全文获取类型
收费全文 | 101篇 |
免费 | 0篇 |
专业分类
化学 | 48篇 |
力学 | 11篇 |
数学 | 4篇 |
物理学 | 38篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 8篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1901年 | 1篇 |
排序方式: 共有101条查询结果,搜索用时 15 毫秒
71.
72.
The temperature-composition phase diagram of the HgTe—HgI2 pseudobinary system was determined between 25 and 670°C using differential scanning calorimetry, differential thermal analysis, Debye-Scherrer powder X-ray diffraction techniques, and metallographic analysis methods. Solid solutions of HgTe and HgI2 with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7±0.8 Mol-% HgI2 in HgTe at 501±5°C. The monoclinic intermediate phase Hg3Te2I2 is formed by a peritectic reaction upon cooling at 501±5°C, with the peritectic point at approximately 37±4 Mol-% HgI2. The previously unknown cubic phase Hg3TeI4 (a = 6.240±0.003 Å) is formed by a eutectoid reaction at 238±3°C and is stable up to 273±3°C, where it melts by a peritectic reaction with the peritectic point at approximately 79±3 Mol-% HgI2. Between Hg3TeI4 and HgI2 is a eutectic point at 82±3 Mol-% HgI2 and 250±3°C. The α to β transition of HgI2 at 133±3°C is independent of sample composition between 33.3 and 100 Mol-% HgI2. 相似文献
73.
The title compound selectively reduces acid chlorides to aldehydes under neutral conditions and aldehydes and ketones to alcohols in acidic media. 4--Butylcyclohexanone is reduced to the alcohol with a high degree of stereoselectivity (94:6). 相似文献
74.
Anderberg PI Turner JJ Evans KJ Hutchins LM Harding MM 《Dalton transactions (Cambridge, England : 2003)》2004,(11):1708-1714
The synthesis of racemic and optically pure ligand L, in which two 6,6'-disubstituted bipyridines are connected by methyleneoxy linkers to the molecular cleft dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione, is reported. In the presence of 2 equivalents of zinc(ii) trifluoromethansulfonate (+/-)- undergoes slow reversible coordination over 24 h to form a pair of enantiomeric [2 + 2] metallomacrocycles, [Zn2(+)L2](OTf)(4) and [Zn2(-)L2](OTf)(4) respectively, that contain either two (+)-L ligands or two (-)-L ligands. This assignment was confirmed by independent studies with either (+)-L or (-)-L which formed the same complexes but at a significantly faster rate (3 h), and circular dichroism spectra of [Zn2(+)L2](OTf)(4) and [Zn2(-)L2](OTf)(4) which gave signals of the same intensity with the opposite sign. Treatment of (+/-)-L or optically pure L with copper(I) showed rapid formation of a mixture of oligomers as well as the [2 + 2] metallomacrocycle. The complex Zn2L2(OTf)(4) exhibits slow exchange between two species on the NMR time scale at room temperature. The results are consistent with the formation of a library of metal complexes in which the zinc(ii) binds initially to the most accessible bipyridyl binding sites in (+/-)-. Equilibration over several hours results in self-recognition of enantiomeric ligands to form a pair of enantiomeric metallomacrocycles, which have been tentatively assigned as having the helical configuration. Slow exchange is attributed to the preference for both metal centres to adopt 6-coordinate geometries involving the linker oxygens, but are limited to exchanging 5-coordinate complexes due to the shape of the cleft and the short linker. 相似文献
75.
Berk SC Rohrer SP Degrado SJ Birzin ET Mosley RT Hutchins SM Pasternak A Schaeffer JM Underwood DJ Chapman KT 《Journal of combinatorial chemistry》1999,1(5):388-396
The tetradecapeptide somatostatin is widely distributed throughout the body and is thought to be involved with a variety of regulatory functions. Recently, five human somatostatin receptors (hSSTR1-5) have been cloned and characterized. Several selective peptidal agonists of the hSSTR receptors are known, and we sought to apply this information to the design of novel non-peptide small molecule ligands for each receptor. Initial computational methods identified a 200 nM murine SSTR2 active compound via a database search of our sample collection. A combinatorial library was designed around the structural class of the compound with the goal of rapidly developing this initial lead into the desired subtype-selective small molecules in order to characterize the pharmacology of each of the receptor subtypes. The library was synthesized using the resin-archive, iterative deconvolution format. The total number of unique compounds in the library was expected to be 131,670, present in 79 mixtures of 1330 or 2660 compounds per mixture. Through sequences of screening and mixture deconvolution, the components of selective and highly active (Ki = 50 pM to 200 nM) non-peptide small molecule ligands for somatostatin subtypes 1, 2, 4, and 5 were identified. In addition to discovering compounds with the desired activity and selectivity, useful structure/activity information was generated which can be used in the design of new compounds and second-generation combinatorial libraries. 相似文献
76.
