全文获取类型
收费全文 | 4474篇 |
免费 | 151篇 |
国内免费 | 28篇 |
专业分类
化学 | 2917篇 |
晶体学 | 15篇 |
力学 | 214篇 |
数学 | 776篇 |
物理学 | 731篇 |
出版年
2023年 | 20篇 |
2022年 | 31篇 |
2021年 | 65篇 |
2020年 | 61篇 |
2019年 | 71篇 |
2018年 | 56篇 |
2017年 | 59篇 |
2016年 | 128篇 |
2015年 | 116篇 |
2014年 | 146篇 |
2013年 | 255篇 |
2012年 | 325篇 |
2011年 | 388篇 |
2010年 | 202篇 |
2009年 | 211篇 |
2008年 | 271篇 |
2007年 | 280篇 |
2006年 | 297篇 |
2005年 | 284篇 |
2004年 | 224篇 |
2003年 | 219篇 |
2002年 | 197篇 |
2001年 | 51篇 |
2000年 | 52篇 |
1999年 | 36篇 |
1998年 | 40篇 |
1997年 | 53篇 |
1996年 | 48篇 |
1995年 | 41篇 |
1994年 | 51篇 |
1993年 | 32篇 |
1992年 | 26篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 16篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 18篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 9篇 |
排序方式: 共有4653条查询结果,搜索用时 15 毫秒
41.
In this last in a series of three papers, we summarize an asymptotic analysis of the near-tip stress and deformation fields for an interface crack between two sheets of Generalized Neo-Hookean materials. This investigation, which is consistent with the nonlinear elastostatic theory of plane stress, allows for an arbitrary choice, on both sides of the three parameters characterizing this class of hyperelastic materials. The first three terms of the approximation series are obtained, showing the existence of a non-oscillatory and contact-free solution to the interface crack problem. The analytical results are compared with a full-field solution obtained numerically using the finite element method. 相似文献
42.
Intersonic crack propagation in homogeneous media under shear-dominated loading: theoretical analysis 总被引:1,自引:0,他引:1
Dhirendra V. Kubair Philippe H. Geubelle Yonggang Y. Huang 《Journal of the mechanics and physics of solids》2002,50(8):1547-1564
The mechanics of cohesive failure under mixed-mode loading is investigated for the case of a steadily propagating subsonic and intersonic dynamic crack subjected to a follower tensile and shear distributed load. The cohesive failure model chosen in this study is rate independent but accounts for the coupling between normal and tangential damage. Special emphasis is placed here on mixed-mode cases with predominantly shear loading. The analysis shows that the size of the mixed-mode cohesive zone is smaller than that obtained in the pure shear case. The relative extent of the shear and tensile cohesive damage zones depends on the crack speed and the mode mixity. In the intersonic regime, the failure process takes place exclusively in shear, even under remote mixed-mode loading conditions. 相似文献
43.
This Note presents an experimental vibro-acoustic set-up that aims to reproduce the energy pumping phenomenon between an acoustic medium and an essentially nonlinear oscillator. It shows a one-way irreversible transfer of energy between the first acoustic mode in a tube and a thin visco-elastic membrane. To cite this article: B. Cochelin et al., C. R. Mecanique 334 (2006). 相似文献
44.
Oscillatory rheological experiments at different temperatures and over a wide range of frequencies have been used to investigate
the gelation process and, more particularly, the sol–gel transition of various poly(vinyl chloride) (PVC) plastisols. The
sol–gel transition process was found to be universal with respect to the temperature and solid volume fraction according to
the similarity of the fractal structure in PVC plastisols. The variation of the gel time (t
gel) with temperature for any composition of PVC plastisols was predicted from the Dickinson’s model (E. Dickinson, J Chem Soc
Faraday Trans, 93:111–114, 1997). Dynamic viscoelastic properties of PVC plastisols have also been studied as a function of
temperature that allowed us to follow the gelation process of various plastisols. Thus, the influence of the type and concentration
of PVC resins in gelation process was investigated. The variation of the complex shear modulus at a constant frequency was
depicted by a master curve regarding the dependence of the moduli on PVC concentrations. 相似文献
45.
46.
