全文获取类型
收费全文 | 1163篇 |
免费 | 146篇 |
国内免费 | 139篇 |
专业分类
化学 | 440篇 |
晶体学 | 13篇 |
力学 | 562篇 |
综合类 | 5篇 |
数学 | 142篇 |
物理学 | 286篇 |
出版年
2023年 | 17篇 |
2022年 | 32篇 |
2021年 | 44篇 |
2020年 | 73篇 |
2019年 | 56篇 |
2018年 | 40篇 |
2017年 | 49篇 |
2016年 | 74篇 |
2015年 | 46篇 |
2014年 | 42篇 |
2013年 | 80篇 |
2012年 | 61篇 |
2011年 | 74篇 |
2010年 | 50篇 |
2009年 | 50篇 |
2008年 | 41篇 |
2007年 | 52篇 |
2006年 | 61篇 |
2005年 | 52篇 |
2004年 | 41篇 |
2003年 | 56篇 |
2002年 | 56篇 |
2001年 | 45篇 |
2000年 | 30篇 |
1999年 | 36篇 |
1998年 | 34篇 |
1997年 | 23篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1957年 | 4篇 |
1936年 | 1篇 |
排序方式: 共有1448条查询结果,搜索用时 15 毫秒
91.
A Solution‐Processed Air‐Stable Perylene Diimide Derivative for N‐type Organic Thin Film Transistors
Heng‐Wen Ting Szu‐Ying Chen Tin‐Chun Huang Prof. Jeng‐Hua Wei Prof. Tri‐Rung Yew 《Chemphyschem》2011,12(4):871-877
For future all‐soluble organic thin film transistor (OTFT) applications, a new soluble n‐type air‐stable perylene diimide derivative semiconductor material with (trifluoromethyl)benzyl groups (TC–PDI–F) is synthesized. The film is formed by spin‐coating in air and optimized for OTFT fabrications. The transistor characteristics and air‐stability of the TC–PDI–F OTFTs is measured to investigate the feasibility of using solution‐processed TC–PDI–F for future OTFT applications. For all‐solution OTFT process applications, the transistor characteristics are demonstrated by using TC–PDI–F as an n‐type semiconductor material and liquid‐phase‐deposited SiO2 (LPD–SiO2) as a gate dielectric material. All processes (except material synthesis and electrode deposition) and electrical measurements are conducted in air. 相似文献
92.
The probability distribution function of n random elements subjected to the flexible boundary condition is derived. The probability density is a descending curve and converges to a delta function as n tends to infinity. The distribution of the minimum value is discussed in context of ordered statistics. 相似文献
93.
介绍了用自适应LMS滤波器离线辨识六面体单元柔性结构模型和逆模型的方法。文中论述了自适应滤波理论和自适应逆控制之间的关系,讨论了LMS算法,并以实验法测得的六面体单元柔性结构随机振动数据为基础对其模型和逆模型进行了辨识,为进一步开展该结构的自适应逆控制研究奠定了基础。 相似文献
94.
95.
静载荷作用下柔韧圆板的大幅度振动 总被引:2,自引:1,他引:2
本文首先给出了均布载荷作用下柔韧圆板的大幅度振动方程,按文中给出的时间模态假设导了该问题的非线性耦合的代数和微分特征方程组,利用修正迭代法求出了该方程组的近似解析解,得到了柔韧圆振动的幅频-载荷特征关系,讨论了静载荷对其振动性态的影响。 相似文献
96.
An extension of the Elastica theory is developed to study the large deflection of an elastic-perfectly plastic horizontal
cantilever beam subjected to a vertical concentrated force at its tip. The entire process is divided into four stages: I.elastic
in the whole cantilever; II.loading and developing of the plastic region; III.unloading in the plastic region; and IV.reverse
loading. Solutions for stages I and II are presented in a closed form. A combination of closed-form solution and numerical
integration is presented for stage III. Finally, stage IV is qualitatively studied. Computed results are given and compared
with those from small-deflection theory and from the Elastica theory. 相似文献
97.
在现代高速旋转机械中,不平衡引起的振动是机器性能降低甚至损坏的重要原因。对变速转子准稳态主动平衡系统,可按一定时间步长把变转速离散成有限个转动角速度。针对每个离散角速度,依据影响系数法,采用包含残余振动值和校正不平衡的广义线性二次型目标性能函数推导出控制律。通过每个离散转速下影响系数的估计和增益矩阵的计算,形成对应于各离散转速的增益表,从而实现变速转子准稳态主动平衡系统的增益调度控制。数值模拟验证了增益调度控制能很好地抑制不平衡振动。与传统的加权二乘法(WLS)相比,数值模拟显示,该法对校正不平衡的惩罚可提高系统的稳定性,也可增强控制的鲁棒性。 相似文献
98.
99.
Zilun Tang Jianyu Wu Xiaochun Liu Qiuping Su Xingshan Yin Zhiyi Huang Xiaofeng Lin Wenjing Lin Guobin Yi 《Particle & Particle Systems Characterization》2021,38(12):2100160
The fabrication of flexible surface-enhanced Raman scattering (SERS) substrates for sensitive detection on uneven or irregular surfaces is challenging. In this study, a flexible dual plasmonic SERS (FDPS) substrate rationally constructed using Au nanoparticle (AuNP) arrays/aligned Ag nanowires (AgNWs) and elastic polyurethane (PU) is demonstrated. It exhibits high sensitivity (detection limit of 10−8 m for melamine and 10−10 m for malachite green) and excellent reproducibility. The well-designed structure of AuNP arrays/aligned AgNWs fabricated using block copolymer self-assembly and oil–water–air interfacial self-assembly successfully enhances the electromagnetic field through plasmonic coupling. In addition, the FDPS substrate retains a high SERS sensitivity after exposure to air at room temperature for 30 days because of the high stability of AuNP arrays and antioxidation characteristic of the PU covered on the aligned AgNWs. Even after undergoing stretching, bending, and twisting for 100 cycles, the FDPS substrate maintains a stable SERS activity owing to the introduction of the elastic PU. This study demonstrates a potential application of SERS detection under practical conditions for irregular surfaces and may be helpful in the development of flexible sensors. 相似文献
100.
Caiyun Xiong Xiaolin Nie Yixue Peng Xun Zhou Yangtao Fan Hu Chen Yanhui Liu 《理论物理通讯》2021,73(7):75602
Knots are discovered in biophysical systems, such as DNA and proteins. Knotted portions in knotted DNA are significantly bent and their corresponding bending angles are comparable with or larger than the sharp bending angle resulting in flexible defects. The role of flexible defects in the interplay of supercoiling and knotting of circular DNA were predicted by a Monte Carlo simulation. In knotted DNA with a particular knot type, a flexible defect noticeably enhances the supercoiling of the knotted DNA and the decreasing excitation energy makes the knotted portion more compact. A reduction in twist rigidity and unwinding of flexible defects are incorporated into the numerical simulations, so that interplay of supercoiling and knotting of circular DNA is studied under torsional conditions. Increasing unwinding not only results in a wider linking number distribution, but also leads to a drift of the distribution to lower values. A flexible defect has obvious effects on knotting probability. The summation of equilibrium distribution probability for nontrivial knotted DNA with different contour length does not change with excitation energy monotonically and has a maximum at an intermediate value of excitation energy around 5 kBT. In the phase space of knot length and gyration radius of knotted DNA, knot length does not anticorrelate with its gyration radius, which is attributed to the flexible defect in the knotted portion, which leads to the release of bending energy and inhibited the competition between entropy and bending energy. 相似文献