全文获取类型
收费全文 | 1087篇 |
免费 | 115篇 |
国内免费 | 93篇 |
专业分类
化学 | 437篇 |
晶体学 | 20篇 |
力学 | 57篇 |
综合类 | 4篇 |
数学 | 59篇 |
物理学 | 718篇 |
出版年
2024年 | 2篇 |
2023年 | 27篇 |
2022年 | 29篇 |
2021年 | 39篇 |
2020年 | 31篇 |
2019年 | 29篇 |
2018年 | 27篇 |
2017年 | 61篇 |
2016年 | 59篇 |
2015年 | 60篇 |
2014年 | 60篇 |
2013年 | 70篇 |
2012年 | 47篇 |
2011年 | 89篇 |
2010年 | 57篇 |
2009年 | 69篇 |
2008年 | 81篇 |
2007年 | 74篇 |
2006年 | 62篇 |
2005年 | 42篇 |
2004年 | 32篇 |
2003年 | 38篇 |
2002年 | 23篇 |
2001年 | 27篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 34篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1948年 | 1篇 |
排序方式: 共有1295条查询结果,搜索用时 15 毫秒
141.
BSO(硅酸铋)晶体除了具有热自聚焦效应外1,还具有电控自聚焦效应2,基于电控自聚焦效应,又进一步对高斯光束经BSO晶体自聚焦后的远场光斑中心处的光强与加在晶体通光方向上的电压和入射光功率的关系进行了理论和实验研究,提出一种新的电光调制方法。理论与实验相符,进一步验证了文献1、2的结论. 相似文献
142.
Wolfgang Meier Hans-Friedrich Eicke Michael Odenwald 《Colloids and surfaces. A, Physicochemical and engineering aspects》1996,110(3):287-292
The influence of ABA-triblock copolymers on the temperature-induced infinite droplet cluster formation in water/oil-microemulsions is studied. The effects of the different blocks of the polymer can be well separated. With the help of an Ehrenfest relation the coupling between the elastically-induced shift of the infinite cluster formation temperature Tc and the plateau modulus of the resulting microemulsion networks is described. 相似文献
143.
Arshak L. Vartanian Mkrtich A. Yeranosyan Albert A. Kirakosyan 《Physica E: Low-dimensional Systems and Nanostructures》2005,27(4):447-456
Using a variational technique, the effect of electron-longitudinal optical (LO) phonon interaction on the ground and the first few excited states of a hydrogenic impurity in a semiconductor quantum wire of rectangular cross section under an external electric field is studied theoretically for the impurity atom doped at various positions. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied uniform electric field and the position of the impurity. It is found that the presence of optical phonons changes significantly the values of the impurity binding energies of the system. Taking into account the electron–LO phonon interaction the 1s→2py and 1s→2pz transition energies are calculated as a function of applied electric field for different impurity positions. 相似文献
144.
Summary The excitation of metastable states in an atomic beam apparatus by means of electron collision is a widespread technique.
We have observed a large bistable behaviour in our apparatus designed to provide an intense and collimated beam of metastable
helium by excitation with orthogonally impinging electrons. This bistable behaviour largely affects the efficiency of the
apparatus and is therefore worth of being carefully investigated. The apparatus has an electrode configuration equivalent
to that of a tetrode valve with large intergrid distances. The bistability consists in a hysteresis cycle in the curve of
the anode currentvs. grid voltage. Experimental measurements, supported by a simple theoretical model and by numerical simulation, stress out
the crucial role played by space charge effects for the onset of bistability. A comparison with previous observation of this
phenomenon is given. Spontaneous current oscillations with various shapes have been recorded in one of the two curves of the
hysteresis cycle. 相似文献
145.
电场驱动的高分子凝胶 总被引:1,自引:0,他引:1
本文较系统地阐述了电场驱动的高分子水凝胶、有机凝胶的响应机理,并扼要介绍了此类凝胶应用的最新进展。 相似文献
146.
电弧-AES法测定金属硅中12个杂质元素 总被引:2,自引:0,他引:2
用直流电弧粉末法在氩气气氛中摄谱,消除硅带干扰,采用铍为内标,直接测定金属硅中12个杂质元素,此法较化学光谱法具有操作简便、快速,试剂耗量少;较化学法和分光光度法更加优越,能同时测定12个元素,更能反映金属硅的真实含量。 相似文献
147.
本文概述了瓦斯煤尘爆炸火焰光谱实验研究的重要性,我们在弱爆炸和探测器小视场角的条件下,利用自己研制的多波道仪,在一端开口的Φ200cm×2900cm大型管道里,得到了CH4、空气和煤尘的混合物在不同状态下,特征波长λ等于0.8875、1.000、1.505、2.801和4.346微米(μ)的绝对辐射强度及其有关的变化规律,对结果进行了分析讨论,并与国外实验结果进行了对比,根据测量λ=4.346μ绝对辐射强度和我们选择的黑体辐射模型,获得了爆炸火焰的温度,该项研究不仅在工业中具有重要意义,而且对燃烧和化学动力学的研究也具有参考价值。 相似文献
148.
This paper presents detailed numerical calculations of the dielectrophoretic force in traps designed for single-cell trapping. A trap with eight planar electrodes is studied for spherical and ellipsoidal particles using the boundary element method (BEM). Multipolar approximations of orders one to three are compared with the full Maxwell stress tensor (MST) calculation of the electrical force on spherical particles. Ellipsoidal particles are also studied, but in their case only the dipolar approximation is available for comparison with the MST solution. The results show that a small number of multipolar terms need to be considered in order to obtain accurate results for spheres, even in the proximity of the electrodes, and that the full MST calculation is only required in the study of non-spherical particles. 相似文献
149.
A. Hussain C.W. Ahn H.J. Lee I.W. Kim J.S. Lee S.J. Jeong S.K. Rout 《Current Applied Physics》2010,10(1):305-310
We have fabricated lead-free Bi0.5(Na0.75K0.25)0.5TiO3 (BNKT) ceramics by a conventional process (CP) and reactive templated grain growth (RTGG) methods. The effect of grain orientation on structure, dielectric, complex impedance and electrical properties was investigated. The phase formation and grain morphology of BNKT ceramics were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. High dielectric constant and low dielectric loss was observed for grain oriented (textured) BNKT ceramics. Complex impedance, temperature dependent ac and dc conductivity were performed to explore the conduction behavior of the prepared BNKT ceramics. 相似文献
150.
Zhi-Hai Zhang Kang-Xian GuoBin Chen Rui-Zhen WangMin-Wu Kang Shuai Shao 《Superlattices and Microstructures》2010
The optical absorption coefficients and the changes in the refractive index in GaAs/AlGaAs parabolic quantum dots(QDs) with applied electric and magnetic fields are studied in detail. Analytical expressions for the linear and nonlinear intersubband absorption coefficients and refractive index changes are obtained by using a compact density matrix approach and an iterative procedure. Finally, the calculated results show the incident optical intensity, the frequencies of the confined potential of the QDs and the applied electric and magnetic fields have a great influence on the optical absorption coefficients and refractive index changes in this system. 相似文献