全文获取类型
收费全文 | 69628篇 |
免费 | 1675篇 |
国内免费 | 2427篇 |
专业分类
化学 | 47472篇 |
晶体学 | 40篇 |
力学 | 1423篇 |
综合类 | 46篇 |
数学 | 2486篇 |
物理学 | 22263篇 |
出版年
2023年 | 171篇 |
2022年 | 184篇 |
2021年 | 152篇 |
2020年 | 147篇 |
2019年 | 120篇 |
2018年 | 188篇 |
2017年 | 88篇 |
2016年 | 200篇 |
2015年 | 227篇 |
2014年 | 431篇 |
2013年 | 336篇 |
2012年 | 6065篇 |
2011年 | 8666篇 |
2010年 | 1566篇 |
2009年 | 530篇 |
2008年 | 6221篇 |
2007年 | 6537篇 |
2006年 | 6588篇 |
2005年 | 6264篇 |
2004年 | 4891篇 |
2003年 | 3607篇 |
2002年 | 3293篇 |
2001年 | 2211篇 |
2000年 | 2509篇 |
1999年 | 980篇 |
1998年 | 359篇 |
1997年 | 266篇 |
1996年 | 1137篇 |
1995年 | 901篇 |
1994年 | 982篇 |
1993年 | 1296篇 |
1992年 | 1097篇 |
1991年 | 539篇 |
1990年 | 583篇 |
1989年 | 498篇 |
1988年 | 461篇 |
1987年 | 449篇 |
1986年 | 455篇 |
1985年 | 449篇 |
1984年 | 192篇 |
1983年 | 129篇 |
1982年 | 122篇 |
1981年 | 108篇 |
1975年 | 126篇 |
1959年 | 83篇 |
1958年 | 134篇 |
1957年 | 123篇 |
1956年 | 109篇 |
1955年 | 118篇 |
1954年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
SINGLE MACHINE SCHEDULING WITH CONTROLLABLE PROCESSING TIMES AND COMPRESSION COSTS (PART I:EQUAL TIMES AND COSTS) 总被引:1,自引:0,他引:1
Most papers in scheduling research have treated individual job processing times as fixed parameters. However, in many practical situations, a manager may control processing time by realloeating resources. In this paper, authors consider a machine scheduling problemwith controllable processing times. In the first part of this paper, a special case where the pro-cessing times and compression costs are uniform among jobs is discussed. Theoretical results are derived that aid in developing an O(n^2) algorithm to slove the problem optimally. In the second part of this paper, authors generalize the discussion to general case, An effective heuristic to the genera/ problem will be presented. 相似文献
152.
Xiugui LIU Xiangjun WANG Department of Mathematics LPMC Nankai University Tianjin China. 《数学年刊B辑(英文版)》2006,(3)
This paper computes the Thorn map onγ2 and proves that it is represented by 2b2,0h1,2 in the ASS. The authors also compute the higher May differential of 62,0, from which it is proved thatγs(b0hn-h1bn-1) for 2≤s < p - 1 are permanent cycles in the ASS. 相似文献
153.
Positron-Lithium Atom and Electron-Lithium Atom Scattering Systems at Intermediate and High Energies
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K. Ratnavelu S. Y. Ng 《中国物理快报》2006,23(7):1753-1756
The coupled-channel optical method is used to study positron scattering by atomic lithium at energies ranging from the ionization threshold to 60eV, The present method simultaneously treats the target channels and the positronium (Ps) channels in the coupled-channel method together with the continuum effects via an ab-initio optical potential. Ionization, elastic and inelastic cross sections in target channels, and the total cross section are also reported and compared with other theoretical and experimental data. A comparative study with the corresponding electron-lithium data is also reported. 相似文献
154.
The authors consider the exact controllability of the vibrations of a thin shallow shell, of thickness 2εwith controls imposed on the lateral surface and at the top and bottom of the shell. Apart from proving the existence of exact controls, it is shown that the solutions of the three dimensional exact controllability problems converge, as the thickness of the shell goes to zero, to the solution of an exact controllability problem in two dimensions. 相似文献
155.
The authors derive a formula for the volume of a compact domain in a symmetric space from normal sections through a special submanifold in the symmetric space.This formula generalizes the volume of classical domains as tubes or domains given as motions along the submanifold.Finally,some stereological considerations regarding this formula are provided. 相似文献
156.
Based on the anisotropic Seebeck tensor coefficients, a light-thermo-radiation detector made of high-Tc superconductor (YBa2Cu3O7-δ) was fabricated, which can function at room temperature. The induced voltaic signals at various modulation frequencies for radiation from He-Ne laser and from a 500 K black body were measured. The noise ratio for detecting He-Ne laser radiation and the D* for black body were evaluated. Compared with bolometer made of high-Tc superconductor which functions at liquid nitrogen, and with pyroelectric detector, it was found that the advantages of this new device are that the device can work at room temperature with very low noise and very fast response. Although having a lower D* value than that of bolometer for the present device construction, we point out the possibility and the direction for improving the D* value, hence the promising prospect of this kind of device. 相似文献
157.
皮秒扫描相机在半导体激光管输出特性研究中的应用 总被引:1,自引:1,他引:0
本工作用Picotron 200型扫描相机和液态氮冷却的CCD摄相机系统对半导体激光二极管LTO22 MC的输出特性进行了测量,其最短输出脉冲宽度为2.1ps。这种半导体激光二极管的发射波长为780nm,连续工作条件下,其输出功率为3mW到5mW。 相似文献
158.
LIBAOLING G.F.DOMANTARY 《数学研究》1994,27(1):89-91
The V^t-integral as defined in[2], which is eqnivalent to M^2-integrsl as defined in Trigonometre series by Zygmund is used to sum trigonometric seies in[1]. In this paper, some convergent theorems of V^2-integral are established. 相似文献
159.
We present a Schrodinger (Liouville) type of equation for a quantum open system.It has a correlated part,and various master equations may be its special cases.It also has significant applications for constructing decoherencefree subspace for quantum computation.It is related to the original Schrodinger (Liouville)equation for the total system through a non-unitary similarity transformation.It is unnecessary for its correlated part to be self-adjoint,so there is a complex spectrum for the corresponding Hamiltonian (Liouvillian),which enables the time evolution of states to be asymmetric.This shows just the correlation to produce evolution of world. 相似文献
160.
This paper tries to introduce the reader to the method of using photochemical re-action to copy holographic optical elements(HOEs)in relief.The holographic blazing gratingso copied is groove depth adjustable phase modulability enlarged through copying and 3.3times the diffraction efficiency(DE)of the original grating.It is expected that the newmethod will lead to the mass production of the light-weight HOEs at low cost. 相似文献