全文获取类型
收费全文 | 5718篇 |
免费 | 904篇 |
国内免费 | 751篇 |
专业分类
化学 | 451篇 |
晶体学 | 37篇 |
力学 | 472篇 |
综合类 | 168篇 |
数学 | 4306篇 |
物理学 | 1939篇 |
出版年
2024年 | 14篇 |
2023年 | 71篇 |
2022年 | 76篇 |
2021年 | 120篇 |
2020年 | 189篇 |
2019年 | 167篇 |
2018年 | 184篇 |
2017年 | 210篇 |
2016年 | 268篇 |
2015年 | 181篇 |
2014年 | 315篇 |
2013年 | 404篇 |
2012年 | 320篇 |
2011年 | 357篇 |
2010年 | 296篇 |
2009年 | 349篇 |
2008年 | 451篇 |
2007年 | 349篇 |
2006年 | 336篇 |
2005年 | 346篇 |
2004年 | 286篇 |
2003年 | 324篇 |
2002年 | 275篇 |
2001年 | 222篇 |
2000年 | 228篇 |
1999年 | 168篇 |
1998年 | 153篇 |
1997年 | 157篇 |
1996年 | 99篇 |
1995年 | 88篇 |
1994年 | 58篇 |
1993年 | 43篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 23篇 |
1989年 | 30篇 |
1988年 | 13篇 |
1987年 | 24篇 |
1986年 | 9篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1971年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有7373条查询结果,搜索用时 476 毫秒
11.
令Ω1与Ω2与C^n中的两个有界齐性域,假设φ:1Ω→Ω2是一个全纯映射。在本中,我们研究相应的复合算子Cφ:β(Ω2)→β(Ω1)的有界性和紧性,特别地,我们讨论取B^n和U^n的情形。 相似文献
12.
在不同激光脉宽下的高次谐波 总被引:3,自引:2,他引:1
用数值计算方法计算了不同强激光脉冲宽度下高次谐波的产生.我们发现对于激光场强度不高,不能有效电离初态的激光场,长脉冲宽度可以更有效产生高次谐波;而对于高场强的激光场,由于它能够在几个光学周期之内把原子的初态全部电离,所以短脉冲的激光场能够更有效产生高次谐波. 相似文献
13.
We consider some Sobolev-type spaces and obtain a necessary and sufficient condition for their embedding in a Lebesgue space. 相似文献
14.
Given a principal value convolution on the Heisenberg group Hn = Cn×R, we study the relation between its Laguerre expansion and the Fourier-Bessel expansion of its limit on Cn. We also calculate the Dirichlet kernel for the Laguerre expansion on the group Hn. 相似文献
15.
Let
d−1{(x1,…,xd)
d:x21+···+x2d=1} be the unit sphere of the d-dimensional Euclidean space
d. For r>0, we denote by Brp (1p∞) the class of functions f on
d−1 representable in the formwhere dσ(y) denotes the usual Lebesgue measure on
d−1,
and Pλk(t) is the ultraspherical polynomial.For 1p,q∞, the Kolmogorov N-width of Brp in Lq(
d−1) is given bythe left-most infimum being taken over all N-dimensional subspaces XN of Lq(
d−1).The main result in this paper is that for r2(d−1)2,where ANBN means that there exists a positive constant C, independent of N, such that C−1ANBNCAN.This extends the well-known Kashin theorem on the asymptotic order of the Kolmogorov widths of the Sobolev class of the periodic functions. 相似文献
16.
《Surface and interface analysis : SIA》2003,35(2):146-150
We report the first application of pump–probe second harmonic generation (SHG) measurements to characterize optically induced magnetization in non‐magnetic multilayer semiconductors. In the experiment, spin‐polarized electrons are excited selectively by a pump beam in the GaAs layer of GaAs/GaSb/InAs structures. However, the resulting net magnetization manifests itself through the induced SHG probe signal from the GaSb/InAs interface, thus indicating a spin‐polarized electron transport across the heterostructure. We find that the magnetization dynamics are governed by an interplay between the spin density evolution at the interfaces and the spin relaxation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
Andrey Pereverzev 《Foundations of Physics Letters》2003,16(5):411-428
We argue that it may be possible to consistently explain the quantum measurement by assuming that the wave function is in one-to-one correspondence with objective physical reality and has no probabilistic interpretation. In the context of such approach we consider the model of a harmonic oscillator linearly coupled to a heat bath and treat the oscillator as the system being measured. Three classes of initial pure states for the bath are considered. Exact expressions for the average values and variances of the oscillator coordinate and momentum as functions of time are considered for each class of pure states. It is shown that these quantities exhibit different asymptotic behavior for different classes of initial states of the bath. In particular, if each mode of the bath is initially in a coherent state, then for an arbitrary initial state of the oscillator the variances of the oscillator coordinate and momentum asymptotically approach the same values as for a coherent state of the free oscillator, while the averages of coordinate and momentum show a Brownian-like behavior. We argue that such behavior shows several features of the quantum measurement and supports our interpretation of the wave function. 相似文献
18.
Lova Zakariasy 《Proceedings of the American Mathematical Society》2003,131(4):1177-1180
We show that on the harmonic Bergman spaces, the Hankel operators with nonconstant harmonic symbol cannot be of finite rank.
19.
林正炎 《数学物理学报(B辑英文版)》2003,23(3)
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions. 相似文献
20.
Chin-Tsang Chiang Mei-Cheng Wang 《Annals of the Institute of Statistical Mathematics》2004,56(1):87-100
This paper proposes kernel estimation of the occurrence rate function for recurrent event data with informative censoring.
An informative censoring model is considered with assumptions made on the joint distribution of the recurrent event process
and the censoring time without modeling the censoring distribution. Under the validity of the informative censoring model,
we also show that an estimator based on the assumption of independent censoring becomes inappropriate and is generally asymptotically
biased. To investigate the asymptotic properties of the proposed estimator, the explicit form of its asymptotic mean squared
risk and the asymptotic normality are derived. Meanwhile, the empirical consistent smoothing estimator for the variance function
of the estimator is suggested. The performance of the estimators are also studied through Monte Carlo simulations. An epidemiological
example of intravenous drug user data is used to show the influence of informative censoring in the estimation of the occurrence
rate functions for inpatient cares over time. 相似文献