduced from calibration solutions. Calibration is therefore done by reference measurements using a manual method for DEM involving quantitative removal and CV-AFS detection. DEM is then determined in the water sample by applying the partitioning factor. The optimised method is precise, sensitive and linear over a wide concentration range. It has provided comparable results with the manual method when applied on board a research vessel in the Mediterranean Sea (0.02–0.05 ng L?1) and during a pilot laboratory-scale experiment on industrial aqueous media from wet flue gas desulphurisation (WFGD) equipment (2–300 ng L?1). 相似文献
105.
Iryna Antal Zholt Kormosh Yaroslav Bazel Svitlana Lysenko Natalya Kormosh 《Electroanalysis》2010,22(22):2714-2719
Vitamin B1‐selective electrodes with PVC membrane were developed that contain ion associates of vitamin B1 with an inorganic anion, BiI4?, and an organic anion, brilliant yellow, as electrode‐active substances. The linearity ranges of the electrode function are 1.0×10?5–1.0×10?2 and 1.0×10?4–1.0×10?2 M, the electrode function slopes are 33.0±1.0 and 33.1±1.1 mV decade?1, the detection limits are 5.5×10?6 and 8.3×10?5 M for BiI4? and brilliant yellow respectively. The working range of pH is 5–12. The efficiency of the use of electrodes for the vitamin B1 content control in multivitamin pharmaceutical preparations was shown by direct potentiometry and potentiometric titration methods. 相似文献
106.
We report on the existence of nonlinear surface waves that, on the one hand, do not require the threshold energy flow for their excitation, and, on the other hand, extend into media at both sides of the interface at low powers, i.e., cannot be reduced to the conventional Tamm states. Such waves can be excited if the refractive index in at least one of the materials forming the interface is periodically modulated, with properly selected modulation depth and frequency. Thresholdless surface solitons can be stable in the entire existence domain. 相似文献
107.
Rastislav Serbin Yaroslav R. Bazel Marcel Torok Josef Havel Ioseph S. Balogh Zholt O. Kormosh Gabriela Holéczyová Vasil Andruch 《中国化学会会志》2009,56(6):1168-1174
A new, simple, rapid, sensitive, efficient and low‐cost spectrophotometric procedure for the determination of gold was developed. The method is based on the reaction of [AuCl4]? with 2‐[2‐(4‐dimethylaminophenyl)‐vinyl]‐1,3,3‐trimethyl‐3H‐indolium reagent to form a colored ion associate extractable by various organic solvents. The molar absorptivity of the ion associates is in the range (5.7–9.2) × 104 L mol?1 cm?1 depending on the extractant. Butyl acetate was chosen as the extractant. The optimum reaction conditions were established: pH 2–4, concentration of the dye reagent (0.8–1.5) × 10?4 mol L?1. The determination of gold is not hindered even by a 1000‐fold concentration of Ni and Co; a 500‐fold concentration of Pb and Zn; a 100‐fold concentration of Bi, Cu, Cd, Pt, Rh and Ru; or a 20‐fold concentration of Ag. The established method was applied to the determination of gold in model samples and enriched polymetallic ores. 相似文献
108.
Yaroslav O. Tokaychuk Yaroslav E. Filinchuk Anatoliy O. Fedorchuk Ivanna R. Mokra 《Journal of solid state chemistry》2006,179(5):1323-1329
New ternary intermetallic compounds Sm2Ga7−xGex (x=5.2-6.1) and Sm4Ga11−xGex (x=5.76-8.75) were synthesized and their crystal structures were determined by X-ray powder diffraction at compositions Sm2Ga1.8Ge5.2 and Sm4Ga5.24Ge5.76. Sm2Ga1.8Ge5.2 crystallizes with the Ce2(Ga0.1Ge0.9)7 type of structure (space group Cmce, Pearson code oS80-8.00, a=8.46216(13), b=8.15343(13), , Z=8), while Sm4Ga5.24Ge5.76 exhibits a new structure (space group Cmmm, Pearson code oS52-22.00, a=4.21038(4), b=35.8075(3), , Z=2). Both structures are the members of the linear intergrowth structure series built up from segments of BaAl4, AlB2 and α-Po structure types. Their Ga/Ge networks contain characteristic empty cubes with one side capped by an atom subjected to an intrinsic displacive disorder. A model of Ga/Ge localization was suggested on the basis of crystal-chemical analysis. 相似文献
109.
Ganin AY Takabayashi Y Bridges CA Khimyak YZ Margadonna S Prassides K Rosseinsky MJ 《Journal of the American Chemical Society》2006,128(46):14784-14785
Co-intercalation of methylamine molecules into the cubic K3C60 lattice affords the fulleride (CH3NH2)K3C60, which was characterized by Raman and MAS 13C and 1H NMR spectroscopy. The high-resolution synchrotron X-ray powder diffraction technique was employed to determine its crystal structure at ambient temperature. We find that CH3NH2 bonds to K+ ions residing in the pseudo-octahedral interstices, thereby providing an efficient and facile route to hyperexpanded close-packed strongly anisotropic fulleride lattices, while retaining the electronic contact between the C603- anions. Preliminary evidence for the occurrence of a transition to an antiferromagnetic state at low temperature is also presented, consistent with the proximity of the present system to the metal-insulator boundary of the electronic phase diagram of C603- fullerides. 相似文献
110.
X-ray data on single crystals of the quaternary metal hydride near the composition LiB(0.33)N(0.67)H(2.67), previously identified as "Li3BN2H8", reveal that its true composition is Li4BN3H10. The structure has body-centered-cubic symmetry [space group I2(1)3, cell parameter a = 10.679(1)-10.672(1) Angstroms] and contains an ordered arrangement of BH4- and NH2- anions in the molar ratio 1:3. The borohydride anion has an almost ideal tetrahedral geometry (angleH-B-H approximately 108-114 degrees), while the amide anion has a nearly tetrahedral bond angle (angleH-N-H approximately 106 degrees). Three symmetry-independent Li atom sites are surrounded by BH4- and NH2- anions in various distorted tetrahedral configurations, one by two B and two N atoms, another by four N atoms, and the third by one B and three N atoms. The Li configuration around B is nearly tetrahedral, while that around N resembles a distorted saddlelike configuration, similar to those in LiBH4 and LiNH2, respectively. 相似文献