全文获取类型
收费全文 | 1120篇 |
免费 | 562篇 |
国内免费 | 93篇 |
专业分类
化学 | 125篇 |
晶体学 | 26篇 |
力学 | 282篇 |
综合类 | 15篇 |
数学 | 125篇 |
物理学 | 1202篇 |
出版年
2024年 | 8篇 |
2023年 | 29篇 |
2022年 | 75篇 |
2021年 | 62篇 |
2020年 | 59篇 |
2019年 | 72篇 |
2018年 | 42篇 |
2017年 | 64篇 |
2016年 | 97篇 |
2015年 | 70篇 |
2014年 | 100篇 |
2013年 | 105篇 |
2012年 | 90篇 |
2011年 | 90篇 |
2010年 | 63篇 |
2009年 | 65篇 |
2008年 | 72篇 |
2007年 | 77篇 |
2006年 | 75篇 |
2005年 | 50篇 |
2004年 | 47篇 |
2003年 | 54篇 |
2002年 | 42篇 |
2001年 | 34篇 |
2000年 | 33篇 |
1999年 | 30篇 |
1998年 | 25篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 10篇 |
1992年 | 2篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 5篇 |
排序方式: 共有1775条查询结果,搜索用时 546 毫秒
991.
992.
993.
本文将基于Hellinger-Reissner广义变分原理,提出一种分析复合材料缠绕壳结构应力场分析的混合状态Hamilton元半解析法.该方法在周向面内采用有限元离散;而沿径向对状态方程进行解析求解.在求解过程中,采用了传递矩阵技术,以保证层间位移和应力的连续性,并建立了缠绕结构的内、外表面状态变量之间的关系.为此,不论缠绕结构的层数有多少,最后都归结为求解缠绕结构内、外表面未知量.同常规位移有限元法相比,此方法大大地降低了求解未知量的数目.文中还采用Chang F K提出的复合材料缠绕结构的破坏准则,对一在服役工况下具有金属内衬的复合材料缠绕壳典型结构进行了强度校核. 相似文献
994.
A variational formulation for a vibroacoustic problem of a membrane and a viscothermal fluid is investigated in this paper. The formulation combines a variational formulation by integral equations of the fluid, that takes into account the acoustic and entropic waves coupling, with a variational formulation of the membrane. The formulation has been implemented numerically for the problems with axisymmetric geometry. The numerical results are compared to the analytical solution for a circular membrane coupled to a cylindrical cavity filled with air. These results show the validity of numerical implementation and illustrate the thermal effects of air on the membrane-cavity system modes in the micro cavities cases. 相似文献
995.
WAVE SUPERPOSITION METHOD BASED ON VIRTUAL SOURCE BOUNDARY WITH COMPLEX RADIUS VECTOR FOR SOLVING ACOUSTIC RADIATION PROBLEMS 总被引:1,自引:0,他引:1
XiangYu HuangYuying MaXiaoqiang 《Acta Mechanica Solida Sinica》2004,17(1):12-19
By virtue of the comparability between the wave superposition method and the dynamic analysis of structures, a general format for overcoming the non-uniqueness of solution induced by the wave superposition method at the eigenfrequencies of the corresponding interior problems is proposed. By adding appropriate damp to the virtual source system of the wave superposition method, the unique solutions for all wave numbers can be ensured. Based on this thought, a novel method-wave superposition method with complex radius vector is constructed. Not only is the computational time of this method approximately equal to that of the standard wave superposition method, but also the accuracy is much higher compared with other correlative methods. Finally, by taking the pulsating sphere and oscillating sphere as examples, the results of calculation show that the present method can effectively overcome the non-uniqueness problem. 相似文献
996.
