全文获取类型
收费全文 | 6030篇 |
免费 | 2173篇 |
国内免费 | 1105篇 |
专业分类
化学 | 1776篇 |
晶体学 | 259篇 |
力学 | 1176篇 |
综合类 | 207篇 |
数学 | 259篇 |
物理学 | 5631篇 |
出版年
2024年 | 53篇 |
2023年 | 182篇 |
2022年 | 263篇 |
2021年 | 206篇 |
2020年 | 155篇 |
2019年 | 211篇 |
2018年 | 127篇 |
2017年 | 213篇 |
2016年 | 226篇 |
2015年 | 277篇 |
2014年 | 730篇 |
2013年 | 434篇 |
2012年 | 410篇 |
2011年 | 469篇 |
2010年 | 401篇 |
2009年 | 490篇 |
2008年 | 566篇 |
2007年 | 366篇 |
2006年 | 369篇 |
2005年 | 344篇 |
2004年 | 301篇 |
2003年 | 394篇 |
2002年 | 357篇 |
2001年 | 300篇 |
2000年 | 253篇 |
1999年 | 194篇 |
1998年 | 143篇 |
1997年 | 115篇 |
1996年 | 115篇 |
1995年 | 143篇 |
1994年 | 95篇 |
1993年 | 68篇 |
1992年 | 76篇 |
1991年 | 61篇 |
1990年 | 65篇 |
1989年 | 66篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1979年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有9308条查询结果,搜索用时 15 毫秒
991.
Thermal transport property of investigated by molecular Ge34 and d-Ge dynamics and the Slack's equation
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)
In this study, we evaluate the values of lattice thermal conductivity κL of type Ⅱ Ge clathrate (Ge34) and diamond phase Ge crystal (d-Ce) with the equilibrium molecular dynamics (EMD) method and the Slack's equation. The key parameters of the Slack's equation are derived from the thermodynamic properties obtained from the lattice dynamics (LD) calculations. The empirical Tersoff's potential is used in both EMD and LD simulations. The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values. The predictions of the Slack's equation are consistent with the EMD results above 250 K for both Ge34 and d-Ge. In a temperature range of 200-1000 K, the κL value of d-Ge is about several times larger than that of Ge34. 相似文献
992.
分析了空间超光谱成像仪前置光学系统的热光学特性。应用有限元方法建立了模拟前置光学系统的热弹性变形模型,并进行了热弹性分析计算;用Zernike多项式拟合分析结果,求得各镜子反射面在热变形后的面型误差和相对于初始理想位置的偏移;利用光学分析设计软件Code V计算得到光学系统的像面与焦面的偏离量,即离焦量,并用多项式拟合得到其随温度变化的规律。计算结果表明,前置光学系统的像面在温度改变时会偏离焦面,离焦量与温度近似地成线性关系,当温度升高时像面最大偏移量为107.4μm,温度降低时像面最大偏移量为106.9μm。该分析结果可作为指导超光谱成像仪改进热控措施,进行调焦补偿的理论参考。 相似文献
993.
Three-party quantum secret sharing of secure direct communication based on x-type entangled states
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)
Based on x-type entangled states and the two-step protocol [Deng F G, Long G L and Liu X S 2003 Phys. Rev. A 68 042317], a quantum secret sharing protocol of secure direct communication based on x-type entangled states |X00〉3214 is proposed. Using some interesting entanglement properties of this state, the agent entirety can directly obtain the secret message from the message sender only if they collaborate together. The security of the scheme is also discussed. 相似文献
994.
Interracial barrier is a key factor that determines the performances of heterojunctions. In this work, we study the effect of manganite film thickness on the effective interracial barrier for La0.67Sr0.33MnO3/Nb:SrTiO3 junctions, The barrier is extracted from the forward current-voltage characteristics. Our results demonstrate that the barrier decreases gradually from -0.85 eV to -0.60 eV when the film thickness decreases from 150 nm to 2 nm. The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect. 相似文献
995.
<正>Accurate measurement of the optical properties of biological tissue is very important for optical diagnosis and therapeutics.An artificial neural network(ANN)-based inverse reconstruction method is introduced to determine the optical properties of turbid media,which is based on the reflectance(R) and transmittance (T) of a thin sample measured by a double-integrating-spheres system.The accuracy and robustness of the method has been validated,and the results show that the root mean square errors(RMSEs) of the absorption coefficientμ_a and scattering coefficientμ'_s reconstruction are less than 0.01 cm~(-1) and 0.02 cm~(-1),respectively.The algorithm is not only very accurate in the case of a lower albedo(~0.33),but also very robust to the noise of R and T especially for theμ'_s reconstruction. 相似文献
996.
997.
We experimentally obtain the route from period doubling to chaos in an active optical fiber ring resonator (AOFRR) with optical injection. The results show that the AOFRR is sensitive to external optical injection and demonstrate various dynamic characteristics. Meanwhile, the change of the injection strength can cause the output of the AOFRR to become periodic or chaotic. It can be confirmed that all the dynamic characteristics of the system are due to the interaction of the semiconductor laser with the erbium-doped fiber amplifier (EDFA). 相似文献
998.
GaN是一种理想的紫外发光和探测材料,其光学特性参数是光学器件设计的重要依据。采用紫外反射与透射光谱相结合的方法对国产GaN外延层进行光学特性测量,利用反射率与折射率之间的关系和薄膜干涉效应,建立了GaN外延层厚度、表面反射率、光谱吸收系数的光谱测量公式。测量结果表明,GaN外延层在紫外波段存在三个吸收区,其中364nm以下波段为强吸收区,吸收系数接近10^5cm^-1,364~375nm为吸收过渡区,375nm以上波段为弱吸收区;GaN表面反射率在三个吸收区的变化不大,为0.2~0.25之间。 相似文献
999.
1000.
Erich Kasper 《光学与光电技术》2010,8(2):1-6
作为微电子材料,硅具备许多优良的电学特性.采用硅材料的器件集成度能够比其他材料高几个数量级。然而.硅是一种间接带隙材料,其光学跃迁过程会引入大量低能的声子造成跃迁几率很低.导致其光学特性(发射与吸收)远不如Ⅲ/Ⅴ族半导体材料。 相似文献