全文获取类型
收费全文 | 8348篇 |
免费 | 1321篇 |
国内免费 | 1271篇 |
专业分类
化学 | 6179篇 |
晶体学 | 99篇 |
力学 | 665篇 |
综合类 | 94篇 |
数学 | 1134篇 |
物理学 | 2769篇 |
出版年
2024年 | 18篇 |
2023年 | 163篇 |
2022年 | 170篇 |
2021年 | 247篇 |
2020年 | 315篇 |
2019年 | 300篇 |
2018年 | 231篇 |
2017年 | 244篇 |
2016年 | 419篇 |
2015年 | 337篇 |
2014年 | 425篇 |
2013年 | 579篇 |
2012年 | 714篇 |
2011年 | 686篇 |
2010年 | 562篇 |
2009年 | 478篇 |
2008年 | 536篇 |
2007年 | 452篇 |
2006年 | 439篇 |
2005年 | 421篇 |
2004年 | 362篇 |
2003年 | 335篇 |
2002年 | 390篇 |
2001年 | 352篇 |
2000年 | 244篇 |
1999年 | 249篇 |
1998年 | 186篇 |
1997年 | 172篇 |
1996年 | 185篇 |
1995年 | 141篇 |
1994年 | 130篇 |
1993年 | 97篇 |
1992年 | 70篇 |
1991年 | 70篇 |
1990年 | 43篇 |
1989年 | 26篇 |
1988年 | 35篇 |
1987年 | 18篇 |
1986年 | 28篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1957年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
空间理性八节点块体元 总被引:1,自引:0,他引:1
推导出空间八节点块体理性有限元列式,采用具有直到三次多项式的空间问题的微分方程的解作为插值的近似函数,数例结果表明空间理性八节点块体元的有效性。 相似文献
992.
本文用拉格朗日方法对稀薄气固两相流进行了数值分析,着重讨论有颗粒存在时,颗粒对气流速度分布的影响。计算的实例与实验结果比较,有着很好的吻合。 相似文献
993.
压电材料椭圆夹杂界面开裂问题的电弹性耦合解 总被引:1,自引:0,他引:1
本文研究了在反平面剪切和面内电场的共同作用下,压电材料椭圆夹杂的界面开裂问题,假定夹杂是刚性的导体,采用复变函数保角变换和级数展开方法,可确定压电材料基体的复势表达式,进而求得夹杂界面开裂的电弹性耦合的能量释放率。 相似文献
994.
Wall boundary conditions for high-order finite-difference schemes in computational aeroacoustics 总被引:2,自引:0,他引:2
High-order finite-difference schemes are less dispersive and dissipative but, at the same time, more isotropic than low-order schemes. They are well suited for solving computational acoustics problems. High-order finite-difference equations, however, support extraneous wave solutions which bear no resemblance to the exact solution of the original partial differential equations. These extraneous wave solutions, which invariably degrade the quality of the numerical solutions, are usually generated when solid-wall boundary conditions are imposed. A set of numerical boundary conditions simulating the presence of a solid wall for high-order finite-difference schemes using a minimum number of ghost values is proposed. The effectiveness of the numerical boundary conditions in producing quality solutions is analyzed and demonstrated by comparing the results of direct numerical simulations and exact solutions.This work was supported by the NASA Lewis Research Center Grant NAG 3-1267 and in part by the NASA Langley Research Center Grant NAG 1-1479 and the Florida State University through time granted on its Cray-YMP Supercomputer. 相似文献
995.
This study is devoted to the development of a unified and explicit elastic solution to the problem of a spherical inhomogeneity with an imperfectly bonded interface. Both tangential and normal displacement discontinuities at the interface are considered and a linear interfacial condition, which assumes that the tangential and the normal displacement jumps are proportional to the associated tractions, is adopted. The elastic disturbance due to the presence of an imperfectly bonded inhomogeneity is decomposed into two parts: the first is formulated in terms of an equivalent nonuniform eigenstrain distributed over a perfectly bonded spherical inclusion, while the second is formulated in terms of an imaginary Somigliana dislocation field which models the interfacial sliding and normal separation. The exact form of the equivalent nonuniform eigenstrain and the imaginary Somigliana dislocation are fully determined in this paper. 相似文献
996.
997.
Fracture of a rectangular piezoelectromagnetic body 总被引:5,自引:0,他引:5
The singular stress, electric fields and magnetic fields in a rectangular piezoelectromagnetic body containing a center Griffith crack under longitudinal shear are obtained. Fourier transforms and Fourier sine series are used to reduce the mixed boundary value problems of the crack, which is assumed to be impermeable, to dual integral equations. The solution of the dual integral equations is then expressed in terms of Fredholm integral equations of the second kind. Expressions for stresses, electric displacements and magnetic inductions in the vicinity of the crack tip are derived. Also obtained are the field intensity factors and the energy release rates. Numerical results obtained show that the geometry of the rectangular body have significant influence on the field intensity factors and the energy release rates. 相似文献
998.
Two theorems concerning the existence of positive solutions for the singular equation
are presented. The results are obtained by using the nonlinear Leray-Schauder alternative and the lower-upper solution method. 相似文献
999.
1000.
when the beam theory was used to calculate ship hull vibration,greater discrepancies were found between theoretical cal-culations and actual measurements especially at higher modes.Thusthe beam model cannot be considered as a practical one for higher-mode calculations.This paper presents the application of two-dimensional finite element model for the calculation of ship ver-tical vibration.Using the multi-element structural dynamic a-nalysis program DDJ(DL)developed by ourselves,the hull vibra-tion analysis of two ships(vessel A and vessel B)was carriedout on the Model-709 Computer made in the People’s Republic ofChina.The results of the calculation,when compared with actualmeasurements.show that the two-dimensional model is much moreefficient than the traditional beam model.The agreement be-tween the calculations and measurements has been improved greatly,and this discrepancy at the4th·and5th-modes has decreased towithin5%as compared to that of more than20%in the traditionalmodel.Furthermore.the mode 相似文献