Allylic acetates are reduced to alkenes by reductive displacement by hydride reagents via catalytic activation with Pd(0) complexes. In the absence of hydrides, allylic acetates afford conjugated dienes in DMSO solvent. 相似文献
77.
Jacopo Canton Ramis Örlü Cheng Chin Nicholas Hutchins Jason Monty Philipp Schlatter 《Flow, Turbulence and Combustion》2016,97(3):811-827
The present study reconsiders the control scheme proposed by Schoppa & Hussain (Phys. Fluids 10, 1049–1051 1998), using a new set of numerical simulations. The computations are performed in a turbulent channel at friction Reynolds numbers of 104 (the value employed in the original study) and 180. In particular, the aim is to better characterise the physics of the control as well as to investigate the optimal parameters. The former purpose lead to a re-design of the control strategy: moving from a numerical imposition of the mean flow to the application of a volume force. A comparison between the two is presented. Results show that the original method only gave rise to transient drag reduction. The forcing method, on the other hand, leads to sustained drag reduction, and thus shows the superiority of the forcing approach for all wavelengths investigated. A clear maximum efficiency in drag reduction is reached for the case with a viscous-scaled spanwise wavelength of the vortices of 1200, which yields a drag reduction of 18 %, as compared to the smaller wavelength of 400 suggested as the most efficient vortex in Schoppa & Hussain. Various turbulence statistics are considered, in an effort to elucidate the causes of the drag-reducing effect. For instance, a region of negative production was found, which is quite unusual for developed turbulent channel flow. 相似文献
78.
Ogg RJ Zou P Allen DN Hutchins SB Dutkiewicz RM Mulhern RK 《Magnetic resonance imaging》2008,26(4):504-512
Functional magnetic resonance imaging (fMRI) was performed in 30 healthy adults to identify the location, magnitude, and extent of activation in brain regions that are engaged during the performance of Conners' Continuous Performance Test (CPT). Performance on the task during fMRI was highly correlated with performance on the standard Conners' CPT in the behavioral testing laboratory. An extensive neural network was activated during the task that included the frontal, cingulate, parietal, temporal, and occipital cortices; the cerebellum and the basal ganglia. There was also a network of brain regions which were more active during fixation than task. The magnitude of activation in several regions was correlated with reaction time. Among regions that were more active during task, the overall volume of supratentorial activation and cerebellar activation was greater in the left hemisphere. Frontal activation was greater in dorsal than in ventral regions, and dorsal frontal activation was bilateral. Ventral frontal region and parietal lobe activation were greater in the right hemisphere. The volume of clusters of activation in the extrastriate ventral visual pathway was greater in the left hemisphere. This network is consistent with existing models of motor control, visual object processing and attentional control and may serve as a basis for hypothesis-driven fMRI studies in clinical populations with deficits in Conners' CPT performance. 相似文献
79.
Riley J. Petersen Brett J. Rozeboom Dr. Shalisa M. Oburn Nolan J. Blythe Tanner L. Rathje Javier A. Luna Steven K. Kibby Emily A. O'Brien Kayleigh G. Rohr Joshua R. Carpenter Taylor L. Sanders Andrew M. Johnson Dr. Kristin M. Hutchins Prof. Scott K. Shaw Prof. Leonard R. MacGillivray Prof. Jay Wm. Wackerly 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):1928-1930
A novel macrocyclic host molecule was synthesized that forms in a single step from commercially available starting materials. The core of the macrocycle backbone possesses two quinone rings and, thus, it is redox-active. Host–guest binding involving the clip-shaped cavity indicates selective binding of pyridine N-oxides based on the electron density of and steric bulk around the anionic oxygen. 相似文献
80.
Endrikat S. Modesti D. MacDonald M. García-Mayoral R. Hutchins N. Chung D. 《Flow, Turbulence and Combustion》2021,107(1):1-29
Flow, Turbulence and Combustion - Riblets reduce skin-friction drag until their viscous-scaled size becomes large enough for turbulence to approach the wall, leading to the breakdown of... 相似文献