全文获取类型
收费全文 | 812篇 |
免费 | 73篇 |
国内免费 | 74篇 |
专业分类
化学 | 41篇 |
晶体学 | 1篇 |
力学 | 214篇 |
综合类 | 25篇 |
数学 | 445篇 |
物理学 | 233篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 4篇 |
2021年 | 22篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 27篇 |
2017年 | 32篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 33篇 |
2013年 | 40篇 |
2012年 | 32篇 |
2011年 | 54篇 |
2010年 | 29篇 |
2009年 | 52篇 |
2008年 | 61篇 |
2007年 | 56篇 |
2006年 | 55篇 |
2005年 | 54篇 |
2004年 | 46篇 |
2003年 | 46篇 |
2002年 | 37篇 |
2001年 | 26篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有959条查询结果,搜索用时 31 毫秒
11.
12.
Frame Wavelets with Compact Supports for L^2(R^n) 总被引:1,自引:0,他引:1
De Yun YANG King Wei ZHOU Zhu Zhi YUAN 《数学学报(英文版)》2007,23(2):349-356
The construction of frame wavelets with compact supports is a meaningful problem in wavelet analysis. In particular, it is a hard work to construct the frame wavelets with explicit analytic forms. For a given n × n real expansive matrix A, the frame-sets with respect to A are a family of sets in R^n. Based on the frame-sets, a class of high-dimensional frame wavelets with analytic forms are constructed, which can be non-bandlimited, or even compactly supported. As an application, the construction is illustrated by several examples, in which some new frame wavelets with compact supports are constructed. Moreover, since the main result of this paper is about general dilation matrices, in the examples we present a family of frame wavelets associated with some non-integer dilation matrices that is meaningful in computational geometry. 相似文献
13.
This paper reports on the experimental investigation of the dynamic large deflection response of a portal frame impacted at its midspan by a body moving at a certain speed. Both the deflection and velocity vs. time curves of the midspan and the dynamic history of a number of desired locations were recorded during the process of response. On the basis of the test data, the momentum and kinetic energy conversion between the frame and the moving body in the impact process are realized, and the occurrence and expansion of plastic regions are described. Investigation results show that the initial collision is approximately ideally inelastic, and that the elastic deformation plays a considerable role in the response though the input energy is much larger than the maximum elastic energy capacity of the beam member; therefore, in a general impact, the energy ratio should not be regarded as a sufficient criterion for a rigid—plastic solution. The ratios of the impulse transferred to and the energy absorbed by the frame in the initial collision to that carried by the moving body before impact is only related to the ratiobetween the equivalent mass of the frame paticipating in the initial collision and the mass of the impacting body, having nothing to do with the impacting velocity to a certain extent. 相似文献
14.
15.
16.
About Perrhenates. 3 On the Structure of the Mesoperrhenate Na3[ReO5] By tempering powder samples (prepared from mixtures of binary oxides: Na2O2/ReO2 and Na2O/ReO3 respectively, Na : Re = 3 : 1, Ar and O2 atmosphere respectively, 400–450°C, corundum boat) in a closed Ag cylinder (500–550°C, 10 d) yellow single crystals of Na3ReO5, sensitive to moisture, were grown. The compound crystallizes trigonal, space group P31, P32 respectively, with a = 5.544(1), c = 13.580(7) Å, Z = 3, drö. = 4.62 g/cm3. The crystal structure [4-circle diffractometer data, 1091 I0(hkl), AgKα, R = 6.14, Rw = 6.08%] is characterized by “isolated” bipyramids ReO5. Na+ ions are occupying all the tetrahedral (Na2, Na3) and octahedral (Na1) holes of the pseudocubic face centred (c/a = 2.441) Re part of the lattice; resulting in a Na3Re kation framework corresponding to the Li3Bi type of structure. Effective Coordination Numbers (ECoN), the Madelung Part of Lattice energy (MAPLE) and the charge distribution (CHARDI) are computed and discussed. 相似文献
17.
Richard J. Wiener Philip W. Hammer Charles E. Swanson David C. Samuels Russell J. Donnelly 《Journal of statistical physics》1991,64(5-6):913-926
Taylor-Couette flow subject to a Coriolis force is studied experimentally and numerically. In the experiment, the Couette apparatus is mounted on a turntable with the axis of the cylinders orthogonal to the rotation vector of the turntable. The Coriolis force stabilizes the fluid against the onset of Taylor vortices and alters the velocity fields, both above and below the transition from the initial flow. At small dimensionless turntable frequencies, the transition yields time-independent Taylor vortices which are tilted with respect to the cylinder axis. At larger there is a direct transition to turbulence. We determine the first-order correction to the classical Couette initial flow, to account for the effects of the Coriolis force, by expanding in powers of. We present numerical results for the axial velocity (the only nonvanishing correction term to order) in the infinite-cylinder approximation. 相似文献
18.
19.
Necessary conditions for the existence of a super‐simple, decomposable, near‐resolvable ‐balanced incomplete block design (BIBD) whose 2‐component subdesigns are both near‐resolvable ‐BIBDs are (mod ) and . In this paper, we show that these necessary conditions are sufficient. Using these designs, we also establish that the necessary conditions for the existence of a super‐simple near‐resolvable ‐RBIBD, namely (mod ) and , are sufficient. A few new pairwise balanced designs are also given. 相似文献
20.
In this paper, we present a method for constructing multivariate tight framelet packets associated with an arbitrary dilation matrix using unitary extension principles.We also prove how to construct various tight frames for L2(Rd) by replac-ing some mother framelets. 相似文献