We consider as in Parts I and II a family of linearly elastic shells of thickness 2?, all having the same middle surfaceS=?(?)?R 3, whereω?R 2 is a bounded and connected open set with a Lipschitz-continuous boundary, and? ∈ ?3 (?;R 3). The shells are clamped on a portion of their lateral face, whose middle line is?(γ 0), whereγ 0 is a portion of?ω withlength γ 0>0. For all?>0, let $\zeta _i^\varepsilon$ denote the covariant components of the displacement $u_i^\varepsilon g^{i,\varepsilon }$ of the points of the shell, obtained by solving the three-dimensional problem; let $\zeta _i^\varepsilon$ denote the covariant components of the displacement $\zeta _i^\varepsilon$ a i of the points of the middle surfaceS, obtained by solving the two-dimensional model ofW.T. Koiter, which consists in finding $$\zeta ^\varepsilon = \left( {\zeta _i^\varepsilon } \right) \in V_K (\omega ) = \left\{ {\eta = (\eta _\iota ) \in {\rm H}^1 (\omega ) \times H^1 (\omega ) \times H^2 (\omega ); \eta _i = \partial _v \eta _3 = 0 on \gamma _0 } \right\}$$ such that $$\begin{gathered} \varepsilon \mathop \smallint \limits_\omega a^{\alpha \beta \sigma \tau } \gamma _{\sigma \tau } (\zeta ^\varepsilon )\gamma _{\alpha \beta } (\eta )\sqrt a dy + \frac{{\varepsilon ^3 }}{3} \mathop \smallint \limits_\omega a^{\alpha \beta \sigma \tau } \rho _{\sigma \tau } (\zeta ^\varepsilon )\rho _{\alpha \beta } (\eta )\sqrt a dy \hfill \\ = \mathop \smallint \limits_\omega p^{i,\varepsilon } \eta _i \sqrt a dy for all \eta = (\eta _i ) \in V_K (\omega ), \hfill \\ \end{gathered}$$ where $a^{\alpha \beta \sigma \tau }$ are the components of the two-dimensional elasticity tensor ofS, $\gamma _{\alpha \beta }$ (η) and $\rho _{\alpha \beta }$ (η) are the components of the linearized change of metric and change of curvature tensors ofS, and $p^{i,\varepsilon }$ are the components of the resultant of the applied forces. Under the same assumptions as in Part I, we show that the fields $\frac{1}{{2_\varepsilon }}\smallint _{ - \varepsilon }^\varepsilon u_i^\varepsilon g^{i,\varepsilon } dx_3^\varepsilon$ and $\zeta _i^\varepsilon$ a i , both defined on the surfaceS, have the same principal part as? → 0, inH 1 (ω) for the tangential components, and inL 2(ω) for the normal component; under the same assumptions as in Part II, we show that the same fields again have the same principal part as? → 0, inH 1 (ω) for all their components. For “membrane” and “flexural” shells, the two-dimensional model ofW.T. Koiter is therefore justified. 相似文献
47.
Alexandre Ragouilliaux Benjamin Herzhaft François Bertrand Philippe Coussot 《Rheologica Acta》2006,46(2):261-271
To have a better knowledge of problems occurring with drilling fluids in complex wells, we carried out a detailed rheological analysis of a typical drilling mud at low shear rates using both conventional rheometry and MRI velocimetry. We show the existence of a viscosity bifurcation effect: Below a critical stress value, the mud tends to completely stop flowing, whereas beyond this critical stress, it reaches an apparent shear rate larger than a finite (critical) value, and no stable flows can be obtained between this critical shear rate value and zero. These results are confirmed by MRI velocity profiles, which exhibit a slope break at the interface between the solid and the liquid phases inside the Couette geometry. Moreover, this viscosity bifurcation is a transient phenomenon, the progressive development of which can be observed by MRI. A further examination of MRI data shows that, in the transient regime, the shear rate does not vary monotonously in the rheometer gap and is particularly large along the outer (rough) cylinder, which might be at the origin of the development of a region of constant shear rate in the apparent flow curve. 相似文献
48.
The two-dimensional equations of a nonlinearly elastic ‘flexural’ shell have been recently identified and justified by V.
Lods and B. Miara, by means of the method of formal asymptotic expansions applied to the three-dimensional equations of nonlinear
elasticity. These equations can be recast as a minimization problem for a ‘two-dimensional energy’ over a manifold of ‘admissible
deformations’. The stored energy function is a quadratic expression in terms of the exact difference between the curvature
tensor of the deformed middle surface and that of the undeformed one; the admissible deformations are those that preserve
the metric of the undeformed middle surface and satisfy boundary conditions of clamping or of simple support. We establish
here that this minimization problem has at least one solution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
Dr. Tran Quang Hung Dr. Ferial Terki Dr. Souleymane Kamara Mourad Dehbaoui Prof. Salam Charar Brajalal Sinha Prof. CheolGi Kim Dr. Philippe Gandit Il'ya A. Gural'skiy Dr. Gabor Molnar Dr. Lionel Salmon Dr. Helena J. Shepherd Dr. Azzedine Bousseksou 《Angewandte Chemie (International ed. in English)》2013,52(4):1058-1058
50.
Dr. Debangshu Chaudhuri Dr. Eva Sigmund Annemarie Meyer Lisa Röck Philippe Klemm Sebastian Lautenschlager Agnes Schmid Shane R. Yost Prof. Dr. Troy Van Voorhis Dr. Sebastian Bange Prof. Dr. Sigurd Höger Prof. Dr. John M. Lupton 《Angewandte Chemie (International ed. in English)》2013,52(50):13449-13452