全文获取类型
收费全文 | 1805篇 |
免费 | 64篇 |
国内免费 | 3篇 |
专业分类
化学 | 1483篇 |
晶体学 | 11篇 |
力学 | 21篇 |
数学 | 179篇 |
物理学 | 178篇 |
出版年
2023年 | 15篇 |
2022年 | 47篇 |
2021年 | 44篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 21篇 |
2017年 | 26篇 |
2016年 | 55篇 |
2015年 | 44篇 |
2014年 | 44篇 |
2013年 | 110篇 |
2012年 | 115篇 |
2011年 | 138篇 |
2010年 | 96篇 |
2009年 | 71篇 |
2008年 | 128篇 |
2007年 | 126篇 |
2006年 | 105篇 |
2005年 | 94篇 |
2004年 | 99篇 |
2003年 | 56篇 |
2002年 | 61篇 |
2001年 | 18篇 |
2000年 | 25篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1956年 | 3篇 |
排序方式: 共有1872条查询结果,搜索用时 15 毫秒
71.
Stieghorst Christian Hampel Gabriele Karches Barbara Krenckel Patricia Kudějová Petra Plonka Christian Révay Zsolt Riepe Stephan Welter Katharina Wiehl Norbert 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):307-313
Journal of Radioanalytical and Nuclear Chemistry - For the optimization of the manufacturing process of multicrystalline silicon (mc-Si) for solar cells in order to reduce energy consumption and... 相似文献
72.
Residual‐based stabilization of the finite element approximation to the acoustic perturbation equations for low Mach number aeroacoustics
下载免费PDF全文
![点击此处可从《国际流体数值方法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Oriol Guasch Patricia Sánchez‐Martín Arnau Pont Joan Baiges Ramon Codina 《国际流体数值方法杂志》2016,82(12):839-857
The acoustic perturbation equations (APE) are suitable to predict aerodynamic noise in the presence of a non‐uniform mean flow. As for any hybrid computational aeroacoustics approach, a first computational fluid dynamics simulation is carried out from which the mean flow characteristics and acoustic sources are obtained. In a second step, the APE are solved to get the acoustic pressure and particle velocity fields. However, resorting to the finite element method (FEM) for that purpose is not straightforward. Whereas mixed finite elements satisfying an appropriate inf–sup compatibility condition can be built in the case of no mean flow, that is, for the standard wave equation in mixed form, these are difficult to implement and their good performance is yet to be checked for more complex wave operators. As a consequence, strong simplifying assumptions are usually considered when solving the APE with FEM. It is possible to avoid them by resorting to stabilized formulations. In this work, a residual‐based stabilized FEM is presented for the APE at low Mach numbers, which allows one to deal with the APE convective and reaction terms in its full extent. The key of the approach resides in the design of the matrix of stabilization parameters. The performance of the formulation and the contributions of the different terms in the equations are tested for an acoustic pulse propagating in sheared‐solenoidal mean flow, and for the aeolian tone generated by flow past a two‐dimensional cylinder. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
73.
Patricia Dähmlow Torsten Trittel Kathrin May Kirsten Harth Ralf Stannarius 《Liquid crystals》2018,45(7):993-1003
Elongated freely floating smectic bubbles are observed during their relaxation to equilibrium sphere shape. Unlike soap bubbles that perform weakly damped oscillations into equilibrium, this relaxation is overdamped in smectics by internal structure reorganisation processes. The bubble area reduction of centimetre-sized freely floating bubbles with few nanometres film thickness is recorded with high-speed optical imaging in microgravity and analysed quantitatively. We find a nearly linear reduction of the film area with time, driven by capillary forces and inhibited by smectic layer reorganisations. Characteristic times are in the milliseconds range, with little correlation to the film thickness and bubble size. Instead, the homogeneity of the films and the number and sizes of islands of excess layers that spontaneously form on the films appear to have crucial influence on the dynamics. The efficiency of this process sets the time scale of the film area shrinkage. We discuss the limitations of a minimalistic model that captures smectic layer reorganisation processes. 相似文献
74.
75.
76.
Michèle Postel Félix Tomi Henri Li Kam Wah Laurence Mordenti Patricia Guillaume 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):453-457
Abstract Fe(NO)2XL and Fe(NO)X2L nitrosyl iron complexes, X = Cl, I, and L = HMPA, dppe, PPh3, activate molecular O2 to yield nitrato complexes. The phosphorous ligand is decisive for the oxidative power of these nitrates: with HMPA or dppe, oxygen transfer occurs only to phosphines. On going from HMPA to PPh3 the single nitrato complex obtained, Fe(NO)2X(OPPh3)2 selectively epoxidizes cyclohexene, and this is the first example of oxygen transfer from a nitrato ligand to an olefin. 相似文献
77.
78.
79.
80.
It has been shown that tert-butyldimethylsilylated (Z) 2-carboethoxymethylene cycloalkanols are readily desilylated with concomitant cyclization to give the corresponding butenolides. The (E) isomers are desilylated, but not cyclized under these conditions. 相似文献