全文获取类型
收费全文 | 9041篇 |
免费 | 398篇 |
国内免费 | 289篇 |
专业分类
化学 | 5326篇 |
晶体学 | 51篇 |
力学 | 244篇 |
综合类 | 18篇 |
数学 | 1958篇 |
物理学 | 2131篇 |
出版年
2022年 | 63篇 |
2021年 | 97篇 |
2020年 | 138篇 |
2019年 | 126篇 |
2018年 | 227篇 |
2017年 | 214篇 |
2016年 | 340篇 |
2015年 | 261篇 |
2014年 | 349篇 |
2013年 | 703篇 |
2012年 | 461篇 |
2011年 | 586篇 |
2010年 | 356篇 |
2009年 | 326篇 |
2008年 | 471篇 |
2007年 | 446篇 |
2006年 | 438篇 |
2005年 | 321篇 |
2004年 | 288篇 |
2003年 | 235篇 |
2002年 | 270篇 |
2001年 | 222篇 |
2000年 | 169篇 |
1999年 | 128篇 |
1998年 | 112篇 |
1997年 | 83篇 |
1996年 | 79篇 |
1995年 | 74篇 |
1994年 | 61篇 |
1993年 | 70篇 |
1992年 | 82篇 |
1991年 | 74篇 |
1990年 | 70篇 |
1989年 | 67篇 |
1988年 | 70篇 |
1987年 | 65篇 |
1986年 | 62篇 |
1985年 | 83篇 |
1984年 | 83篇 |
1983年 | 84篇 |
1982年 | 78篇 |
1981年 | 58篇 |
1980年 | 77篇 |
1979年 | 68篇 |
1978年 | 97篇 |
1977年 | 71篇 |
1976年 | 84篇 |
1975年 | 67篇 |
1974年 | 72篇 |
1973年 | 55篇 |
排序方式: 共有9728条查询结果,搜索用时 187 毫秒
951.
A generalized phase-shifting algorithm is implemented in the electron-wave interferometry with a transmission electron microscope, based on simultaneous measurement of the initial phases of the interferograms. The initial phase of each interferogram that has inherent linear carrier fringes is calculated using the Fourier co-efiicients of the interferogram itself corresponding to the carrier-frequency. Taking advantage of this phase-shifting method in both spatial resolution and precision, the phase distribution of a biological weak phase object is successfully measured. This promises to be one of the most spectacular application fields for this new technology. 相似文献
952.
953.
Maximal operator semigroups, bounded in a certain sense, on real or complex vector spaces are studied. For any maximal semigroup
\MM dominated by a certain pair of homogeneous functions there is an operator quasinorm for which \MM is exactly the semigroup of contractions in this quasinorm. Applications to Riesz spaces are given. In particular, maximal
semigroups of matrices dominated by a given positive matrix are characterized. We thus answer the question implicitly posed
in [2].
November 20, 1998 相似文献
954.
We observed circular white-light dark spatial solitons in photovoltaic self-defocusing LiNbO3:Fe crystal using an ordinary incandescent lamp as light source (a line source) with the filament of the bulb parallel to the crystalline c axis. Besides the above condition, the formation of the elliptic soliton needs an additive condition that the crystalline c axis is parallel to the minor axis of dark elliptic spot. 相似文献
955.
Simple Explicit Formulas for the Frame-Stewart Numbers 总被引:1,自引:0,他引:1
Several different approaches to the multi-peg Tower of Hanoi problem are equivalent. One of them is Stewart's recursive formula ¶¶ S (n, p) = min {2S (n1, p) + S (n-n1, p-1) | n1, n-n1 ? \mathbbZ+}. S (n, p) = min \{2S (n_1, p) + S (n-n_1, p-1)\mid n_1, n-n_1 \in \mathbb{Z}^+\}. ¶¶In the present paper we significantly simplify the explicit calculation of the Frame-Stewart's numbers S(n, p) and give a short proof of the domain theorem that describes the set of all pairs (n, n1), such that the above minima are achieved at n1. 相似文献
956.
Jia Zhen YANG* Ru Bo ZHANG Institute of Rare Scattered Element Chemistry Liaoning University Shenyang 《中国化学快报》2002,13(5)
This paper reports the EMF(electromotive force) measurements of cell (A) without liquid junction at five temperatures from 278.15 to 318.15 K. Pt|H2(101.325kPa)|HCl(m1),GaCl3(m2),H2O|Ag|AgCl (A) The measurements on the system HCl+GaCl3+H2O was carried out in an appropriate concentration of hydrochloric acid when the concentration of hydrochloric acid is not lower than 0.13 mol/kg the hydrolysis of Ga3+ can be avoided or elimited1. The standard association constant, KAS ,… 相似文献
957.
Predrag M. Rajković Sladjana D. Marinković Miomir S. Stanković 《The Ramanujan Journal》2006,12(2):245-255
We construct the sequence of orthogonal polynomials with respect to an inner product which is defined by q-integrals over a collection of intervals in the complex plane. We prove that they are connected with little q-Jacobi polynomials. For such polynomials we discuss a few representations, a recurrence relation, a difference equation,
a Rodrigues-type formula and a generating function.
2000 Mathematics Subject Classification Primary—33D45, 42C05 相似文献
958.
Schnelzer L Waldmann O Horvatić M Ochsenbein ST Krämer S Berthier C Güdel HU Pilawa B 《Physical review letters》2007,99(8):087201
The 1H NMR spectrum and nuclear relaxation rate T(1)(-1) in the antiferromagnetic wheel CsFe8 were measured to characterize the previously observed magnetic field-induced low-temperature phase around the level crossing at 8 T. The data show that the phase is characterized by a huge staggered transverse polarization of the electronic Fe spins, and the opening of a gap, providing microscopic evidence for the interpretation of the phase as a field-induced magnetoelastic instability. 相似文献
959.
960.
We experimentally investigate the interaction of counterpropagating discrete solitons in a one-dimensional waveguide array in photorefractive lithium niobate. While for low input powers only weak interaction and formation of counterpropagating vector solitons are observed, for higher input powers a growing instability results in discrete lateral shifting of the formed discrete solitons. Numerical modeling shows the existence of three different regimes: stable propagation of vector solitons at low power, instability for intermediate power levels leading to discrete shifting of the two discrete solitons, and an irregular temporal dynamic behavior of the two beams for high input power. 相似文献