全文获取类型
收费全文 | 35492篇 |
免费 | 5565篇 |
国内免费 | 2916篇 |
专业分类
化学 | 12795篇 |
晶体学 | 209篇 |
力学 | 1612篇 |
综合类 | 602篇 |
数学 | 9527篇 |
物理学 | 19228篇 |
出版年
2024年 | 72篇 |
2023年 | 386篇 |
2022年 | 949篇 |
2021年 | 1072篇 |
2020年 | 987篇 |
2019年 | 925篇 |
2018年 | 877篇 |
2017年 | 1002篇 |
2016年 | 1218篇 |
2015年 | 1047篇 |
2014年 | 1607篇 |
2013年 | 2418篇 |
2012年 | 1780篇 |
2011年 | 2054篇 |
2010年 | 1824篇 |
2009年 | 2265篇 |
2008年 | 2490篇 |
2007年 | 2507篇 |
2006年 | 2304篇 |
2005年 | 1793篇 |
2004年 | 1598篇 |
2003年 | 1485篇 |
2002年 | 1450篇 |
2001年 | 1204篇 |
2000年 | 1129篇 |
1999年 | 939篇 |
1998年 | 891篇 |
1997年 | 629篇 |
1996年 | 499篇 |
1995年 | 438篇 |
1994年 | 364篇 |
1993年 | 345篇 |
1992年 | 433篇 |
1991年 | 257篇 |
1990年 | 223篇 |
1989年 | 208篇 |
1988年 | 168篇 |
1987年 | 159篇 |
1986年 | 125篇 |
1985年 | 136篇 |
1984年 | 135篇 |
1983年 | 77篇 |
1982年 | 151篇 |
1981年 | 211篇 |
1980年 | 211篇 |
1979年 | 228篇 |
1978年 | 202篇 |
1977年 | 131篇 |
1976年 | 129篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented
within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical
properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with
time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available. 相似文献
42.
43.
Maria Kordaki Athanasia Balomenou 《International Journal of Computers for Mathematical Learning》2006,11(1):99-135
This study focuses on the constructions in terms of area and perimeter in equivalent triangles developed by students aged 12–15 years-old, using the tools provided by Cabri-Geometry II [Labore (1990). Cabri-Geometry (software), Université de Grenoble]. Twenty-five students participated in a learning experiment where they were asked to construct: (a) pairs of equivalent triangles “in as many ways as possible” and to study their area and their perimeter using any of the tools provided and (b) “any possible sequence of modifications of an original triangle into other equivalent ones”. As regards the concept of area and in contrast to a paper and pencil environment, Cabri provided students with different and potential opportunities in terms of: (a) means of construction, (b) control, (c) variety of representations and (d) linking representations, by exploiting its capability for continuous modifications. By exploiting these opportunities in the context of the given open tasks, students were helped by the tools provided to develop a broader view of the concept of area than the typical view they would construct in a typical paper and pencil environment. 相似文献
44.
We present a new approach to study the convergence of Newton's method in Banach spaces, which relax the conditions appearing in the usual studies. The approach is based on the bound required for the second derivative of the operator involved. An application to a nonlinear integral equation is presented. 相似文献
45.
The theory of free-carrier absorption (FCA) is developed, in the extreme quantum limit when the carriers are assumed to populate
only the lowest quantized energy level, for quasi-two and one-dimensional semiconducting quantum well structures where the
carriers are scattered by ionized impurities. The radiation field is assumed to be polarized in the plane of the layer in
the quasi-two-dimensional case and along the length of the wire in the quasi-one-dimensional case. Expressions for FCA are
obtained for the cases where the impurities are either in the well (background impurities) or outside the well (remote impurities).
Variation of FCA is numerically studied with photon frequency and well width. 相似文献
46.
相对论性无自旋粒子在Hartmann势场中运动的精确解 总被引:1,自引:1,他引:0
在标量势等于矢量势的条件下,本文获得了具有Hartmann型势的Klein-Gordon方程的精确解.给出了束缚态的精确的能谱方程和归一化的径向波函数,对于散射态,获得了按“k/2π标度”归一化的径向波函数和相移的解析计算公式.讨论了散射振幅的解析性质和波函数、能谱方程以及相移的非相对论近似. 相似文献
47.
浅析二阶齐次线性变系数微分方程的一个可积类型 总被引:1,自引:0,他引:1
姬志飞 《应用数学与计算数学学报》2006,20(1):125-128
本文讨论了二阶齐次线性变系数微分方程的特殊形式,给出了这种微分方程的一个可积类型. 相似文献
48.
We inquire into the time evolution of quantum systems associated with pseudo-or quasi-Hermitian Hamiltonians. We obtain, in
the pseudo-Hermitian case, a generalized Liouville-von Neumann equation for closed systems. We show that quantum systems with
quasi-Hermitian Hamiltonians admit the proper interpretation in terms of open quantum system and derive a generalized Lindblad-Kossakowski
equation. Finally, we extend such formalism to the study of decaying systems.
Partially supported by PRIN “Sintesi”. 相似文献
49.
We present a general scheme for entangling any degree of freedom of two uncorrelated identical particles from independent
sources by a combination of two-particle interferometry and which-way detection. We show that this entanglement generation
procedure works for completely random initial states of the variable to be entangled. We also demonstrate a curious complementarity
exhibited by our scheme and its applications in estimating the generated entanglement as a function of wave packet overlap
at the beamsplitter. 相似文献
50.