全文获取类型
收费全文 | 8043篇 |
免费 | 1254篇 |
国内免费 | 935篇 |
专业分类
化学 | 5792篇 |
晶体学 | 86篇 |
力学 | 457篇 |
综合类 | 52篇 |
数学 | 925篇 |
物理学 | 2920篇 |
出版年
2024年 | 27篇 |
2023年 | 151篇 |
2022年 | 323篇 |
2021年 | 294篇 |
2020年 | 317篇 |
2019年 | 356篇 |
2018年 | 283篇 |
2017年 | 262篇 |
2016年 | 380篇 |
2015年 | 426篇 |
2014年 | 441篇 |
2013年 | 542篇 |
2012年 | 712篇 |
2011年 | 781篇 |
2010年 | 485篇 |
2009年 | 418篇 |
2008年 | 482篇 |
2007年 | 415篇 |
2006年 | 421篇 |
2005年 | 354篇 |
2004年 | 261篇 |
2003年 | 227篇 |
2002年 | 169篇 |
2001年 | 174篇 |
2000年 | 169篇 |
1999年 | 202篇 |
1998年 | 164篇 |
1997年 | 138篇 |
1996年 | 137篇 |
1995年 | 124篇 |
1994年 | 116篇 |
1993年 | 76篇 |
1992年 | 79篇 |
1991年 | 88篇 |
1990年 | 59篇 |
1989年 | 34篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing 下载免费PDF全文
2.
We consider concentrated vorticities for the Euler equation on a smooth domain in the form of supported on well-separated vortical domains , , of small diameters . A conformal mapping framework is set up to study this free boundary problem with being part of unknowns. For any given vorticities and small , through a perturbation approach, we obtain such piecewise constant steady vortex patches as well as piecewise smooth Lipschitz steady vorticities, both concentrated near non-degenerate critical configurations of the Kirchhoff–Routh Hamiltonian function. When vortex patch evolution is considered as the boundary dynamics of , through an invariant subspace decomposition, it is also proved that the spectral/linear stability of such steady vortex patches is largely determined by that of the 2N-dimensional linearized point vortex dynamics, while the motion is highly oscillatory in the 2N-codim directions corresponding to the vortical domain shapes. 相似文献
3.
4.
A multi-exposure of color fringes method has been developed to improve the capture speed of a conventional color CCD camera. In the method, four groups of projected fringe patterns encoded with different colors and different directions are stored in one CCD frame. Therefore the capture frequency of the conventional CCD can be improved to 200 Hz. It is available to measure the insect wings with low beating frequency, such as dragonfly, moth, or butterfly, whose beating frequency is about 30–40 Hz. We have used the method to measure the beating motion of a moth successfully. 相似文献
5.
Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi4−xNdxTi4O15 (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd3+ dopant. The effects of Nd3+ doping on the dielectric and ferroelectric properties of CaBi4Ti4O15 ceramics are studied. Nd3+ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd3+ doped CaBi4Ti4O15 ceramics was increased by 80% at x=0.25, while more Nd3+ dopant decreased the remnant polarization. CaBi3.75Nd0.25Ti4O15 ceramics had the largest piezoelectric constant d33. The structure and properties of CaBi4−xNdxTi4O15 ceramics showed that Nd3+ may occupy different crystal locations when Nd3+ content x is less than 0.25 and more than 0.50. 相似文献
6.
曾六川 《高等学校计算数学学报(英文版)》2003,12(1)
The purpose of this paper is to investigate the problem of approximating fixed points of non-Lipschitizian asymptotically pseudocontractive mappings in an arbitrary real Banach space by the modified Ishikawa iterative sequences with errors. 相似文献
7.
8.
9.
A Note on Topological Entropy of Maps 总被引:1,自引:0,他引:1
For a given collection of subsets of a compact metric space X which cover X,the entropies,hm(f)and hi(f),are introduced for a continuous map f of X to itseif. Also the concept of shadowing property with same end point (SPSEP for short) is introduced. The main results are,(1)H(f)≤hi(f)+hm(f)and,(2)h(f)=hm(f)whenever f has SPSEP,where h(f) is the topological entropy of f. Moreover,several corollaries are obtained. 相似文献
10.
利用指数二分性和泛函分析方法,我们研究了当未扰动系统不具有异宿流形的退化异宿分支.我们利用Melnikov型向量给出了系统在退化情形下的横截异宿轨道存在的充分条件. 相似文献