全文获取类型
收费全文 | 12610篇 |
免费 | 1034篇 |
国内免费 | 702篇 |
专业分类
化学 | 8446篇 |
晶体学 | 121篇 |
力学 | 499篇 |
综合类 | 51篇 |
数学 | 1487篇 |
物理学 | 3742篇 |
出版年
2023年 | 159篇 |
2022年 | 293篇 |
2021年 | 292篇 |
2020年 | 308篇 |
2019年 | 327篇 |
2018年 | 253篇 |
2017年 | 265篇 |
2016年 | 404篇 |
2015年 | 415篇 |
2014年 | 485篇 |
2013年 | 723篇 |
2012年 | 899篇 |
2011年 | 1025篇 |
2010年 | 651篇 |
2009年 | 676篇 |
2008年 | 769篇 |
2007年 | 734篇 |
2006年 | 647篇 |
2005年 | 561篇 |
2004年 | 532篇 |
2003年 | 455篇 |
2002年 | 406篇 |
2001年 | 330篇 |
2000年 | 271篇 |
1999年 | 207篇 |
1998年 | 163篇 |
1997年 | 139篇 |
1996年 | 175篇 |
1995年 | 132篇 |
1994年 | 150篇 |
1993年 | 124篇 |
1992年 | 117篇 |
1991年 | 96篇 |
1990年 | 106篇 |
1989年 | 82篇 |
1988年 | 90篇 |
1987年 | 61篇 |
1986年 | 69篇 |
1985年 | 95篇 |
1984年 | 69篇 |
1983年 | 68篇 |
1982年 | 49篇 |
1981年 | 46篇 |
1980年 | 47篇 |
1979年 | 34篇 |
1977年 | 37篇 |
1976年 | 37篇 |
1975年 | 34篇 |
1974年 | 48篇 |
1973年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A modified Lorentz theory (MLT) based on the generalized Galilean transformation has recently received attention. In the framework of MLT, some explicit formulas dealing with the one-way velocity of light, slow-clock transport and the Doppler effect are derived in this paper. Several typical experiments are analyzed on this basis. The results show that the empirical equivalence between MLT and special relativity is still maintained to second order terms. We confirm recent findings of other works that predict the MLT might be distinguished from special relativity at the third order by Doppler centrifuge experiments capable of a fractional frequency detection threshold of 10–15. 相似文献
132.
本文描述了一种应用于自由电子激光结合高里德堡态氢原子飞行时间谱装置中的分光方法,以及该方法应用于小分子(如2S)光解动力学研究中的必要性. 拉曼-α辐射(121.6 nm),用作H原子产物探测的激光,是在Kr/Ar气介质中利用四波混频产生的. 利用透镜对不同波长的光有不同的折射率,四波混频后的混合光在经过一片离轴的氟化锂透镜后,121.6 nm的激光将会与212.6和845 nm在空间上分开. 在激光到达反应中心前利用挡板挡住212.6和845 nm的激光,只让121.6 nm的光经过反应中心,从而消除212.6 nm激光产生的背景信号对实验的干扰. 结合自由电子激光,成功地研究了H2S在122.95 nm波长下的光解动力学,采集到了产物时间飞行谱. 本文展示了转换得到的产物总平动能谱,解离机理与121.6 nm波长下的结果相似. 实验结果显示,该方法成功地解决了分子在VUV波段进行光解动力学研究的难题,消除了这些分子在紫外光波段因为强烈吸收而产生的背景信号. 相似文献
133.
134.
This load supporting prefabricated wall consists of a thin plate reinforced along its boundaries by a frame. With the loads acting on the frame, the plate has its boundary conditions defined neither by forces nor by displacements. On the basis of satisfying the biharmonic equation of the stress function for the plate, we make the total strain energy to be minimum to ensure the compatibility of displacements for the two elastic bodies. Thus we get a set of infinite simultaneous equations. The results obtained indicate the method of solution is effective. 相似文献
135.
This work is a continuation of the discussion of [1], On a class of method for solving problems with random boundary notches and/or cracks, (I) by C. Ouyang (Appl. Math. & Mech., vol. 1, No. 2, 1980). Here computations for boundary notches are made by using the theory and formulas presented in [1]. In the computation modification is also made for the boundary conditions in parametric plane in [1]. Numerical results for examples show that within ranges of parameter considered in the paper, for example L, the present method in quite workable in practical computations. 相似文献
136.
137.
Resonance fluorescence spectra of gaseous chlorine, excited with a high power single longitudinal mode argon ion laser which was tuned through the lasing profiles of the 4880-, 4965-, 5017-, and 5145-Å lines, were studied. Five progressions of fluorescence lines were found and assigned as the fluorescence of 35Cl35Cl and 37Cl37Cl isotopic molecules resonantly excited from v = 0 and 1 levels of the X1Σ state to the B3Π state. The fluorescence line positions agreed with those of the theoretical calculation within 0.2 cm?1. The fluorescence intensities were very weak due to the extremely small transition probability between the B3Π and the X1Σ states. 相似文献
138.
A new acousto-optic diffraction configuration is described. At a liquid-solid interface, a light beam is incident from the solid side of higher refractive index. The maximum acousto-optic diffraction of the Raman-Nath type occurs in the liquid with light incident at the critical angle. The angular dependence of the diffraction efficiency indicates accurate optical alignment requirement. Application to acoustic imaging is briefly discussed. 相似文献
139.
R.T.V. Kung C.H. Chang 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(7):579-586
The neutral Bremsstrahlung cross-sections of Ne, Ar and atomic oxygen around the 3 and 10μ wavelength regions were measured in a high temperature plasma generated in a shock tube. The results were generally a factor of three higher than the theoretical values calculated by Geltman. Agreement with the experimental results of Taylor and Caledonia around 3μ was good except for the case of Ne. The cross-sections around 10μ are the first measurements in this wavelength region. Enhanced radiation due to atomic line emission on top of the Bremsstrahlung continuum, as predicted by Hyman was observed around 7.44μ. 相似文献
140.