全文获取类型
收费全文 | 603篇 |
免费 | 24篇 |
国内免费 | 2篇 |
专业分类
化学 | 454篇 |
晶体学 | 6篇 |
力学 | 13篇 |
数学 | 74篇 |
物理学 | 82篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 17篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 27篇 |
2013年 | 55篇 |
2012年 | 41篇 |
2011年 | 53篇 |
2010年 | 28篇 |
2009年 | 19篇 |
2008年 | 24篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 31篇 |
2004年 | 30篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1970年 | 2篇 |
1954年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1932年 | 2篇 |
排序方式: 共有629条查询结果,搜索用时 265 毫秒
61.
The aim of this paper is to study two problems in the framework of paracontact geometry of dimension \(3\) , namely, the class of parallel symmetric tensor fields of \((0, 2)\) -type and possible Lorentz Ricci solitons. We search for two types of Ricci solitons: the first when its potential vector field is exactly the characteristic vector field \(\xi \) of the paracontact structure and the second when the potential vector field is a paracontact-holomorphic one. For the former case we find all variants of Ricci solitons, expanding, steady and shrinking, and the fact that \(\xi \) is a conformal Killing vector field. A class of examples is completely discussed. 相似文献
62.
A mathematical two-phase model is used to numerically investigate physical and rheological effects on small, individual bubbles in high-viscosity liquids under pressure impact. It is found out that bubbles remain stable over time at high viscosity and surface tension. The steady case is considered and connected to the stability behavior of the bubble. An upper bound for the bubble radius is derived and the new equilibrium state of the bubble can be predicted by means of stability theorems of differential equations. Finally, the interaction of a limited number of well separated bubbles in an Hele-Shaw flow is mathematically analyzed to visualize and physically interpret their trajectories. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
63.
Michael Esseling Annamaria Zaltron Nicola Argiolas Giovanni Nava Jörg Imbrock Ilaria Cristiani Cinzia Sada Cornelia Denz 《Applied physics. B, Lasers and optics》2013,113(2):191-197
We investigate the applicability of highly reduced lithium niobate samples doped with iron for the use as optoelectronic tweezers. Increasing the reduction degree of Fe-doped lithium niobate is well known to increase the photoconductivity and reduce the writing time of internal space-charge fields. Based on our measurements of the photorefractive properties, we determine the optimal conditions for dielectrophoretic trapping and present the application of Fe-doped lithium niobate as optoelectronic tweezers. For higher reduction degrees, an unexpected decrease in the photovoltaic current density and the saturation space-charge field is reported. 相似文献
64.
65.
66.
67.
Petre Ionita Vasile Dinoiu Cornel Munteanu Ioana Maria Turcu Victorita Tecuceanu Traian Zaharescu Eliza Oprea Cornelia Ilie Dan Anghel Gabriela Ionita 《Chemical Papers》2015,69(6):872-880
The rosemary extract was encapsulated in polyethylene or in covalently-based network gels. The covalent gels were obtained by the reaction of isocyanate end-capped polyethylene glycol (PEG) with β-cyclodextrin or glycerol. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to evaluate the antioxidant activity (AA) of rosemary extract entrapped in polymeric structures and in ethanol or water solutions. The AA of the rosemary extract was determined using a DPPH radical for samples prepared in ethanol, and a water-soluble derivative, the sulphonated DPPH radical (DPPH-SO3Na), for the rosemary extract in water. Formulation of the rosemary extract in polymeric gels ensures a rapid release which determines the AA values similar to those in solution. 相似文献
68.
Raluca Dumitru Florica Manea Lavinia Lupa Cornelia Păcurariu Adelina Ianculescu Anamaria Baciu Sorina Negrea 《Journal of Thermal Analysis and Calorimetry》2017,128(3):1305-1312
Nanosized cobalt aluminate (CoAl2O4) was prepared by thermolysis of heteronuclear coordination compound, namely [Al2Co(C2O4)4(OH2)6]. The synthesized precursor was characterized by chemical analysis, vibrational spectra and thermal analysis. The cobalt aluminate obtained after a heating treatment of the precursor at 700 °C was characterized by IR, XRD, TEM coupled with SAED measurements. Two types of carbon-based electrodes, glassy carbon and boron-doped diamond electrodes were decorated with the obtained cobalt aluminate in order to enhance the electroanalytical performance for the tetracycline (TC) detection in the aqueous solutions. Cyclic voltammetry technique was used to determine the effect of the nanosized CoAl2O4 on the electrochemical oxidation of TC and as consequence, for TC detection at both carbon-based electrodes. The obtained cobalt aluminate exhibited the electrocatalytic activity toward TC detection in direct relation with the type of the carbon substrate, which allowed enhancing the electroanalytical parameters of TC detection in the aqueous solution. 相似文献
69.
70.
Shah Hussain Cornelia Pezzei Yüksel Güzel Matthias Rainer Christian W. Huck Günther K. Bonn 《Analytica chimica acta》2014
An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC–DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic acids (CQAs) and their metabolites in human plasma. The procedure demonstrated high recoveries for the standard compounds spiked at different concentrations. Cynarin and chlorogenic acid were recovered in the range of 81–86% and 78–83%, respectively. Caffeic acid was extracted in the excess of 89–92%, while ferulic acid and dihydroxyhydrocinnamic acid showed a recovery of 87–91% and 92–95%, respectively. The method was partially validated in accordance with FDA-Industry Guidelines for Bioanalytical Method Validation (2001). The presented scheme improves the clean-up efficacy of the methanol deproteinization, significantly reduces the matrix effects and provides a great analytical tool for the isolation of small molecules from human plasma. 相似文献