全文获取类型
收费全文 | 5027篇 |
免费 | 680篇 |
国内免费 | 395篇 |
专业分类
化学 | 845篇 |
晶体学 | 64篇 |
力学 | 2091篇 |
综合类 | 93篇 |
数学 | 1457篇 |
物理学 | 1552篇 |
出版年
2024年 | 13篇 |
2023年 | 31篇 |
2022年 | 87篇 |
2021年 | 109篇 |
2020年 | 151篇 |
2019年 | 133篇 |
2018年 | 135篇 |
2017年 | 189篇 |
2016年 | 215篇 |
2015年 | 172篇 |
2014年 | 224篇 |
2013年 | 378篇 |
2012年 | 220篇 |
2011年 | 274篇 |
2010年 | 190篇 |
2009年 | 234篇 |
2008年 | 284篇 |
2007年 | 319篇 |
2006年 | 286篇 |
2005年 | 259篇 |
2004年 | 225篇 |
2003年 | 239篇 |
2002年 | 207篇 |
2001年 | 192篇 |
2000年 | 197篇 |
1999年 | 192篇 |
1998年 | 141篇 |
1997年 | 96篇 |
1996年 | 110篇 |
1995年 | 88篇 |
1994年 | 98篇 |
1993年 | 70篇 |
1992年 | 49篇 |
1991年 | 61篇 |
1990年 | 44篇 |
1989年 | 35篇 |
1988年 | 32篇 |
1987年 | 23篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有6102条查询结果,搜索用时 15 毫秒
41.
We establish solvability of the boundary-value problems describing stationary and periodic flows of viscoplastic media. In the case of stationary flows we study the question of convergence of the Galerkin method. For the problem of periodic flows we prove a version of the second Bogolyubov theorem. 相似文献
42.
本文研究了非线性应变波方程与Schr(?)dinger方程耦合系统Cauchy问题吸引 子的正则性.获得了该系统在空间Eo中存在整体吸引子Ao,并且Ao与E1中的强吸 引子A1相等. 相似文献
43.
Alexander Linkov Liliana Rybarska-Rusinek 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(10):821-831
The paper presents a general method to find asymptotics for a (multi-)wedge system containing a thin wedge. It employs separation
of the symmetric and anti-symmetric parts of the boundary displacements and tractions of the wedge. The method is applicable
when the angle of the thin wedge turns to zero. A physical interpretation of the derived equations is obtained by using power
expansions of non-polynomial functions, which appear after the Mellin transform. We establish that the first term in the expansion
of the symmetric part corresponds to shear, while the first term of the anti-symmetric part describes deflection of the wedge
axis. Numerical experiments, performed by using a code developed on the basis of the theory, show that using only the first
terms of the expansions insignificantly influence accuracy: the approximate results coincide with the exact values of roots
to the third significant digit even for the wedge angle of 30°. 相似文献
44.
Periodica Mathematica Hungarica - Let X 1,X 2,... be a sequence of independent and identically distributed random variables, and put % MATHTYPE!MTEF!2!1!+-%... 相似文献
45.
Tandem intramolecular silylformylation-allyl(crotyl)silylation reactions have been developed that allow the highly efficient synthesis of polyketide fragments. The substrates are subjected to Rh(I)-catalyzed silylformylation to afford β-(diallyl)silyl aldehydes which undergo spontaneous uncatalyzed allylsilylation. This unusual spontaneous allylsilylation reaction is driven by strain release Lewis acidity, which arises from the ∼95° O-Si-C bond angle in the oxasilacyclopentane product of the silylformylation reaction. The methodology has been developed both for alkene and alkyne substrates, may be used to establish as many as three stereocenters, and has been shown to be amenable to use in an iterative fashion. 相似文献
46.
I. J. Gnip V. I. Kersulis S. I. Vaitkus S. A. Veyelis 《Mechanics of Composite Materials》2005,41(6):535-540
Data obtained in investigating the creep of expanded polystyrene in compression are discussed. An analysis of the results
of creep tests 65–608 days long showed that the creep can be predicted for 50 years based on experiments of less duration
than the 605 days indicated in EN 13163. For this purpose, it is suggested to employ a 95-fold extrapolation in time if the
creep curves are described by a power function (as recommended by EN 13163) or a 50-fold extrapolation if the exponential
equation proposed in the present paper is used.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 795–802, November–December, 2005. 相似文献
47.
Frank N. Proske Madan L. Puri 《Proceedings of the American Mathematical Society》2003,131(9):2937-2944
In this article we prove a strong law of large numbers for Borel measurable nonseparably valued random elements in the case of generalized random sets.
48.
大视场短焦距镜头CCD摄像系统的畸变校正 总被引:11,自引:1,他引:10
从光学测量角度出发,结合计算机视觉中的摄像机标定方法,解决了大视场短焦距镜头CCD摄像系统的畸变校正问题。与摄像机标定不同,畸变校正中仅标定内部参数,外部参数作为已知条件。采用线性畸变模型,由最小二乘法解线性方程组得到摄像系统畸变模型的畸变系数。介绍了数字图像中像素间距和光学中心的标定方法。通过比较由标定参数得到的畸变图像和摄像机采集的畸变图像对实验标定精度进行评定,实验结果表明边缘视场(112°)的标定精度达到了0 75%。 相似文献
49.
Jin Sun Yihu Song Qiang Zheng Hong Tan Jie Yu Hong Li 《Journal of Polymer Science.Polymer Physics》2007,45(18):2594-2602
The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO2 causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO2 hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007 相似文献
50.