全文获取类型
收费全文 | 13601篇 |
免费 | 2449篇 |
国内免费 | 5280篇 |
专业分类
化学 | 10325篇 |
晶体学 | 631篇 |
力学 | 993篇 |
综合类 | 428篇 |
数学 | 2172篇 |
物理学 | 6781篇 |
出版年
2024年 | 25篇 |
2023年 | 124篇 |
2022年 | 439篇 |
2021年 | 456篇 |
2020年 | 436篇 |
2019年 | 462篇 |
2018年 | 400篇 |
2017年 | 623篇 |
2016年 | 440篇 |
2015年 | 622篇 |
2014年 | 817篇 |
2013年 | 1123篇 |
2012年 | 1080篇 |
2011年 | 1232篇 |
2010年 | 1258篇 |
2009年 | 1293篇 |
2008年 | 1393篇 |
2007年 | 1288篇 |
2006年 | 1275篇 |
2005年 | 1057篇 |
2004年 | 816篇 |
2003年 | 590篇 |
2002年 | 580篇 |
2001年 | 571篇 |
2000年 | 724篇 |
1999年 | 391篇 |
1998年 | 248篇 |
1997年 | 188篇 |
1996年 | 208篇 |
1995年 | 146篇 |
1994年 | 152篇 |
1993年 | 144篇 |
1992年 | 113篇 |
1991年 | 77篇 |
1990年 | 93篇 |
1989年 | 94篇 |
1988年 | 74篇 |
1987年 | 58篇 |
1986年 | 45篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1971年 | 5篇 |
1965年 | 11篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
The present paper deals with the long-time behavior of a class of nonautonomous retarded semilinear parabolic differential equations. When the time delays are small enough and the spectral gap conditions hold, the inertial manifolds of the nonautonomous retard parabolic equations are constructed by using the Lyapunov-Perron method. 相似文献
123.
孙福伟 《数学的实践与认识》2002,32(3):370-373
本文提出了位移和速度同时反馈的数学模型 .并给出了位移和速度反馈的实现方法 ,该方法用传统的差动变压器实现了位移和速度的同时反馈 相似文献
124.
Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. The cell shape effect was simulated by an ellipsoidal cell model but the comparison between theory and experiment was far from being satisfactory. Prompted by the discrepancy, we proposed the use of spectral representation to analyze more realistic cell models. We adopted a shell-spheroidal model to analyze the effects of the cell membrane. It is found that the dielectric property of the cell membrane has only a minor effect on the dispersion magnitude ratio and the characteristic frequency ratio. We further included the effect of rotation of dipole induced by an external electric field, and solved the dipole-rotation spheroidal model in the spectral representation.Good agreement between theory and experiment has been obtained. 相似文献
125.
126.
双电极对双脉冲激光器结构分析 总被引:1,自引:0,他引:1
本文对双电极对双脉冲激光器的谐振腔结构进行了分析,结果表明采用双非稳腔和增大反射镜的曲率半径可分别获得单纵模和基横模输出。为使输出能量稳定,则双电极对的间距有一最小值的限制。 相似文献
127.
介绍了一种新的配送中心(DC)选址模型,在该模型中考虑了一般库存和安全库存成本,同时把从供应商到DC的运输成本也结合进去综合考虑,运输成本是由固定成本加可变成本两部分组成,反映了运输规模经济. 相似文献
128.
Liang Ruixi Peng Jun Shen Jianhua 《Annals of Differential Equations》2006,22(4):502-510
The boundedness of the every solution and the asymptotic behavior of all solutions of the nonlinear neutral delay differential equation [x(t) - P(t)x(t - t)]' Q1 (t)f(x{t-σ1))-Q2(t)f(x(t -σ2))=0,t≥t0 are investigated, whereτ,σ1,σ2∈(0,∞), P∈C([t0,∞),R), and Q1,Q2∈C([t0,∞),R), f∈C(R,R). The sufficient conditions obtained improve the existing results in the literatures. 相似文献
129.
Topological Properties of Urban Public Traffic Networks in Chinese Top-Ten Biggest Cities 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate the topological characteristics of complex networks as exemplified by the urban public traffic network (UPTN) in Chinese top-ten biggest cities. It is found that the UPTNs have small world behaviour, by the examination of their topological parameters. The quantitative analysis of the transport efficiency of the UPTNs reveals their higher local efficiency El and lower global efficiency Eg, which coincide well with the status quo of those Chinese cities still at their developing stage. Furthermore, the topological properties of efficiency in the UPTNs are also examined, and the findings indicate that, on the one hand, the UPTNs show robustness to random attacks and frangibility to malicious attacks on a global scale; on the other hand, the interrelation between UPTN efficiency and network motifs deserves our attention. The motifs which interrelate the UPTN efficiency are always triangular-formed patterns, e.g. motifs ID 238, ID 174 and ID 102, etc. 相似文献
130.
In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions in the literature 相似文献