全文获取类型
收费全文 | 32371篇 |
免费 | 6580篇 |
国内免费 | 3089篇 |
专业分类
化学 | 18273篇 |
晶体学 | 596篇 |
力学 | 1038篇 |
综合类 | 268篇 |
数学 | 2379篇 |
物理学 | 19486篇 |
出版年
2024年 | 76篇 |
2023年 | 332篇 |
2022年 | 836篇 |
2021年 | 959篇 |
2020年 | 1065篇 |
2019年 | 1011篇 |
2018年 | 981篇 |
2017年 | 1119篇 |
2016年 | 1491篇 |
2015年 | 1354篇 |
2014年 | 1598篇 |
2013年 | 3159篇 |
2012年 | 1968篇 |
2011年 | 2093篇 |
2010年 | 1722篇 |
2009年 | 1830篇 |
2008年 | 2075篇 |
2007年 | 2056篇 |
2006年 | 1988篇 |
2005年 | 1743篇 |
2004年 | 1633篇 |
2003年 | 1469篇 |
2002年 | 1518篇 |
2001年 | 1061篇 |
2000年 | 1117篇 |
1999年 | 870篇 |
1998年 | 809篇 |
1997年 | 608篇 |
1996年 | 481篇 |
1995年 | 506篇 |
1994年 | 374篇 |
1993年 | 324篇 |
1992年 | 303篇 |
1991年 | 212篇 |
1990年 | 211篇 |
1989年 | 162篇 |
1988年 | 146篇 |
1987年 | 123篇 |
1986年 | 126篇 |
1985年 | 105篇 |
1984年 | 99篇 |
1983年 | 43篇 |
1982年 | 64篇 |
1981年 | 40篇 |
1980年 | 36篇 |
1979年 | 41篇 |
1978年 | 28篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
The finiteness is proved of the set of isomorphism classes of potentially abelian geometric Galois representations with a given set of data. This is a special case of the finiteness conjecture of Fontaine and Mazur. 相似文献
22.
We investigate the problem of teleportation of unitary operations by unidirectional control-state telepor-tation and propose a scheme called unidirectional quantum remote control. The scheme is based on the isomorphismbetween operation and state. It allows us to store a unitary operation in a control state, thereby teleportation of theunitary operation can be implemented by unidirectional teleportation of the control-state. We find that the probabilityof success for implementing an arbitrary unitary operation on arbitrary M-qubit state by unidirectional control-stateteleportation is 4-M, and 2M ebits and 4M cbits are consumed in each teleportation. 相似文献
23.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
24.
25.
Nobuaki Obata 《Acta Appl Math》1997,47(1):49-77
A general theory of operators on Boson Fock space is discussed in terms of the white noise distribution theory on Gaussian space (white noise calculus). An integral kernel operator is generalized from two aspects: (i) The use of an operator-valued distribution as an integral kernel leads us to the Fubini type theorem which allows an iterated integration in an integral kernel operator. As an application a white noise approach to quantum stochastic integrals is discussed and a quantum Hitsuda–Skorokhod integral is introduced. (ii) The use of pointwise derivatives of annihilation and creation operators assures the partial integration in an integral kernel operator. In particular, the particle flux density becomes a distribution with values in continuous operators on white noise functions and yields a representation of a Lie algebra of vector fields by means of such operators. 相似文献
26.
M. Hanson 《Chromatographia》1994,39(7-8):431-437
Summary Pressure/temperature variation in SFC was shown to influence selectivity towards steroids. Major changes were observed for polar column packings compared to non-polar packings and variation of the amount of modifier showed that this is valid over the whole investigated range. The effect is underlined by a fall in resolution in the low density range (low pressure/high temperature) for polar stationary phases and appears to be significantly larger than for non-polar phases. Major selectivity shifts induced by variation of the physical properties of the mobile phase are considered to be due to the greater effect of polar modifiers on the nature of polar stationary phases than on non-polar phases. 相似文献
27.
28.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
29.
The Schwinger representation of the SO(8) fermion pair algebra in terms ofd and quasispin vector (u, s, v) bosons is used in deriving a microscopic boson coherent state having both particle-hole and pair excitations. The coherent
state is the exact boson image of the HFB variational solution. We can study the shape phase transition and pairing behaviour
of the nuclear ground states using the coherent states. 相似文献
30.
采用Agilent 81910A光子全参量测试仪,首次实验研究了InP/In1-xGaxAs1-yPy-MQW(Multiple-Quantum-Well,MQW)材料与衬底间因应力而产生的M-Z型光调制器的PDL影响以及由此引起的由差分群时延(Differential Group Delay,DGD)表征的偏振模色散(Polarization Mode Dispersion,PMD).研究结果表明,半导体MQW光调制器的PDL与DGD是一致的.因此在半导体光器件的制作过程中,应尽可能地减小衬底与波导芯层之间的因残存应力的存在造成对光器件的高速性能的不利影响. 相似文献