全文获取类型
收费全文 | 240篇 |
免费 | 3篇 |
专业分类
化学 | 157篇 |
数学 | 21篇 |
物理学 | 65篇 |
出版年
2021年 | 2篇 |
2019年 | 3篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 13篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1965年 | 1篇 |
1959年 | 1篇 |
1941年 | 1篇 |
1936年 | 1篇 |
1927年 | 1篇 |
1922年 | 1篇 |
1917年 | 1篇 |
1910年 | 3篇 |
1909年 | 1篇 |
1908年 | 1篇 |
1905年 | 4篇 |
1904年 | 2篇 |
1903年 | 2篇 |
1902年 | 2篇 |
1900年 | 1篇 |
1890年 | 4篇 |
1884年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 15 毫秒
11.
Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2388-2391
12.
Fontaine P Goldmann M Muller P Fauré MC Konovalov O Krafft MP 《Journal of the American Chemical Society》2005,127(2):512-513
We report the first direct evidence for the formation of circular surface micelles (hemimicelles) on the surface of water. These highly monodisperse 30 nm hemimicelles, made from a semifluorinated alkane deposited as a Langmuir monolayer, form organized hexagonal arrays as determined by small-angle X-ray diffraction conducted directly on the water surface at grazing incidence. 相似文献
13.
The unprecedented reactivity of Co(4)(CO)(12) with enynes under aqueous conditions, representing the development of a mild and simple aqueous-phase cobalt-catalyzed PK reaction protocol, is described herein. 相似文献
14.
Supershell structure in alkali metal nanowires 总被引:1,自引:0,他引:1
Nanowires are formed by indenting and subsequently retracting two pieces of sodium metal. Their cross section gradually reduces upon retraction and the diameters can be obtained from the conductance. In previous work we have demonstrated that when one constructs a histogram of diameters from large numbers of indentation-retraction cycles such histograms show a periodic pattern of stable nanowire diameters due to shell structure in the conductance modes. Here, we report the observation of a modulation of this periodic pattern, in agreement with predictions of a supershell structure. 相似文献
15.
Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Halling AM Jedicke R Karchin PE Kwan S Leuking LH Mantsch PM de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review D: Particles and fields》1994,49(9):R4317-R4320
16.
Alves GA Amato S Anjos JC Appel JA Bracker SB Cremaldi LM Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Kaplan D Karchin PE Kwan S Leedom I Lueking LH Luste GJ Mantsch PM de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Rafatian A dos Reis AC Reucroft S Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wu Z 《Physical review letters》1993,70(6):722-725
17.
Tricyclic skeletons have been generated from acyclic enyne precursors by using an intramolecular Pauson-Khand reaction in combination with aldol, Michael and alkylation reactions. 相似文献
18.
Clara Stiebing Christian Matthäus Christoph Krafft Andrea-Anneliese Keller Karina Weber Stefan Lorkowski Jürgen Popp 《Analytical and bioanalytical chemistry》2014,406(27):7037-7046
Macrophages are phagocytic cells which are involved in the non-specific immune defense. Lipid uptake and storage behavior of macrophages also play a key role in the development of atherosclerotic lesions within walls of blood vessels. The allocation of exogenous lipids such as fatty acids in the blood stream dictates the accumulation and quantity of lipids within macrophages. In case of an overexposure, macrophages transform into foam cells because of the large amount of lipid droplets in the cytoplasm. Raman micro-spectroscopy is a powerful tool for studying single cells due to the combination of microscopic imaging with spectral information. With a spatial resolution restricted by the diffraction limit, it is possible to visualize lipid droplets within macrophages. With stable isotopic labeling of fatty acids with deuterium, the uptake and storage of exogenously provided fatty acids can be investigated. In this study, we present the results of time-dependent Raman spectroscopic imaging of single THP-1 macrophages incubated with deuterated arachidonic acid. The polyunsaturated fatty acid plays an important role in the cellular signaling pathway as being the precursor of icosanoids. We show that arachidonic acid is stored in lipid droplets but foam cell formation is less pronounced as with other fatty acids. The storage efficiency in lipid droplets is lower than in cells incubated with deuterated palmitic acid. We validate our results with gas chromatography and gain information on the relative content of arachidonic acid and its metabolites in treated macrophages. These analyses also provide evidence that significant amounts of the intracellular arachidonic acid is elongated to adrenic acid but is not metabolized any further. The co-supplementation of deuterated arachidonic acid and deuterated palmitic acid leads to a non-homogenous storage pattern in lipid droplets within single cells. Figure a
? 相似文献
19.
This study assessed the diagnostic potential of Raman spectroscopic mapping by evaluating its ability to distinguish between normal brain tissue and the human intracranial tumors gliomas and meningeomas. Seven Raman maps of native specimens were collected ex vivo by a Raman spectrometer with 785 nm excitation coupled to a microscope with a motorized stage. Variations within each Raman map were analyzed by cluster analysis. The dependence of tissue composition on the tissue type in cluster averaged Raman spectra was shown by linear combinations of reference spectra. Normal brain tissue was found to contain higher levels of lipids, intracranial tumors have more hemoglobin and lower lipid to protein ratios, meningeomas contain more collagen with maximum collagen content in normal meninges. One sample was studied without freezing. Whereas tumor regions did not change significantly, spectral changes were observed in the hemoglobin component after snap freezing and thawing to room temperature. The results constitute a basis for subsequent Raman studies to develop classification models for diagnosis of brain tissue. 相似文献
20.