全文获取类型
收费全文 | 1464篇 |
免费 | 101篇 |
国内免费 | 13篇 |
专业分类
化学 | 962篇 |
晶体学 | 29篇 |
力学 | 68篇 |
数学 | 113篇 |
物理学 | 406篇 |
出版年
2024年 | 11篇 |
2023年 | 19篇 |
2022年 | 98篇 |
2021年 | 104篇 |
2020年 | 70篇 |
2019年 | 66篇 |
2018年 | 60篇 |
2017年 | 53篇 |
2016年 | 73篇 |
2015年 | 67篇 |
2014年 | 71篇 |
2013年 | 116篇 |
2012年 | 98篇 |
2011年 | 106篇 |
2010年 | 73篇 |
2009年 | 46篇 |
2008年 | 53篇 |
2007年 | 48篇 |
2006年 | 44篇 |
2005年 | 33篇 |
2004年 | 33篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有1578条查询结果,搜索用时 15 毫秒
101.
Impact of Linear Operator on the Convergence of HAM Solution: A Modified Operator Approach 下载免费PDF全文
S. T. Hussain S. Nadeem & M. Qasim 《advances in applied mathematics and mechanics.》2016,8(3):499-516
The linear operator plays an important role in the computational process of
Homotopy Analysis Method (HAM). In HAM frame any kind of linear operator can
be chosen to develop a solution. Hence, it is easy to introduce the modified/physical
parameter dependent linear operators. The effective use of these operators has been
judged through solving fluid flow problems. Modification in linear operators affects
the solution and improves the computational efficiency of HAM for larger values of
parameters. The convergence rate of the solution is rapid and several times higher
resulting in less computational time. 相似文献
102.
O.M. Hussain A.S. Swapnasmitha J. John R. Pinto 《Applied Physics A: Materials Science & Processing》2005,81(6):1291-1297
The structure and surface morphology of WO3 thin films deposited by a laser-ablation technique have been found to be strongly dependent on the deposition conditions and the nature of the substrate. By precisely controlling the substrate temperature and the oxygen partial pressure, amorphous, polycrystalline, nano-crystalline and iso-epitaxial WO3 thin films were successfully grown. The structure and surface morphological features of the films from X-ray diffraction and atomic force microscopy data are described in relation to the deposition conditions. PACS 81.15.Fg; 68.55.-a; 68.37.Ps 相似文献
103.
Biqun Chen Karthikeyan Rajagopal Fatemeh Parastesh Hamed Azarnoush Sajad Jafari Iqtadar Hussain 《理论物理通讯》2020,72(10):105003-28
The economic and financial systems consist of many nonlinear factors that make them behave as the complex systems. Recently many chaotic finance systems have been proposed to study the complex dynamics of finance as a noticeable problem in economics. In fact, the intricate structure between financial institutions can be obtained by using a network of financial systems. Therefore, in this paper, we consider a ring network of coupled symmetric chaotic finance systems, and investigate its behavior by varying the coupling parameters. The results show that the coupling strength and range have significant effects on the behavior of the coupled systems, and various patterns such as the chimera and multi-chimera states are observed. Furthermore, changing the parameters' values, remarkably influences on the oscillators attractors. When several synchronous clusters are formed, the attractors of the synchronized oscillators are symmetric, but different from the single oscillator attractor. 相似文献
104.
The characterization and accurate determination of the chloride content in cement/concrete is very important for the assessment of the durability and safety of a concrete structure. The available analytical techniques are relatively expensive and time consuming. In this study, a laser-induced breakdown spectroscopy (LIBS) system was used for determination of elemental composition in three different types of cement samples. The plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm on the cement samples. The concentrations of different elements of significance for structural stability in cement samples were determined. The evaluation of the potential and the capabilities of LIBS as a rapid tool for characterization of cement samples is discussed. The optimum LIBS setup and experimental conditions to detect and measure chloride in building materials are reported. The LIBS results were compared with the results obtained using a standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP–ES). The limits of detection were determined, and calibration curves were measured. The results of this investigation indicate the reliability of LIBS to characterize different cement samples and to assess the chloride content in these cements. 相似文献
105.
O.M. Hussain K. Srinivasa Rao K.V. Madhuri C.V. Ramana B.S. Naidu S. Pai J. John R. Pinto 《Applied Physics A: Materials Science & Processing》2002,75(3):417-422
Molybdenum trioxide thin films were prepared by reactive pulsed laser deposition on Corning 7059 glass substrates. The influence
of oxygen partial pressure and deposition temperature on the structure, surface morphology and optical properties of these
films was studied to understand the growth mechanism of MoO3 thin films. The films formed at 473 K in an oxygen partial pressure of 100 mTorr exhibited predominantly a (0k0) orientation,
corresponding to an orthorhombic layered structure of α-MoO3. The evaluated optical band gap of the films was 3.24 eV. The crystallite size increased with increase of deposition temperature.
