全文获取类型
收费全文 | 34347篇 |
免费 | 6410篇 |
国内免费 | 4510篇 |
专业分类
化学 | 12985篇 |
晶体学 | 286篇 |
力学 | 2110篇 |
综合类 | 263篇 |
数学 | 8565篇 |
物理学 | 21058篇 |
出版年
2024年 | 114篇 |
2023年 | 445篇 |
2022年 | 765篇 |
2021年 | 1143篇 |
2020年 | 1236篇 |
2019年 | 1129篇 |
2018年 | 1109篇 |
2017年 | 1205篇 |
2016年 | 1518篇 |
2015年 | 1351篇 |
2014年 | 1919篇 |
2013年 | 3087篇 |
2012年 | 2075篇 |
2011年 | 2419篇 |
2010年 | 1906篇 |
2009年 | 2285篇 |
2008年 | 2503篇 |
2007年 | 2489篇 |
2006年 | 2183篇 |
2005年 | 1872篇 |
2004年 | 1552篇 |
2003年 | 1481篇 |
2002年 | 1385篇 |
2001年 | 1071篇 |
2000年 | 1130篇 |
1999年 | 876篇 |
1998年 | 840篇 |
1997年 | 614篇 |
1996年 | 413篇 |
1995年 | 373篇 |
1994年 | 315篇 |
1993年 | 278篇 |
1992年 | 243篇 |
1991年 | 197篇 |
1990年 | 201篇 |
1989年 | 193篇 |
1988年 | 163篇 |
1987年 | 147篇 |
1986年 | 125篇 |
1985年 | 133篇 |
1984年 | 114篇 |
1983年 | 41篇 |
1982年 | 84篇 |
1981年 | 75篇 |
1980年 | 59篇 |
1979年 | 68篇 |
1978年 | 60篇 |
1977年 | 70篇 |
1976年 | 63篇 |
1973年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
采用密度泛函方法(B3P86)对 Fe_2分子结构进行了优化.计算结果中未观察到自旋污染,基态波函数与高态波函数并未混杂,结果表明,Fe_2中有8个未配对电子,这些电子空间分布不同和自旋平行产生的自旋极化效应,使 Fe_2能量最低.计算结果表明,Fe_2分子的基态是~9∑_g~ ,并非~7Δ_u,进而表明 Fe_2的自旋平行效应比电子自旋配对效应要强.计算得到该分子基态的二阶、三阶和四阶力常数分别为1.4115×10~(-2)aJ/nm~2、-37.1751×10~3aJ/nm~3和 98.7596×10~4aJ/nm~4;光谱数据ω_eχ_e、B_e、α_e分别为0.3522、0.0345、 0.4963×10~(-4)cm~(-1);离解能为3.5522eV,平衡键长为0.2137nm,振动频率为292.914cm~(-1);并得到了 Murrel-Sorbie 函数. 相似文献
52.
53.
54.
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
55.
根据Pegg-Barnett位相定义, 计算了一种新的奇偶非线性相干态的位相概率分布函数, 利用数值计算方法研究了它们的位相统计性质. 数值计算结果表明:新的奇偶非线性相干态的位相特性与通常奇偶相干态的位相特性截然不同. 相似文献
56.
57.
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
58.
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
59.
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
60.
DING Bin-Gang ZHANG Da-Li LU Ding-Hui 《理论物理通讯》2006,46(1):113-118
We calculate the binding energies of Ni, Cu, Xe, Cs, Pt, Au, Np, Pu isotope chains using two interaction parameter sets NL-3 and NL-Z, and compared the relative errors of the even-even nuclei with those of odd-even nuclei and odd-odd nuclei. We find that the errors of binding energy of odd-even and odd-odd nuclei are not bigger than the one of even-even nuclei. The result shows that comparing with even-even nuclei, there is no systematic error and approximation in the calculations of the binding energy of odd-even and odd-odd nuclei with relativistic mean-field theory. In addition, the result is explained theoretically. 相似文献