全文获取类型
收费全文 | 370篇 |
免费 | 13篇 |
专业分类
化学 | 183篇 |
力学 | 10篇 |
数学 | 107篇 |
物理学 | 83篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 31篇 |
2012年 | 13篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 5篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2001年 | 5篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1988年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1943年 | 3篇 |
1940年 | 3篇 |
1938年 | 3篇 |
1937年 | 6篇 |
1935年 | 4篇 |
1934年 | 5篇 |
1933年 | 7篇 |
1932年 | 8篇 |
1931年 | 4篇 |
1930年 | 10篇 |
1928年 | 3篇 |
1927年 | 4篇 |
1921年 | 3篇 |
1918年 | 7篇 |
1917年 | 8篇 |
1916年 | 5篇 |
1915年 | 13篇 |
排序方式: 共有383条查询结果,搜索用时 15 毫秒
1.
Henri de Maissin Philipp R. Groß Obaid Mohiuddin Dr. Moritz Weigt Luca Nagel Marvin Herzog Zirun Wang Robert Willing Dr. Wilfried Reichardt Dr. Martin Pichotka Dr. Lisa Heß Prof. Dr. Thomas Reinheckel Prof. Dr. Henning J. Jessen Prof. Dr. Robert Zeiser Prof. Dr. Michael Bock Prof. Dominik von Elverfeldt Prof. Dr. Maxim Zaitsev Dr. Sergey Korchak Dr. Stefan Glöggler Prof. Dr. Jan-Bernd Hövener Prof. Dr. Eduard Y. Chekmenev Prof. Dr. Franz Schilling Dr. Stephan Knecht Dr. Andreas B. Schmidt 《Angewandte Chemie (International ed. in English)》2023,62(36):e202306654
2.
In this experimental study a thorough analysis of the steady and unsteady flow field in a realistic transparent silicone lung
model of the first bifurcation of the upper human airways will be presented. To determine the temporal evolution of the flow
time-resolved particle-image velocimetry recordings were performed for a Womersley number range 3.3 ≤ α ≤ 5.8 and Reynolds
numbers of Re
D
= 1,050, 1,400, and 2,100. The results evidence a highly three-dimensional and asymmetric character of the velocity field
in the upper human airways, in which the influence of the asymmetric geometry of the realistic lung model plays a significant
role for the development of the flow field in the respiratory system. At steady inspiration, the flow shows independent of
the Reynolds number a large zone with embedded counter-rotating vortices in the left bronchia ensuring a continuous streamwise
transport into the lung. At unsteady flow the critical Reynolds number, which describes the onset of vortices in the first
bifurcation, is increased at higher Womersley number and decreased at higher Reynolds number. At expiration the unsteady and
steady flows are almost alike. 相似文献
3.
Dipl.-Ing. J. Groß-Weege Priv. Doz. Dr.-Ing. D. Weichert 《Archive of Applied Mechanics (Ingenieur Archiv)》1987,57(4):297-306
Übersicht Ein Finite-Element-Verfahren zur Berechnung von Einspiellastfaktoren elastisch-idealplastischer Scheiben auf der Grundlage des Melanschen Theorems wird vorgestellt. Berechnungsheispiele illustrieren die Methode.
On the numerical investigation of the shakedown of elastic-plastic disks under variable mechanical and thermal loads
Summary A finite element procedure for the calculation of shakedown loading factors of elastic-ideal plastic disks basing on Melan's theorem is presented. Sample calculations illustrate the method.相似文献
4.
G. Groβmann 《Isotopes in environmental and health studies》2013,49(7):268-270
Es wurde ein Trennverfahren ausgeabeitet, das es gestattet, die Aktivitätsausbeuten für Mono-, Di- und Triphenylarsenverbindungen, für Tetraphenylarsoniumverbindungen und für Pentaphenylarsen sowie für nicht organisch gebundenes Arsen in neutronenbestrahlten Tetraphenylarsoniumver erbindungen und in Pentaphenylarsen zu bestimmen. Als Trennmethoden werden Extraktion, Ionenaustauwsch und Al2O3-Chromatographic benutzt. Zur Reinigung und Ausbeutebestimmung von Di- und Triphenylarsenprodukten sowie von Tetraphenylarsonimverbindungen finden Kristallisations- bzw. Fällungsreaktionen Anwendung unter Ausnutzung des Prinzips der Isotopenverdünnungsanalyse. 相似文献
5.
6.
This paper deals with higher order accurate variational integrators for finite element systems. The variational integrator (VI) is based on higher order LAGRANGE polynomials as shape functions and a higher order GAUSSIAN quadrature rule. The goals of this paper are to implement a discrete gradient to preserve the balance of total energy and fulfill the constraints with the LAGRANGE multiplier method and a NEWTON-COTÊS quadrature rule. We show the calculation of bearing forces from the LAGRANGE multipliers, which are essential for the balance of total linear momentum and the balance of total angular momentum. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
This paper presents a basic endochronic plasticity model with isotropic hardening for small strain theory according to Valanis. The key point of this model is a convolution integral over an intrinsic time scale involving past values of the strain measure and a so-called memory kernel which leads to a smooth evolution equation for the internal variable. For the temporal discretization of the underlying constitutive equations and the resulting evolution equation we use higher order accurate variational integrators (VI). The remarkable feature is the fact that we approximate the position vector in terms of velocities according to partitioned Runge-Kutta methods (pRK). As a representative model problem serves a quasistatic, uniaxial tensile testing as well as a dynamic, elastoplastic cantilever beam with a smooth plasticity model according to the Valanis framework. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
A modern block cipher consists of round transformations, which are obtained by alternatively applying permutations (P-boxes) and substitutions (S-boxes). Clearly, the most important attribute of a block cipher is its security. However, with respect to the hardware implementation, a good block cipher has to have a reasonable complexity as well. In this paper, we study complexity of round transformations satisfying some basic security criteria. There are several ways to define the complexity of a round transformation, and to choose “necessary” security criteria. It turns out, that for our purpose, it is suitable to view a round transformation as a single Boolean function, not separating it into S-boxes and P-boxes. We require that the Boolean function F possesses some fundamental properties imposed on each block cipher for security reasons; namely, we require that the function is a strictly non-linear bijection and that it has a good diffusion. The total number of variables in the normal algebraic form of the component functions of F is taken as its complexity. We find the minimum complexity of such functions, and this way we establish a lower bound on complexity of all round transformations. To show that the lower bound is the best possible, we construct a round transformation F′ attaining the bound. We stress that it is not an aspiration of this paper to construct a round transformation which would be of practical use; F′ is useful only from the theoretical point of view. 相似文献
9.
We give sharp, necessary conditions on complete embedded CMC surfaces with three ends and an extra reflection symmetry. The
respective submoduli space is a two-dimensional variety in the moduli space of general CMC surfaces. Fundamental domains of
our CMC surfaces are characterized by associated great circle polygons in the three-sphere.
Received: 23 January 1998 / Revised version: 23 October 1998 相似文献
10.