全文获取类型
收费全文 | 1714篇 |
免费 | 63篇 |
国内免费 | 26篇 |
专业分类
化学 | 1075篇 |
晶体学 | 7篇 |
力学 | 62篇 |
数学 | 259篇 |
物理学 | 400篇 |
出版年
2023年 | 14篇 |
2022年 | 26篇 |
2021年 | 25篇 |
2020年 | 45篇 |
2019年 | 30篇 |
2018年 | 22篇 |
2017年 | 15篇 |
2016年 | 36篇 |
2015年 | 29篇 |
2014年 | 47篇 |
2013年 | 72篇 |
2012年 | 115篇 |
2011年 | 118篇 |
2010年 | 69篇 |
2009年 | 60篇 |
2008年 | 118篇 |
2007年 | 78篇 |
2006年 | 91篇 |
2005年 | 96篇 |
2004年 | 71篇 |
2003年 | 60篇 |
2002年 | 60篇 |
2001年 | 43篇 |
2000年 | 40篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 9篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1994年 | 24篇 |
1993年 | 26篇 |
1992年 | 19篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 19篇 |
1976年 | 12篇 |
1974年 | 12篇 |
1973年 | 11篇 |
排序方式: 共有1803条查询结果,搜索用时 31 毫秒
111.
112.
N. T. Tung T. X. Hoai V. D. Lam J. W. Park V. T. Thuy Y. P. Lee 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(1):47-51
Matching the impedance of a medium to free space, which is usually not available in natural materials, is an important advance
in metamaterials. In this paper, we present a simple mechanism for a perfect impedance-matched left-handed metamaterials,
that reveals a nearly zero reflection over operating frequency. This finding is based on the independent manipulation of the
electric response without any effect on the magnetic one. 相似文献
113.
Baoyong Zhang James Lam Shengyuan Xu Zhan Shu 《Nonlinear Analysis: Real World Applications》2010,11(3):1963-1976
This paper is concerned with the problem of absolute exponential stability analysis for a class of continuous-time systems with sector-bounded nonlinearities and interval time-varying delays. Absolute exponential stability criteria, which depend not only on the delay range but also on the decay rate, are derived by using a novel Lyapunov functional. These criteria are expressed in the form of linear matrix inequalities (LMIs) and they can easily be checked. By solving these LMIs, estimates of the exponential decay rate and decay coefficient are obtained. A numerical example is provided to demonstrate the effectiveness of the proposed method. 相似文献
114.
We develop a microscopic pedestrian-simulation model in which pedestrian positions are updated at discrete time steps. At each time step, each pedestrian probabilistically selects a direction of movement from a predetermined set according to a logit-type function that considers the dynamics of other pedestrians around, and then selects a step size that satisfies a certain distribution. We perform a number of field experiments on real intersecting pedestrian flows with four different angles. We then validate and calibrate the model using sample data on the deviation angles, step velocities, and velocity–density relations obtained from the experiments. 相似文献
115.
We expand the picture of plasmon hybridization in metamagnetic structure via numerically studying the electromagnetic coupling in the metallic cut-wire-pair super cells. It is shown that a triple negative permeability band can be achieved by systematically controlling the plasmon hybridization in such the structure. The corresponding transmission properties as well as the electromagnetic responses of the plasmon-hybridized structures were presented by using the finite integration technique simulations. Our results would reveal a promising design to obtain the multiple negative refractions based on the combination of hybridized cut-wire-pairs and continuous wires. 相似文献
116.
This article describes the roadside traffic noise surveys conducted in heavily built-up urban areas in Hong Kong. Noise measurements were carried out along 18 major roads in 1999. The measurement data included L10, L50, L90, Leq, Lmax, the number of light vehicles, the number of heavy vehicles, the total traffic flow, and the average speed of vehicles. Statistical analysis using the analysis of variance (ANOVA) and Tukey test (p<0.05) reveals that the total traffic flow and the number of heavy vehicles are the most significant factors of urban traffic noise. Multiple regression was used to derive a set of empirical formulas for predicting L10 noise level due to road traffic. The accuracy of these empirical formulas is quantified and compared to that of another widely used prediction model in Hong Kong--the Calculation of Road Traffic Noise. The applicability of the selected multiple regression model is validated by the noise measurements performed in the winter of 2000. 相似文献
117.
Jetti RK Thallapally PK Nangia A Lam CK Mak TC 《Chemical communications (Cambridge, England)》2002,(9):952-953
The title molecule forms a honeycomb network of molecular and nitro-trimer synthons with guest species included in the hexagonal voids. 相似文献
118.
119.
120.
Let P be a lattice polytope in R
n
, and let P \cap Z
n
= {v
1
,\ldots,v
N
} . If the N + N\choose 2 points 2v
1
,\ldots, 2v
N
;v
1
+v
2
,\ldots, v
N-1
+ v
N
are distinct, we say that P is a ``distinct pair-sum' or ``dps' polytope. We show that if P is a dps polytope in R
n
, then N≤ 2
n
, and, for every n , we construct dps polytopes in R
n
which contain 2
n
lattice points. We also discuss the relation between dps polytopes and the study of sums of squares of real polynomials.
Received November 10, 2000, and in revised form June 28, 2001. Online publication November 2, 2001. 相似文献