全文获取类型
收费全文 | 323篇 |
免费 | 10篇 |
专业分类
化学 | 281篇 |
晶体学 | 5篇 |
数学 | 29篇 |
物理学 | 18篇 |
出版年
2023年 | 3篇 |
2022年 | 26篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 23篇 |
2012年 | 19篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 19篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 18篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1995年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有333条查询结果,搜索用时 15 毫秒
21.
Monika Karpierz Jan Suchanicz Krzysztof Konieczny Dorota Sitko Pascal Marchet Urszula Lewczuk 《Phase Transitions》2015,88(7):662-667
The 0.5K0.5Bi0.5TiO3–0.5PbTiO3 ceramics were prepared by following a standard solid-state method. The Raman, thermal and dielectric properties of these ceramics were investigated. The X-ray measurements showed that samples have single perovskite-type structure with tetragonal symmetry. Dielectric study revealed that the dielectric behaviour of the investigated ceramics is rather of normal ferroelectrics with large thermal hysteresis. The transition temperature observed by means of differential scanning calorimetry measurements is in good agreement with that obtained from dielectric study. 相似文献
22.
Journal of Thermal Analysis and Calorimetry - The research consisted of investigation of non-freezable bound water (NFW) contents of raw hydroxypropylcellulose (HPC) Klucel® Pharm HF, MF, and... 相似文献
23.
24.
Gawronski J Gawronska K Grajewski J Kacprzak K Rychlewska U 《Chemical communications (Cambridge, England)》2002,(6):582-583
Chiral oligomeric diimides prepared from pyromellitic dianhydride, (R,R)-1,2-diaminocyclohexane and phthalic anhydride fold into M or P helical conformers; trimer 1 folds into the P conformer in the crystal but the M conformer dominates in solution; longer chain oligomers 2 and 3 form preferentially P conformers in solution, as a result of intermolecular interactions. 相似文献
25.
Low-frequency current fluctuations are investigated over a bias range covering Ohmic, trap-filling, and space-charge-limited current regimes in polycrystalline polyacenes. The relative current noise power spectral density S(f) is constant in the Ohmic region, steeply increases at the trap-filling transition region, and decreases in the space-charge-limited-current region. The noise peak at the trap-filling transition is accounted for within a continuum percolation model. As the quasi-Fermi level crosses the trap level, intricate insulating paths nucleate within the Ohmic matrix, determining the onset of nonequilibrium conditions at the interface between the insulating and conducting phase. The noise peak is written in terms of the free and trapped charge carrier densities. 相似文献
26.
A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl2(4-pmOpe)2], [NiCl2(4-pmOpe)4], [CoCl2(4-pmOpe)], [ZnCl2(4-pmOpe)2], and [CdCl2(4-pmOpe)2], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic
studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl
oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination
mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe
acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II)
and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice. 相似文献
27.
Urszula Koss Mariusz ?ukaszewski Katarzyna Hubkowska Andrzej Czerwi��ski 《Journal of Solid State Electrochemistry》2011,15(11-12):2477-2487
Hydrogen electrosorption into Pd-rich (>80?at.% Pd in the bulk) Pd?CRh alloys has been studied in acidic solutions (0.5?M H2SO4) using cyclic voltammetry and chronoamperometry. The influence of temperature (in the range between 283 and 328?K), electrode potential and alloy bulk composition on hydrogen electrosorption properties of Pd?CRh alloys is presented. It has been found that the additive of Rh to Pd?CRh alloys increases the maximum hydrogen solubility (for Rh bulk content below 10?at.%), decreases the potential of absorbed hydrogen oxidation peak and decreases the potential of the ???????? phase transition. Increasing temperature decreases the potential of absorbed hydrogen oxidation peak, the maximum hydrogen solubility, and the potential of the ???????? phase transition. The amounts of electrosorbed hydrogen for ??- and ??-phase boundaries, i.e., ??max and ??min, have been determined from the integration of the initial parts of current?Ctime responses in hydrogen absorption and desorption processes. The H/M ratio corresponding to ??max increases with increasing Rh content, while for ??min a maximum of H/M ratio is observed for the alloys containing ca. 95% Rh. 相似文献
28.
In this paper, we present an analysis for the class of delay differential equations with one discrete delay and the right‐hand side depending only on the past. We extend the results from paper by U. Fory? (Appl. Math. Lett. 2004; 17 (5):581–584), where the right‐hand side is a unimodal function. In the performed analysis, we state more general conditions for global stability of the positive steady state and propose some conditions for the stable Hopf bifurcation occurring when this steady state looses stability. We illustrate the analysis by biological examples coming from the population dynamics. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
29.
Urszula Rychlewska Beata Warzajtis Biljana D. Glisic Snezana Rajkovic Milo Djuran 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(2):m51-m54
Crystallographic analysis of a solid solution of two diastereoisomers, i.e. ({(1S,R)‐1‐carboxy‐3‐[(R,S)‐methylsulfinyl]propyl}aminocarbonyl)methanaminium tetrachloridoaurate(III) and ({(1S,R)‐1‐carboxy‐3‐[(S,R)‐methylsulfinyl]propyl}aminocarbonyl)methanaminium tetrachloridoaurate(III), (C7H15N2O4S)[AuCl4], has shown that in the presence of gold(III), the methionine part of the Gly‐d ,l ‐Met dipeptide is oxidized to sulfoxide, and no coordination to the AuIII cation through the S atom of the sulfoxide is observed. In view of our observation, literature reports that methionine acts as an N,S‐bidentate donor ligand forming stable gold(III) complexes require verification. Moreover, it has been demonstrated that crystallization of the oxidation product leads to a substantial 77:23 excess of both S‐methionine/R‐sulfoxide and R‐methionine/S‐sulfoxide over S‐methionine/S‐sulfoxide and R‐methionine/R‐sulfoxide. The presence of two different diastereoisomers at the same crystallographic site is a source of static disorder at this site. 相似文献
30.
Fic E Kedracka-Krok S Jankowska U Pirog A Dziedzicka-Wasylewska M 《Electrophoresis》2010,31(21):3573-3579
Sample preparation is a fundamental step in proteomic methodologies. The quality of the results from a proteomic experiment is dependent on the nature of the sample and the properties of the proteins. In this study, various pre-treatment methods were compared by proteomic analysis; we analysed various rat brain structures after chloroform/methanol, acetone, TCA/acetone and TCA protein precipitation procedures. The protein content of the supernatant was also examined by 2-DE. We found that for four of the rat brain structures, precipitation with chloroform/methanol and acetone delivered the highest protein recovery for top-down proteomic analysis; however, TCA precipitation resulted in good protein separation and the highest number of protein spots in 2-DE. Moreover, TCA precipitation also gave high efficiency of protein recovery if prior sonication procedure was performed. 相似文献