Jing Tang XING 《力学进展》1971,46(1):201602
本文综述了线性与非线性流固耦合问题数值方法的进展及工程应用. 讨论了四种数值分析方法: (1) 混合有限元-子结构-子区域数值模型, 以求解有限域线性流固耦合问题, 如流体晃动, 声腔-结构耦合, 流体中的压力波, 化工容器的地震响应,坝水耦合等; (2) 混合有限元-边界元数值模型, 以求解涉及无限域的线性流固耦合问题, 如大型浮体承受飞机降落冲击, 船舰的炮击回应等; (3) 混合有限元-有限差分(体积) 数值模型, 以求解不涉及破浪和两相分离的非线性流固耦合问题; (4) 混合有限元-光滑粒子数值模型, 以求解涉及破浪和两相分离的非线性流固耦合问题. 文中推荐分区迭代求解过程, 以便应用现有的固体及流体求解器, 于毎一时间步长分别求解固体及流体的方程, 通过耦合迭代收敛, 向前推进以达问题求解. 文中选用的工程应用例子包含气-液-壳三相耦合, 液化天然气船水晃动, 人体步行冲击引起的声腔-建筑结构耦合, 大型浮体承受飞机降落冲击的瞬态动力回应, 涉及破浪和两相分离的气-翼耦合及结构于水上降落的冲击. 数值分析结果与可用的实验或计算结果作了比较, 以说明所述方法的精度及工程应用价值. 文中列出了基于流固耦合的波能采积装置模型, 以应用线性系统的共振及非线性系统的周期解原理, 有效地采积波能. 本文列出了231 篇参考文献, 以便读者进一步研讨所感兴趣方法. 相似文献
997.
Forced Convective Cooling via Acoustic Streaming in a Narrow Channel Established by a Vibrating Piezoelectric Bimorph 总被引:2,自引:0,他引:2
Qun?Wan Tao?Wu John?Chastain William?L.?Roberts Andrey?V.?KuznetsovEmail author Paul?I.?Ro 《Flow, Turbulence and Combustion》2005,74(2):195-206
Forced convection in a narrow channel is investigated both numerically and experimentally. The flow field is established through the mechanism of acoustic streaming. This is accomplished by high frequency vibration of one of the channel walls, which is composed of a piezoelectric bimorph. In the numerical computations, the Navier-Stokes equations are decomposed into the acoustic equations and the streaming equations by the perturbation method. The acoustic field is first numerically obtained, which provides the driving force for the streaming field. The streaming field and the associated temperature field are then obtained numerically. Heat losses from a heat source are measured to determine the efficiency of this as a cooling method. The air-flow patterns in the channel between the heat source and the bimorph actuator are visualized using the particle tracking velocimetry. The visualization clearly shows that vortical streaming (acoustic streaming) can be induced by bimorph vibration, which enhances heat transfer between the heat source and the surrounding air. The temperature decreases obtained computationally and experimentally are in good agreement. 相似文献
998.
Maria Bała 《Transport in Porous Media》1992,9(1-2):123-134
A full waveform recording in a borehole during acoustic logging makes it possible to determine the elastic parameters of a medium under in-situ conditions.The velocity of elastic wave propagation in rocks and elastic moduli are influenced by factors connected with its macrostructure and microstructure, as well as with rock overburden and porous pressure and temperature.The results of the calculations of the relationships between the elastic and reservoir parameters of sedimentary rocks are presented in this paper. The theoretical Kuster and Toksöz model has been applied.The influence of the porosity, the pore space coefficient, and the saturation of different media of porous rocks on elastic moduli and on compressional and shear wave propagation have been considered in this model. The complex composition of the skeleton and the influence of clay material in the porous rock are taken into account. 相似文献
999.
Some examples of flows with separation zones andmovable contact discontinuities obtained as a result of the numerical integration of the time-dependent equations for an ideal gas are presented. The examples concern a steady annular separation zone on the blunt nose of a body in a supersonic flow, periodic shedding of unsteady discontinuities from a cylinder in a steady uniform subsonic flow with a supercritical Mach number, and the complicated deformation of a contact (tangential) discontinuity, namely, the boundaries of a two-dimensional jet, either subsonic or supersonic, flowing into a cocurrent subsonic low-velocity flow. A multiple increase in the difference grid capacity in the numerical integration of the Euler equations indicates the absence of a noticeable scheme viscosity effect in the examples calculated. The inviscid nature of the separation flows obtained is also confirmed by their well-known counterparts constructed in the ideal incompressible fluid approximation. The time-average velocity fields of the two-dimensional jet and the intensity of its sound field are in reasonable agreement with the available data. 相似文献
1000.
姚志远 《应用数学和力学(英文版)》2002,23(3):350-354
IntroductionVibratingobjectsunderwater,suchassubmarineandtorpedo ,transmitnoisetowardsexternalsoundfield ,formachineryvibrationofinsidepowerapparatus.Itwillenhancegreatlytheconcealmentofsubmarineandtorpedoandenforcefightingpowerbycontrollingnoiseofsubma… 相似文献