The films formed at an oxygen partial pressure of pO2=100 mTorr and at a deposition temperature greater than 700 K exhibited both (0k0) and (0kl) orientations, representing α-β
mixed phases of MoO3. The films formed at an oxygen partial pressure less than 100 mTorr were found to be sub-stoichiometric with α-β mixed phases.
The investigation revealed the growth of polycrystalline and single-phase orthorhombic-layered-structure α-MoO3 thin films with composition nearly approaching the nominal stoichiometry at moderate substrate temperatures in an oxygen
partial pressure of 100 mTorr.
Received: 9 April 2001 / Accepted: 6 August 2001 / Published online: 17 October 2001 相似文献
106.
We have studied the magnetic and transport properties of Fe doped La0.65A0.35Mn0.95Fe0.05O3 (A = Ca, Sr, Pb, Ba) manganites. All the compositions show ferromagnetic/metal to paramagnetic/insulator transition (TC) except the Pb doped sample which is insulating and ferromagnetic (FM) in the entire temperature range. The magnetization and TC are decreased by decreasing the cation size on La site. The transition temperature and magnetic moment at 77 K is a maximum for Sr doped sample and is decreasing if we increase or decrease the cation size from Sr size. The maximum value of TC and magnetic moment for Sr based sample is most likely due to the closer ionic sizes of La and Sr as compared to the other dopants (Ca, Pb, and Ba). We observed a spin freezing type effect in the Pb doped sample below 120 K in resistivity, ac susceptibility and in magnetization. This suggests that the AFM interactions introduced by the Fe are most effective in the Pb doped composition leading to increased competition between the FM and AFM interactions. This FM and AFM interaction generates some degree of frustration leading to the appearance of spin glass like phase whose typical magnetic behavior is studied for small ion when the metallic like behavior is lost. 相似文献
107.
Nida Iqbal Rabia NazirAnila Asif Aqif Anwar ChaudhryMuhammad Akram Goh Yi FanAftab Akram Rashid AminSung Ha Park Rafaqat Hussain 《Current Applied Physics》2012,12(3):755-759
Polyvinyl alcohol (PVA) coated hydroxyapatite was deposited onto a 316L stainless steel substrate by electrophoretic deposition. Deposition was carried out in a methanol suspension at pH 5.5 using a graphite rod as an anode. Parameters such as PVA concentration, deposition voltage and time were optimized to achieve a homogeneous, crack-free adhesive coating. Techniques such as X-ray diffraction and Fourier transform infrared spectroscopy were used to study the phase composition of the coated materials and the stability of hydroxyapatite in the presence of PVA. 相似文献
108.
Iqtadar Hussain Tariq Shah Muhammad Asif Gondal Hasan Mahmood 《Nonlinear dynamics》2013,71(1-2):133-140
In this paper, we synthesize substitution boxes by the use of chaotic logistic maps in linear fractional transformation. In order to introduce randomness in the construction of S-boxes, the data from the chaotic system is used in linear fractional transformation to add additional unpredictable behavior. The proposed S-box is tested for its strength in encryption applications. The nonlinearity characteristic of the proposed S-box is studied, and the strength of the cipher is quantized in terms of this property. In addition, the behavior of bit changes at the output of the cipher in comparison with the input is also studied. Similarly, the input/output differential is also evaluated for different bit patterns. The results of statistical analyses show superior performance of the proposed S-boxes. 相似文献
109.
S.Nadeem Anwar Hussain M.Y.Malik T.Hayat 《应用数学和力学(英文版)》2009,30(10):1255-1262
This study derives the analytic solutions of boundary layer flows bounded by a shrinking sheet. With the similarity transformations, the partial differential equations are reduced into the ordinary differential equations which are then solved by the homotopy analysis method (HAM). Two-dimensional and axisymmetric shrinking flow cases are discussed. 相似文献
110.
Imran Hussain Syed Anastasia Braer Frank Fleck Jorge Lacayo-Pineda 《Soft Materials》2018,16(4):275-288
In the present study, a specific type of reinforcing resin behavior is investigated using various mechanical approaches as well as microscopic techniques such as transmission electron microscopy and atomic force microscopy. Based on these observations, it could be concluded that the reinforcing resin introduces a synergistic effect with carbon black in order to strengthen the system. This is implied since the percolation threshold is significantly reduced and the morphology of the filler aggregates changes toward higher compactness, i.e., an increase of volume-to-size ratio with the addition of resin. 相似文献