全文获取类型
收费全文 | 245篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 150篇 |
晶体学 | 8篇 |
力学 | 5篇 |
数学 | 56篇 |
物理学 | 29篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有248条查询结果,搜索用时 46 毫秒
241.
In the present paper we classify all surfaces in $
\mathbb{E}
$
\mathbb{E}
3 with a canonical principal direction. Examples of this type of surfaces are constructed. We prove that the only minimal surface
with a canonical principal direction in the Euclidean space $
\mathbb{E}
$
\mathbb{E}
3 is the catenoid. 相似文献
242.
Ocimum basilicum L., popularly known as sweet basil, is a Lamiaceae species whose essential oil is mainly composed of monoterpenes, sesquiterpenes and phenylpropanoids. The contents of these compounds can be affected by abiotic and biotic factors such as infections caused by viruses. The main goal of this research was an investigation of the effects of viral infection on the essential oil profile of common basil. Seeds of O. basilicum L. cv. Genovese were sowed and kept in a greenhouse. Plants presenting two pairs of leaves above the cotyledons were inoculated with an unidentified virus isolated from a field plant showing chlorotic yellow spots and foliar deformation. Essential oils of healthy and infected plants were extracted by hydrodistillation and analyzed by GCMS. Changes in essential oil composition due to viral infection were observed. Methyleugenol and p-cresol,2,6-di-tert-butyl were the main constituents. However, methyleugenol contents were significantly decreased in infected plants. 相似文献
243.
Filip D. Macocinschi D. Paslaru E. Munteanu B. S. Dumitriu R. P. Lungu M. Vasile C. 《Journal of nanoparticle research》2014,16(11):1-17
Journal of Nanoparticle Research - Bionanocomposite membranes based on polyurethane (PU), extracellular matrix (EM), and silver nanoparticles (AgNPs) were prepared by applying both solvent casting... 相似文献
244.
Mohamed?Jleli Marian?Ioan?Munteanu Ana?Irina?NistorEmail author 《Results in Mathematics》2015,67(1-2):125-134
In this paper we classify magnetic trajectories γ in \({{\mathbb{R}}^{2N+1}}\) endowed with a canonical quasi-Sasakian structure, corresponding to a magnetic field proportional to the fundamental 2-form. We prove that they are helices of order 5 and we show that there exists a totally geodesic \({{\mathbb{R}}^5}\) in \({\mathbb{R}^{2N+1}}\) such that γ lies in \({{\mathbb{R}}^5}\). Moreover, the quasi-Sasakian structure of \({{\mathbb{R}}^5}\) is that induced from the ambient manifold. 相似文献
245.
Paolo Ugo Ligia M. Moretto Morena Silvestrini Francisco C. Pereira 《International journal of environmental analytical chemistry》2013,93(9):747-759
Procedures for the preparation and characterisation of ensembles of gold nanodisk electrodes (NEE) of 30 nm diameter are presented, in particular focusing on improvements in the signal/background current ratios and detection limits with respect to the electrochemical oxidation of iodide and its analytical determination in water samples. At NEEs iodide undergoes a quasi-reversible diffusion controlled oxidation with a slight shift in E 1/2 values and slightly higher peak to peak separation with respect to conventional gold disk electrodes. The double layer charging current at the NEE is significantly lower than at conventional electrodes so that the detection limit (DL) by cyclic voltammetry with NEEs in tap water is significantly lower than DL at the Au-disk millimetre-sized electrode (DL 0.3 µM at NEE vs. 4 µM for Au-disk). Finally, it is shown that NEEs in combination with square wave voltammetry can be applied for the direct determination of iodide in water samples from the lagoon of Venice, with a detection limit of 0.10 µM. 相似文献
246.
Deodato Radíc Claudia Dain Alejandra Opazo Ligia Gargello 《Macromolecular Symposia》1992,58(1):209-213
The synthesis of poly(di-2-chloroethyl itaconate) (PD2CEI) and poly(di-3-chloropropyl itaconate) (PD3CPI) was carried out. The dilute solution behaviour of these polymers in tetrahydrofuran and chloroform at 298 K has been studied, by viscometry, membrane osmometry, and size-exclusion chromatography (SEC) measurements. The Kuhn-Mark-Houwink-Sakurada relationships were established. The flexibility factors σ and C∞ and the thermodynamic parameters B were calculated using the Stockmayer-Fixman equation. The results obtained are compared with those found for the corresponding poly(methacrylates) and the poly(dialkyl itaconates), and discussed in terms of specific influence of the chlorine incorporated in the side chain. 相似文献
247.
Anca Suteanu-Simulescu Mirela Sarbu Raluca Ica Ligia Petrica Alina Diana Zamfir 《Electrophoresis》2023,44(5-6):501-520
The expression of gangliosides in central nervous system is a few times higher than in the extraneural tissue, a characteristic highlighting their major role at this level. Although in very low amounts, gangliosides are ubiquitously distributed in body fluids too, where, depending on many factors, including pathological states, their composition fluctuates, thus having diagnostic value. Ganglioside investigation in biological fluids, which, except for cerebrospinal fluid (CSF), may be sampled noninvasively, was for years impeded by the limited sensitivity of the analytical instrumentation available in glycomics. However, because the last decade has witnessed significant developments in biological mass spectrometry (MS) and the hyphenated separation techniques, marked by a major increase in sensitivity, reproducibility, and data reliability, ganglioside research started to be focused on biofluid analysis by separation techniques coupled to MS. In this context, our review presents the achievements in this emerging field of gangliosidomics, with a particular emphasis on modern liquid chromatography (LC), thin-layer chromatography, hydrophilic interaction LC, and ion mobility separation coupled to high-performance MS, as well as the results generated by these systems and allied experimental procedures in profiling and structural analysis of gangliosides in healthy or diseased body fluids, such as CSF, plasma/serum, and milk. 相似文献
248.
Blends of poly(monoitaconates)b) containing different side chain structures with poly(N-vinyl-2-pyrrolidone) (PVP) of three different weight-average molecular weights (M̄w) were studied by thermomechanical analysis. Blends containing PVP of M̄w =10000 shows a monotonous variation of the coefficient of linear expansion α against composition but PVP samples of higher molecular weights present a minimum which is attributed to polymer-polymer complex due to strong specific interactions. 相似文献