全文获取类型
收费全文 | 178733篇 |
免费 | 17762篇 |
国内免费 | 10412篇 |
专业分类
化学 | 93008篇 |
晶体学 | 1924篇 |
力学 | 13039篇 |
综合类 | 533篇 |
数学 | 42765篇 |
物理学 | 55638篇 |
出版年
2024年 | 369篇 |
2023年 | 2133篇 |
2022年 | 3644篇 |
2021年 | 4052篇 |
2020年 | 4248篇 |
2019年 | 4138篇 |
2018年 | 13045篇 |
2017年 | 12645篇 |
2016年 | 10744篇 |
2015年 | 5716篇 |
2014年 | 6291篇 |
2013年 | 8062篇 |
2012年 | 12934篇 |
2011年 | 19590篇 |
2010年 | 11677篇 |
2009年 | 11785篇 |
2008年 | 12760篇 |
2007年 | 14285篇 |
2006年 | 5666篇 |
2005年 | 5839篇 |
2004年 | 4841篇 |
2003年 | 4530篇 |
2002年 | 3371篇 |
2001年 | 2211篇 |
2000年 | 2044篇 |
1999年 | 2219篇 |
1998年 | 2032篇 |
1997年 | 1856篇 |
1996年 | 2080篇 |
1995年 | 1614篇 |
1994年 | 1531篇 |
1993年 | 1257篇 |
1992年 | 1121篇 |
1991年 | 1045篇 |
1990年 | 840篇 |
1989年 | 621篇 |
1988年 | 522篇 |
1987年 | 439篇 |
1986年 | 431篇 |
1985年 | 364篇 |
1984年 | 283篇 |
1983年 | 190篇 |
1982年 | 183篇 |
1981年 | 144篇 |
1980年 | 122篇 |
1979年 | 88篇 |
1978年 | 68篇 |
1976年 | 52篇 |
1974年 | 56篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Elizabeth Wulcan 《Arkiv f?r Matematik》2007,45(1):157-178
With a given holomorphic section of a Hermitian vector bundle, one can associate a residue current by means of Cauchy–Fantappiè–Leray
type formulas. In this paper we define products of such residue currents. We prove that, in the case of a complete intersection,
the product of the residue currents of a tuple of sections coincides with the residue current of the direct sum of the sections. 相似文献
102.
Liang-gen Hu 《应用数学学报(英文版)》2007,23(2):281-288
In this paper,we will establish several strong convergence theorems for the approximation ofcommon fixed points of r-strictly asymptotically pseudocontractive mappings in uniformly convex Banachspaces using the modiied implicit iteration sequence with errors,and prove the necessary and sufficient conditionsfor the convergence of the sequence.Our results generalize,extend and improve the recent work,in thistopic. 相似文献
103.
Daniel Maerten 《Annals of Global Analysis and Geometry》2007,32(4):391-414
We prove a Penrose-like inequality for the mass of a large class of constant mean curvature (CMC) asymptotically flat n-dimensional spin manifolds which satisfy the dominant energy condition and have a future converging, or past converging compact
and connected boundary of non-positive mean curvature and of positive Yamabe invariant. We prove that for every n ≥ 3 the mass is bounded from below by an expression involving the norm of the linear momentum, the volume of the boundary,
dimensionless geometric constants and some normalized Sobolev ratio. 相似文献
104.
In cricket, a rain-affected pitch can make batting more difficult than normal. Several other conditions such as poor light or an initially lively pitch, may also result in difficulties for the batsmen. In this note, we refer to all of them as ‘sticky wickets’. On sticky wickets, lower order batsmen are often sent into ‘hold the fort’ until conditions improve. In this paper, a stochastic dynamic programming model is used to examine the appropriateness of this policy. The model suggests that the tactic is often optimal when the sticky wicket persists until the end of the day's play, but not often when the sticky wicket is transitory. In some circumstances, it is worthwhile, on a normal wicket near the end of the day, to send in a lower order batsman to hold the fort (a night watchman): when the wicket is sticky, this tactic is even more worthwhile. 相似文献
105.
106.
The universal condition for the formation of omnidirectional band gaps (OBG) in photonic crystal (PC) was derived with consideration
of permeability of the materials. And it was found that there are four kinds of PCs: one of them has no OBG, and one always
possesses OBG. For the other two kinds of PCs, there are OBG for only TM or TE waves respectively. Moreover, in all PCs, the
OBG can be broadened by decreasing the refractive index of the ambient medium or/and increasing the contrast between the wave
impedances of the component materials of the PC.
PACS 42.70.Qs; 71.20.Tx 相似文献
107.
Perovskite-type lithium fast ion conductors of Li3xLa0.67−xScyTi1−2yNbyO3 system were prepared by solid state reaction. X-Ray powder diffraction shows that perovskite solid solution form in the ranges
of x=0.10, y≤0.10. AC impedance measurements indicate that the bulk conductivities and the total conductivities are of the
order of 10−4 S·cm−1 and 10−5 S·cm−1 at 25 °C respectively. The compositions have low bulk activation energies of about 17 kJ/mol in the temperature ranges of
298 – 523 K and total activation energies of about 37 kJ/mol in the temperature ranges of 298 – 523 K. 相似文献
108.
Jie Xue Liang Chen Li Zhou Zhifeng Jia Yanping Wang Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2006,44(15):2050-2057
α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006 相似文献
109.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
110.