全文获取类型
收费全文 | 8396篇 |
免费 | 623篇 |
国内免费 | 1351篇 |
专业分类
化学 | 2860篇 |
晶体学 | 35篇 |
力学 | 1055篇 |
综合类 | 70篇 |
数学 | 1567篇 |
物理学 | 1092篇 |
综合类 | 3691篇 |
出版年
2024年 | 36篇 |
2023年 | 109篇 |
2022年 | 172篇 |
2021年 | 220篇 |
2020年 | 267篇 |
2019年 | 248篇 |
2018年 | 219篇 |
2017年 | 254篇 |
2016年 | 343篇 |
2015年 | 307篇 |
2014年 | 402篇 |
2013年 | 631篇 |
2012年 | 499篇 |
2011年 | 548篇 |
2010年 | 442篇 |
2009年 | 508篇 |
2008年 | 454篇 |
2007年 | 583篇 |
2006年 | 499篇 |
2005年 | 505篇 |
2004年 | 483篇 |
2003年 | 387篇 |
2002年 | 360篇 |
2001年 | 293篇 |
2000年 | 237篇 |
1999年 | 225篇 |
1998年 | 165篇 |
1997年 | 126篇 |
1996年 | 116篇 |
1995年 | 137篇 |
1994年 | 101篇 |
1993年 | 99篇 |
1992年 | 84篇 |
1991年 | 59篇 |
1990年 | 53篇 |
1989年 | 39篇 |
1988年 | 37篇 |
1987年 | 28篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献
3.
Kai Cheng Xiao-Shuai Zhang Jie An Cheng Li Ruo-Yun Zhang Run Ye Prof. Dr. Bang-Jiao Ye Prof. Dr. Bo Liu Prof. Dr. Yuan-Di Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7553-7560
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA. 相似文献
4.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
5.
6.
为研究钢筋屈服强度和混凝土抗压强度对钢筋混凝土(RC)框架边节点剪切性能的影响规律,基于修正斜压场理论(MCFT),对某框架边节点的剪切应力-应变骨架曲线进行数值模拟,并与试验结果进行对比.在验证MCFT算法的精度后,研究钢筋屈服强度和混凝土抗压强度两个参数变化对RC框架边节点剪切应力-应变骨架曲线和峰值剪切应力的影响规律.结果表明:基于MCFT可以较好地模拟RC框架边节点的剪切应力-应变关系曲线; RC框架边节点的峰值剪切应力对混凝土抗压强度的变化更为敏感,但当试件的钢筋(HRB400)屈服应力下降幅度超过16.45%时,对钢筋屈服应力的变化更为敏感;当试件的钢筋(HRB400)屈服应力下降幅度超过10%时,节点发生钢筋滑移破坏,此时峰值剪切应力会大幅下降. 相似文献
7.
8.
This paper deals with the Cauchy–Dirichlet problem for the fractional Cahn–Hilliard equation. The main results consist of global (in time) existence of weak solutions, characterization of parabolic smoothing effects (implying under proper condition eventual boundedness of trajectories), and convergence of each solution to a (single) equilibrium. In particular, to prove the convergence result, a variant of the so-called ?ojasiewicz–Simon inequality is provided for the fractional Dirichlet Laplacian and (possibly) non-analytic (but ) nonlinearities. 相似文献
9.
10.
清明上河园游客行为及经营对策研究 总被引:1,自引:0,他引:1
主题公园必须有鲜明的主题,清明上河园突出宋文化,1998年开园以来取得了一定的效益,但还存在不少问题,针对清明上河园的经营现状,为了该园更好的发展,通过问卷调查的方式系统地了解了清明上河园的游客行为,在详细分析游客行为的基础上,对该园的经营提出了建设性对策。 相似文献