全文获取类型
收费全文 | 132篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
化学 | 51篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 51篇 |
物理学 | 31篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 484 毫秒
81.
Marco Franchi Marilisa Quaranta Maria Macciocca Viviana De Pasquale Vittoria Ottani Alessandro Ruggeri 《Micron (Oxford, England : 1993)》2009,40(3):370-377
Tendons and ligaments have similar but slightly different structure and composition. Crimps of tendons and ligaments are morphological structures related to the elastic functional properties of these connective tissues. Aim of this study was to investigate the morphological arrangement of collagen fibres, fibrils and crimping pattern of suprapatellar (rectus femoris tendon-RFT and vastus intermedius tendon-VIT) and infrapatellar connective tissues (patellar ligament-PL) to relate their structural aspects to their common function role of leg extension. RFT, VIT and PL were removed from knees of Sprague–Dawley rats and light and electron microscopy (TEM and SEM) performed. Sagittal sections showed that collagen array and crimping pattern were similar in RFT and PL but differed from VIT. Morphometric analysis confirmed that crimp number was about the same in RFT and PL (5.4 ± 1.4 and 6.1 ± 2.8 respectively), but it was almost three times higher in VIT (14.5 ± 4.7). Similarly crimp top angle in RFT and PL (141.5 ± 15.0° and 146.2 ± 12.2° respectively) was significantly higher than in VIT (122.3 ± 14.8°) and the crimp base length was more than twice as wide in RFT (75.5 ± 22.6 μm) and PL (72.3 ± 28.9 μm) than in VIT (36 ± 14.1 μm). The smaller, fewer and most crimped crimps in VIT show that this tendon has a greater elastic recoil and responds to higher forces as among quadriceps muscles the vastus intermedius belly contributes the most during knee extension. By contrast, RFT acting as a “stopper” tendon also plays a ligament role by limiting an excessive flexion of the joint during postural rest position of the knee. 相似文献
82.
Annalisa Baldi Bruno Franchi 《Calculus of Variations and Partial Differential Equations》2012,43(1-2):211-229
Carnot groups (connected simply connected nilpotent stratified Lie groups) can be endowed with a complex (E 0 * , d c ) of “intrinsic” differential forms. In this paper we prove that, in a free Carnot group of step κ, intrinsic 1-forms as well as their intrinsic differentials d c appear naturally as limits of usual “Riemannian” differentials d ε , ε >?0. More precisely, we show that L 2-energies associated with ε ?κ d ε on 1 forms Γ-converge, as ε → 0, to the energy associated with d c . 相似文献
83.
Structural Changes of a Doubly Spin‐Labeled Chemically Driven Molecular Shuttle Probed by PELDOR Spectroscopy
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Paola Franchi Valentina Bleve Prof. Dr. Elisabetta Mezzina Christian Schäfer Giulio Ragazzon Dr. Marco Albertini Prof. Donatella Carbonera Prof. Dr. Alberto Credi Prof. Marilena Di Valentin Prof. Marco Lucarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(26):8745-8750
Gaining detailed information on the structural rearrangements associated with stimuli‐induced molecular movements is of utmost importance for understanding the operation of molecular machines. Pulsed electron–electron double resonance (PELDOR) was employed to monitor the geometrical changes arising upon chemical switching of a [2]rotaxane that behaves as an acid–base‐controlled molecular shuttle. To this aim, the rotaxane was endowed with stable nitroxide radical units in both the ring and axle components. The combination of PELDOR data and molecular dynamic calculations indicates that in the investigated rotaxane, the ring displacement along the axle, caused by the addition of a base, does not alter significantly the distance between the nitroxide labels, but it is accompanied by a profound change in the geometry adopted by the macrocycle. 相似文献
84.
N-benzyl-tert-butyl nitroxide derivatives substituted at the aromatic ring form host-guest inclusion complexes with β-and γ-cyclodextrin. They were employed as probes to assess substituent effects on the geometry of the complex and on the kinetics of this complexation by combining EPR and (1)H NMR data. 相似文献
85.
The purpose of this article is to introduce and study a relativistic motion whose acceleration, in proper time, is given by a white noise. We deal with general relativity and consider more closely the problem of the asymptotic behavior of paths in the Schwarzschild geometry example. © 2006 Wiley Periodicals, Inc. 相似文献
86.
We give examples of discontinuous solutions and of unbounded solutions of linear isotropic degenerate elliptic equations. Discontinuous solutions exist even when both the maximum eigenvalue and the inverse of the minimum eigenvalue of the matrix of the coefficients are in the intersection of all the Lp spaces. 相似文献
87.
Buoyancy driven flows of two Bingham fluids in an inclined ductare considered, providing a simplified model for many oilfieldcementing processes. The flows studied are near-uniaxial andstratified, with the heavy fluid moving down the incline, displacingthe lighter fluid upwards. Existence and uniqueness resultsare obtained for quite general flows and for those which satisfyan axial flow rate constraint. Parametric dependence of thesolutions on the axial pressure gradient is studied. Flows whichsatisfy a zero net axial flow constraint result from an axialpressure gradient which minimizes the viscous dissipation, butnot the plastic dissipation. A regularization method is usedto compute solutions to these problems for (more or less) arbitraryfluid-fluid interfaces and duct-cross sections. Examples relatedto a number of practical applications are presented. 相似文献
88.
Vittoria Petrillo Giorgia Alberti Luca Celardo Francesco Cerutti Silvano Franchi Vittorio Mariani 《Central European Journal of Physics》2006,4(2):196-209
The effect of a position measurement on one component of a two-particle wave packet in a regularized space-momentum entangled
state is analyzed. The wave packet interacts in the physical space with a potential barrier. When a position or momentum measurement
is performed on one particle, a consequent strong modification of the dynamics of the other particle occurs. 相似文献
89.
We calculate the shrinkage of the gaps between the different subbands of a quantum well induced by the presence of a photo-excited electron-hole plasma. The reduction of the higher gaps is found to be almost as strong as that of the fundamental gap. We discuss the importance of the interactions between the different subbands. Our theoretical results compare well with optical transmission experiments. 相似文献
90.
Optical absorption and thermoluminescence measurements have been performed on single crystals of ZnIn2S4. An absorption edge and a distribution of traps which depend exponentially on the radiation energy with the same ‘slope’, have been found. These results provide evidence for the existence of a considerable amount of intrinsic disorder in this compound, and allow one to relate the discussion to the wider problem of the optical properties of amorphous semiconductors. 相似文献