全文获取类型
收费全文 | 1243篇 |
免费 | 104篇 |
国内免费 | 77篇 |
专业分类
化学 | 103篇 |
晶体学 | 3篇 |
力学 | 576篇 |
综合类 | 8篇 |
数学 | 454篇 |
物理学 | 280篇 |
出版年
2024年 | 2篇 |
2023年 | 17篇 |
2022年 | 23篇 |
2021年 | 22篇 |
2020年 | 41篇 |
2019年 | 31篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 54篇 |
2015年 | 37篇 |
2014年 | 80篇 |
2013年 | 119篇 |
2012年 | 60篇 |
2011年 | 73篇 |
2010年 | 40篇 |
2009年 | 75篇 |
2008年 | 72篇 |
2007年 | 77篇 |
2006年 | 87篇 |
2005年 | 71篇 |
2004年 | 46篇 |
2003年 | 53篇 |
2002年 | 52篇 |
2001年 | 29篇 |
2000年 | 38篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1424条查询结果,搜索用时 15 毫秒
71.
72.
Palladium nanoparticles/wool keratin-assisted carbon composite-modified flexible and disposable electrochemical solid-state pH sensor 下载免费PDF全文
张文立 刘笑天 林友辉 马利芸 孔令庆 闵光宗 吴荣辉 Sharwari K.Mengane 杨丽坤 Aniruddha B.Patil 刘向阳 《中国物理 B》2022,31(2):28201-028201
Several p H-dependent processes and reactions take place in the human body;hence,the p H of body fluids is the best indicator of disturbed health conditions.However,accurate and real-time diagnosis of the p H of body fluids is complicated because of limited commercially available p H sensors.Hence,we aimed to prepare a flexible,transparent,disposable,userfriendly,and economic strip-based solid-state p H sensor using palladium nanoparticles(Pd NPs)/N-doped carbon(NC)composite material.The Pd NPs/NC composite material was synthesized using wool keratin(WK)as a precursor.The insitu prepared Pd NPs played a key role in the controlled switching of protein structure to the N-doped carbon skeleton withπ–πarrangement at the mesoscale level,which mimics the A–B type polymeric structure,and hence,is highly susceptible to H+ions.The optimized carbonization condition in the presence of Pd NPs showed that the material obtained using a modified Ag/Ag Cl reference electrode had the highest p H sensitivity with excellent stability and durability.The optimized p H sensor showed high specificity and selectivity with a sensitivity of 55 m V/p H unit and a relative standard deviation of 0.79%.This study is the first to synthesize Pd NPs using WK as a stabilizing and reducing agent.The applicability of the sensor was investigated for biological samples,namely,saliva and gastric juices.The proposed protocol and material have implications in solid-state chemistry,where biological material will be the best choice for the synthesis of materials with anticipated performance. 相似文献
73.
74.
针对不同体积分布指数p的W/Cu连续功能梯度材料的偏滤器第一壁结构,采用有限元软件计算了 8MW•m−2稳态运行热加载以及等离子体破裂条件下1GW•m−2热流冲击下的力学响应。相同稳态加载条件下,W/Cu 连续功能梯度材料的最优分布指数与分层梯度材料存在较大差异,其最优等效应力比分层梯度材料要小26%,表现出更优异的性能。在热冲击响应过程中,连续梯度W/Cu材料塑性损伤随p值不同也存在较大变化,其最优p值与其稳态运行时热应力最优p值存在一定差异,从第一壁应用条件考虑,应综合选取,最佳p值在1.2附近。综合来看,连续梯度W/Cu材料具有更连续变化的热物理属性及力学性能,在聚变堆第一壁结构设计中具有更大的应用潜力。 相似文献
75.
76.
非均质、各向异性材料梯度多墙结构充分利用了材料性质连续、渐进、变化的物理力学性能,现已广泛应用于飞行机翼结构和汽车轻量化结构.在层合板屈曲理论的基础上,针对梯度多墙结构这一具体结构形式,采用当量刚度方法,建立了相应的本构关系和非线性屈曲控制方程,求解得到不同复杂边界条件及组合载荷下的屈曲临界载荷,通过试验分析验证,计算结果可以较好地满足工程设计.研究结果表明:梯度材料能有效地减小界面中的应力集中,减弱材料中初始缺陷的作用,从而不同程度地提高了材料的强度和韧性. 相似文献
77.
利用弹道冲击摆锤系统对分层梯度蜂窝夹芯板在爆炸荷载下的动力响应进行了实验研究,分析了梯度蜂窝夹芯板在爆炸荷载作用下的变形失效模式,并与传统非梯度蜂窝夹芯板的抗爆性能做了对比。通过一维应力波理论,分析了应力波在梯度芯层中的传播规律。应力波透射系数在梯度试件中比非梯度芯层中小,而且相对密度递减的芯层组合有最小的应力波透射系数。综合考虑结构变形失效模式,后面板挠度,芯层压缩量以及应力波传播特点得到:分层梯度蜂窝夹芯板的抗爆性能明显优于传统的非梯度夹芯板,在所研究的荷载范围内,芯层相对密度从大到小排列试件的抗爆性能相对较好。 相似文献
78.
A New Higher Order Shear Deformation Model for Static Behavior of Functionally Graded Plates 下载免费PDF全文
Tahar Hassaine Daouadji Abdelouahed Tounsi & El Abbes Adda Bedia 《advances in applied mathematics and mechanics.》2013,5(3):351-364
In this paper, a new displacement based high-order shear deformation theory is introduced
for the static response of functionally graded plate. Unlike any other theory, the number
of unknown functions involved is only four, as against five in case of other shear deformation
theories. The theory presented is variationally consistent, has strong similarity with
classical plate theory in many aspects, does not require shear correction factor, and
gives rise to transverse shear stress variation such that the transverse shear stresses
vary parabolically across the thickness satisfying shear stress free surface conditions.
The mechanical properties of the plate are assumed to vary continuously in the thickness
direction by a simple power-law distribution in terms of the volume fractions of the
constituents. Numerical illustrations concerned flexural behavior of FG plates with
Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume
fraction, volume fraction profiles, aspect ratios and length to thickness ratios. The
validity of the present theory is investigated by comparing some of the present results
with those of the classical, the first-order and the other higher-order theories. It
can be concluded that the proposed theory is accurate and simple in solving the static
behavior of functionally graded plates. 相似文献
79.
As to an ideally layered structure with a functionally graded piezoelectric substrate (material parameters change continuously along the thickness direction) and a hard dielectric layer, the existence and propagation behavior of transverse surface waves is studied by analytical technique. The dispersion equations for the existence of the transverse surface waves with respect to phase velocity are obtained for electrically open and short circuit conditions, respectively. A detailed investigation of the effect of gradient coefficient on dispersion relation, electromechanical coupling factor and penetration depth is carried out. It is found by numerical examples that adjusting gradient coefficient makes the electromechanical coupling factor of the transverse surface waves achieve quite high values at some appropriate ratio values of the layer thickness to the wavelength, and at the same time, the penetration depth can be reduced to the same order as the wavelength. 相似文献
80.