全文获取类型
收费全文 | 965篇 |
免费 | 101篇 |
国内免费 | 177篇 |
专业分类
化学 | 185篇 |
晶体学 | 3篇 |
力学 | 545篇 |
综合类 | 27篇 |
数学 | 141篇 |
物理学 | 342篇 |
出版年
2023年 | 11篇 |
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 23篇 |
2019年 | 23篇 |
2018年 | 23篇 |
2017年 | 25篇 |
2016年 | 44篇 |
2015年 | 37篇 |
2014年 | 52篇 |
2013年 | 68篇 |
2012年 | 44篇 |
2011年 | 38篇 |
2010年 | 40篇 |
2009年 | 51篇 |
2008年 | 41篇 |
2007年 | 63篇 |
2006年 | 53篇 |
2005年 | 53篇 |
2004年 | 51篇 |
2003年 | 51篇 |
2002年 | 44篇 |
2001年 | 43篇 |
2000年 | 27篇 |
1999年 | 38篇 |
1998年 | 23篇 |
1997年 | 25篇 |
1996年 | 27篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1243条查询结果,搜索用时 15 毫秒
221.
窦华书 《应用数学和力学(英文版)》2014,35(5):541-548
For the stability problem of homogeneous shear flows in sea straits of arbitrary cross section, a sufficient condition for stability is derived under the condition of inviscid flow. It is shown that there is a critical wave number, and if the wave number of a normal mode is greater than this critical wave number, the mode is stable. 相似文献
222.
223.
本文中通过对PTFE纤维/芳纶纤维混合编织衬垫分别进行稀土处理和丙酮处理,研究了在倾斜摆动条件下衬垫改性对自润滑关节轴承摩擦学性能的影响,并用扫描电子显微镜(SEM)以及三维形貌仪分析了衬垫磨损表面微观形貌.研究结果表明:与未经改性处理衬垫的轴承相比,经稀土处理和丙酮处理后自润滑关节轴承减磨耐磨性能均得到提高,其中在高摆频工况下,衬垫经稀土处理后自润滑关节轴承减摩耐磨性能得到更大程度的提高;稀土处理轴承衬垫仅出现轻微黏着磨损,这是由于稀土处理过程增强了衬垫层的自润滑功能. 相似文献
224.
The space-time evolution of the (1+1)-dimensional viscous hydrodynamics with an initial quark-gluon plasma (QGP) produced in ultrarelativistic heavy ion collisions is studied numerically. The particle-emitting sources undergo a crossover transition from the QGP to hadronic gas. We take into account a usual shear viscosity for the strongly coupled QGP as well as the bulk viscosity which increases significantly in the crossover region. The two-pion Hanbury-Brown-Twiss (HBT) interferometry for the viscous hydrodynamic sources is performed. The HBT analyses indicate that the viscosity effect on the two-pion HBT results is small if only the shear viscosity is taken into consideration in the calculations. The bulk viscosity leads to a larger transverse freeze-out configuration of the pion-emitting sources, and thus increases the transverse HBT radii. The results of the longitudinal HBT radius for the source with Bjorken longitudinal scaling are consistent with the experimental data. 相似文献
225.
In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market. 相似文献
226.
《Analytical letters》2012,45(9):1801-1808
Abstract In this paper, we demonstrate the microelectrode electrochemistry of a simple electroactive probe (ferrocene) in SDS/n‐C4H9OH/H2O microemulsion systems. The oxidation of ferrocene within the microemulsion environment was carried out at a Pt microelectrode using a three‐electrode assembly with a Pt wire acting as an auxiliary electrode and an Ag wire as the pseudo‐reference electrode. Excellent Nernstian electrochemical responses were observed. The well‐defined reversible electrochemical responses facilitated the measurement of the self‐diffusion coefficient of microemulsion droplets and introduced the possibility of probing the structural changes of microemulsion systems. 相似文献
227.
228.
Zhaoli Guo & Kun Xu 《advances in applied mathematics and mechanics.》2009,1(3):391-401
Recently Brenner [Physica A 349, 60 (2005)] proposed a
modified Navier-Stokes set of equations. Based on some theoretical
arguments and some limited experiments, the model is expected to be
able to describe flows with a finite Knudsen number. In this work,
we apply this model to the plane Poiseuille flow driven by a force,
and compare the results with the Direct Simulation Monte Carlo
(DSMC) measurements. It is found that Brenner's model is inadequate
for flows with a finite Knudsen number. 相似文献
229.
This work reports a numerical study undertaken to investigate the dynamic response of a rotor supported by two turbulent flow
model journal bearings with nonlinear suspension and lubricated with couple stress fluid under quadratic damping. This may
be the first time that analysis of rotor-bearing system considered the quadratic damping effect. The dynamic response of the
rotor center and bearing center are studied. The analysis methods employed in this study are inclusive of the dynamic trajectories
of the rotor center and bearing center, power spectra, Poincaré maps and bifurcation diagrams. The maximum Lyapunov exponent
analysis is also used to identify the onset of chaotic motion. The modeling results provide some useful insights into the
design and development of rotor-bearing system for rotating machinery that operates at highly rotational speed and highly
nonlinear regimes. 相似文献
230.
Effects of axial preload of ball bearing on the nonlinear dynamic characteristics of a rotor-bearing system 总被引:2,自引:0,他引:2
This research studies the effects of axial preload on nonlinear dynamic characteristics of a flexible rotor supported by angular
contact ball bearings. A dynamic model of ball bearings is improved for modeling a five-degree-of-freedom rotor bearing system.
The predicted results are in good agreement with prior experimental data, thus validating the proposed model. With or without
considering unbalanced forces, the Floquet theory is employed to investigate the bifurcation and stability of system periodic
solution. With the aid of Poincarè maps and frequency response, the unstable motion of system is analyzed in detail. Results
show that the effects of axial preload applied to ball bearings on system dynamic characteristics are significant. The unstable
periodic solution of a balanced rotor bearing system can be avoided when the applied axial preload is sufficient. The bifurcation
margins of an unbalanced rotor bearing system enhance markedly as the axial preload increases and relates to system resonance
speed. 相似文献